Therapeutic potential of adipose tissue in aesthetic medicine

Abstract

Aesthetic medicine is a branch of medicine dedicated to improve an individual’s appearance and overall visual appeal. Conventional aesthetic treatments have limitations, including the risk of complications, allergic reactions, and temporary benefits. Adipose tissue offers a promising alternative to conventional aesthetic treatments. The regenerative properties, accessibility and versatility of adipose tissue make it an attractive option for individuals seeking natural and long-lasting aesthetic results. Adipose tissue is rich source of adipose tissue derived stem cells (ASCs), growth factors and extracellular matrix. It can restore and rejuvenate the damaged and aged tissues. Adipose tissue can be used in different formats such as pure adipose tissue grafts, stromal vascular fraction, nanofat, macrofat, microfat and as a pure population of ASCs. In addition, ASC derived exosomes offer a unique cell-free therapy advantages bioactive molecules like growth factors, cytokines, and microRNAs to stimulate collagen production, improve skin texture, and address pigmentation issues. This review highlights the multifaceted potential of adipose tissue in aesthetic medicine. It discusses its diverse applications, the biological mechanisms involved, and emerging therapeutic approaches. Moreover, this review also highlights the challenges and future direction of using adipose tissue-based therapies for aesthetic treatments.

Key Words: Aesthetic medicine; Adipose tissue; Autologous fat grafting; Regenerative aesthetics; Nanofat

Core Tip: Aesthetic medicine has evolved with innovative solutions for improvement of overall appearance. Adipose tissue, with its regenerative properties, offers a promising alternative to traditional treatments. Adipose tissue derivatives such as nanofat, microfat, adipose tissue-derived stem cells, and stromal vascular fraction have shown therapeutic applications in aesthetic medicine. Studies demonstrate their effectiveness in treating acne scars, burn wounds, hyperpigmentation, wrinkles, and skin rejuvenation. However, limitations such as graft survival variability and regulatory challenges need to be addressed. Further research is necessary to fully harness the potential of adipose tissue in aesthetic medicine.

INTRODUCTION

Aesthetic medicine is a dynamic and interdisciplinary field dedicated to enhance the physical appearance of an individual and promote overall well-being. It offers innovative solutions for improvement of skin (particularly of face) to make the body attractive and beautiful[1]. It uses various non-invasive or minimally invasive techniques to provide the beauty, which someone idealizes. Conventional aesthetic treatments such as derma fillers, botox, chemical peel, laser treatment, and microdermabrasion can enhance appearance. However, they may have several drawbacks such as allergic reactions, infections, granuloma formation, ischemia, and risks related to anesthesia[2]. Adipose tissue is a potential alternative to traditional treatments due to its wide versatility, accessibility and regenerative properties[3].

Adipose tissue, also known as fat, is a loose connective tissue, composed mostly of adipocytes. It also contains cells such as fibroblasts, stem cells, preadipocytes, vascular endothelial cells and a variety of immune cells. Fat is distributed throughout the body; in bone marrow (giving it a yellowish appearance), in subcutaneous regions (beneath the skin), intra-articular, (within the joints) and visceral region (around internal organs). Human possess three different kinds of adipose tissues: Brown adipose tissue, white adipose tissue (WAT), and beige (brown/white) adipose tissue. Brown adipose tissue is abundantly present in newborns but its proportion decreases in adults. It generates heat and play important role in survival of newborns[4]. WAT is most abundant form of adipose tissue. It provides insulation to body, is a source of numerous hormones, serve as cushion for organs and act as energy storage organ during starvation or intense activity. It stores energy in the form of triglycerides (fat). When required, lipase breaks adipose tissue to release the stored energy through lipolysis. Beige adipose tissue exhibit properties of both brown and WAT[5]. WAT is widely employed in the applications of regenerative medicine. WAT and its derivatives can serve multiple roles beyond energy storage, including its therapeutic applications in asthetic medicine.

Adipose tissue can be used in different forms in aesthetic medicine applications. Most common forms of adipose tissue for aesthetic medicine are nanofat, microfat, macrofat, SVF, adipose tissue derived stem cells (ASCs), and pure adipose tissue graft. ASCs are known for their regenerative properties. They have high proliferative potential and the ability to differentiate into various cell types[6]. ASCs secrete paracrine signals that promote angiogenesis, proliferation, wound healing, migration, and extracellular matrix (ECM) production[7]. During burn wound healing, ASCs demonstrate increased production of collagen type 2 and reduction of scar tissues. ASC-supplemented nanofat has demonstrated significant improvement in scar depth, volume and is being widely used to treat acne scars[8]. SVF is used to treat melanocytosis due to their collagen production and anti-inflammatory properties[9]. Adipose tissue grafts have also exhibited a significant improvement in the treatment of hyperpigmentation that occur due to excessive production of melanin pigment from melanocytes[10]. Adipose tissues can be used in the form of nanofat to treat fine lines, and wrinkles, thus improving physical appearance[11]. While it has promising results in aesthetic medicine, the use of adipose tissue may have some limitations, such as such as graft survival variability, formation of fat cyst, regulatory, and ethical challenges that hinder its widespread and effective use. This review highlights the use of adipose tissue and its regenerative products for aesthetic medicine. It also explores the biological mechanism related to regenerative potential of adipose tissue, the approaches to use adipose tissue in aesthetic medicine and its applications in various aesthetic and reconstructive procedures. The review also discusses the challenges associated with the use of adipose tissue and future directions to improve its use for aesthetic treatments.

OVERVIEW OF AESTHETIC MEDICINE

Aesthetic medicine is a branch of medicine that enhances physical appearance of an individual by improving skin health, facial features, and body shape. It is a multidisciplinary field and overlaps with several other fields such as aesthetic surgery, plastic surgery, dermatology, and anti-aging medicine[12]. The most distinguishing feature of aesthetic medicine is the use of non-invasive or minimally invasive techniques to alter the appearance while ensuring safety. Physical appearance has an important role in developing confidence, self-esteem, and happiness[13]. Aesthetic medicine has its roots back in ancient civilizations, where aesthetic procedures were performed to contour physical appearance of the body, as preventive care to slow aging, and treating skin conditions[14]. Table 1 shows the timeline of aesthetic medicine from ancient civilizations to modern advancements.

Table 1 Timeline of aesthetic medicine.

Category	Description	Key developments	Timeline
Ancient civilizations	Aesthetic procedures for contouring, preventive care, and skin conditions	Egyptian medicine, Greek and Roman medical systems	Ancient times
Modern aesthetic medicine	Breakthroughs in surgical techniques and chemical peels	Johann F. Dieffenbach, William Tilbury Fox, Paul G. Unna	19th century
Chemical peels	First chemical peel performed by Dr. William Tilbury Fox	Phenol-based peels for skin rejuvenation	1871
Facial reconstruction	Johann F. Dieffenbach's work on facial reconstruction	Rhinoplasty, cleft lip and palate repair	1845
Paraffin injections	Robert Gersuny's use of paraffin injections	Augmentation for facial and body contouring	1899
Laser technology	Development of first laser technique	Ruby laser for tattoo removal	1960
Plastic surgery	Development of plastic surgery centers in Germany, Britain, and Europe	Advancements in reconstructive and aesthetic procedures	20th century
Silicone fillers	Use of silicone as fillers	Long-lasting effect and natural feel	Mid-20th century
Botox	Botulinum toxin type A for facial wrinkles and fine lines	Muscle relaxation for wrinkle reduction	Late 20th century
Derma fillers	Hyaluronic acid-based fillers for skin rejuvenation and volume restoration	Safety and reversibility
Laser treatments	Different wavelengths for unwanted hairs, acne, pigmentation, and scars	Cornerstone of aesthetic medicine
Adipose tissue-derived therapies	Natural and biocompatible alternative to conventional aesthetic treatments	Tissue regeneration, collagen production, angiogenesis	21st century

Ancient Egyptians treated hair and skin disorders. Ancient Greeks and Romans incorporated their understanding of herbal remedies, oils, and therapeutic techniques into their own medical system, which laid the groundwork for European medicine[15]. Modern aesthetic medicine began with a breakthrough in surgical techniques and chemical peels in 19^th century. In 1845, Johann F. Differbach used the term rhinoplasty for the first time for nasal reconstructive surgery. He documented his findings regarding facial reconstruction. In 1871, Dr. William Tilbury Fox performed the first chemical peel by using 20% phenol. The technique was then further refined by Paul G. Unna in 1882[16]. In 1899 Robert Gersuny's used paraffin injection for augmentation purposes, but the patients later developed granulomas. Therefore, its use in aesthetic treatments was stopped. In 20^th century, the two world wars played a central role in the development of the field of plastic surgery[17]. These wars witnessed horrific injuries on face and limbs of soldiers which no one has witnessed before. This lead to the development of plastic surgery centers in Germany, Britian, and Europe[18]. In mid 20^th century, the use of silicon as filler became popular due to its long-lasting effect and natural feel. However, it caused serious complications like infection, granuloma formation, migration, and fibrosis[19]. In 1960, a significant advancement was made in aesthetic medicine with the development of first laser technique to remove tattoos, also know as ruby laser[20].

The emphasis of ancient Egyptians and Greeks on the natural remedies has influenced the modern shift towards minimally invasive, holistic approaches in aesthetic medicine. In 21^st century, aesthetic medicine has evolved to offer broader range of treatments. Patients are increasingly opting for non-surgical face rejuvenation, injectables, and laser treatment as minimally invasive procedures that provide natural-looking outcomes with fewer side effects. Currently, a wide variety of services is being offered including botox, derma fillers, laser, and body contouring. Botox (botulinum toxin type A) is a neurotoxic protein that can stop the release of the neurotransmitter acetylcholine at the neuromuscular junction. This makes muscles to relax. In aesthetic medicine, it is being used to treat facial wrinkles and fine lines[21]. Derma fillers are used for skin rejuvenation, volume restoration, and to improve overall facial aesthetics by enhancing facial features. There are multiple types of derma fillers, such as calcium hydroxylapatite fillers, hyaluronic acid-based fillers, and poly-L-lactic acid fillers. Hyaluronic acid based fillers are commonly employed due to their safety and reversibility[22]. Laser have become the corner stone of aesthetic medicine and being used to address multiple issues like unwanted hairs, acne, pigmentation, and scars by using different wavelengths[23]. These conventional aesthetic procedures have limitations. For example, fillers may cause the development of granulomas and ischemia, adverse skin reactions by laser treatments, serious allergic reactions of the use of bovine collagen, and minor side effects like bruising and edema[24]. Additionally, there is a lack of standardized and evidence-based practices, which complicates the use of above-mentioned techniques and chemicals. These procedures fail to fully restore the natural look of skin and underlying tissues. A more natural and biocompatible alternative to these conventional aesthetic treatments is the use of adipose tissue and its derivatives. The use of adipose tissue is a safer option as compared to conventional therapies. Adipose tissue is readily available from patient own body, which eliminates the need for synthetic or external substances. The applications of adipose tissue also avoid allergic reactions, granulomas, immune rejection, and foreign body responses, which make it a biocompatible option for regenerative and aesthetic treatments. Overall, adipose tissue is preferred over conventional aesthetic approaches due to its natural ability to promote tissue regeneration, collagen production, angiogenesis, biocompatibility, being natural and autologous and provision of long-term effects.

ADIPOSE TISSUE: A VERSATILE SOURCE FOR AESTHETIC SURGERY

The term "adipose tissue" refers to a particular type of connective tissue that is found in abundance throughout the human body. It is also known as fat tissue, fatty tissue, and fat. Adipose tissue is commonly found under the skin, in the lining of internal organs, interstitial spaces between muscles, breast tissue, and bone marrow. Adipose tissue is now considered as an active tissue that primarily function as a fat storage site but also serve as an endocrine organ. It produces several bioactive substances like adipokines and cytokines [e.g., leptin, adiponectin, tumor necrosis factor-alpha (TNF-α), and interleukin (IL)-6], which play crucial roles in metabolism, inflammation, and tissue regeneration[25]. Adipose tissue depots contain a wide variety of cell types, including mature adipocytes, ASCs, fibroblasts, vascular smooth muscle cells, haematopoietic cells, pericytes, endothelial cells, erythrocytes, and various immune cells (B and T-lymphocytes, macrophages, myeloid cells). These cells communicate to control the activity and function of adipose tissue depots[26].

There are three types of adipose tissue: Brown, white, and beige. The morphology and function of brown and WATs are different[5]. Brown fat is found in newborn babies. It is usually found on the back, between the shoulders, along the upper spine, and around the kidneys of babies. The quantity of brown adipose tissue decreases gradually as it endures a morphologic transformation with advanced age. Adults have some brown adipose tissue deposits around their vertebrae, in the middle section of the thoracic cavity, and in the upper back, above the clavicles[27]. WAT is the predominant fat type in the body. The majority of its distribution occurs in subcutaneous or intra-abdominal depots. It is also found around the heart and pericardium. The majority of cells of WATs are adipocytes, or monocular fat cells. These cells contain just one massive lipid droplet and lack most cellular organelles. WAT is primarily responsible for storing energy and producing adipokines[28]. Beige (brown/white) adipose tissue, the third type of adipose tissue, stores energy. It exhibits properties of both brown and WAT. However, it is more similar to WAT. Typically, WAT is found in pockets with beige adipocytes. Beige adipocytes can secrete heat when stimulated by cold or particular nerve adrenergic receptors[29]. Among all types of adipose tissues, WAT is abundantly utilized in healthcare applications including aesthetic medicine. Because it contains the highest concentration of adult stem cells (i.e. ASCs), subcutaneous adipose tissue is a popular choice for cell-based therapies in cosmetic, reconstructive, and plastic surgery treatments[5].

Adipose tissue can be processed to obtain various forms prior to its use in patients. The products of adipose tissue processing include microvascular fragments (MVFs), ASCs, fat grafts (macrofat, microfat, nanofat), and stromal vascular fractions (SVF). Autologous adipose tissue grafting is considered as the optimal treatment option for a variety of conditions due to its ability to provide tissue material that is identical to the patient's own. Furthermore, it eliminates issues related to allogenic materials. Fat grafting is a viable option for treating a range of medical conditions due to its unique properties. Macrofat, microfat, and nanofat are the three varieties of fat that are utilized in fat grafting[5]. Macrofat is structurally larger and is applied without further breaking it into smaller fragments. It is obtained with cannulas of diameter 3 mm or above. There is no additional processing required for the application of macrofat[30]. Macrofat grafting is also known as traditional fat grafting. It can restore lost or damaged soft tissue from aging, disease, trauma, or other causes. It can also correct structural abnormalities. The term "microfat" indicates smaller fat particles (lobules) that are approximately 500 mm in size. Microfat contains smaller particles as compared to macrofat. It is possible to inject microfat into a sensitive area of the body without worrying about the lumpiness that can occur with larger fat particles. Nanofat is an emulsified form of adipose tissue. Nanofat contains large number of stem cells and other progenitors. Therefore, it has been widely used for tissue repair and regeneration. Nanofat grafting is applied in delicate body parts especially the face. Nanofat can repair and remodel tissues in a variety of dermatological condition, including pigmentation, scars, wrinkles, small joints, and particular ligament-tendon targets. Thus, nanofat is thought of as a possible adipose tissue product in the field of regenerative medicine. Additional byproducts of adipose tissue processing include millifat, millimicrofat, SVF, and MVFs. The SVF obtained by enzymatic digestion of adipose tissue is a rich resource for the rapid treatment of a wide range of medical conditions. Cells in SVF can repair damaged tissues and organs by using paracrine and trans differentiation processes. Obtaining SVF is far easier and takes considerably less time than obtaining pure population of ASCs. ASC isolation required further culturing of SVF in in vitro cultures. Furthermore, heterogeneous cell composition of SVF provides therapeutic advantages in a variety of medical applications[5]. The use of SVF and the three main forms of fat grafts (macrofat, microfat, and nanofat) has been widespread in cosmetic, aesthetic, and reconstructive surgeries for regenerative medicine purposes. Figure 1 shows an overview of adipose tissue isolation and processing for aesthetic applications.

Figure 1 A schematic representation of adipose tissue isolation and processing for aesthetic applications. The process involves harvesting, excision, and washing, followed by enzymatic and non-enzymatic isolation and processing methods to obtain various end products. These products are used in aesthetic treatments such as skin rejuvenation, precise injection of stem cells, and facial volumization.

ADIPOSE TISSUE HARVESTING

Adipose tissue is mostly collected from abdominal region of body using minimally invasive methods. The survival of fat grafts and the transplanted cells is dependent on the technique used to harvest the adipose tissue. There have been several proposed methods for fat harvesting. Nevertheless, the best one, considering both convenience of use and cell survival, remains up for debate. The ideal fat-harvesting process would increase the number of healthy cells. The two most common methods to remove fat from the body are liposuction and direct surgical excision.

Liposuction

Liposuction is a less invasive and widely used technique for adipose tissue extraction. It is used for both aesthetic and reconstructive surgery. This procedure is often carried out using suction-assisted liposuction or hand-held syringe aspiration. The suction-assisted liposuction technique removes fat more quickly than the syringe aspiration approach. Larger quantities of fat can be aspirated with this method. Using a suction pump, this method generates a negative pressure. Large syringes are used to collect adipose tissue during suction-assisted liposuction. The use of liquid-jet, ultrasonic pulses, or laser energy to improve the results of liposuction is a relatively new development[31].

Syringe aspiration is the process of harvesting and collecting adipose tissue in a syringe by applying negative pressure. A cannula is attached to a syringe using a valve system. The volume of syringe is typically 10 to 50 milliliters. The plunger is withdrawn to generate a negative pressure within the hypodermic layer after the valve is closed. Aspirating the adipose tissue requires inserting the cannula under the skin and opening the valve. Various orientations of the syringe-connected cannula are applied. The negative pressure will eventually cause the adipose tissue to begin entering the syringe. Once the desired quantity of adipose tissue is obtained in the syringe, the process is repeated using new syringe. Syringes containing fat can be sealed and sent to a processing laboratory in a sterile environment. Syringe liposuction is commonly used when only a little amount of fat tissue is required. The ability to freely adjust the cannula during the procedure is the primary benefit of syringe aspiration, which makes it easier, faster, and more efficient. The surgeon can also exactly control the amount of fat that is extracted during the procedure using this method[5,32].

Excision method

The harvesting of adipose tissue through excision method involves the surgical removal of fat tissue. Multiple larger incisions are necessary to access the tissue through direct excision. In direct fat excision, adipocytes encounter less damage and exhibit higher survival rates, ultimately enhancing graft survival.

This method has certain advantages and disadvantages over lipoaspiration technique. Its advantages includes preservation of structural integrity[33], prevention of cellular damage[34], and higher yield of stem cells[35]. It yields high quality fat tissue but it is more invasive, require processing of adipose tissue though mincing or enzymatic digestion, longer recovery time, and patient complication like infection can also occur. Both methods have their own benefits and limitations, so the selection of a particular method depends upon the required outcomes.

ISOLATION OF ADIPOSE TISSUES DERIVED STEM CELLS

The isolation method of Adipose-Derived Stem Cells (ADSCs) from adipose tissue includes enzymatic and non-enzymatic methods. Enzymatic methods are commonly used for SVF preparation and subsequently stem cells isolation. The initial step in enzymatic method involves the minimally invasive retrieval of an adequate quantity of subcutaneous adipose tissue from the patient. The task is achieved using appropriately sized cannulas connected to a 20cc or 50cc syringe. Typically, 3-5-mm cannulas featuring sharp side holes are employed for this procedure. The abdomen is the most common site for liposuction in SVF preparation. However, surgeons may also choose thigh or buttock regions in many cases. After aspiration, the fat tissue is transferred to the lab in a sterile container. The syringes are subsequently sprayed with 70% ethanol and transferred to a biosafety cabinet for further processing. Fat is subsequently transferred to 50 mL centrifuge tubes to facilitate the removal of debris and blood. An equal volume of PBS is added to the tubes, followed by vigorous shaking to facilitate the separation of clumped tissue fragments. The tubes are left upright for a suitable amount of time so that the various phases can separate. Adipose tissue floats at the top layer due to its relatively lower density, whereas debris with blood clots sinks to the bottom. The infranatant is extracted using sterile disposable pipettes and subsequently discarded. The procedure mentioned earlier is repeated 3 to 5 times or until the tissue is completely washed. Following adequate cleaning of the adipose tissue, collagenase enzyme (2–3 mg/mL) is mixed with the washed adipose tissue for enzymatic breakdown. The tubes are shaken and kept in an incubator set at 37 °C for 30 minutes. Collagenase breaks the collagen fibres in the ECM of adipose tissue while physical movement enhance the release of the cells. After half-hour incubation, the contents of the tube are separated into two phases: The lower aqueous fraction contains the cells of interest, while the upper floating layer contains the debris, undigested fat, oils and mature adipocyte fraction. A 70 mm cell strainer is used to remove larger cell clumps and debris particles from the infranatant after it has been collected from the tubes. The cell suspension is centrifuged at 300 relative centrifugal force for 10 minutes at 4 °C to collect the cells as pellet. This pellet contains a mixture of cells and is referred to as SVF. The supernatant is carefully disposed of from the tubes without disruption of the cell pellet at the bottom of the tube. The pellet is resuspended in an appropriate volume of liquid, such as saline, and subsequently transferred to a syringe for further applications[5,36,37].

Mechanical emulsification, sonication, and vortexing are non-enzymatic methods for adipose tissue disintegration. The non-enzymatic approach involves employing mechanical grinders to process adipose tissue, followed by the application of various-sized filters to isolate the necessary cells. Ortho kit (Lipogems International SpA, Milan, Italy), Rigenera^® (Human Brain Wave HBW, Turin, Italy), Lipogems^® ortho kit (Lipogems International SpA, Milan, Italy) have also been developed for mechanical isolation of cells from adipose tissue. Mechanical methods have no effect on cell survival and viability, despite the fact that enzymatic methods are still considered the gold standard. However, due to the strong collagen bonds that bind adipose tissue cells together, mechanical methods alone are unable to significantly increase cellular output compared to enzymatic methods[5,36,37].

APPLICATIONS OF ADIPOSE TISSUE IN AESTHETIC MEDICINE

Adipose tissue contains a large number of cells including the stem cells. It is a readily available source of cells for numerous regenerative medicine applications. Advancements in understanding adipose tissue biology have sparked increasing interest in its potential therapeutic uses, especially within aesthetic medicine. The use of adipose tissue to treat contour deformities, pigmentation, and rhinoplasty is a renowned practice in aesthetic medicine and reconstructive surgery.

Rhinoplasty

Rhinoplasty is a very popular facial reconstruction procedure that can alter the shape of nose. It employs autologous fat grafting (AFG) to improve the appearance of nose as well as quality of nasal skin[38]. In surgical AFG, soft tissue augmentation is used to enhance facial aesthetics, volume restoration, and lipofilling[5]. Adipose tissue has the ability to release IL-13 and TGF-β thereby enhancing restorative results[39]. IL-13 is an important immunomodulatory cytokine that helps to maintain nasal structure after surgery by promoting graft stability and reducing cartilage degradation. TGF-β, a multifunctional cytokine, regulates cellular development, differentiation, and immune function. It contributes significantly to tissue repair, remodeling, and ECM maintenance. During grafting, TGF-β facilitates graft stability by promoting collagen synthesis, reducing inflammation, and facilitating cellular adhesion. This provides structural support and benefits for achieving desired aesthetic outcomes. Severely narrowed nostrils sometimes require a revision rhinoplasty procedure, which involves use of adipose tissue derived SVF, which shows promising results due to its smoothing, scar reduction and tissue repair properties. It also promotes angiogenesis, which is crucial for tissue regeneration. The use of adipose tissue has proven beneficial than traditional use of autologous cartilage grafting, which may involve complications like bending, infections due to lack of cytokines and growth factor support. Adipose tissue is used in the form of microfat (lipofilling) in non-surgical AFG. Microfat supplemented with ASCs offer a minimally invasive alternative for nasal enhancement. Lipofillers restores lost volume, improves contours, and rejuvenates the overall appearance of skin. The use of ASCs provide immunomodulatory properties, help to obtain faster recovery time, and allow patient to resume normal activities. It stimulates production of collagen, which gives elasticity to skin, thus reduce wrinkles and fine lines and give anti-aging effect to the skin use. While the use of ASCs-rich fat injections offers multiple benefits, it may not be a substitute for traditional surgical rhinoplasty, which is necessary for more extensive changes to the nasal structure and morphology[40].

Aesthetic dermatology

Aesthetic dermatology is a branch of dermatology that focuses on improving the appearance of the skin, particularly the face, neck and hands. The discipline of dermo-aesthetics was founded on three principles: Scaffolds, biochemical cues, and cells and cell derivatives[41]. Nanofat grafting is widely used in the dermoaesthetic field. An intradermal injection of nanofat is administered using a fan-shaped, retrograde strategy. The dimensions of nanofat are around 400 to 600 μm. The typical coverage area for 1 mL of nanofat is 1 cm by 1 cm. Miconeedling is a viable delivery method. Because nanofat has almost no filling properties, it can improve skin quality and rejuvenation through the injection of regenerative cells and ECM components[42]. Subcutaneous injections of 18 mL of nanofat-PRP were administered to 50 participants to assess the regenerative and face-lifting effects of nanofat grafting. At two to four weeks post-treatment, patients began to notice a lift and an improvement in skin quality. These effects persisted for up to six months following treatment. An improvement in dermal cellularity, elastic fiber, vascular density, and collagen density was observed in the biopsies[43]. Since nanofat grafting can provide long-term outcomes and appears more natural to the patient than other injectables, it is a potentially appealing and optimistic choice. The heterogeneous population of multipotent progenitors known as adipose-derived stem cells i.e. ASCs is abundant in adipose tissue. Adipose tissue contains stem cell niches that are highly interconnected to the ECM and other supporting cells. The niche regulates the biological properties and the proliferation, differentiation, and migration capabilities of ASCs in wound healing and tissue regeneration. As a physiological reaction to local injury, ASCs play a crucial role in preserving the dermo-epidermal structure. They are paracrine agents in skin regeneration. ASCs have the potential to develop into several skin components, including keratinocytes and dermal fibroblasts. AFG is considered the gold standard filler due to its exceptional qualities, including biocompatibility, adaptability, longevity, and natural appearance. In 1893, Neuber first used lipofilling to enhance soft tissues. Since then, its role in skin regeneration has been confirmed through several experiments.

Anti-photoaging

Photoaging is a complicated process that is primarily caused on by ultraviolet (UV) radiation from prolonged sun exposure. UV light can penetrate the skin and cause substantial modifications of the cutaneous connective tissue and form reactive oxygen species (ROS). Damage to DNA and the generation of ROS trigger an inflammatory response that changes the structure and function of cells. Oxidative stress causes damage via numerous mechanisms, including lipid and protein alterations, inflammation, immunological suppression, DNA damage, and signal transduction pathways that impact cell cycle, gene transcription and proliferation. It causes skin cancer, chronic inflammation, dermal collagen degradation, senescence, cell death, apoptosis, and elastic fiber degeneration. The goals of photoaging treatment are to improve the patient's aesthetics and functional well-being. ASCs have many beneficial effects, which include lower oxidative stress, prevent cell death and aging, enhance the production of ECM, skin regeneration, and control the progression of inflammation[44].

Dermal WAT (dWAT) has been found to have anti-aging target in recent decades. This is because dWAT is home to adipose stem cells and preadipocytes, the primary stem cell population thought to play a role in skin tissue regeneration. Fat and progenitor cells in the dWAT have distinct functions beyond those of the skin's antibacterial, antifibrotic, healing, and energy metabolism systems. Over time, the adipose layer under sun-exposed skin thins out. The photoaged skin's thin dermis show reduced adipogenesis and increased fibrosis. Sun exposure can lead to a significant increase in the quantity of IL-11, IL-1α, IL-6, and TNF-α released at the dermal junction, which can significantly impede the lipogenic differentiation of precursor cells. Furthermore, progenitor cells can transform into myofibroblasts by exposure to UV radiation. Additionally, subcutaneous ASCs are less susceptible to oxidative stress, UV light, and other aging factors than other skin stem cells, and their regulatory mechanism in differentiation may stem from epigenetic modifications rather than changes to their basic DNA sequence. The replacement of dermal fat by fibrous tissue results in mechanical abnormalities, such as true wrinkles and skin relaxation that are caused by microscopic skin structure and a loss of true skin volume. However, there are promising opportunities for dWAT remodeling with intradermally injected fat products that are enhanced with these different types of components[45].

The effects of adipose tissue derivatives on resistance to photoaging can have significant biological and therapeutic significance if the bioactive components from the adipose tissue fraction are further purified. A number of factors, including the removal of denatured collagen fibers, the regeneration of collagen fibers, the management of inflammation, and the prevention of ROS, have demonstrated varying degrees of therapeutic efficacy in adipose tissue derivatives. The survival rate of fat cells is an important factor in the fat transplantation process[45]. In vitro culture results showed that SVF-gel had greater long-term cell density and activity than nanofat and microfat, while a clinical trial of anti-wrinkle injections in the face and neck found that microfat restored better skin texture and instant subcutaneous volume than nanofat and microfat, respectively, due to a more integrated extracellular structure[46]. Compared to conventional nanofat, a comparative study revealed that SVF and ASC-enriched nanofat exhibited superior improvements in the reduction of wrinkles, increase of dermal thickness, collagen content, and the morphology of neocollagen[47]. It is true that SVF-gel has a higher density and survival rate of ASCs, but it also helps the healing of subcutaneous adipose tissue content. This may affect the survival of adipocytes and play a long-lasting secretory role in the future[48]. SVF-gel was thought to have a therapeutic impact on wrinkles and photoaging by raising the density of collagen in the dermis by activating fibroblasts to make type I collagen prepreptide and encouraging TGF-β1 expression[49].

Pigmentation treatment

Pigmentation refers to coloring of skin, hair, and eyes primarily determined by the presence of melanin. Melanin pigment is produced by melanocytes present between basal cells of epidermis through a process called melanogenesis. Tyrosinase regulate the process of melanogenesis. It catalyzes transformation of tyrosine amino acid into L-DOPA followed by its further oxidation into dopaquinone. Melanogenesis is influenced by various genetic, environmental, nutritional, hormonal regulations, medication, and endocrine disorder, which leads to various pigmentation disorders (such as hypopigmentation or hyperpigmentation)[50].

Hypopigmentation characterized by lighter than surrounding skin patches due to reduced melanin production. It could be due to genetic factors (generalized hypopigmentation) and autoimmune disorder (localized hypopigmentation). Currently, there are limited number of studies using ASCs for the treatment of hypopigmentation. However, ASCs have potential to improve pigmentation in individuals with localized hypopigmentation. It is a condition in which certain regions of the skin experience a reduction in pigment, leading to visibly lighter patches compared to the surrounding areas. Its most common cause is vitiligo, a chronic autoimmune disorder in which body`s own immune cells attack melanocytes which reduce melanin production. ASCs coupled melanocyte transplant have shown improved pigmentation. An innovative treatment of vitiligo is the use of adipose tissue derive extracellular fluid as it has shown visible improvements in clinical trials[51].

Hyperpigmentation is characterized by appearance of darker areas on skin due to hyper activity of melanogenic enzyme, which leads to the over production of melanin. These brown spots or patches can vary in size and color, ranging from light to dark brown. They can appear anywhere on the body, but are often most noticeable on exposed skin areas. The most common areas affected due to hyperpigmentation includes forehead, cheeks and chin. Hyperpigmentation has three major types: Melasma, solar lentigines (sunspot) and post-inflammatory hyperpigmentation (Table 2). Melasma is the most common form of hyperpigmentation among individuals with darker skin tone but is most prevalent among women during the age of 20-40 years[52]. It can occur due to multiple causes like hormonal changes such as in pregnancy, genetic disposition and skin irritation. All of these factors together or individually can stimulate a complex signalling pathway, leading to the over production of melanin from melanocytes. ADSCs have shown spectacular results in treatment of hyperpigmentation by down-regulating tyrosinase by the stimulation of cytokine and growth factor secretion, which promote tissue repair and healing[53]. Topical medications for hyperpigmentation work by adjusting the cellular pH to an optimal level of 5.5-6.2. This change in pH can influence various cellular signaling pathways, including those involved in melanin production, thereby helping to reduce hyperpigmentation. Solar lentigines occur due to prolonged sun exposure, UV rays diffuse into skin ultimately leading to an overproduction of ROS. ROS then influence tyrosinase activity leading to the overproduction of melanin. ASCs can be used to treat solar lentigines because they can stimulates the production of antioxidant cytokines, which is important for giving a lighter tone to the skin[54]. Post-inflammatory hyperpigmentation occurs due to injury or skin irritation including eczema, acne, burn, and exposure to heavy metals such as arsenic. They damage the dermis layer of skin, which induces abnormally high melanin synthesis, leading to appearance of dark patches. Adipose tissue derived exosomes gel in combination with CO₂ laser have shown improvement in pigmentation due to acne scars[55].

Table 2 Adipose tissue derived stem cells treatment in different types of hyperpigmentation.

Type of hyperpigmentation	Cause	Effect	Treatment
Melasma	Hormonal changes, genetic disposition, skin irritation	Melanocyte Hyperactivation	ADSC enriched nanofat have shown some improvement but due to involvement of hormonal and genetic factor its efficacy is still questionable
Solar Lentigines	Prolonged sun exposure, UV rays	Overproduction of ROS, influencing tyrosinase enzyme leading to melanin overproduction	ADSCs downregulate tyrosinase enzyme, gives lighter tone to the skin
Post-inflammatory hyperpigmentation	Skin injury, acne, burn, exposure to heavy metal	Damaged dermis layer causes appearance of dark patches due to disruption of melanocytes	Adipose tissue derived exosome gel in combination with CO2 laser improve skin texture

ADSC: Adipose-derived stem cells; UV: Ultraviolet; ROS: Reactive oxygen species.

Facial contour deformities

Facial contour deformities include a wide spectrum of soft tissue and skeletal deficiencies, often leading to altered skin appearance and aesthetic challenges. These deformities may vary from mild to serious depending on the cause and degree of damage. It can be due to acne, trauma, aging and medical conditions such as tumor or lip deformities. Acne is a skin disorder that occur in adolescence or young adults. Acne have shown different prevalence among different population ranging from 35% to 90%[56]. Severe acne scars, caused by loss to tissue during healing process, leaving denture on skin thus damaging facial aesthetics. These damaged facial aesthetics impact several psyclogical and social aspects of their lives. Those affected may experience feelings of depression, isolation, and an increased risk of suicidal behavior. However, the use of adipose tissue in the form of nanofat and PRP as adjuvant have shown increased dermal thickness, by boosting collagen production, which leads to reduced inflammation and dullness of scars[57]. ADSCs also influence several paracrine signaling pathway, which helps to repair skin wear and tear[58]. Traumas like facial burns damage skin and underlying tissues leaving scars and structural damage. These injuries can range from mild to sever depending upon degree of burn, can cause serious aesthetic, functional (tight or immobile areas of face such as lips) and psyclogical problems. Adipose tissue grafting is a promising therapy for the treatment of burn deformities due to their regenerative and tissue repair properties. ASCs can also be used to treat these deformities because they secrete cytokines and growth factors, thus stimulating body’s own immune cells to minimize scarring and restoring normal function of soft tissues. Aging also impact facial aesthetics by altering facial structures due to loss of fat and changes in skin elasticity. Adipose tissue fat grafts enriched with mesenchymal stem cells (MSCs) is being used to for facial volume restoration and improved overall aesthetic. These adipose tissue derived therapies have shown improved outcomes and higher patient satisfaction[58].

Adipose-derived exosomes: A cell-free therapy for aesthetic applications

Exosomes are small subset of extracellular vesicles produced by almost all cells of body including adipocytes, epithelial cells, fibroblasts, and nervous system cells. There typical size ranges for 40-160 nm[59]. Exosomes derived from adipose tissue derived- MSCs have shown a significant potential in regenerative medicine. These exosomes play a vital role in wound repair and tissue regeneration through various mechanisms such as enhance proliferation and migration of endothelial cells to the site of injury, which is a crucial step for angiogenesis, lead to minimize recovery time and diminished scaring[60]. Additionally, exosomes modulate immune activity and minimize inflammation to the site of injury, creating conditions conducive to healing. They transport regenerative molecules and genetic information to recipient cells, influencing their functions[61]. They also activate local stem and progenitor cells, thereby supporting the body's natural repair processes. Exosomes have significant potentials in skin rejuvenation, scar revision, and hair restoration by modulating anti-inflammatory and tissue repair pathways[62]. They are being used to treat dark spots, discoloration issues, reduce wrinkles and enhance skin elasticity[63].

Skin brightening cosmetic products are effective in reducing skin pigmentation and improving skin tone. They are becoming more popular for their ability to diminish the appearance of age spots, imperfections, and uneven skin tone. ASC-exosomes have numerous applications in personal care products[64]. A prospective, double blind, randomized placebo-controlled research found that a topical preparation containing ASC-exosomes reduced hyperpigmentation. Until the second week of treatment, there was no noticeable difference in the lowering of melanin levels between the test-treated and placebo-controlled areas. However, after 4 weeks of treatment, the changes were obvious and remained till 8 weeks after treatment. Despite the fact that instrumental measurement of melanin contents yielded statistically significant differences between placebo-controlled and test-treated areas, ASC-exosomes have been effective in vitro. However, clinically relevant brightening effects were not observed in volunteers, likely as a result of inefficient exosome delivery into the deep dermis[65]. It is recommended that future clinical trials investigate the use of improved transdermal distribution of ASC-exosomes. Chemical boosters, microneedles, thermal ablation, microdermabrasion, electroporation, cavitation ultrasound, iontophoresis, and ultrasound are just a few of the transdermal delivery techniques that have been developed for use in cosmetics and medicine. Several methods have been reported for the effective transdermal delivery of exosomes, including a microneedle patch made of keratin hydrogel, a needle-free jet injector, and iontophoresis. Both during and following the trial, no abnormalities of the skin were observed, including redness, swelling, scaling, itching, stinging, burning, tightness, or prickling[64].

Obesity has been demonstrated to influence an individual's holistic miRNA profile. MiR-450a-50 and the hedgehog-signaling pathway activate adipocyte development and lipid synthesis by adipocyte-derived exosomes. The found miRNAs may provide targeted routes to enhance weight loss with exosome therapy. However, this is just a theory at this point; no other published data or literature supports this claim. This theoretical possibility necessitates additional research to ascertain its practicability. AFG is a method that is commonly used all over the body and has many uses, including injecting fat to the buttocks for cosmetic reasons. The inconsistent and unpredictable survival rate of transplanted fat is a major obstacle to AFG[63]. Lipoaspirate and adipose-derived stem cell-rich SVF form cell-assisted lipotransfer (CAL), which improves autologous fat adipogenesis and angiogenesis in response to this obstacle. Given the regenerative and angiogenic capabilities of adipose stem cells, CAL has been shown in multiple published studies to improve graft life and engrafted fat volume retention[66]. Similar to adipose stem cells, adipose-derived exosomes are functional molecules released by adipose stem cells that improve fat graft retention[67]. The ideal concentrations, source cells, treatment duration, and potential side effects of exosome therapy have not been defined, while existing data indicate that exosomes produced from adipose tissue could be a good option to improve graft survival in lipotransfer[68]. Moreover, despite the remarkable potential of exosomes, exosomes in aesthetic medicine face challenges, including lack of FDA-approved products, cost variations among different exosome based treatments, and a lack of exploration of their full potential due to very little clinical trial.

POTENTIAL, LIMITATIONS, AND FUTURE PERSPECTIVES

Therapies derived from adipose tissue, especially those utilizing ASCs, have demonstrated significant potential in the field of aesthetic medicine. However, these therapies are not without limitations. The efficiency of ASC derived therapies can vary from person to person depending upon donors health status, age, site for tissue harvesting, isolation technique and factors affecting consistency of outcomes[69]. The potential risks associated with fat grafting, a procedure where ASCs are frequently utilized, include common complications like scarring, tissue damage, swelling, bruising, or the development of cysts[70]. Moreover, in some severe cases, patients have even reported serious issues like sudden vision loss. A case of 27 years old female was reported with sudden blindness after receiving an autologous fat injection into nasolabial fold[71]. After investigation, an embolus was observed due to entry of injected material into nasal artery, which then traveled to ophthalmic artery and resulted in sudden blockage and vision loss[71].

Currently, there is a lack of comprehensive data on the long-term efficacy and safety of these treatments. Lack of FDA-approved procedures and limited data on long-term safety due to very few clinical trials, arises ethical and regulatory concerns[72]. Adipose tissue-derived and exosome-derived therapies raise concerns about cost-effectiveness, primarily due to the wide range of costs associated with different treatment options. Safety concern regarding complications like massive bleeding during tissue harvesting should also be addressed by developing standardized protocol. All these issues regarding long-term efficiency and safety of ASCs derived therapies suggest the need for further studies through rigorous clinical trials and standardization of protocols for harvesting, isolation, etc. The majority of new adipose tissue derivatives are still in the early stages of preclinical research. There is a lack of large-scale clinical trials and follow-up data. The most critical issue is the absence of globally accepted practices for harvesting, processing, and injection methods[45]. Conducting more extensive and prolonged studies will provide valuable insights into the potential risks and benefits associated with these therapies.

Developing standardized protocols for adipose tissue harvesting, processing, and application is crucial for achieving consistent outcomes. This standardization will help minimize variability and ensure reproducibility of results[73]. There is currently no established process that is considered to be the gold standard for autologous fat transfer. This method has a minimal chance of hypersensitivity, foreign body, or auto inflammatory reactions since it uses the patient's own fat[74]. However, there are potential side effects and complications with adipose tissue derivatives that contain intracellular and extracellular structures, such as embolism, skin necrosis, hematoma, bruising, swelling, dysesthesia, and imperfection of the recipient's and donor's contours. A lack of post-graft survival, leading to complications such nodules, oil cysts, calcifications, etc., is another danger associated with adipose tissue derivatives used for filling[45].

One of the most actively researched and widely used cell sources for biologic treatments is human adipose-derived stromal cells. The multipotent adipose-derived stromal cells can be obtained from adipose tissue and then minimally treated in various ways to produce effective biologic treatments. Adipose tissue is an interesting cell source since it includes a variety of bioactive components that play a vital part in tissue maintenance and regeneration different functions of this tissue. Adipose tissue is becoming an increasingly common source for regenerative and repairing tissues in the field of biologics, hence it is vital to understand its structure, functions and mechanism of actions. Further research is needed to fully elucidate the biological mechanisms underlying the regenerative effects of adipose tissue[75].

Using SVF to help fat grafting is widely believed to increase tissue resistance to hypoxia and ischemia, which increases graft survival following large-volume engrafting without increasing the risk of complications[76]. Stem cell-related complications following transplantation, including lymphatic ganglia, heterotopic fibrosis, and other aberrant differentiations outside the transplant site, may be associated with these complex lipid compounds that are abundant in dissociated stem progenitor cells. Postoperative lymphadenopathy of the abdominal wall and inguinal region was documented in patients who underwent SVF-assisted fat grafting[77]. Transplanting fat derivatives is necessary to meet the minimum treatment' requirement, as stem cells in nonphysiological settings are difficult to manage[78]. The comparable benefits of secreted products, including stem cell exosomes, are a low tumorigenicity, a well-defined route, and a simple composition. Safe secretesomes can, however, carry chemicals that start an infection or help start the autoimmune response when they come into contact with secretory parts of infected or cancerous cells[79].

Despite a promising theoretical foundation for aesthetic-dermatological regenerative approach applications, there is currently no consensus on best practices and the technology is still evolving, leading to inconsistent and frequently disappointing results in the published literature. Skin regeneration pathophysiology is sequential rather than precise. When a cascade of events begins with platelets and their derived activity and continues through stem cell differentiation and fibroblastic activation, the skin's regeneration potential is activated. The combination of consequential processes should be regarded as the fundamental components of the restoration and improvement of skin regenerative capacity in the context of regenerative dermatology. A multi-target, sequential treatment plan including activation, stimulation/enhancement, and maintenance is necessary for the clinical application of regenerative medicine methods in dermo-aesthetics because the physiological mechanisms of stem cell action cannot be excluded. The comprehension of the pathophysiology of skin regeneration will open up new avenues for the development of a new era of cosmetic dermatology, which comprises therapeutic strategies that replicate physiological pathways[42].

Tissue engineering and gene editing have great potential to improve regenerative abilities of cells, which could lead to the restoration of function and their ability to repair damaged tissue. Tissue engineered employ various methods such as the use of biomaterial scaffolds and cell-based therapies. While genome editing aims to alter, delete, add or replace the nucleotides in the DNA within the cells. The regenerative properties of stem cells produced from adipose tissue can be improved through gene editing by altering genes that promote proliferation, differentiation, or the production of growth factors[80,81]. The exact spatial organization of cells and biomaterials allows for the creation of sophisticated, functional adipose tissue structures using advanced techniques such as 3D bioprinting[82]. The combinations of adipose tissue-based therapies with other aesthetic treatments, such as laser therapy holds significant potentials. Evidence suggests that fractional CO₂ laser treatment when combined with adipose tissue extract can slow the progression of hypertrophic scars. This method not only offers a novel adipogenic acellular treatment for the clinical treatment of hypertrophic scars, but it also gives basic research data for the clinical use of lasers and adipose tissue extract to cure scars. Further research is necessary to gain a comprehensive understanding of the fundamental processes[83].

CONCLUSION

Aesthetic medicine improves individual attraction and appeal. Traditional aesthetic procedures can cause allergic reactions, are temporary and require repeated sessions to maintain the desired look. Adipose tissue is a promising alternative to conventional cosmetic procedures for natural, long-lasting outcomes due to their regenerative characteristics, accessibility, and adaptability. Adipose tissue can also be employed as pure grafts, SVF, nano fat, or ASCs. These forms of adipose tissue treatment have limitations, such as variability in cell viability, graft survival rates, and potential for scarring. Exosomes derived from adipose tissue present an effective cell-free therapy. They are used to treat dark spots, discoloration issues, reduce wrinkles and enhance skin elasticity. However, more research is needed through robust clinical trials, as well as standardization of methods for harvesting, isolation, and other procedures.