Over the last 20 years, research into the Meibomian glands of the eyelids has increased exponentially and is now widely recognized as a field of research. It is all the more astonishing that knowledge about another type of gland in the eyelids, the Moll glands or ciliary glands, has almost stagnated and there has been little to almost no progress, even though this type of gland as a whole takes up a relatively large volume in the upper and lower eyelids. There is not much information about the namesake Moll or the function of the glands although these are listed in nearly every textbook of anatomy, histology and ophthalmology. For this reason, we set out to compile the existing knowledge about the Moll glands of the eyelids in order to create a basis for follow-up studies and to stimulate research into this type of gland. In our literature research, we went back to the middle of the 19th century and made contact with a descendant of the Moll family and illustrate their relevance for the present. The structure of the secretory part of the Moll glands is very well described, a number of secretory products are known, but the current state of research allows only very rough speculations about their function. The overview provides numerous interesting insights, which, however, raise more questions than they provide answers.

How to elicit and harness regeneration is a major issue in wound healing. Skin injury in most amniotes leads to repair rather than regeneration, except in hair and feathers. Feather follicles are unique organs that undergo physiological cyclic renewal, supported by a dynamic stem cell niche. During normal feather cycling, growth-phase proximal follicle collar bulge stem cells adopt a ring configuration. At the resting and initiation phases, these stem cells descend to the dermal papilla to form papillary ectoderm and ascend to the proximal follicle in a new growth phase. Plucking resting-phase feathers accelerates papillary ectoderm cell activation. Plucking growth-phase feathers depletes collar bulge stem cells; however, a blastema reforms the collar bulge stem cells, expressing KRT15, LGR6, Sox9, integrin-α6, and tenascin C. Removing the follicle base and dermal papilla prevents feather regeneration. Yet, transplanting an exogenous dermal papilla to the follicle base can induce re-epithelialization from the lower follicle sheath, followed by feather regeneration. Thus, there is a stepwise regenerative strategy using stem cells located in the collar bulge, papillary ectoderm, and de-differentiated lower follicle sheath to generate new feathers after different levels of injuries. This adaptable regenerative mechanism is based on the hierarchy of stem cell regenerative capacity and underscores the remarkable resilience of feather follicle regenerative abilities.

Liver regeneration is supported by hepatocytes and, in certain conditions, biliary epithelial cells (BECs). BECs are facultative liver stem cells that form organoids in culture and engraft in damaged livers. However, BEC heterogeneity in the homeostatic liver remains to be fully elucidated. Here, we exploit systemic lentiviral vector (LV) administration to achieve efficient and lifelong gene transfer to BECs in mice. We find that LV-marked BECs retain organoid formation potential and predominantly respond to liver damage; however, they are less clonogenic and display a hepatocyte-primed transcriptome compared to untransduced BECs. We thus identify a BEC subset committed to hepatocyte lineage in the absence of liver damage, characterized by a transcriptional network orchestrated by hepatocyte nuclear factor 4α. We also report in vivo targeting of such BECs in non-human primates. This work highlights intrinsic BEC heterogeneity and that in vivo LV gene transfer to the liver may persist following BEC-mediated repair of hepatic damage.

Loss of ZIP13 causes Ehlers-Danlos syndrome spondylodysplastic type 3 involving connective tissue dysplasias associated with a reduction in muscular strength. However, ZIP13 role in skeletal muscle homeostasis, particularly for the regulation of muscle satellite cells (MuSCs), remains poorly understood. In this study, we investigated Zip13-knockout (KO) mice and found a reduction in MuSCs of Zip13-KO mice, in which the quiescent and activated phase balances were disrupted. To clarify the physiological role and dynamics of ZIP13 expression in MuSCs, we generated Zip13-GFP knock-in (KI) mice encoding GFP at the Zip13 locus, which showed that ZIP13 contributes to the phase balance regulation of quiescent and activated MuSCs and their functions. Indeed, Zip13-KO mice exhibited delayed recovery from skeletal muscle injury, indicating ZIP13 requirement for proper skeletal muscle regeneration. Moreover, GFP expression was reduced in the MuSCs of homozygous Zip13-GFP KI mice whose intact ZIP13 expression was perturbed, suggesting that positive feedback mechanisms exist to maintain ZIP13 expression. Altogether, our results illustrate that ZIP13 might be positively involved in skeletal muscle regeneration by controlling the quiescent/activated phase balance of MuSCs through autoregulatory ZIP13 expression, and that newly generated Zip13-GFP KI mice would be useful for investigating the roles and dynamics of ZIP13-expressing cells.

The epidermis provides a protective barrier against hostile environments. However, our knowledge of how this barrier forms during development and is subsequently maintained remains incomplete. The infundibulum is a cylindrical epidermal tissue compartment that serves as an outlet for hair follicles protruding from the skin and the excretion of the sebaceous glands that are essential for proper skin function. In this study, we applied quantitative fate mapping to address how infundibulum are maintained during adulthood. We demonstrate that progenitors build and maintain tissues through stochastic cell fate choices. Long-term analysis identified a preferential transient contribution from cells initially located at the bottom of the structure to the maintenance of the tissue, with bursts of local progenitor expansion associated with the phases of hair growth. Beyond providing compartment-wide insights into progenitor cell dynamics in infundibulum, these findings demonstrate how spatiotemporal regulation controls transient progenitor dominance.

Meibomian glands secrete lipid-rich meibum, which prevents tear evaporation. Aging-related Meibomian gland shrinkage may result in part from stem cell exhaustion and is associated with evaporative dry eye disease, a common condition lacking effective treatment. The identities and niche of Meibomian gland stem cells and the signals controlling their activity are poorly defined. Using snRNA-seq, in vivo lineage tracing, ex vivo live imaging, and genetic studies in mice, we identify markers for stem cell populations that maintain distinct regions of the gland and uncover Hedgehog (Hh) signaling as a key regulator of stem cell proliferation. Consistent with this, we show that human Meibomian gland carcinoma exhibits increased Hh signaling. Aged glands display decreased Hh and EGF signaling, deficient innervation, and loss of collagen I in niche fibroblasts, indicating that alterations in both glandular epithelial cells and their surrounding microenvironment contribute to age-related degeneration. These findings suggest new approaches to treat aging-associated Meibomian gland loss.

In eutherian mammals, the embryonic cloaca is partitioned into genitourinary and anorectal canals by the urorectal septum. At the caudal end of the mouse embryo, the urorectal septum contributes to the perineum, which separates the anus from the external genitalia. Growth of the urorectal septum displaces cloacal endoderm to the surface of the perineum, where it is incorporated into epidermis, an enigmatic fate for endodermal cells. Here we show that endodermal cells differentiate into true epidermis in the perineum, expressing basal, spinous, and granular cell markers. Endodermal epidermis is lost through terminal differentiation and desquamation postnatally, when it is replaced by ectoderm. Live imaging and single-cell tracking reveal that ectodermal cells move at a faster velocity in a lateral-to-medial direction, converging towards the narrow band of endoderm between the anus and external genitalia. Although the perineum is sexually dimorphic, similar spatiotemporal patterns of cell movement were observed in males and females. These results demonstrate that cloacal endoderm differentiates into a non-renewing, transient epidermis at the midline of the perineum. Differential movement of endodermal and ectodermal cells suggests that perineum epidermis develops by convergent extension. These findings provide a foundation for further studies of perineum development and of sex-specific epidermal phenotypes.

Hematopoiesis is the process that generates the cells of the blood and immune system from hematopoietic stem and progenitor cells (HSPCs) and represents the system with the most rapid cell turnover in a mammalian organism. HSPC differentiation trajectories, their underlying molecular mechanisms, and their dysfunctions in hematologic disorders are the focal research questions of experimental hematology. While HSPC transplantations in murine models are the traditional tool in this research field, recent advances in genome editing and next generation sequencing resulted in the development of many fundamentally new approaches for the analyses of mammalian hematopoiesis in situ and at single cell resolution. The current review will cover many recent developments in this field in murine models, from the bulk lineage tracing studies of HSPC differentiation to the barcoding of individual HSPCs with Cre-recombinase, Sleeping Beauty transposase, or CRISPR/Cas9 tools, to map hematopoietic cell fates, together with their transcriptional and epigenetic states. We also address studies of the clonal dynamics of human hematopoiesis, from the tracing of HSPC clonal behaviours based on viral integration sites in gene therapy patients to the recent analyses of unperturbed human hematopoiesis based on naturally accrued mutations in either nuclear or mitochondrial genomes. Such studies are revolutionizing our understanding of HSPC biology and hematopoiesis both under homeostatic conditions and in the response to various forms of physiological stress, reveal the mechanisms responsible for the decline of hematopoietic function with age, and in the future may advance the understanding and management of the diverse disorders of hematopoiesis.

Immunotherapy has become a key new pillar of cancer treatment, and this has sparked interest in understanding mechanisms of cancer immune evasion. It has long been appreciated that cancers are constituted by heterogeneous populations of tumour cells. This feature is often fuelled by specialized cells that have molecular programs resembling tissue stem cells. Although these cancer stem cells (CSCs) have capacity for unlimited self-renewal and differentiation, it is increasingly evident that some CSCs are capable of achieving remarkable immune resistance. Given that most immunotherapy regiments have overlooked CSC-specific immune-evasive mechanisms, many current treatment strategies often lead to cancer relapse. This Review focuses on advancements in understanding how CSCs in solid tumours achieve their unique immune-evasive properties, enabling them to drive tumour regrowth. Moreover, as cancers often arise from tissue stem cells that acquired oncogenic mutations, we discuss how tissue stem cells undergoing malignant transformation activate intrinsic immune-evasive mechanisms and establish close interactions with suppressive immune cells to escape immune surveillance. In addition, we summarize how in advanced disease stages, CSCs often hijack features of normal stem cells to resist antitumour immunity. Finally, we provide insights in how to design a new generation of cancer immunotherapies to ensure elimination of CSCs.

Skin regeneration, repair, and the promotion of hair growth are intricate and dynamic processes essential for preserving the overall health, functionality, and appearance of both skin and hair. These processes involve a coordinated interplay of cellular activities and molecular signaling pathways that ensure the maintenance and restoration of skin integrity and hair vitality. Recent advancements in regenerative medicine have underscored the significant role of mesenchymal stem cell (MSC)-derived exosomes as key mediators in these processes. Exosomes, emerging as a promising cell-free therapy in tissue engineering, hold substantial potential due to their ability to influence various biological functions. This review explores the mechanisms by which MSC-derived exosomes facilitate skin regeneration and repair, and hair growth, their therapeutic applications, and the future research directions in this emerging field.

Surgical site infections (SSIs) pose a significant challenge to healthcare systems by elevating patient morbidity and mortality and driving up financial costs. Preoperative skin preparation is crucial for preventing SSIs; however, certain traditional methods of hair removal have been found to increase the risk of SSI development. Mechanical epilation and waxing constitute two relatively explored methods of hair removal, which may hold potential to accelerate wound healing due to the activation of stem cells within hair follicles. This review assesses the efficacy of preoperative hair removal via waxing and mechanical epilation in reducing SSI incidence.

This systematic review was prospectively registered with PROSPERO (ref: CRD42023423798) and a protocol previously published in a peer-reviewed journal. All findings are reported according to PRISMA guidelines. A comprehensive search of Medline, Embase, CENTRAL, ClinicalTrials.gov and CINAHL. Inclusion criteria encompassed adult patients undergoing any surgical procedure, comparing waxing or epilation against other hair removal methods or no hair removal, with SSI incidence as the primary outcome. There was no restriction on study size or quality to ensure a comprehensive literature evaluation.

The review found no studies meeting the selection criteria out of 576 records screened.

This review has identified no literature regarding the use of waxing and mechanical epilation as methods of preoperative hair removal. The lack of experimental evidence combined with the potential physiological advantages of these techniques indicate that this could be a valuable area of future research. These techniques may represent novel approaches to SSI prevention, particularly beneficial in high-risk surgical disciplines like vascular surgery.

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=423798, PROSPERO (CRD42023423798).

Ectodermal organs, such as hair follicles, originate from simple epithelial and mesenchymal sheets through a complex developmental process driven by interactions between these cell types. This process involves dermal condensation, placode formation, bud morphogenesis, and organogenesis, and all of these processes require intricate interactions among various tissues. Recent research has emphasized the crucial role of reciprocal and dynamic interactions between cells and the extracellular matrix (ECM), referred to as the "dynamic duo", in the development of ectodermal organs. These interactions provide spatially and temporally changing biophysical and biochemical cues within tissues. Using the hair follicle as an example, this review highlights two types of cell-ECM adhesion units-focal adhesion-type and hemidesmosome-type adhesion units-that facilitate communication between epithelial and mesenchymal cells. This review further explores how these adhesion units, along with other cell-ECM interactions, evolve during hair follicle development and regeneration, underscoring their importance in guiding both developmental and regenerative processes.

There is an urgent need for new treatments to solve hair loss problem. As mesenchymal stem cells were proved to have effects on promoting tissue repair and regeneration, in which the exosome plays a vital role, we aim to investigate the influence of umbilical cord mesenchymal stem cells exosome (UCMSC-Exos) on hair growth and its mechanism.

The hUCMSC-Exos were extracted by ultracentrifugation. Primary fibroblasts were cultured with or without hUCMSC-Exos and cell proliferation was evaluated by CCK-8 assay. C57BL/6 mice model of depilation-induced hair regrowth was treated with either hUCMSC-Exos (200 μg/mL) or PBS on one side of the dorsal back. Real time quantitative PCR, flow cytometry analysis, immunohistochemistry and Immunofluorescent staining were used to analyze the regulative effect of hUCMSC-Exos on hair follicle stem/progenitor cells and Wnt/β-catenin pathway.

The proliferation of fibroblasts incubated with hUCMSC-Exos at the concentration of 200 μg/mL was greater than other groups. Treatment with hUCMSC-Exos resulted in rapid reentry into anagen. Hair follicle stem/progenitor cell markers (K15, Lgr5, Lgr6, CD34 and Lrig1) and Wnt/β-catenin pathway related factors (Wnt5, Lef1, Lrp5 and β-catenin) were increased in hUCMSC-Exos-injected region.

hUCMSC-Exos promote fibroblasts proliferation and accelerate mouse hair regrowth by upregulating hair follicle stem/progenitor cell and Wnt/β-catenin pathway, which suggests potential therapeutic approaches for hair loss disorders.

Fracture management largely relies on the bone's inherent healing capabilities and, when necessary, surgical intervention. Currently, there are limited osteoinductive therapies to promote healing, making targeting skeletal stem/progenitor cells (SSPCs) a promising avenue for therapeutic development. A limiting factor for this approach is our incomplete understanding of the molecular mechanisms governing SSPCs' behavior. We have recently identified that the Leucine-rich repeat-containing G-protein coupled receptor 6 (Lgr6) is expressed in sub-populations of SSPCs, and is required for maintaining bone volume during adulthood and for proper fracture healing. Lgr family members (Lgr4-6) are markers of stem cell niches and play a role in tissue regeneration primarily by binding R-Spondin (Rspo1-4). This interaction promotes canonical Wnt (cWnt) signaling by stabilizing Frizzled receptors. Interestingly, our findings here indicate that Lgr6 may also influence cWnt-independent pathways. Remarkably, Lgr6 expression was enhanced during Bmp-mediated osteogenesis of both human and murine cells. Using biochemical approaches, RNA sequencing, and bioinformatic analysis of published single-cell data, we found that elements of BMP signaling, including its target gene, pSMAD, and gene ontology pathways, are downregulated in the absence of Lgr6. Our findings uncover a molecular interdependency between the Bmp pathway and Lgr6, offering new insights into osteogenesis and potential targets for enhancing fracture healing.

Diseases of the female reproductive system, especially malignant tumors, pose a serious threat to women's health worldwide. One of the key factors limiting research progress in this area is the lack of representative models. Organoid technology, especially tumor organoids, has been increasingly applied in the study of female reproductive system tumors due to their high heterogeneity, close resemblance to the physiological state, easy acquisition and cultivation advantages. They play a significant role in understanding the origin and causes of tumors, drug screening, and personalized treatment and more. This article reviews the organoid models for the female reproductive system, focusing on the cancer research advancements. It discusses the methods for constructing tumor organoids of the female reproductive tract and summarizes the limitations of current research. The aim is to offer a reference for future development and application of these organoid models, contributing to the advancement of anti-tumor drugs and treatment strategies for female reproductive tract cancer patients.

Organ development is guided by a space-time landscape that constraints cell behavior. This landscape is challenging to characterize for the hair follicle - the most abundant mini organ - due to its complex microscopic structure and asynchronous development. We developed 3DEEP, a tissue clearing and spatial transcriptomic strategy for characterizing tissue blocks up to 400 µm in thickness. We captured 371 hair follicles at different stages of organogenesis in 1 mm3 of skin of a 12-hour-old mouse with 6 million transcripts from 81 genes. From this single time point, we deconvoluted follicles by age based on whole-organ molecular pseudotimes to animate a stop-motion 3D atlas of follicle development along its trajectory. We defined molecular stages for hair follicle organogenesis and characterized the order of emergence for its structures, differential signaling dynamics at its top and bottom, morphogen shifts preceding and accompanying structural changes, and series of structural changes leading to the formation of its canal and opening. We further found that hair follicle stem cells and their niche are established and stratified early in organogenesis, before the formation of the hair bulb. Overall, this work demonstrates the power of increased depth of spatial transcriptomics to provide a four-dimensional analysis of organogenesis.

We have developed and validated a highly specific, versatile antibody to the extracellular domain of human LGR5 (α-LGR5). α-LGR5 detects LGR5 overexpression in >90% of colorectal cancer (CRC), hepatocellular carcinoma (HCC) and pre-B-ALL tumour cells and was used to generate an Antibody-Drug Conjugate (α-LGR5-ADC), Bispecific T-cell Engager (α-LGR5-BiTE) and Chimeric Antigen Receptor (α-LGR5-CAR). α-LGR5-ADC was the most effective modality for targeting LGR5+ cancer cells in vitro and demonstrated potent anti-tumour efficacy in a murine model of human NALM6 pre-B-ALL driving tumour attrition to less than 1% of control treatment. α-LGR5-BiTE treatment was less effective in the pre-B-ALL cancer model yet promoted a twofold reduction in tumour burden. α-LGR5-CAR-T cells also showed specific and potent LGR5+ cancer cell killing in vitro and effective tumour targeting with a fourfold decrease in pre-B-ALL tumour burden relative to controls. Taken together, we show that α-LGR5 can not only be used as a research tool and a biomarker but also provides a versatile building block for a highly effective immune therapeutic portfolio targeting a range of LGR5-expressing cancer cells.

The hair follicle and nail unit develop and regenerate through epithelial-mesenchymal interactions. Here, we review some of the key signals and molecular interactions that regulate mammalian hair follicle and nail formation during embryonic development and how these interactions are reutilized to promote their regeneration during adult homeostasis and in response to skin wounding. Finally, we highlight the role of some of these signals in mediating human hair follicle and nail conditions.

The skin epidermis is continually influenced by a myriad of internal and external elements. At its basal layer reside epidermal stem cells, which fuels epidermal renovation and hair regeneration with powerful self-renewal ability, as well as keeping diverse signals that direct their activity under surveillance with quick response. The importance of epidermal stem cells in wound healing and immune-related skin conditions has been increasingly recognized, and their potential for clinical applications is attracting attention. In this review, we delve into recent advancements and the various physiological and psychological factors that govern distinct epidermal stem cell populations, including psychological stress, mechanical forces, chronic aging, and circadian rhythm, as well as providing an overview of current methodological approaches. Furthermore, we discuss the pathogenic role of epidermal stem cells in immune-related skin disorders and their potential clinical applications.

Meibomian glands secrete lipid-rich meibum, which prevents tear evaporation. Aging-related Meibomian gland shrinkage may result in part from stem cell exhaustion and is associated with evaporative dry eye disease, a common condition lacking effective treatment. The identities and niche of Meibomian gland stem cells and the signals controlling their activity are poorly defined. Using snRNA-seq, in vivo lineage tracing, ex vivo live imaging, and genetic studies in mice, we identified markers for stem cell populations that maintain distinct regions of the gland and uncovered Hh signaling as a key regulator of stem cell proliferation. Consistent with this, human Meibomian gland carcinoma exhibited increased Hh signaling. Aged glands displayed decreased Hh and EGF signaling, deficient innervation, and loss of collagen I in niche fibroblasts, indicating that alterations in both glandular epithelial cells and their surrounding microenvironment contribute to age-related degeneration. These findings suggest new approaches to treat aging-associated Meibomian gland loss.

Skin stem cells (SCs) play a pivotal role in supporting tissue homeostasis. Several types of SCs are responsible for maintaining and regenerating skin tissue. These include bulge SCs and others residing in the interfollicular epidermis, infundibulum, isthmus, sebaceous glands, and sweat glands. The emergence of skin SCs commences during embryogenesis, where multipotent SCs arise from various precursor populations. These early events set the foundation for the diverse pool of SCs that will reside in the adult skin, ready to respond to tissue repair and regeneration demands. A network of molecular cues regulates skin SC behavior, balancing quiescence, self-renewal, and differentiation. The disruption of this delicate equilibrium can lead to SC exhaustion, impaired wound healing, and pathological conditions such as skin cancer. The present review explores the intricate mechanisms governing the development, activation, and differentiation of skin SCs, shedding light on the molecular signaling pathways that drive their fate decisions and skin homeostasis. Unraveling the complexities of these molecular drivers not only enhances our fundamental knowledge of skin biology but also holds promise for developing novel strategies to modulate skin SC fate for regenerative medicine applications, ultimately benefiting patients with skin disorders and injuries.

Taste buds, the neuroepithelial organs responsible for the detection of gustatory stimuli in the oral cavity, arise from stem/progenitor cells among nearby basal keratinocytes. Using genetic lineage tracing, Lgr5 and Lgr6 were suggested as the specific markers for the stem/progenitor cells of taste buds, but recent evidence implied that taste buds may arise even in the absence of these markers. Thus, we wanted to verify the genetic lineage tracing of lingual Lgr5- and Lgr6-expressing cells. Unexpectedly, we found that antibody staining revealed more diverse Lgr5-expressing cells inside and outside the taste buds of circumvallate papillae than was previously suggested. We also found that, while tamoxifen-induced genetic recombination occurred only in cells expressing the Lgr5 reporter GFP, we did not see any increase in the number of recombined daughter cells induced by consecutive injections of tamoxifen. Similarly, we found that cells expressing Lgr6, another stem/progenitor cell marker candidate and an analog of Lgr5, also do not generate recombined clones. In contrast, Lgr5-expressing cells in fungiform papillae can transform into Lgr5-negative progeny. Together, our data indicate that lingual Lgr5- and Lgr6-expressing cells exhibit diversity in their capacity to transform into Lgr5- and Lgr6-negative cells, depending on their location. Our results complement previous findings that did not distinguish this diversity.

Neuroblastoma (NB) is a cancer of the peripheral nervous system found in children under 15 years of age. It is the most frequently diagnosed cancer during infancy, accounting for ~12% of all cancer-related deaths in children. Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) is a membrane receptor that is associated with the primary tumor formation and metastasis of cancers in the gastrointestinal system. Remarkably, high levels of LGR5 are found in NB tumor cells, and high LGR5 expression is strongly correlated with poor survival. Antibody-drug conjugates (ADCs) are monoclonal antibodies that are covalently linked to cell-killing cytotoxins to deliver the payloads into cancer cells. We generated an ADC with an anti-LGR5 antibody and pyrrolobenzodiazepine (PBD) dimer-based payload SG3199 using a chemoenzymatic conjugation method. The resulting anti-LGR5 ADC was able to inhibit the growth of NB cells expressing LGR5 with high potency and specificity. Importantly, the ADC was able to completely inhibit the growth of NB xenograft tumors in vivo at a clinically relevant dose for the PBD class of ADCs. The findings support the potential of targeting LGR5 using the PBD class of payload for the treatment of high-risk NBs.

The wound-healing process is a paradigm of the directed migration of various pools of stem cells from their niche to the site of injury where they replenish damaged cells. Two decades have elapsed since the observation that wounding activates multipotent hair follicle stem cells to infiltrate the epidermis, but the cues that coax these cells out of their niche remain unknown. Here, we report that Caspase-1, a protein classically known as an integral component of the cytosolic inflammasome, is secreted upon wounding and has a non-canonical role in the extracellular milieu. Through its caspase activation recruitment domain (CARD), Caspase-1 is sufficient to initiate the migration of hair follicle stem cells into the epidermis. Uncovering this novel function of Caspase-1 also facilitates a deeper understanding of the mechanistic basis of the epithelial hyperplasia found to accompany numerous inflammatory skin diseases.

Cross-species transmission of coronaviruses has been continuously posing a major challenge to public health. Pigs, as the major animal reservoirs for many zoonotic viruses, frequently mediate viral transmission to humans. This study comprehensively mapped the relationship between human and porcine coronaviruses through in-depth bioinformatics analysis. We found that human coronavirus OC43 and porcine coronavirus PHEV share a close phylogenetic relationship, evidenced by high genomic homology, similar codon usage patterns and comparable tertiary structure in spike proteins. Inoculation of infectious OC43 viruses in organoids derived from porcine small and large intestine demonstrated that porcine intestinal organoids (pIOs) are highly susceptible to human coronavirus OC43 infection and support infectious virus production. Using transmission electron microscopy, we visualized OC43 viral particles in both intracellular and extracellular compartments, and observed abnormalities of multiple organelles in infected organoid cells. Robust OC43 infections in pIOs result in a significant reduction of organoids viability and widespread cell death. This study bears essential implications for better understanding the evolutionary origin of human coronavirus OC43, and provides a proof-of-concept for using pIOs as a model to investigate cross-species transmission of human coronavirus.

Stem cells play a critical role in cancer development by contributing to cell heterogeneity, lineage plasticity, and drug resistance. We created gene expression networks from hundreds of mouse tissue samples (both normal and tumor) and integrated these with lineage tracing and single-cell RNA-seq, to identify convergence of cell states in premalignant tumor cells expressing markers of lineage plasticity and drug resistance. Two of these cell states representing multilineage plasticity or proliferation were inversely correlated, suggesting a mutually exclusive relationship. Treatment of carcinomas in vivo with chemotherapy repressed the proliferative state and activated multilineage plasticity whereas inhibition of differentiation repressed plasticity and potentiated responses to cell cycle inhibitors. Manipulation of this cell state transition point may provide a source of potential combinatorial targets for cancer therapy.

The nail matrix containing stem cell populations produces nails and may contribute to fingertip regeneration. Nails are important tissues that maintain the functions of the hand and foot for handling objects and locomotion. Tumor chemotherapy impairs nail growth and, in many cases, loses them, although not permanently. In this report, we have achieved the successful differentiation of nail stem (NS)-like cells from human-induced pluripotent stem cells (iPSCs) via digit organoids by stepwise stimulation, tracing the molecular processes involved in limb development. Comprehensive mRNA sequencing analysis revealed that the digit organoid global gene expression profile fits human finger development. The NS-like cells expressed Lgr6 mRNA and protein and produced type-I keratin, KRT17, and type-II keratin, KRT81, which are abundant in nails. Furthermore, we succeeded in producing functional Lgr6-reporter human iPSCs. The reporter iPSC-derived Lgr6-positive cells also produced KRT17 and KRT81 proteins in the percutaneously transplanted region. To the best of our knowledge, this is the first report of NS-like cell differentiation from human iPSCs. Our differentiation method and reporter construct enable the discovery of drugs for nail repair and possibly fingertip-regenerative therapy.

Sebaceous glands (SGs), as holocrine-secreting appendages, lubricate the skin and play a central role in the skin barrier. Large full-thickness skin defects cause overall architecture disruption and SG loss. However, an effective strategy for SG regeneration is lacking. Organoids are 3D multicellular structures that replicate key anatomical and functional characteristics of in vivo tissues and exhibit great potential in regenerative medicine. Recently, considerable progress has been made in developing reliable procedures for SG organoids and existing SG organoids recapitulate the main morphological, structural and functional features of their in vivo counterparts. Engineering approaches empower researchers to manipulate cell behaviors, the surrounding environment and cell-environment crosstalk within the culture system as needed. These techniques can be applied to the SG organoid culture system to generate functionally more competent SG organoids. This review aims to provide an overview of recent advancements in SG organoid engineering. It highlights some potential strategies for SG organoid functionalization that are promising to forge a platform for engineering vascularized, innervated, immune-interactive and lipogenic SG organoids. We anticipate that this review will not only contribute to improving our understanding of SG biology and regeneration but also facilitate the transition of the SG organoid from laboratory research to a feasible clinical application.

Wound healing, a critical biological process vital for tissue restoration, has spurred a global market exceeding $15 billion for wound care products and $12 billion for scar treatment. Chronic wounds lead to delayed or impaired wound healing. Natural bioactive compounds, prized for minimal side effects, stand out as promising candidates for effective wound healing. In response, researchers are turning to nanotechnology, employing the encapsulation of these agents into drug delivery carriers. Drug delivery system will play a crucial role in enabling targeted delivery of therapeutic agents to promote tissue regeneration and address underlying issues such as inflammation, infection, and impaired angiogenesis in chronic wound healing. Drug delivery carriers offer distinct advantages, exhibiting a substantial ratio of surface area to volume and altered physical and chemical properties. These carriers facilitate sustained and controlled release, proving particularly advantageous for the extended process of wound healing, that typically comprise a diverse range of components, integrating both natural and synthetic polymers. Additionally, they often incorporate bioactive molecules. Despite their properties, including poor solubility, rapid degradation, and limited bioavailability, various natural bioactive agents face challenges in clinical applications. With a global research, emphasis on harnessing nanomaterial for wound healing application, this research overview engages advancing drug delivery technologies to augment the effectiveness of tissue regeneration using bioactive molecules. Recent progress in drug delivery has poised to enhance the therapeutic efficacy of natural compounds in wound healing applications.

Vitiligo is an autoimmune skin disease caused by cutaneous melanocyte loss. Although phototherapy and T cell suppression therapy have been widely used to induce epidermal re-pigmentation, full pigmentation recovery is rarely achieved due to our poor understanding of the cellular and molecular mechanisms governing this process. Here, we identify unique melanocyte stem cell (McSC) epidermal migration rates between male and female mice, which is due to sexually dimorphic cutaneous inflammatory responses generated by ultra-violet B exposure. Using genetically engineered mouse models, and unbiased bulk and single-cell mRNA sequencing approaches, we determine that manipulating the inflammatory response through cyclooxygenase and its downstream prostaglandin product regulates McSC proliferation and epidermal migration in response to UVB exposure. Furthermore, we demonstrate that a combinational therapy that manipulates both macrophages and T cells (or innate and adaptive immunity) significantly promotes epidermal melanocyte re-population. With these findings, we propose a novel therapeutic strategy for repigmentation in patients with depigmentation conditions such as vitiligo.

A characteristic feature of repair processes in mammals is the formation of scar tissue at the site of injury, which is designed to quickly prevent contact between the internal environment of the organism and the external environment. Despite this general pattern, different organs differ in the degree of severity of scar changes in response to injury. One of the areas in which regeneration after wounding leads to the formation of a structure close to the original one is the abdominal skin of laboratory rats. Finding out the reasons for such a phenomenon is essential for the development of ways to stimulate full regeneration. The model of skin wound healing in the abdominal region of laboratory animals was reproduced in this work. It was found that the wound surface is completely epithelialized on the abdomen by 20 days, while on the back-by 30 days. The qPCR method revealed higher expression of marker genes of skin stem cells (Sox9, Lgr6, Gli1, Lrig1) in the intact skin of the abdomen compared to the back, which corresponded to a greater number of hairs with which stem cells are associated on the abdomen compared to the back. Considering that some stem cell populations are associated with hair, it can be suggested that one of the factors in faster regeneration of abdominal skin in the rat is the greater number of stem cells in this area.

The touch dome (TD) keratinocytes are specialized epidermal cells that intimately associate with the light touch sensing Merkel cells (MCs). The TD keratinocytes function as a niche for the MCs and can induce de novo hair follicles upon stimulation; however, how the TD keratinocytes are maintained during homeostasis remains unclear. scRNA-seq identified a specific TD keratinocyte marker, Tenascin-C (TNC). Lineage tracing of Tnc-expressing TD keratinocytes revealed that these cells maintain themselves as an autonomous epidermal compartment and give rise to MCs upon injury. Molecular characterization uncovered that, while the transcriptional and chromatin landscape of the TD keratinocytes is remarkably similar to that of the interfollicular epidermal keratinocytes, it also shares certain molecular signatures with the hair follicle keratinocytes. Our study highlights that the TD keratinocytes in the adult skin have molecular characteristics of keratinocytes of diverse epidermal lineages.

Eccrine sweat glands are indispensable for human thermoregulation and, similar to other mammalian skin appendages, form from multipotent epidermal progenitors. Limited understanding of how epidermal progenitors specialize to form these vital organs has precluded therapeutic efforts toward their regeneration. Herein, we applied single-nucleus transcriptomics to compare the expression content of wild-type, eccrine-forming mouse skin to that of mice harboring a skin-specific disruption of Engrailed 1 (En1), a transcription factor that promotes eccrine gland formation in humans and mice. We identify two concurrent but disproportionate epidermal transcriptomes in the early eccrine anlagen: one that is shared with hair follicles and one that is En1 dependent and eccrine specific. We demonstrate that eccrine development requires the induction of a dermal niche proximal to each developing gland in humans and mice. Our study defines the signatures of eccrine identity and uncovers the eccrine dermal niche, setting the stage for targeted regeneration and comprehensive skin repair.

Exosomes are lipid bilayer vesicles, 30-200 nm in diameter, that are produced by cells and play essential roles in cell-cell communication. Exosomes have been studied in several medical fields including dermatology. Hair loss, a major disorder that affects people and sometimes causes mental stress, urgently requires more effective treatment. Because the growth and cycling of hair follicles are governed by interactions between hair follicle stem cells (HFSCs) and dermal papilla cells (DPCs), a better understanding of the mechanisms responsible for hair growth and cycling through exosomes may provide new insights into novel treatments for hair loss. In this review, we focused on the comprehensive knowledge and recent studies on exosomes in the field of hair development and regeneration. We classified exosomes of several cellular origins for the treatment of hair loss. Exosomes and their components, such as microRNAs, are promising drugs for effective hair loss treatment.

The objectives of the present research were to ascertain the relationship of Leucine-Rich Repeat-Containing G-Protein Coupled Receptors 6 (LGR6) methylation and transcript levels with ankylosing spondylitis (AS).

Targeted bisulfite sequencing was applied to analyze LGR6 DNA methylation in 81 AS cases and 81 controls. Besides, the LGR6 transcription level of peripheral blood mononuclear cells (PBMCs) from 70 AS cases and 64 controls was measured utilizing quantitative real-time transcription-polymerase chain reaction (qRT-PCR).

The study detected the methylation levels of 43 sites in two CpG (cytosine-guanine dinucleotide) islands of LGR6 and found that LGR6 were significantly hypomethylated in AS patients (LGR6_1: P = 0.002; LGR6_2: P < 0.001). LGR6 transcript level was obviously reduced in AS (P = 0.001) and was positively related to DNA methylation level (CpG-1: P = 0.010; CpG-2: P = 0.007). Besides, the Receiver operating characteristic curve (ROC) exhibited good diagnostic performance of LGR6 methylation level (AUC = 0.676, 95% CI = 0.594-0.758, P < 0.001). Further subgroup analysis revealed that gender may affect the LGR6_1 methylation pattern.

The present study revealed that LGR6 DNA methylation dysregulation may be involved in the pathogenesis of AS from an epigenetic perspective for the first time, with the aim of providing new directions for biomarker identification and treatment development for AS patients.

As a population of homogeneous cells with both self-renewal and differentiation potential, stem cell pools are highly compartmentalized and contain distinct subsets that exhibit stable but limited heterogeneity during homeostasis. However, their striking plasticity is showcased under natural or artificial stress, such as injury, transplantation, cancer, and aging, leading to changes in their phenotype, constitution, metabolism, and function. The complex and diverse network of cell-extrinsic niches and signaling pathways, together with cell-intrinsic genetic and epigenetic regulators, tightly regulate both the heterogeneity during homeostasis and the plasticity under perturbation. Manipulating these factors offers better control of stem cell behavior and a potential revolution in the current state of regenerative medicine. However, disruptions of normal regulation by genetic mutation or excessive plasticity acquisition may contribute to the formation of tumors. By harnessing innovative techniques that enhance our understanding of stem cell heterogeneity and employing novel approaches to maximize the utilization of stem cell plasticity, stem cell therapy holds immense promise for revolutionizing the future of medicine.

The Wnt β-catenin signaling pathway is a highly conserved mechanism that plays a critical role from embryonic development and adult stem cell homeostasis. However, dysregulation of the Wnt pathway has been implicated in various diseases, including cancer. Therefore, multiple layers of regulatory mechanisms tightly control the activation and suppression of the Wnt signal. The E3 ubiquitin ligases RNF43 and ZNRF3, which are known negative regulators of the Wnt pathway, are critical component of Wnt signaling regulation. These E3 ubiquitin ligases control Wnt signaling by targeting the Wnt receptor Frizzled to induce ubiquitination-mediated endo-lysosomal degradation, thus controlling the activation of the Wnt signaling pathway. We also discuss the regulatory mechanisms, interactors, and evolution of RNF43 and ZNRF3. This review article summarizes recent findings on RNF43 and ZNRF3 and their potential implications for the development of therapeutic strategies to target the Wnt signaling pathway in various diseases, including cancer.

Since adult stem cells are responsible for replenishing tissues throughout life, it is vital to understand how failure to undergo apoptosis can dictate stem cell behavior both intrinsically and non-autonomously. Here, we report that depletion of pro-apoptotic Bax protein bestows hair follicle stem cells with the capacity to eliminate viable neighboring cells by sequestration of TNFα in their membrane. This in turn induces apoptosis in "loser" cells in a contact-dependent manner. Examining the underlying mechanism, we find that Bax loss-of-function competitive phenotype is mediated by the intrinsic activation of NFκB. Notably, winner stem cells differentially respond to TNFα, owing to their elevated expression of TNFR2. Finally, we report that in vivo depletion of Bax results in an increased stem cell pool, accelerating wound-repair and de novo hair follicle regeneration. Collectively, we establish a mechanism of mammalian cell competition, which can have broad therapeutic implications for tissue regeneration and tumorigenesis.

Tissue interactions are essential for guiding organ development and regeneration. Hair follicle formation relies on inductive signalling between two tissues, the embryonic surface epithelium and the adjacent mesenchyme. Although previous research has highlighted the hair-inducing potential of the mesenchymal component of the hair follicle - the dermal papilla and its precursor, the dermal condensate - the source and nature of the primary inductive signal before dermal condensate formation have remained elusive. Here, we performed epithelial-mesenchymal tissue recombination experiments using hair-forming back skin and glabrous plantar skin from mouse embryos to unveil that the back skin mesenchyme is inductive even before dermal condensate formation. Moreover, the naïve, unpatterned mesenchyme was sufficient to trigger hair follicle formation even in the oral epithelium. Building on previous knowledge, we explored the hair-inductive ability of the Wnt agonist R-spondin 1 and a Bmp receptor inhibitor in embryonic skin explants. Although R-spondin 1 instigated precocious placode-specific transcriptional responses, it was insufficient for hair follicle induction, either alone or in combination with Bmp receptor inhibition. Our findings pave the way for identifying the hair follicle-inducing cue.

Topical defensins have recently gained attention as agents to improve skin composition. This study aimed to aggregate and synthesize studies in the literature assessing the effects of topical defensins on skin composition in the context of its ability to combat signs of aging.