Published online Jul 18, 2019. doi: 10.5312/wjo.v10.i7.278
Peer-review started: February 15, 2019
First decision: April 16, 2019
Revised: May 10, 2019
Accepted: June 25, 2019
Article in press: June 25, 2019
Published online: July 18, 2019
Platelet-rich plasma (PRP) is a biological adjunct derived from autologous blood, which is thought to aid the healing of various bone, ligament, cartilage, and muscle injuries. PRP is composed of various cytokines, growth factors, and concentrations of leukocytes and platelets. PRP is often used clinically to expedite healing as a non-operative treatment or operative adjunct. However, studies have reported mixed effects of PRP, and clinicians continue to employ this adjunct despite little understanding of its mechanism of action.
The main topics of the current study are (1) The various mechanisms of PRP action at the molecular and tissue levels for muscle injuries; and (2) Reporting patterns of PRP preparations in these studies. The current study seeks to clarify the underlying mechanisms of action of PRP, in terms of its ability to induce cellular changes and changes at the histologic and tissue levels, which are not well-described.
The main objective of the current study is to clarify the effects of PRP at the cellular and tissue levels through synthesizing its mechanisms of action from available basic science studies on muscle injuries. A secondary objective that was realized was that it is important to understand PRP preparations across multiple studies to allow for the standardization of study protocols and better comparisons.
A systematic review of basic science studies from the PubMed/MEDLINE and EMBASE databases was conducted, as these studies would allow for the best understanding of the mechanism of action of PRP at the cellular and tissue levels. Using a custom pre-determined spreadsheet of a wide variety of growth factors, cytokines, and other molecular markers, each study was analyzed, and these variables were subsequently extracted. The PRP preparation methods were also extracted.
A total of 23 articles were identified. PRP conferred multiple beneficial effects on muscles both in vitro and in vivo through the upregulation of genes beneficial to healing and muscle regeneration, increasing cellular proliferation and differentiation, and producing superior tissue quality and biomechanical properties in comparison to placebo. However, this study also identified the lack of PRP cytology reporting among these studies, of which only one study reported a full cytology.
PRP confers multiple beneficial effects at the basic science level in models of muscle injury compared to placebo through changes at the cellular level, which include gene expression, growth factor and cytokine concentrations, increased angiogenesis, and cellular differentiation and proliferation. PRP also mediates increased muscle regeneration at the gross level, and superior histologic quality when compared to placebo in a few studies. There was significant variability in both PRP preparation and reporting among the included studies.
This study highlights the importance of understanding processes at the basic science level in order to provide better insight into clinical practice. Future research is needed to determine the optimal cytology, dosing, timing, and delivery method of PRP for muscle injuries. Higher level randomized studies will need to be performed in order to determine these factors. Furthermore, it will be essential for future studies to use standardized protocols, such that outcomes and practices with PRP become reproducible.