Platelet-rich plasma does not reduce skeletal muscle fibrosis after distraction osteogenesis

Fibrosis and Sports Injuries: Concept and Implications: The GESMUTE-SETRADE Consensus Statement

Background

Musculoskeletal fibrosis can be frequently observed in the scope of sports medicine; however, there is no consensus regarding its definition, nor do we have substantial knowledge regarding its epidemiology or best therapeutic alternatives.

Purpose

The GESMUTE (Group for the Study of the Muscle Tendon System) Epidemiology Group, integrated into SETRADE (The Spanish Society for Sports Traumatology) propose a definition for musculoskeletal fibrosis within the field of physical exercise.

Study Design

Consensus statement.

Methods

A bibliographic review of the existing scientific evidence and consensus was developed by the authors on the definition of fibrosis in the field of sport.

Results

Our working group proposed the definition of fibrosis as an abnormal accumulation of extracellular matrix, usually with regards to an injury complication, showing various clinical findings affecting muscles, tendons, ligaments, articular capsules and nerves which, in turn, mars the recovery process, causing symptoms and finally leading to relapses.

Conclusion

Fibrosis in sport may be considered as an abnormal accumulation of extracellular matrix, usually related to complications of an injury, showing a wide range of clinical symptomatology, affecting muscles, tendons, ligaments, articular capsules, and nerves.

The Biological Use of Platelet-Rich Plasma in Skeletal Muscle Injury and Repair

Platelet-rich plasma (PRP) is a blood product that contains several growth factors and active proteins. PRP is thought to be used autologously to assist in the repair of injured tissues as well as to treat pain at the site of injury. The mechanism behind PRP in regenerative medicine has been well investigated and includes the identification and concentration of released growth factors and exosomes. The benefits of PRP have been highly recommended and are used widely in orthopaedics and sports medicine, including repair of injured skeletal muscle. This current report summarizes some of the more recent studies in the use of PRP as it relates to muscle healing, in both the in vitro and clinical arenas.

Platelet-rich plasma (PRP) accelerates murine patellar tendon healing through enhancement of angiogenesis and collagen synthesis

PURPOSE

Although platelet-rich plasma (PRP) therapy has become an increasingly popular treatment for sports-related injuries, the molecular mechanisms of PRP on tissue healing process remain poorly understood. The aim of the present study was to develop an experimental method quantifying the efficacy of PRP with murine patellar tendon injury model, leading to future elucidation of the mechanisms of PRP on healing processes.

METHODS

Full-thickness defects were created in the central third of the murine patellar tendon. The prepared allogenic PRP gel was applied on the defect of the patellar tendon (PRP group), while the remaining mice served as the untreated control group. Mice were sacrificed at 2, 4, 6, 8, and 10 weeks after the operation, with histological sections obtained in each time point (n = 4 / time point / group). Semi-quantitative histological evaluation was performed in accordance with the Bonar score. The variables included in this scoring system were cell morphology, ground substance, collagen arrangement, and vascularity, with higher grades indicating worse tendon structures. In addition, the ratio of the collagen fibers to the entire tendon tissue (FT ratio) was measured using KS400 software as a quantitative histological evaluation.

RESULTS

The total Bonar score in the PRP group was significantly lower than in control group. With regard to the variables in the Bonar score, the vascularity score was significantly higher in the PRP group at 2 and 4 weeks, while the collagen arrangement score was significantly lower in the PRP group at 8 weeks. Based on a quantitative evaluation, the recovery speed of the patellar tendon determined by FT ratio was significantly faster in the PRP group than in the control group at 6 and 8 weeks.

CONCLUSIONS

We have developed an experimental method for histological and quantitative evaluation of the effects of PRP on tissue healing using murine patellar tendon injury model. The results of this study suggest that the local application of PRP could enhance the tissue-healing process both directly through action on localized cells and indirectly through the recruitment of reparative cells through the blood flow. Further investigations will be needed to confirm the mechanisms of PRP in tissue-healing processes with the development of this experimental model.

Revisiting the Regenerative Therapeutic Advances Towards Erectile Dysfunction

Erectile dysfunction (ED) is an inability to attain or maintain adequate penile erection for successful vaginal intercourse, leading to sexual and relationship dissatisfaction. To combat ED, various surgical and non-surgical approaches have been developed in the past to restore erectile functions. These therapeutic interventions exhibit significant impact in providing relief to patients; however, due to their associated adverse effects and lack of long-term efficacy, newer modalities such as regenerative therapeutics have gained attention due to their safe and prolonged efficacy. Stem cells and platelet-derived biomaterials contained in platelet-rich plasma (PRP) are thriving as some of the major therapeutic regenerative agents. In recent years, various preclinical and clinical studies have evaluated the individual, as well as combined of stem cells and PRP to restore erectile function. Being rich in growth factors, chemokines, and angiogenic factors, both stem cells and PRP play a crucial role in regenerating nerve cells, myelination of axons, homing and migration of progenitor cells, and anti-fibrosis and anti-apoptosis of damaged cavernous nerve in corporal tissues. Further, platelet-derived biomaterials have been proven to be a biological supplement for enhancing the proliferative and differentiation potential of stem cells towards neurogenic fate. Therefore, this article comprehensively analyzes the progresses of these regenerative therapies for ED.

Platelet-Rich Plasma Modulates Gap Junction Functionality and Connexin 43 and 26 Expression During TGF-β1-Induced Fibroblast to Myofibroblast Transition: Clues for Counteracting Fibrosis

Skeletal muscle repair/regeneration may benefit by Platelet-Rich Plasma (PRP) treatment owing to PRP pro-myogenic and anti-fibrotic effects. However, PRP anti-fibrotic action remains controversial. Here, we extended our previous researches on the inhibitory effects of PRP on in vitro transforming growth factor (TGF)-β1-induced differentiation of fibroblasts into myofibroblasts, the effector cells of fibrosis, focusing on gap junction (GJ) intercellular communication. The myofibroblastic phenotype was evaluated by cell shape analysis, confocal fluorescence microscopy and Western blotting analyses of α-smooth muscle actin and type-1 collagen expression, and electrophysiological recordings of resting membrane potential, resistance, and capacitance. PRP negatively regulated myofibroblast differentiation by modifying all the assessed parameters. Notably, myofibroblast pairs showed an increase of voltage-dependent GJ functionality paralleled by connexin (Cx) 43 expression increase. TGF-β1-treated cells, when exposed to a GJ blocker, or silenced for Cx43 expression, failed to differentiate towards myofibroblasts. Although a minority, myofibroblast pairs also showed not-voltage-dependent GJ currents and coherently Cx26 expression. PRP abolished the TGF-β1-induced voltage-dependent GJ current appearance while preventing Cx43 increase and promoting Cx26 expression. This study adds insights into molecular and functional mechanisms regulating fibroblast-myofibroblast transition and supports the anti-fibrotic potential of PRP, demonstrating the ability of this product to hamper myofibroblast generation targeting GJs.

Influence of Platelet-Rich and Platelet-Poor Plasma on Endogenous Mechanisms of Skeletal Muscle Repair/Regeneration

The morpho-functional recovery of injured skeletal muscle still represents an unmet need. None of the therapeutic options so far adopted have proved to be resolutive. A current scientific challenge remains the identification of effective strategies improving the endogenous skeletal muscle regenerative program. Indeed, skeletal muscle tissue possesses an intrinsic remarkable regenerative capacity in response to injury, mainly thanks to the activity of a population of resident muscle progenitors called satellite cells, largely influenced by the dynamic interplay established with different molecular and cellular components of the surrounding niche/microenvironment. Other myogenic non-satellite cells, residing within muscle or recruited via circulation may contribute to post-natal muscle regeneration. Unfortunately, in the case of extended damage the tissue repair may become aberrant, giving rise to a maladaptive fibrotic scar or adipose tissue infiltration, mainly due to dysregulated activity of different muscle interstitial cells. In this context, plasma preparations, including Platelet-Rich Plasma (PRP) and more recently Platelet-Poor Plasma (PPP), have shown advantages and promising therapeutic perspectives. This review focuses on the contribution of these blood-derived products on repair/regeneration of damaged skeletal muscle, paying particular attention to the potential cellular targets and molecular mechanisms through which these products may exert their beneficial effects.