Platelet-rich plasma for muscle injuries: A systematic review of the basic science literature

Table 1  In vitro PRP and muscle studies – summaries

Ref.	PRP preparation	Cytology findings	Study design	Outcomes measured	Results
Kelc et al[11], 2015	Whole blood in citrate dextrose anticoagulant spun 10 min at 1500 rpm. Three PRP solutions prepared at differing “growth factor concentrations” by diluting with DMEM (5%, 10% and 20%)	Not reported	Human CD56+ Myoblast cells cultured and treated with PRP (5,10,20%) and/or decorin for 4 d of treatment	Cell viability, proliferation. Myogenic differentiation, TGF-β and other fibrotic cytokine expression, MRF	PRP increased myoblast proliferation, viability, and differentiation. PRP supported myogenic shift in differentiation. Decreased TGF-β and other fibrotic cytokine expression and increased expression of MRFs
Mazzocca et al[7], 2012	PRP-LP (low platelet) – single 1500 rpm spin for 5 min. Plasma layer isolated. PRP-DS (High Platelet, high WBC) – double spin first at 1500 rpm for 5 min then again at 6300 rpm for 20 min. PRP-HP (High platelet, low WBC) – single 3200 rpm spin for 15 min	PRP-LP – Platelet (Plt) count equal to 382.0 ± 111.6 103/µL; RBC 0; WBC 0.6 ± 0.3 103/µL. PRP-HP – Plt count equal to 940.1 ± 425.8 × 103/µL; RBC 1.5± 2.5 × 103/µL; WBC 17.0 ± 5.2 × 103/µL. PRP-DS - Plt count equal to 472.6 ± 224.2 × 103/µL; RBC 0.0 ± 0.1 × 103/µL, WBC 1.5 ± 0.6 × 103/µL	Human muscles isolated from lattisimus dorsi transfer procedures cultured for 2 wk to allow for myocyte outgrowth. Myocytes treated with three PRP treatments for 96 h	Cell proliferation, growth factor concentrations (EGF, FGF2, HGF, IGF-1, PDGF, TGF-β, VEGF)	PRP-DS and PRP-LP increased cell proliferation. PRP-LP increased concentration of all growth factors except HGF, FGF, & EGF. PRP-DS increased concentration of all growth factors except FGF & HGF. PRP-HP increased concentration of all growth factors except FGF
McClure et al[1], 2016	Prepared with commercial SmartPReP® 2 system. Frozen thaw protocol to lyse platelets. Product then frozen and lyophilized to create dry PRGF	Not reported	C2C12 murine myoblasts cultured and expanded and treated with PRGF at various concentrations for 7 d	Proliferation (MTS proliferation assay), myogenic regulatory factor (MRFs) concentration, cell differentiation, skeletal muscle cell signaling, scaffold fiber alignment	PRP dose dependently increased myoblast cell proliferation, differentiation, skeletal muscle cell signaling, and concentration of MRFs (MyoD, MyoG)
Miroshnychenko et al[12], 2017	50 mL whole blood from seven volunteers processed with Pure PRP kit (EmCyte Corp) into: (1) Single spin leukocyte poor PRP; (2) Single spin mod-PRP with TGF-β1 and MSTN depletion; (3) Dual spin PRP; (4) Dual spin Mod-PRP; and (5) PPP. Second spin was 550 × g for 5 min and removed all platelets	PRP - Plt count equal to 879 ± 350.6 103/µL; WBC 1.8 ± 2.3 103/µL. PPP -Plt count equal to 9.9 ± 4.9 103/µL	Human skeletal muscle myoblast (HSMM) cell culture (CC-2580, Lanza) used to produce positive control (treated with 2% horse serum in myogenic DMEM/F-12 medium) and negative control (treated with 10% FBS in SkBM-2 basal medium). HSMM treated at varying concentrations with plasma formulations	Cell proliferation, protein production, myoblast differentiation, gene expression (MYH, MYH2, MSTN, MEF2C)	Single spin PRP & single spin Mod-PRP greatest influence on myoblast proliferation, but did not promote myogenic differentiation or formulation of myotubules. PPP and double spin PRP had little effect on proliferation, but greatest effects on promotion of myogenic differentiation and myotubule formation. PPP had a dose-dependent effect (peaking at 4%) on increasing MYH expression
Tsai et al[13], 2017	Whole blood from Sprague-Dawley rats in acid citrate-dextrose, spun at 800 × g for 30mins. Plasma isolated and spun at 3000 × g for 20 min. 10% thrombin solution added and again centrifuged at 5500 × g for 15 min. Final release filtered by 0.22 μm ultra-filtration and frozen at -20 °C	Not reported	Skeletal muscle cells isolated from Sprague-Dawley rats cultured and treated with PRP releasate. MTT assay and Immunohistochemistry with ki-67 stain also used to determine cell proliferation. Western blot used to determine changes in protein expression. Flow cytometry used to evaluate cell-cycle progression	Cell proliferation, cell viability, protein expression (cyclin A2, cyclin B1, cdk1, cdk2, PCNA)	PRP increased skeletal muscle cell viability & cell proliferation by shifting cells from the G1 phase to the S1 phase and G2/M phases. PRP increased protein expression of cyclin A2, cyclin B1, cdk1, cdk2, PCNA
Tsai et al[14], 2017	Whole blood from Sprague-Dawley rats in acid citrate-dextrose, spun at 800 × g for 30 min. Plasma isolated and spun at 3000 × g for 20 min. 10% thrombin solution added and again centrifuged at 5500 × g for 15 min. Final release filtered by 0.22 μm ultra-filtration and frozen at -20 °C	Not reported	Myocyte migration evaluated by trans-well filter migration assay and electric cell-substrate impedance sensing. Myocyte spreading evaluated microscopically. Formation of filamentous actin (F-actin) cytoskeleton assessed by immunofluorescence staining. Protein expressions of paxillin and focal adhesion kinase (FAK) assessed by Western blot analysis	Myocyte migration, spreading, FAK and Paxillin expression, F-actin formation	PRP dose-dependently promoted (1) Myocyte migration, (2) Spreading, (3) Paxillin and FAK expression, (4) F-actin formation, and (5) Wound healing

PRP: Platelet-rich plasma.