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

Table 6  In vivo and in vitro muscle studies

Ref.	PRP preparation	Cytology findings	Study design	Outcomes measured	Results
Takase et al[27], 2017 (In vitro arm)	Whole blood extracted from male volunteers, combined with 12 mL 3.13% sodium citrate. Centrifuged 2400 rpm/10 min, again at 3600 rpm/15 min for 10 mL PRP and PPP. PRP activated by freezing at -80 °C; centrifuged again at 10000 rpm/10 min	PRP – Plt count equal to 7.2 × 105 - 9.4 × 105 platelets/mL	Murine myogenic cell line (C2C12 cells) subjected to PRP treatment. Cell morphology assessed by phase microscopy. Myotube quantification assessed by immunocytostaining. Cell proliferation assessed using water-soluble tetrazolium salt (WST) assay using a cell counting Kit-8. Oil Red-O staining used to identify lipid droplets and accumulation determined by phase contrast microscopy. rt-PCR used to quantify myogenic and adipogenic markers	Cell proliferation, myogenic differentiation (Pax7, myogenin), adipogenic differentiation [PPARγ, CCAAT/enhancer binding protein (C/EBPα)]	PRP inhibited myotube formation, decreased average area of myotubes, induced myogenic proliferation compared to myogenic group. Number of lipid droplets in PRP-adipogenic group was lower than adipogenic group. PRP suppressed expression of Pax7, myogenin, PPARγ and C/ERPα
(In vivo arm)	8 mL blood retrieved from one, 3-mo old, Sprague-Dawley rat, combined with 2 mL 3.13% sodium citrate Centrifuged at 1500 rpm for 10 min. Second spin at 3000 rpm for 10 min yielded PRP (1mL) and PPP. PRP frozen at -80 °C until needed	PRP - Plt count equal to 1.6 × 109 platelets/mL	PRP injection into subacromial space of five rat rotator cuff tear models Infraspinatus used for histology. Muscles cryosectioned, fixed with 4% PFA, stained with Oil Red-O and hematoxylin. Supraspinatus used for biochemical assays. rt-PCR to quantify genes	Oil Red-O positive lipid droplet formation, adipogenic differentiation [PPARγ, CCAAT/enhancer binding protein (C/EBPα)], and muscular atrophy [(Muscle RING Finger Protein-1 (MuRF-1) and atrogin-1]	Rotator tear groups had increased MuRF-1, atrogin-1, PPARγ and C/EBPα PRP decreased lipid droplet presence. PRP decreased expression of PPARγ and C/EBPα
Li et al[26], 2013 (In vivo arm)	Human whole blood from Central Blood Bank, Pittsburgh, PA, United States centrifuged 3000 g/ 10 min. Fraction of PRP poor supernatant transferred, PRP pellet re-suspended. PRP concentration measured by hemocytometer, activated with human thrombin (1U/mL). PRP releasate separated from cellular debris by centrifugation 3000 × g/30 min. PRP releasate stored at -80 °C	Cytology not provided	Gastrocnemius of mdx-SCID mice damaged with cardiotoxin and treated with hMDPCs treated with PRP	Histological assessment of as the number of hMHC-I-positive myofibers/1 × 105 injected cells	PRP maintained hMDPCs growth and regeneration of myofibers
(In vitro arm)	Centrifuged at 3000 × g for 10 min at RT. PRP activated with one unit per mL human thrombin. After activation, the PRP releasate obtained by centrifugation at 3000 × g for 30 min	PRP – Plt count equal to 2000/µL	hMDPCs isolated from donors cultured in PRP versus 20% FBS as a control. Assessed Proliferation, role of exogenous growth factors, gene expression, and cell differentiation	Proliferation, growth factor PDGF, VEGF, TGF-B1 RT-PCR for expression profile of stem cell markers and differentiation	PRP increased cell proliferation. PRP with anti TGF-B1 and anti VEGF did not. PRP increased the expression of BMPR1-A, BMPR1-B, BMPR2, ALDH, SOX2, Aggrecan, and Desmin. No difference in differentiation capacity

PRP: Platelet-rich plasma.