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

Table 4  In vivo platelet-rich plasma and muscle studies - summaries

Ref.	PRP preparation	Cytology findings	Study design	Outcomes measured	Results
Borrione et al[9], 2014	Whole blood collected in sodium citrate spun twice first at 220 × g for 15 min and again at 1270 × g for 5 min. Pellet re-suspended and activated with 10% CaCl2 (20 mL)	Not reported	102 Wistar male adult rats had flexor sublimis muscle surgically cut and PRP immediately applied	Macroscopic evaluation, H&E changes, Leukocyte infiltration & WBC numbers, MyoD protein expression, gene expression of CD3, CD8, CD19, and CD 68, Myo D. Outcomes measured up to 7 d	PRP led to greater & earlier leukocyte infiltration (lymphocytes & monocytes) than control. PRP increased gene & MyoD protein expression
Cunha et al[2], 2014	Whole blood spun at 220 × g for 20 min at 20 °C. PRP combined with thrombin and activated with 10% CaCl2 to yield PRP gel	Not reported	20 Wistar adult male rats had vastus lateralis surgically injured. Rats randomized to treatment with and without PRP +/- exercise training	Serum lactate levels, histological analysis measuring type 1 and type 3 collagen at 3 wk after treatment	Exercise training + PRP led to greatest increase in type 3 collagen and decrease in type 1 collagen
Delos et al[3], 2014	Whole blood collected in citrate phosphate dextrose. Spun at 1000 × g for 15 min at 4 °C. Second spin under same conditions. 100 µL of PRP used for treatment	PRP – Plt count equal to 2.19 × 106 ± 2.69 × 105 µL, WBC 22.54 × 103/µL	46 male Lewis rats underwent single blunt injury to gastrocnemius muscle. Four treatment groups: Immediate PRP, Immediate saline, PRP day 1, PRP day 3	Histology, biomechanical testing (maximal isometric torque), amount of fibrosis (Masson’s trichome staining), IHC. Outcomes measured at day 15	PRP did not demonstrate any effects on outcomes including isometric torque strength, amount of fibrosis, or inflammation
Denapoli et al[15], 2016	Pure leukocyte poor PRP: Blood in 70% EDTA HEPES buffer spun at 300 × g/15 min and again 1000 × g/10 min. Platelets separated and 70% EDTA HEPES buffer added	Pure PRP- Plt count equal to 1090.0 ± 70.7 × 103/µL	30 male 10– to 12-week-old C57BL/6 wild-type mice had surgically induced blunt contusion to tibialis anterior muscle. 10 µL, pure PRP was injected at day 1, 4 and 7 d after injury. Outcomes measured at day 30	Histologic assessment of repair. Treadmill exercise for functional performance. Other PRP preparations were created and cytology & growth factor concentrations were compared between PRP groups. However, only pure leukocyte poor PRP was used in muscle contusion model	The day 7 PRP treated group had best functional performance and the most peripheral nucleated fibers on histology suggesting fastest recovery and decreased fibrosis
Dimauro et al[16], 2014	Whole blood collected in citrate phosphate dextrose. Spun at 220 × g/15 min, and again at 1270 × g/5 min. Pellet re-suspended and activated with 10% CaCl2	Averages not reported. However, PRP reported to have platelet concentration > 1250000 and WBC, neutrophils < baseline	40 Wistar male adult rats had surgical lesion made in flexor sublimus muscle. 20 rats immediately treated with PRP, other 20 untreated. Additional 10 rats anesthetized with lesion made. Outcomes measured at days 2 and 5	Gene expression of many intrinsic factors in regenerating skeletal muscle (e.g. cytokines, MRFs, growth factors), protein expression of MyoD1, Pax7, myogenin, stress response proteins, and apoptotic markers	PRP increased early expression of pro-inflammatory cytokines (e.g., TGF-β1, IL-1β. Increased expression of MRFs. No effect on VEGF. Increased ERK activation & IGF-1Eb expression
Gigante et al[23], 2012	Whole blood collected in citrate phosphate dextrose (1:5). Spun at 1000 × g/6 min. Supernatant activated with CaCl2 and then spun at 1450 × g/15 min	Not reported	Surgically induced bilateral lesions of longissimus dorsi muscle and subsequently treated with PRP matrix evaluated over 60 d	Histologic evaluation of neovascularization, muscle regeneration, fibrosis and inflammation. IMHC of myoD and Myogenin	Improved fibrosis, muscular regeneration and neovascularization. Increased expression of Myogenin
Hammond et al[6], 2009	Femoral/renal veins or intracardiac punctures on five adult male Sprague-Dawley rats (20 mL blood/each). PRP separated from whole blood (Symphony II Platelet Concentration System, DePuy). PPP used for control. Remaining PRP subjected to high frequency ultrasound (10 s). 100 µL used for injections	Not reported	72 adult male Sprague-Dawley rats had strain of tibialis anterior induced with superimposed lengthening contraction onto maximal isometric contraction using either a single repetition or multiple repetitions. Outcomes measured at days 3, 5, 7, 14, 21	Maximal isometric contraction and torque, Isometric torque, histology, and gene and protein expression of MyoD and myogenin, PDGF and IGF-1 concentrations in PRP and PPP	PRP had higher concentrations of PDGF and IGF-1. In single repetition group, PRP resulted in increased force only at day 3. No difference in return to function. For multiple repetitions, PRP improved force at multiple time points and faster return to function
Li et al[17], 2016	PRP isolated from three rats and mixed in citrate-phosphate-dextrose isolated as above. Centrifuged at 160 × g/20 min. Supernatant transferred, centrifuged 400 × g/15 min. Pellet re-suspended with remaining plasma to yield PRP	PRP - Plt count equal to 6.44 ± 0.64 × 106/µL, WBC 22.37 ± 2.25 × 103/µL	16 male Fisher rats injured with cardiotoxin injection into tibialis anterior. Four treatments: (1) Control, (2) 50 µL PRP, (3) 50 µL PRP neutralized with 280 ng/µL TGF-β1 antibody, (4) 50 µL PRP neutralized with 1400 ng/µL TGF-β1 antibody. Outcomes at 7, 14 d	Assessed muscle regeneration and collagen deposition with histology. IMHC for CD31, Alpha-SMA, Pax-7, CD68, transglutaminase-2, dystrophin to determine differentiation and mechanism for repair	PRP accelerated muscle regeneration (increased regenerating myofibers), increased angiogenesis (increased MVD-CD31, MVD-α-SMA) TGF-β1 neutralization of PRP reduced collagen deposition, PRP reduced macrophages and inflammatory response
Martins et al[19], 2016	Whole blood centrifuged 180 × g/10 min. Supernatant transferred and centrifuged at 1000 × g/10 min. Pellet re-suspended and activated with 10% calcium gluconate	PRP - Plt count equal to 4904/µL	Gastrocnemius Muscle contusion model studying the effect of PRP and reactive oxygen species over a 7-d treatment course	Reactive species byproducts (TBARS, DCFHRS), mitochondria function (MTT assay), antioxidant enzyme activities (GSH, CAT, SOD) and myeloperoxidase	PRP reduces oxidative damage and MPO enzyme, increases antioxidants
Ozaki et al[21], 2016	4mL blood from cardiac puncture combined with 0.2 mL 10% sodium citrate. Centrifuged 200 × g/15 min. Top two fractions isolated and centrifuged, at 500 × g/10 min	PRP- Plt count equal to 4999 × 103/µL	Thirty-five male Wistar rats in 5 groups (n = 7): control (C), control lesion (CL), lesion treated with low-level laser therapy (LLt), lesion treated with PRP (LP), and lesion treated with both techniques (LLtP). Muscle injury by stretching gastrocnemius muscle. PRP (100 μL) injected into distal third of tibia to be applied to gastrocnemius muscle belly	Histology for morphology, inflammatory infiltrate, oxidative stress using Raman scattering spectroscopy, collagen content	CL group had increased macrophages and oxidative stress. LP group had decreased inflammation, increased tissue organization, and increased presence of regeneration cells
Pinheiro et al[24], 2016	Intracardiac puncture -3 mL blood/each rat centrifuged 1200 × g/15 min to yield three layers. Isolated PRP/RBC layer, centrifuged 1min. PRP (0.2 mL) separated and activated with calcium gluconate (0.01 mL) to yield PRP gel	Cytology not provided	Ultrasound study following PRP therapy in a gastrocnemius muscle injury model	Pennation angle, Muscle thickness, Mean pixel intensity, claudication scores	No significant difference found
Quarteiro et al[8], 2015	Four blood samples (8 mL/rat) from five rats mixed with anticoagulant Samples centrifuged and plasma separated. Plasma centrifuged and supernatant removed leaving PRP (1mL)	PRP - Plt count equal to 1019 ± 182.25 × 103/µL	Gastrocnemius muscle injury model	Histologic assessment	No difference in collagen content at 21 days. Inflammatory process observed in groups treated with PRP
Terada et al[20], 2013	Blood obtained from intracardiac puncture. Centrifuged 800 rpm/ 15 min at 25 °C. Three PRP preparations created (rPRP, gPRP and hPRP). All three activated with 10% CaCl2 and bovine thrombin (300 IU, Fibriquik Thrombin, BioMerieux Inc., Durham, NC, United States)	PRP - Plt count equal to 208.0 ± 25.8 × 103/mL	PRP +/- Losartan in a tibialis anterior contusion model	IMHC (VEGF, CD31, Follistatin), Isometric Torque, Histological assessment (fibrosis and number of regenerating myofibers)	PRP in conjunction with losartan improved muscle recovery, reduced fibrosis. increased angiogenesis. PRP alone had similar but lesser effects
Contreras-Muñoz et al[22], 2017	3.5-4 mL whole blood obtained from intracardiac puncture, added to citrate phosphate dextrose, spun at 400 × g for 10 min. Plasma fraction extracted and spun at 800 g for 10 min	PRP - Plt count equal to 3.73 ± 0.25 × 106 platelets/ µL; WBC - 0.004 ± 0.0054 × 103 /µL	40 rats assigned to five groups: Injured rats (medial gastrocnemius injury) + single PRP injection (PRP group), daily exercise training (Exer group), or combination of single PRP injection and daily exercise training (PRP-Exer group). Untreated and intramuscular saline–injected animals were used as controls	Histologic and immunofluorescence analysis, force assessment, cross-sectional area of newly formed muscle fibers, dMHC and presence of collagen 1 in scar formation	18%, 20%, and 30% strength increase in PRP, PRP-Exer, and Exer groups. 1.5-, 2-, 2.5-fold increase in myofiber cross sectional area in PRP, PRP-Exer, and Exer groups. 20%, 34%, 41% of reduction scar formation in PRP, PRP-Exer, and Exer groups. 35% and 47% decrease in percentage of dMHC-positive regenerating fibers in PRP-Exer and Exer groups
Garcia et al[25], 2017	Cardiac puncture (4 mL) combined with 10% sodium citrate, spun at 200 × g for 15 min. Top layer + buffy coat extracted, spun at 500 × g for 10 minf	PRP – Plt count equal to 4998.676 × 103 platelets/µL	35 rats assigned to five groups: Control (C), Injury (soleus) Control (IC), injury PRP (IP), injury LLLT (ILT) and injury LLLT and PRP (ILTP)	Histologic assessment of muscle fiber morphology, collagen, inflammatory infiltrate	Intense polymorphic fibers (> 75%) in ILTP and IP groups. Lowest inflammatory infiltrate (< 20%) in ILTP compared to other injured groups. Significantly more focused collagen in ILT compared to IP and C groups