Use of autologous platelet-rich plasma to treat muscle strain injuries

Abstract

Background: Standard nonoperative therapy for acute muscle strains usually involves short-term rest, ice, and nonsteroidal anti-inflammatory medications, but there is no clear consensus on how to accelerate recovery.

Hypothesis: Local delivery of platelet-rich plasma to injured muscles hastens recovery of function.

Study design: Controlled laboratory study.

Methods: In vivo, the tibialis anterior muscles of anesthetized Sprague-Dawley rats were injured by a single (large strain) lengthening contraction or multiple (small strain) lengthening contractions, both of which resulted in a significant injury. The tibialis anterior either was injected with platelet-rich plasma, was injected with platelet-poor plasma as a sham treatment, or received no treatment.

Results: Both injury protocols yielded a similar loss of force. The platelet-rich plasma only had a beneficial effect at 1 time point after the single contraction injury protocol. However, platelet-rich plasma had a beneficial effect at 2 time points after the multiple contraction injury protocol and resulted in a faster recovery time to full contractile function. The sham injections had no effect compared with no treatment.

Conclusion: Local delivery of platelet-rich plasma can shorten recovery time after a muscle strain injury in a small-animal model. Recovery of muscle from the high-repetition protocol has already been shown to require myogenesis, whereas recovery from a single strain does not. This difference in mechanism of recovery may explain why platelet-rich plasma was more effective in the high-repetition protocol, because platelet-rich plasma is rich in growth factors that can stimulate myogenesis.

Clinical relevance: Because autologous blood products are safe, platelet-rich plasma may be a useful product in clinical treatment of muscle injuries.

Conflict of interest statement

No potential conflict of interest declared.

Figures

Figure 1

Results of enzyme-linked immunosorbent (ELISA) assays to confirm that platelet-rich plasma (PRP) is enriched in myogenic growth factors PDGF and IDF-1. Both PRP and platelet-poor plasma (PPP) were separated and subjected to ELISAs to detect and to quantify the presence of growth factors, such as platelet-derived growth factor (PDGF, grey bar to left in A) and insulin growth factor-1 (IGF-1, grey bar to left in B), both known to stimulate myogenesis. In addition, we also assayed “conditioned” plasma (grey bars to right), as described in the methods. The PRP was clearly rich in the 2 tested growth factors, and was further enriched by conditioning. Results are shown compared to ELISA assays of platelet-poor plasma (PPP). * = P

Figure 2

Representative trace recordings of torque from the lengthening contractions. For both single and multiple repetitions, muscles were stimulated for 200 ms to induce a peak isometric contraction prior to lengthening by the foot plate. Maximal isometric torque (without lengthening) was measured before injury (not shown, but equal to the plateau of the isometric portion of the trace recordings, indicated by filled arrows). A: superimposed recordings from the multiple repetition protocol (a 60° arc of motion) showing the first (ECC 1), middle (ECC 15), and last (ECC 45) eccentric contractions. Note that even with injury, the eccentric torque is still relatively high compared to isometric torque (the peak isometric torque measured after injury is not shown, but is similar to the isometric portion of the last trace recording, indicated by open arrow) B: superimposed recordings of the single repetition protocol (ECC 1, a 90° arc of motion) and the isometric contraction to measure torque loss after injury (ISO-POST).

Figure 3

Maximal torque was measured in each animal before injury (CTL) and immediately after injury (D0), as well as at selected time points after injury (days 3, 5, 7, 14, and 21). “100%” represents peak torque before injury. The percentage of recovery for each animal was calculated and the mean is expressed as the “percent of maximal isometric torque” (out of 100%) at each time point. A: after a single repetition through a 90° arc of motion, there is a significant drop in torque and gradual recovery to full contractile function by day 7. PRP had a significant effect only on day 3 (n = 8 animals each group). B: after multiple repetitions through a 60° arc of motion, there is a significant loss of torque followed by a gradual recovery by day 21. PRP had a significant effect on days 7 and 14, by which time the injured muscle had returned to pre-injury level of strength (n = 8 animals each group). “No Rx” = injury only (no injections) * = P

Figure 4

Myogenesis after the multiple repetition injury. A: 2 µg of total RNA was isolated from frozen rat tibialis anterior muscle and reverse transcriptase polymerase chain reaction (RT-PCR) was performed at various time points after injury using primers for two different genes involved in muscle regeneration (myoD and myogenin), as well as a gene used as an internal control (GAPDH). The gel shows representative PCR products from muscles injected with PPP or PRP 7 days after injury. B: Densitometry of the bands was performed and the results quantified relative to expression of the total GAPDH expressed in a particular muscle sample, as described in the Materials and Methods section. Thus, the histogram shows the mRNA transcript levels of myoD and myogenin from muscles injected with PPP or PRP (n = 3). C: Muscle samples from the same time point (day 3) were homogenized and proteins separated by electrophoresis. Immunoblots confirmed the increase protein expression of myoD (38 kD) and myogenin (36 kD). * = P

Figure 5

Tibialis anterior muscles were harvested at various time points after injury. The micrograph (top) shows representative cross-sections of non-injured control muscle (CTL) and of injured muscle (INJ) 14 days after the multiple repetition injury, when some of the normally peripherally located nuclei (CTL) are seen in the middle of the fiber (INJ). These centrally nucleated fibers (CNFs) are a marker of muscle regeneration and the peak in CNFs occurred on day 14. The histogram (bottom) shows the percentage of fibers that had CNFs at this time point in the injured TA muscles injected with PPP (black bar) and PRP (grey bar). * = P