To understand the variable efficacy with platelet rich plasma (PRP) treatments for tendon injury, we determined the differential effects of proteinase-activated receptor (PAR)1- or PAR4-activated PRP (PAR1-PRP, PAR4-PRP) from humans on human patellar tendon stem/progenitor cells (TSCs) and tendon healing. We show that PAR1-PRP released VEGF, whereas PAR4-PRP released endostatin. Treatment of TSCs with PAR1-PRP increased collagen I expression and matrix metalloproteinase-1 (MMP-1), but cells treated with PAR4-PRP increased less collagen I and higher MMP-2 expression. The wound area treated with PAR4-PRP formed tendon-like tissues with well-organized collagen fibers and fewer blood vessels, while PAR1-PRP treatment resulted in the formation of blood vessels and unhealed tissues. These findings indicate that differential activation of PRP leads to different effects on TSCs and tendon healing. We suggest that based on acute or chronic type of tendon injury, selective activation of PRP should be applied in clinics in order to treat injured tendons successfully.

中文翻译：

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选择性激活的PRP对肌腱干/祖细胞和肌腱愈合产生不同的作用。

为了解富血小板血浆（PRP）治疗肌腱损伤的疗效，我们确定了人类蛋白酶激活受体（PAR）1或PAR4激活PRP（PAR1-PRP，PAR4-PRP）对人的不同作用tell腱干/祖细胞（TSC）和腱愈合。我们显示PAR1-PRP释放VEGF，而PAR4-PRP释放内皮抑素。用PAR1-PRP处理TSC可以增加胶原蛋白I的表达和基质金属蛋白酶-1（MMP-1），但是用PAR4-PRP处理的细胞可以减少胶原蛋白I的表达，并提高MMP-2的表达。PAR4-PRP处理的伤口区域形成了肌腱样组织，胶原纤维组织良好，血管较少，而PAR1-PRP处理导致血管和未愈合组织的形成。这些发现表明，PRP的不同激活导致对TSC和肌腱愈合的不同影响。我们建议基于急性或慢性类型的肌腱损伤，应在临床中应用选择性激活PRP才能成功治疗受伤的肌腱。