The effect of platelet-rich plasma on the neovascularization of surgically created equine superficial digital flexor tendon lesions

The repair process of tendon injuries, which are common in both human and equine athletes, is slow and the quality of the repair tissue is often inferior to the original tendon tissue, which frequently leads to re-injury. The relatively poor vascularization of tendons is considered to be one of the reasons for their limited healing potential. Recently, platelet-rich plasma (PRP), an autologous concentrate of platelets, rich in growth factors, has been shown to enhance the repair process of injured tendons. This effect has been ascribed to the high levels of growth factors in PRP, several of which are known to be involved in tendon repair. Among many other growth factors, the vascular endothelial growth factor, a powerful stimulator of angiogenesis, is abundantly present in PRP, suggesting that enhancement of neovascularization might be one of the working mechanisms. In this study, the effect of PRP on neovascularization was studied in experimentally induced tendon injuries using color Doppler ultrasonography and immunological staining of Factor VIII. PRP induced significantly more neovascularization than the placebo treatment until at least 23 weeks after treatment, as detected by both Doppler ultrasonography and Factor VIII staining. Neovascularization might be one of the explanations for the long-lasting effect of a single intratendinous treatment with PRP.