Platelet rich plasma intralesional injection as bedside therapy for tendinitis in athletic horse

ABSTRACT

Background: Tendinitis result in a considerable economic loss to the equine industry due to decreased performance, prolonged rehabilitation, recurrent injuries and early retirement. It is well known that damaged tendons have a low healing potential and old therapies often lead to mechanical side effect of a scar tissue with reduced functionality and high risks of re-injury. Regenerative therapies that induce the restoration of the tendon's normal structure and function, rather than formation of less functional scar tissue, decrease the risk of re-injury tissue repair. In particular, platelet rich plasma (PRP) therapy reproduce those processes of development in which there are spatial and temporal interactions between scaffold, growth factors and cell populations that lead to a normal structure and function of neo-formed tendon tissue. According to this knowledge, the aim of this study was to assess autologous PRP therapy as bedside procedure to treat equine tendon injuries. Materials, Methods & Results: Following a clinical and ultrasound examination, fifteen Thoroughbred horses affected by tendinitis of the superficial or deep digital flexor tendons were treated with intralesional injection of autologous PRP on-field preparation. On each horse blood samples were aseptically collected from the jugular vein into sterile tubes. Two sequential centrifugations of whole blood, added with Anticoagulant Citrate Dextrose Solution "A", were performed at 400 g for 10 min and at 620 g for 12 min, respectively, to obtain the PRP. After the PRP injection, horses were subjected to a standardized rehabilitation program that lasted about 6 months and an ultrasound checkup on the 50th day after the administration of PRP showed echographic aspect of the treated tendons comparable to healthy tendons. At the time of ultrasound checkup, all horses showed a marked clinical improvement. A month after completing the rehabilitation program the horses return to train and compete in 1200 m gallop competitions, on average once a month. In no case re-injury occurred within 12 months from the beginning of the therapy. Discussion: PRP treatment improves the regeneration of tissues with a low healing potential like tendons through increased levels of several growth factors including transforming growth factor-b (TGF-b), platelet derived growth factor (PDGF) and vascular endothelial growth factor (VEGF), that are released after platelet degranulation in the damage site and enhance tissue regeneration by stimulating cell proliferation. The effects of PRP therapy in equine tendinitis include also the enhanced gene expression of tendon matrix molecules, including cartilage oligomeric matrix protein (COMP), and the increased collagen type I/collagen type III ratio, with no concomitant increase in the catabolic molecule matrix metalloproteinase. There are many methods for sampling and preparing PRP test tubes, quadruple blood bags, apheresis, manual preparation or automatic preparation systems; but most of these methods require expensive and sophisticated technical equipment. Since treated horses showed neither local nor systemic side effect after the PRP administration, our study suggests that maintaining aseptic conditions PRP treatment is a minimally invasive and low cost therapy that is quite easy and safe to realize in the field to treat equine tendinitis. After a year follow-up all horses treated with the PRP were either performing at their previous workload and they were back in racing. None of them showed signs of re-injury.