The application of growth factors in the treatment of local cartilage defects as well as osteoarthritis appears promising; however, further research is needed at both the basic science and clinical levels before routine application.

Platelet-rich plasma (PRP) has generated substantial interest for tendon and ligament regeneration because of the high concentrations of growth factors in platelet a-granules. This study compared the temporal release of growth factors from bone marrow aspirate (BMA), PRP, and lyophilized platelet product (PP), and measured their effects on tendon and ligament gene expression. Blood and BMA were collected and processed to yield PRP and plasma. Flexor digitorum superficialis tendon (FDS) and suspensory ligament (SL) explants were cultured in 10% plasma in DMEM (control), BMA, PRP, or PP. TGF-b1 and PDGF-BB concentrations were determined at 0, 24, and 96 h of culture using ELISA. Quantitative RT-PCR for collagen types I and III (COL1A1, COL3A1), cartilage oligomeric matrix protein (COMP), decorin, and matrix metalloproteinases-3 and 13 (MMP-3, MMP-13) was performed. TGF-b1 and PDGF-BB concentrations were highest in PRP and PP. Growth factor quantity was unchanged in BMA, increased in PRP, and decreased in PP over 4 days. TGF-b1 and platelet concentrations were positively correlated. Lyophilized PP and PRP resulted in increased COL1A1:COL3A1 ratio, increased COMP, and decreased MMP-13 expression. BMA resulted in decreased COMP and increased MMP-3 and MMP-13 gene expression. Platelet concentration was positively correlated with COL1A1, ratio of COL1A1:COL3A1, and COMP, and negatively correlated with COL3A1, MMP-13, and MMP-3. White blood cell concentration was positively correlated with COL3A1, MMP3, and MMP13, and negatively correlated with a ratio of COL1A1:COL3A1, COMP, and decorin. These findings support further in vivo investigation of PRP and PP for treatment of tendonitis and desmitis. ß

The optimum composition of PRP for the treatment of tendinopathy has not been directly investigated. Persistent inflammation results in inferior repair with scar tissue. The present study indicates that in an animal model, WBC in PRP contributes to inflammatory cytokine production. Therefore, leukocyte-reduced PRP may be the optimum preparation to stimulate superior healing without scar tissue formation.

This study supports the use of orally administered minocycline at a dose of 4 mg/kg bwt every 12 h for the treatment of nonocular infections caused by susceptible (MIC ≤ 0.25 µg/ml) organisms in horses. Further studies are required to determine the dose that would be effective for the treatment of ocular infections.