Temporal and Spatial Expression of TGF-b1 in the Early Phase of Patellar Tendon Healing after Application of Platelet Rich Plasma.

BACKGROUND The aim of this study is to find out the spatial and temporal expression of TGF-b1 during the tendon healing, after application of Platelet Rich Plasma (PRP). METHODS A patellar tendon defect model in rabbits was used for this purpose. 48 skeletally mature New Zealand White rabbits, weighing 3.5 kg, were used for this study. Equal numbers of animals from both groups were sacrificed at 4 different time points (1st, 2nd, 3rd, and 4th week). A full thickness patellar tendon substance in the right limb of each animal was excised from its central portion during the operation. PRP with a gel form was applied and filled the tendon defect in PRP group. No PRP was applied in the tendon defect of controls. Histological sections with hematoxylin-eosin and immunohistochemical sections with an anti-TGF-b1 primary antibody were made for the evaluation of the results. RESULTS A differentiation of the healing process was observed in the PRP group in comparison with the control group. TGF-b1 expression was detected in various cell populations (inflammatory cells, endothelial cells, macrophages, and tenocytes). Both cytoplasmic and nuclear expressions were present. The larger amounts of immunoexpression were localized in epitenon and in the repair site. PRP group showed stronger and more extensive staining at 1st and 2nd week (P<0.0001), whereas control group showed more extensive staining at the 3(rd) and 4(th) week (P<0.0001). CONCLUSIONS Our study demonstrates that locally application of PRP result in an alteration of TGF-b1 expression during the healing of a patellar tendon defect.