Platelet-Rich Plasma (PRP) Impairs the Craniofacial Bone Repair Associated with Its Elevated TGF-β Levels and Modulates the Co-Expression between Collagen III and α-Smooth Muscle Actin

Transforming growth factor-beta (TGF-beta) is considered the main inducer of both the alpha-smooth muscle actin (alpha-SMA) phenotype and collagen synthesis and deposition and plays a significant role in the tissue repair and the development of fibrosis. Since the PRP constitutes an important source of TGF-beta and its efficacy on the craniofacial bone repair remains controversy, the aim of this study was to evaluate the effect of PRP in the presence of levels of TGF-beta on PRP samples, as well as in the presence of collagen III and alpha-SMA+ cells, while comparing these results by means of a histomorphornetric analysis of the bone matrix and fibrous deposition on the bone repair. Four bone defects of 16 mm(2) were created on the calvarium of 21 rabbits. The surgical defects were treated with either particulate autograft, particulate autograft mixed with PRP and PRP alone. Animals were euthanized at 15, 30, and 45 days postoperative. Histomorphometric and immunohistochemical analyses were performed to assess repair time, as well as the expression of collagen III, and alpha-SMA. The histomorphometric results demonstrated intensive deposition of fibrous tissue while hinder bone deposition occurred in PRP groups. These results coincided with higher values of the TGF-beta on the PRP sample, also larger occurrence of diffuse collagen III deposition and higher presence of alpha-SMA+ cells spread among the fibrous tissue. Thus, the higher levels of TGF-beta associated with the both expression of collagen III and beta-SMA on defect treated with PRP suggest that its biomaterial induce an effect that can be considered similarly to a fibroproliferative disorder. (C) 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:457-463, 2011