Growth factor expression in healing rabbit medial collateral and anterior cruciate ligaments

Exogenously administered growth factors such as platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-beta) and basic fibroblast growth factor (bFGF) have been shown to affect connective tissue healing in vivo, but their intrinsic role in the healing response has not been established. In the present study, immunohistochemistry with antibodies directed against these growth factors showed that expression of PDGF, TGF-beta 1 and bFGF was increased in and around the wound site in the rabbit medial collateral ligament (MCL) seven days following surgical injury. The strong expression of PDGF correlated with the observed increased cellularity consistent with this growth factor's mitogenic and chemotactic properties. Expression of these growth factors was also increased in wounded rabbit anterior cruciate ligaments (ACL) at seven days following surgical injury, but such expression was limited to the edge of the ACL injury site and was of lesser intensity relative to the MCL. This study suggests that PDGF and TGF-beta 1, and to a lesser extent bFGF, are actively involved during the early stage of MCL healing, but have a more limited presence in the injured rabbit ACL.