009 Differential Phenotypical Expression of Healing vs. Normal Fibroblasts

Abstract

Fibroblasts from a healing ligament likely have differential phenotypical expression from those in an intact ligament, because fibroblasts at the healing site need to repair/regenerate the wounded matrix around them caused by injury, whereas normal fibroblasts just maintain an intact matrix. This study was designed to determine the differences in proliferation, collagen production, α-smooth muscle actin (α-SMA) expression, and contraction between healing and normal fibroblasts. Transected and sham-operated rat medial collateral ligaments (MCL) were used to obtain healing and normal fibroblasts, respectively. It was noted that healing and normal MCL fibroblasts in culture were seen to have a similar morphology. However, healing fibroblasts in monolayer culture proliferated 1.4-fold faster at 48 hours and had 1.7-fold greater protein expression of α-SMA than normal fibroblasts. In addition, it was noted that the proliferation of healing fibroblasts in collagen gels was not significantly different from that of normal fibroblasts at 24 hours, but it was at 48 hours. Furthermore, in collagen gels, healing fibroblasts produced 10% more type I collagen than normal fibroblasts and generated 1.6- and 1.7-fold larger contractile forces at 15 and 20 hours, respectively, than their normal counterparts. Taken together, the results of this study show that healing fibroblasts possess a differential proliferation, α-SMA protein expression, and contraction than normal fibroblasts. This study also highlights the importance of using healing fibroblasts to study the cellular and molecular mechanisms of ligament healing. Supported by the NIH grant AR049921 and Whitaker Foundation Grant (JHW)