Type I and type III procollagen gene expressions in the early phase of ligament healing in rabbits: an in situ hybridization study

The purpose of this study is to observe type I and type III procollagen gen e expressions in the healing ligament using in situ hybridization histochem istry. The rabbit medial collateral ligaments were incised and harvested at 3, 7, 14, and 28 days postoperatively. The healing ligament showed increas ed expression of both procollagen genes through this period compared with t he unoperated ligament, The peak expression level was observed at 7 or 14 d ays for type I and at 7 days for type III, respectively. The strongest expr ession of both genes was detected in the scar tissue created between the en ds of the old ligament. Although type III procollagen gene expression was o bserved almost only in the newly created scar tissue, type I procollagen ge ne was expressed not only in the scar tissue, but also at the ends of the p reviously normal ligament. These results suggest that type I collagen synth esis begins shortly after ligament injury and occurs at the ends of the inj ured ligament as well as in the scar tissue, and that type III collagen is largely synthesized in the scar tissue around one week after injury but con tinues being synthesized for at least four weeks after injury. (C) 2001 Ort hopaedic Research Society. Published by Elsevier Science Ltd. All rights re served.