An immunolocalization study of tissue inhibitors of metalloproteinase-1 of bone graft healing on parietal bone

Abstract

This immunolocalization study was performed to investigate the temporal and spatial expression of tissue inhibitors of metalloproteinase (TIMP) 1 within endochondral and intramembranous bone grafts during the early stages of healing, in the hope of gaining a better understanding of the mechanisms of bone graft healing, which could influence the choice of bone graft used. Twenty-seven adult New Zealand White rabbits were used as the experimental model. Autogenous bone grafts taken from the cranial bone (intramembranous in origin) and the femur (endochondral in origin) were grafted into skull defects created on either side of the parietal suture. Rabbits were killed on days 1 to 9 postgrafting, and the bone graft alone was harvested for immunolocalization of TIMP-1. In endochondral bone grafts, TIMP-1 was expressed on days 1 to 3, followed by a period of absence until days 8 and 9. Intramembranous bone grafts did not express TIMP-1 until days 6 to 9. The timing and location of TIMP-1 expression coincided with osteogenesis, which indicates a role for TIMP-1 in preserving newly formed bone during the initial stages of graft healing. The differential temporal expression of TIMP-1 in endochondral and intramembranous bone grafts suggests that bone graft type plays an important role in influencing the healing process mediated by the host tissues. The earlier expression of TIMP-1 in endochondral bone grafts could be the reason for delayed vascularization of defects containing these grafts, whereas the delayed expression of TIMP-1 in intramembranous bone grafts could allow earlier vascularization of the intramembranous bone grafts. ©2008Muntaz B. Habal, MD.