Abstract
Five different types of carriers combined with bone morphogenetic protein (BMP) were implanted into the dorsal subcutaneous tissue in the rat in order to study and compare the osteoinductive capacity and histological patterns. The carriers were: insoluble bone matrix (IBM), porous particles of hydroxyapatite (PPHAP), wet and dry collagen beads (CBw, CBd), fibrous collagen membrane (FCM), and fibrous glass membrane (FGM). The carriers alone were implanted for control studies. Each composite and its surrounding tissues were removed after 1, 2 and 3 weeks, and were studied by routine histology. Our results demonstrated that BMP-IBM, BMP-CBd, BMP-FCM and BMP-FGM induced bone tissue in a process that resembled an endochondral ossification mode; in BMP-IBM and BMP-CBd there was an early initiation of the process, in contrast with BMP-FCM and BMP-FGM where a delayed endochondral ossification was observed. These systems, with the exception of BMP-FGM, also induced bone formation through a direct ossification mode. On the other hand, BMP-PPHAP and BMP-CBw induced bone formation in a process that resembled an intramembranous ossification. BMP-carrier composites induce immature mesenchymal cells to become either osteogenetic or chondrogenetic cells, or both, depending on the physicochemical nature of the carrier that affected the microenvironment for cell differentiation. The presen study suggests that BMP-FCM, BNIP-PPHAP and BMP-CBd could be applicable carriers to explore the osteoinductive function of BMP, since no side-effects caused by the carrier were observed.
