Collagen bead carriers with bone morphogenetic protein (BMP) were implanted in the rat dorsal subcutaneous tissues in order to study and compare the osteoinductive capacity and histological patterns. The carriers were wet (CBw) and dry collagen beads (CBd) and of round star shaped varieties. The carrier alone was implanted as a control. Each composite and its surrounding tissue were removed 1, 2 and 3 weeks later and were studied by routine histology.
BMP-CBd induced bone tissue in a process that resembled endochondral ossification mode BMP-CBd showed an early initiation of the process.This system also induced bone formation through a direct ossification mode. One the other hand, BMP-CBw induced bone formation in a process resembling intramembranous ossification. BMP-collagen bead composites induced immature mesenchymal cells to become either osteogenetic or chondrogenetic cells or both, depending on the shape of the carrier that affected the microenvironment for cell differentiation.
