BMPS INDUCE ENDOCHONDRAL OSSIFICATION IN RATS WHEN IMPLANTED ECTOPICALLY WITHIN A CARRIER MADE OF FIBROUS GLASS MEMBRANE

Background: Bone morphogenetic proteins (BMPs) replicate the process o f embryonic bone formation when implanted in ectopic sites, Our previo us studies have indicated that BMPs can induce intramembranous ossific ation, i.e., direct bone formation without preexisting cartilage when implanted in rats subcutaneously by using the fibrous collagen membran e (FCM) as a carrier for implanting BMPs (Sasano et al, 1993, Anat, Re c., 236:373-380), The present study was designed to investigate how th e physicochemical property of the carrier material influences the proc ess of bone formation induced by BMPs, using a carrier made of fibrous glass membrane (FGM). Methods: BMPs, partially purified from bovine m etatarsal bones, were added to an FGM carrier and implanted subcutaneo usly in rats, The implants were analyzed at weekly intervals, and the osteogenic process induced by BMPs was examined by histology and immun ohistochemistry for cartilage and bone formation. Results: Neither car tilage nor bone were observed after week 1, Cartilage formation occurr ed within the carrier after week 2, although no bone formation was see n. The cartilage matrix showed immunoreactivity for types II, X, and I collagen, Bone was induced on the previously formed cartilage after w eek 3, The bone matrix stained with anti-osteocalcin antibody and with anti-type I collagen antibody, The cartilage was replaced by bone and bone marrow after week 10. Conclusions: BMPs cause endochondral ossif ication when administered with an FGM carrier, The physicochemical pro perty of the carrier may be involved in the BMP-induced phenotype expr ession of bone and cartilage. (C) 1997 Wiley-Liss, Inc.