[Effect of BMP-2 and -3 overexpression on osteogenic and chondrogenic differentiation of prenatal mouse intervertebral disc cells in vitro].

OBJECTIVE: To investigate the effect of recombinant adenovirus-mediated bone morphogenetic protein (BMP)-2 and -3 over expressions on chondrogenesis and osteogenesis of prenatal mouse intervertebral disc cells and provide experimental evidences for the application of BMPs in the therapy of disc diseases.

METHODS: The prenatal mouse intervertebral disc cells were infected with a recombinant adenovirus expressing BMP-2 and BMP-3 for 5-7 days, and the expressions of collagen type I (Col I), collagen type II (Col II), aggrecan, osteocalcin, osteoprotegerin and osteopontin mRNAs were detected with RT-PCR. The expression of cartilage matrix was evaluated with toluidine blue staining, and alkaline phosphatase (ALP) activity was detected with ALP reading and ALP staining.

RESULTS: BMP-2 and -3 overexpression did not enhance chondrogenesis and osteogenesis of annulus fibrosus (AF) cells or cause significant increases in the expressions of Col I, Col II or aggrecan mRNA in nucleus pulposus (NP) cells. Adenovirus-mediated overexpression of BMP-2 and BMP-3, however, promoted osteogenesis of NP cells and significantly increased the expression of osteocalcin mRNA; the overexpression of BMP-2, but not BMP-3, enhanced the mRNA expressions of osteoprotegerin and osteopontin. Toluidine blue staining demonstrated that BMP-2 and BMP-3 overexpression did not obviously affect the secretion of cartilage matrix. In NP cells, BMP-2 and -3 overexpression significantly enhanced ALP activity, which was not observed in AF cells.

CONCLUSION: Adenovirus-mediated BMP-2 and -3 overexpression can promote the osteogenic differentiation of NP cells but can not affect osteogenesis of AF cells or chondrogenesis of NP cells.