Bone morphogenetic proteins (BMPs) expression in the femoral heads of patients with avascular necrosis

Avascular necrosis (AVN) is a disorder of the bone repair process which usually results in femoral head (FH) destruction. Bone morphogenetic proteins (BMPs) are the key proteins regulating bone remodelling and healing. BMPs gene expression levels were analyzed in the normal and necrotic sites of osteonecrotic FHs. Quantitative RT-PCR for BMP-2, -4, -6, -7 genes was performed in bone tissue samples from 47 osteonecrotic FHs. Protein levels of BMP-2, -4, -6 were estimated by Western Blot. Statistical analysis was performed using the Wilcoxon signed rank test. BMP-2 and BMP-6 mRNA levels were higher in the normal than the necrotic site (normal/necrotic: 16.8/6.8 and 1.75/1.64, respectively). On the contrary, BMP-4 mRNA levels were higher in the necrotic (0.75) than the normal (0.62), while BMP-7 mRNA levels were extremely low. At the protein level, BMP-2 continued to have a higher expression in the normal region (normal/necrotic: 0.67/0.64). BMP-4 and -6 were detected at higher levels in the necrotic site (normal/necrotic: 0.51/0.61 for BMP-4, 0.51/0.56 for BMP-6), while BMP-7 was not detectable. Different BMP levels between the normal and necrotic site, as well as discrepancies between the gene and protein expression pattern suggest a different regulation mechanism for BMPs between the two regions of FHs. The understanding of the expression pattern and the correlation of BMPs could lead to a more successful use in the prevention and treatment of AVN.