Objective: To study the influence of mutation of -1997G-->T of COL I A1 gene on the biochemical function of osteoblast, and the pathomechanism of BMD.
Methods: Spongy bones were obtained to culture osteoblast primarily during total hip or knee replacements. The genotype of osteoblast was identified with PCR-RFLP. The amount of mRNA of COL I A1 and collagen type I were determined by RT-PCR and ELISA. The growth of osteoblast, the activity of bone ALP, and the amount of calcium in cell matrix and calcium nodus were measured.
Results: Three genotypes GG, GT and TT in osteoblast were successfully identified. Compared with GG and GT genotypes, lower expression of mRNA of COL I A1 gene, lesser collagen type I, calcium in cell matrix, and calcium nodus were found in the cells with TT genotype (P < 0.01). No significant differences were found between GG and GT genotype (P > 0.05). There were no significant differences in age, growth of osteoblast, and activity of bone ALP among the three genotypes (P > 0.05).
Conclusion: Cells with TT genotype have low expression of mRNA of COL I A1 gene and less collagen type I , calcium in cell matrix and calcium nodus. The lower amount of collagen type I synthesized by osteoblast can decrease the matrix outside the bone cells and result in insufficient site for calcium deposition. This may be the cause of lower BMD in patients with TT genotype.