Objective      To construct lentiviral vectors for overexpression and RNA interference of inhibitors of differentiation 1 (Id1) gene

and observe the changes of cartilage phenotype molecules secreting from bone morphogenetic proteins 2 (BMP-2)-induced nucleus pulposus cells after adjusting the expression level of Id1 gene.       Methods      The sequences for overexpression and RNA interference of human Id1 gene were designed and linked into lentiviral vectors by genetic recombination technology

and then the constructed lentiviral vectors were introduced into 293T cells to determine the titers. After the nucleus pulposus cells were transfected with the 2 kinds of recombinant lentiviruses

the expression of Id1 at mRNA and protein levels were assayed by real-time quantitative PCR and Western blotting respectively. Then

the nucleus pulposus cells were sequentially transfected with recombinant adenovirus AdBMP2 and the 2 kinds of lentiviruses

and the capacity of expressing cartilage phenotype molecules was detected by qRT-PCR.       Results      The expression of Id1 at mRNA and protein levels in the nucleus pulposus cells were changed after lentivirus transfection

and compared with the normal cell control group (0.428±0.079) and negative control group (0.400±0.045)

the Id1 gene expressions were increased in the overexpression group (0.848±0.154) and decreased in the RNAi group (0.115±0.014)

with statistically significant differences (P0.01). The Id1 gene overexpression could promote the mRNA expression of collagen Ⅱ (0.407±0.083) and Agreecan (0.284±0.074)

and there was statistically significant difference as compared with the GFP group (P0.01). After AdBMP2 transfection

the Id1 gene overexpression could further promote the mRNA expression of collagen Ⅱ (0.590±0.072) and Agreecan (0.351±0.066)

while the down-regulation expression of Id1 gene could inhibit the expressions of collagen Ⅱ (0.244±0.060) and Agreecan (0.168±0.034)

with statistically significant difference (P0.01).       Conclusion      Id1 can promote the expression of cartilage phenotype molecules

and its expression change can significantly affect the secretion of cartilage phenotype molecules in the BMP-2-induced nucleus pulposus cells

thus Id1 may be the key factor in maintaining cartilage phenotype of the BMP-2-induced intervertebral disc cells.