Correlate gene expression regulation of bone metabolism of the proximal tubular epithelial cells to osteoblasts in vitro

Purpose To investigate the direct accommodation of the proximal tubular epithelial cells (PTECs) on correlate gene expression in osteoblasts (OB). Methods The rat proximal tubular epithelial cells and osteoblasts were culture to establish the co-culture system in vitro. The PTECs were treated with PTH,γ-ray and 25(OH)D3 in advance, then co-cultured with osteoblast assigned to 4 group as follows:(1) Single- culture group (OB);(2) Co-culture group (PTECs + OB);(3) Stimulation co-culture group (PTECs stimulated by PTH + 25(()H)D, + OB) and (4) Inhibition co-culture group (PTECs irradiated byγ-rays + 25(OH)D3 + OB). The expression level of ALP, BGP, COL I , RANKL and OPG mRNA in osteoblasts were detected by RT-PCR technigne. Results The expression levels of ALP, BGP, COL I mRNA of the co-culture group were significantly lower than those in single-culture group (P0. 001); The expression levels of ALP,BGP,COL I mRNA the stimulation co-culture group were significantly higher than those in the co-culture group (P0. 05-P0. 001 ) ; The expression of ALP mRNA of the inhibition co-culture group was significantly lower than that of the co-culture group (P0. 001 ). The expression of BGP and COL I mRNA were not changed; The co-culture group compared with Single-culture group were detected that the expression levels of RANKL and OPGmRNA were significantly decreased (P0. 001) , but the RANKL/ OPG was higher than the latter (P0. 01). The stimulationco-culture group compared with co-culture group were detected that the expression level of OPGmRNA was remarkably up-regulated(P0. 01), the change of RANKL mRNA was not marked, and the RANKL/ OPG was obviously decreased (P0. 01). Compared with co-culture group, the expression of OPG mRNA of the Inhibition co-culture group was lower (P0. 001), and RANKL was not changed, RANKL/ OPG was increased obviously (P0. 001). Conclusions PTECs can direct regulate the gene expression of osteoblasts in vitro. The established co-culture system can be used to study the drug screening and action mechanism on bone metabolism.