Expression of BMP-7 and its receptors in rats with unilateral ureteral obstruction

AIM: To explore the expression changes of bone morphogenetic protein-7 (BMP-7) and its receptors (BMPR-Ⅱ, ALK-2, ALK-3, ALK-6) in the renal tubulo-interstitial lesions induced by unilateral ureteral obstruction (UUO). METHODS: Rats were divided into normal control, sham operation and UUO groups, and sacrificed at postoperative day 1, 3, 7 and 14. The mRNA levels of BMP-7, BMPR-Ⅱ, ALK-2, ALK-3 and ALK-6 were examined by RT-PCR. The protein expression site and level of BMP-7 was detected by immunohistochemistry staining. RESULTS: Compared to sham operation group, the mRNA levels of BMP-7, BMPR-Ⅱ, ALK-2 and ALK-3 were significantly decreased, but the change of ALK-6 mRNA was not marked in UUO rats. The reduction of mRNA expression levels of BMP-7, BMPR-Ⅱ, ALK-2 and ALK-3 in the kidney tissue aggravated along with the delayed post-operated days. The results of immunohistochemistry staining indicated that BMP-7 mainly expressed in renal tubular and interstitial, rarely in glomeruli. In UUO rats, the protein expression of BMP-7 decreased in varying degrees according to the post-operated days. CONCLUSION: The loss of BMP-7 and its receptors (BMPR-Ⅱ, ALK-2, ALK-3) were observed in the early phase of fibrotic process and this may play a very important role in mediating the renal tubulointerstital fibrosis.