MicroRNA­1 regulates the development of osteoarthritis in a Col2a1­Cre­ERT2/GFPfl/fl­RFP­miR­1 mouse model of osteoarthritis through the downregulation of Indian hedgehog expression.

ABSTRACT

The present study assessed the effects of microRNA­1 (miR­1) on the development of osteoarthritis using human tissues and a Col2a1­Cre­ERT2/GFPfl/fl­RFP­miR­1 mouse model of osteoarthritis. Human cartilage tissues (n=20) were collected for reverse transcription­quantitative polymerase chain reaction (RT­qPCR), histological analysis and immunohistochemistry experiments. A transgenic mouse model of osteoarthritis was established by subjecting Col2a1­Cre­ERT2/GFPfl/fl­RFP­miR­1 transgenic mice to anterior cruciate ligament transection (ACLT). Mice were subjected to radiography and in vivo fluorescence molecular tomography (FMT), while mouse tissues were collected for histological analysis, RT­qPCR and Safranin O staining. It was found that the miR­1 level was downregulated, whereas the levels of Indian hedgehog (Ihh), as well as those of its downstream genes were upregulated in human osteoarthritic cartilage. In the transgenic mice, treatment with tamoxifen induced miR­1, as well as collagen, type II (Col2a1) and Aggrecan (Acan) expression; however, it decreased Ihh, glioma­associated oncogene homolog (Gli)1, Gli2, Gli3, smoothened homolog (Smo), matrix metalloproteinase (MMP)­13 and collagen type X (Col10) expression. Safranin O staining revealed cartilage surface damage in the non­tamoxifen + ACLT group, compared with that in the tamoxifen + ACLT group. Histologically, an intact cartilage surface and less fibrosis were observed in the tamoxifen + ACLT group. Immunohistochemistry revealed that the protein expression of Ihh, Col10, and MMP­13 was significantly higher in the joint tissues of the non­tamoxifen + ACLT group than in those of the tamoxifen + ACLT group. However, Col2a1 expression was lower in the joint tissues of the non­tamoxifen + ACLT group than in those of the tamoxifen + ACLT group. The results of RT­qPCR and FMT further confirmed these findings. On the whole, the findings of the present study demonstrate that miR­1 expression protects against osteoarthritis­induced cartilage damage and gene expression by inhibiting Ihh signaling.