miR-18a-3p Encourages Apoptosis of Chondrocyte in Osteoarthritis via HOXA1 Pathway

Background: Osteoarthritis is a disorder of joints featuring inflammation and degeneration of articular cartilage. Recently, miRs have been found to be associated in the regulation of chondrocytes and their apoptosis. miR-18a-3p has been found to be associated in the pathogenesis of rheumatoid arthritis, however, its role in articular cartilage tissues remains unclear. C57BL/6 strain of mice and human cartilage tissue were used for the study. Histological analysis was done on isolated cartilage samples followed by TUNEL assay and immunohistochemical analysis. The chondrocytes were isolated from mouse and human cartilage tissues, RNA was isolated and subjected for qRT-PCR analysis. The chondrocytes were transfected with miR-18a-3p agomir, antagomir and siHOXA-1. Luciferase assay was done in 293T cells. Flow cytometry analysis was done and western blot analysis for studying the expression of proteins. The expression of miR-18a-3p was upregulated in chondrocytes after exposing them to interlukin-1 beta (IL-1 beta) in vitro. The transfection of miR-18a-3p antagomir halted the IL-1 beta mediated apoptosis. The luciferase assay suggested that miR-18a-3p targets the 3'IJTR region of HOXA1 gene thus blocking its expression. The treatment of HOXA1 siRNA demonstrated the rescuing effect of miR18a-3p antagomir on the apoptosis of chondrocytes. Treatment of miR-18a-3p antagomir attenuated the surface of cartilage in osteoarthritis mice and the agomir worsened it. TUNEL assay suggested decreased apoptosis and over-expression of HOAX1 in osteoarthritis mice post miR-18a-3p knock-down. The findings confirmed the involvement of miR-18a-3p/HOXA1 pathway as a potential mechanism in the regulation of Osteoarthritis.