MicroRNA‑let‑7a inhibition inhibits LPS‑induced inflammatory injury of chondrocytes by targeting IL6R.

Osteoarthritis (OA) is a type of degenerative joint disease that affects the health of the elderly. OA is characterized by articular cartilage degradation and joint inflammation. The present study aimed to investigate the role and mechanism of microRNA‑let‑7a (Let‑7a) in OA by examining its role in lipopolysaccharide (LPS)‑induced cartilage inflammatory injury in ATDC5 cells. ATDC5 cells were treated with various concentrations of LPS. The present results suggested that 5 and 10 µg/ml LPS significantly inhibited ATDC5 cell viability, and 5 µg/ml LPS was selected for further experiments. Reverse transcription‑quantitative PCR (RT‑qPCR) results suggested that treatment with LPS significantly induced the expression levels of multiple inflammatory factors, including tumor necrosis factor‑α (TNF‑α), interleukin (IL)‑1β, IL‑6 and IL‑8, and increased the expression level of Let‑7a in ATDC5 cells. IL‑6 receptor (IL‑6R) was identified to be a direct target of Let‑7a using TargetScan and a dual‑luciferase reporter assay. Subsequently, Cell Counting Kit‑8 and flow cytometry analyses identified that Let‑7a inhibitor could significantly promote cell viability and reduce cell apoptosis in ATDC5 cells treated with LPS, and these effects could be reversed by transfection with small interfering (si)RNA‑IL‑6R. ELISA was used to examine the expression of inflammatory factors in ATDC5 cells following treatment with LPS. Additionally, RT‑qPCR and western blotting were performed to detect the mRNA and protein expression level of IL‑6R and STAT3. The present results suggested that Let‑7a inhibitor significantly reduced the expression level of TNF‑α, IL‑1β, IL‑6 and IL‑8 in ATDC5 cells, and this effect was reversed by transfecting siRNA‑IL‑6R. Moreover, RT‑qPCR and western blot assay results suggested that Let‑7a inhibitor significantly increased the expression level of IL‑6R and phosphorylated STAT3, and these effects could be reversed by siRNA‑IL‑6R. Collectively, Let‑7a inhibitor increased cell proliferation, reduced apoptosis and inhibited inflammatory response in ATDC5 cells treated with LPS. The present study provided a new potential therapeutic target for OA treatment.