〔Abstract〕 Objective To study the protective effect and mechanism of iPSC-MSCs on cartilage matrix in knee osteoarthritis(KOA) patients in vitro. Methods Cartilage tissues removed from KOA patients with joint replacement surgery were collected and subjected to tissue and cellular experiments, respectively. Cartilage tissue was cut into small pieces and randomly divided into a control group, an IL-1β(10 ng/ml) induction group, and iPSC-MSCs groups. Except for the control group, cartilage tissues from each group were stimulated with IL-1β(10 ng/ml) for 96 h and then co-cultured with different amounts of iPSC-MSCs(1×104, 1×105, 1×106) cells for 72 h. For in tissues, the pathological changes of isolated cartilage tissues were examined by HE staining. The levels of ADAMTS-4, ADAMTS-5, and type II collagen expression were analyzed by immunohistochemistry, while the levels of MMP13, IL-6, and IL-10 in culture supernatants were detected by ELISA kits. The 2 to 5 generations of chondrocytes, which were extracted from cartilage tissue of KOA patients, were stimulated with IL-1β(10 ng/ml) for 48 h and then co-cultured with different concentrations of iPSC-MSCs(1×104, 1×105, 1×106) cells for 72 h. Immunofluorescence and Western blot detected the expression of RUNX2, ADAMTS-4, and ADAMTS-5 in chondrocytes. Results Comparison with the control group, in the IL-1β-induced group, the levels of RUNX2, ADAMTS-4, and ADAMTS-5 increased, the level of type II collagen decreased, the levels of MMP-13 and IL-6 in the culture supernatant increased(P<0.05), and the level of IL-10 decreased(P<0.05); Compared with the IL-1β-induced group, co-culture of different numbers of iPSC-MSCs reduced the levels of MMP-13 and IL-6 in the supernatant, decreased the expression of RUNX2, ADAMTS-4, and ADAMTS-5, promoted type II collagen expression and elevated IL-10 levels. Conclusion iPSC-MSCs inhibited ADAMTS-4 and ADAMTS-5 expression in vitro, reduced cartilage extracellular matrix degradation, and played a role in articular cartilage protection.