Human Umbilical Cord Mesenchymal Stem Cells Alleviate Rat Knee Osteoarthritis via Activating Wnt/ β-catenin Signaling Pathway

Background: Osteoarthritis (OA) is a chronic disease characterized by joint cartilage degeneration, destruction, and osteogenic hyperplasia. Human umbilical cord mesenchymal stem cells (hUC-MSCs) have attracted increasing research interest due to their high clonogenic, proliferative, and migratory potential, as well as their improved secretion of relevant chondrogenic factors. This study evaluated the therapeutic potential and underlying mechanism of hUC-MSCs in alleviating pathological symptoms of OA.Methods: For the in vivo study, OA rats were established by the Hulth method to observe the therapeutic effect of intra-articular injection of hUC-MSCs. X-ray tests, gross observations, and histological and immunohistochemical assessments were conducted in rats. Levels of interleukin-1 beta (IL-1 beta), IL-6, matrix metalloproteinase-13 (MMP-13), and tissue inhibitor matrix metalloproteinase-1 in rats' synovial fluid were measured using enzyme-linked immunosorbent assay kits. For the in vitro study, hUC-MSCs and chondrocytes were cultured to explore the effect and underlying mechanisms of hUC-MSCs on OA. Apoptosis, proliferation, and glycosaminoglycan (GAG) were measured in the chondrocytes. The relative expression of aggrecan, COL-2, and SOX-9 mRNA was quantified by real-time polymerase chain reaction. Expressions of Wnt/beta-catenin signaling molecules were measured by Western blot.Results: We found that intra-articular injection of hUC-MSCs reduced the combined score, increased the expression of collagen II, and decreased the expression of MMP-13, IL-1 beta, and IL-6 in rat knee joints. Additionally, hUC-MSCs increased the content of GAGs, inhibited chondrocyte apoptosis, and promoted chondrocyte proliferation. The expression of aggrecan, COL-2, and SOX-9 mRNA in chondrocytes was promoted by hUC-MSCs via activation of the Wnt/beta-catenin signaling pathway.Conclusion: Overall, this study demonstrated that hUC-MSCs induce the secretion of some cytokines via the paracrine function to activate the Wnt/beta-catenin signaling pathway to reduce the pathological condition of OA and maintain the proper expression of cytokines and extracellular matrix proteins.