Glucosamine promotes chondrocyte proliferation via the Wnt/β‑catenin signaling pathway

The present study investigated the mechanism underlying the effects of glucosamine (GlcN) on the proliferation of chondrocytes isolated from the knee cartilage of Sprague‑Dawley rats. Chondrocytes were treated with various concentrations of GlcN or without GlcN. The effects of GlcN on chondrocyte proliferation were determined using reverse transcription‑polymerase chain reaction, western blot analysis and immunohistochemistry. The results indicated that GlcN significantly improved chondrocyte viability, accelerated G1/S transition during progression of the cell cycle and promoted the expression of cell cycle regulatory proteins, including cyclin D1, cyclin‑dependent kinase (CDK)4 and CDK6, thus indicating that GlcN may promote chondrocyte proliferation. Furthermore, GlcN upregulated the expression levels of Wnt‑4, Frizzled‑2 and β‑catenin, and downregulated the expression of glycogen synthase kinase‑3. GlcN also promoted β‑catenin translocation; β‑catenin is able to activate numerous downstream target genes, including cyclin D1. To determine the role of the Wnt/β‑catenin signaling pathway in chondrocyte proliferation, the Wnt/β‑catenin signaling pathway was inhibited using Dickkopf‑1 (DKK‑1), after which chondrocytes were treated with GlcN. The results demonstrated that the expression levels of β‑catenin and cyclin D1 were decreased in chondrocytes treated with DKK‑1 and GlcN. These results suggested that GlcN may promote chondrocyte proliferation via the Wnt/β‑catenin signaling pathway.