Osteoarthritis is the most prevalent form of arthritis in the world. Certain signaling pathways, such as the wnt pathway,
are involved in cartilage pathology. Osteoarthritic chondrocytes undergo morphological and biochemical changes that lead to
chondrocyte de-differentiation. We investigated whether the Wnt pathway is involved in de-differentiation of human articular
chondrocytes in vitro. Human articular chondrocytes were cultured for four passages in the presence or absence of IL-1 in
monolayer or micromass culture. Changes in cell morphology were monitored by light microscopy. Protein and gene expression
of chondrocyte markers and Wnt pathway components were determined by Western blotting and qPCR after culture. After culturing
for four passages, chondrocytes exhibited a fibroblast-like morphology. Collagen type II and aggrecan protein and gene expression
decreased, while collagen type I, matrix metalloproteinase 13, and nitric oxide synthase expressions increased. Wnt molecule
expression profiles changed; Wnt5a protein expression, the Wnt target gene, c-jun, and in Wnt pathway regulator, sFRP4 increased.
Treatment with IL-1 caused chondrocyte morphology to become more filament-like. This change in morphology was accompanied
by extinction of col II expression and increased col I, MMP13 and eNOS expression. Changes in expression of the Wnt pathway
components also were observed. Wnt7a decreased significantly, while Wnt5a, LRP5, β-catenin and c-jun expressions increased.
Culture of human articular chondrocytes with or without IL-1 not only induced chondrocyte de-differentiation, but also changed
the expression profiles of Wnt components, which suggests that the Wnt pathway is involved in chondrocyte de-differentiation