Effects of Notch1 knockdown on the proliferation and the differentiation of human articular chondrocytes

Purpose: Osteoarthritis (OA) is the main degenerative disease of the joint, altering the differentiation pattern of articular chondrocytes. In mouse, Notch signaling is critical regulator of cartilage development and homeostasis. In human, NOTCH1 pathway is overexpressed in OA articular cartilage compared to healthy chondrocytes. Our aim was to investigate if NOTCH1 knockdown could be a potential therapeutic approach in OA. Methods: Primary human OA articular chondrocytes were NOTCH1 silenced by siRNA and cultured in 3D up to 3 weeks. Proliferation was assessed by cell cycle and DNA quantification. Cell viability, catabolic factors release and cell differentiation were also analysed. Results: NOTCH1 silencing reduced active proliferation, but had no effects on senescence and cell cycle regulators. In 3D cultures, mimicking OA progressive differentiation, NOTCH1 silenced cells showed higher viability, reduced differentiation and matrix metalloproteases production. Conclusions : NOTCH1 silenced OA chondrocytes showed a more helthy phenotype, by reducing terminal differentiation and increasing cell viability. NOTCH1 appears a therapeutic target to reduce OA progression.