Low-dose halofuginone inhibits the synthesis of type I collagen without influencing type II collagen in the extracellular matrix of chondrocytes

Full-thickness and large area defects of articular cartilage are unable to completely repair themselves and require surgical intervention, including microfracture, autologous or allogeneic osteochondral grafts, and autologous chondrocyte implantation. A large proportion of regenerative cartilage exists as fibrocartilage, which is unable to withstand impacts in the same way as native hyaline cartilage, owing to excess synthesis of type I collagen in the matrix. The present study demonstrated that low-dose halofuginone (HF), a plant alkaloid isolated from Dichroa febrifuga, may inhibit the synthesis of type I collagen without influencing type II collagen in the extracellular matrix of chondrocytes. In addition, HF was revealed to inhibit the phosphorylation of mothers against decapentaplegic homolog (Smad)2/3 and promoted Smad7 expression, as well as decrease the synthesis of type I collagen synthesis. Results from the present study indicated that HF treatment suppressed the synthesis of type I collagen by inhibiting the transforming growth factor-β signaling pathway in chondrocytes. These results may provide an alternative solution to the problems associated with fibrocartilage, and convert fibrocartilage into hyaline cartilage at the mid-early stages of cartilage regeneration. HF may additionally be used to improve monolayer expansion or 3D cultures of seed cells for the tissue engineering of cartilage.