COL10A1 and osteoarthritis: Type X collagen synthesis is observed in the cartilaginous callus, which is composed of hypertrophic and degenerative chondrocytes, suggesting increased vascularity and matrix mineralization during fracture repair.(10) As to the correlation of COL10A1 expression and chondrocyte maturation with osteoarthritis, previous studies have reported the upregulation of COL10A1 and enhanced chondrocyte hypertrophy in human osteoarthritic cartilage.(11,12) It was also suggested that upon osteoarthritis progression, factors that constrain articular chondrocyte maturation are relieved.