Chondrocyte
The only cell type found in healthy cartilage, responsible for producing and maintaining the cartilage matrix. Chondrocytes have limited regenerative capacity. Vosoritide acts on growth plate chondrocytes in achondroplasia, where it counteracts the growth-inhibiting FGFR3 signal to promote bone elongation.
Technical Context
Chondrocytes are the sole cell type in mature cartilage, residing in lacunae within the ECM they produce. They maintain the cartilage matrix through balanced synthesis and degradation of type II collagen and proteoglycans (primarily aggrecan). In the growth plate, chondrocytes exist in distinct zones: reserve zone (quiescent stem-like cells), proliferative zone (rapidly dividing, forming columns), pre-hypertrophic zone (beginning to enlarge), hypertrophic zone (maximally enlarged, secreting type X collagen and VEGF, preparing for ossification), and calcification zone (apoptosing, matrix mineralising, replaced by bone). Vosoritide acts on proliferative and pre-hypertrophic chondrocytes: CNP → NPR-B → cGMP → PKG-II → inhibition of FGFR3-activated MAPK pathway → restored chondrocyte proliferation and hypertrophy → increased growth plate height → increased bone elongation. This mechanism is specific to the growth plate — vosoritide does not affect articular chondrocytes or mature bone.