Rcn3 is Involved in Postnatal Tendon Development by Regulating Collagen Modification and Fibrillogenesis

Tendon plays a critical role in the joint movement by transmitting force from muscle to bone. This transmission of force is facilitated by its structure, which consists of an aligned and organized type I collagen. Despite the importance of collagen structure, the biological mechanisms regulating fibrillogenesis are not well understood. Here we examine the function of Rcn3 in postnatal tendon development and collagen fibrillogenesis using a genetic mouse model. Loss of Rcn3 in tendon caused decreased tendon thickness, abnormal tendon cellular maturation, and decreased mechanical properties. Interestingly, Rcn3 deficient mice exhibited a relatively smaller distribution of collagen fibril and over-hydroxylation in C-telopeptide cross-linking lysine from α1(1) chain. Besides, the proline 3-hydroxylation sites in type I collagen were also over-hydroxylated in Rcn3 deficient mice. Our data collectively suggest that Rcn3 is required for proper postnatal tendon development via regulation of collagen modification and fibrillogenesis.