Biosynthesis and processing of collagens in different cartilaginous tissues.

The distribution, structure, and biosynthesis of various collagen types have been studied in growth and structural cartilage from young rabbits. The major collagen of cartilage is alpha 1(II); however, all cartilage matrix also contains 1 alpha, 2 alpha, 3 alpha (Type Cm), as well as a high molecular weight disulfide-linked collagen (Type M). Cartilage fragments in organ culture demonstrate synthesis of precursors of collagen alpha chains and processing to their final forms. Although Type Cm collagen is present in the same proportion in the matrix of growth and structural cartilage, in vitro radiolabeling of rabbit cartilage showed that only growth cartilage is capable of actively synthesizing Type Cm, except in the newborn period when synthesis of Type Cm does occur in structural cartilage. A low molecular weight collagen (designated G collagen) is synthesized in vitro by growth cartilage but not by structural or articular cartilage. Preferential distribution of these minor collagens in growth cartilage suggests a role in development during normal cartilage growth.