Immunohistochemical localization of the matrix glycoprotein tenascin in the skull of the growing rat.

Tenascin is an extracellular matrix glycoprotein which interacts with other matrix molecules and with cells, and which appears to play important roles in growth and differentiation. The immunohistochemistry of sections of newborn, 5-day and 20-day-old rats showed that accumulation of tenascin was largely restricted to bones, cartilages and teeth. It was also present in the periosteal and endosteal surfaces of membrane bones, in perichondrium, and ion the dental pulp, but was absent from mature bone, cartilage and dentine. In nasal cartilage, tenascin was present only in the perichondrium, whereas in the condylar cartilage staining was observed in the proliferating and maturing cell layers but not in the hypertrophied cartilage. These differences may reflect differences in the growth mechanisms of primary and secondary cartilages. Accumulation of tenascin was particularly striking in areas where the periosteum or perichondrium was thickened such as sites of some muscle attachments, sutures and condylar cartilage. The restricted distribution of tenascin is unlike the patterns observed for other extracellular matrix molecules. Tenascin may have a unique role in bone growth and remodelling in the craniofacial region.