THE EXPRESSION OF TYPE-X AND TYPE-VI COLLAGEN AND FIBRILLIN IN RAT MANDIBULAR CONDYLAR CARTILAGE - RESPONSE TO MASTICATION FORCES

Types X and VI collagen and fibrillin were localized by in situ hybrid ization and immunohistochemical methods in the mandibular condyles of rats, and the response of these molecules to post-weaning diets of sof t food, ordinary pellets, or hardened pellets was studied. Type X coll agen was synthesized, particularly in conditions of soft food consiste ncy, by cells in the perichondrium-periosteum and in the bone and by c ells at the erosion Front between cartilage and bone. Type X collagen synthesis diminished under higher compression forces due to masticatio n and with increasing age. Type VI collagen and fibrillin were synthes ized by cells in the perichondrium-periosteum and by chondrocytes and by stromal osteoblasts and were not modified by higher mechanical forc es. In contrast to previous findings in the growth plate of long bones , type X collagen in the mandibular condyle was not synthesized by hyp ertrophic chondrocytes but was associated with cells of the osteoblast ic rather than the chondroblastic phenotype.