Vitality of chondrocytes in the mandibular condyle as revealed by collagen formation. An autoradiographic study with 3 H-Proline.

Histological and autoradiographic studies using 3H-proline indicate that cartilaginous tissue in the mandibular condyle maintains morphologic and metabolic characteristics of an embryonic type of tissue. Cartilage cells in the condyle lack the specific arrangement and cellular homogeneity characteristic of more differentiated endochondral growth sites. Through dedifferentiation many chondrocytes in the mandibular condyle appear to outlive the hypoxic conditions that are reported to prevail within the mineralizing zone. Chondrocytes in this zone reveal only a minimal amount of 3H-proline uptake in comparison with the cells in the chondroblastic and premineralizing zones. The dedifferentiated chondrocytes appear to redifferentiate into more specialized cells, possibly osteoprogenitor cells, as they reveal a significant increase in 3H-proline incorporation in the vicinity of the ossifying front. These observations on proline metabolism support the concept that calcification in the condylar cartilage is not necessarily accompanied by degeneration and death of the chondrocytes.