Two patterns of calcification in primary (physeal) and secondary (epiphyseal) growth cartilage.

It is generally stated that the process of cartilage calcification and ossification is the same in the physeal (primary growth center) and epiphyseal (secondary growth center) growth plates. Reexamination of osteophyte growth led to the proposal that these growth plates differ. This proposition was tested by examining rabbit and human material from both sites before and after maceration; both tissue preparations were processed for light microscopy, and the macerated tissues were also studied by scanning electron microscopy (SEM).

The control of cell division in articular chondrocytes.

Our objective was to investigate the factors that control chondrocyte division, namely, (1) steric hindrance caused by the surrounding matrix, (2) growth factors and (3) cell shape. Bovine articular cartilage explants and isolated chondrocytes were cultured in medium containing [3H]-TdR to measure DNA synthesis. The effect of enzyme treatment, growth factors and cell shape was investigated.

Human articular surface chondrocytes initiate alkaline phosphatase and type X collagen synthesis in suspension culture.

The type X collagen is a short chain collagen associated with calcific cartilage and/or the expression of the hypertrophic chondrocyte phenotype. In articular cartilage, type X collagen is restricted to the basal zone of calcified cartilage adjacent to the subchondral bone. However, during pathological change such as in osteoarthritis, the synthesis of type X collagen becomes more widespread but never extends to the articular surface.