Expression of collagen type III and tenascin-C during joint formation in embryonic chick skull

Expression of collagen type III and tenascin-C was investigated in developing joints of embryonic chick skull using immunohistochemistry and in situ hybridization. At E8.0, the quadratomandibular joint was formed between the quadrate cartilage and the articular cartilage, with an intervening interzone consisting of fibrous tissues. Collagen type III immunoreactivity and COL3A1 mRNA expression were restricted to the interzone and the surface layer of cartilage. By contrast, tenascin-C expression was detected throughout the peripheral layer of the cartilage, but the expression intensity was reduced in the surface layer within the joint, indicating that both molecules exhibit a mutually exclusive expression pattern. This expression pattern was maintained at E15.0, after formation of the articular space. At E11.0, the quadratosquamosal joint was formed between the quadrate cartilage and squamosal bone, with the perichondrium and periosteum intervening. Collagen type III expression was restricted to the perichondrium within the joint. Meanwhile, tenascin-C expression was detected throughout the perichondrium and peripheral layer of the cartilage, but the expression intensity was reduced within the joint, indicating a mutually exclusive expression pattern also in this joint. At E14.0, the pterygoid-parasphenoid joint was formed between the palatoquadrate cartilage and parasphenoid cartilaginous pad, with a narrow interzone. Immunoreactivity indicative of collagen type III and tenascin-C expression was observed throughout the cartilage area, with regional differences in staining intensity, which also suggests a mutually exclusive expression pattern. These results suggest that interactions between collagen type III and tenascin-C in chick skull are related to joint formation. Mini-abstract Collagen type III and tenascin-C exhibit a mutually exclusive expression pattern in developing joints of chick skull, suggesting that interactions between these molecules are related to joint formation.