Histochemistry of the foetal human temporomandibular joint articular disc.

The human temporomandibular joint (TMJ) develops from mesenchymal cells that form condensations appearing as condylar and temporal blastema which give rise to the respective anterior and posterior regions of the TMJ articular disc. Previous reports have shown the foetal disc to be avascular, with a high content of organized collagen fibres and a lesser content of elastic fibres. In this study, the articular discs from TMJs of a human foetus at age 22 weeks were evaluated. At this stage of intrauterine (i.u.) development, the disc was found to be a highly cellular, biconcave structure with a dense arrangement of collagen fibres. Cell density was not uniform, with increased density in the intermediate band relative to the anterior and posterior bands. In contrast to earlier reports, capillaries containing red blood cells were observed along the inferior surface of the disc. Immunohistochemical staining for proteoglycans and glycosaminoglycans (GAGS) revealed abundant chondroitin sulphate proteoglycan (CSPG) and hyaluronic acid in the disc while relatively little amounts of dermatan sulphate proteoglycan II (DSPGII) were found. No keratin sulphate proteoglycan (KSPG) was detectable. Foetal human TMJ articular discs at this age were found to have morphology and regional characteristics similar to adult discs.