CELLULAR ASPECTS OF THE DEVELOPMENT OF DIARTHRODIAL JOINTS AND ARTICULAR-CARTILAGE

There have been many reports on the histological development of mammal ian diarthrodial or synovial joints. While these are useful for compar ative purposes, they tell us little of the cellular basis of joint mor phogenesis which must underlie a number of morphogenetic defects. The process of joint morphogenesis is complex and can be subdivided into a number of facets and this report will focus on 2 of them. First, the process of joint cavitation in the chick metatarsophalangeal joint, wh ere we propose that the selective secretion of hyaluronan into the pre sumptive cavity plays a central role. Secondly, the development of art icular cartilage where we have used the South American opossum Monodel phis domestica as a model for mammalian development. Like most marsupi als, the young are born at a much earlier developmental stage than eut herian mammals. Using antibodies which detect proliferating chondrocyt es and those synthesising insulin-like growth factors 1 and 2 and insu lin-like growth factor 1 binding protein, we report that the majority of growth (as assessed by these indicators) appears appositional.