Consequences of Reduced Versican Expression in Embryonic Chick Synovial Joint Development

Abstract

The different mechanisms involved in vertebrate synovial joint development are actively being uncovered. A variety of studies have thus far discovered the involvement of several large molecules in the processes of joint development and cavitation. Such molecules include glycosaminoglycans, glycoproteins, proteoglycans, growth factors, and adhesive molecules. The coordinated spatiotemporal expressions of these molecules, among them chondroitin-sulfate proteoglycans (CSPG), are believed to play a crucial role in synovial joint formation. A previous study has shown that isoforms of the CSPG versican are abundantly expressed in the developing chick synovial joint during progressive stages of embryonic development (Shepard et al. 2007). The purpose of this study is to better understand the importance of versican in the developing limb joints by inhibiting its expression. We employed adenoviral-mediated RNA interference and inovo microinjection techniques to knock down endogenous versican protein levels. Results show an average reduction of 14% in the non-chondrogenic space of the joint interzone of day 10 embryos in response to versican knockdown that was coupled with attenuated expressions of key versican associating molecules such as hyaluronan, tenascin, CD44 and link protein. Impacts of versican knockdown also resulted in lowered collagen II expression among articular chondrocytes implying possible delays in chondrogenesis, or early transition toward an osteogenic fate.