Hyaluronan in morphogenesis.

Pericellular matrices surrounding migrating and proliferating cells in the developing embryo, in regenerating tissues and in other dynamic cellular events, such as tumour cell invasion, are enriched in hyaluronan. In addition to contributing to the unique structure of the pericellular matrix, hyaluronan interacts with cell surface receptors, such as RHAMM and CD44. During morphogenesis, these interactions of hyaluronan with the cell surface are important in several ways. First, hyaluronan-CD44 interactions have been shown to mediate endocytic removal of hyaluronan at critical stages of embryonic development. Secondly, hyaluronan provides an appropriately hydrated, pericellular milieu that facilitates cellular invasion. Thirdly, in-vitro studies suggest strongly that interactions of hyaluronan with RHAMM or CD44 are involved in cell movement and proliferation, which are critical events in morphogenesis.