Figure 7.

Proposed models of polySia-dependent mechanisms on smooth muscle cells during postnatal development of epididymis [71]. (A) The model is based on studies by Sato and co-workers demonstrating that polySia binds neurotrophins modulating the induction of proliferation [58]. Since polySia was observed on proliferating smooth muscle cells and smooth muscle cells express neurotrophin receptors during postnatal development [72] it was suggested that polySia contributes to the induction of proliferation [71]. (B) With increasing amounts of collagen the polysialylation of smooth muscle cells stops. Based on cell culture experiments in the lab of Curtis showing that collagen induces the internalization of polySia-NCAM and degradation of polySia chains [83], a functional relationship between increasing amount of collagen and decreasing amount of polySia-NCAM was discussed [71].