Isolation and partial characterization of myogenic cells from mussel larvae in vitro.

The main finding of the present study is the discovery of the possibility of a morphofunctional myogenic differentiation of larval mussel cells in vitro. The shape and extensive cytoskeletal network of the cultured contracting cells mimic largely those of smooth muscle cells in vivo. However, the behavior and protein composition of these cells are not completely identical with those of smooth muscle cells. Contracting mussel cells in vitro, as well as differentiated smooth muscles, demonstrate both phasic and tonic contractions. The paramyosin to myosin ratio in the cultured mussel cells is far less than that in the muscles of veliger larvae and adult mussels. We have found the protein carpets with various adhesive characteristics determine different development pathways. Myogenic differentiation is only observed in spreading cells. Non-spreading adherent cells plated on collagen carpet show high synthetic activity but the commitment of contractile phenotype is inhibited. Our results confirm that the myogenic program established in early embryogenesis of molluscs can be realized during the cultivation of cells from premyogenic larval stages.