Schistosoma japonicum: in vitro cultivation of miracidium to daughter sporocyst using a Biomphalaria glabrata embryonic cell line.

In vitro cultivation of Schistosoma japonicum miracidia to the mother sporocyst (MS) and then to the daughter sporocyst (DS) stage was achieved using the Biomphalaria glabrata embryonic (Bge) cell line as a coculture system. When comparing the effect of Bge cell and MS density on MS development, it was apparent that Bge cell density had a highly significant effect on both MS viability and growth. Viability and growth rate of MS cultured under high cell density conditions (350 cells/mm2) were almost 2 times greater than those of MS cultured under conditions of low cell density (60 cells/mm2). Growth under high cell density conditions corresponded to a 20 to 30 times increase in MS estimated volume within the first 9 weeks of cultivation. Emergence of fully formed motile DS was first observed after 11 weeks of cocultivation. A few DS lived for 14 weeks after emergence and attained a size of 770 +/- 100 microns in length and 48 +/- 13 microns in width. In contrast to what was observed in Bge cell/Schistosoma mansoni cocultures, Bge cells did not encapsulate S. japonicum MS. Our results show that, although the cellular interactions between Bge cells and schistosomes MS display some level of specificity, Bge cells apparently secrete soluble factors that permit excellent survival and can trigger advanced in vitro development of S. japonicum.