PRODUCTION OF SCHISTOSOMA-MANSONI DAUGHTER SPOROCYSTS FROM MOTHER SPOROCYSTS MAINTAINED IN SYNXENIC CULTURE WITH BIOMPHALARIA-GLABRATA EMBRYONIC (BGE) CELLS

In vitro production of Schistosoma mansoni daughter sporocysts (DS) fr om miracidium-derived mother sporocysts (MS) was achieved by synxenic larval cultivation with cells of the Biomphalaria glabrata embryonic ( Bge) cell line. The in vitro growth and viability of MS cocultured wit h Bge cells or in Bge cell-conditioned medium were significantly exten ded beyond that of larvae cultured in fresh medium alone. However, com plete DS development and emergence from MS were achieved only in the p resence of Bge cells. Introduction of either miracidia or previously t ransformed MS onto Bge cell monolayers resulted in an initial attachme nt of cultured cells to sporocysts, followed by a gradual encapsulatio n of larvae by multiple layers of Bge cells. Sporocysts and their enca psulating cells eventually formed large cellular aggregates, within wh ich MS increased 4-fold in size during the first 20 days of cultivatio n. The timing of in vitro DS development was somewhat variable; howeve r, in general, early embryo formation, i.e., germ cell aggregates with surrounding primitive epithelium, was first detected at 15-20 days of culture, whereas motile, intra-MS daughter stages were seen at 25-30 days and thereafter. Mature, first generation DS, measuring 136 +/- 46 mu m long by 22 +/- 6 mu m wide, emerged from MS starting at approxim ately 30-45 days of initial cultivation. Although the basic morphology and size of emergent, in vitro-derived DS were comparable to those pr opagated in vivo, there was a large reduction in the in vitro reproduc tive capacity of the MS and a delay in DS culture development. Bge cel ls provided an acceptable physiological and physical environment for i n vitro MS-to-DS development, although conditions optimal for sporocys t growth and those permitting continued DS-to-cercarial stage formatio n have yet to be defined.