In vitro sexual dimorphism establishment in schistosomes

Schistosomes are parasitic flatworms responsible for the neglected tropical disease Schistosomiasis, which affects over 250 million individuals worldwide. Unlike most flatworms, schistosomes exhibit sexual dimorphism with female (ZW) and male (ZZ) sexes only becoming apparent during adulthood in the mammalian host. The cellular and molecular mechanisms behind this sexual differentiation remain poorly understood due to difficulties in assessing parasite development in vivo.

Researchers have sought robust, reproducible in vitro methods to maintain and develop schistosomes, but few studies have succeeded in producing sexually dimorphic stages, and none have been reliably reproduced. This lack of progress hinders efforts to understand the sexual biology of this significant human parasite.

In a new study, scientists refined a protocol for long-term culture of newly transformed cercariae in vitro. The researchers tested the impact of adding two different sera, foetal bovine serum (FBS) and human serum (HS), to the culture medium containing red blood cells. Cultured parasites in human serum showed clear sexual dimorphism, although the development was delayed compared to those in FBS.

Moreover, cells within the human serum-cultured parasites continuously proliferated in EdU-pulse experiments, while fewer proliferated in FBS-culture.

By providing a reliable protocol for in vitro development of schistosomes, this research opens new avenues for studying the mechanisms behind sexual dimorphism and screening potential interventions across the parasite's life cycle.