Cell repertoire and proliferation of germinative cells of the model cestode Mesocestoides corti.

The phylum Platyhelminthes shares a unique population of undifferentiated cells responsible for the proliferation capacity needed for cell renewal, growth, tissue repair and regeneration. These cells have been extensively studied in free-living flatworms, whereas in cestodes the presence of a set of undifferentiated cells, known as germinative cells, has been demonstrated in classical morphology studies, but poorly characterized with molecular biology approaches. Furthermore, several genes have been identified as neoblast markers in free-living flatworms that deserve study in cestode models. Here, different cell types of the model cestode Mesocestoides corti were characterized, identifying differentiated and germinative cells. Muscle cells, tegumental cells, calcareous corpuscle precursor cells and excretory system cells were identified, all of which are non-proliferative, differentiated cell types. Besides those, germinative cells were identified as a population of small cells with proliferative capacity in vivo. Primary cell culture experiments in Dulbecco's Modified Eagle Medium (DMEM), Echinococcus hydatid fluid and hepatocyte conditioned media in non-reductive or reductive conditions confirmed that the germinative cells were the only ones with proliferative capacity. Since several genes have been identified as markers of undifferentiated neoblast cells in free-living flatworms, the expression of pumilio and pL10 genes was analysed by qPCR and in situ hybridization, showing that the expression of these genes was stronger in germinative cells but not restricted to this cell type. This study provides the first tools to analyse and further characterise undifferentiated cells in a model cestode.