J Appl Biomed 2:21-35, 2004

The significance of stem cells in free-living flatworms: one common source for all cells in the adult

Roland Peter^1,*, Robert Gschwentner², Wolfgang Schürmann¹, Reinhard M. Rieger², Peter Ladurner²

¹ Department of Genetics and General Biology, University of Salzburg, Salzburg, Austria

² Department of Zoology and Limnology, University of Innsbruck, Innsbruck, Austria

A survey of the current knowledge on stem cells and cell proliferation in turbellarians is presented, with special focus on recent results obtained by the authors when studying cell kinetics and cultivating neoblasts from various species. Differentiated somatic cells do not divide in flatworms. In these animals neoblasts constitute a proliferative compartment. These cells are rather uniform when viewed through a light microscope, but constitute a heterogeneous population comprising actual stem cells, progenitors and early differentiation stages. Cell kinetics were monitored by the incorporation of 5-bromo-2'-deoxyuridine and by immunocytochemical staining for mitoses in the marine microturbellarians Macrostomum, Microstomum and Convolutriloba. Distribution patterns of proliferating cells within the body were documented, and a tentative interpretation of the differences observed is given. Correlations to the nervous system and the mode of reproduction seem to exist. To analyse neoblasts quantitatively and establish primary cultures, neoblasts from the freshwater planarians (triclads) Dugesia and Schmidtea were isolated, purified and subjected to various culture conditions, with the ultimate but not yet achieved goal of establishing a permanent stem cell line. The role of stem cells in flatworms is compared with the situation in mammals, with special focus on embryogenesis, germline and strategies of cell renewal.

Keywords: BrdU labelling; cell cultures; cell proliferation; neoblasts; germline; stem cells

Received: October 24, 2003; Published: March 31, 2004  Show citation