Small coelomic epithelial cells of the starfish Asterias rubens L. that are able to proliferate in vivo and in vitro

Abstract

Echinoderms, due to their outstanding potential for regeneration, are widely used as experimental models for research in regenerative biology. One of the main problems in this field concerns identification and characterization of cells responsible for the restoration of lost body parts and organs in adult animals. In this study, we analyze the probable candidates for this role in the starfish Asterias rubens L., namely, small coelomic epithelial cells with a high nuclear-cytoplasmic ratio that have the ability to proliferate. These cells are one of several cell types common to the coelomic epithelium (CE) and coelomic fluid (CF). They are analyzed with respect to morphology, proportion in the total cell pool, dynamics after injury and distribution between CE and CF. The results of whole-mount and scanning electron microscopy provide evidence that these small cells occupy a boundary position between CE and CF. Moreover, a novel subpopulation of CE cells is identified that is enriched (up to 50 %) with small epitheliocytes capable of migrating from CE into the CF. As shown in experiments with BrdU incorporation and anti-phospho-histone H3 antibody staining, small epitheliocytes cultured on laminin retain proliferative activity for at least 1 month and can form colony-like aggregates. Two types of small proliferating cells are distinguished by their behavior in culture: some cells remain attached to the substrate and form aggregates, while others detach from the substrate during culturing. The morphology of small epitheliocytes, their proliferative activity in vivo and in vitro and the ability to migrate suggest that they possess certain properties characteristic of stem cells.

A combined characterization of coelomic fluid cell types in the spiny starfishMarthasterias glacialis– inputs from flow cytometry and imaging

“…In line with our proposal, P1L has been suggested as the progenitor of the circulating cells (14), since they displayed no signs of differentiation and constituted 50% of the weakly attached CE cells (27). Both CE cell types showed incorporation of BrdU, although in the coelomic fluid only the cells with smaller nucleus to cytoplasm ratio presented the same BrdU-positive feature (27). P1S properties, such as proliferative activity, undifferentiated cell morphotype, ability to migrate and presence of euchromatin, are also exhibited by other animals' stem cells (i.e.…”

“…Based on this observation, we would like to suggest that this last cell type (P1L) corresponds to a non-differentiated form of the other more mature first cell type (P1S). In line with our proposal, P1L has been suggested as the progenitor of the circulating cells (14), since they displayed no signs of differentiation and constituted 50% of the weakly attached CE cells (27). Both CE cell types showed incorporation of BrdU, although in the coelomic fluid only the cells with smaller nucleus to cytoplasm ratio presented the same BrdU-positive feature (27).…”

“…rubens after staining with azure-eosin (27). In both studies these cells were detected in the coelomic fluid or included in the coelomic epithelium.…”

“…The higher forward scatter determined for P2 cells (see above), compared to P1, is justified by a more complex internal cellular architecture. According to Sharlaimova and collaborators (27); (35) P2 cells incorporate BrdU suggesting their proliferative activity in vivo. Despite the similar cell size distribution and similar nucleus/cytoplasm diameter ratio, morphological heterogeneity has been observed within this population.…”

Expression of stem cell factors in the adult sea cucumber digestive tube

“…Expression of stem cell markers in this cell type corroborates earlier observations that clearly demonstrated plasticity of this cell type in the context of post-tramatic regeneration. Peritoneal cells reacted to injury by undergoing extensive dedifferentiation and were capable of giving rise not only to other peritoneocytes, but also to muscle cells and even to the cells of the luminal epithelium and coelomic fluid (Mashanov et al, 2005; García-Arrarás and Dolmatov, 2010; Mashanov and García-Arrarás, 2011; Sharlaimova et al, 2014). …”