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Slow-cycling stem cells in hydra contribute to head regeneration.

Govindasamy N, Murthy S, Ghanekar Y - Biol Open (2014)

Bottom Line: Intriguingly, hydra does not display consequences of high proliferation, such as senescence or tumour formation.A significant number of undifferentiated cells of all three lineages in hydra retained EdU for about 8-10 cell cycles, indicating that these cells did not enter cell cycle.These results suggest an early evolution of slow-cycling stem cells in multicellular animals.

View Article: PubMed Central - PubMed

Affiliation: Institute for Stem Cell Biology and Regenerative Medicine (inStem), National Centre for Biological Sciences, GKVK Campus, Bellary Road, Bangalore 560065, India.

No MeSH data available.


Related in: MedlinePlus

Identification of label-retaining cells.(A) Label-retaining ectodermal and endodermal epithelial cells at the end of four weeks and 1s/2s interstitial cells at the end of one week. (B) EdU retention was also observed in differentiated cells like gland cells and neurons at the end of four weeks and in 4s nematoblasts at the end of one week of chase. Scale bars: 10 µm.
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f02: Identification of label-retaining cells.(A) Label-retaining ectodermal and endodermal epithelial cells at the end of four weeks and 1s/2s interstitial cells at the end of one week. (B) EdU retention was also observed in differentiated cells like gland cells and neurons at the end of four weeks and in 4s nematoblasts at the end of one week of chase. Scale bars: 10 µm.

Mentions: Hydra were simultaneously macerated to identify the cell types that retained label, as described (David, 1973). The cells retaining label were defined as those which had EdU signal that completely colocalized with signal from DAPI staining of nuclear DNA. Cells with partial/punctate EdU signal were not considered to be label-retaining cells since dilution of signal indicates that cells have undergone cell division (supplementary material Fig. S1B). The morphology of label-retaining nuclei and cells was normal (Fig. 2). After one week of pulse, the labelling index of interstitial cells was approximately 94–98%. The labelling index of epithelial cells was much lower; the labelling index of ectodermal epithelial cells varied between 54–80% and that of endodermal cells varied between 41–56% (Table 1). The labelling index was not 100% in any cell lineage indicating lack of cell division in a substantial number of cells, especially in the epithelial lineages. The fact that a fraction of stem cells of all lineages remained undivided suggested that morphologically similar cells indeed display variation in the frequency of cell division and not all cells in hydra undergo incessant cell division. A longer pulse of four weeks was also performed to determine if this time of pulse is sufficient to label all cells capable of undergoing cell division. Upon longer pulse of four weeks, the labelling index increased; all 1s and 2s interstitial cells were completely labelled. The labelling index of ectodermal and endodermal epithelial cells was >90% but not 100%, indicating that a few epithelial cells remained undivided even after 4 weeks (Table 1). A similar labelling index was also observed when regenerating aggregates of hydra were pulsed with EdU. The aggregates of dissociated single cells (Gierer et al., 1972) were pulsed with EdU from the time aggregates were generated until hydranths developed and fell off the aggregate (data not shown). Long pulse with EdU, of both whole animals and developing aggregates, however adversely affected hydra which showed defects such as slow rate of budding and tentacle formation. Subsequent studies were therefore performed with one week pulse.


Slow-cycling stem cells in hydra contribute to head regeneration.

Govindasamy N, Murthy S, Ghanekar Y - Biol Open (2014)

Identification of label-retaining cells.(A) Label-retaining ectodermal and endodermal epithelial cells at the end of four weeks and 1s/2s interstitial cells at the end of one week. (B) EdU retention was also observed in differentiated cells like gland cells and neurons at the end of four weeks and in 4s nematoblasts at the end of one week of chase. Scale bars: 10 µm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4265762&req=5

f02: Identification of label-retaining cells.(A) Label-retaining ectodermal and endodermal epithelial cells at the end of four weeks and 1s/2s interstitial cells at the end of one week. (B) EdU retention was also observed in differentiated cells like gland cells and neurons at the end of four weeks and in 4s nematoblasts at the end of one week of chase. Scale bars: 10 µm.
Mentions: Hydra were simultaneously macerated to identify the cell types that retained label, as described (David, 1973). The cells retaining label were defined as those which had EdU signal that completely colocalized with signal from DAPI staining of nuclear DNA. Cells with partial/punctate EdU signal were not considered to be label-retaining cells since dilution of signal indicates that cells have undergone cell division (supplementary material Fig. S1B). The morphology of label-retaining nuclei and cells was normal (Fig. 2). After one week of pulse, the labelling index of interstitial cells was approximately 94–98%. The labelling index of epithelial cells was much lower; the labelling index of ectodermal epithelial cells varied between 54–80% and that of endodermal cells varied between 41–56% (Table 1). The labelling index was not 100% in any cell lineage indicating lack of cell division in a substantial number of cells, especially in the epithelial lineages. The fact that a fraction of stem cells of all lineages remained undivided suggested that morphologically similar cells indeed display variation in the frequency of cell division and not all cells in hydra undergo incessant cell division. A longer pulse of four weeks was also performed to determine if this time of pulse is sufficient to label all cells capable of undergoing cell division. Upon longer pulse of four weeks, the labelling index increased; all 1s and 2s interstitial cells were completely labelled. The labelling index of ectodermal and endodermal epithelial cells was >90% but not 100%, indicating that a few epithelial cells remained undivided even after 4 weeks (Table 1). A similar labelling index was also observed when regenerating aggregates of hydra were pulsed with EdU. The aggregates of dissociated single cells (Gierer et al., 1972) were pulsed with EdU from the time aggregates were generated until hydranths developed and fell off the aggregate (data not shown). Long pulse with EdU, of both whole animals and developing aggregates, however adversely affected hydra which showed defects such as slow rate of budding and tentacle formation. Subsequent studies were therefore performed with one week pulse.

Bottom Line: Intriguingly, hydra does not display consequences of high proliferation, such as senescence or tumour formation.A significant number of undifferentiated cells of all three lineages in hydra retained EdU for about 8-10 cell cycles, indicating that these cells did not enter cell cycle.These results suggest an early evolution of slow-cycling stem cells in multicellular animals.

View Article: PubMed Central - PubMed

Affiliation: Institute for Stem Cell Biology and Regenerative Medicine (inStem), National Centre for Biological Sciences, GKVK Campus, Bellary Road, Bangalore 560065, India.

No MeSH data available.


Related in: MedlinePlus