Planarian regeneration involves distinct stem cell responses to wounds and tissue absence

Abstract

Regeneration requires signaling from a wound site for detection of the wound, and a mechanism that determines the nature of the injury to specify the appropriate regenerative response. Wound signals and tissue responses to wounds that elicit regeneration remain poorly understood. Planarians are able to regenerate from essentially any type of injury and present a novel system for the study of wound responses in regeneration initiation. Newly developed molecular and cellular tools now enable study of regeneration initiation using the planarian Schmidtea mediterranea. Planarian regeneration requires adult stem cells called neoblasts and amputation triggers two peaks in neoblast mitoses early in regeneration. We demonstrate that the first mitotic peak is a body-wide response to any injury and that a second, local, neoblast response is induced only when injury results in missing tissue. This second response was characterized by recruitment of neoblasts to wounds, even in areas that lack neoblasts in the intact animal. Subsequently, these neoblasts were induced to divide and differentiate near the wound, leading to formation of new tissue. We conclude that there exist two functionally distinct signaling phases of the stem cell wound response that distinguish between simple injury and situations that require the regeneration of missing tissue.

Telomere maintenance and telomerase activity are differentially regulated in asexual and sexual worms

“…Control asexual DsRed(RNAi) animals also maintained their telomere length over 57 wk, suggesting a link between telomerase activity and raised levels of pASC proliferation caused by wounding (Fig. 2D) (19). Prolonged Smed-tert(RNAi) led to consistent and steady erosion of average telomere length of ∼290 bp per wk in asexual animals ( Fig.…”

The planarian neoblast: the rambling history of its origin and some current black boxes

“…Indeed, soon after cutting an still unidentified wound-specific signal induces between 2-6 hrs a first mitotic peak by shortening the G2 phase of neoblasts close to the wound (Saló and Baguñà, 1984;Wenemoser and Reddien, 2010). Of note, in the species Schmidtea mediterranea this first mitotic peak occurs allover the organism (Wenemoser and Reddien, 2010). After the first mitotic peak a relative minimum follows at 1 day of regeneration and a they grow again to adult size.…”

“…The blastema, whose cells do not proliferate, increase in size by the continuous entrance at its base of new undifferentiated cells, alike to neoblasts, produced by active cell proliferation in the old stump (postblastema: Baguñà, 1976b;Saló and Baguñà, 1984). Indeed, soon after cutting an still unidentified wound-specific signal induces between 2-6 hrs a first mitotic peak by shortening the G2 phase of neoblasts close to the wound (Saló and Baguñà, 1984;Wenemoser and Reddien, 2010). Of note, in the species Schmidtea mediterranea this first mitotic peak occurs allover the organism (Wenemoser and Reddien, 2010).…”

Changes of alkaline phosphatase activity in response to different stressors in planarian Dugesia japonica

“…Traditionally, they have been used as animal models in stem cell research and in studies of the central nervous system regeneration because of their powerful regenerating ability (Wenemoser et al 2010;Gentile et al 2011). Recently, they have also been used as test organisms in environmental toxicology (Guecheva et al 2003;Pra et al 2005;Li 2008;Alonso et al 2011).…”