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Under physiological conditions, the complex planarian neoblast system is a composite of hierarchically organized stem cell sub-populations with sigma-class neoblasts, including clonogenic neoblasts, endowed with larger self-renewal and differentiation capabilities, thus generating all the other sub-populations and dominating the regenerative process. This complex system responds to differentiated tissue demands, ensuring a continuous cell turnover in a way to replace aged specialized cells and maintain tissue functionality. Potency of the neoblast system can be appreciated under challenging conditions in which these stem cells are massively depleted and the few remaining repopulate the entire body, ensuring animal resilience. These challenging conditions offer the possibility to deepen the relationships among different neoblast sub-populations, allowing to expose uncanonical properties that are negligible under physiological conditions. In this paper, we employ short, sub-lethal 5-fluorouracil treatment to specifically affect proliferating cells passing through the S phase and demonstrate that S-phase slowdown triggers a shift in the transcriptional profile of sigma neoblasts, which reduces the expression of their hallmark sox-P1 . Later, some cells reactivate sox-P1 expression, suggesting that some neoblasts in the earlier steps of commitment could modulate their expression profile, reacquiring a wider differentiative potential.

Background Information: Planarians are a sound, well-established model system for molecular studies in the field of stem cells, cell differentiation, developmental biology and translational research. Treated stem cell-less planarians produced by X-ray treatment are commonly used to study stem cell transcriptional profile and their role in planarian biological processes. X-ray induces oxidative and DNA damage to differentiated cells, requires expensive radiation machines that are not available in most of the research centres and demand rigorous risk management and dedicated staff., Results: We tested the use of the well-known antimetabolite genotoxic drug 5-fluorouracil which mainly affects proliferating cells in way to demonstrate its use in replacing X-ray treatment. We succeeded in demonstrating ability of high doses of 5-fluorouracil to deplete Dugesia japonica stem cells and in identifying a 5-fluorouracil transiently resistant population of lineage committed stem cells., Conclusions and Significance: Our results encourage the use of 5-fluorouracil-treated planarians as a model system for studying mechanisms of resistance to genotoxicants, planarian stem cell heterogeneity and molecular cascades of tissue aging., (© 2020 Société Française des Microscopies and Société de Biologie Cellulaire de France. Published by John Wiley & Sons Ltd.)

Microtubule-associated 1B (MAP1B) proteins are expressed at the nervous system level where they control cytoskeleton activity and regulate neurotransmitter release. Here, we report about the identification of a planarian MAP1B factor (DjMap1B) that is enriched in cephalic ganglia and longitudinal nerve cords but not in neoblasts, the plentiful population of adult stem cells present in planarians, thanks to which these animals can continuously cell turnover and regenerate any lost body parts. DjMap1B knockdown induces morphological anomalies in the nervous system and affects neoblast commitment. Our data put forward a correlation between a MAP1B factor and stem cells and suggest a function of the nervous system in non-cell autonomous control of planarian stem cells. [ABSTRACT FROM AUTHOR]

Gravity alterations elicit complex and mostly detrimental effects on biological systems. Among these, a prominent role is occupied by oxidative stress, with consequences for tissue homeostasis and development. Studies in altered gravity are relevant for both Earth and space biomedicine, but their implementation using whole organisms is often troublesome. Here we utilize planarians, simple worm model for stem cell and regeneration biology, to characterize the pathogenic mechanisms brought by artificial gravity alterations. In particular, we provide a comprehensive evaluation of molecular responses in intact and regenerating specimens, and demonstrate a protective action from the space‐apt for nanotechnological antioxidant cerium oxide nanoparticles. [ABSTRACT FROM AUTHOR]

Owing to the self-renewing reactive oxygen species scavenger capability of cerium oxide nanoparticles (nanoceria), we tested in vivo radioprotective effects on stem cells and tissue regeneration using low-dose irradiated planarians as model system. We treated planarians with nanoceria or gum Arabic, as control, and we analyzed the expression of stem cell molecular markers and tissue regeneration capability, as well as cell death and DNA damage in non-irradiated and in low-dose irradiated animals. Our findings show that nanoceria increase the number of stem cells and tissue regenerative capability, and reduce cell death and DNA damage after low-dose irradiation, suggesting a protective role on stem cells. Unlabelled Image • Cerium oxide nanoparticles (nanoceria) show radioprotective effects on stem cells and in tissue regeneration in planarians. • Nanoceria increase the number of stem cells and tissue regenerative capability. • Nanoceria reduce cell death and DNA damage after low-dose irradiation. • Obtained data represent a relevant step towards a translational application of nanoceria. [ABSTRACT FROM AUTHOR]