Fundamentals of planarian regeneration.

@article{Reddien2004FundamentalsOP,
  title={Fundamentals of planarian regeneration.},
  author={Peter W. Reddien and Alejandro S{\'a}nchez Alvarado},
  journal={Annual review of cell and developmental biology},
  year={2004},
  volume={20},
  pages={
          725-57
        }
}
The principles underlying regeneration in planarians have been explored for over 100 years through surgical manipulations and cellular observations. Planarian regeneration involves the generation of new tissue at the wound site via cell proliferation (blastema formation), and the remodeling of pre-existing tissues to restore symmetry and proportion (morphallaxis). Because blastemas do not replace all tissues following most types of injuries, both blastema formation and morphallaxis are needed… Expand
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Whether the actions of elements of the bone morphogenetic protein (BMP), Wnt, and fibroblast growth factor (FGF) pathways that control patterning and axial polarity during planarian regeneration and homeostasis could be based on Morphogenetic gradients is discussed. Expand
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TLDR
An overview of planarians as a model system for research into development and regeneration is provided and new lines of investigation in this area are described. Expand
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TLDR
A "target-blind" model for planarian regeneration is suggested in which progenitor production by neoblasts does not depend on feedback from the presence or absence of specific target tissues to be regenerated. Expand
Stem cell-based growth, regeneration, and remodeling of the planarian intestine.
TLDR
The results indicate that growth and regeneration of the planarian intestine are achieved by co-ordinated differentiation of stem cells and the remodeling of pre-existing tissues. Expand
Tissue transplantation in planarians: A useful tool for molecular analysis of pattern formation.
TLDR
The different grafting approaches used in planarians, and the corresponding intercalary regenerative response, are discussed, placing particular emphasis on the respective contributions of donor and host tissue. Expand
Regenerative tissue remodeling in planarians - The mysteries of morphallaxis.
  • J. Pellettieri
  • Biology, Medicine
  • Seminars in cell & developmental biology
  • 2019
TLDR
Some of the key features of regenerative tissue remodeling, including repatterning of the body axes, reproportioning of organs like the brain and gut, and a major increase in the rate of cell death are revealed. Expand
Planarian regeneration involves distinct stem cell responses to wounds and tissue absence.
TLDR
It is demonstrated 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. Expand
Restoration of anterior regeneration in a planarian with limited regenerative ability
TLDR
Examining Procotyla fluviatilis, a planarian with restricted ability to replace missing tissues, is examined, finding that Wnt signalling is aberrantly activated in regeneration-deficient tissues and manipulating a single signalling pathway can reverse the evolutionary loss of regenerative potential. Expand
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References

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Intercalary regeneration in planarians
TLDR
This work proposes a new interpretation, i.e., that the blastema may work as a signaling center inducing intercalary regeneration, and introduces the intercalation induced by ectopic grafting along the anteroposterior, dorsoventral, and left–right (L‐R) axes. Expand
Regeneration and pattern formation in planarians III . Evidence that neoblasts are totipotent stem cells and the source of blastema cells
In most regenerating systems, blastema cells arise by dedifferentiation of functional tissue cells. In planarians, though, it is still debatable whether dedifferentiated cells or a population ofExpand
Regeneration and pattern formation in planarians. III. that neoblasts are totipotent stem cells and the cells
TLDR
This work describes a new approach to these problems regenerative and stem cell capabilities of purified differentiated cells when introduced, separately, into hosts. Expand
Epimorphic regeneration of the distal part of the planarian pharynx
TLDR
It is shown that the regeneration after amputation of the distal part of the pharynx is an 'epimorphic' process, based on conventional histochemical observations and observations of the regeneration process of planarians irradiated with X-rays in particular regions. Expand
Bromodeoxyuridine specifically labels the regenerative stem cells of planarians.
TLDR
The ability to label specifically the regenerative stem cells, combined with the recently described use of double-stranded RNA to inhibit gene expression in the planarian, should serve to reignite interest in the flatworm as an experimental model for studying the problems of metazoan regeneration and the control of stem cell proliferation. Expand
The process of pharynx regeneration in planarians.
TLDR
Interestingly, cells expressing the pharynx-muscle-specific myosin heavy chain gene (DjMHC-A) appeared within 24 h after amputation in the mesenchymal space of the stump, not in the blastema region. Expand
Dissecting planarian central nervous system regeneration by the expression of neural‐specific genes
TLDR
The results from this study show that the comparison of the expression patterns of different neural genes supports the view that at day one of regeneration, the new brain appears within the blastema, whereas the pre‐existing ventral nerve cords remain in the old tissues. Expand
The use of planarians to dissect the molecular basis of metazoan regeneration
  • A. S. Alvarado, P. Newmark
  • Biology, Medicine
  • Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society
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TLDR
The objective of this article is to present a molecular strategy to identify and functionally manipulate genes involved in the process of blastema‐derived regeneration and define a series of useful molecular templates that may help unravel the more complex epigenetic processes of vertebrate regeneration. Expand
Electron microscopic studies of planarian regeneration. III. Degeneration and differentiation of muscles
TLDR
Planarians were surgically decapitated, and morphological changes in their muscles during regeneration were studied with the electron microscope, finding no evidence of de- and redifferentiation of preexisting muscle cells. Expand
Cell movement in intact and regenerating planarians. Quantitation using chromosomal, nuclear and cytoplasmic markers.
TLDR
It is concluded that the so-called 'migration' of neoblasts is not a true cell migration but the result of the slow, even and progressive spreading of these cells mainly caused by random movements linked to cell proliferation. Expand
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