Study
Fundamentals of planarian regeneration
Reddien, Peter W.; Sánchez Alvarado, Alejandro
Annual Review of Cell and Developmental Biology, 2004
A synthesis of planarian regeneration: the neoblast stem cell population, the establishment of polarity in a regenerating fragment, the classical cutting experiments, and the molecular tools that reopened the field.
- Studied in
- Schmidtea mediterranea, Dugesia
- Sample size
- review of planarian regeneration biology
Planarians regenerate complete animals from small fragments using neoblasts, a population of adult stem cells distributed through the body and the only dividing cells the animal has. A fragment re-establishes head-to-tail polarity correctly, and regeneration proceeds substantially by remodelling existing tissue as well as by building new — the animal rescales rather than only regrowing.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Planarian regeneration rests on a genuinely pluripotent adult stem cell population combined with a system for re-establishing body axes in a fragment.
How NatureHQ reads it
The important comparison is with the axolotl, because the two solve the same problem in opposite ways. A salamander uses lineage-restricted cells that remember what they are, and rebuilds by growing. A planarian uses genuinely pluripotent stem cells and rebuilds substantially by *rescaling* — existing tissue is remodelled into the right proportions for a smaller animal. Those are the two classical categories: epimorphosis, where new tissue is built from a growth zone, and morphallaxis, where existing tissue is repatterned. Knowing that there are two answers is most of what makes the subject a subject rather than a list of impressive animals.
- A review predating much of the single-cell work that has since refined neoblast heterogeneity.
- Species differ substantially in regenerative capacity even within planarians.
- The relationship between neoblast subclasses and specific tissue outcomes was unresolved at the time.
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: Annual ReviewsPublished in an Annual Reviews journal.
doi.org/10.1146/annurev.cellbio.20.010403.095114
This reference was resolved automatically against Crossref on 2026-08-11.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-08-11.