# Rejuvenation, Regeneration and Aging **URL:** \ **Category:** General\ **Created:** [May 25, 2025, 9:53am UTC](https://www.rapamycin.news/t/rejuvenation-regeneration-and-aging/20015 "2025-05-25T09:53:17Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![John\_Hemming](https://www.rapamycin.news/user_avatar/www.rapamycin.news/john_hemming/32/6542_2.png) [@John\_Hemming](https://www.rapamycin.news/u/John_Hemming)\ **Post date:** [May 25, 2025, 9:53am UTC](https://www.rapamycin.news/t/rejuvenation-regeneration-and-aging/20015/1 "2025-05-25T09:53:17Z")
I asked chatGPT for an analysis of the links between Regeneration, Rejuvenation and Aging. This was the result: **Short answer:** It depends on the animal. Some species never seem to lose their regenerative super-powers, some keep them but the process slows with age, and in a few (including most mammals) the capacity is switched off very early in life. * * * ### 1. Species that keep regeneration for life | Group | Typical examples | What we know about ageing & regeneration | Key references | | --- | --- | --- | --- | | _Basal invertebrates_ | **Hydra** (fresh-water polyp) | Stem-cell–driven self-renewal is continuous; mortality and fertility curves stay flat for years, implying no age-related decline in regeneration at all. | ([PNAS](https://www.pnas.org/doi/10.1073/pnas.1521002112?utm_source=chatgpt.com "Constant mortality and fertility over age in Hydra - PNAS"), [ScienceDirect](https://www.sciencedirect.com/science/article/pii/S0022519315003227?utm_source=chatgpt.com "Unraveling the non-senescence phenomenon in Hydra")) | | _Flatworms_ | **Planarians** (e.g. _Schmidtea mediterranea_) | Even “old” planarians still rebuild an entire body from a tiny fragment. Recent work shows that a round of regeneration can actually _rejuvenate_ aging tissues. | ([Nature](https://www.nature.com/articles/s43587-025-00847-9?utm_source=chatgpt.com "Regeneration leads to global tissue rejuvenation in aging sexual ...")) | | _Urodele amphibians_ | **Mexican axolotl, newts** | Axolotls regenerate limbs, tail, spinal cord and even parts of the brain throughout a 10- to 15-year lifespan; repeated amputations in very old newts do not measurably reduce success, only slow the timetable a little. | ([Financial Times](https://www.ft.com/content/a1f83886-fb29-4f5f-9577-bec61dfd31d2?utm_source=chatgpt.com "Scientists make breakthroughs on blood ageing and limb regrowth"), [PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC3144589/?utm_source=chatgpt.com "Regenerative capacity in newts is not altered by repeated ...")) | * * * ### 2. Lifelong but _slowing_ regeneration | Group | Example tissues regenerated | Age-related changes | | | --- | --- | --- | --- | | **Teleost fish** (zebrafish) | Fins, heart, retina | Old zebrafish still regenerate but cardiomyocytes show replication-stress and the process takes longer. | ([Nature](https://www.nature.com/articles/s41467-025-56993-6?utm_source=chatgpt.com "BMP signaling promotes zebrafish heart regeneration via alleviation ...")) | | **Reptiles** (most lizards) | Tail | Older lizards regrow tails more slowly and the cartilage tube is often thinner, but the capacity itself is retained. | ([PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC4895314/?utm_source=chatgpt.com "The regeneration blastema of lizards: an amniote model for the ...")) | | **Spiny mouse** (_Acomys_) | Skin, ear cartilage, skeletal muscle | Adults of all ages regenerate with little scarring; very aged animals complete ear-hole closure more slowly and sometimes incompletely. | ([ResearchGate](https://www.researchgate.net/publication/384834689_Older_spiny_mice_Acomys_cahirinus_have_delayed_and_spatially_heterogenous_ear_wound_regeneration?utm_source=chatgpt.com "Older spiny mice ( Acomys cahirinus ) have delayed and spatially ...")) | Why the slowdown? Common themes are stem-cell DNA damage, epigenetic drift, and changes in the immune milieu that turn injuries from pro-regenerative to pro-scar-forming environments. ([Nature](https://www.nature.com/articles/s41467-025-56993-6?utm_source=chatgpt.com "BMP signaling promotes zebrafish heart regeneration via alleviation ...")) * * * ### 3. Regeneration that is _switched off early_ | Species (mammals) | What they can regenerate | When the window closes | | | --- | --- | --- | --- | | Mouse heart | Full-thickness ventricular apex | Day 1 neonates regenerate; by day 7 the same injury scars instead of regrowing muscle. | ([PubMed](https://pubmed.ncbi.nlm.nih.gov/21350179/?utm_source=chatgpt.com "Transient regenerative potential of the neonatal mouse heart")) | | Human fingertips | Distal phalanx in children | The ability fades around puberty; adults generally scar. (Clinical literature, no loss-of-function genes identified yet.) | | | Most other mammalian tissues | Skin, liver, etc. | Capacity declines steadily with age because resident stem-cell pools shrink and become senescent. | | Mechanistically, mammals restrict regeneration partly to guard against cancer: tumour-suppressor pathways (e.g., p16^Ink4a^) ramp up quickly after birth and curb the cell-cycle re-entry that true epimorphic regeneration demands. ([PubMed](https://pubmed.ncbi.nlm.nih.gov/21350179/?utm_source=chatgpt.com "Transient regenerative potential of the neonatal mouse heart")) * * * ### 4. Putting it together - **No-loss species** (Hydra, many planarians) couple continuous stem-cell cycling to strong genomic maintenance, so regeneration and “non-ageing” go hand-in-hand. - **Slow-down species** (zebrafish, lizards, spiny mice) maintain the genetic programmes but accumulate enough molecular and immunological “noise” that each round of repair is just a bit less efficient. - **Early-loss species** (most mammals) silence the programme entirely once development is complete, probably as an anti-cancer trade-off. So the answer is **not universal** : whether a regenerating species loses that ability—and if so, when—depends on how its stem-cell biology, immune system and cancer suppression have been balanced over evolution. ---
**Author:** ![John\_Hemming](https://www.rapamycin.news/user_avatar/www.rapamycin.news/john_hemming/32/6542_2.png) [@John\_Hemming](https://www.rapamycin.news/u/John_Hemming)\ **Post date:** [May 25, 2025, 9:53am UTC](https://www.rapamycin.news/t/rejuvenation-regeneration-and-aging/20015/2 "2025-05-25T09:53:46Z")
The reason I think it is relevant is because I think regenerative abilities link to mitochondrial membrane potential. ---
**Author:** ![starspawn0](https://www.rapamycin.news/user_avatar/www.rapamycin.news/starspawn0/32/5876_2.png) [@starspawn0](https://www.rapamycin.news/u/starspawn0)\ **Post date:** [February 2, 2026, 1:05am UTC](https://www.rapamycin.news/t/rejuvenation-regeneration-and-aging/20015/3 "2026-02-02T01:05:13Z")
Interesting short video about new findings on how flatworms regenerate: [![](https://img.youtube.com/vi/zYKVq8rBEqg/maxresdefault.jpg "Scientists Discover Why Flatworms are 'Immortal'") ](https://www.youtube.com/watch?v=zYKVq8rBEqg) > Planarian flatworms regenerate their entire bodies using signals from distant intestinal cells, challenging the long-held belief that stem cells are regulated only by their immediate neighbors. This discovery reveals a complex network of long-range cellular communication that could transform regenerative medicine approaches. > **[“Immortal” flatworm rewrites the science of healing](https://www.sciencedaily.com/releases/2025/10/251029100156.htm)** > > Flatworms can rebuild themselves from just a small fragment, and now scientists know why. Their stem cells ignore nearby instructions and respond to long-distance signals from other tissues. This discovery turns old stem cell theories upside down and... If use of stem cells to repair tissue works anything like this in humans, then it may be suggests that intestinal cells are somehow involved – even when it comes to tissues far-removed from the intestines.