Axolotl Limb Blastema: Regeneration & Positional Patterning

Amputation Level

Signalling

FGF (blastema growth rate) 100%

Wnt/β-catenin (dedifferentiation) 100%

BMP (redifferentiation timing) 100%

Regeneration Status

Wound healing…

Days post-amputation

0.0

Blastema cells

Limb length regenerated

How it works

After amputation, dermis and muscle fibroblasts near the wound re-enter the cell cycle and dedifferentiate into a mass of multipotent progenitors — the blastema — rather than forming scar tissue as in mammals. Blastema growth follows logistic proliferation with signalling-dependent rate and capacity:

dB/dt = r·B·(1 − B/K) − δ·B
r = r0 · (FGF/100)         — FGF sets the proliferation rate
K = K0 · (Wnt/100)         — Wnt/β-catenin sets how many wound
                              cells dedifferentiate (blastema size cap)
δ = δ0 · (BMP/100)         — BMP drives cell-cycle exit into
                              redifferentiation, depleting the pool

Outgrowth of new limb length tracks the proliferating blastema mass, slowing as the target length is approached:

dL/dt = k · (B/K) · (1 − L/Ltarget)

As the growth front advances, connective-tissue fibroblasts carry positional memory — a HOX9–HOX13 gradient recording distance from the body — so each newly laid segment differentiates into the tissue appropriate for its position along the proximodistal axis:

Stylopod (near shoulder) — upper-arm bone and muscle
Zeugopod (mid-limb) — paired forearm bones
Autopod (wrist) — carpal elements
Digits — pattern last, at the distal tip, once outgrowth completes

Lineage tracing shows dedifferentiated muscle re-forms muscle and dedifferentiated fibroblasts re-form connective tissue — cells re-enter the cycle but stay largely restricted to their own lineage rather than trans-differentiating. Real-world relevance: identifying why mammalian fibroblasts default to fibrotic scarring instead of this Wnt/FGF/BMP programme is a central question in regenerative medicine.

Blastema (dedifferentiated) Stylopod Zeugopod Autopod / digits

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.