Theory 06/Regenerative Biology/Appendage regeneration
Regeneration Needs Nerves, Not Factors
Nerves are known to be required. The requirement may be quantitative, which changes what replacement therapy should deliver.
Appendage regeneration requires a threshold in nerve density at the stump rather than a specific trophic factor, so denervation abolishes regeneration even when the factors are supplied exogenously.
01The evidence
Denervation blocks limb regeneration in amphibians, and exogenous growth factors do not fully rescue it.
02The tension
The nerve requirement is attributed to specific factors released by axons. That predicts factor replacement should rescue, which it does not.
03The mechanism
Blastema formation requires a threshold density of nerve endings, because the signal is a sum over many contacts rather than a concentration from a few. Below the threshold, the aggregate signal is insufficient regardless of how much any single source provides.
That makes density the determinant, and predicts that adding nerves should rescue while adding factors should not.
04What this is not
Those make one factor the requirement. This makes the summed density the requirement, which explains the failure of factor rescue.
05Predictions
- P1Regeneration should track nerve density.
- P2Factor supplementation should fail below threshold.
- P3Nerve grafting should rescue regeneration.
06Refutation
Factor replacement rescuing denervated limbs would restore the factor account.
07What it changes
It would redirect regenerative therapy toward innervation.