Brief electrical pulses improved survival and regeneration in the colonial chordate Botryllus

What happened

Botryllus schlosseri is a colonial marine chordate that replaces all of its differentiated tissues every week from progenitor cells, so its ageing tracks the decline of that precursor pool. The researchers applied a pulsed electrical current to colonies: 20 mA at 150 pulses per minute for five minutes, repeated three times, a regimen based on parameters used in cardiac pacing.

Stimulated colonies grew more, reproduced more and survived longer. Twelve months after treatment, 9 of 12 stimulated colonies were alive and still budding weekly, compared with 2 of 12 controls (P = 0.0123). Whole-transcriptome analysis showed a two-phase response. Within two hours, genes for the mitochondrial respiratory chain, the contractile apparatus and the extracellular matrix were turned down together. By 24 hours the same pathways were strongly reactivated. The treatment also shifted gene expression from a pro-inflammatory to a reparative signature, which the authors compare to changes seen in mammals after exercise.

Why it matters

Endogenous electrical currents are known to regulate development and regeneration, but their effect on lifespan and stem-cell-driven repair is poorly understood. An animal that rebuilds its body weekly offers a direct way to test whether an electrical intervention acts on progenitor cells.

Caveats

The survival comparison involves 12 colonies per group from one laboratory. Botryllus is an invertebrate chordate with an unusual, continuously regenerating body plan, so the result says little about ageing in vertebrates. The study shows that an applied current changes outcomes; it does not show which endogenous bioelectric signals are involved. The paper declares that the company that makes the pacemaker used for stimulation contributed the pacemakers and electrodes.