Computational and Experimental Study of the Mechanics of Embryonic Wound Healing

TL;DR

This study uncovers a rapid, biphasic wound healing process in embryonic chick epithelia involving actomyosin contraction, with a faster initial phase and a slower subsequent phase, supported by experimental and finite-element modeling evidence.

Contribution

It reveals a previously uncharacterized rapid wound closure mechanism in embryos, combining experimental observations with biophysical modeling to elucidate actomyosin dynamics.

Findings

Wounds can close over 50% within 30 seconds.

Healing involves a biphasic process with rapid and slow contraction phases.

Finite-element models support the biophysical plausibility of the proposed mechanism.

Abstract

Wounds in the embryo show a remarkable ability to heal quickly without leaving a scar. Previous studies have found that an actomyosin ring ("purse string") forms around the wound perimeter and contracts to close the wound over the course of several dozens of minutes. Here, we report experiments that reveal an even faster mechanism which remarkably closes wounds by more than 50% within the first 30 seconds. Circular and elliptical wounds (~100 um in size) were made in the blastoderm of early chick embryos and allowed to heal, with wound area and shape characterized as functions of time. The closure rate displayed a biphasic behavior, with rapid constriction lasting about a minute, followed by a period of more gradual closure to complete healing. Fluorescent staining suggests that both healing phases are driven by actomyosin contraction, with relatively rapid contraction of fibers at cell borders within a relatively thick ring of tissue (several cells wide) around the wound followed by slower contraction of a thin supracellular actomyosin ring along the margin, consistent with a purse string mechanism. Finite-element modeling showed that this idea is biophysically plausible, with relatively isotropic contraction within the thick ring giving way to tangential contraction in the thin ring. In addition, consistent with experimental results, simulated elliptical wounds heal with little change in aspect ratio, and decreased membrane tension can cause these wounds to open briefly before going on to heal. These results provide new insight into the healing mechanism in embryonic epithelia.