Abstract
Purpose::
Wounds produced on monolayers of cultured bovine corneal endothelial cells (BCEC) heal by a combination of actin cable formation and lamellipodia-dependent cell crawling. Each one of these two basic mechanisms can be selected by maintaining or removing the extracellular matrix (ECM) on the wound surface. The purpose of this work is to introduce a mathematical model that describes the dynamics of development of these basic cellular mechanisms of epithelial wound healing.
Methods::
Confluent monolayers of BCEC were wounded with a syringe needle or a silicon-coated wire to remove or maintain the underlying ECM, respectively. In wounds produced removing the ECM, a narrow strip of matrix nevertheless remains at each of the two borders. The lengths of wound border presenting actin cable, lamellipodial protrusions or none of these structures were measured on images taken after staining with rhodamin-phalloidin. To determine the rate of wound closure the wounded monolayers were periodically examined under phase optics. The dynamic model consists in differential equations that describe the rate of formation of actin cable and lamellipodial protrusions at the wound border. The time evolution of the model was determined by numerical integration. The parameters were adjusted to obtain good approximations to the experimental results.
Results::
In wounds created both removing and maintaining the ECM, approximately two hours following injury about 40% of the wound border corresponds to actin cable and 40% to lamellipodial protrusions. Afterwards, the percentages vary for the two experimental conditions. In wounds preserving the ECM the percentage of actin cable gradually decreases to zero whereas for the case of ECM removal that percentage increases. The mean values for the rates of wound closure are 0.1 and 0.2 mm/min, for monolayers that heal predominantly by actin cable formation and by lamellipodial crawling, respectively. These observations can be reproduced by the model simulations assuming that the healing process starts with similar parameter values for the two experimental conditions and that the absence of the ECM afterwards induces modifications in the parameter values (i.e., made effective once the healing border reaches the denuded wound region.
Conclusions::
The experimental results and model simulations are consistent with the idea that the extracellular matrix plays a critical role in the determination of the specific cellular mechanisms adopted to perform wound healing in epithelia.
Keywords: cornea: endothelium • wound healing • extracellular matrix