Continuous imaging shows cells during limb regeneration

Regeneration of limbs may be restricted to lizards and crustaceans, but science is no less interested in studying just how cells accomplish the amazing feat. For the first time, researchers have been able to record just how epidermal cells act during regrowth after amputation.

A team from the Institute of Functional Genomics in Lyon (IGFL), France, used a continuous stream of live imaging to monitor the regeneration of the leg of the crustacean Parhyale hawaiensis.

"Parhyale hawaiensis is well suited for imaging limb regrowth," said Michalis Averof, Director of Research at IGFL and senior author of the current study. "The animals have relatively rapid limb regeneration, requiring as little as one week for young adults to fully regrow their legs. Also, their tiny limbs enable us to image the regeneration process in unprecedented cell-by-cell detail through their entire thickness."

To track the regeneration process, researchers labeled the epidermal cells with fluorescent proteins. A live recording of the regrowth process was first taken via microscopy four to five days after amputation. The recording showed researchers the cellular events of the wound closure and morphogenesis of regenerating legs in high resolution.

Over the course of the study, researchers found no specialized stem cells for regeneration of the epidermis in new limbs. Instead, most of the amputated leg's epidermal cells divided and rearranged themselves into new segments.

"With the ability to track the movements and behavior of single cells individually through time, we now have the means to understand the cellular dynamics of the regeneration process, which could not have been reconstructed from fixed material,” said first author Frederike Alwes. "While our paper focuses mostly on the behavior of epidermal cells, we now plan to extend this work to include all the different cell types that are involved in limb regrowth. The ultimate aim of our research is to explore how some animals can respond to a severe injury by regenerating an entire body part that was lost."