Characterization of the radial excision repair model: an in vivo assay for dedifferentiation

The Urodele amphibians are the only adult vertebrates able to fully regenerate lost limbs. This impressive regenerative response begins with the formation of a mass of multipotent cells, called a blastema, after injury, which then directs the development of a new fully functional limb. The mechanisms through which the blastema achieves this are not fully understood, however if we are able to fully characterize the events which take place, then we can hopefully use that knowledge to enhance human regenerative ability. One of the ways in which this can be accomplished is by manipulating non-blastema cells in an effort to make them "blastema like," however this in turn requires an assay which will allow you determine whether or not your cells in question are actually regenerative competent. To this end our lab recently devised a model for determining regenerative competency termed the radial excision repair model. This model is based on the observation that, despite their tremendous limb regenerating abilities, the axolotl cannot regenerate a 2mm surgically created bone defect in the radius of the forelimb. We discovered that regeneration could be induced by grafting cells from a blastema into the defect area. This gives us an effective assay with a well defined readout (regenerative response), with which we can assay how closely experimentally manipulated cells can match a blastema regeneration response. To enhance the viability of the assay, we characterize the levels of cell proliferation and apoptosis which occur as a result of a blastema graft at 2, 10, and 20 days. With these characterizations, we will be able to make full use of the radial excision repair model by allowing researchers to compare experimental cells to blastema cells with a variety of readouts.