Regeneration of rabbit ear tissue.

Holes punched in the ears of rabbits are repaired by regeneration of new tissues from blastemas found on the periphery of the wounds. The proportion whch successfully regenerated was greater in males than in females (75% vs 20%), in pregnancy than during etrus or lactation (75% vs 25%), and in ovariectomized does given testosterone than in those given oil carrier alone (88% vs 50%), but the speed of closure did not differ in these groups. The steroid hormone influence postulated by other workers is confirmed. Closure was faster in younger animals and for second holes punched on the same site where earlier holes had been repaired, in both cases, by shortening of the initial seven to ten day delay period seen for primary holes in adult ears. The cartilage layer was also thicker after regeneration from secondary punches and the success rate greater (67% vs 29%). These observations suggest a "priming" effect on the tissue from the primary punch. Ear holes in the area proximal to the head were repaired faster and with more success (78% vs 12%) than those punched distally. The relative thickness of the cartilage layer may be the critical factor. Tissues did not regenerate from semicircular layer may be the critical factor. Tissues did not regenerate from semicircular wounds made on the edge of the pinna. Hair grown on regenerated ear skin reestablished the original color pattern. Skin regenerating for hles punched where skin from the back had been transplanted to ears had the characteristics of back skin, but no regeneration was detectable from transplanted toe tissue. Skin from other locations can regenerate in the environment provided by the ear but more complex tissue structures put into the same locatin apparently cannot. Skin cells involved in regeneration originate from the tissues bounding the wound.