The effect of mechanical obstruction on tissue regeneration in the rabbit's ear

Abstract

Abstract Tissue of area 1 cm.2 was excised through the full thickness of both ears of a group of rabbits. The excision site of one ear of each rabbit was blocked with Perspex for a time varying between 7 and 49 days. The other ear was allowed to heal and regenerate normally as a control. The growth of new tissue in the experimental ears was measured after block removal and compared with that of the opposite control ears. The regenerated tissue was also examined histologically for changes produced by blocking. Blocking for any period up to 49 days results in an increased growth rate on block removal. Only blocking for 14 days or less has a permanent stimulatory effect. All other blocking periods investigated (21, 28, 35, 42, and 49 days) were ultimately deleterious. The presence of the mechanical blocking device stops the development of a blastema in the normal position. The blastema cells gather in the uninjured tissue behind the wound edge and take up their normal position once the block is removed. The harmful effect of long-term blocking may be due to reduction of the vascularity of the marginal tissue and subsequently to damage to the blastema. Blocking for 14 days or longer results in deformation of the regenerating elastic cartilage.