Sensorimotor recovery after partial facial (mystacial pad) transplantation in rats

Most research in facial transplantation has been conducted in rats. This skill demanding model has a steep learning curve and is accompanied by high mortality rates. Investigations were carried out to minimize these disadvantages and a whiskers flap properly named mystacial pad flap, was developed. The mystacial pad contains the whiskers follicles of the rat, and our aim was to investigate the effect of repairing the nerves on the whiskers function after mystacial pad allotransplantation in rats. A total of 56 animals were studied in 6 groups. In the main study group (VI), 16 semi-allogenic vascularized mystacial flaps were transplanted from Lewis-Brown-Norway (RT1(l+n)) to Wistar-Lewis (RT1(l)) rats. This group was divided in 2 subgroups; in subgroup VIa (nonneurotized alloflap transplant group, n = 8), alloflaps were transplanted without nerve repairs, whereas in subgroup VIb (neurotized alloflap transplant group, n = 8) the facial and trigeminal nerves were repaired. Animals were kept under tapered doses of tacrolimus immunosuppression monotherapy. Clinical and neurophysiological explorations were performed to evaluate sensitivity and motor voluntary activity of the mystacial region after 6 weeks. Animals were euthanized after 8 weeks and histologic studies were performed. In group VI, each procedure required an average of 3.5 hours, and 87.5% of the recipients survived for 8 weeks. Sensitivity, motor activity, and histologic signs of recovery were found in the mystacial pad allotransplants after 6 weeks. Mystacial pad allotransplants in which nerves were repaired showed clinical, neurophysiological, and histologic signs of recovery. A functional facial subunit was successfully transplanted and sensorimotor function recovery could be demonstrated in rats.