Functional outcome after facial allograft transplantation in rats

SummaryBackgroundFull face, hemiface and facial subunit transplants have been reported before. However, the functional recovery of the face transplant largely remains unknown. The mystacial pad (also known as the vibrissal or whiskers region) is the main sensorimotor unit in rats' faces. We included the mystacial region in the hemifacial flap of the rat, and our aim was to study its functional recovery after transplant.MethodsHemifacial flaps were transplanted from Brown-Norway RTn to Wistar-Lewis RTl rats, under tapered doses of tacrolimus immunosuppression monotherapy (8 mg/Kg/day to 2 mg/Kg/day after 4 weeks). Group I (n = 12) was the anatomic study group, in which the harvesting technique of the flap was trial run and angiographies of the flap were obtained. In group II (n = 12), non-vascularized hemifacial allografts were transplanted. Group III (n = 24) was the vascularized hemiface allotransplant group. This was divided into two subgroups relating to nerve repairs. In subgroup IIIa (n = 12) no nerve repairs were performed, while in subgroup IIIb (n = 12) the zygomaticoorbital, bucolabial and upper marginal mandibular branches of the facial nerve, and the infraorbital branch of the trigeminal nerve were repaired. Clinical, neurophysiological and histological studies were performed to evaluate the recovery of the mystacial region after six weeks.ResultsIn group I the hemifacial flap harvesting technique to include the mystacial region was established, and angiographies confirmed a rich axial vascular network in the flaps. All grafts in group II necrosed. In group III, each procedure required an average of 7 h (range 5–11). Of this group, 75% of the rats survived for 8 weeks. In subgroup IIIa no signs of recovery were noted, whilst in subgroup IIIb clinical, neurophysiological and histological recovery were found in face transplant recipients after 6 weeks.ConclusionsThe hemifacial flap including the mystacial region could be transplanted successfully in the rat model. Face allotransplants in which nerves were repaired showed clinical, neurophysiological and histological signs of recovery.