THE INFLUENCE OF VASCULARIZATION OF TRANSPLANTED PROCESSED ALLOGRAFT NERVE ON RETURN OF MOTOR FUNCTION IN RATS GUILHERME GIUSTI, M.D., 1 JOO-YUP LEE, M.D., 1 THOMAS KREMER, M.D., 1 PATRICIA FRIEDRICH, B.S., 1 ALLEN T. BISHOP, M.D., 1,2 and ALEXANDER Y. SHIN, M.D. 1,2 * Processed nerve allografts have become an alternative to repair segmental nerve defects, with results comparable with autografts regard- ing sensory recovery; however, they have failed to reproduce comparable motor recovery. The purpose of this study was to determine how revascularizaton of processed nerve allograft would affect motor recovery. Eighty-eight rats were divided in four groups of 22 animals each. A unilateral 10-mm sciatic nerve defect was repaired with allograft (group I), allograft wrapped with silicone conduit (group II), allo- graft augmented with vascular endothelial growth factor (group III), or autograft (group IV). Eight animals from each group were sacrificed at 3 days, and the remaining animals at 16 weeks. Revascularization was evaluated by measuring the graft capillary density at 3 days and 16 weeks. Measurements of ankle contracture, compound muscle action potential, tibialis anterior muscle weight and force, and nerve histomorphometry were performed at 16 weeks. All results were normalized to the contralateral side. The results of capillary density at 3 days were 0.99% 6 1.3% for group I, 0.33% 6 0.6% for group II, 0.05% 6 0.1% for group III, and 75.6% 6 45.7% for group IV. At 16 weeks, the results were 69.9% 6 22.4% for group I, 37.0% 6 16.6% for group II, 84.6% 6 46.6% for group III, and 108.3% 6 46.8% for group IV. The results of muscle force were 47.5% 6 14.4% for group I, 21.7% 6 13.5% for group II, 47.1% 6 7.9% for group III, and 54.4% 6 10.6% for group IV. The use of vascular endothelial growth factor in the fashion used in this study improved neither the nerve allograft short-term revascularization nor the functional motor recovery after 16 weeks. Blocking allograft vascularization from surrounding tissues was detrimental for motor recovery. The processed nerve allografts used in this study showed similar functional motor recovery compared with that of the autograft. V C 2014 Wiley Periodicals, Inc. Microsurgery 36:134–143, 2016. The functional recovery after reconstruction of segmen- tal nerve loss in cases of acute or chronic nerve injuries often remains poor despite advances in surgical techni- ques. Currently available reconstructive options include: vascularized and nonvascularized nerve autografts, nerve conduits from a variety of materials, nerve allografts, and nerve transfers. 1–6 Autografts have been considered the gold standard treatment for most cases, 7 but they have limited availability, dimensions, and produce a donor-site morbidity. An alternative nerve conduit with equal or better outcomes would be a major benefit to the patient. Although processed nerve allografts have been used as an option for reconstruction of sensory deficits, 8 with good results in experimental 9 and clinical reconstruc- tions, 10,11 they failed to demonstrate similar results for motor recovery. 12 Enhancement in nerve allograft revascularization has been demonstrated in experimental studies after a short- term local administration of vascular endothelial growth factor (VEGF). 13 However, little is known about the direct effects of VEGF or the enhancement of revascular- ization of nerve allografts in motor nerve recovery. 14,15 VEGF is a signal protein that stimulates vasculogenesis (de novo formation of vessels) and angiogenesis (growth of vessels from pre-existing vasculature), 16 and it has been proved to increase vascularization in a variety of tissues, including bone 17–19 and nerve. 13 VEGF also has important roles in nerve function not only enhancing local blood flow but also with direct stimulation of axon regeneration. 20–22 The purpose of this study was to deter- mine the effects of enhancement and reduction of revas- cularization of transplanted nerve allografts in the functional motor recovery, using an experimental model. Enhancement was achieved by providing a local short- term delivery of VEGF, and reduction was obtained wrapping the transplanted allografts with a silicone con- duit. Results were compared regarding functional motor recovery, blood vessel formation, and histomorphometry. MATERIAL AND METHODS After approval by the Institutional Animal Care and Use Committee, a unilateral 10 mm sciatic nerve injury gap was created on 88 male inbred Lewis rats, weighing between 200 and 300 g. Animals were divided in four different groups, with 22 animals in each group: group I received a 10 mm processed nerve allograft, group II a 10 mm processed nerve allograft wrapped with a silicone tube measuring 1.4 mm length and 2.0 mm inner diame- ter, group III a 10 mm nerve allograft augmented with VEGF, and group IV a 10 mm ipsilateral reversed nerve Additional Supporting Information may be found in the online version of this article. 1 Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 2 Microvascular Research Laboratory, Mayo Clinic, Rochester, MN Grant sponsor: Musculoskeletal Transplant Foundation. *Correspondence to: Alexander Y. Shin, M.D., Professor and Consultant of Orthopedic Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail: shin.alexander@mayo.edu Received 29 April 2014; Revision accepted 28 November 2014; Accepted 11 December 2014 Published online 30 December 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/micr.22371 Ó 2014 Wiley Periodicals, Inc.