Background: Peripheral nerve injury can occur through a variety of mechanisms including blunt and penetrating injury to the limbs. When severe injury occurs patients require surgical exploration, neurolysis, and often resection of a large segment of scarred / nonfunctional nerve. Ongoing research on alternatives and supplements to nerve grafting have shown promise, including the use of Schwann cells (SCs). In the last 5-10 years improvements have been made to axonal guidance channels (AGCs) ? second generation guidance channels offer a three- dimensional, internal lattice as structural support for budding axons. Such second-generation AGCs offer the perfect platform for SC delivery to the site of nerve repair. Objective/Hypothesis: We propose that transplantation of SCs into these AGCs will improve axonal organization, axonal growth, and improve functional recovery. There is robust data on the benefit of supplementing peripheral nerve grafts with SCs in animals and preliminary data in humans, as demonstrated by our group. Progress in nerve guidance conduits has led to the development of guidance channels with a robust 3D collagen- glycosaminoglycan matrix. Study Design: The study will include ex vitro as well as in vivo components. The majority of Aim 1 will be ex vitro experimentation assessing optimal concentrations of rat and human SCs to promote uniform cellular distribution and survival. Different loading methods will be analyzed.
Aim 1 will include an in vivo arm both rat and human-derived SCs will be loaded into AGCs and these will then be explanted at two weeks post-repair (10 animals).
Aims 2 and 3 will contain all in vivo experimentation.
Aim 2 will investigate six groups: reversed autograft, multiple sural cable grafts, empty hollow AGCs (first-generation), empty 3D AGCs (second-generation), implanted 3D AGCs ? nerve-derived rat SCs. These animals will survive for 4 and 16 weeks, at which point we will measure electrophysiological function (electromyography and nerve conduction studies), axonal counts and density via histological analysis, novel three-dimensional clearing analysis to determine specific axon growth patterns. Behavioral studies will be conducting throughout the study period.
Aim 3 will introduce human derived SCs via an additional group following a similar experimental design (3D AGCs with nerve-derived SCs).
Aims 2 and 3 combined will include 174 animals, for Aim 3 nude athymic rats will be required.
The proposed study will investigate the use of nerve-derived rodent and human Schwann cells and their ability to supplement a nerve graft. These cells will be delivered using a second- generation axonal guidance channel (Neuragen 3D, Integra), which has a structural matrix to support budding axons. Beyond conventional methods to assess outcome (electrophysiology, behavioral analysis, cross-sectional histology) we will utilize a specialized three-dimensional confocal microscopy to compare axonal microstructure between experimental groups.
