| For patients with long-distance nerve defects, neuro-restorative effect of the bridged nerve guidance conduit(NGC) remains a big challenge, although it has emerged as a promising new therapeutic tool. The current research focus on the development of various types of nerve conduits with better biological activity to continuously improve the degree of nerve repair after damage. A non-antigenic and biodegradable chitosan nerve guidance conduit has been successfully developed and tested in the animal models with peripheral nerve injury previously by our research group. In this study, according to the needs of the clinical translation, the large mammals(goats) were used as the animal model of peroneal nerve injury with long-distance gap to investigate the feasibility of application of two enhanced biologically active chitosan nerve conduits, i.e., one seeded with autologous bone marrow mononuclear cells, the other filled with two neurotrophic factors(nerve growth factor, NGF and basic fibroblast growth factor, b FGF) fibrin gel. The new scanning sequence 3D m FFE WATs with three-dimensional reconstruction techniques were used first in 3.0 Tesla magnetic resonance scanner to observe the damage and regeneration conditions of peroneal nerves in goats and to elucidate the clinical potential application value in the field of peripheral nerve system.The animal’s behavior assessment, high-field magnetic resonance neuroimaging(MRN), electrophysiological examination, morphological and immunohistochemical analysis were carried out to monitor and evaluate the nerve regeneration and functional recovery. One-year follow up results showed that(1) chitosan conduit with autologous bone marrow mononuclear cells, an artificial tissue engineering nerve, can repair the 30-mm defect in goats. This effect is similar with autologous nerve graft: the locomotor ability of animals was improved close to normal state. No significant differences were found in conduction velocities of regenerated nerves compared with autologous nerve transplantation group. The axonal regeneration crossed bridging grafts to the full length, although the diameter of the newborn nerve fiber is still smaller than the normal ones. The myelin density is also thin. The control group(conduit filled with saline) failed to repair nerve and there are significant differences compared to the group of bone marrow mononuclear cells plus conduit and autologous nerve graft group(p < 0.05).(2) Combination of chitosan conduit with NGF / b FGF / heparin / fibronectin / fibrin gel successfully repaired 26-mm nerve defects. The animal’s motor behavior ameliorated significantly. Electrophysiological nerve conduction tests also showed improvements and the robust nerve regeneration crosses the gap as observed by MRI scanning and histological investigations. The goat in control group(saline plus conduit) did not have functional recovery and nerve repair as compared to the experimental groups(p < 0.05).(3) High-field MRN could clearly show the peripheral nerve injury and repair, and has the capability of dynamic and continuous observation for the morphological changes of local conditions after chitosan conduit were bridged in vivo. The preliminary results of this study demonstrated that the enhanced biological activity of chitosan conduits with bone marrow mononuclear cells or NGF / b FGF gel may promote long-distance nerve regeneration and functional recovery. Further studies to quantify the functional evaluation of critical nerve defects of different large animal models closed to human, and comparing various bioactive conduits is the next focus of our research. |
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