Macromolecular Nerve Conduit And Sciatic Nerve Regeneration: An Experimental Study In Rats

Macromolecular Nerve Conduit and Sciatic Nerve Regeneration: An Experimental Study in RatsPeripheral nerve injury is one of the common traumas which results in severe sensory-motor deficits in patients. Using nerve conduit is a new therapy for peripheral nerve damage with significant limitations. The main problems are: 1) It is not well studied how to select appropriate materials, ameliorate the manufacture of the nerve conduit, and improve the nerve conduits which can adapt themselves to the microenvironment surrounding the gaps better. 2) It is necessary to develop certain fillings with the nerve conduits to accelerate nerve regeneration and improve its quality. In the current study we investigated the effects of macromolecular nerve conduit on peripheral nerve regeneration in rats. The innovative macromolecular nerve conduit filled with Schwann cells were made by Zheijang University Macromolecule Institution. The aim of this study is to find a reliable method to repair peripheral nerve gaps.Part One: The effects of physical and chemical features of the macromolecular nerve conduits on the peripheral nerve regenerationObjective: To investigate the effects of the physical and chemical features of themacromolecular nerve conduits on the repair of the peripheral nerve gaps in rats and evaluate the effectiveness of the polyester-polycarbonate nerve conduits on nerve regeneration in a relatively longer gap (10mm -13mm) in sciatic nerve. Methods: Four types of polyester-polycarbonate nerve conduits (A, B, C and D) with different permeability and degradation rates to bridge two stumps of the rat sciatic nerve gap were employed. The information of nerve regeneration by means of periodical observation was recorded. (Tube A, B and D were semi-permeable, with pore size of less than 15 μm and Tube C was not permeable. The lengths of the tubes were 14-18 mm and the wall thickness was about 200 μm. ) Results: 1) An improvement was observed on the flextion of the experimental limb and the walking manners four weeks after nerve conduit implantation. There was no ulceration presented on the limbs. The degradation of the nerve conduit was first observed at four weeks and was completed at 20 weeks. The bridging part had thickened without evidence of atrophy of the distal and proximal nerve stumps. 2) The contraction rate of anterior tibial muscles after electric stimulation was measured in all five groups. The group using tube-A (Group tube-A) ranked top in the positive rates, and followed by Group tube-D, Group tube-B, and Group tube-C. Group E (without using tubes) was the worst. There were significant differences in the positive rates between the groups of the 4-week and the 12-week, as well as the groups of the 4-week and the 20-week. In contrast, the positive rates were similar in the 12-week and the 20-week groups. 3) Histological observations: Four weeks after implantation, there were no nerve fibers and degradation of the conduit presented in tube-C. A few nerve fibers connecting the two ends of the injured nerves in tube A, B and D were presented. However, there were no significant differences among them. In the 12-week and the 20-week groups, the numbers of the nerve fibers ranked as below: Group tube-A = Group tube-D > Group tube-B > Group E > Group tube-C. The rank of fibrous tissues,inflammatory cells and vascularization was Group tube-B > Group tube-D > Group tube-A >Group tube-C. In the 20-week group, there were still a few nerve fibers in tube D. The thickness of myelin sheaths and g value (the thickness of myelin sheath/the radius of the axon) were much less than those of normal rat sciatic nerves. Meantime lots of macrophages, fibroblasts and collagen fibers were found in tube D. Conclusions: 1) The successful regeneration can be accomplished over the 10-13mm peripheral nerve gap under the guidance of polyester-polycarbonate nerve conduits. 2) The permeability and degradation rate of the macromolecular nerve conduits had critical influences on the nerve regeneration. Our study demonstrated that tube A and D can im...