Study On The Preparation Of Chitosan Nerve Conduit Combined With Nerve Growth Factor Microspheres And Its Repairing Of Facial Nerve Defect In Rabbits

OBJECTIVE To prepare the complicated controlled release microspheres of nerve growth factor (NGF), and respair facial nerve defect in rabbits by using chitosan nerve conduit combined with NGF.To evaluate the role of sustained releasing NGF on the growth of facial nerve.METHODS:(1) The NGF microspheres were obtained by multiple emulsificating solvent evaporating(W/O/W) or Polymer-alloys combined with oil-oil emulsion/solvent evaporation (S/O/W)method,and its general properties and releasing of NGF in vitro were studied. The morphology, size of NGF microspheres were observed in scanning electron microscope(SEM),and NGF content was assayed by an enzyme-linked immunosorbent assay(ELISSA), while its bioactivity was measured by PC 12 cell method. (2)Thirty-six New Zealand white rabbits which weighed 2.5-3 kilograms were made the model of 10mm gap on the right buccal branches of the facial nerve under sterile condition and were randomly divided into four groups(nine in each group): Group A:chitosan nerve conduit+NGF microsphere(10 mg), Group B:chitosan nerve conduit+NGF (5μg),Group C: chitosan nerve conduit+normal saline, Group D: autogenous nerve transplantation. Each group was divided into 3 subgroups (three in each group).General observation, measure of fiber diameter, nerve electrophysiology detection, histochemistry,and immunohistochemical and SEM observation were employed 30,60,90 days after surgery.RESULTS:The NGF microspheres yield of multiple emulsificating group (23.74%), the NGF microspheres yield of Polymer-alloys group(49.46%). The release of NGF in multiple emulsificating group continued to more than 60 days,while the release of NGF in Polymer-alloys group continued than 90 days. Beneficial effects on nerve conduction speed, fiber amount and thickness of medullary sheath were observed in Group A than Group B and C,while Group D had the similar effect.CONCLUSION:The NGF microspheres yield in Polymer-alloys group were higher than multiple emulsificating group. The complicated controlled release NGF microspheres has stable property in vitro,which can release active NGF for a long time. The effect of facial nerve regeneration in chitosan nerve conduit combined with NGF microspheres were similar to the autogenous nerve transplantation group,while significantly better than the control group.The chitosan nerve conduit combined with NGF microspheres can significantly improve the repairing of the facial nerve defection.