| Objective:This study was designed to explore the characteristics of the PGA nerve conduit in vitro degradation,biocompatibility,in vivo degradation,and the nerve repair effect in nerve defects,so as to provide the basis and a method for repairing peripheral nerve injuries.Method:The PGA nerve conduits were soaked in 15ml of normal saline for in vitro degradation.The experimental period was 12 weeks,with one observation time point per week.At each time point,four nerve conduits were immersed in 15ml normal saline,while in three of them the normal saline was replaced every 72h to calculate the mass loss rate,and one of them the normal saline was not replaced to measure the pH value of the immersion solution.The biocompatibility of the PGA nerve conduit was observed.The DMEM medium containing 10%fetal bovine serum was used as the extraction medium.The extraction medium was added at a ratio of 6cm~2/ml as the sample group,and the extraction medium was used as the blank control group.The extraction medium was used at(37±1)℃for(72±2)h.RSC96 rat neural Schwann cells were chosen to characterize the biocompatibility of neural conduits.The effect of PGA nerve conduit on RSC96 cell proliferation was observed by MTT experiment,and the effect of PGA nerve conduit on RSC96 cell migration was observed by Transwell experiment.The PGA nerve conduit was embedded in the muscle space of the lower limbs of rats for in vivo degradation.The degradation and biocompatibility of the PGA nerve conduit were evaluated through general observation,blood routine,liver and kidney function tests,and histological examination.Sciatic nerve defect model in rats was used to explore the differences in nerve regeneration and functional recovery between PGA nerve conduit and autologous nerve transplantation.The differences in nerve regeneration and functional recovery between the two groups were evaluated by general observation,gait measurement analysis,toe extension test,gastrocnemius wet weight recovery rate,and histological examination.Results:The degradation rate of in vitro degradation was 1.47±0.026%at 4 weeks.At this time,the shape of the nerve conduit was complete,and the support was not significantly changed.Then the degradation rate gradually accelerated.At the time of 12 weeks,the degradation rate was 32.18±0.040%.At this time,although the shape of the nerve conduit was complete,the overall conduit became soft,and the support strength became worse than before.The pH decreased slowly in the first 2 weeks while the pH value was 6.20±0.061at the 2nd week.The pH value suddenly dropped to 3.93±0.118 at the 3rd week,and then the pH decreased slowly,and the pH value was 2.56±0.003 at the 12th week.The results of MTT experiment showed that the extract of PGA nerve conduit had no effect on the proliferation of RSC96 cells,and there was no significant difference compared with the control.The results of Transwell experiment showed that the PGA nerve conduit had no effect on the migration ability of RSC96 cells,and there was no significant difference compared with the control(P>0.05).The results of in vivo degradation experiments of PGA nerve conduits showed that the nerve conduits in both groups showed good support at 2 weeks after operation.At 4-12 weeks after surgery,the nerve conduits in the experimental group gradually softened and collapsed,but the conduits were intact without breaks.The surface of the conduits wrapped soft tissue gradually and it was difficult to peel off.The control group still showed good support 4 weeks after operation,without obvious collapse.At 8 and 12 weeks after operation,the conduits in the control group gradually became soft and collapsed.The blood routine examination,liver and kidney function tests had no statistically significant difference between the experimental group and the control group at the same period,and between each time point within the groups and the preoperative groups(P>0.05).There were no obvious abnormalities in liver and kidney anatomy at each observation time point.The results of histological examination showed that there were less inflammatory cell infiltration around the conduit in the experimental group and the control group at 2 weeks after operation.At 4,8,and 12 weeks after operation,there was no obvious degeneration and necrosis of the muscle tissue around the conduits in the two groups,and no obvious inflammatory cells infiltration.The muscle tissue morphology is normal.The results of the experiment on rat sciatic nerve repaired by PGA nerve conduit showed that the right calf muscles of the nerve conduit group and autologous nerve transplantation group were significantly atrophied at 4 weeks after operation,and recovered to varying degrees at 12 weeks after the operation.In the nerve conduit group,the nerve conduit was intact at 4 weeks after operation,without falling off,collapsed and deformed.The regenerated nerve gradually became thicker at 8,12,and 16weeks after operation,and the nerve conduit gradually degraded without obvious infection around it.No neuroma formation was seen.The results of gait analysis showed that the SFI of both groups decreased significantly at 4 weeks after operation(t=0.662,P=0.5762>0.05),and the difference was not statistically significant.With the prolongation of recovery time,SFI gradually increased at 8-12 weeks after operation,and the autologous nerve transplantation group recovered faster.There was a statistically significant difference between the conduit groups and the autologous nerve groups(P<0.05).The nerves in both groups recovered,but the nerve recovery in the autologous nerve transplantation group was better than that in the nerve conduit group.The right toe extension test results of the nerve conduit group were still grade 1 at 16 weeks after operation,while the right foot toe extension test results of the autologous nerve transplantation group were grade 2.This result showed that the nerve recovery of the autologous nerve transplantation group was better than that of the nerve conduit group.The gastrocnemius muscle recovery rate showed that there was a statistically significant difference in the gastrocnemius muscle recovery rate between the nerve conduit group(37.53±3.649%)and the autologous nerve transplantation group(56.86±3.862%)(t=6.579,P=0.0223<0.05).Histological examination showed that the nerve recovery group in the autologous nerve transplantation group was better than that in the nerve conduit group.Conclusions:1.The pH value of PGA nerve conduit degradation in vitro was relatively stable within 2 weeks,and then dropped rapidly after 3 weeks,and the degradation speed was accelerated.2.The PGA nerve conduit body has no obvious effect on the proliferation and migration of RSC96 cells,indicating that it exhibits good biocompatibility.3.The degradation rate of the PGA nerve conduit in vivo is faster than that of the control samples,but it has no significant impact on the blood,liver and kidney functions of rats.The degradation products do not cause obvious local inflammation and rejection,and no obvious muscle necrosis occurs.These results showed that the PGA nerve conduit and its metabolites have no obvious effect on local tissues,blood system and liver and kidney organs,and have good biocompatibility.4.PGA nerve conduit is not as good as the autologous nerve transplantation in repairing rat sciatic nerve defect. |
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