Effects of collagen membranes enriched with in vitro-differentiated N1E-115 cells on rat sciatic nerve regeneration after end-to-end repair

Abstract

Peripheral nerves possess the capacity of self-regeneration after traumatic injury but the extent of regeneration is often poor and may benefit from exogenous factors that enhance growth. The use of cellular systems is a rational approach for delivering neurotrophic factors at the nerve lesion site, and in the present study we investigated the effects of enwrapping the site of end-to-end rat sciatic nerve repair with an equine type III collagen membrane enriched or not with N1E-115 pre-differentiated neural cells. After neurotmesis, the sciatic nerve was repaired by end-to-end suture (End-to-End group), end-to-end suture enwrapped with an equine collagen type III membrane (End-to-EndMemb group); and end-to-end suture enwrapped with an equine collagen type III membrane previously covered with neural cells pre-differentiated in vitro from N1E-115 cells (End-to-EndMembCell group). Along the postoperative, motor and sensory functional recovery was evaluated using extensor postural thrust (EPT), withdrawal reflex latency (WRL) and ankle kinematics. After 20 weeks animals were sacrificed and the repaired sciatic nerves were processed for histological and stereological analysis. Results showed that enwrapment of the rapair site with a collagen membrane, with or without neural cell enrichment, did not lead to any significant improvement in most of functional and stereological predictors of nerve regeneration that we have assessed, with the exception of EPT which recovered significantly better after neural cell enriched membrane employment. It can thus be concluded that this particular type of nerve tissue engineering approach has very limited effects on nerve regeneration after sciatic end-to-end nerve reconstruction in the rat.

Figure 1

Weekly values of the percentage of motor deficit obtained by the Extensor Postural Thrust (EPT) test. * Significantly different from week-0 all groups pooled together (p < 0.05). # Group End-to-EndMembCell significantly different from the other groups (p < 0.05). Results are presented as mean and standard error of the mean (SEM).

Figure 2

Weekly values of the withdrawal reflex latency test. At week-1 all animals failed in responding to the noxious thermal stimulus within the 12 sec cut-off time. No differences between the percentages of motor deficit obtained by the Extensor Postural Thrust (EPT) test. * Significantly different from week-0 all groups pooled together (p < 0.05). Results are presented as mean and standard error of the mean (SEM).

Figure 3

Kinematics plots in the sagittal plane for the angular position (°) of the ankle as it moves through the stance phase, during the healing period of 20 weeks. The mean of each group is plotted.

Figure 4

Kinematics plots in the sagittal plane for the angular velocity (°/s) of the ankle as it moves through the stance phase, during the healing period of 20 weeks. The mean of each group is plotted.

Figure 5

Representative high resolution photomicrographs of nerve fibers form regenerated (A-C) and normal (D) rat sciatic nerves. A: End-to-End. B:End-to-EndMemb. C:End-to-EndMembCell. Magnification = × 1,500.