Potential of Artificial Nerve Filled with Schwann Cells for the Treatment of Nerve Defect over 20 mm in Rats.
Masao Suzuki, Graduated student1; Ayato Hayashi, professor1; Satoshi Ichihara, Associate professor1; Ohtani Satoshi, Graduated Student1; Sayaka Ishii, Graduated student2; Akira Hara, Associate Professor1
1Juntendo University Urayasu Hospital, Chiba, Japan; 2Juntendo University urayasu Hospital, Chiba, Japan
Background and Aims: Migrating Schwann cells (SCs) through end-to-side (ETS) neurorrhaphy has been used as an option for inducing faster axonal growth within a graft. In this study, we investigated in vivo, whether ETS neurorrhaphy could be useful for inducing migration of SCs into an artificial nerve (AN) and whether such ANs were superior to conventional ANs in repairing 20mm nerve gaps in rats.
Methods: 8-12-week Sprague Dawley rats (n=48) were divided into 2 experimental groups, control (AN Group) and experimental (SCiAN Group). Prior to the experiment, the ANs employed for SCiAN Group had SC migration induced over 4 weeks in vivo through end-to-side (ETS) neurorrhaphy on to rat sciatic nerve. Both groups underwent end-to-end suture of 20mm AN onto 20mm gap in sciatic nerve. Two sections from AN (AN Proximal (AN-P) and AN Distal (AN-D)) and another section from distal sciatic nerve (SN-D) in both groups underwent assessments at 4 weeks for SC migration through immunohistochemical analysis and for s100, nerve growth factor, brain derived nerve growth factor through polymerase chain reaction. At 16 weeks, the extent of SC migration and axonal elongation were assessed through immunohistochemical analysis, histomorphometry and electron microscopes, counting total myelinated fibers, calculating g-ratio, measuring myelin sheath thickness and axon diameter. Functional recovery was also evaluated at 16 weeks, conducting Von Frey Filament test for sensory recovery and calculating their muscle fiber areas for motor recovery.
Results: At 4 weeks, the area occupied by SCs at AN-P and AN-D were significantly larger in the SCiAN Group than in the AN Group. Similarly, at 16 weeks, the area occupied by axons at AN-P, AN-D, and SN-D were significantly larger in the SCiAN Group than the AN Group, Histo-morphometrical evaluation at AN-D also revealing significantly higher number of axons. In the 16-week functional recovery assessments, plantar perception in the SCiAN Group showed significantly better improvement of sensory function. However, no tibialis anterior muscle improvement was observed in neither group.
Discussion: In vivo induction of SC migration to an AN through ETS proved to be a useful technique for repairing 20mm nerve defect in rats, revealing better nerve regeneration and sensory recovery. No motor recovery could be observed in neither group, however, it may be that such recovery requires a longer period of time and it is pre-mature to arrive at its conclusion after 16 weeks. Longer assessment period would be interesting for further study.
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