Co-Graft of Bone Marrow Stromal Cells and Schwann Cells Into Acellular Nerve Scaffold for Sciatic Nerve Regeneration in Rats

Purpose: The conventional strategy for bridging large nerve defects, namely nerve autograft transplantation, results in donor-site morbidity. This detrimental consequence currently drives the search for alternatives. The authors used an acellular nerve scaffold filled with bone marrow stromal cells (BMSCs) and Schwann cells (SCs) to enhance regeneration.

Materials and methods: In 60 adult rats, a 10-mm sciatic nerve defect was bridged with a nerve autograft (positive control), an acellular nerve scaffold (negative control), an acellular nerve scaffold with BMSCs (group I), an acellular nerve scaffold with SCs (group II), or an acellular nerve scaffold with BMSCs plus SCs (group III). After regenerating for 4 and 16 weeks after surgery, nerve regeneration was functionally assessed by a walking track analysis. The compound muscle action potential (CMAP), nerve conduction velocity (NCV) along regenerated sciatic nerves, and gastrocnemius muscle index (GMI) were recorded to assess the conduction properties and extent of denervation atrophy. The number of retrograde-labeled lumbar motor neurons identified by fluorescent dyes in the ipsilateral ventral horn and spinal ganglia were counted to assess the regeneration of axons.

Results: After 4 and 16 weeks, improvement of the sciatic function index of the sciatic nerve in group III was statistically greater than that of the negative control group, group I, and group II. At 16 weeks after grafting, obvious differences in the GMI were found among groups. Group III had a statistical increase in GMI compared with the negative control group, group I, and group II. The CMAP and NCV measurements showed comparable results at 16 weeks after reconstruction: group III had statistically better results compared with the negative control group, group I, and group II. Fluorescent dye analysis of the retrograde-labeled lumbar motoneurons in the ipsilateral ventral horn and spinal ganglia showed that more motor neurons in the ipsilateral ventral horns and spinal ganglia were labeled in group III than in the negative control group, group I, and group II at 16 weeks after the operation. All results consistently showed that when BMSCs and SCs were loaded together in an acellular nerve scaffold, functional recovery of the sciatic nerve was enhanced to the greatest degree among the 3 cell-treated groups; furthermore, its beneficial effect on sciatic injury regeneration was similar to the autograft group, although it never exceeded it.

Conclusions: This study is a step forward in the search for an alternative to the nerve autograft because it showed that co-grafting of BMSCs and SCs into an acellular nerve scaffold enhanced sciatic nerve functional recovery in rats. Its beneficial effect on sciatic injury regeneration was similar to the autograft group, although it did not exceed it.