Combined use of spinal cord-mimicking partition type scaffold architecture and BMSCs for surgical repair of completely transected spinal cord in rats

摘要

Introduction: Since the adult central nervous system is generally believed to fail to spontaneously regenerate after physical injury, clinical management of spinal cord injury represents a huge medical challenge. To date, many experimental researches have reported different strategies for spinal cord injury repair. Among these experimental endeavors, tissue engineering approaches attract great research interest due to their combined use of neural scaffolds and bioactive cues. In this study, several tissue-engineered nerve grafts were used to bridge the spinal cord gap for comparing their efficacy to promote spinal cord injury repair. Out of them, a composite nerve graft was engineered by incorporating bone marrow stromal cells (BMSCs) of rat to a chitosan-based scaffold, whose architecture was intended to be well-matched with the anatomy of spinal cord (Fig. 1 B). We assumed that this unique scaffold architecture might guide the regularly aligned regrowth of gray matter and major descending tracts within the circumferential white matter and allow segregative regeneration of functional pathways. Materials & Methods: The spinal cord of adlut Sprague Dawley (SD) rats was transected about 5 mm from the level of T8 toward caudal end and completely removed. The animals were randomly divided into four groups (n=10 each) to receive different treatments. In groups A, B, C and D the spinal cord gap was bridged by partition-type tube scaffold (PtTS) (Fig. 1 B), hollow tube scaffold (HTS) (Fig.1 A), PtTS with BMSCs (10~6/ml × 10 u l), and HTS with BMSCs (10~6/ml × 10 μl) respectively. Twenty-four weeks after implantation, a set of behavioral, functional and histological assessments were carried out to evaluate the repair outcome. Results& Discussion: The data from quantitative CatWalk analysis showed group C was significantly higher than that for other 3 implanted groups or non-implanted group. The results of motor evoked potential (MEP) measurements showed in group C MEPs were recorded on stimulation either of the cerebral cortex or the lower spinal cord injury site; however, in other 3 implanted groups or non-implanted group, MEPs were recorded only on stimulation of the lower spinal cord injury site. Immunohistochemistry showed in groups B and D, NF-positive nerve fibers were present at the rostral and caudal segments of the spinal cord, respectively, but they were arranged irregularly with folding into random coils. In groups A and C, NF-positive nerve fibers were found to locate in 2 descending tracts (corticorspinal tracts and rubrospinal tracts) at the rostral and caudal segments of the spinal cord, respectively, displaying an ordered arrangement into bundles. The results suggested that the combined use of chitosan as the scaffold biomaterial, a spinal cord-mimicking partition-type as the scaffold architecture, and BMSCs as the bioactive component might probably create synergetic promotion on spinal cord regeneration in that the composite nerve graft yielded significantly better results in axon regeneration and function restoration as compared to its scaffold alone or another hollow tube scaffold alone. Conclusion: Combined use of spinal cord-mimicking partition type scaffold architecture and BMSCs provided significantly better results in axon regeneration and function restoration as compared to the PtTS or HTS alone for surgical repair of completely transected spinal cord in rats.