Reduction of cystic cavity, promotion of axonal regeneration and sparing, and functional recovery with transplanted bone marrow stromal cell–derived Schwann cells after contusion injury to the adult rat spinal cord

Abstract

Object The authors previously reported that Schwann cells (SCs) could be derived from bone marrow stromal cells (BMSCs) in vitro and that they promoted axonal regeneration of completely transected rat spinal cords in vivo. The aim of the present study is to evaluate the efficacy of transplanted BMSC-derived SCs (BMSC-SCs) in a rat model of spinal cord contusion, which is relevant to clinical spinal cord injury. Methods Bone marrow stromal cells were cultured as plastic-adherent cells from the bone marrow of GFPtransgenic rats. The BMSC-SCs were derived from BMSCs in vitro with sequential treatment using beta-mercaptoethanol, all-trans-retinoic acid, forskolin, basic fibroblast growth factor, platelet derived–growth factor, and heregulin. Schwann cells were cultured from the sciatic nerve of neonatal, GFP-transgenic rats. Immunocytochemical analysis and the reverse transcriptase–polymerase chain reaction were performed to characterize the BMSC-SCs. For transplantation, contusions with the New York University impactor were delivered at T-9 in 10- to 11-week-old male Wistar rats. Four groups of rats received injections at the injury site 7 days postinjury: the first received BMSCSCs and matrigel, a second received peripheral SCs and matrigel, a third group received BMSCs and matrigel, and a fourth group received matrigel alone. Histological and immunohistochemical studies, electron microscopy, and functional assessments were performed to evaluate the therapeutic effects of BMSC-SC transplantation. Results Immunohistochemical analysis and reverse transcriptase–polymerase chain reaction revealed that BMSC-SCs have characteristics similar to SCs not only in their morphological characteristics but also in their immunocytochemical phenotype and genotype. Histological examination revealed that the area of the cystic cavity was significantly reduced in the BMSC-SC and SC groups compared with the control rats. Immunohistochemical analysis showed that transplanted BMSCs, BMSC-SCs, and SCs all maintained their original phenotypes. The BMSC-SC and SC groups had a larger number of tyrosine hydroxilase–positive fibers than the control group, and the BMSC-SC group had more serotonin-positive fibers than the BMSC or control group. The BMSC-SC group showed significantly better hindlimb functional recovery than in the BMSC and control group. Electron microscopy revealed that transplanted BMSC-SCs existed in association with the host axons. Conclusions Based on their findings, the authors concluded that BMSC-SC transplantation reduces the size of the cystic cavity, promotes axonal regeneration and sparing, results in hindlimb functional recovery, and can be a useful tool for spinal cord injury as a substitute for SCs.