Accumulating evidence shows alterations in the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) in ALS patients and in animal models of disease, mainly by endothelial cell (EC) damage. Repair of the altered barrier in the CNS by replacement of ECs via cell transplantation may be a new therapeutic approach for ALS. Recently, we demonstrated positive effects towards BSCB repair by intravenous administration of unmodified human bone marrow CD34 (hBM34) cells at different doses into symptomatic ALS mice. However, particular benefits of these transplanted cells on microvascular integrity in symptomatic ALS mice are still unclear. The aim of the present study was to determine the structural and functional spinal cord capillary integrity in symptomatic ALS mice after intravenous administration of hBM34 cells. The G93A mice at 13 weeks of age intravenously received one of three different cell doses (5 × 10, 5 × 10, or 1 × 10) and were euthanized at 17 weeks of age (4 weeks post-transplant). Control groups were media-treated and non-carrier mutant SOD1 gene mice. Capillary ultrastructural (electron microscopy), immunohistochemical (laminin and HuNu), and histological (myelin and capillary density) analyses were performed in the cervical and lumbar spinal cords. Capillary permeability in the spinal cords was determined by Evans Blue (EB) injection. Results showed significant restoration of ultrastructural capillary morphology, improvement of basement membrane integrity, enhancement of axonal myelin coherence, and stabilization of capillary density in the spinal cords primarily of ALS mice receiving the high dose of 1 × 10 cells. Moreover, substantial reduction of parenchymal EB levels was determined in these mice, confirming our previous results on capillary permeability. Additionally, transplanted cells were detected in blood smears of sacrificed late symptomatic mice by HuNu marker. Altogether, these results provide novel evidence that unmodified bone marrow hematopoietic stem cell treatment at optimal dose might be beneficial for structural and functional repair of the damaged BSCB in advanced stage of ALS, potentially resulting in delayed disease progression by increased motor neuron survival.

Convincing evidence demonstrated impairment of the blood-spinal cord barrier (BSCB) in Amyotrophic Lateral Sclerosis (ALS), mainly by endothelial cell (EC) alterations. Replacing damaged ECs by cell transplantation is a potential barrier repair strategy. Recently, we showed that intravenous (iv) administration of human bone marrow CD34 + (hBM34 + ) cells into symptomatic ALS mice benefits BSCB restoration and postpones disease progression. However, delayed effect on motor function and some severely damaged capillaries were noted. We hypothesized that hematopoietic cells from a restricted lineage would be more effective. This study aimed to establish the effects of human bone marrow-derived endothelial progenitor cells (hBMEPCs) systemically transplanted into G93A mice at symptomatic disease stage. Results showed that transplanted hBMEPCs significantly improved behavioral disease outcomes, engrafted widely into capillaries of the gray/white matter spinal cord and brain motor cortex/brainstem, substantially restored capillary ultrastructure, significantly decreased EB extravasation into spinal cord parenchyma, meaningfully re-established perivascular astrocyte end-feet, and enhanced spinal cord motor neuron survival. These results provide novel evidence that transplantation of hBMEPCs effectively repairs the BSCB, potentially preventing entry of detrimental peripheral factors, including immune/inflammatory cells, which contribute to motor neuron dysfunction. Transplanting EC progenitor cells may be a promising strategy for barrier repair therapy in this disease.

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Convincing evidence of blood-spinal cord barrier (BSCB) alterations has been demonstrated in amyotrophic lateral sclerosis (ALS) and barrier repair is imperative to prevent motor neuron dysfunction.We showed benefits of human bone marrow-derived CD34+ cells (hBM34+) and endothelial progenitor cells (hBM-EPCs) intravenous transplantation into symptomatic G93A SOD1 mutant mice on barrier reparative processes. These gains likely occurred by replacement of damaged endothelial cells, prolonging motor neuron survival. However, additional investigations are needed to confirm the effects of administered cells on integrity of the microvascular endothelium. The aim of this study was to determine tight junction protein levels, capillary pericyte coverage, microvascular basement membrane, and endothelial F-actin status in spinal cord capillaries of G93A SOD1 mutant mice treated with human bone marrow-derived stem cells. Tight junction proteins were detected in the spinal cords of cell-treated vs. nontreated mice via western blotting at four weeks post-transplant. Capillary pericyte, basement membrane laminin, and endothelial F-actin magnitudes were determined in cervical/lumbar spinal cord tissues in ALS mice, including controls, by immunohistochemistry and fluorescent staining. Results showed that celltreated vs. media-treated ALS mice substantially increased tight junction protein levels, capillary pericyte coverage, basement membrane laminin immunoexpressions, and endothelial cytoskeletal F-actin fluorescent expressions. The greatest benefits were detected in mice receiving hBM-EPCs vs. hBM34 + cells. These study results support treatment with a specific cell type derived from human bone marrow towards BSCB repair in ALS. Thus, hBM-EPCs may be advanced for clinical applications as a cellspecific approach for ALS therapy through restored barrier integrity.

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