The Effects Of Combinatorial Transplantation Of Polarized Macrophages And Spinal-cord-derived Neural Stem Cells On Spinal Cord Injury

Ⅰ Polarized macrophages have distinct roles in the differentiation and migration of embryonic spinal-cord-derived neural stem cells after grafting to injured sites of spinal cordSpinal cord injury(SCI) frequently provokes serious detrimental outcomes because neuronal regeneration is limited in the central nervous system(CNS). Thus, the creation of a permissive environment for transplantation therapy with neural stem/progenitor cells(NS/PCs) is a promising strategy to replace lost neuronal cells, promote repair and stimulate functional plasticity after SCI. Macrophages are important SCI-associated inflammatory cells and a major source of secreted factors that modify the lesion milieu. Here, we used conditional medium(CM) from bone marrow-derived M1 or M2 polarized macrophages to culture murine NS/PCs. The NS/PCs showed enhanced astrocytic vs. neuronal/oligodendrocytic differentiation in the presence of M1- vs. M2-CM. Similarly, co-transplantation of NS/PCs with M1 and M2 macrophages into intact or injured murine spinal cord increased the number of engrafted NS/PC-derived astrocytes and neurons/oligodendrocytes, respectively. Furthermore, when co-transplantated with M2 macrophages, the NS/PC derived neurons integrated into the local circuitry and enhanced locomotor recovery following SCI. Interesting, engrafted M1 macrophages promoted long-distance rostral migration of NS/PC-derived cells in a chemokine(C-X-C motif) receptor 4(CXCR4)-dependent manner, while engrafted M2 macrophages resulted in limited cell migration of NS/PC-derived cells. Altogether, these findings suggest that the co-transplantation of NS/PCs together with polarized macrophages could constitute a promising therapeutic approach for SCI repair.Ⅱ The effects of spinal-cord-derived neural stem cells on macrophage polarityNS/PCs are very promising candidates for CNS therapy, having shown strong immunomodulatory capacity following CNS transplantation. Microglia/Macrophage cells are the key mediators of immune response in the CNS. However, the mechanism by which NS/PCs modulate the immune profile of the CNS as well as their cross-talk with microglia/Macrophage still needs explanation. We used two types of mice(AR-/-、PD1-/-) to evaluate the effect of spinal-cord-derived neural stem cells on M1 and M2 macrophage polarization in vitro and in vivo with the aim of clarifying how engrafted stem cells influence the initiation and maintenance of immune responses, while providing insights into how the understanding of the mechanisms regulating this reciprocal relationship might contribute to the development of therapeutic strategies for regenerative neurosciences.Our data in vitro indicated that spinal-cord-derived neural stem cells when had direct cell–cell contact with primary M1 macrophages significantly reduced the number of CD11b+CD86+ M1 macrophage cells. This immunomodulatory effect was also observed in co-cultures in a cell-to-cell contact manner where spinal-cord-derived neural stem cells with M1 mixed M2 macrophages. Such experiments were designed to mimick the in vivo damaged environment.Modulation by spinal-cord-derived neural stem cells in our in vivo a study shows they decrease markers of M1-macrophage cells(smaller i NOS) at 1w. Additionally they increased the number of Neu N+ cells in the injury site following transplantation and enhanced locomotor recovery following SCI. NS/PCs cultured by M1-CM have a low expression of CCR2/MCP-1and CCR5/MIP-1, but M1 macrophage have a high expression of CCR2/MCP-1and CCR5/MIP-1. However, it is still to elucidate Whether they have interactions lead to the above immunomodulatory effect.Ⅲ Tissue specificity of neural stem cellsA number of experimental studies showing positive results with NS/PCtransplantation for several neurodegenerative disorders in CNS. However, clear mechanisms have not been elucidated.We found that the primary culture of NS/PC drived from hippocamp and spinal cord at different stages have a distinct speed of proliferation and resistance to Acutase. Here we firstly verify the difference of proliferation speed between two types of NS/PCs, and to elucidate relative mechanisms.Cell-cell adherens junctions(AJs), the most common(indeed, essentially ubiquitous) type of intercellular adhesions, are important for maintaining tissue architecture and cell polarity and can limit cell movement and proliferation. We detected the expression of adhesive mo lecules in intact or injury hippocamp /spinal cord-drived NS/PCs.Our date shows that the number of Brd U/Ki67/Phh3-positive cells in hippocamp–NS/PCs is more than spinal cord-drived NS/PCs;NS/PC drived from injury spinal cord have more Brd U/Ki67-positive cells than from intact spinal cord. These data indicate spinal cord stem cell have a slower proliferation than hippocamp and injury can accelerate the expansion of NS/PCs. Additionally, the expression of relative adhesive molecules(N-cadherin,β-catenin, Rho A, Pax6) in spinal cord-drived NS/PCs is higher than hippocamp–drived NS/PCs.Maybe it is one reason which effect the speed of NS/PCs proliferation. Further studies are needed to understand their rols in cell adhesion, proliferation and other other else characters of NS/PC.