Neural stem/progenitor cells modulate immune responses by suppressing T lymphocytes with nitric oxide and prostaglandin E2

Cross-talk between CD4+ T-cells and neural stem/progenitor cells

Immune-neural interactions dictate both lesion formation and repair in multiple sclerosis (MS). MS pathogenesis is mediated by the interplay of invading immune cells, neurons, glia, and endogenous stores of neural stem/progenitor cells (NPCs). However, the signals important in this cross-talk are not well defined. We utilized a co-culture method and flow cytometric analysis capable of detecting outcomes for both cell types. Here we describe the effects of NPCs on three different CD4+ subtypes (Th1, Th2, and Th17) and vice versa. Utilizing lpr (Fas receptor-deficient) and gld (Fas ligand-deficient) NPC lines, we further define the role of Fas in this neuroimmune cross-talk. We show that only the Th1 subtype is capable of inducing NPC cell death, and this is independent of Fas activation. Conversely, NPCs specifically kill pro-inflammatory Th1 and Th17 cells in a contact-dependent manner without affecting Th2 survival. Further investigation into these effects revealed that FasL expressed by NPCs mediates Th17 apoptosis. Additionally NPC/T-cell cross-talk modulates FasL expression in both cell types, while Fas receptor levels remains static. These findings illuminate the direct neuropathogenic effects of T-cells, as well as help define the immunomodulatory capacity of NPCs. We have elucidated novel interactions that may be critical in MS pathogenesis.

Trophic and immunoregulatory properties of neural precursor cells: benefit for intracerebral transplantation

Intracerebral xenotransplantation of porcine fetal neuroblasts (pNB) is considered as an alternative to human neuroblasts for the treatment of neurodegenerative diseases. However, pNB are systematically rejected, even in an immunoprivileged site such as the brain. Within this context, neural stem/precursor cells (NSPC), which were suggested as exhibiting low immunogenicity, appeared as a useful source of xenogeneic cells. To determine the advantage of using porcine NSPC (pNSPC) in xenotransplantation, pNB and pNSPC were grafted into the striatum of rats without immunosuppression. At day 63, all the pNB were rejected while 40% of the rats transplanted with pNSPC exhibited large and healthy grafts with numerous pNF70-positive cells. The absence of inflammation at day 63 and the occasional presence of T cells in pNSPC grafts evoked a weak host immune response which might be partly due to the immunosuppressive properties of the transplanted cells. T cell proliferation assays confirmed such a hypothesis by revealing an inhibitory effect of pNSPC on T cells through a soluble factor. In addition to their immunosuppressive effect, in contrast to pNB, very few pNSPC differentiated into tyrosine hydroxylase-positive neurons but the cells triggered an intense innervation of the striatum by rat dopaminergic fibers coming from the substantia nigra. Further experiments will be required to optimize the use of pNSPC in regenerative medicine but here we show that their immunomodulatory and trophic activities might be of great interest for restorative strategies. This article is part of a Special Issue entitled "Interaction between repair, disease, & inflammation."

Co-graft of allogeneic immune regulatory neural stem cells (NPC) and pancreatic islets mediates tolerance, while inducing NPC-derived tumors in mice

BACKGROUND

Data available on the immunomodulatory properties of neural stem/precursor cells (NPC) support their possible use as modulators for immune-mediated process. The aim of this study was to define whether NPC administered in combination with pancreatic islets prevents rejection in a fully mismatched allograft model.

METHODOLOGY/PRINCIPAL FINDING

Diabetic Balb/c mice were co-transplanted under the kidney capsule with pancreatic islets and GFP(+) NPC from fully mismatched C57BL/6 mice. The following 4 groups of recipients were used: mice receiving islets alone; mice receiving islets alone and treated with standard immunosuppression (IL-2Ralpha chain mAbs + FK506 + Rapamycin); mice receiving a mixed islet/NPC graft under the same kidney capsule (Co-NPC-Tx); mice receiving the islet graft under the left kidney capsule and the NPC graft under the right kidney capsule (NPC-Tx). Our results demonstrate that only the co-transplantation and co-localization of NPC and islets (Co-NPC-Tx) induce stable long-term graft function in the absence of immunosuppression. This condition is associated with an expansion of CD4(+)CD25(+)FoxP3(+) T regulatory cells in the spleen. Unfortunately, stable graft function was accompanied by constant and reproducible development of NPC-derived cancer mainly sustained by insulin secretion.

CONCLUSION

These data demonstrate that the use of NPC in combination with islets prevents graft rejection in a fully mismatched model. However, the development of NPC-derived cancer raises serious doubts about the safety of using adult stem cells in combination with insulin-producing cells outside the original microenvironment.

Immune influence on adult neural stem cell regulation and function

Neural stem cells (NSCs) lie at the heart of central nervous system development and repair, and deficiency or dysregulation of NSCs or their progeny can have significant consequences at any stage of life. Immune signaling is emerging as one of the influential variables that define resident NSC behavior. Perturbations in local immune signaling accompany virtually every injury or disease state, and signaling cascades that mediate immune activation, resolution, or chronic persistence influence resident stem and progenitor cells. Some aspects of immune signaling are beneficial, promoting intrinsic plasticity and cell replacement, while others appear to inhibit the very type of regenerative response that might restore or replace neural networks lost in injury or disease. Here we review known and speculative roles that immune signaling plays in the postnatal and adult brain, focusing on how environments encountered in disease or injury may influence the activity and fate of endogenous or transplanted NSCs.