Allogeneic stromal cell implantation in brain tissue leads to robust microglial activation

Abstract

Although adult and embryonic stem cell-based therapy for central nervous system (CNS) injury is being developed worldwide, less attention is given to the immunological aspects of allogeneic cell implantation in the CNS. The latter is of major importance because, from a practical point of view, future stem cell-based therapy for CNS injury will likely be performed using well-characterised allogeneic stem cell populations. In this study, we aimed to further describe the immunological mechanism leading to rejection of allogeneic bone marrow-derived stromal cells (BM-SC) after implantation in murine CNS. For this, we first investigated the impact of autologous and allogeneic BM-SC on microglia activation in vitro. Although the results indicate that both autologous and allogeneic BM-SC do not activate microglia themselves in vitro, they also do not inhibit activation of microglia after exogenous stimuli in vitro. Next, we investigated the impact of allogeneic BM-SC on microglia activation in vivo. In contrast to the in vitro observations, microglia become highly activated in vivo after implantation of allogeneic BM-SC in the CNS of immune-competent mice. Moreover, our results suggest that microglia, rather than T-cells, are the major contributors to allograft rejection in the CNS. Within the next decades, ischaemic and traumatic injuries to the central nervous system (CNS) will surpass many diseases worldwide as a major cause of death or disability, 1-3 and will have an enormous socio-economical impact on our society. The main physiopathological processes leading to neural cell loss after trauma are necrosis and apoptosis. In addition, activated immune cells can cause major secondary damage to the CNS through secretion of neurotoxic molecules. 4 Recently, transplantation of bone marrow-derived stromal cells (BM-SC) has been proposed as a potential cell therapy after neurotrauma. 5,6 Following this strategy, it is believed that BM-SC can prevent apoptosis of neural cell types and can stimulate proliferation and/or differentiation of endogenous neural stem cells in order to compensate for the necrotic cell loss. Ideally, such a cell therapy strategy should be performed using autologous BM-SC in order to prevent immunological rejection of the cell populations implanted. For clinical applications, therapeutic intervention after neurotrauma is likely to be urgent in order to reduce secondary ischaemic and traumatic stress. Therefore, clinical applications are likely to concentrate on the use of allogeneic BM-SC. The use of such 'off-the-shelf' stem cell preparations might provide several advantages over the use of autologous stem cell preparations as they can be pre-manipulated and/or screened for increased effectiveness (for example, regenerative capacity) without adverse effects (for example, tumorigenicity). Several reports ascribe multiple immunosuppressive properties to 7,8 but the immune-privileged status of these cells in vivo remains controversial. [9][10][11] Multiple studies, including our own work, describe the...

Transplantation of Enteric Neural Stem/Progenitor Cells into the Irradiated Young Mouse Hippocampus

“…4F). This feature of glial reactivity (both microglia and astroglia) was seen as a sign of rejection of mesenchymal allografts, even in the absence of T-lymphocyte involvement (11,55). Given that we used syngeneic ENSPCs, and no T-cells (CD3 + cells) were seen (Fig.…”

“…However, assuming that labeling indicates that the cells, or their progeny, were grafted, survival was lower for ENSPCs than BNSPCs. Death of transplanted cells is a major hindrance for cell therapy (31), because of the small number of remaining cells to be incorporated, because of the local reaction caused by dying cells (55), and because of the structural changes incurred (48). Long-term studies have revealed a low yield of grafted cells over time (2,45).…”

Clinical Potential of Intravenous Neural Stem Cell Delivery for Treatment of Neuroinflammatory Disease in Mice?

“…However, the use of allogeneic cell implants implies the need for immune suppression (e.g., towards inflammatory lesions (7,26,39). Although several studies reported on a beneficial effect of IV admincyclosporine A, CsA) in order to avoid acute or chronic rejection of cellular transplant in the CNS, as previously istered autologous NSCs on the clinical course of EAE (37,56), recent reports indicate that most-if not all-IV demonstrated by us (8,47,52) and others (9,28). Therefore, in the second therapeutically oriented part of this administered cells do not enter the CNS, but exert their therapeutic effect via immunomodulatory mechanisms study, we focus on the regenerative potential of IV administered allogeneic NSCs on EAE disease progression throughout the peripheral immune system (6,15,38).…”

“…All surgical interventions were performed under sterImmunofluorescence Microscopy ile conditions as previously described (8,52). Briefly, mice were anesthetized by an IP injection of a ketamine Immunofluorescence staining of NSC cultures, differentiated NSC cultures, BMSC cultures, and primary as-(80 mg/kg) + xylazine (16 mg/kg) mixture and placed in a mouse stereotactic frame.…”

“…Histological analysis was performed according to previously optimized procedures (8,47,52). Briefly, mice In Vivo Magnetic Resonance Imaging were deeply anesthetized in an induction chamber by inhalation of an isoflurane (4%), oxygen (0.5 L/min), Imaging was performed on a horizontal magnetic resonance imaging (MRI) system (Biospec 94/20 USR, and nitrogen (1 L/min) mixture for 2 min, and euthanized by cervical dislocation.…”