Intracerebral cytokine profiles in adult rats grafted with neural tissue of different immunological disparity

Microglia-secreted TNF-α affects differentiation efficiency and viability of pluripotent stem cell-derived human dopaminergic precursors

Disease is a neurodegenerative disorder characterised by the progressive loss of dopaminergic cells of the substantia nigra pars compacta. Even though successful transplantation of dopamine-producing cells into the striatum exhibits favourable effects in animal models and clinical trials; transplanted cell survival is low. Since every transplant elicits an inflammatory response which can affect cell survival and differentiation, we aimed to study in vivo and in vitro the impact of the pro-inflammatory environment on human dopaminergic precursors. We first observed that transplanted human dopaminergic precursors into the striatum of immunosuppressed rats elicited an early and sustained activation of astroglial and microglial cells after 15 days' post-transplant. This long-lasting response was associated with Tumour necrosis factor alpha expression in microglial cells. In vitro, conditioned media from activated BV2 microglial cells increased cell death, decreased Tyrosine hydroxylase-positive cells and induced morphological alterations on human neural stem cells-derived dopaminergic precursors at two differentiation stages: 19 days and 28 days. Those effects were ameliorated by inhibition of Tumour necrosis factor alpha, a cytokine which was previously detected in vivo and in conditioned media from activated BV-2 cells. Our results suggest that a pro-inflammatory environment is sustained after transplantation under immunosuppression, providing a window of opportunity to modify this response to increase transplant survival and differentiation. In addition, our data show that the microglia-derived pro-inflammatory microenvironment has a negative impact on survival and differentiation of dopaminergic precursors. Finally, Tumour necrosis factor alpha plays a key role in these effects, suggesting that this cytokine could be an interesting target to increase the efficacy of human dopaminergic precursors transplantation in Parkinson's Disease.

Monoclonal antibody-mediated immunosuppression enables long-term survival of transplanted human neural stem cells in mouse brain

BACKGROUND

As the field of stem cell therapy advances, it is important to develop reliable methods to overcome host immune responses in animal models. This ensures survival of transplanted human stem cell grafts and enables predictive efficacy testing. Immunosuppressive drugs derived from clinical protocols are frequently used but are often inconsistent and associated with toxic side effects. Here, using a molecular imaging approach, we show that immunosuppression targeting costimulatory molecules CD4 and CD40L enables robust survival of human xenografts in mouse brain, as compared to conventional tacrolimus and mycophenolate mofetil.

METHODS

Human neural stem cells were modified to express green fluorescent protein and firefly luciferase. Cells were implanted in the fimbria fornix of the hippocampus and viability assessed by non-invasive bioluminescent imaging. Cell survival was assessed using traditional pharmacologic immunosuppression as compared to monoclonal antibodies directed against CD4 and CD40L. This paradigm was also implemented in a transgenic Alzheimer's disease mouse model.

RESULTS

Graft rejection occurs within 7 days in non-immunosuppressed mice and within 14 days in mice on a traditional regimen. The addition of dual monoclonal antibody immunosuppression extends graft survival past 7 weeks (p < .001) on initial studies. We confirm dual monoclonal antibody treatment is superior to either antibody alone (p < .001). Finally, we demonstrate robust xenograft survival at multiple cell doses up to 6 months in both C57BL/6J mice and a transgenic Alzheimer's disease model (p < .001). The dual monoclonal antibody protocol demonstrated no significant adverse effects, as determined by complete blood counts and toxicity screen.

CONCLUSIONS

This study demonstrates an effective immunosuppression protocol for preclinical testing of stem cell therapies. A transition towards antibody-based strategies may be advantageous by enabling stem cell survival in preclinical studies that could inform future clinical trials.

Current Status on Canine Foetal Fluid and Adnexa Derived Mesenchymal Stem Cells

Effective standards of care treatment guidelines have been developed for many canine diseases. However, a subpopulation of patients is partially or completely refractory to these protocols, so their owners seek novel therapies such as treatments with MSCs. Although in dogs, as with human medicine, the most studied MSCs sources have been bone marrow and adipose tissue, in recent years, many researchers have drawn attention towards alternative sources, such as foetal adnexa and fluid, since they possess many advantages over bone marrow and adipose tissue. Foetal adnexa and fluid could be considered as discarded material; therefore, sampling is non-invasive, inexpensive and free from ethical considerations. Furthermore, MSCs derived from foetal adnexa and fluid preserve some of the characteristics of the primitive embryonic layers from which they originate and seem to present immune-modulatory properties that make them a good candidate for allo- and xenotransplantation. The aim of the present review is to offer an update on the state of the art on canine MSCs derived from foetal adnexa and fluid focusing on the findings in their clinical setting.

Concise Review: Innate and Adaptive Immune Recognition of Allogeneic and Xenogeneic Cell Transplants in the Central Nervous System

Over the last 30 years, numerous allogeneic and xenogeneic cell grafts have been transplanted into the central nervous system (CNS) of mice and men in an attempt to cure neurological diseases. In the early studies, human or porcine embryonic neural cells were grafted in the striatum of animals or patients in an attempt to replace lost neurons. Although the immune-privileged status of the brain as a recipient organ was widely accepted, it rapidly became evident that CNS-grafted allogeneic and xenogeneic cells could be recognized and rejected by the immune system, resulting in poor neural graft survival and limited functional recovery. Since then, the CNS transplantation field has witnessed a sharp rise in the number of studies in which allogeneic and xenogeneic neural or mesenchymal stem cells (NSCs or MSCs, respectively) are transplanted, predominantly aiming at providing trophic stimulation and promoting endogenous repair of the brain. Interestingly, in many recent NSC and MSC-based publications functional improvement was used as the principal measure to evaluate the success of cell transplantation, while the fate of transplanted cells remained largely unreported. In this review, we first attempt to understand why primary neural cell isolates were largely substituted for NSCs and MSCs in cell grafting studies. Next, we review the current knowledge on the immune mechanisms involved in the recognition and rejection of allogeneic and xenogeneic cellular grafts in the CNS. Finally, we propose strategies to reduce graft immunogenicity and to improve graft survival in order to design improved cell-based CNS therapies. Stem Cells Translational Medicine 2017;6:1434-1441.

Cell therapy for Parkinson's disease: Functional role of the host immune response on survival and differentiation of dopaminergic neuroblasts

Parkinson's disease (PD) is a neurodegenerative disorder, whose cardinal pathology is the loss of dopaminergic neurons in the substantia nigra. Current treatments for PD have side effects in the long term and do not halt disease progression or regenerate dopaminergic cell loss. Attempts to compensate neuronal cell loss by transplantation of dopamine-producing cells started more than 30 years ago, leading to several clinical trials. These trials showed safety and variable efficacy among patients. In addition to variability in efficacy, several patients developed graft-induced dyskinesia. Nevertheless, they have provided a proof of concept that motor symptoms could be improved by cell transplantation. Cell transplantation in the brain presents several immunological challenges. The adaptive immune response should be abolished to avoid graft rejection by the host. In addition, the innate immune response will always be present after transplanting cells into the brain. Remarkably, the innate immune response can have dramatic effects on the survival, differentiation and proliferation of the transplanted cells, but has been hardly investigated. In this review, we analyze data on the functional effects of signals from the innate immune system on dopaminergic differentiation, survival and proliferation. Then, we discussed efforts on cell transplantation in animal models and PD patients, highlighting the immune response and the immunomodulatory treatment strategies performed. The analysis of the available data lead us to conclude that the modulation of the innate immune response after transplantation can increase the success of future clinical trials in PD by enhancing cell differentiation and survival. This article is part of a Special Issue entitled SI: PSC and the brain.

Identification of Neurexophilin 3 as a Novel Supportive Factor for Survival of Induced Pluripotent Stem Cell-Derived Dopaminergic Progenitors

Successful cell transplantation for Parkinson's disease (PD) depends on both an optimal host brain environment and ideal donor cells. We report that a secreted peptide, neurexophilin 3 (NXPH3), supports the survival of mouse induced pluripotent stem cell-derived (iPSC-derived) dopaminergic (DA) neurons in vitro and in vivo. We compared the gene expression profiles in the mouse striatum from two different environments: a supportive environment, which we defined as 1 week after acute administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and a nonsupportive environment, defined as 8 weeks after chronic administration of MPTP. NXPH3 expression was higher in the former condition and lower in the latter compared with untreated controls. When we injected mouse iPSC-derived neural cells along with NXPH3 into the mouse striatum, the ratio of tyrosine hydroxylase-positive DA neurons per graft volume was higher at 8 weeks compared with cell injections that excluded NXPH3. In addition, quantitative polymerase chain reaction analyses of the postmortem putamen revealed that the expression level of NXPH3 was lower in PD patients compared with normal controls. These findings will contribute to optimizing the host brain environment and patient recruitment in cell therapy for PD.

Comparison of mesenchymal stem cells derived from fat, bone marrow, Wharton's jelly, and umbilical cord blood for treating spinal cord injuries in dogs

Previous animal studies have shown that transplantation of mesenchymal stem cells (MSCs) into spinal cord lesions enhances axonal regeneration and promotes functional recovery. We isolated the MSCs derived from fat, bone marrow, Wharton's jelly and umbilical cord blood (UCB) positive for MSC markers and negative for hematopoietic cell markers. Their effects on the regeneration of injured canine spinal cords were compared. Spinal cord injury was induced by balloon catheter compression. Dogs with injured spinal cords were treated with only matrigel or matrigel mixed with each type of MSCs. Olby and modified Tarlov scores, immunohistochemistry, ELISA and Western blot analysis were used to evaluate the therapeutic effects. The different MSC groups showed significant improvements in locomotion at 8 weeks after transplantation (P<0.05). This recovery was accompanied by increased numbers of surviving neuron and neurofilament-positive fibers in the lesion site. Compared to the control, the lesion sizes were smaller, and fewer microglia and reactive astrocytes were found in the spinal cord epicenter of all MSC groups. Although there were no significant differences in functional recovery among the MSCs groups, UCB-derived MSCs (UCSCs) induced more nerve regeneration and anti-inflammation activity (P<0.05). Transplanted MSCs survived for 8 weeks and reduced IL-6 and COX-2 levels, which may have promoted neuronal regeneration in the spinal cord. Our data suggest that transplantation of MSCs promotes functional recovery after SCI. Furthermore, application of UCSCs led to more nerve regeneration, neuroprotection and less inflammation compared to other MSCs.

Functional recovery after spinal cord injury in dogs treated with a combination of Matrigel and neural-induced adipose-derived mesenchymal Stem cells

BACKGROUND AIMS

Previous studies have reported that scaffold or cell-based transplantation may improve functional recovery following spinal cord injury (SCI), but these results were based on neuronal regeneration and cell replacement. In this study, we investigated whether a combination of Matrigel and neural-induced mesenchymal stem cells (NMSC) improved hindlimb function in dogs with SCI, and what mechanisms were involved.

METHODS

We pre-differentiated canine adipose-derived mesenchymal stem cells into NMSC. A total of 12 dogs subjected to SCI procedures were assigned to one of the following three transplantation treatment groups: phosphate-buffered saline (PBS); Matrigel; or Matrigel seeded with NMSC. Treatment occurred 1 week after SCI. Basso, Beattie and Bresnahan (B.B.B.) and Tarlov scores, histopathology, immunofluorescence staining and Western blot analysis were used to evaluate the treatment effects.

RESULTS

Compared with dogs administered PBS or Matrigel alone, dogs treated with Matrigel + NMSC showed significantly better functional recovery 8 weeks after transplantation. Histology and immunochemical analysis revealed that the combination of Matrigel + NMSC reduced fibrosis from secondary injury processes and improved neuronal regeneration more than the other treatments. In addition, the combination of Matrigel + NMSC decreased the expression of inflammation and/or astrogliosis markers. Increased expressions of intracellular molecules related to neuronal extension, neuronal markers and neurotrophic factors were also found in the Matrigel + NMSC group. However, the expression of nestin as a neural stem cell marker was increased with Matrigel alone.

CONCLUSIONS

The combination of Matrigel + NMSC produced beneficial effects in dogs with regard to functional recovery following SCI through enhancement of anti-inflammation, anti-astrogliosis, neuronal extension and neuronal regeneration effects.

Exposure of foetal neural progenitor cells to IL-1β impairs their proliferation and alters their differentiation - a role for maternal inflammation?

During pregnancy, activation of the maternal immune system results in inflammation in the foetal nervous system. The causative agents are pro-inflammatory cytokines like interleukin-1β (IL-1β), produced by the foetus. In this study, we examine the effect of IL-1β on the proliferation and differentiation of neural progenitor cells (NPCs) to better understand its potential effects on the developing brain. We find that the IL-1β receptor (IL-1R1) is expressed in the ventral mesencephalon of the developing brain. Furthermore, IL-1R1 is expressed on Nestin-positive, Sox-2-positive NPCs. IL-1β treatment reduced the numbers of proliferating NPCs, an effect prevented by the IL-1R1 receptor antagonist. LDH and MTT assays, and western blot analysis for cleaved caspase 3 and poly(ADP-ribose) polymerase, confirmed that this was not due to an increase in cell death but rather an induction of differentiation. To further study the effects of IL-1β on cell fate determination, we differentiated NPCs in the presence and absence of IL-1β. Il-1β promoted gliogenesis and inhibited neurogenesis, an effect that required p38-MAPK kinase signalling. In summary, these data show that exposure of NPCs to IL-1β affects their development. This necessitates an examination of the consequences that maternal immune system activation during pregnancy has on the cellular architecture of the developing brain.

Development of histocompatible primate-induced pluripotent stem cells for neural transplantation

Immune rejection and risk of tumor formation are perhaps the greatest hurdles in the field of stem cell transplantation. Here, we report the generation of several lines of induced pluripotent stem cells (iPSCs) from cynomolgus macaque (CM) skin fibroblasts carrying specific major histocompatibility complex (MHC) haplotypes. To develop a collection of MHC-matched iPSCs, we genotyped the MHC locus of 25 CMs by microsatellite polymerase chain reaction analysis. Using retroviral infection of dermal skin fibroblasts, we generated several CM-iPSC lines carrying different haplotypes. We characterized the immunological properties of CM-iPSCs and demonstrated that CM-iPSCs can be induced to differentiate in vitro along specific neuronal populations, such as midbrain dopaminergic (DA) neurons. Midbrain-like DA neurons generated from CM-iPSCs integrated into the striatum of a rodent model of Parkinson's disease and promoted behavioral recovery. Importantly, neither tumor formation nor inflammatory reactions were observed in the transplanted animals up to 6 months after transplantation. We believe that the generation and characterization of such histocompatible iPSCs will allow the preclinical validation of safety and efficacy of iPSCs for neurodegenerative diseases and several other human conditions in the field of regenerative medicine.

Single and local blockade of interleukin-6 signaling promotes neuronal differentiation from transplanted embryonic stem cell-derived neural precursor cells

Safe and efficient transplantation of embryonic stem (ES) cells to the brain requires that local inflammatory and immune responses to allogeneic grafts are inhibited. To investigate cytokines that affect graft cell survival and differentiation, we used stromal cell-derived inducing activity to induce the differentiation of neural progenitor cells (NPCs) from mouse ES cells and transplanted the NPCs into mouse brain. Examination of surrounding brain tissue revealed elevated expression levels of interleukin (IL)-1β, IL-4, and IL-6 in response to NPC transplantation. Among these, only IL-6 reduced neuronal differentiation and promoted glial differentiation in vitro. When we added anti-IL-6 receptor antibodies to NPCs during transplantation, this single and local blockade of IL-6 signaling reduced the accumulation of host-derived leukocytes, including microglia. Furthermore, it also promoted neuronal differentiation and reduced glial differentiation from the grafted NPCs to an extent similar to that with systemic and continuous administration of cyclosporine A. These results suggest that local administration of anti-IL-6 receptor antibodies with NPCs may promote neuronal differentiation during the treatment of neurological diseases with cell replacement therapy.

Matrigel supports survival and neuronal differentiation of grafted embryonic stem cell-derived neural precursor cells

Cell replacement therapy holds great promise as a means of treating neurological disorders, including Parkinson's disease. However, one of the major obstacles to the success of this treatment is the low survival rate of grafted cells, which probably results from mechanical damage, acute inflammation, and immunological rejection. To overcome this problem, we investigated the effect of different types of extracellular matrix (ECM) on the survival and differentiation of embryonic stem (ES) cell-derived neural precursor cells (NPCs). We tested materials from natural sources, including collagen, ornithine/laminin, and growth factor-reduced Matrigel (gfrMG), as well as the synthetic biomaterial PuraMatrix, which consists of self-assembling polypeptides. GfrMG efficiently supported cell survival, migration, and neurite outgrowth in vitro and promoted proliferation of grafted cells in vivo, resulting in larger graft volume and an increase in the number of TH-positive dopaminergic neurons in the graft. GfrMG did not induce dopaminergic differentiation directly; rather, it reduced the invasion of pan-leukocytic CD45-positive cells into the graft. Insofar as the inflammatory or immune response in the host brain inhibits neuronal differentiation of grafted NPCs, gfrMG may increase the number of TH-positive cells by suppressing this effect. Thus, gfrMG appears to provide a suitable scaffold that supports survival and differentiation of NPCs. However, because it is derived from mouse sarcomas, a human-derived matrix or synthetic biomaterial must be developed for clinical applications.

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.

Immune or inflammatory response by the host brain suppresses neuronal differentiation of transplanted ES cell-derived neural precursor cells

Embryonic stem (ES) cells are a promising donor source for transplantation therapy, but several problems must be solved before they can be clinically useful. One of these is the host immune reaction to allogeneic grafts. In this article, we examine the effect of the host immune reaction on survival and differentiation of grafted ES cell-derived neural precursor cells (NPCs). We induced NPCs from mouse ES cells by stromal cell-derived inducing activity and then transplanted them into mouse brains with or without administering the immunosuppressant cyclosporine A (CsA). Two and 8 weeks following transplantation, the accumulation of host-derived microglia/macrophages and lymphocytes was observed around the graft. This effect was reduced by CsA treatment, although no significant difference in graft volume was observed. These data suggest that an immune response occurs in allografts of ES cell-derived NPCs. Intriguingly, however, the ratio of neurons to astrocytes in the graft was higher in immunosuppressed mice. Because inflammatory or immune cells produce various cytokines, we examined the effect of IL-1beta, IL-6, IFN-gamma, and TNF-alpha on the differentiation of NPCs in vitro. Only IL-6 promoted glial cell fate, and this effect could be reversed by the addition of an IL-6 neutralizing antibody. These results suggest that allogeneic ES cell-derived NPCs can cause an immune response by the host brain, but it is not strong enough to reject the graft. More important, activated microglia and lymphocytes can suppress neuronal differentiation of grafted NPCs in vivo by producing cytokines such as IL-6.

Sustained survival of xenografted human neural stem/progenitor cells in experimental brain trauma despite discontinuation of immunosuppression

Neural stem cells have emerged as a promising therapeutic tool in CNS disease and injuries. In the clinical setting, cultured human neural stem/progenitor cells (hNSC) are an attractive possibility for transplantation to the damaged brain. However, transplantation of hNSC requires toxic immunosuppressive treatment to avoid rejection. The aim of the current study was to evaluate if shortening the duration of immunosuppression by cyclosporin A would affect hNSC survival and differentiation after transplantation to the site of a focal brain injury in the rat. hNSC were xenografted to the hippocampus and the medial limit of an experimentally induced cortical contusion. The animals received immunosuppression for either 6 or 3 weeks or no immunosuppression. The status of the grafted human cells was analysed by immunohistochemistry. No statistically significant differences were observed between the two immunosuppressed groups regarding graft survival, migration or proliferation at 6 weeks post-transplantation. In contrast, the graft survival was extremely poor in the non-immunosuppressed group. Furthermore, the expression of the differentiation markers nestin, neuronal nuclei (NeuN) and glial fibrillary acidic protein (GFAP) in the transplanted cells did not differ significantly between the two immunosuppressed groups. Moreover, a fourth group of eight animals that were immunosuppressed for 3 weeks were allowed to survive for 6 months. Five of these rats demonstrated robust graft survival in the hippocampus and scattered cells in the cortex. This study demonstrates the importance of immunosuppression but also the possibility of shortening immunosuppression without impacting on the phenotype of the grafted hNSC.

The high integration and differentiation potential of autologous neural stem cell transplantation compared with allogeneic transplantation in adult rat hippocampus

Cell therapy is thought to have a central role in restorative therapy, which aims to restore function to the damaged nervous system. The purpose of this study was to establish an autologous neural stem cell (NSC) transplantation model using adult rats and to compare survival, migration, and differentiation between this system and allogeneic NSC transplantation. Furthermore, we compared the immunologic response of the host tissue between autologous and allogeneic transplantation. NSCs were removed from the subventricular zone of adult Fischer 344 rats using stereotactic methods. NSCs were expanded and microinjected into normal hippocampus in the autologous brain. Allogeneic NSC (derived from adult Wistar rats) transplantation was performed using the same procedure, and hippocampal sections were analyzed immunohistologically 3 weeks post-transplantation. The cell survival and migration rate were higher for autologous transplantation than for allogeneic transplantation, and the neuronal differentiation rate in the autologous transplanted cells far exceeded that of allogeneic transplantation. Furthermore, there was less astrocyte and microglia reactivity in the host tissue of the autologous transplantation compared with allogeneic transplantation. These findings demonstrate that immunoreactivity of the host tissue strongly influences cell transplantation in the CNS as the autologous transplantation did not induce host tissue immunoreactivity; the microenvironment was essentially maintained in an optimal condition for the transplanted cells.

Increased capacity for axonal outgrowth using xenogenic tissue in vitro and in a rodent model of Parkinson's disease

BACKGROUND

It has previously been proposed that grafted neurons may have the potential for more extensive axonal outgrowth in a xenogenic environment, and may thus possess a primary advantage over allografts in central nervous system repair and circuit reconstruction. In order to directly address this issue, fibre outgrowth from primary dopaminergic neurons was examined both in vitro and in vivo in an allogenic or xenogenic environment. A combination of species was used to circumvent problems relating to different gestational/developmental periods for such cells.

METHODS

In the in vitro experiments, axon length was measured over 2 to 14 days in cultures derived from either rat or mouse ventral mesencephalon (VM) tissue co-cultured onto either a monolayer of the rat Neu7 inhibitory cell line or fetal rodent cortical tissue. In the in vivo experiments, fetal rat or mouse VM tissue was transplanted into the striatum or substantia nigra of 6-hydroxydopamine-lesioned athymic rats. Amphetamine-induced rotations were observed for 3 months post-transplantation and the degree of graft-mediated neurite outgrowth was analyzed.

RESULTS

Embryonic VM manifested a greater capacity for neurite formation and outgrowth on xenogenic tissue, which was shown to be significant using co-cultures of cortical cells. The transplantation study showed that xenograft-derived fibres had a greater capacity for extensive fibre projection compared with those originating from allografts.

CONCLUSION

Results from the present study provide evidence for the hypothesis that xenografts are less responsive to inhibitory molecules present in the adult host environment and as such can project over great distances. Thus neural xenotransplantation may have the potential for more complete circuit reconstruction within the damaged host brain than equivalent allografted tissue.

The neuroprotective efficacy of alpha-crystallin against acute inflammation in mice

Acute inflammation activates macrophages or monocytes and subsequently releases several inflammatory cytokines and reactive oxygen and nitrogen species. These proinflammatory cytokines activate astrocytes and trigger neurodegenerative diseases. In this work, we chose to address the mechanistic aspects of alpha-crystallin's protective function in inflammation-triggered neurotoxicity in mice. Alpha-crystallin, a lens structural protein, comprising alpha-A and alpha-B subunits is an ubiquitous molecular chaperone, which have been shown to reduce reactive oxygen species (ROS) production and enhance cellular glutathione level in the acute inflammation-induced mice. Results show that the proinflammatory cytokines such as interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) were significantly high (P<0.05) in the plasma, liver, cortex and hippocampus of inflammation-induced mice when compared to control. Alpha-crystallin pretreatment prevents inflammation-induced cytokines and NO production. In addition, a significant (P<0.05) reduction of dopamine (DA), 5-hydroxytryptamine (5-HT) and norepinephrine (NE) was also observed in the inflammation-induced mice. Nevertheless, their metabolites, such as 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindole acetic acid (5-HIAA) increased significantly (P<0.05) as compared to control. The results indicate that alpha-crystallin pretreatment controls the inflammation-induced DA, 5-HT and NE catabolism and suggest that alpha-crystallin has the potential to act as an anti-inflammatory agent in the neuroprotective processes.

[From bench to bedside: should we believe in the efficacy of stem cells in cerebral ischaemia?]

Stroke is the third cause of mortality and the leading cause of morbidity in industrialized countries. At the present time, ischaemic stroke is treated at the acute phase by thrombolysis with a recombinant of the tissular-plasminogen activator, which must be administered within the first 3 hours. Cell therapy, while using the self-renewal and differentiation potentials of stem cells, brings new hope for the long-term care of ischaemic stroke. Animal studies show that stem cells improve functional deficit without reduction of infarct volume and with very rare differentiation of the stem cell. These experimental studies suggest that stem cells would support cerebral plasticity via growth factor production and stimulation of endogenous mechanisms of local repair. Assessment of effectiveness and safety in the use of stem cells in cerebral ischaemia still require thorough investigation before clinical trials in humans can be developed.

Immune problems in central nervous system cell therapy

Transplantation of cells and tissues to the mammalian brain and CNS has revived the interest in the immunological status of brain and its response to grafted tissue. The previously held view that the brain was an absolute "immunologically privileged site" allowing indefinite survival without rejection of grafts of cells has proven to be wrong. Thus, the brain should be regarded as a site where immune responses can occur, albeit in a modified form, and under certain circumstances these are as vigorous as those seen in other peripheral sites. Clinical cell transplant trials have now been performed in Parkinson's disease, Huntington's disease, demyelinating diseases, retinal disorders, stroke, epilepsy, and even deafness, and normally are designed as cell replacement strategies, although implantation of genetically modified cells for supplementation of growth factors has also been tried. In addition, some disorders of the CNS for which cell therapies are being considered have an immunological basis, such as multiple sclerosis, which further complicates the situation. Embryonic neural tissue allografted into the CNS of animals and patients with neurodegenerative conditions survives, makes and receives synapses, and ameliorates behavioral deficits. The use of aborted human tissue is logistically and ethically complicated, which has lead to the search for alternative sources of cells, including xenogeneic tissue, genetically modified cells, and stem cells, all of which can and will induce some level of immune reaction. We review some of the immunological factors involved in transplantation of cells to CNS.