Interplay between human microglia and neural stem/progenitor cells in an allogeneic co-culture model.

Experimental neural cell therapies, including donor neural stem/progenitor cells (NPCs) have been reported to offer beneficial effects on the recovery after an injury and to counteract inflammatory and degenerative processes in the central nervous system (CNS). The interplay between donor neural cells and the host CNS still to a large degree remains unclear, in particular in human allogeneic conditions. Here, we focused our studies on the interaction of human NPCs and microglia utilizing a co-culture model. In co-cultures, both NPCs and microglia showed increased survival and proliferation compared with mono-cultures. In the presence of microglia, a larger subpopulation of NPCs expressed the progenitor cell marker nestin, whereas a smaller group of NPCs expressed the neural markers polysialylated neural cell adhesion molecule, A2B5 and glial fibrillary acidic protein compared with NPC mono-cultures. Microglia thus hindered differentiation of NPCs. The presence of human NPCs increased microglial phagocytosis of latex beads. Furthermore, we observed that the expression of CD200 molecules on NPCs and the CD200 receptor protein on microglia was enhanced in co-cultures, whereas the release of transforming growth factor-ß was increased suggesting anti-inflammatory features of the co-cultures. To conclude, the interplay between human allogeneic NPCs and microglia, significantly affected their respective proliferation and phenotype. Neural cell therapy including human donor NPCs may in addition to offering cell replacement, modulate host microglial phenotypes and functions to benefit neuroprotection and repair.

Neuroprotective effects of human mesenchymal stem cells on neural cultures exposed to 6-hydroxydopamine: implications for reparative therapy in Parkinson's disease.

Stem cell (SC) transplantation represents a promising tool to treat neurodegenerative disorders, such as Parkinson's disease (PD), but positive therapeutic outcomes require elucidation of the biological mechanisms involved. Therefore, we investigated human Mesenchymal SCs (hMSCs) ability to protect murine differentiated Neural SCs (mdNSCs) against the cytotoxic effects of 6-hydroxydopamine (6-OHDA) in a co-culture model mimicking the in vivo neurovascular niche. The internalization of 6-OHDA mainly relies on its uptake by the dopamine active transporter (DAT), but its toxicity could also involve other pathways. We demonstrated that mdNSCs consistently expressed DAT along the differentiative process. Exposure to 6-OHDA did not affect hMSCs, but induced DAT-independent apoptosis in mdNSCs with generation of reactive oxygen species and caspases 3/7 activation. The potential neuroprotective action of hMSCs on mdNSCs exposed to 6-OHDA was tested in different co-culture conditions, in which hMSCs were added to mdNSCs prior to, simultaneously, or after 6-OHDA treatment. In the presence of the neurotoxin, the majority of mdNSCs acquired an apoptotic phenotype, while co-cultures with hMSCs significantly increased their survival (up to 70%) in all conditions. Multiplex human angiogenic array analysis on the conditioned media demonstrated that cytokine release by hMSCs was finely modulated. Moreover, sole growth factor addition yielded a similar neuroprotective effect on mdNSCs. In conclusion, our findings demonstrate that hMSCs protect mdNSCs against 6-OHDA neurotoxicity, and rescue cells from ongoing neurodegeneration likely through the release of multiple cytokines. Our findings provide novel insights for the development of therapeutic strategies designed to counteract the neurodegenerative processes of PD.

Correction to: Human ex vivo spinal cord slice culture as a useful model of neural development, lesion, and allogeneic neural cell therapy.

An amendment to this paper has been published and can be accessed via the original article.

Human ex vivo spinal cord slice culture as a useful model of neural development, lesion, and allogeneic neural cell therapy.

BACKGROUND: There are multiple promising treatment strategies for central nervous system trauma and disease. However, to develop clinically potent and safe treatments, models of human-specific conditions are needed to complement in vitro and in vivo animal model-based studies. METHODS: We established human brain stem and spinal cord (cross- and longitudinal sections) organotypic cultures (hOCs) from first trimester tissues after informed consent by donor and ethical approval by the Regional Human Ethics Committee, Stockholm (lately referred to as Swedish Ethical Review Authority), and The National Board of Health and Welfare, Sweden. We evaluated the stability of hOCs with a semi-quantitative hOC score, immunohistochemistry, flow cytometry, Ca2+ signaling, and electrophysiological analysis. We also applied experimental allogeneic human neural cell therapy after injury in the ex vivo spinal cord slices. RESULTS: The spinal cord hOCs presented relatively stable features during 7-21 days in vitro (DIV) (except a slightly increased cell proliferation and activated glial response). After contusion injury performed at 7 DIV, a significant reduction of the hOC score, increase of the activated caspase-3+ cell population, and activated microglial populations at 14 days postinjury compared to sham controls were observed. Such elevation in the activated caspase-3+ population and activated microglial population was not observed after allogeneic human neural cell therapy. CONCLUSIONS: We conclude that human spinal cord slice cultures have potential for future structural and functional studies of human spinal cord development, injury, and treatment strategies.

Induction of neurotrophin expression via human adult mesenchymal stem cells: implication for cell therapy in neurodegenerative diseases.

In animal models of neurological disorders for cerebral ischemia, Parkinson's disease, and spinal cord lesions, transplantation of mesenchymal stem cells (MSCs) has been reported to improve functional outcome. Three mechanisms have been suggested for the effects of the MSCs: transdifferentiation of the grafted cells with replacement of degenerating neural cells, cell fusion, and neuroprotection of the dying cells. Here we demonstrate that a restricted number of cells with differentiated astroglial features can be obtained from human adult MSCs (hMSCs) both in vitro using different induction protocols and in vivo after transplantation into the developing mouse brain. We then examined the in vitro differentiation capacity of the hMSCs in coculture with slices of neonatal brain cortex. In this condition the hMSCs did not show any neuronal transdifferentiation but expressed neurotrophin low-affinity (NGFR(p75)) and high-affinity (trkC) receptors and released nerve growth factor (NGF) and neurotrophin-3 (NT-3). The same neurotrophin's expression was demonstrated 45 days after the intracerebral transplantation of hMSCs into nude mice with surviving astroglial cells. These data further confirm the limited capability of adult hMSC to differentiate into neurons whereas they differentiated in astroglial cells. Moreover, the secretion of neurotrophic factors combined with activation of the specific receptors of transplanted hMSCs demonstrated an alternative mechanism for neuroprotection of degenerating neurons. hMSCs are further defined in their transplantation potential for treating neurological disorders.

Molecular and phenotypic characterization of human amniotic fluid cells and their differentiation potential.

The main goal of the study was to identify a novel source of human multipotent cells, overcoming ethical issues involved in embryonic stem cell research and the limited availability of most adult stem cells. Amniotic fluid cells (AFCs) are routinely obtained for prenatal diagnosis and can be expanded in vitro; nevertheless current knowledge about their origin and properties is limited. Twenty samples of AFCs were exposed in culture to adipogenic, osteogenic, neurogenic and myogenic media. Differentiation was evaluated using immunocytochemistry, RT-PCR and Western blotting. Before treatments, AFCs showed heterogeneous morphologies. They were negative for MyoD, Myf-5, MRF4, Myogenin and Desmin but positive for osteocalcin, PPARgamma2, GAP43, NSE, Nestin, MAP2, GFAP and beta tubulin III by RT-PCR. The cells expressed Oct-4, Rex-1 and Runx-1, which characterize the undifferentiated stem cell state. By immunocytochemistry they expressed neural-glial proteins, mesenchymal and epithelial markers. After culture, AFCs differentiated into adipocytes and osteoblasts when the predominant cellular component was fibroblastic. Early and late neuronal antigens were still present after 2 week culture in neural specific media even if no neuronal morphologies were detectable. Our results provide evidence that human amniotic fluid contains progenitor cells with multi-lineage potential showing stem and tissue-specific gene/protein presence for several lineages.

Mild to moderate reduction of a von Willebrand factor cleaving protease (ADAMTS-13) in pregnant women with HELLP microangiopathic syndrome.

BACKGROUND AND OBJECTIVES: Among the array of microangiopathies that may occur during pregnancy, HELLP syndrome and thrombotic thrombocytopenic purpura (TTP) produce similar laboratory findings (hemolytic anemia and thrombocytopenia), although neurological symptoms prevail in TTP and abnormal liver function in HELLP syndrome. It is clinically important to distinguish the two entities given that their managements differ (prompt induction of delivery in HELLP syndrome, plasma exchange in TTP). The purpose of this study was to evaluate whether or not ADAMTS-13, the metalloprotease that disposes ultralarge, highly thrombogenic multimers of von Willebrand factor (VWF) and is severely deficient or undetectable in many patients with TTP, is deficient in HELLP syndrome. DESIGN AND METHODS: We measured ADAMTS-13 and VWF (antigen, ristocetin cofactor activity, collagen binding, multimeric structure) in 17 pregnant women during HELLP syndrome and after 6 months during clinical remission. Controls were 25 healthy pregnant women and 50 healthy non-pregnant women. RESULTS: All the women with HELLP syndrome had lower plasma levels of ADAMTS-13 activity (median and range: 31%, 12-43) than did the healthy pregnant (71%, 48-105) and non-pregnant women (101%, 45-152); the reduced levels returned to normal on remission (115%, 90-170). Reduced levels were not due to the presence of inactivating autoantibodies and in no case was the protease undetectable in plasma. Ultralarge VWF multimers were not present in plasma, the levels of VWF were higher than in normal pregnancy. INTERPRETATION AND CONCLUSIONS: Because none of the pregnant women diagnosed with HELLP syndrome had undetectable ADAMTS-13 levels in pregnancy-associated thrombotic microangiopathies, the finding of severe ADAMTS-13 deficiency would argue against a diagnosis of HELLP syndrome and for a diagnosis of TTP.

Neuroprotective effects of human spinal cord-derived neural precursor cells after transplantation to the injured spinal cord.

To validate human neural precursor cells (NPCs) as potential donor cells for transplantation therapy after spinal cord injury (SCI), we investigated the effect of NPCs, transplanted as neurospheres, in two different rat SCI models. Human spinal cord-derived NPCs (SC-NPCs) transplanted 9 days after spinal contusion injury enhanced hindlimb recovery, assessed by the BBB locomotor test. In spinal compression injuries, SC-NPCs transplanted immediately or after 1 week, but not 7 weeks after injury, significantly improved hindlimb recovery compared to controls. We could not detect signs of mechanical allodynia in transplanted rats. Four months after transplantation, we found more human cells in the host spinal cord than were transplanted, irrespective of the time of transplantation. There was no focal tumor growth. In all groups the vast majority of NPCs differentiated into astrocytes. Importantly, the number of surviving rat spinal cord neurons was highest in groups transplanted acutely and subacutely, which also showed the best hindlimb function. This suggests that transplanted SC-NPCs improve the functional outcome by a neuroprotective effect. We conclude that SC-NPCs reliably enhance the functional outcome after SCI if transplanted acutely or subacutely, without causing allodynia. This therapeutic effect is mainly the consequence of a neuroprotective effect of the SC-NPCs.

Human neural stem/progenitor cells derived from embryonic stem cells and fetal nervous system present differences in immunogenicity and immunomodulatory potentials in vitro.

To develop cell therapies for damaged nervous tissue with human neural stem/progenitor cells (hNPCs), the risk of an immune response and graft rejection must be considered. There are conflicting results and lack of knowledge concerning the immunocompetence of hNPCs of different origin. Here, we studied the immunogenicity and immunomodulatory potentials of hNPCs cultured under equivalent conditions after derivation from human embryonic stem cells (hESC-NPCs) or human fetal spinal cord tissue (hfNPCs). The expression patterns of human leukocyte antigen, co-stimulatory and adhesion molecules in hESC-NPCs and hfNPCs were relatively similar and mostly not affected by inflammatory cytokines. Unstimulated hfNPCs secreted more transforming growth factor-ß1 (TGF-ß1) and ß2 but similar level of interleukin (IL)-10 compared to hESC-NPCs. In contrast to hfNPCs, hESC-NPCs displayed 4-6 fold increases in TGF-ß1, TGF-ß2 and IL-10 under inflammatory conditions. Both hNPCs reduced the alloreaction between allogeneic peripheral blood mononuclear cells (PBMCs) and up-regulated CD4(+)CD25(+)forkhead box P3 (FOXP3)(+) T cells. However, hESC-NPCs but not hfNPCs dose-dependently triggered PBMC proliferation, which at least partly may be due to TGF-ß signaling. To conclude, hESC-NPCs and hfNPCs displayed similarities but also significant differences in their immunocompetence and interaction with allogeneic PBMCs, differences may be crucial for the outcome of cell therapy.

Amniotic fluid stem cells increase embryo survival following injury.

Although amniotic fluid cells can differentiate into several mesenchymal lineages and have been proposed as a valuable therapeutic cell source, their ability to undergo terminal neuronal differentiation remains a cause of controversy. The aim of this study was to investigate the neuronal differentiation ability of the c-Kit-positive population from GFP-transgenic rat amniotic fluid, amniotic fluid stem (AFS) cells, and to assess how they affected injury response in avian embryos. AFS cells were found to express several neural stem/progenitor cell markers. However, no overt neuronal differentiation was apparent after either treatment with small molecules known to stimulate neuronal differentiation, attempts to differentiate AFS cell-derived embryoid body-like structures, or grafting AFS cells into environments known to support neuronal differentiation (organotypic rat hippocampal cultures, embryonic chick nervous system). Nonetheless, AFS cells significantly reduced hemorrhage and increased survival when grafted at the site of an extensive thoracic crush injury in E2.5 chick embryos. Increased embryo survival was induced neither by desmopressin treatment, which also reduced hemorrhage, nor by grafting other mesenchymal or neural cells, indicating a specific effect of AFS cells. This was found to be mediated by soluble factors in a transwell coculture model. Altogether, this study shows that AFS cells reduce tissue damage and increase survival in injured embryos, providing a potentially valuable tool as therapeutic agents for tissue repair, particularly prenatal/perinatal repair of defects diagnosed during gestation, but this effect is mediated via paracrine mechanisms rather than the ability of AFS cells to fully differentiate into neuronal cells.

Metalloproteinase alterations in the bone marrow of ALS patients.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, nowadays considered as suitable candidate for autologous stem therapy with bone marrow (BM). A careful characterization of BM stem cell (SC) compartment is mandatory before its extensive application to clinic. Indeed, widespread systemic involvement has been recently advocated given that non-neuronal neighboring cells actively influence the pathological neuronal loss. We therefore investigated BM samples from 21 ALS patients and reported normal hematopoietic biological properties while an atypical behavior and impaired SC capabilities affected only the mesenchymal compartment. Moreover, by quantitative real-time approach, we observed altered Collagen IV and Metalloproteinase-9 levels in patients' derived mesenchymal stem cells (MSCs). Widespread metalloproteinase (MMPs) and their tissue inhibitor (TIMPs) alterations were established by multiplex ELISA analysis, demonstrating diffuse enzymatic variations in MSC compartment. Since MMPs act as fundamental effectors of extra-cellular matrix remodeling and stem cell mobilization, their modifications in ALS may influence reparative mechanisms effective in counteracting the pathology. In conclusion, ALS is further confirmed to be a systemic disease, not restricted to the nervous system, but affecting also the BM stromal compartment, even in sporadic cases. Therefore, therapeutic implantation of autologous BM derived SC in ALS patients needs to be carefully reevaluated.

Multiple neurogenic and neurorescue effects of human mesenchymal stem cell after transplantation in an experimental model of Parkinson's disease.

Stimulation of endogenous repair in neurodegenerative diseases, such as Parkinson's disease (PD), appears to be a novel and promising therapeutic application of stem cells (SCs). In fact SCs could propel local microenvironmental signals to sustain active endeavors for damaged neurons substitution, normally failing in non-supportive pathological surroundings. In this study, we demonstrated that two different doses of naïve human adult mesenchymal stem cells (hMSCs), implanted in the striatum of rats lesioned with 6-hydroxydopamine (6-OHDA), positively survived 23 days after transplantation. Their fate was directly influenced by the surrounding host environment while grafted hMSCs, dose dependently, regionally sustained the survival of striatal/nigral dopaminergic terminals and enhanced neurogenesis in the Subventricular Zone (SVZ). The number of proliferative cells (Ki67/Proliferating Cell Nuclear Antigen +) as well as neuroblasts migration significantly augmented in the lesioned striatum of transplanted animals compared to controls. No SVZ astrogenesis was detected in all experimental conditions, irrespectively of graft presence. Activation of endogenous stem cell compartments and rescue of dopaminergic neurons, supported by the persistent release of specific cytokine by MSCs in vivo, appeared in principle able to contrast the neurodegenerative processes induced by the 6-OHDA lesion. Our results suggest that reciprocal influences between grafted cells and endogenous neural precursors could be important for the observed neurorescue effect on several brain regions. Altogether, our data provide remarkable cues regarding the potential of hMSCs in promoting endogenous reparative mechanisms that may prove applicable and beneficial for PD treatment.

Transplantation of undifferentiated human mesenchymal stem cells protects against 6-hydroxydopamine neurotoxicity in the rat.

Stem cells have been increasingly recognized as a potential tool to replace or support cells damaged by the neurodegenerative process that underlies Parkinson's disease (PD). In this frame, human adult mesenchymal stem cells (hMSCs) have been proposed as an attractive alternative to heterologous embryonic or neural precursor cells. To address this issue, in this study we implanted undifferentiated hMSCs into the striatum of rats bearing a lesion of the nigrostriatal pathway induced by local injection of 6-hydroxydopamine (6-OHDA), a widely recognized rodent model of PD. Before grafting, cultured hMSCs expressed markers of both undifferentiated and committed neural cells, including nestin, GAP-43, NSE, beta-tubulin III, and MAP-2, as well as several cytokine mRNAs. No glial or specific neuronal markers were detected. Following transplantation, some hMSCs acquired a glial-like phenotype, as shown by immunoreactivity for glial fibrillary acid protein (GFAP), but only in animals bearing the nigrostriatal lesion. More importantly, rats that received the striatal graft showed increased survival of both cell bodies and terminals of dopaminergic, nigrostriatal neurons, coupled with a reduction of the behavioral abnormalities (apomorphine-induced turning behavior) associated with the lesion. No differentiation of the MSCs toward a neuronal (dopaminergic) phenotype was observed in vivo. In conclusion, our results suggest that grafted hMSCs exert neuroprotective effects against nigrostriatal degeneration induced by 6-OHDA. The mechanisms underlying this effect remain to be clarified, although it is likely that the acquisition of a glial phenotype by grafted hMSCs may lead to the release of prosurvival cytokines within the lesioned striatum.

A role for the ELAV RNA-binding proteins in neural stem cells: stabilization of Msi1 mRNA.

Post-transcriptional regulation exerted by neural-specific RNA-binding proteins plays a pivotal role in the development and maintenance of the nervous system. Neural ELAV proteins are key inducers of neuronal differentiation through the stabilization and/or translational enhancement of target transcripts bearing the AU-rich elements (AREs), whereas Musashi-1 maintains the stem cell proliferation state by acting as a translational repressor. Since the gene encoding Musashi-1 (Msi1) contains a conserved ARE in its 3' untranslated region, we focused on the possibility of a mechanistic relationship between ELAV proteins and Musashi-1 in cell fate commitment. Colocalization of neural ELAV proteins with Musashi-1 clearly shows that ELAV proteins are expressed at early stages of neural commitment, whereas interaction studies demonstrate that neural ELAV proteins exert an ARE-dependent binding activity on the Msi1 mRNA. This binding activity has functional effects, since the ELAV protein family member HuD is able to stabilize the Msi1 ARE-containing mRNA in a sequence-dependent way in a deadenylation/degradation assay. Furthermore activation of the neural ELAV proteins by phorbol esters in human SH-SY5Y cells is associated with an increase of Musashi-1 protein content in the cytoskeleton. We propose that ELAV RNA-binding proteins exert an important post-transcriptional control on Musashi-1 expression in the transition from proliferation to neural differentiation of stem/progenitor cells.