Genome-wide expression profiling and functional network analysis upon neuroectodermal conversion of human mesenchymal stem cells suggest HIF-1 and miR-124a as important regulators.

Tissue-specific stem cells, such as bone-marrow-derived human mesenchymal stem cells (hMSCs), are thought to be lineage restricted and therefore, could only be differentiated into cell types of the tissue of origin. Several recent studies however have suggested that these types of stem cells might be able to break barriers of germ layer commitment and differentiate in vitro into cells with neuroectodermal properties. We reported earlier about efficient conversion of adult hMSCs into a neural stem cell (NSC)-like population (hmNSCs, for human marrow-derived NSC-like cells) with all major properties of NSCs including functional neuronal differentiation capacity. Here we compared the transcriptomes from hMSCs and hmNSCs using a novel strategy by combining classic Affymetrix oligonucleotide microarray profiling with regulatory and protein interaction network analyses to shed light on regulatory protein networks involved in this neuroectodermal conversion process. We found differential regulation of extracellular matrix protein transcripts, up-regulation of distinct neuroectodermal and NSCs marker genes and local chromosomal transcriptional up-regulation at chromosome 4q13.3. In comparison to hMSCs and primary adult hippocampal NSCs, the transcriptome of hmNSCs displayed minor overlap with both other cell populations. Advanced bioinformatics of regulated genes upon neuroectodermal conversion identified transcription factor networks with HIF-1 and microRNA miR-124a as potential major regulators. Together, transgerminal neuroectodermal conversion of hMSCs into NSC-like cells is accompanied by extensive changes of their global gene expression profile, which might be controlled in part by transcription factor networks related to HIF-1 and miR-124a.

Neuroectodermally converted human mesenchymal stromal cells provide cytoprotective effects on neural stem cells and inhibit their glial differentiation.

BACKGROUND AIMS: In recent years, bone marrow (BM)-derived mesenchymal stromal cells (MSC) have become a promising source for neuroregenerative therapies. We evaluated the trophic effects of neuroectodermally converted MSC (mNSC) on neural stem cells (NSC). METHODS: We quantified the expression of growth factors by mNSC using real-time reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) and studied the effects of mNSC conditioned medium and mNSC (in direct co-culture) on NSC proliferation, differentiation and survival. RESULTS: Neuroectodermal conversion of human MSC induced high expression of growth factors at both mRNA and protein levels, most prominently hepatocyte growth factor, vascular endothelial growth factor and amphiregulin (37 +/- 17, 92 +/- 44 and 12 +/- 11 ng/10(5) cells, respectively), which remained at high levels upon co-culturing with neural cells. Accordingly, mNSC conditioned medium and co-cultivation with mNSC reduced cell death of NSC (36% of control), stimulated their proliferation, attenuated glial differentiation of NSC (7 +/- 3 versus 59 +/- 6%; P < 0.01) and protected NSC against the neurotoxin 6-hydroxydopamine (with half-maximally concentrations EC(50) values of 217 +/- 207 microM in the presence of mNSC compared with 62 +/- 49 microM for NSC alone). CONCLUSIONS: mNSC promote survival and proliferation, and inhibit glial differentiation, of NSC. Protection of NSC by mNSC against 6-hydroxy-dopamine is probably mediated by the release of cytotrophic factors. Our results promote neuroectodermally converted MSC as promising candidate cells for the development of neuroregenerative and neuroprotective therapies.

Age-dependent neuroectodermal differentiation capacity of human mesenchymal stromal cells: limitations for autologous cell replacement strategies.

BACKGROUND AIMS: Human adult bone marrow (BM)-derived mesenchymal stromal cells (hMSC) are reported to break germ layer commitment and differentiate into cells expressing neuroectodermal properties. Although it is of pivotal interest for cell replacement therapies for neurologic disorders, no data exist on the influence of the donor's age on this multipotent differentiation behavior. METHODS: We evaluated various epigenetic neuroectodermal conversion protocols in adult hMSC derived from older donors (>45 versus 18-35 years of age) using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and immunocytochemistry. The protocols included single- and multi-step conversion-differentiation protocols combined with co-culture techniques. Furthermore, the age dependency of mesodermal differentiation potential and cell senescence were investigated. RESULTS: The neuroectodermal differentiation potential of hMSC derived from old donors was completely lost, with no cells showing mature neuroectodermal phenotypes using single- and multi-step conversion-differentiation protocols and no improvement of neurogenesis by various co-culture conditions. Comparison of young versus old donor-derived hMSC showed fewer cells expressing early neuroectodermal marker proteins in the latter samples. qRT-PCR showed reduced expression of the proliferation marker KI67 and the neuroectodermal gene NES (nestin) in old donor-derived cells compared with young donor hMSC. Telomere length analysis showed no general cell aging. CONCLUSIONS: Our data provide evidence that only young donor-derived hMSC can be epigenetically differentiated in vitro into neuroectodermal cells, pointing towards senescence of multipotentiality of old donor-derived hMSC. There is thus an urgent need to develop better protocols for successful neuroectodermal differentiation of hMSC from old individuals as a prerequisite for autologous cell replacement strategies for neurologic diseases in elderly patients.

Neurotransplantation in mice: the concorde-like position ensures minimal cell leakage and widespread distribution of cells transplanted into the cisterna magna.

The access of transplanted cells to large areas of the CNS is of critical value for cell therapy of chronic diseases associated with widespread neurodegeneration. Intrathecal cell application can match this requirement. Here we describe an efficient method for cell injection into the cisterna magna and the assessment of the cell distribution within subarachnoidal space in mice. In order to maximize cell distribution we applied a "concord-like" position, where the cisterna magna is nearly the highest point of the animal's body. A drop of saline on the needle insertion site avoided the outflow of transplanted cells from subarachnoidal space with CSF during surgery. Twenty-four hours later the preparation of the CNS with an intact dura mater by a suitable dissection technique (described in detail) revealed approx. 80% of the injected cells (100,000 cells per animal) within the subarachnoidal space ranging from the skull base (olfactory nerve to premedullary cisterns) to the IV ventricle, and to both the ventral and dorsal surfaces of the spinal cord. Thus the "concorde-like" position proved to be very useful for intrathecal cell application leading to a widespread cell distribution within the subarachnoidal space.

Efficient processing of Alzheimer's disease amyloid-Beta peptides by neuroectodermally converted mesenchymal stem cells.

Most disease-modifying therapeutic approaches in Alzheimer's disease (AD) aim to reduce the accumulation of neurotoxic amyloid-beta (Abeta) peptides as a hallmark of AD pathogenesis. Here we report the in vitro basis for a potential autologous stem cell-based strategy for widespread delivery of enzymatic activities against Abeta formation in the brain. We detected the functional induction of two genes upon neuroectodermal conversion of human adult mesenchymal stem cells (MSCs), namely F-spondin and neprilysin (CD10), with a 4,992 + or - 697-fold and 692 + or - 226-fold increase of mRNA levels in converted cells compared to MSCs, respectively (n = 3; P < 0.01). These genes are known to be involved in the formation and degradation of Abeta peptides, respectively. Consistently, coincubation of the neuroectodermally converted MSCs with HEK-293 cells stably expressing amyloid precursor protein (APP) lead to a significant cell dose-dependent decrease of Abeta peptides. These in vitro results indicate that MSCs might be useful vehicles for delivering anti-Abeta activity depicting a causal stem cell-based therapeutic approach to treat AD.

Limited effects of glatiramer acetate in the high-copy number hSOD1-G93A mouse model of ALS.

In amyotrophic lateral sclerosis (ALS), an involvement of the immune system in the degenerative processes has been shown in both humans and the transgenic SOD1-G93A mice. We previously showed that Glatiramer acetate (also known as copolymer-1; COP-1; Copaxone) improves motor function and extends survival times in an inbred strain of ALS mice probably by interacting with pro-inflammatory T(H) lymphocytes. In the course of this study we tested whether these beneficial effects could be reproduced by repeated vaccination of animals with COP-1 without co-administration of complete Freund's adjuvant. In an outbred strain we could not demonstrate a positive effect of COP-1 on survival times, but found a significant improvement of motor performance during the late stage of disease and a moderate decrease of the production of the inflammatory cytokines interferon-gamma and IL-4 by T lymphocytes isolated from the mice's spleen. In conclusion, the effects of COP-1 in the applied hybrid strain displaying a faster disease progression were less pronounced than in the earlier tested inbred strain of ALS mice.

Transcription profiling of adult and fetal human neuroprogenitors identifies divergent paths to maintain the neuroprogenitor cell state.

Global gene expression profiling was performed using RNA from adult human hippocampus-derived neuroprogenitor cells (NPCs) and multipotent frontal cortical fetal NPCs compared with adult human mesenchymal stem cells (hMSCs) as a multipotent adult stem cell control, and adult human hippocampal tissue, to define a gene expression pattern that is specific for human NPCs. The results were compared with data from various databases. Hierarchical cluster analysis of all neuroectodermal cell/tissue types revealed a strong relationship of adult hippocampal NPCs with various white matter tissues, whereas fetal NPCs strongly correlate with fetal brain tissue. However, adult and fetal NPCs share the expression of a variety of genes known to be related to signal transduction, cell metabolism and neuroectodermal tissue. In contrast, adult NPCs and hMSCs overlap in the expression of genes mainly involved in extracellular matrix biology. We present for the first time a detailed transcriptome analysis of human adult NPCs suggesting a relationship between hippocampal NPCs and white matter-derived precursor cells. We further provide a framework for standardized comparative gene expression analysis of human brain-derived NPCs with other stem cell populations or differentiated tissues. Disclosure of potential conflicts of interest is found at the end of this article.

Comparative analysis of neuroectodermal differentiation capacity of human bone marrow stromal cells using various conversion protocols.

Human adult bone marrow-derived mesodermal stromal cells (hMSCs) are able to differentiate into multiple mesodermal tissues, including bone and cartilage. There is evidence that these cells are able to break germ layer commitment and differentiate into cells expressing neuroectodermal properties. There is still debate about whether this results from cell fusion, aberrant marker gene expression or real neuroectodermal differentiation. Here we extend our work on neuroectodermal conversion of adult hMSCs in vitro by evaluating various epigenetic conversion protocols using quantitative RT-PCR and immunocytochemistry. Undifferentiated hMSCs expressed high levels of fibronectin as well as several neuroectodermal genes commonly used to characterize neural cell types, such as nestin, beta-tubulin III, and GFAP, suggesting that hMSCs retain the ability to differentiate into neuroectodermal cell types. Protocols using a direct differentiation of hMSCs into a neural phenotype failed to induce significant changes in morphology and/or expression of markers of early and mature glial/neuronal cells types. In contrast, a multistep protocol with conversion of hMSCs into a neural stem cell-like population and subsequent terminal differentiation in mature glia and neurons generated relevant morphological changes as well as significant increase of expression levels of marker genes for early and late neural cell types, such as nestin, neurogenin2, MBP, and MAP2ab, accompanied by a loss of their mesenchymal properties. Our data provide an impetus for differentiating hMSCs in vitro into mature neuroectodermal cells. Neuroectodermally converted hMSCs may therefore ultimately help in treating acute and chronic neurodegenerative diseases. Analysis of marker gene expression for characterization of neural cells derived from MSCs has to take into account that several early and late neuroectodermal genes are already expressed in undifferentiated MSCs.

Pharmacological interference with dimerization of human neuronal nitric-oxide synthase expressed in adenovirus-infected DLD-1 cells.

A recombinant adenovirus containing the cDNA of human neuronal nitric-oxide synthase (nNOS) was constructed to characterize the interaction of nNOS with N-[(1,3-benzodioxol-5-yl)methyl]-1-[2-(1H-imidazole-1-yl)pyrimidin-4-yl]-4-(methoxycarbonyl)-piperazine-2-acetamide (BBS-1), a potent inhibitor of inducible NOS dimerization [Proc Natl Acad Sci USA 97:1506-1511, 2000]. BBS-1 inhibited de novo expression of nNOS activity in virus-infected cells at a half-maximal concentration (IC(50)) of 40 +/- 10 nM in a reversible manner. Low-temperature gel electrophoresis showed that BBS-1 attenuated the formation of SDS-resistant nNOS dimers with an IC(50) of 22 +/- 5.2 nM. Enzyme inhibition progressively decreased with increasing time of addition after infection. BBS-1 did not significantly inhibit dimeric nNOS activity (IC(50) > 1 mM). Long-term incubation with BBS-1 of human embryonic kidney cells stably transfected with nNOS or endothelial NOS revealed a slow time- and concentration-dependent decrease of NOS activity with half-lives of 30 and 43 h and IC(50) values of 210 +/- 30 nM and 12 +/- 0.5 microM, respectively. These results establish that BBS-1 interferes with the assembly of active nNOS dimers during protein expression. Slow inactivation of constitutively expressed NOS in intact cells may reflect protein degradation and interference of BBS-1 with the de novo synthesis of functionally active NOS dimers. As time-dependent inhibitors of NOS dimerization, BBS-1 and related compounds provide a promising strategy to develop a new class of selective and clinically useful NOS inhibitors.