Sequential RARbeta and alpha signalling in vivo can induce adult forebrain neural progenitor cells to differentiate into neurons through Shh and FGF signalling pathways.

We show here the role of retinoic acid receptor (RAR) beta and alpha signalling in proliferation and differentiation of endogenous adult forebrain neural progenitor cells (NPCs). RARbeta activation stimulates Sonic hedgehog signalling (Shh), and induces the proliferation of the NPCs. They can be induced to become Doublecortin (DCX) expressing migrating neuroblasts by RARalpha signalling, some of which differentiate into cholinergic neurons. The same signalling pathways cause the proliferation of embryonic forebrain NPCs. These cells express glial fibrillary acidic protein (GFAP) and are predominantly uni/bipolar, two characteristics of neuronal progenitor cells. We further show that fibroblast growth factor (FGF) signalling, induces the expression of the retinoic acid degrading enzyme cytochrome P450 (cyp) 26a1, and that one of its products, 4-oxo-RA, mimics the action of the RARalpha agonist in the differentiation of the NPCs into cholinergic neurons.

Embryonic stem cells: protecting pluripotency from alloreactivity.

There can be little doubt that 2006 turned out to be the annus horribilis for therapeutic cloning by somatic nuclear transfer (SNT). As the full extent of the fraud surrounding the generation of patient-specific embryonic stem (ES) cell lines became apparent, hopes began to fade for the advent of cell replacement therapies (CRT), free from the confounding issues of immune rejection. While the dust begins to settle, it is perhaps pertinent to ask whether the promise of SNT is still worth pursuing or whether alternative strategies for immune evasion might help fill the void.

Characterization of human embryonic stem cell lines by the International Stem Cell Initiative.

The International Stem Cell Initiative characterized 59 human embryonic stem cell lines from 17 laboratories worldwide. Despite diverse genotypes and different techniques used for derivation and maintenance, all lines exhibited similar expression patterns for several markers of human embryonic stem cells. They expressed the glycolipid antigens SSEA3 and SSEA4, the keratan sulfate antigens TRA-1-60, TRA-1-81, GCTM2 and GCT343, and the protein antigens CD9, Thy1 (also known as CD90), tissue-nonspecific alkaline phosphatase and class 1 HLA, as well as the strongly developmentally regulated genes NANOG, POU5F1 (formerly known as OCT4), TDGF1, DNMT3B, GABRB3 and GDF3. Nevertheless, the lines were not identical: differences in expression of several lineage markers were evident, and several imprinted genes showed generally similar allele-specific expression patterns, but some gene-dependent variation was observed. Also, some female lines expressed readily detectable levels of XIST whereas others did not. No significant contamination of the lines with mycoplasma, bacteria or cytopathic viruses was detected.

Generation of hepatocytes from human embryonic stem cells.

Use of human hepatocytes for therapeutic and drug discovery applications is hampered by limited tissue source and the inability of hepatocytes to proliferate and maintain function long-term in vitro. Human embryonic stem (hES) cells are immortal and pluripotent and may provide a cell source for functional human hepatocytes (1) Here we have outlined some of the protocols currently in use for the generation of hepatocytes from hES cells.

Isolation, in vitro cultivation and characterisation of foetal liver cells.

Hepatocyte transplantation has recently become an efficient clinical method in the treatment of patients with metabolic liver diseases. The shortage of donor cells remains an obstacle to treat more patients. Foetal liver tissues may therefore be useful as an alternative source of generating functional hepatocytes after in vitro culture and maturation.

Homogeneous monocytes and macrophages from human embryonic stem cells following coculture-free differentiation in M-CSF and IL-3.

OBJECTIVE: To develop a simple and efficient method for producing homogeneous populations of monocytes and macrophages from human embryonic stem cells (hES). MATERIALS AND METHODS: Human embryonic stem cell lines KCL001, KCL002, and HUES-2 were differentiated into monocytes by coculture-free differentiation with two growth factors using a three-step method. The method involved embryoid body (EB) formation in hES media, directed differentiation with macrophage colony-stimulating factor and interleukin (IL)-3, and harvest of nonadherent monocytes from the culture supernatants. hES monocytes (esMCs) were analyzed by microscopy, flow cytometry, transcriptome analysis, and tested for the ability to differentiate into macrophages. hES monocyte-derived macrophages (esMDM) were analyzed for phagocytosis and endocytosis by microscopy and flow cytometry, cytokine secretion by multiplex cytokine assay, and for interferon (IFN)-gamma and IL-4 activation by flow cytometry. RESULTS: Homogeneous esMCs (>90% CD14-positive) that did not require any additional purification steps were produced after 18.7 +/- 7.7 days (mean +/- SD, n = 19). Production continued for several months when growth factors were replaced, with a total yield of 3.4 x 10(5) +/- 2.0 esMCs (mean +/- SD, n = 9) per EB. Transcriptome analysis of the esMC and the esMDM revealed a distinct myeloid signature that correlated with primary adult blood-derived monocytes and spleen tissue samples but not with other tissue samples tested. We found that esMCs and esMDMs expressed well-defined markers of the mononuclear phagocyte system including PU-1, C/EBPalpha, EMR1, and EMR2, MPEG1, CD1c, CD4, CD18, CD32, CD33, CD68, cathepsins and serine carboxypeptidase. Finally, esMCs differentiated into functional macrophages that could endocytose acetylated low-density lipoprotein, phagocytose opsonized yeast particles, secrete specific cytokines in response to lipopolysaccharide, and be activated differentially with IFN-gamma and IL-4. CONCLUSIONS: We have developed a simple and efficient method for producing homogeneous populations of monocytes and macrophages from hES cells. esMCs have a myeloid signature and can differentiate into functional macrophages. The method should prove useful in answering experimental questions regarding monocyte and macrophage development and biology.

Regenerative medicine in Parkinson's disease: generation of mesencephalic dopaminergic cells from embryonic stem cells.

Cell replacement therapy has been proposed as a means of replacing specific populations of cells lost through trauma, disease or ageing. Parkinson's disease is a progressive neurodegenerative disorder caused by the loss of midbrain dopaminergic neurons. Intrastriatal transplants of human foetal mesencephalic tissue in Parkinson's patients have demonstrated clinical efficacy, but the limited availability of tissue precludes systematic use of this treatment. Human embryonic stem cells are capable of unlimited self-renewal and can differentiate into cells representative of all three germ layers, including cells of the central nervous system. These cells may thus provide a relatively unlimited source of cells for transplantation, if appropriate differentiation protocols to generate highly enriched and specific populations of neural cells can be developed.

Altered neurogenesis in Alzheimer's disease.

BACKGROUND: Exciting preliminary work indicates an increase in progenitor activity in the subgranular zone of the dentate gyrus of people with Alzheimer's disease (AD) compared to that of controls. We examine progenitor activity in the other main progenitor niche, the subventricular zone (SVZ), as well as potential associations with key pathological and neurochemical substrates. METHOD: Immunocytochemistry techniques utilizing nestin and Musashi1 antibodies were used to examine progenitor activity in the SVZ and to enable comparisons between seven patients with AD and seven controls, based upon the quantification of the percentage area covered, using the Image Pro Plus v.4.1 image analysis system. AD pathology was staged using the Consortium to Establish a Registry for Alzheimer's Disease and Braak criteria. Choline acetyl transferase (ChAT) was measured in the temporal cortex as an indication of the severity of cortical cholinergic deficits. Glial fibrillary acidic protein (GFAP) was used to label astrocytes. RESULTS: There was a significant ninefold decrease (Z = 2.2, P = .046) of Musashi1 immunoreactivity in the SVZ of patients with AD in comparison with that of controls, but there was a significant increase in nestin immunoreactivity in the same region (Z = 2.2, P = .028) without any significant change in GFAP immunoreactivity. Reduced ChAT enzymatic activity was the main association of Musashi immunoreactivity (R = -.90, P = .03). DISCUSSION: The current results indicate a significant reduction of progenitor cells (as labeled by Musashi1) in the SVZ of patients with AD, but an increase in GFAP-negative astrocyte-like cells with progenitor characteristics. Cortical cholinergic loss was strongly associated with the reduction of progenitors, with potential implications of important treatment targets.

Stage-specific changes in neurogenic and glial markers in Alzheimer's disease.

BACKGROUND: Reports of altered endogenous neurogenesis in people with Alzheimer's disease (AD) and transgenic AD models have suggested that endogenous neurogenesis may be an important treatment target, but there is considerable discrepancy among studies. We examined endogenous neurogenesis and glia changes across the range of pathologic severity of AD in people with and without dementia to address this key question. METHODS: Endogenous neurogenesis and glia in the subventricular zone and dentate gyrus neurogenic niches were evaluated using single and double immunohistochemistry and a validated antibody selection for stage-specific and type-specific markers in autopsy tissue from a representative cohort of 28 participants in the Medical Research Council Cognitive Function and Ageing Study. Immunopositive cells were measured blinded to diagnosis using bright-field and fluorescent microscopy. RESULTS: The number of newly generated neurons significantly declined only in the dentate gyrus of patients with severe tau pathology. No other changes in other neurogenic markers were observed in either of the neurogenic niches. Alterations in astrocytes and microglia were also observed in the dentate gyrus across the different stages of tau pathology. No change in any of the markers was observed in individuals who died with dementia compared with individuals who did not die with dementia. CONCLUSIONS: Alterations in endogenous neurogenesis appeared to be confined to a reduction in the generation of new neurons in the dentate gyrus of patients with AD and severe neurofibrillary tangle pathology and were accompanied by changes in the glia load. These data suggest that intervention enhancing endogenous neurogenesis may be a potential therapeutic target in AD.

Noradrenergic changes, aggressive behavior, and cognition in patients with dementia.

BACKGROUND: We wished to examine the integrity of the noradrenergic system in patients with Alzheimer's disease, mixed/other dementias and controls, and possible relationships between changes in the noradrenergic system and the presence of behavioral and psychiatric signs and symptoms in dementia. METHODS: Alpha(2) adrenoceptor sites were measured by radioligand binding in three cortical regions of 46 individuals with dementia and 33 elderly normal controls together with cortical noradrenaline concentration and locus coeruleus cell and neurofibrillary tangle counts. RESULTS: The alpha(2) adrenergic receptor density was unaltered in patients with Alzheimer's disease, mixed/other dementias compared with controls; however, there was a loss of locus coeruleus cells in subjects with dementia, reaching 50% within the rostral nucleus. In addition, a significant reduction was seen in the midtemporal cortical noradrenaline concentration (31% decrease) in patients with Alzheimer's disease. In subjects with dementia, there was a positive correlation between aggressive behavior and magnitude of rostral locus coeruleus cell loss, while the reduction in noradrenaline concentration correlated with cognitive impairment. CONCLUSIONS: Subgroups of patients with Alzheimer's disease may have different neurochemical changes from patients lacking these changes. Therefore, this study may have implications for the treatment of behavioral and psychiatric signs and symptoms in dementia, particularly aggressive behavior in patients with dementia.

Therapeutic potential of stem cells in central nervous system regeneration.

Neurodegenerative disorders and traumatic brain injury result in the loss of specific neuronal populations. Stem cells are self-renewing, multi- or pluripotent cells capable of differentiating into a wide range of cell types, properties which make stem cells a potentially invaluable source of transplantable cells. Recent experimental studies have indicated that several stem cell populations have the ability to replace lost neurons and to repair the damaged nervous system following transplantation. This review evaluates the potential of various stem cell populations in the treatment of human neurodegenerative conditions and traumatic brain injury.

Changes in hippocampal SNAP-25 expression following afferent lesions.

Reductions in SNAP-25 immunohistochemistry were found after removing the glutamatergic and cholinergic inputs to the rat hippocampus. SNAP-25 levels were normalised by 1 month after afferent lesions. Surprisingly, a superimposed cholinergic lesions did not affect the return to normal SNAP-25 levels after a long-term entorhinal cortex lesion. It is concluded that changes in SNAP-25 may represent early markers of synaptic loss following afferent lesions to the hippocampus.

Glutamate receptor antagonists modulate heat shock protein response in focal brain ischemia.

Neurons and glia reacting to ischemic injury exhibit delayed expression of heat shock proteins (HSPs). We tested the hypothesis that glutamate receptor antagonists alter neuronal and glial activation during focal cerebral ischemia, as shown by spatio-temporal changes in HSP immunoreactivity. Rats underwent focal ischemia by permanent occlusion of the middle cerebral artery. All animals were pre-treated with NBQX (30 mg kg-1), a competitive antagonist of the AMPA/kainate receptor, or CGS-19755 (10 mg kg-1), a competitive NMDA receptor antagonist, and euthanatized after 6 or 24 h of ischemia to demonstrate regional immunoreactivity of HSP-72 or 32 in brain. Neurons immunolabeled for HSP-72 appeared in the penumbral region adjacent to the infarct at 24 h and increased in number and distribution after pretreatment with NBQX or CGS-19755. Immunolabeling for HSP-32 revealed that pre-treatment with CGS-19755 caused ramified glia to infiltrate the ischemic cortex at 6 h, a pattern that was not seen in ischemic controls until 24 h. Blockade of the NMDA or AMPA/kainate receptor modulates cellular stress responses in both neurons and glia within the developing infarct. We conclude that early, rather than delayed, expression of HSP-32 is a sensitive indicator of glial activation induced specifically by CGS-19755.

Developing technologies to unlock the therapeutic and research potential of human stem cells.

Since human embryonic stem cells (hESCs) were first isolated and cultured nearly 15 years ago, stem cell biology has been a promising and fast-moving area of research. Improved clinical predictivity in drug development, use in assays to personalise medicine effectively and as the foundation for cell-based therapies are all areas where stem cells can play an important role. But with opportunities come challenges and it is vital that the field of stem cells continues to progress to achieve its potential. This article outlines the measures the Cell Technologies group at GE Healthcare Life Sciences are taking, along with its collaborators in academia, industry and the clinic, to advance stem cell tools and technologies, as well as identifying some future challenges for stem cell research, drug discovery, cell therapy and regenerative medicine.

Increased neural progenitors in vascular dementia.

Since groundbreaking studies demonstrated the presence of progenitor cells in the adult human brain, there have been intense interests in their potential therapeutic application, but to date only limited data has been obtained in man. An immunohistological study was performed in order to examine neurogenesis in both the subventricular and peri-infarct zones of vascular dementia patients compared to age-matched controls. The results were striking, showing a significant increase of progenitor cells in both the subventricular zone and in peri-infarct area in patients with vascular dementia compared to controls, which was sustained even in patients with infarcts occurring more than three months prior to autopsy. Moreover, the peri-infarct response appeared to be unified with that of the subventricular zone via a stream of cells, with some of them differentiating into immature neurons. We conclude that neurogenesis is stimulated in vascular dementia patients and, specifically, in patients with visible infarcts. Progenitors may migrate from the neurogenic niche to areas of infarction and differentiate into neurons, even three months after cerebrovascular damage, thus implicating the feasibility of enhancing neurogenesis as a novel treatment approach.

The effects of culture on genomic imprinting profiles in human embryonic and fetal mesenchymal stem cells.

Human embryonic stem (hES) cells and fetal mesenchymal stem cells (fMSC) offer great potential for regenerative therapy strategies. It is therefore important to characterise the properties of these cells in vitro. One major way the environment impacts on cellular physiology is through changes to epigenetic mechanisms. Genes subject to epigenetic regulation via genomic imprinting have been characterised extensively. The integrity of imprinted gene expression therefore provides a measurable index for epigenetic stability. Allelic expression of 26 imprinted genes and DNA methylation at associated differentially methylated regions (DMRs) was measured in fMSC and hES cell lines. Both cell types exhibited monoallelic expression of 13 imprinted genes, biallelic expression of six imprinted genes, and there were seven genes that differed in allelic expression between cell lines. fMSCs exhibited the differential DNA methylation patterns associated with imprinted expression. This was unexpected given that gene expression of several imprinted genes was biallelic. However, in hES cells, differential methylation was perturbed. These atypical methylation patterns did not correlate with allelic expression. Our results suggest that regardless of stem cell origin, in vitro culture affects the integrity of imprinted gene expression in human cells. We identify biallelic and variably expressed genes that may inform on overall epigenetic stability. As differential methylation did not correlate with imprinted expression changes we propose that other epigenetic effectors are adversely influenced by the in vitro environment. Since DMR integrity was maintained in fMSC but not hES cells, we postulate that specific hES cell derivation and culturing practices result in changes in methylation at DMRs.

Neural progenitors promote axon growth in vitro and ex vivo but not following injury.

Following an injury to the dorsal roots primary sensory afferents fail to regenerate past the hostile dorsal root entry zone (DREZ), the interface between the peripheral and central nervous system. Neural progenitor cells have previously been utilised as a cellular replacement therapy in a variety of CNS injury models. Here we show for the first time that NPCs are capable of promoting neurite outgrowth from adult sensory neurons in vitro and ex vivo cryo-cultures. The effectiveness of NPCs as a potential means of promoting regeneration of primary afferents across the DREZ was assessed following rhizotomy at the cervical level in the adult rat. Adult rats were subjected to rhizotomy of the dorsal roots between C(5)-T(1) which were then reanastamosed. In conjunction with the rhizotomy NPCs were delivered at the DREZ. NPCs survived transplantation and were observed to differentiate predominantly into glia. Regeneration of the dorsal root fibers was assessed with immunhistochemical analysis of the large and small diameter peptidergic and non-peptidergic afferents. Although afferents appeared near to the DREZ there was little regeneration beyond the DREZ. Furthermore, no significant improvement was observed in behavioural tasks.

Transplanted neural progenitor cells survive and differentiate but achieve limited functional recovery in the lesioned adult rat spinal cord.

UNLABELLED: Endogenous repair after injury in the adult CNS is limited by a number of factors including cellular loss, inflammation, cavitation and glial scarring. Spinal cord neural progenitor cells (SCNPCs) may provide a valuable cellular source for promoting repair following spinal cord injury. SCNPCs are multipotent, can be expanded in vitro, have the capacity to differentiate into CNS cell lineages and are capable of long-term survival following transplantation. AIMS & METHOD: To determine the extent to which SCNPCs may contribute to spinal cord repair SCNPCs isolated from rat fetal spinal cord were expanded ex vivo and transplanted into the adult rat spinal cord after a dorsal column crush lesion. RESULTS: The survival and distribution of transplanted cells were examined at 24 h, 1, 2 and 6 weeks after injury. Transplanted cells were identified at all time points, located mainly at the lesion perimeter, indicating good post-transplant cell survival. Furthermore, SCNPCs maintained their ability to differentiate in vivo, with approximately 40% differentiating into cells with a glial morphology, whilst 8% displayed a neural morphology. Transplanted animals were also assessed on a number of behavioral tasks measuring sensorimotor and proprioceptive function to determine the extent to which SCNPC transplants might attenuate lesion-induced functional deficits. SCNPCs failed to promote significant functional recovery, with a small improvement observed in only one of the four tasks employed, primarily related to improvements in sensory function. Tracing of the corticospinal tract and ascending dorsal column pathway revealed no regeneration of the axons beyond the lesion site. CONCLUSIONS: These data indicate that, although transplanted SCNPCs show good survival in the spinal cord injury environment, combination with other treatment strategies is likely to be required for these cells to fully exert their therapeutic potential.

Endogenous neurogenesis in the human brain following cerebral infarction.

Increased endogenous neurogenesis has a significant regenerative role in many experimental models of cerebrovascular diseases, but there have been very few studies in humans. We therefore examined whether there was evidence of altered endogenous neurogenesis in an 84-year-old patient who suffered a cerebrovascular accident 1 week prior to death. Using antibodies that specifically label neural stem/neural progenitor cells, we examined the presence of immunopositive cells around and distant from the infarcted area, and compared this with a control, age-matched individual. Interestingly, a large number of neural stem cells, vascular endothelial growth factor-immunopositive cells and new blood vessels were observed only around the region of infarction, and none in the corresponding brain areas of the healthy control. In addition, an increased number of neural stem cells was observed in the neurogenic region of the lateral ventricle wall. Our results suggest increased endogenous neurogenesis associated with neovascularization and migration of newly-formed cells towards a region of cerebrovascular damage in the adult human brain and highlight possible mechanisms underlying this process.