Neural precursors (NPCs) from adult L967Q mice display early commitment to “in vitro” neuronal differentiation and hyperexcitability. Exp Neurol. 2012;236:307-318. [PMID: 22634210 DOI: 10.1016/j.expneurol.2012.05.010]

Mitochondrial Dysfunction, Neurogenesis, and Epigenetics: Putative Implications for Amyotrophic Lateral Sclerosis Neurodegeneration and Treatment

Amyotrophic lateral sclerosis (ALS) is a progressive and devastating multifactorial neurodegenerative disorder. Although the pathogenesis of ALS is still not completely understood, numerous studies suggest that mitochondrial deregulation may be implicated in its onset and progression. Interestingly, mitochondrial deregulation has also been associated with changes in neural stem cells (NSC) proliferation, differentiation, and migration. In this review, we highlight the importance of mitochondrial function for neurogenesis, and how both processes are correlated and may contribute to the pathogenesis of ALS; we have focused primarily on preclinical data from animal models of ALS, since to date no studies have evaluated this link using human samples. As there is currently no cure and no effective therapy to counteract ALS, we have also discussed how improving neurogenic function by epigenetic modulation could benefit ALS. In support of this hypothesis, changes in histone deacetylation can alter mitochondrial function, which in turn might ameliorate cellular proliferation as well as neuronal differentiation and migration. We propose that modulation of epigenetics, mitochondrial function, and neurogenesis might provide new hope for ALS patients, and studies exploring these new territories are warranted in the near future.

Mutant Ataxin-1 Inhibits Neural Progenitor Cell Proliferation in SCA1

Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited neurodegenerative disease caused by the expansion of a polyglutamine (Q) repeat tract in the protein ataxin-1 (ATXN1). Beginning as a cerebellar ataxic disorder, SCA1 progresses to involve the cerebral cortex, hippocampus, and brainstem. Using SCA1 knock-in mice that mirror the complexity of the human disease, we report a significant decrease in the capacity of adult neuronal progenitor cells (NPCs) to proliferate. Remarkably, a decrease in NPCs proliferation can be observed in vitro, outside the degenerative milieu of surrounding neurons or glia, demonstrating that mutant ATXN1 acting cell autonomously within progenitor cells interferes with their ability to proliferate. Our findings suggest that compromised adult neurogenesis contributes to the progressive pathology of the disease particularly in areas such as the hippocampus and cerebral cortex where stem cells provide neurotropic factors and participate in adult neurogenesis. These findings not only shed light on the biology of the disease but also have therapeutic implications in any future stem cell-based clinical trials.

Importance of being Nernst: Synaptic activity and functional relevance in stem cell-derived neurons

Functional synaptogenesis and network emergence are signature endpoints of neurogenesis. These behaviors provide higher-order confirmation that biochemical and cellular processes necessary for neurotransmitter release, post-synaptic detection and network propagation of neuronal activity have been properly expressed and coordinated among cells. The development of synaptic neurotransmission can therefore be considered a defining property of neurons. Although dissociated primary neuron cultures readily form functioning synapses and network behaviors in vitro, continuously cultured neurogenic cell lines have historically failed to meet these criteria. Therefore, in vitro-derived neuron models that develop synaptic transmission are critically needed for a wide array of studies, including molecular neuroscience, developmental neurogenesis, disease research and neurotoxicology. Over the last decade, neurons derived from various stem cell lines have shown varying ability to develop into functionally mature neurons. In this review, we will discuss the neurogenic potential of various stem cells populations, addressing strengths and weaknesses of each, with particular attention to the emergence of functional behaviors. We will propose methods to functionally characterize new stem cell-derived neuron (SCN) platforms to improve their reliability as physiological relevant models. Finally, we will review how synaptically active SCNs can be applied to accelerate research in a variety of areas. Ultimately, emphasizing the critical importance of synaptic activity and network responses as a marker of neuronal maturation is anticipated to result in in vitro findings that better translate to efficacious clinical treatments.

Neuroprotective effects of the Sigma-1 receptor (S1R) agonist PRE-084, in a mouse model of motor neuron disease not linked to SOD1 mutation

The identification of novel molecular targets crucially involved in motor neuron degeneration/survival is a necessary step for the development of hopefully more effective therapeutic strategies for amyotrophic lateral sclerosis (ALS) patients. In this view, S1R, an endoplasmic reticulum (ER)-resident receptor with chaperone-like activity, has recently attracted great interest. S1R is involved in several processes leading to acute and chronic neurodegeneration, including ALS pathology. Treatment with the S1R agonist PRE-084 improves locomotor function and motor neuron survival in presymptomatic and early symptomatic mutant SOD1-G93A ALS mice. Here, we tested the efficacy of PRE-084 in a model of spontaneous motor neuron degeneration, the wobbler mouse (wr) as a proof of concept that S1R may be regarded as a key therapeutic target also for ALS cases not linked to SOD1 mutation. Increased staining for S1R was detectable in morphologically spared cervical spinal cord motor neurons of wr mice both at early (6th week) and late (12th week) phases of clinical progression. S1R signal was also detectable in hypertrophic astrocytes and reactive microglia of wr mice. Chronic treatment with PRE-084 (three times a week, for 8weeks), starting at symptom onset, significantly increased the levels of BDNF in the gray matter, improved motor neuron survival and ameliorated paw abnormality and grip strength performance. In addition, the treatment significantly reduced the number of reactive astrocytes whereas, that of CD11b+ microglial cells was increased. A deeper evaluation of microglial markers revealed significant increased number of cells positive for the pan-macrophage marker CD68 and of CD206+ cells, involved in tissue restoration, in the white matter of PRE-084-treated mice. The mRNA levels of TNF-α and IL-1β were not affected by PRE-084 treatment. Thus, our results support pharmacological manipulation of S1R as a promising strategy to cure ALS and point to increased availability of growth factors and modulation of astrocytosis and of macrophage/microglia as part of the mechanisms involved in S1R-mediated neuroprotection.

Altered miRNA expression is associated with neuronal fate in G93A-SOD1 ependymal stem progenitor cells

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive motoneuron loss in the CNS. In G93A-SOD1 mice, motoneuron degeneration is associated with proliferative restorative attempts of ependymal stem progenitor cells (epSPCs), usually quiescent in the spinal cord. The aims of the study were to demonstrate that epSPCs isolated from the spinal cord of G93A-SOD1 mice express neurogenic potential in vitro, and thus gain a better understanding of epSPC neural differentiation properties. For this purpose, we compared the ability of epSPCs from asymptomatic and symptomatic G93A-SOD1 and WT SOD1 transgenic mice to proliferate and differentiate into neural cells. Compared to control cells, G93A-SOD1 epSPCs differentiated more into neurons than into astrocytes, whereas oligodendrocyte proportions were similar in the two populations. G93A-SOD1 neurons were small and astrocytes had an activated phenotype. Evaluation of microRNAs, specific for neural cell fate and cell-cycle regulation, in G93A-SOD1 epSPCs showed that miR-9, miR-124a, miR-19a and miR-19b were differentially expressed. Expression analysis of the predicted miRNA targets allowed identification of a functional network in which Hes1, Pten, Socs1, and Stat3 genes were important for controlling epSPC fate. Our findings demonstrate that G93A-SOD1 epSPCs are a source of multipotent cells that have neurogenic potential in vitro, and might be a useful tool to investigate the mechanisms of neural differentiation in relation to miRNA expression whose modulation might constitute new targeted therapeutic approaches to ALS.

Neurorescue effects and stem properties of chorionic villi and amniotic progenitor cells

The capability to integrate into degenerative environment, release neurotrophic cytokines, contrast oxidative stress and an inherent differentiation potential towards siteappropriate phenotypes are considered crucial for the use of stem cells in tissue repair and regeneration. Naïve human chorial villi- (hCVCs) and amniotic fluid- (hAFCs) derived cells, whose properties and potentiality have not been extensively investigated, may represent two novel foetal cell sources for stem cell therapy. We previously described that long-term transplantation of hAFCs in the lateral ventricles of wobbler and healthy mice was feasible and safe. In the present study we examine the in vitro intrinsic stem potential of hCVCs and hAFCs for future therapeutic applications in neurodegenerative disorders. Presence of stem lineages was evaluated assessing the expression pattern of relevant candidate markers by flow cytometry, reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemistry. Release of cytokines that may potentialy sustain endogenous neurogenesis and/or activate neuroprotective pathways was quantified by enzyme-linked immunosorbent assays (ELISAs). We also performed an in vitro neurorescue assay, wherein a neuroblastoma cell line damaged by 6-hydroxydopamine (6-OHDA) was treated with hCVC/hAFC-derived conditioned medium (CM). Naïve hCVCs/hAFCs show a neurogenic/angiogenic predisposition. Both cell types express several specific neural stem/progenitor markers, such as nestin and connexin 43, and release significant amounts of brain-derived neurotrophic factor, as well as vascular endothelial growth factor. hCVC and hAFC populations comprise several interesting cell lineages, including mesenchymal stem cells (MSCs) and cells with neural-like phenotypes. Moreover, although CMs obtained from both cell cultures actively sustained metabolic activity in a 6-OHDA-induced Parkinson's disease (PD) cell model, only hCVC-derived CMs significantly reduced neurotoxin-induced apoptosis. In conclusion, this study demonstrates that naïve hAFCs and hCVCs may enhance cell-recovery following neuronal damage through multiple rescue mechanisms, and may provide a suitable means of stem cell therapy for neurodegenerative disorders including PD.