Differentiation of Human Neural Stem Cells into Motor Neurons Stimulates Mitochondrial Biogenesis and Decreases Glycolytic Flux

Lineage-specific changes in mitochondrial properties during neural stem cell differentiation

Neural stem cells (NSCs) reside in discrete regions of the adult mammalian brain where they can differentiate into neurons, astrocytes, and oligodendrocytes. Several studies suggest that mitochondria have a major role in regulating NSC fate. Here, we evaluated mitochondrial properties throughout NSC differentiation and in lineage-specific cells. For this, we used the neurosphere assay model to isolate, expand, and differentiate mouse subventricular zone postnatal NSCs. We found that the levels of proteins involved in mitochondrial fusion (Mitofusin [Mfn] 1 and Mfn 2) increased, whereas proteins involved in fission (dynamin-related protein 1 [DRP1]) decreased along differentiation. Importantly, changes in mitochondrial dynamics correlated with distinct patterns of mitochondrial morphology in each lineage. Particularly, we found that the number of branched and unbranched mitochondria increased during astroglial and neuronal differentiation, whereas the area occupied by mitochondrial structures significantly reduced with oligodendrocyte maturation. In addition, comparing the three lineages, neurons revealed to be the most energetically flexible, whereas astrocytes presented the highest ATP content. Our work identified putative mitochondrial targets to enhance lineage-directed differentiation of mouse subventricular zone-derived NSCs.

High OXPHOS efficiency in RA-FUdr-differentiated SH-SY5Y cells: involvement of cAMP signalling and respiratory supercomplexes

Neurons are highly dependent on mitochondria to meet their bioenergetic needs and understanding the metabolic changes during the differentiation process is crucial in the neurodegeneration context. Several in vitro approaches have been developed to study neuronal differentiation and bioenergetic changes. The human SH-SY5Y cell line is a widely used cellular model and several differentiation protocols have been developed to induce a neuron-like phenotype including retinoic acid (RA) treatment. In this work we obtained a homogeneous functional population of neuron-like cells by a two-step differentiation protocol in which SH-SY5Y cells were treated with RA plus the mitotic inhibitor 2-deoxy-5-fluorouridine (FUdr). RA-FUdr treatment induced a neuronal phenotype characterized by increased expression of neuronal markers and electrical properties specific to excitable cells. In addition, the RA-FUdr differentiated cells showed an enrichment of long chain and unsaturated fatty acids (FA) in the acyl chain composition of cardiolipin (CL) and the bioenergetic analysis evidences a high coupled and maximal respiration associated with high mitochondrial ATP levels. Our results suggest that the observed high oxidative phosphorylation (OXPHOS) capacity may be related to the activation of the cyclic adenosine monophosphate (cAMP) pathway and the assembly of respiratory supercomplexes (SCs), highlighting the change in mitochondrial phenotype during neuronal differentiation.

Combined transplantation of hiPSC-NSC and hMSC ameliorated neuroinflammation and promoted neuroregeneration in acute spinal cord injury

BACKGROUND

Spinal cord injury (SCI) is a serious clinical condition that has pathological changes such as increased neuroinflammation and nerve tissue damage, which eventually manifests as fibrosis of the injured segment and the development of a spinal cord cavity leading to loss of function. Cell-based therapy, such as mesenchymal stem cells (MSCs) and neural stem cells (NSCs) are promising treatment strategies for spinal cord injury via immunological regulation and neural replacement respectively. However, therapeutic efficacy is rare reported on combined transplantation of MSC and NSC in acute mice spinal cord injury even the potential reinforcement might be foreseen. Therefore, this study was conducted to investigate the safety and efficacy of co-transplanting of MSC and NSC sheets into an SCI mice model on the locomotor function and pathological changes of injured spinal cord.

METHODS

To evaluate the therapeutic effects of combination cells, acute SCI mice model were established and combined transplantation of hiPSC-NSCs and hMSCs into the lesion site immediately after the injury. Basso mouse scale was used to perform the open-field tests of hind limb motor function at days post-operation (dpo) 1, 3, 5, and 7 after SCI and every week after surgery. Spinal cord and serum samples were collected at dpo 7, 14, and 28 to detect inflammatory and neurotrophic factors. Hematoxylin-eosin (H&E) staining, masson staining and transmission electron microscopy were used to evaluate the morphological changes, fibrosis area and ultrastructure of the spinal cord.

RESULT

M&N transplantation reduced fibrosis formation and the inflammation level while promoting the secretion of nerve growth factor and brain-derived neurotrophic factor. We observed significant reduction in damaged tissue and cavity area, with dramatic improvement in the M&N group. Compared with the Con group, the M&N group exhibited significantly improved behaviors, particularly limb coordination.

CONCLUSION

Combined transplantation of hiPSC-NSC and hMSC could significantly ameliorate neuroinflammation, promote neuroregeneration, and decrease spinal fibrosis degree in safe and effective pattern, which would be indicated as a novel potential cell treatment option.

Mitochondria in the Central Nervous System in Health and Disease: The Puzzle of the Therapeutic Potential of Mitochondrial Transplantation

Mitochondria, the energy suppliers of the cells, play a central role in a variety of cellular processes essential for survival or leading to cell death. Consequently, mitochondrial dysfunction is implicated in numerous general and CNS disorders. The clinical manifestations of mitochondrial dysfunction include metabolic disorders, dysfunction of the immune system, tumorigenesis, and neuronal and behavioral abnormalities. In this review, we focus on the mitochondrial role in the CNS, which has unique characteristics and is therefore highly dependent on the mitochondria. First, we review the role of mitochondria in neuronal development, synaptogenesis, plasticity, and behavior as well as their adaptation to the intricate connections between the different cell types in the brain. Then, we review the sparse knowledge of the mechanisms of exogenous mitochondrial uptake and describe attempts to determine their half-life and transplantation long-term effects on neuronal sprouting, cellular proteome, and behavior. We further discuss the potential of mitochondrial transplantation to serve as a tool to study the causal link between mitochondria and neuronal activity and behavior. Next, we describe mitochondrial transplantation's therapeutic potential in various CNS disorders. Finally, we discuss the basic and reverse-translation challenges of this approach that currently hinder the clinical use of mitochondrial transplantation.

Emerging Functional Connections Between Metabolism and Epigenetic Remodeling in Neural Differentiation

Stem cells possess extraordinary capacities for self-renewal and differentiation, making them highly valuable in regenerative medicine. Among these, neural stem cells (NSCs) play a fundamental role in neural development and repair processes. NSC characteristics and fate are intricately regulated by the microenvironment and intracellular signaling. Interestingly, metabolism plays a pivotal role in orchestrating the epigenome dynamics during neural differentiation, facilitating the transition from undifferentiated NSC to specialized neuronal and glial cell types. This intricate interplay between metabolism and the epigenome is essential for precisely regulating gene expression patterns and ensuring proper neural development. This review highlights the mechanisms behind metabolic regulation of NSC fate and their connections with epigenetic regulation to shape transcriptional programs of stemness and neural differentiation. A comprehensive understanding of these molecular gears appears fundamental for translational applications in regenerative medicine and personalized therapies for neurological conditions.

Humanin ameliorates TBI-related cognitive impairment by attenuating mitochondrial dysfunction and inflammation

Traumatic brain injury (TBI) often results in a reduction of the capacity of cells to sustain energy demands, thus, compromising neuronal function and plasticity. Here we show that the mitochondrial activator humanin (HN) counteracts a TBI-related reduction in mitochondrial bioenergetics, including oxygen consumption rate. HN normalized the disruptive action of TBI on memory function, and restored levels of synaptic proteins (synapsin 1 and p-CREB). HN also counteracted TBI-related elevations of pro-inflammatory cytokines in plasma (TNF-α, INF-y, IL 17, IL 5, MCP 5, GCSF, RANNETS, sTNFRI) as well as in the hippocampus (gp-130 and p-STAT3). Gp-130 is an integral part of cytokine receptor impinging on STAT3 (Tyr-705) signaling. Furthermore, HN reduced astrocyte proliferation in TBI. The overall evidence suggests that HN plays an integral role in normalizing fundamental aspects of TBI pathology which are central to energy balance, brain function, and plasticity.

Mitochondrial Dynamics and Cristae Shape Changes During Metabolic Reprogramming

Significance: The architecture of the mitochondrial network and cristae critically impact cell differentiation and identity. Cells undergoing metabolic reprogramming to aerobic glycolysis (Warburg effect), such as immune cells, stem cells, and cancer cells, go through controlled modifications in mitochondrial architecture, which is critical for achieving the resulting cellular phenotype. Recent Advances: Recent studies in immunometabolism have shown that the manipulation of mitochondrial network dynamics and cristae shape directly affects T cell phenotype and macrophage polarization through altering energy metabolism. Similar manipulations also alter the specific metabolic phenotypes that accompany somatic reprogramming, stem cell differentiation, and cancer cells. The modulation of oxidative phosphorylation activity, accompanied by changes in metabolite signaling, reactive oxygen species generation, and adenosine triphosphate levels, is the shared underlying mechanism. Critical Issues: The plasticity of mitochondrial architecture is particularly vital for metabolic reprogramming. Consequently, failure to adapt the appropriate mitochondrial morphology often compromises the differentiation and identity of the cell. Immune, stem, and tumor cells exhibit striking similarities in their coordination of mitochondrial morphology with metabolic pathways. However, although many general unifying principles can be observed, their validity is not absolute, and the mechanistic links thus need to be further explored. Future Directions: Better knowledge of the molecular mechanisms involved and their relationships to both mitochondrial network and cristae morphology will not only further deepen our understanding of energy metabolism but may also contribute to improved therapeutic manipulation of cell viability, differentiation, proliferation, and identity in many different cell types. Antioxid. Redox Signal. 39, 684-707.

Understanding the role of hyperglycemia and the molecular mechanism associated with diabetic neuropathy and possible therapeutic strategies

Diabetic neuropathy is a neuro-degenerative disorder that encompasses numerous factors that impact peripheral nerves in the context of diabetes mellitus (DM). Diabetic peripheral neuropathy (DPN) is very prevalent and impacts 50% of diabetic patients. DPN is a length-dependent peripheral nerve lesion that primarily causes distal sensory loss, discomfort, and foot ulceration that may lead to amputation. The pathophysiology is yet to be fully understood, but current literature on the pathophysiology of DPN revolves around understanding various signaling cascades involving the polyol, hexosamine, protein-kinase C, AGE, oxidative stress, and poly (ADP ribose) polymerase pathways. The results of research have suggested that hyperglycemia target Schwann cells and in severe cases, demyelination resulting in central and peripheral sensitization is evident in diabetic patients. Various diagnostic approaches are available, but detection at an early stage remains a challenge. Traditional analgesics and opioids that can be used "as required" have not been the mainstay of treatment thus far. Instead, anticonvulsants and antidepressants that must be taken routinely over time have been the most common treatments. For now, prolonging life and preserving the quality of life are the ultimate goals of diabetes treatment. Furthermore, the rising prevalence of DPN has substantial consequences for occupational therapy because such therapy is necessary for supporting wellness, warding off other chronic-diseases, and avoiding the development of a disability; this is accomplished by engaging in fulfilling activities like yoga, meditation, and physical exercise. Therefore, occupational therapy, along with palliative therapy, may prove to be crucial in halting the onset of neuropathic-symptoms and in lessening those symptoms once they have occurred.

Brain Mitochondrial Bioenergetics in Genetic Neurodevelopmental Disorders: Focus on Down, Rett and Fragile X Syndromes

Mitochondria, far beyond their prominent role as cellular powerhouses, are complex cellular organelles active as central metabolic hubs that are capable of integrating and controlling several signaling pathways essential for neurological processes, including neurogenesis and neuroplasticity. On the other hand, mitochondria are themselves regulated from a series of signaling proteins to achieve the best efficiency in producing energy, in establishing a network and in performing their own de novo synthesis or clearance. Dysfunctions in signaling processes that control mitochondrial biogenesis, dynamics and bioenergetics are increasingly associated with impairment in brain development and involved in a wide variety of neurodevelopmental disorders. Here, we review recent evidence proving the emerging role of mitochondria as master regulators of brain bioenergetics, highlighting their control skills in brain neurodevelopment and cognition. We analyze, from a mechanistic point of view, mitochondrial bioenergetic dysfunction as causally interrelated to the origins of typical genetic intellectual disability-related neurodevelopmental disorders, such as Down, Rett and Fragile X syndromes. Finally, we discuss whether mitochondria can become therapeutic targets to improve brain development and function from a holistic perspective.

Mitochondrial regulation of local supply of energy in neurons

Brain computation is metabolically expensive and requires the supply of significant amounts of energy. Mitochondria are highly specialized organelles whose main function is to generate cellular energy. Due to their complex morphologies, neurons are especially dependent on a set of tools necessary to regulate mitochondrial function locally in order to match energy provision with local demands. By regulating mitochondrial transport, neurons control the local availability of mitochondrial mass in response to changes in synaptic activity. Neurons also modulate mitochondrial dynamics locally to adjust metabolic efficiency with energetic demand. Additionally, neurons remove inefficient mitochondria through mitophagy. Neurons coordinate these processes through signalling pathways that couple energetic expenditure with energy availability. When these mechanisms fail, neurons can no longer support brain function giving rise to neuropathological states like metabolic syndromes or neurodegeneration.

Molecular Beacon Imaging System to Discriminate the Differentiation State of Cells from Energy Metabolic Pathways

Metabolic pathways of energy production play an essential role as a function of cells. It is well recognized that the differentiation state of stem cells is highly associated with their metabolic profile. Therefore, visualization of the energy metabolic pathway makes it possible to discriminate the differentiation state of cells and predict the cell potential for reprogramming and differentiation. However, at present, it is technically difficult to directly assess the metabolic profile of individual living cells. In this study, we developed an imaging system of cationized gelatin nanospheres (cGNS) incorporating molecular beacons (MB) (cGNSMB) to detect intracellular pyruvate dehydrogenase kinase 1 (PDK1) and peroxisome proliferator-activated receptor γ, coactivator-1α (PGC-1α) mRNA of key regulators in the energy metabolism. The prepared cGNSMB was readily internalized into mouse embryonic stem cells, while their pluripotency was maintained. The high level of glycolysis in the undifferentiated state, the increased oxidative phosphorylation over the spontaneous early differentiation, and the lineage-specific neural differentiation were visualized based on the MB fluorescence. The fluorescence intensity corresponded well to the change of extracellular acidification rate and the oxygen consumption rate of representative metabolic indicators. These findings indicate that the cGNSMB imaging system is a promising tool to visually discriminate the differentiation state of cells from energy metabolic pathways.

Molecular phenotypes of mitochondrial dysfunction in clinically non-manifesting heterozygous PRKN variant carriers

Homozygous or compound heterozygous (biallelic) variants in PRKN are causal for PD with highly penetrant symptom expression, while the much more common heterozygous variants may predispose to PD with highly reduced penetrance, through altered mitochondrial function. In the presence of pathogenic heterozygous variants, it is therefore important to test for mitochondrial alteration in cells derived from variant carriers to establish potential presymptomatic molecular markers. We generated lymphoblasts (LCLs) and human induced pluripotent stem cell (hiPSC)-derived neurons from non-manifesting heterozygous PRKN variant carriers and tested them for mitochondrial functionality. In LCLs, we detected hyperactive mitochondrial respiration, and, although milder compared to a biallelic PRKN-PD patient, hiPSC-derived neurons of non-manifesting heterozygous variant carriers also displayed several phenotypes of altered mitochondrial function. Overall, we identified molecular phenotypes that might be used to monitor heterozygous PRKN variant carriers during the prodromal phase. Such markers might also be useful to identify individuals at greater risk of eventual disease development and for testing potential mitochondrial function-based neuroprotective therapies before neurodegeneration advances.

Characterization of mitochondrial and metabolic alterations induced by trisomy 21 during neural differentiation

Cellular redox state directs differentiation of induced pluripotent stem cells (iPSC) by energy metabolism control and ROS generation. As oxidative stress and mitochondrial dysfunction have been extensively reported in Down syndrome (DS), we evaluated mitochondrial phenotypes and energy metabolism during neural differentiation of DS iPSCs to neural progenitor cells (NPCs). Our results indicate early maturation of mitochondrial networks and elevated NADPH oxidase 4 (NOX4) expression in DS iPSCs. DS cells also fail to transition from glycolysis to oxidative phosphorylation during differentiation. Specifically, DS NPCs show an increased energetic demand that is limited in their mitochondrial and glycolytic response to mitochondrial distress. Additionally, DS iPSC and NPC non-mitochondrial oxygen consumption was significantly impacted by NOX inhibition. Together, these data build upon previous evidence of accelerated neural differentiation in DS that correlates with cellular redox state. We demonstrate the potential for mitochondrial and non-mitochondrial ROS sources to impact differentiation timing in the context of DS, which could contribute to developmental deficits in this condition.

Mitochondrial DNA Mutations and Ageing

Mitochondria are subcellular organelles present in most eukaryotic cells which play a significant role in numerous aspects of cell biology. These include carbohydrate and fatty acid metabolism to generate cellular energy through oxidative phosphorylation, apoptosis, cell signalling, haem biosynthesis and reactive oxygen species production. Mitochondrial dysfunction is a feature of many human ageing tissues, and since the discovery that mitochondrial DNA mutations were a major underlying cause of changes in oxidative phosphorylation capacity, it has been proposed that they have a role in human ageing. However, there is still much debate on whether mitochondrial DNA mutations play a causal role in ageing or are simply a consequence of the ageing process. This chapter describes the structure of mammalian mitochondria, and the unique features of mitochondrial genetics, and reviews the current evidence surrounding the role of mitochondrial DNA mutations in the ageing process. It then focusses on more recent discoveries regarding the role of mitochondrial dysfunction in stem cell ageing and age-related inflammation.

NSC Physiological Features in Spinal Muscular Atrophy: SMN Deficiency Effects on Neurogenesis

While the U.S. Food and Drug Administration and the European Medicines Evaluation Agency have recently approved new drugs to treat spinal muscular atrophy 1 (SMA1) in young patients, they are mostly ineffective in older patients since many motor neurons have already been lost. Therefore, understanding nervous system (NS) physiology in SMA patients is essential. Consequently, studying neural stem cells (NSCs) from SMA patients is of significant interest in searching for new treatment targets that will enable researchers to identify new pharmacological approaches. However, studying NSCs in these patients is challenging since their isolation damages the NS, making it impossible with living patients. Nevertheless, it is possible to study NSCs from animal models or create them by differentiating induced pluripotent stem cells obtained from SMA patient peripheral tissues. On the other hand, therapeutic interventions such as NSCs transplantation could ameliorate SMA condition. This review summarizes current knowledge on the physiological properties of NSCs from animals and human cellular models with an SMA background converging on the molecular and neuronal circuit formation alterations of SMA fetuses and is not focused on the treatment of SMA. By understanding how SMA alters NSC physiology, we can identify new and promising interventions that could help support affected patients.

Metabolic regulation of the neural stem cell fate: Unraveling new connections, establishing new concepts

The neural stem cell niche is a key regulator participating in the maintenance, regeneration, and repair of the brain. Within the niche neural stem cells (NSC) generate new neurons throughout life, which is important for tissue homeostasis and brain function. NSCs are regulated by intrinsic and extrinsic factors with cellular metabolism being lately recognized as one of the most important ones, with evidence suggesting that it may serve as a common signal integrator to ensure mammalian brain homeostasis. The aim of this review is to summarize recent insights into how metabolism affects NSC fate decisions in adult neural stem cell niches, with occasional referencing of embryonic neural stem cells when it is deemed necessary. Specifically, we will highlight the implication of mitochondria as crucial regulators of NSC fate decisions and the relationship between metabolism and ependymal cells. The link between primary cilia dysfunction in the region of hypothalamus and metabolic diseases will be examined as well. Lastly, the involvement of metabolic pathways in ependymal cell ciliogenesis and physiology regulation will be discussed.

Phenotypic, metabolic, and biogenesis properties of human stem cell-derived cerebellar spheroids

Human cerebellum consists of high density and complexity of neurons. Thus, it is challenging to differentiate cerebellar-like organoids with similar cellular markers and function to the human brain. Our previous study showed that the combination of retinoic acid (RA), Wingless/integrated (Wnt) activator, and Sonic Hedgehog (SHH) activator promotes cerebellar differentiation from human induced pluripotent stem cells (hiPSCs). This study examined phenotypic, metabolic, and biogenesis in early cerebellar development. Cerebellum spheroids were differentiated from human iPSK3 cells. During day 7–14, RA and Wnt activator CHIR99021 were used and SHH activator purmorphamine (PMR) was added later to promote ventralization. Gene expression for early cerebellar layer markers, metabolism, and extracellular vesicle (EV) biogenesis were characterized. Zinc-induced neurotoxicity was investigated as a proof-of-concept of neurotoxicity study. Flow cytometry results showed that there was no significant difference in NEPH3, PTF1A, OLIG2, and MATH1 protein expression between RCP (RA-CHIR-PMR) versus the control condition. However, the expression of cerebellar genes for the molecular layer (BHLE22), the granule cell layer (GABRB2, PAX6, TMEM266, KCNIP4), the Bergmann glial cells (QK1, DAO), and the Purkinje cell layer (ARHGEF33, KIT, MX1, MYH10, PPP1R17, SCGN) was significantly higher in the RCP condition than the control. The shift in metabolic pathways toward glycolysis was observed for RCP condition. The EV biogenesis marker expression was retained. Mild zinc-induced neurotoxicity may exist when zinc exposure exceeds 1.0 µM. RCP treatment can promote specific cerebellar-like differentiation from hiPSCs indicated by gene expression of early cerebellar markers and regionally enriched genes. The higher cerebellar marker expression is accompanied by the elevated glycolysis with the retained EV biogenesis. This study should advance the understanding of biomarkers during early cerebellar development for cerebellum organoid engineering and neurotoxicity study.

Mitochondrial function and dynamics in neural stem cells and neurogenesis: Implications for neurodegenerative diseases

Mitochondria have been largely described as the powerhouse of the cell and recent findings demonstrate that this organelle is fundamental for neurogenesis. The mechanisms underlying neural stem cells (NSCs) maintenance and differentiation are highly regulated by both intrinsic and extrinsic factors. Mitochondrial-mediated switch from glycolysis to oxidative phosphorylation, accompanied by mitochondrial remodeling and dynamics are vital to NSCs fate. Deregulation of mitochondrial proteins, mitochondrial DNA, function, fission/fusion and metabolism underly several neurodegenerative diseases; data show that these impairments are already present in early developmental stages and NSC fate decisions. However, little is known about mitochondrial role in neurogenesis. In this Review, we describe the recent evidence covering mitochondrial role in neurogenesis, its impact in selected neurodegenerative diseases, for which aging is the major risk factor, and the recent advances in stem cell-based therapies that may alleviate neurodegenerative disorders-related neuronal deregulation through improvement of mitochondrial function and dynamics.

POLG mutations lead to abnormal mitochondrial remodeling during neural differentiation of human pluripotent stem cells via SIRT3/AMPK pathway inhibition

We showed previously that POLG mutations cause major changes in mitochondrial function, including loss of mitochondrial respiratory chain (MRC) complex I, mitochondrial DNA (mtDNA) depletion and an abnormal NAD⁺/NADH ratio in both neural stem cells (NSCs) and astrocytes differentiated from induced pluripotent stem cells (iPSCs). In the current study, we looked at mitochondrial remodeling as stem cells transit pluripotency and during differentiation from NSCs to both dopaminergic (DA) neurons and astrocytes comparing the process in POLG-mutated and control stem cells. We saw that mitochondrial membrane potential (MMP), mitochondrial volume, ATP production and reactive oxygen species (ROS) changed in similar ways in POLG and control NSCs, but mtDNA replication, MRC complex I and NAD⁺ metabolism failed to remodel normally. In DA neurons differentiated from NSCs, we saw that POLG mutations caused failure to increase MMP and ATP production and blunted the increase in mtDNA and complex I. Interestingly, mitochondrial remodeling during astrocyte differentiation from NSCs was similar in both POLG-mutated and control NSCs. Further, we showed downregulation of the SIRT3/AMPK pathways in POLG-mutated cells, suggesting that POLG mutations lead to abnormal mitochondrial remodeling in early neural development due to the downregulation of these pathways. [Figure: see text].

Maternal Inflammation During Pregnancy and Offspring Brain Development: The Role of Mitochondria

The association between maternal immune activation (MIA) during pregnancy and risk for offspring neuropsychiatric disorders has been increasingly recognized over the past several years. Among the mechanistic pathways that have been described through which maternal inflammation during pregnancy may affect fetal brain development, the role of mitochondria has received little attention. In this review, the role of mitochondria as a potential mediator of the association between MIA during pregnancy and offspring brain development and risk for psychiatric disorders will be proposed. As a basis for this postulation, convergent evidence is presented supporting the obligatory role of mitochondria in brain development, the role of mitochondria as mediators and initiators of inflammatory processes, and evidence of mitochondrial dysfunction in preclinical MIA exposure models and human neurodevelopmental disorders. Elucidating the role of mitochondria as a potential mediator of MIA-induced alterations in brain development and neurodevelopmental disease risk may not only provide new insight into the pathophysiology of mental health disorders that have their origins in exposure to infection/immune activation during pregnancy but also offer new therapeutic targets.

Mitochondrial function in spinal cord injury and regeneration

Many people around the world suffer from some form of paralysis caused by spinal cord injury (SCI), which has an impact on quality and life expectancy. The spinal cord is part of the central nervous system (CNS), which in mammals is unable to regenerate, and to date, there is a lack of full functional recovery therapies for SCI. These injuries start with a rapid and mechanical insult, followed by a secondary phase leading progressively to greater damage. This secondary phase can be potentially modifiable through targeted therapies. The growing literature, derived from mammalian and regenerative model studies, supports a leading role for mitochondria in every cellular response after SCI: mitochondrial dysfunction is the common event of different triggers leading to cell death, cellular metabolism regulates the immune response, mitochondrial number and localization correlate with axon regenerative capacity, while mitochondrial abundance and substrate utilization regulate neural stem progenitor cells self-renewal and differentiation. Herein, we present a comprehensive review of the cellular responses during the secondary phase of SCI, the mitochondrial contribution to each of them, as well as evidence of mitochondrial involvement in spinal cord regeneration, suggesting that a more in-depth study of mitochondrial function and regulation is needed to identify potential targets for SCI therapeutic intervention.

Mitochondria and Other Organelles in Neural Development and Their Potential as Therapeutic Targets in Neurodegenerative Diseases

The contribution of organelles to neural development has received increasing attention. Studies have shown that organelles such as mitochondria, endoplasmic reticulum (ER), lysosomes, and endosomes play important roles in neurogenesis. Specifically, metabolic switching, reactive oxygen species production, mitochondrial dynamics, mitophagy, mitochondria-mediated apoptosis, and the interaction between mitochondria and the ER all have roles in neurogenesis. Lysosomes and endosomes can regulate neurite growth and extension. Moreover, metabolic reprogramming represents a novel strategy for generating functional neurons. Accordingly, the exploration and application of mechanisms underlying metabolic reprogramming will be beneficial for neural conversion and regenerative medicine. There is adequate evidence implicating the dysfunction of cellular organelles—especially mitochondria—in neurodegenerative disorders, and that improvement of mitochondrial function may reverse the progression of these diseases through the reinforcement of adult neurogenesis. Therefore, these organelles have potential as therapeutic targets for the treatment of neurodegenerative diseases. In this review, we discuss the function of these organelles, especially mitochondria, in neural development, focusing on their potential as therapeutic targets in neurodegenerative disorders, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis.

Significance of mitochondrial activity in neurogenesis and neurodegenerative diseases

Mitochondria play a multidimensional role in the function and the vitality of the neurological system. From the generation of neural stem cells to the maintenance of neurons and their ultimate demise, mitochondria play a critical role in regulating our neural pathways' homeostasis, a task that is critical to our cognitive health and neurological well-being. Mitochondria provide energy via oxidative phosphorylation for the neurotransmission and generation of an action potential along the neuron's axon. This paper will first review and examine the molecular subtleties of the mitochondria's role in neurogenesis and neuron vitality, as well as outlining the impact of defective mitochondria in neural aging. The authors will then summarize neurodegenerative diseases related to either neurogenesis or homeostatic dysfunction. Because of the significant detriment neurodegenerative diseases have on the quality of life, it is essential to understand their etiology and ongoing molecular mechanics. The mitochondrial role in neurogenesis and neuron vitality is essential. Dissecting and understanding this organelle's role in the genesis and homeostasis of neurons should assist in finding pharmaceutical targets for neurodegenerative diseases.

Covering the Role of PGC-1α in the Nervous System

The peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) is a well-known transcriptional coactivator involved in mitochondrial biogenesis. PGC-1α is implicated in the pathophysiology of many neurodegenerative disorders; therefore, a deep understanding of its functioning in the nervous system may lead to the development of new therapeutic strategies. The central nervous system (CNS)-specific isoforms of PGC-1α have been recently identified, and many functions of PGC-1α are assigned to the particular cell types of the central nervous system. In the mice CNS, deficiency of PGC-1α disturbed viability and functioning of interneurons and dopaminergic neurons, followed by alterations in inhibitory signaling and behavioral dysfunction. Furthermore, in the ALS rodent model, PGC-1α protects upper motoneurons from neurodegeneration. PGC-1α is engaged in the generation of neuromuscular junctions by lower motoneurons, protection of photoreceptors, and reduction in oxidative stress in sensory neurons. Furthermore, in the glial cells, PGC-1α is essential for the maturation and proliferation of astrocytes, myelination by oligodendrocytes, and mitophagy and autophagy of microglia. PGC-1α is also necessary for synaptogenesis in the developing brain and the generation and maintenance of synapses in postnatal life. This review provides an outlook of recent studies on the role of PGC-1α in various cells in the central nervous system.

Differences in Glycolysis and Mitochondrial Respiration between Cytotrophoblast and Syncytiotrophoblast In-Vitro: Evidence for Sexual Dimorphism

In the placenta the proliferative cytotrophoblast cells fuse into the terminally differentiated syncytiotrophoblast layer which undertakes several energy-intensive functions including nutrient uptake and transfer and hormone synthesis. We used Seahorse glycolytic and mitochondrial stress tests on trophoblast cells isolated at term from women of healthy weight to evaluate if cytotrophoblast (CT) and syncytiotrophoblast (ST) have different bioenergetic strategies, given their different functions. Whereas there are no differences in basal glycolysis, CT have significantly greater glycolytic capacity and reserve than ST. In contrast, ST have significantly higher basal, ATP-coupled and maximal mitochondrial respiration and spare capacity than CT. Consequently, under stress conditions CT can increase energy generation via its higher glycolytic capacity whereas ST can use its higher and more efficient mitochondrial respiration capacity. We have previously shown that with adverse in utero conditions of diabetes and obesity trophoblast respiration is sexually dimorphic. We found no differences in glycolytic parameters between sexes and no difference in mitochondrial respiration parameters other than increases seen upon syncytialization appear to be greater in females. There were differences in metabolic flexibility, i.e., the ability to use glucose, glutamine, or fatty acids, seen upon syncytialization between the sexes with increased flexibility in female trophoblast suggesting a better ability to adapt to changes in nutrient supply.

Neuronal mitochondrial dysfunction in sporadic amyotrophic lateral sclerosis is developmentally regulated

Amyotrophic lateral sclerosis is an adult-onset neurodegenerative disorder characterized by loss of motor neurons. Mitochondria are essential for neuronal survival but the developmental timing and mechanistic importance of mitochondrial dysfunction in sporadic ALS (sALS) neurons is not fully understood. We used human induced pluripotent stem cells and generated a developmental timeline by differentiating sALS iPSCs to neural progenitors and to motor neurons and comparing mitochondrial parameters with familial ALS (fALS) and control cells at each developmental stage. We report that sALS and fALS motor neurons have elevated reactive oxygen species levels, depolarized mitochondria, impaired oxidative phosphorylation, ATP loss and defective mitochondrial protein import compared with control motor neurons. This phenotype develops with differentiation into motor neurons, the affected cell type in ALS, and does not occur in the parental undifferentiated sALS cells or sALS neural progenitors. Our work demonstrates a developmentally regulated unifying mitochondrial phenotype between patient derived sALS and fALS motor neurons. The occurrence of a unifying mitochondrial phenotype suggests that mitochondrial etiology known to SOD1-fALS may applicable to sALS. Furthermore, our findings suggest that disease-modifying treatments focused on rescue of mitochondrial function may benefit both sALS and fALS patients.

Generation of hiPSC-Derived Functional Dopaminergic Neurons in Alginate-Based 3D Culture

Human induced pluripotent stem cells (hiPSCs) represent an unlimited cell source for the generation of patient-specific dopaminergic (DA) neurons, overcoming the hurdle of restricted accessibility to disease-affected tissue for mechanistic studies on Parkinson's disease (PD). However, the complexity of the human brain is not fully recapitulated by existing monolayer culture methods. Neurons differentiated in a three dimensional (3D) in vitro culture system might better mimic the in vivo cellular environment for basic mechanistic studies and represent better predictors of drug responses in vivo. In this work we established a new in vitro cell culture system based on the microencapsulation of hiPSCs in small alginate/fibronectin beads and their differentiation to DA neurons. Optimization of hydrogel matrix concentrations and composition allowed a high viability of embedded hiPSCs. Neural differentiation competence and efficiency of DA neuronal generation were increased in the 3D cultures compared to a conventional 2D culture methodology. Additionally, electrophysiological parameters and metabolic switching profile confirmed increased functionality and an anticipated metabolic resetting of neurons grown in alginate scaffolds with respect to their 2D counterpart neurons. We also report long-term maintenance of neuronal cultures and preservation of the mature functional properties. Furthermore, our findings indicate that our 3D model system can recapitulate mitochondrial superoxide production as an important mitochondrial phenotype observed in neurons derived from PD patients, and that this phenotype might be detectable earlier during neuronal differentiation. Taken together, these results indicate that our alginate-based 3D culture system offers an advantageous strategy for the reliable and rapid derivation of mature and functional DA neurons from hiPSCs.

Regulatory roles of mitochondria and metabolism in neurogenesis

Neural stem cells (NSCs) undergo massive molecular and cellular changes during neuronal differentiation. These include mitochondria and metabolism remodelling, which were thought to be mostly permissive cues, but recent work indicates that they are causally linked to neurogenesis. Striking remodelling of mitochondria occurs right after mitosis of NSCs, which influences the postmitotic daughter cells towards self-renewal or differentiation. The transitioning to neuronal fate requires metabolic rewiring including increased oxidative phosphorylation activity, which drives transcriptional and epigenetic effects to influence cell fate. Mitochondria metabolic pathways also contribute in an essential way to the regulation of NSC proliferation and self-renewal. The influence of mitochondria and metabolism on neurogenesis is conserved from fly to human systems, but also displays striking differences linked to cell context or species. These new findings have important implications for our understanding of neurodevelopmental diseases and possibly human brain evolution.

Modelling Mitochondrial Disease in Human Pluripotent Stem Cells: What Have We Learned?

Mitochondrial diseases disrupt cellular energy production and are among the most complex group of inherited genetic disorders. Affecting approximately 1 in 5000 live births, they are both clinically and genetically heterogeneous, and can be highly tissue specific, but most often affect cell types with high energy demands in the brain, heart, and kidneys. There are currently no clinically validated treatment options available, despite several agents showing therapeutic promise. However, modelling these disorders is challenging as many non-human models of mitochondrial disease do not completely recapitulate human phenotypes for known disease genes. Additionally, access to disease-relevant cell or tissue types from patients is often limited. To overcome these difficulties, many groups have turned to human pluripotent stem cells (hPSCs) to model mitochondrial disease for both nuclear-DNA (nDNA) and mitochondrial-DNA (mtDNA) contexts. Leveraging the capacity of hPSCs to differentiate into clinically relevant cell types, these models permit both detailed investigation of cellular pathomechanisms and validation of promising treatment options. Here we catalogue hPSC models of mitochondrial disease that have been generated to date, summarise approaches and key outcomes of phenotypic profiling using these models, and discuss key criteria to guide future investigations using hPSC models of mitochondrial disease.

hiPSC-derived NSCs effectively promote the functional recovery of acute spinal cord injury in mice

Background

Spinal cord injury (SCI) is a common disease that results in motor and sensory disorders and even lifelong paralysis. The transplantation of stem cells, such as embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), or subsequently generated stem/progenitor cells, is predicted to be a promising treatment for SCI. In this study, we aimed to investigate effect of human iPSC-derived neural stem cells (hiPSC-NSCs) and umbilical cord-derived MSCs (huMSCs) in a mouse model of acute SCI.

Methods

Acute SCI mice model were established and were randomly treated as phosphate-buffered saline (PBS) (control group), repaired with 1 × 10⁵ hiPSC-NSCs (NSC group), and 1 × 10⁵ huMSCs (MSC group), respectively, in a total of 54 mice (n = 18 each). Hind limb motor function was evaluated in open-field tests using the Basso Mouse Scale (BMS) at days post-operation (dpo) 1, 3, 5, and 7 after spinal cord injury, and weekly thereafter. Spinal cord and serum samples were harvested at dpo 7, 14, and 21. Haematoxylin-eosin (H&E) staining and Masson staining were used to evaluate the morphological changes and fibrosis area. The differentiation of the transplanted cells in vivo was evaluated with immunohistochemical staining.

Results

The hiPSC-NSC-treated group presented a significantly smaller glial fibrillary acidic protein (GFAP) positive area than MSC-treated mice at all time points. Additionally, MSC-transplanted mice had a similar GFAP+ area to mice receiving PBS. At dpo 14, the immunostained hiPSC-NSCs were positive for SRY-related high-mobility-group (HMG)-box protein-2 (SOX2). Furthermore, the transplanted hiPSC-NSCs differentiated into GFAP-positive astrocytes and beta-III tubulin-positive neurons, whereas the transplanted huMSCs differentiated into GFAP-positive astrocytes. In addition, hiPSC-NSC transplantation reduced fibrosis formation and the inflammation level. Compared with the control or huMSC transplanted group, the group with transplantation of hiPSC-NSCs exhibited significantly improved behaviours, particularly limb coordination.

Conclusions

HiPSC-NSCs promote functional recovery in mice with acute SCI by replacing missing neurons and attenuating fibrosis, glial scar formation, and inflammation.

Graphical abstract

Melatonin inhibits cytosolic mitochondrial DNA-induced neuroinflammatory signaling in accelerated aging and neurodegeneration

Chronic inflammation is a pathologic feature of neurodegeneration and aging; however, the mechanism regulating this process is not understood. Melatonin, an endogenous free radical scavenger synthesized by neuronal mitochondria, decreases with aging and neurodegeneration. We proposed that insufficient melatonin levels impair mitochondrial homeostasis, resulting in mitochondrial DNA (mtDNA) release and activation of cytosolic DNA-mediated inflammatory response in neurons. We found increased mitochondrial oxidative stress and decreased mitochondrial membrane potential, with higher mtDNA release in brain and primary cerebro-cortical neurons of melatonin-deficient aralkylamine N-acetyltransferase (AANAT) knockout mice. Cytosolic mtDNA activated the cGAS/STING/IRF3 pathway, stimulating inflammatory cytokine generation. We found that Huntington's disease mice had increased mtDNA release, cGAS activation, and inflammation, all inhibited by exogenous melatonin. Thus, we demonstrated that cytosolic mtDNA activated the inflammatory response in aging and neurodegeneration, a process modulated by melatonin. Furthermore, our data suggest that AANAT knockout mice are a model of accelerated aging.

Down syndrome is an oxidative phosphorylation disorder

Down syndrome is the most common genomic disorder of intellectual disability and is caused by trisomy of chromosome 21. Several genes in this chromosome repress mitochondrial biogenesis. The goal of this study was to evaluate whether early overexpression of these genes may cause a prenatal impairment of oxidative phosphorylation negatively affecting neurogenesis. Reduction in the mitochondrial energy production and a lower mitochondrial function have been reported in diverse tissues or cell types, and also at any age, including early fetuses, suggesting that a defect in oxidative phosphorylation is an early and general event in Down syndrome individuals. Moreover, many of the medical conditions associated with Down syndrome are also frequently found in patients with oxidative phosphorylation disease. Several drugs that enhance mitochondrial biogenesis are nowadays available and some of them have been already tested in mouse models of Down syndrome restoring neurogenesis and cognitive defects. Because neurogenesis relies on a correct mitochondrial function and critical periods of brain development occur mainly in the prenatal and early neonatal stages, therapeutic approaches intended to improve oxidative phosphorylation should be provided in these periods.

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Several chromosome 21-encoded proteins repress mitochondrial biogenesis.

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These proteins are overexpressed in fetal brains of Down syndrome (DS) individuals.

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Oxidative phosphorylation function is essential for neurogenesis.

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Upregulation of these proteins adversely impact on neurogenesis.

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Prenatal therapy with drugs inhibiting these proteins would increase DS neurogenesis.

An NRF2 Perspective on Stem Cells and Ageing

Redox and metabolic mechanisms lie at the heart of stem cell survival and regenerative activity. NRF2 is a major transcriptional controller of cellular redox and metabolic homeostasis, which has also been implicated in ageing and lifespan regulation. However, NRF2's role in stem cells and their functioning with age is only just emerging. Here, focusing mainly on neural stem cells, which are core to adult brain plasticity and function, we review recent findings that identify NRF2 as a fundamental player in stem cell biology and ageing. We also discuss NRF2-based molecular programs that may govern stem cell state and function with age, and implications of this for age-related pathologies.

Resveratrol promotes the survival and neuronal differentiation of hypoxia-conditioned neuronal progenitor cells in rats with cerebral ischemia

Hypoxia conditioning could increase the survival of transplanted neuronal progenitor cells (NPCs) in rats with cerebral ischemia but could also hinder neuronal differentiation partly by suppressing mitochondrial metabolism. In this work, the mitochondrial metabolism of hypoxia-conditioned NPCs (hcNPCs) was upregulated via the additional administration of resveratrol, an herbal compound, to resolve the limitation of hypoxia conditioning on neuronal differentiation. Resveratrol was first applied during the in vitro neuronal differentiation of hcNPCs and concurrently promoted the differentiation, synaptogenesis, and functional development of neurons derived from hcNPCs and restored the mitochondrial metabolism. Furthermore, this herbal compound was used as an adjuvant during hcNPC transplantation in a photothrombotic stroke rat model. Resveratrol promoted neuronal differentiation and increased the long-term survival of transplanted hcNPCs. 18-fluorine fluorodeoxyglucose positron emission tomography and rotarod test showed that resveratrol and hcNPC transplantation synergistically improved the neurological and metabolic recovery of stroke rats. In conclusion, resveratrol promoted the neuronal differentiation and therapeutic efficiency of hcNPCs in stroke rats via restoring mitochondrial metabolism. This work suggested a novel approach to promote the clinical translation of NPC transplantation therapy.

Metabolic regulation of neurodifferentiation in the adult brain

Understanding the mechanisms behind neurodifferentiation in adults will be an important milestone in our quest to identify treatment strategies for cognitive disorders observed during our natural ageing or disease. It is now clear that the maturation of neural stem cells to neurones, fully integrated into neuronal circuits requires a complete remodelling of cellular metabolism, including switching the cellular energy source. Mitochondria are central for this transition and are increasingly seen as the regulatory hub in defining neural stem cell fate and neurodevelopment. This review explores our current knowledge of metabolism during adult neurodifferentiation.

Induced pluripotent stem cell (iPSC) line (HEBHMUi002-A) from a healthy female individual and neural differentiation

Induced pluripotent stem cells (iPSCs) can be used to generate different types of somatic cells in vitro, including neuronal cells. Here, a human iPSC line was generated from the peripheral blood mononuclear cells of a healthy 39-year-old individual. The resulting iPSCs were integration-free, maintained the normal karyotype, expressed pluripotency stem cell markers, and were demonstrated to be capable of differentiating into cells representative of the three embryonic germ layers. Furthermore, we showed that this iPSC line could be differentiated into neural stem cells. Taken together, this generated iPSC line could be useful to test multiple differentiation protocols, and also serve as a control for investigating drug development and disease mechanisms.

Uridine Prevents Negative Effects of OXPHOS Xenobiotics on Dopaminergic Neuronal Differentiation

Neuronal differentiation appears to be dependent on oxidative phosphorylation capacity. Several drugs inhibit oxidative phosphorylation and might be detrimental for neuronal differentiation. Some pregnant women take these medications during their first weeks of gestation when fetal nervous system is being developed. These treatments might have later negative consequences on the offspring's health. To analyze a potential negative effect of three widely used medications, we studied in vitro dopaminergic neuronal differentiation of cells exposed to pharmacologic concentrations of azidothymidine for acquired immune deficiency syndrome; linezolid for multidrug-resistant tuberculosis; and atovaquone for malaria. We also analyzed the dopaminergic neuronal differentiation in brains of fetuses from pregnant mice exposed to linezolid. The drugs reduced the in vitro oxidative phosphorylation capacity and dopaminergic neuronal differentiation. This differentiation process does not appear to be affected in the prenatally exposed fetus brain. Nevertheless, the global DNA methylation in fetal brain was significantly altered, perhaps linking an early exposure to a negative effect in older life. Uridine was able to prevent the negative effects on in vitro dopaminergic neuronal differentiation and on in vivo global DNA methylation. Uridine could be used as a protective agent against oxidative phosphorylation-inhibiting pharmaceuticals provided during pregnancy when dopaminergic neuronal differentiation is taking place.

The paradox of metabolism in quiescent stem cells

The shift between a proliferating and a nonproliferating state is associated with significant changes in metabolic needs. Proliferating cells tend to have higher metabolic rates, and their metabolic profiles facilitate biosynthesis, as compared to those of nondividing cells of the same sort. Recent studies have elucidated specific molecules that control metabolic changes while cells shift between proliferation and quiescence. Embryonic stem cells, which are rapidly proliferating, tend to have metabolic patterns that are similar to those of nonstem cells in a proliferative state. Moreover, although adult stem cells tend to be quiescent, their metabolic profiles have been reported in multiple organs to more closely resemble those of proliferating than those of nondividing cells in some respects. The findings raise questions about whether there are metabolic profiles that are required for stemness, and whether these profiles relate to the metabolic properties that may be required for quiescence. Here, we review the literature on how metabolism changes upon commitment to proliferation and compare the proliferating and nonproliferating metabolic states of differentiated cells and embryonic and adult stem cells.

Differentiation but not ALS mutations in FUS rewires motor neuron metabolism

Energy metabolism has been repeatedly linked to amyotrophic lateral sclerosis (ALS). Yet, motor neuron (MN) metabolism remains poorly studied and it is unknown if ALS MNs differ metabolically from healthy MNs. To address this question, we first performed a metabolic characterization of induced pluripotent stem cells (iPSCs) versus iPSC-derived MNs and subsequently compared MNs from ALS patients carrying FUS mutations to their CRISPR/Cas9-corrected counterparts. We discovered that human iPSCs undergo a lactate oxidation-fuelled prooxidative metabolic switch when they differentiate into functional MNs. Simultaneously, they rewire metabolic routes to import pyruvate into the TCA cycle in an energy substrate specific way. By comparing patient-derived MNs and their isogenic controls, we show that ALS-causing mutations in FUS did not affect glycolytic or mitochondrial energy metabolism of human MNs in vitro. These data show that metabolic dysfunction is not the underlying cause of the ALS-related phenotypes previously observed in these MNs.

Quiescence Entry, Maintenance, and Exit in Adult Stem Cells

Cells of unicellular and multicellular eukaryotes can respond to certain environmental cues by arresting the cell cycle and entering a reversible state of quiescence. Quiescent cells do not divide, but can re-enter the cell cycle and resume proliferation if exposed to some signals from the environment. Quiescent cells in mammals and humans include adult stem cells. These cells exhibit improved stress resistance and enhanced survival ability. In response to certain extrinsic signals, adult stem cells can self-renew by dividing asymmetrically. Such asymmetric divisions not only allow the maintenance of a population of quiescent cells, but also yield daughter progenitor cells. A multistep process of the controlled proliferation of these progenitor cells leads to the formation of one or more types of fully differentiated cells. An age-related decline in the ability of adult stem cells to balance quiescence maintenance and regulated proliferation has been implicated in many aging-associated diseases. In this review, we describe many traits shared by different types of quiescent adult stem cells. We discuss how these traits contribute to the quiescence, self-renewal, and proliferation of adult stem cells. We examine the cell-intrinsic mechanisms that allow establishing and sustaining the characteristic traits of adult stem cells, thereby regulating quiescence entry, maintenance, and exit.

The Stat3-Fam3a axis promotes muscle stem cell myogenic lineage progression by inducing mitochondrial respiration

Metabolic reprogramming is an active regulator of stem cell fate choices, and successful stem cell differentiation in different compartments requires the induction of oxidative phosphorylation. However, the mechanisms that promote mitochondrial respiration during stem cell differentiation are poorly understood. Here we demonstrate that Stat3 promotes muscle stem cell myogenic lineage progression by stimulating mitochondrial respiration in mice. We identify Fam3a, a cytokine-like protein, as a major Stat3 downstream effector in muscle stem cells. We demonstrate that Fam3a is required for muscle stem cell commitment and skeletal muscle development. We show that myogenic cells secrete Fam3a, and exposure of Stat3-ablated muscle stem cells to recombinant Fam3a in vitro and in vivo rescues their defects in mitochondrial respiration and myogenic commitment. Together, these findings indicate that Fam3a is a Stat3-regulated secreted factor that promotes muscle stem cell oxidative metabolism and differentiation, and suggests that Fam3a is a potential tool to modulate cell fate choices.

Mitochondrial contributions to neuronal development and function

Mitochondria are critical to tissues and organs characterized by high-energy demands, such as the nervous system. They provide essential energy and metabolites, and maintain Ca2+ balance, which is imperative for proper neuronal function and development. Emerging findings further underline the role of mitochondria in neurons. Technical advances in the last decades made it possible to investigate key mechanisms in neuronal development and the contribution of mitochondria therein. In this article, we discuss the latest findings relevant to the involvement of mitochondria in neuronal development, placing emphasis on mitochondrial metabolism and dynamics. In addition, we survey the role of mitochondrial energy metabolism and Ca2+ homeostasis in proper neuronal function, and the involvement of mitochondria in axon myelination.

Matrix Topography Regulates Synaptic Transmission at the Neuromuscular Junction

Recreation of a muscle that can be controlled by the nervous system would provide a major breakthrough for treatments of injury and diseases. However, the underlying basis of how neuron-muscle interfaces are formed is still not understood sufficiently. Here, it is hypothesized that substrate topography regulates neural innervation and synaptic transmission by mediating the cross-talk between neurons and muscles. This hypothesis is examined by differentiating neural stem cells on the myotubes, formed on the substrate with controlled groove width. The substrate with the groove width of 1600 nm, a similar size to the myofibril diameter, serves to produce larger and aligned myotubes than the flat substrate. The myotubes formed on the grooved substrate display increases in the acetylcholine receptor expression. Reciprocally, motor neuron progenitor cells differentiated from neural stem cells innervate the larger and aligned myotubes more actively than randomly oriented myotubes. As a consequence, mature and aligned myotubes respond to glutamate (i.e., an excitatory neurotransmitter) and curare (i.e., a neuromuscular antagonist) more rapidly and homogeneously than randomly oriented myotubes. The results of this study will be broadly useful for improving the quality of engineered muscle used in a series of applications including drug screening, regeneration therapies, and biological machinery assembly.

Modulation of mitochondrial respiration underpins neuronal differentiation enhanced by lutein

Lutein is a dietary carotenoid of particular nutritional interest as it is preferentially taken up by neural tissues. Often linked with beneficial effects on vision, a broader role for lutein in neuronal differentiation has emerged recently, although the underlying mechanisms for these effects are not yet clear. The purpose of this study was to investigate the effect of lutein on neuronal differentiation and explore the associated underpinning mechanisms. We found that lutein treatment enhanced the differentiation of SH-SY5Y cells, specifically increasing neuronal arborization and expression of the neuronal process filament protein microtubule-associated protein 2. This effect was mediated by the intracellular phosphoinositide-3-kinase (PI3K) signaling pathway. While PI3K activity is a known trigger of neuronal differentiation, more recently it has also been shown to modulate the metabolic state of cells. Our analysis of bioenergetics found that lutein treatment increased glucose consumption, rates of glycolysis and enhanced respiratory activity of mitochondrial complexes. Concomitantly, the generation of reactive oxygen species was increased (consistent with previous reports that reactive oxygen species promote neuronal differentiation), as well as the production of the key metabolic intermediate acetyl-CoA, an essential determinant of epigenetic status in the cell. We suggest that lutein-stimulated neuronal differentiation is mediated by PI3K-dependent modulation of mitochondrial respiration and signaling, and that the consequential metabolic shifts initiate epigenetically dependent transcriptomic reprogramming in support of this morphogenesis. These observations support the potential importance of micronutrients supplementation to neurogenesis, both during normal development and in regenerative repair.

Many Cells Make Life Work-Multicellularity in Stem Cell-Based Cardiac Disease Modelling

Cardiac disease causes 33% of deaths worldwide but our knowledge of disease progression is still very limited. In vitro models utilising and combining multiple, differentiated cell types have been used to recapitulate the range of myocardial microenvironments in an effort to delineate the mechanical, humoral, and electrical interactions that modulate the cardiac contractile function in health and the pathogenesis of human disease. However, due to limitations in isolating these cell types and changes in their structure and function in vitro, the field is now focused on the development and use of stem cell-derived cell types, most notably, human-induced pluripotent stem cell-derived CMs (hiPSC-CMs), in modelling the CM function in health and patient-specific diseases, allowing us to build on the findings from studies using animal and adult human CMs. It is becoming increasingly appreciated that communications between cardiomyocytes (CMs), the contractile cell of the heart, and the non-myocyte components of the heart not only regulate cardiac development and maintenance of health and adult CM functions, including the contractile state, but they also regulate remodelling in diseases, which may cause the chronic impairment of the contractile function of the myocardium, ultimately leading to heart failure. Within the myocardium, each CM is surrounded by an intricate network of cell types including endothelial cells, fibroblasts, vascular smooth muscle cells, sympathetic neurons, and resident macrophages, and the extracellular matrix (ECM), forming complex interactions, and models utilizing hiPSC-derived cell types offer a great opportunity to investigate these interactions further. In this review, we outline the historical and current state of disease modelling, focusing on the major milestones in the development of stem cell-derived cell types, and how this technology has contributed to our knowledge about the interactions between CMs and key non-myocyte components of the heart in health and disease, in particular, heart failure. Understanding where we stand in the field will be critical for stem cell-based applications, including the modelling of diseases that have complex multicellular dysfunctions.

Mitochondria in Developmental and Adult Neurogenesis

Generation of new neurons is a tightly regulated process that involves several intrinsic and extrinsic factors. Among them, a metabolic switch from glycolysis to oxidative phosphorylation, together with mitochondrial remodeling, has emerged as crucial actors of neurogenesis. However, although accumulating data raise the importance of mitochondrial morphology and function in neural stem cell proliferation and differentiation during development, information regarding the contribution of mitochondria to adult neurogenesis processes remains limited. In the present review, we discuss recent evidence covering the importance of mitochondrial morphology, function, and energy metabolism in the regulation of neuronal development and adult neurogenesis, and their impact on memory processes.

Prenatal exposure to oxidative phosphorylation xenobiotics and late-onset Parkinson disease

Late-onset Parkinson disease is a multifactorial and multietiological disorder, age being one of the factors implicated. Genetic and/or environmental factors, such as pesticides, can also be involved. Up to 80% of dopaminergic neurons of the substantia nigra are lost before motor features of the disorder begin to appear. In humans, these neurons are only formed a few weeks after fertilization. Therefore, prenatal exposure to pesticides or industrial chemicals during crucial steps of brain development might also alter their proliferation and differentiation. Oxidative phosphorylation is one of the metabolic pathways sensitive to environmental toxicants and it is crucial for neuronal differentiation. Many inhibitors of this biochemical pathway, frequently found as persistent organic pollutants, affect dopaminergic neurogenesis, promote the degeneration of these neurons and increase the risk of suffering late-onset Parkinson disease. Here, we discuss how an early, prenatal, exposure to these oxidative phosphorylation xenobiotics might trigger a late-onset, old age, Parkinson disease.

PPARs and Energy Metabolism Adaptation during Neurogenesis and Neuronal Maturation

Peroxisome proliferator activated receptors (PPARs) are a class of ligand-activated transcription factors, belonging to the superfamily of receptors for steroid and thyroid hormones, retinoids, and vitamin D. PPARs control the expression of several genes connected with carbohydrate and lipid metabolism, and it has been demonstrated that PPARs play important roles in determining neural stem cell (NSC) fate. Lipogenesis and aerobic glycolysis support the rapid proliferation during neurogenesis, and specific roles for PPARs in the control of different phases of neurogenesis have been demonstrated. Understanding the changes in metabolism during neuronal differentiation is important in the context of stem cell research, neurodegenerative diseases, and regenerative medicine. In this review, we will discuss pivotal evidence that supports the role of PPARs in energy metabolism alterations during neuronal maturation and neurodegenerative disorders.