Can pluripotent/multipotent stem cells reverse Parkinson's disease progression?

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by continuous and selective degeneration or death of dopamine neurons in the midbrain, leading to dysfunction of the nigrostriatal neural circuits. Current clinical treatments for PD include drug treatment and surgery, which provide short-term relief of symptoms but are associated with many side effects and cannot reverse the progression of PD. Pluripotent/multipotent stem cells possess a self-renewal capacity and the potential to differentiate into dopaminergic neurons. Transplantation of pluripotent/multipotent stem cells or dopaminergic neurons derived from these cells is a promising strategy for the complete repair of damaged neural circuits in PD. This article reviews and summarizes the current preclinical/clinical treatments for PD, their efficacies, and the advantages/disadvantages of various stem cells, including pluripotent and multipotent stem cells, to provide a detailed overview of how these cells can be applied in the treatment of PD, as well as the challenges and bottlenecks that need to be overcome in future translational studies.

Adipose-derived stem cells show hepatic differentiation potential and therapeutic effect in rats with acute liver failure.

Hepatocyte transplantation contributes to the repair of liver damage, but hepatocyte resources are limited, making it difficult for this to become a routine treatment. Previous studies have confirmed that mesenchymal stem cells (MSCs) can be induced to differentiate into hepatocyte-like cells (HLCs) by adding different cytokine combinations in vitro, and they then play some roles of hepatocytes. Our previous studies found that the differentiation ability of stem cells is closely related to the origin of the tissue. To identify the mesenchymal stem cells that are most suitable for hepatic differentiation and the treatment of liver failure, we use a three-phase induction process in which human adipose-derived stem cells (hADSCs) and umbilical cord mesenchymal stem cells (hUCMSCs) are induced to differentiate towards HLCs in vitro, and rats with acute liver failure (ALF) induced by D-gal are cured by MSCs and MSC-derived HLCs (MSCs-HLC), respectively. We find that hADSCs are stronger than hUCMSCs in hepatic differentiation ability, and they have a better curative effect when using hADSCs-HLC or jointly using hADSCs and hADSCs-HLC, which has positive significance for hepatocyte regeneration, recovery of liver function and reduction of systemic inflammatory reaction, finally improving the survival rate of rats with acute liver failure.

Cathepsin L-containing exosomes from α-synuclein-activated microglia induce neurotoxicity through the P2X7 receptor.

Uncontrolled microglial activation is pivotal to the pathogenesis of Parkinson's disease (PD), which can secrete Cathepsin L (CTSL) to affect the survival of neurons in the PD patients; however, the precise mechanism has yet to be determined. We demonstrated for the first time that CTSL was mostly released by exosomes derived from α-Syn-activated microglia, resulting in neuronal damage and death. The elevation of CTSL activity was blocked by GW4869, suggesting a critical role for exosomes in mediating CTSL release. Furthermore, the P2X7R/PI3K/AKT signalling pathway was identified as the underlying molecular mechanism since specific antagonists of this signalling pathway, P2X7R knockdown and exosome release inhibitors significantly reduced the injury to cultured mouse cortical neurons. Our study suggests that increased extracellular release of CTSL from α-Syn-activated microglia through exosomes amplifies and aggravates of the neurotoxic effect of microglia, implying that CTSL may be involved in a fresh mechanism of PD pathogenesis, and serve as a potential biomarker and a target for PD drug development.

Rebuilding hippocampus neural circuit with hADSC-derived neuron cells for treating ischemic stroke.

BACKGROUND: Human adipose-derived stem cells (hADSCs) have been demonstrated to be a promising autologous stem cell source for treating various neuronal diseases. Our study indicated that hADSCs could be induced into neuron-like cells in a stepwise manner that are characterized by the positive expression of MAP2, SYNAPSIN 1/2, NF-200, and vGLUT and electrophysiological activity. We first primed hADSCs into neuron-like cells (hADSC-NCs) and then intracerebrally transplanted them into MCAO reperfusion mice to further explore their in vivo survival, migration, integration, fate commitment and involvement in neural circuit rebuilding. RESULTS: The hADSC-NCs survived well and transformed into MAP2-positive, Iba1- or GFAP-negative cells in vivo while maintaining some proliferative ability, indicated by positive Ki67 staining after 4 weeks. hADSC-NCs could migrate to multiple brain regions, including the cortex, hippocampus, striatum, and hypothalamus, and further differentiate into mature neurons, as confirmed by action potential elicitation and postsynaptic currents. With the aid of a cell suicide system, hADSC-NCs were proven to have functionally integrated into the hippocampal memory circuit, where they contributed to spatial learning and memory rescue, as indicated by LTP improvement and subsequent GCV-induced relapse. In addition to infarction size shrinkage and movement improvement, MCAO-reperfused mice showed bidirectional immune modulation, including inhibition of the local proinflammatory factors IL-1α, IL-1ß, IL-2, MIP-1ß and promotion proinflammatory IP-10, MCP-1, and enhancement of the anti-inflammatory factors IL-15. CONCLUSION: Overall, hADSC-NCs used as an intermediate autologous cell source for treating stroke can rebuild hippocampus neuronal circuits through cell replacement.

ATM modulates subventricular zone neural stem cell maintenance and senescence through Notch signaling pathway.

Ataxia telangiectasia mutated (ATM) plays an essential role in DNA damage response and the maintenance of genomic stability. However, the role of ATM in regulating the function of adult neural stem cells (NSCs) remains unclear. Here we report that ATM deficiency led to accumulated DNA damage and decreased DNA damage repair capacity in neural progenitor cells. Moreover, we observed ATM ablation lead to the short-term increase of proliferation of neural progenitor cells, resulting in the depletion of the NSC pool over time, and this loss of NSC quiescence resulted in accelerated cell senescence. We further apply RNA sequencing to unravel that ATM knockout significantly affected Notch signaling pathway, furthermore, notch activation inhibit the abnormal increased proliferation of ATM-/- NSCs. Taken together, these findings indicate that ATM can serve as a key regulator for the normal function of adult NSCs by maintaining their stemness and preventing cellular senescence primarily through Notch signaling pathway.

Roles of Exosomes from Mesenchymal Stem Cells in Treating Osteoarthritis.

Exosomes are small extracellular vesicles (EVs) with a diameter of 50-150 nm that play important roles in cell-to-cell communication through transportation of proteins, microRNAs, lncRNAs, and mRNAs. Some components, such as miRNAs, have been proven to be involved in inflammation regulation. Osteoarthritis (OA) is a progressive disease resulting in articular cartilage degeneration and subchondral bone deficiency. Complicated relationships between the breakdown of extracellular matrix and inflammation make it difficult to recover thoroughly. Current studies reported that exosomes secreted by mesenchymal stem cells (MSCs) can change disease evolution and protect the cartilage matrix in OA. In addition, exosomes obtained from human adipose derived stem cells downregulate inflammation and oxidative stress, which might mediate antisenescence in OA. The goal of this review is to describe and summarize the role of mesenchymal stem cell (MSC)-derived exosomes in OA, focusing on their potential mechanism and possible therapeutic strategies.

miR-29a Promotes the Neurite Outgrowth of Rat Neural Stem Cells by Targeting Extracellular Matrix to Repair Brain Injury.

Neural stem cells (NSCs) can generate new neurons to repair brain injury and central nervous system disease by promoting neural regeneration. MicroRNAs (miRNAs) involve in neural development, brain damage, and neurological diseases repair. Recent reports show that several miRNAs express in NSCs and are important to neurogenesis. Neurites play a key role in NSC-related neurogenesis. However, the mechanism of NSC neurite generation is rarely studied. We surprisingly noticed that the neurites increased after bone morphogenetic protein (BMP) treatment in rat NSCs. This process was accompanied by the dynamic change of miRNA-29. Then we discovered that miR-29a regulated neural neurites in rat hippocampus NSCs. Overexpression of miR-29a reduced the cell soma area and promoted the neurite outgrowth of NSCs. Cell soma area became small, whereas the number of neurite increased. Moreover, neurite complexity increased dramatically, with more primary and secondary branches after miR-29a overexpression. In addition, miR-29a overexpression still maintained the stemness of NSCs. Besides, we identified that miR-29a can promote the neurite outgrowth by targeting extracellular matrix-related genes like Fibrillin 1 (Fbn1), Follistatin-like 1 (Fstl1), and laminin subunit gamma 2 (Lamc2). These findings may provide a novel role of miR-29a to regulate neurite outgrowth and development of NSCs. We also offered a possible theoretical basis to the migration mechanism of NSCs in brain development and damage repair.

Corrigendum: The Challenge of the Pathogenesis of Parkinson's Disease: Is Autoimmunity the Culprit?

[This corrects the article DOI: 10.3389/fimmu.2018.02047.].

Differentiation of human adipose-derived stem cells into neuron/motoneuron-like cells for cell replacement therapy of spinal cord injury.

Human adipose-derived stem cells (hADSCs) are increasingly presumed to be a prospective stem cell source for cell replacement therapy in various degenerative and/or traumatic diseases. The potential of trans-differentiating hADSCs into motor neuron cells indisputably provides an alternative way for spinal cord injury (SCI) treatment. In the present study, a stepwise and efficient hADSC trans-differentiation protocol with retinoic acid (RA), sonic hedgehog (SHH), and neurotrophic factors were developed. With this protocol hADSCs could be converted into electrophysiologically active motoneuron-like cells (hADSC-MNs), which expressed both a cohort of pan neuronal markers and motor neuron specific markers. Moreover, after being primed for neuronal differentiation with RA/SHH, hADSCs were transplanted into SCI mouse model and they survived, migrated, and integrated into injured site and led to partial functional recovery of SCI mice. When ablating the transplanted hADSC-MNs harboring HSV-TK-mCherry overexpression system with antivirial Ganciclovir (GCV), functional relapse was detected by motor-evoked potential (MEP) and BMS assays, implying that transplanted hADSC-MNs participated in rebuilding the neural circuits, which was further confirmed by retrograde neuronal tracing system (WGA). GFP-labeled hADSC-MNs were subjected to whole-cell patch-clamp recording in acute spinal cord slice preparation and both action potentials and synaptic activities were recorded, which further confirmed that those pre-conditioned hADSCs indeed became functionally active neurons in vivo. As well, transplanted hADSC-MNs largely prevented the formation of injury-induced cavities and exerted obvious immune-suppression effect as revealed by preventing astrocyte reactivation and favoring the secretion of a spectrum of anti-inflammatory cytokines and chemokines. Our work suggests that hADSCs can be readily transformed into MNs in vitro, and stay viable in spinal cord of the SCI mouse and exert multi-therapeutic effects by rebuilding the broken circuitry and optimizing the microenvironment through immunosuppression.

Correction to: Human adipose-derived stem cells partially rescue the stroke syndromes by promoting spatial learning and memory in mouse middle cerebral artery occlusion model.

The original article [1] contains an accidental omission in the Acknowledgements.

Stress-induced precocious aging in PD-patient iPSC-derived NSCs may underlie the pathophysiology of Parkinson's disease.

Parkinson's disease (PD) is an aging-related degenerative disorder arisen from the loss of dopaminergic neurons in substantia nigra. Although many genetic mutations have been implicated to be genetically linked to PD, the low incidence of familial PD carried with mutations suggests that there must be other factors such as oxidative stress, mitochondrial dysfunction, accumulation of misfolded proteins, and enhanced inflammation, which are contributable to the pathophysiology of PD. The major efforts of current research have been devoted to unravel the toxic effect of multiple factors, which directly cause the degeneration of dopaminergic neurons in adulthood. Until recently, several studies have demonstrated that NSCs had compromised proliferation and differentiation capacity in PD animal models or PD patient-derived iPS models, suggesting that the pathology of PD may be rooted in some cellular aberrations at early developmental stage but the mechanism remains to be elusive. Based on the early-onset PD patient-specific iPSCs, we found that PD-patient iPSC-derived NSCs were more susceptible to stress and became functionally compromised by radiation or oxidative insults. We further unraveled that stress-induced SIRT1 downregulation leading to autophagic dysfunction, which were responsible for these deficits in PD-NSCs. Mechanistically, we demonstrated that stress-induced activation of p38 MAPK suppressed SIRT1 expression, which in turn augmented the acetylation of multiple ATG proteins of autophagic complex and eventually led to autophagic deficits. Our studies suggest that early developmental deficits may, at least partially, contribute to the pathology of PD and provide a new avenue for developing better therapeutic interventions to PD.

Astrocytic miR-324-5p is essential for synaptic formation by suppressing the secretion of CCL5 from astrocytes.

There is accumulating evidence that astrocytes play an important role in synaptic formation, plasticity, and pruning. Dicer and the fine-tuning of microRNA (miRNA) network are important for maintaining the normal functions of central nervous system and dysregulation of miRNAs is implicated in neurological disorders. However, little is known about the role of Dicer and miRNAs of astrocytes in the homeostasis of synapse as well as its plasticity. By selectively deleting Dicer in postnatal astrocytes, Dicer-deficient mice exhibited reactive astrogliosis and deficits in dendritic spine formation. Astrocyte-conditioned medium (ACM) collected from Dicer-null astrocytes caused synapse degeneration in cultured primary neurons. The expression of chemokine ligand 5 (CCL5) elevated in Dicer-deleted astrocytes which led to the significant augmentation of secreted CCL5 in ACM. In neurons treated with Dicer KO-ACM, CCL5 supplementation inhibited MAPK/CREB signaling pathway and exacerbated the synaptic formation deficiency, while CCL5 knockdown partially rescued the synapse degeneration. Moreover, we validated CCL5 as miR-324-5p targeted gene. ACM collected from miR-324-5p antagomir-transfected astrocytes mimicked the effect of CCL5 treatment on inhibiting synapse formation and MAPK/CREB signaling in Dicer KO-ACM-cocultured neurons. Furthermore, decreased miR-324-5p expression and elevated CCL5 expression were observed in the brain of aging mice. Our work reveals the non-cell-autonomous roles of astroglial miRNAs in regulation of astrocytic secretory milieu and neuronal synaptogenesis, implicating the loss or misregulation of astroglial miRNA network may contribute to neuroinflammation, neurodegeneration, and aging.

Rapamycin Enhances Mitophagy and Attenuates Apoptosis After Spinal Ischemia-Reperfusion Injury.

The spinal cord is extremely vulnerable to ischemia-reperfusion (I/R) injury, and the mitochondrion is the most crucial interventional target. Rapamycin can promote autophagy and exert neuroprotective effects in several diseases of the central nervous system. However, the impact of rapamycin via modulating mitophagy and apoptosis after spinal cord ischemia-reperfusion injury remains unclear. This study was undertaken to investigate the potential role of rapamycin in modulating mitophagy and mitochondria-dependent apoptosis using the spinal cord ischemia-reperfusion injury (SCIRI) mouse model. We found that rapamycin significantly (p < 0.05) enhanced mitophagy by increasing the translocation of p62 and Parkin to the damaged mitochondria in the mouse spinal cord injury model. At the same time, rapamycin significantly (p < 0.05) decreased mitochondrial apoptosis related protein (Apaf-1, Caspase-3, Caspase-9) expression by inhibiting Bax translocation to the mitochondria and the release of the cytochrome c from the mitochondria. After 24 h following SCIRI, rapamycin treatment reduced the TUNEL+ cells in the spinal cord ischemic tissue and improved the locomotor function in these mice. Our results therefore demonstrate that rapamycin can improve the locomotor function by promoting mitophagy and attenuating SCIRI -induced apoptosis, indicating its potential therapeutic application in a spinal cord injury.

The Challenge of the Pathogenesis of Parkinson's Disease: Is Autoimmunity the Culprit?

The role of autoimmunity in Parkinson's disease (PD), as one of the most popular research subjects, has been intensively investigated in recent years. Although the ultimate cause of PD is unknown, one major area of interest remains identifying new therapeutic targets and options for patients suffering from PD. Herein, we present a comprehensive review of the impacts of autoimmunity in neurodegenerative diseases, especially PD, and we have composed a logical argument to substantiate that autoimmunity is actively involved in the pathogenesis of PD through several proteins, including α-synuclein, DJ-1, PINK1, and Parkin, as well as immune cells, such as dendritic cells, microglia, T cells, and B cells. Furthermore, a detailed analysis of the relevance of autoimmunity to the clinical symptoms of PD provides strong evidence for the close correlation of autoimmunity with PD. In addition, the previously identified relationships between other autoimmune diseases and PD help us to better understand the disease pattern, laying the foundation for new therapeutic solutions to PD. In summary, this review aims to integrate and present currently available data to clarify the pathogenesis of PD and discuss some controversial but innovative research perspectives on the involvement of autoimmunity in PD, as well as possible novel diagnostic methods and treatments based on autoimmunity targets.

Extracellular Vesicles Secreted by Human Adipose-derived Stem Cells (hASCs) Improve Survival Rate of Rats with Acute Liver Failure by Releasing lncRNA H19.

It has previously been reported that human adipose-derived stem cells (hASCs) can promote the regeneration of damaged tissues in rats with liver failure through a 'paracrine effect'. Here we demonstrate a therapeutic effect of hASCs derived Extracellular Vesicles (EVs) on rat models with acute liver failure, as shown by the improvement of the survival rate by >70% compared to controls. Gene sequencing of rat liver revealed an increase in human long-chain non-coding RNA (lncRNA) H19 after hASC-derived EVs transplantation. When the H19 coding sequence was silenced in hASCs and EVs were then collected for treatment of rats with liver failure, we saw a decrease in the survival rate to 40%, compared to treatment with EVs generated from non-silenced hASCs. These data indicate that lncRNA H19 may be a potential therapeutic target for the treatment of liver failure.

SIRT1 Involved in the Regulation of Alternative Splicing Affects the DNA Damage Response in Neural Stem Cells.

BACKGROUND/AIMS: Alternative splicing and DNA damage exhibit cross-regulation, with not only DNA damage inducing changes in alternative splicing, but alternative splicing itself possibly modulating the DNA damage response (DDR). Sirt1, a prominent anti-aging player, plays pivotal roles in the DDR. However, few studies have examined alternative splicing with DNA damage in neural stem cells (NSCs) and, in essence, nothing is known about whether SIRT1 regulates alternative splicing. Hence, we investigated the potential involvement of Sirt1-mediated alternative splicing in the NSC DDR. METHODS: Genome-wide alternative splicing profiling was performed upon DNA damage induction and SIRT1 deletion. RESULTS: DNA damage caused genome-wide changes in alternative splicing in adult NSCs and Sirt1 deficiency dramatically altered DDR-related alternative splicing. In particular, extensive alternative splicing changes in DDR-related processes such as cell cycle control and DNA damage repair were observed; these processes were dramatically influenced by Sirt1 deficiency. Phenotypically, Sirt1 deficiency altered the proliferation and DNA repair of adult NSCs, possibly by regulating alternative splicing. CONCLUSION: SIRT1 helps to regulate alternative splicing, which itself affects the DDR of NSCs. Our findings provide novel insight into the mechanisms underlying the DDR in stem cells.

MicroRNA­138­5p regulates neural stem cell proliferation and differentiation in vitro by targeting TRIP6 expression.

Research on neural stem cells (NSCs) has recently focused on microRNAs (miRNAs), a class of small non­coding RNAs that have crucial roles in regulating NSC proliferation and differentiation. In the present study, a quantitative­polymerase chain reaction assay revealed that the expression of miRNA (miR)­138­5p was significantly decreased during neural differentiation of NSCs in vitro. Overexpression of miR­138­5p reduced NSC proliferation and increased NSC differentiation. Furthermore, suppression of miR­138­5p via transfection with a miRNA inhibitor enhanced NSC proliferation and attenuated NSC differentiation. Additionally, expression of thyroid hormone receptor interacting protein 6 (TRIP6), a critical regulator of NSCs, was negatively correlated with the miR­138­5p level. A luciferase assay demonstrated that miR­138­5p regulate TRIP6 by directly binding the 3'­untranslated region of the mRNA. Additionally, upregulation of TRIP6 rescued the NSC proliferation deficiency induced by miR­138­5p and abolished miR­138­5p­promoted NSCs differentiation. By contrast, downregulation of TRIP6 produced the opposite effect on proliferation and differentiation of NSCs transfected with anti­miR­138­5p. Taken together, the data suggest that miR­138­5p regulates NSCs proliferation and differentiation, and may be useful in developing novel treatments for neurological disorders via manipulation of miR­138­5p in NSCs.

Human adipose-derived stem cells partially rescue the stroke syndromes by promoting spatial learning and memory in mouse middle cerebral artery occlusion model.

INTRODUCTION: Growing evidence has brought stem cell therapy to the forefront as new promising approaches towards stroke treatment. Of all candidate seeding cells, adipose-derived stem cells (ADSCs) are considered as one of the most appropriate for stroke treatment. However, previous experimental data could not reach to an agreement on the efficacy of ADSC transplantation for treating stroke in vivo as well as its mechanism which hinders their further clinical translational application. METHODS: To explore their in vivo mechanism of hADSC administration on neurological injury, hADSC were labeled with Enhanced Green Fluorescence Protein expressing FG12 lentivirus and injected into MCAO mouse infarct area by in situ way. Neurological function was evaluated by Rogers Scaling System and their spatial learning and memory was determined by Morris Test. 2,3,5-triphenyltetrazolium chloride was carried out to compare the infarct area among groups. Histoimmunostaining was used to track the injected hADSCs for their in vivo migration, transdifferentiation and integration with the endogenous neuronal circuitry. To better address the underlying rescuing mechanism, qRT-PCR was performed on neural markers of MBP, MAP2, GFAP, microglia marker of Iba1. RESULTS: It was found that hADSCs could promote both spatial learning and memory of MCAO mice. Co-localization of GFP and MAP2 were found in the whole cortex with significantly (P<0.01) higher percentage at the contralateral cortex compared with the ipsilateral cortex. Low percentage of GFP and GFAP co-localized cells were found at whole cortex. Meanwhile, Iba1(+) microglia and GFAP(+) astrocyte cells were significantly (P<0.05) suppressed by hADSC injection. CONCLUSIONS: hADSCs could transdifferentiate into neuron like cells (MAP2(+)) in vivo and probably used as seeding cells for replacement based stem cell therapy of stroke. Also, significant immunomodulation was found. Meanwhile hADSCs could significantly protect the endogenous neuron survival. This study demonstrated that hADSC intervention with MCAO mice could apparently ameliorate stroke symptoms by direct cell replacement, enhanced immnunosuppression and increasing the viability of endogenous neurons.

Differentiation of human adipose-derived stem cells into neuron-like cells which are compatible with photocurable three-dimensional scaffolds.

Multipotent human adipose-derived stromal/stem cells (hADSCs) hold a great promise for cell-based therapy for many devastating human diseases, such as spinal cord injury and stroke. If exogenous hADSCs can be cultured in a three-dimensional (3D) scaffold with effective proliferation and differentiation capacity, it will better mimic the in vivo environment, which will have profound impact on the therapeutic application of hADSCs. In this study, a group of elastic-dominant, porous bioscaffolds from photocurable chitosan and gelatin were fabricated and proven to be biocompatible with both hADSCs and hADSC-derived neuron-like cells (hADSC-NLCs) in vitro. The identity of harvested hADSCs was confirmed by their positive immunostaining of mesenchymal stem cell surface markers, CD29, CD44, and CD105, and also positive expression of stem markers, Sox-2, Oct-4, c-Myc, Nanog, and Klf4. Their multipotency was further confirmed by trilineage differentiation of hADSCs toward adipocyte, osteoblast, and chondrocyte. It was found that hADSCs could be conditioned to differentiate into neurons in vitro as determined by immunostaining the markers of Tuj1, MAP2, NeuN, and Synapsin. The hADSCs and hADSC-NLCs were proven to be biocompatible with 3D scaffold, which actually facilitated the proliferation and differentiation of hADSCs in vitro, by MTT assay and their neuronal gene expression profiling. Moreover, hADSC-NLCs, which were mixed with 3D scaffold and transplanted into traumatic brain injury mouse model, survived in vivo and led to the better repair of the damaged brain area. The immunohistochemical studies revealed that 3D scaffold indeed improved the viability of transplanted cells, their ability to incorporate into the in vivo neural circuit, and their capacity for tissue repair. This study indicates that hADSCs would have great therapeutic application potential as seeding cells for in vivo transplantation to treat various neurological diseases when co-applied with porous chitosan/gelatin bioscaffolds.