Mitomycin-C treatment during differentiation of induced pluripotent stem cell-derived dopamine neurons reduces proliferation without compromising survival or function in vivo

Lineage tracing of stem cell-derived dopamine grafts in a Parkinson's model reveals shared origin of all graft-derived cells

Stem cell therapies for Parkinson's disease are at an exciting time of development, and several clinical trials have recently been initiated. Human pluripotent stem cells are differentiated into transplantable dopamine (DA) progenitors which are proliferative at the time of grafting and undergo terminal differentiation and maturation in vivo. While the progenitors are homogeneous at the time of transplantation, they give rise to heterogeneous grafts composed not only of therapeutic DA neurons but also of other mature cell types. The mechanisms for graft diversification are unclear. We used single-nucleus RNA-seq and ATAC-seq to profile DA progenitors before transplantation combined with molecular barcode-based tracing to determine origin and shared lineages of the mature cell types in the grafts. Our data demonstrate that astrocytes, vascular leptomeningeal cells, and DA neurons are the main component of the DAergic grafts, originating from a common progenitor that is tripotent at the time of transplantation.

The Neuroanatomy of Induced Pluripotent Stem Cells: In Vitro Models of Subcortical Nuclei in Neurodegenerative Disorders

Neuromodulatory subcortical systems (NSSs) are monoaminergic and cholinergic neuronal groups that are markedly and precociously involved in the pathogenesis of many neurodegenerative disorders (NDDs), including Parkinson's and Alzheimer's diseases. In humans, although many tools have been developed to infer information on these nuclei, encompassing neuroimaging and neurophysiological methods, a detailed and specific direct evaluation of their cellular features in vivo has been difficult to obtain until recent years. The development of induced pluripotent stem cell (iPSC) models has allowed research to deeply delve into the cellular and molecular biology of NSS neurons. In fact, iPSCs can be produced easily and non-invasively from patients' fibroblasts or circulating blood monocytes, by de-differentiating those cells using specific protocols, and then be re-differentiated towards neural phenotypes, which may reproduce the specific features of the correspondent brain neurons (including NSS ones) from the same patient. In this review, we summarized findings obtained in the field of NDDs using iPSCs, with the aim to understand how reliably these might represent in vitro models of NSS. We found that most of the current literature in the field of iPSCs and NSSs in NDDs has focused on midbrain dopaminergic neurons in Parkinson's disease, providing interesting results on cellular pathophysiology and even leading to the first human autologous transplantation. Differentiation protocols for noradrenergic, cholinergic, and serotoninergic neurons have also been recently defined and published. Thus, it might be expected that in the near future, this approach could extend to other NSSs and other NDDs.

Comparative study of enriched dopaminergic neurons from siblings with Gaucher disease discordant for parkinsonism

Inducible pluripotent stem cells (iPSCs) derived from patient samples have significantly enhanced our ability to model neurological diseases. Comparative studies of dopaminergic (DA) neurons differentiated from iPSCs derived from siblings with Gaucher disease discordant for parkinsonism provides a valuable avenue to explore genetic modifiers contributing to GBA1 -associated parkinsonism in disease-relevant cells. However, such studies are often complicated by the inherent heterogeneity in differentiation efficiency among iPSC lines derived from different individuals. To address this technical challenge, we devised a selection strategy to enrich dopaminergic (DA) neurons expressing tyrosine hydroxylase (TH). A neomycin resistance gene (neo) was inserted at the C-terminus of the TH gene following a T2A self-cleavage peptide, placing its expression under the control of the TH promoter. This allows for TH+ DA neuron enrichment through geneticin selection. This method enabled us to generate comparable, high-purity DA neuron cultures from iPSC lines derived from three sisters that we followed for over a decade: one sibling is a healthy individual, and the other two have Gaucher disease (GD) with GBA1 genotype N370S/c.203delC+R257X (p.N409S/c.203delC+p.R296X). Notably, the younger sister with GD later developed Parkinson disease (PD). A comprehensive analysis of these high-purity DA neurons revealed that although GD DA neurons exhibited decreased levels of glucocerebrosidase (GCase), there was no substantial difference in GCase protein levels or lipid substrate accumulation between DA neurons from the GD and GD/PD sisters, suggesting that the PD discordance is related to of other genetic modifiers.

Unravelling the Parkinson's puzzle, from medications and surgery to stem cells and genes: a comprehensive review of current and future management strategies

Parkinson's disease (PD) is a neurodegenerative disorder, prevalent in the elderly population. Neuropathological hallmarks of PD include loss of dopaminergic cells in the nigro-striatal pathway and deposition of alpha-synuclein protein in the neurons and synaptic terminals, which lead to a complex presentation of motor and non-motor symptoms. This review focuses on various aspects of PD, from clinical diagnosis to currently accepted treatment options, such as pharmacological management through dopamine replacement and surgical techniques such as deep brain stimulation (DBS). The review discusses in detail the potential of emerging stem cell-based therapies and gene therapies to be adopted as a cure, in contrast to the present symptomatic treatment in PD. The potential sources of stem cells for autologous and allogeneic stem cell therapy have been discussed, along with the progress evaluation of pre-clinical and clinical trials. Even though recent techniques hold great potential to improve the lives of PD patients, we present the importance of addressing the safety, efficacy, ethical, cost, and regulatory concerns before scaling them to clinical use.

Molecular mechanisms regulating wound repair: Evidence for paracrine signaling from corneal epithelial cells to fibroblasts and immune cells following transient epithelial cell treatment with Mitomycin C

In this paper, we use RNAseq to identify senescence and phagocytosis as key factors to understanding how mitomyin C (MMC) stimulates regenerative wound repair. We use conditioned media (CM) from untreated (CMC) and MMC treated (CMM) human and mouse corneal epithelial cells to show that corneal epithelial cells indirectly exposed to MMC secrete elevated levels of immunomodulatory proteins including IL-1α and TGFβ1 compared to cells exposed to CMC. These factors increase epithelial and macrophage phagocytosis and promote ECM turnover. IL-1α supplementation can increase phagocytosis in control epithelial cells and attenuate TGFβ1 induced αSMA expression by corneal fibroblasts. Yet, we show that epithelial cell CM contains factors besides IL-1α that regulate phagocytosis and αSMA expression by fibroblasts. Exposure to CMM also impacts the activation of bone marrow derived dendritic cells and their ability to present antigen. These in vitro studies show how a brief exposure to MMC induces corneal epithelial cells to release proteins and other factors that function in a paracrine way to enhance debris removal and enlist resident epithelial and immune cells as well as stromal fibroblasts to support regenerative and not fibrotic wound healing.

Clinical considerations in Parkinson's disease cell therapy

Cell replacement therapy is an area of increasing interest for treating Parkinson's disease (PD). However, to become a clinically practical option for PD patients, it must first overcome significant barriers, including establishment of safe and standardized surgical procedures, determination of appropriate perioperative medication regimens, demonstration of long-term graft survival and incorporation, and standardized, clinically meaningful follow-up measures. In this review, we will describe the current status of cell therapy for PD with special attention to these critical requirements, to define guideposts on the road to bring the benefit of this therapy to the Parkinson's clinic.

Optimizing maturity and dose of iPSC-derived dopamine progenitor cell therapy for Parkinson's disease

In pursuit of treating Parkinson’s disease with cell replacement therapy, differentiated induced pluripotent stem cells (iPSC) are an ideal source of midbrain dopaminergic (mDA) cells. We previously established a protocol for differentiating iPSC-derived post-mitotic mDA neurons capable of reversing 6-hydroxydopamine-induced hemiparkinsonism in rats. In the present study, we transitioned the iPSC starting material and defined an adapted differentiation protocol for further translation into a clinical cell transplantation therapy. We examined the effects of cellular maturity on survival and efficacy of the transplants by engrafting mDA progenitors (cryopreserved at 17 days of differentiation, D17), immature neurons (D24), and post-mitotic neurons (D37) into immunocompromised hemiparkinsonian rats. We found that D17 progenitors were markedly superior to immature D24 or mature D37 neurons in terms of survival, fiber outgrowth and effects on motor deficits. Intranigral engraftment to the ventral midbrain demonstrated that D17 cells had a greater capacity than D24 cells to innervate over long distance to forebrain structures, including the striatum. When D17 cells were assessed across a wide dose range (7,500-450,000 injected cells per striatum), there was a clear dose response with regards to numbers of surviving neurons, innervation, and functional recovery. Importantly, although these grafts were derived from iPSCs, we did not observe teratoma formation or significant outgrowth of other cells in any animal. These data support the concept that human iPSC-derived D17 mDA progenitors are suitable for clinical development with the aim of transplantation trials in patients with Parkinson’s disease.

Research progress on antineoplastic, antibacterial, and anti-inflammatory activities of seven-membered heterocyclic derivatives

Abstract:

Seven-membered heterocyclic compounds are important drug scaffolds, because of their unique chemical structures. They widely exist in natural products and show a variety of biological activities. They have commonly been used in central nervous system drugs in the past 30 years. In the past decade, there are many studies on the activities of antitumor, antibacterial, etc. Herein, we summarize the research advances in different kinds of seven-membered heterocyclic compounds containing nitrogen, oxygen, and sulfur heteroatoms with antitumor, antisepsis, and anti-inflammation activities in the past ten years, which is expected to be beneficial to the development and design of novel drugs for the corresponding indications.

Mitomycin-Treated Endothelial and Smooth Muscle Cells Suitable for Safe Tissue Engineering Approaches

In our previous study, we showed that discarded cardiac tissue from the right atrial appendage and right ventricular myocardium is an available source of functional endothelial and smooth muscle cells for regenerative medicine and tissue engineering. In the study, we aimed to find out what benefits are given by vascular cells from cardiac explants used for seeding on vascular patches engrafted to repair vascular defects in vivo. Additionally, to make the application of these cells safer in regenerative medicine we tested an in vitro approach that arrested mitotic division to avoid the potential tumorigenic effect of dividing cells. A tissue-engineered construction in the form of a patch based on a polycaprolactone-gelatin scaffold and seeded with endothelial and smooth muscle cells was implanted into the abdominal aorta of immunodeficient SCID mice. Aortic patency was assessed using ultrasound, MRI, immunohistochemical and histological staining. Endothelial and smooth muscle cells were treated with mitomycin C at a therapeutic concentration of 10 μg/ml for 2 h with subsequent analysis of cell proliferation and function. The absence of the tumorigenic effect of mitomycin C-treated cells, as well as their angiogenic potential, was examined by injecting them into immunodeficient mice. Cell-containing patches engrafted in the abdominal aorta of immunodeficient mice form the vessel wall loaded with the appropriate cells and extracellular matrix, and do not interfere with normal patency. Endothelial and smooth muscle cells treated with mitomycin C show no tumorigenic effect in the SCID immunodeficient mouse model. During in vitro experiments, we have shown that treatment with mitomycin C does not lead to a decrease in cell viability. Despite the absence of proliferation, mitomycin C-treated vascular cells retain specific cell markers, produce specific extracellular matrix, and demonstrate the ability to stimulate angiogenesis in vivo. We pioneered an approach to arresting cell division with mitomycin C in endothelial and smooth muscle cells from cardiac explant, which prevents the risk of malignancy from dividing cells in vascular surgery. We believe that this approach to the fabrication of tissue-engineered constructs based on mitotically inactivated cells from waste postoperative material may be valuable to bring closer the development of safe cell products for regenerative medicine.

Emerging Therapeutic Strategies for Parkinson’s Disease and Future Prospects: A 2021 Update

Parkinson’s disease (PD) is a neurodegenerative disorder pathologically distinguished by degeneration of dopaminergic neurons in the substantia nigra pars compacta. Muscle rigidity, tremor, and bradykinesia are all clinical motor hallmarks of PD. Several pathways have been implicated in PD etiology, including mitochondrial dysfunction, impaired protein clearance, and neuroinflammation, but how these factors interact remains incompletely understood. Although many breakthroughs in PD therapy have been accomplished, there is currently no cure for PD, only trials to alleviate the related motor symptoms. To reduce or stop the clinical progression and mobility impairment, a disease-modifying approach that can directly target the etiology rather than offering symptomatic alleviation remains a major unmet clinical need in the management of PD. In this review, we briefly introduce current treatments and pathophysiology of PD. In addition, we address the novel innovative therapeutic targets for PD therapy, including α-synuclein, autophagy, neurodegeneration, neuroinflammation, and others. Several immunomodulatory approaches and stem cell research currently in clinical trials with PD patients are also discussed. Moreover, preclinical studies and clinical trials evaluating the efficacy of novel and repurposed therapeutic agents and their pragmatic applications with encouraging outcomes are summarized. Finally, molecular biomarkers under active investigation are presented as potentially valuable tools for early PD diagnosis.

Uncovering specificity of endogenous TAU aggregation in a human iPSC-neuron TAU seeding model

Tau pathobiology has emerged as a key component underlying Alzheimer's disease (AD) progression; however, human neuronal in vitro models have struggled to recapitulate tau phenomena observed in vivo. Here, we aimed to define the minimal requirements to achieve endogenous tau aggregation in functional neurons utilizing human induced pluripotent stem cell (hiPSC) technology. Optimized hiPSC-derived cortical neurons seeded with AD brain-derived competent tau species or recombinant tau fibrils displayed increases in insoluble, endogenous tau aggregates. Importantly, MAPT-wild type and MAPT-mutant hiPSC-neurons exhibited unique propensities for aggregation dependent on the seed strain rather than the repeat domain identity, suggesting that successful templating of the recipient tau may be driven by the unique conformation of the seed. The in vitro model presented here represents the first successful demonstration of combining human neurons, endogenous tau expression, and AD brain-derived competent tau species, offering a more physiologically relevant platform to study tau pathobiology.

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Seeded tau aggregation in hiPSC-neurons does not require tau overexpression

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Tau aggregation is concentration, time, and maturation dependent

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Successful templating requires compatibility between neuronal tau and added seeds

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Endogenous tau aggregates exhibit properties consistent with pathological tau

Recent Advances in the Development of Stem-Cell-Derived Dopaminergic Neuronal Transplant Therapies for Parkinson's Disease

The last decade has seen exciting advances in the development of potential stem cell-based therapies for Parkinson's disease (PD), which have used different types of stem cells as starting material. These cells have been developed primarily to replace dopamine-producing neurons in the substantia nigra that are progressively lost in the disease process. The aim is to largely restore lost motor functions, whilst not ever being curative. We discuss cell-based strategies that will have to fulfill important criteria to become effective and competitive therapies for PD. These criteria include reproducibly producing sufficient numbers of cells with an authentic substantia nigra dopamine neuron A9 phenotype, which can integrate into the host brain after transplantation and form synapses (considered crucial for long-term functional benefits). Furthermore, it is essential that transplanted cells exhibit no, or only very low levels of, proliferation without tumor formation at the site of grafting. Cumulative research has shown that stem cell-based approaches continue to have great potential in PD, but key questions remain to be answered. Here, we review the most recent progress in research on stem cell-based dopamine neuron replacement therapy for PD and briefly discuss what the immediate future might hold. © 2021 International Parkinson and Movement Disorder Society.

Mitomycin-C treatment during differentiation of induced pluripotent stem cell-derived dopamine neurons reduces proliferation without compromising survival or function in vivo

Nongenetic methodologies to reduce undesirable proliferation would be valuable when generating dopamine neurons from stem cells for transplantation in Parkinson's disease (PD). To this end, we modified an established method for controlled differentiation of human induced pluripotent stem cells (iPSCs) into midbrain dopamine neurons using two distinct methods: omission of FGF8 or the in‐process use of the DNA cross‐linker mitomycin‐C (MMC). We transplanted the cells to athymic rats with unilateral 6‐hydroxydopamine lesions and monitored long‐term survival and function of the grafts. Transplants of cells manufactured using MMC had low proliferation while still permitting robust survival and function comparable to that seen with transplanted dopamine neurons derived using genetic drug selection. Conversely, cells manufactured without FGF8 survived transplantation but exhibited poor in vivo function. Our results suggest that MMC can be used to reduce the number of proliferative cells in stem cell‐derived postmitotic neuron preparations for use in PD cell therapy.