Fluid shear stress promotes embryonic stem cell pluripotency via interplay between ß-catenin and vinculin in bioreactor culture.

The expansion of pluripotent stem cells (PSCs) as aggregates in stirred suspension bioreactors is garnering attention as an alternative to adherent culture. However, the hydrodynamic environment in the bioreactor can modulate PSC behavior, pluripotency and differentiation potential in ways that need to be well understood. In this study, we investigated how murine embryonic stem cells (mESCs) sense fluid shear stress and modulate a noncanonical Wnt signaling response to promote pluripotency. mESCs showed higher expression of pluripotency marker genes, Oct4, Sox2, and Nanog in the absence of leukemia inhibitory factor (LIF) in stirred suspension bioreactors compared to adherent culture, a phenomenon we have termed mechanopluripotency. In bioreactor culture, fluid shear promoted the nuclear translocation of the less well-known pluripotency regulator ß-catenin and concomitant increase of c-Myc expression, an upstream regulator of Oct4, Sox2, and Nanog. We also observed similar ß-catenin nuclear translocation in LIF-free mESCs cultured on E-cadherin substrate under defined fluid shear stress conditions in flow chamber plates. mESCs showed lower shear-induced expression of pluripotency marker genes when ß-catenin was inhibited, suggesting that ß-catenin signaling is crucial to mESC mechanopluripotency. Key to this process is vinculin, which is known to rearrange and associate more strongly with adherens junctions in response to fluid shear. When the vinculin gene is disrupted, we observe that nuclear ß-catenin translocation and mechanopluripotency are abrogated. Our results indicate that mechanotransduction through the adherens junction complex is important for mESC pluripotency maintenance.

Enhanced Osteogenic Differentiation of Pluripotent Stem Cells via γ-Secretase Inhibition.

Bone healing is a complex, well-organized process. Multiple factors regulate this process, including growth factors, hormones, cytokines, mechanical stimulation, and aging. One of the most important signaling pathways that affect bone healing is the Notch signaling pathway. It has a significant role in controlling the differentiation of bone mesenchymal stem cells and forming new bone. Interventions to enhance the healing of critical-sized bone defects are of great importance, and stem cell transplantations are eminent candidates for treating such defects. Understanding how Notch signaling impacts pluripotent stem cell differentiation can significantly enhance osteogenesis and improve the overall healing process upon transplantation. In Rancourt's lab, mouse embryonic stem cells (ESC) have been successfully differentiated to the osteogenic cell lineage. This study investigates the role of Notch signaling inhibition in the osteogenic differentiation of mouse embryonic and induced pluripotent stem cells (iPS). Our data showed that Notch inhibition greatly enhanced the differentiation of both mouse embryonic and induced pluripotent stem cells.

Cardiomyocyte marker expression in mouse embryonic fibroblasts by cell-free cardiomyocyte extract and epigenetic manipulation.

BACKGROUND: The regenerative capacity of the mammalian heart is quite limited. Recent reports have focused on reprogramming mesenchymal stem cells into cardiomyocytes. We investigated whether fibroblasts could transdifferentiate into myocardium. METHODS: Mouse embryonic fibroblasts were treated with Trichostatin A (TSA) and 5-Aza-2-Deoxycytidine (5-aza-dC). The treated cells were permeabilized with streptolysin O and exposed to the mouse cardiomyocyte extract and cultured for 1, 10, and 21 days. Cardiomyocyte markers were detected by immunohistochemistry. Alkaline phosphatase activity and OCT4 were also detected in cells treated by chromatin-modifying agents. RESULTS: The cells exposed to a combination of 5-aza-dC and TSA and permeabilized in the presence of the cardiomyocyte extract showed morphological changes. The cells were unable to express cardiomyocyte markers after 24 h. Immunocytochemical assays showed a notable degree of myosin heavy chain and α-actinin expressions after 10 days. The expression of the natriuretic factor and troponin T occurred after 21 days in these cells. The cells exposed to chromatin-modifying agents also expressed cardiomyocyte markers; however, the proportion of reprogrammed cells was clearly smaller than that in the cultures exposed to 5-aza-dC , TSA, and extract. CONCLUSION: It seems that the fibroblasts were able to eliminate the previous epigenetic markers and form new ones according to the factors existing in the extract. Since no beating was observed, at least up to 21 days, the cells may need an appropriate extracellular matrix for their function.

Modulation of Reoviral Cytolysis (II): Cellular Stemness.

Oncolytic viruses (OVs) are an emerging cancer therapeutic that are intended to act by selectively targeting and lysing cancerous cells and by stimulating anti-tumour immune responses, while leaving normal cells mainly unaffected. Reovirus is a well-studied OV that is undergoing advanced clinical trials and has received FDA approval in selected circumstances. However, the mechanisms governing reoviral selectivity are not well characterised despite many years of effort, including those in our accompanying paper where we characterize pathways that do not consistently modulate reoviral cytolysis. We have earlier shown that reovirus is capable of infecting and lysing both certain types of cancer cells and also cancer stem cells, and here we demonstrate its ability to also infect and kill healthy pluripotent stem cells (PSCs). This led us to hypothesize that pathways responsible for stemness may constitute a novel route for the modulation of reoviral tropism. We find that reovirus is capable of killing both murine and human embryonic and induced pluripotent stem cells. Differentiation of PSCs alters the cells' reoviral-permissive state to a resistant one. In a breast cancer cell line that was resistant to reoviral oncolysis, induction of pluripotency programming rendered the cells permissive to cytolysis. Bioinformatic analysis indicates that expression of the Yamanaka pluripotency factors may be associated with regulating reoviral selectivity. Mechanistic insights from these studies will be useful for the advancement of reoviral oncolytic therapy.

3D bioprinting for organ and organoid models and disease modeling.

INTRODUCTION: 3D printing, a versatile additive manufacturing technique, has diverse applications ranging from transportation, rapid prototyping, clean energy, and medical devices. AREAS COVERED: The authors focus on how 3D printing technology can enhance the drug discovery process through automating tissue production that enables high-throughput screening of potential drug candidates. They also discuss how the 3D bioprinting process works and what considerations to address when using this technology to generate cell laden constructs for drug screening as well as the outputs from such assays necessary for determining the efficacy of potential drug candidates. They focus on how bioprinting how has been used to generate cardiac, neural, and testis tissue models, focusing on bio-printed 3D organoids. EXPERT OPINION: The next generation of 3D bioprinted organ model holds great promises for the field of medicine. In terms of drug discovery, the incorporation of smart cell culture systems and biosensors into 3D bioprinted models could provide highly detailed and functional organ models for drug screening. By addressing current challenges of vascularization, electrophysiological control, and scalability, researchers can obtain more reliable and accurate data for drug development, reducing the risk of drug failures during clinical trials.

Expression of a2, a5 and a6 subunits of integrin in de-differentiated NIH3T3 cells by cell-free extract of embryonic stem cells.

Generation of patient specific stem cells is among the ultimate goals in regenerative medicine. Such a cell needs to be functional when it transplants. Interaction between the matrix proteins and integrin adjust many cells' function such as adhesion, migration, cell cycle and self renewal in stem cells. In this study, NIH3T3 cells were dedifferentiated by mouse Embryonic Stem Cell (mESC) extract. The expression of pluripotency markers as well as a2, a5 and a6 integrin subunits were determined. NIH3T3 cells treated with mESC extract showed noticeable changes in cell morphology as early as day 2 post-treatment forming colonies similar to typical mESC morphology by day 8, after three passages. Alkaline phosphatase (ALP) assay and immunocytochemistry staining were performed for the induced reprogrammed cells. The results indicated that these colonies showed the ALP activity and they express Sox2 and Nanog. RT-PCR revealed that the colonies also express Oct3/4. NIH3T3 cells, ESC and reprogrammed cells expressed a2 integrin. a5 integrin expression was greatest in reprogrammed cells followed by the expression of this integrin in NIH3T3 which in turn was more than in ESC. a6A integrin was expressed in NIH3T3 cells while a6B integrin was expressed in ESC and in very low quantity was expressed in reprogrammed cells. These data provide evidence for both the generation of ES like cells from differentiated somatic cells and the expression profile of integrins after de-differentiation by mESC extract.

Isolating Nuclei From Frozen Human Heart Tissue for Single-Nucleus RNA Sequencing.

Heart disease is the leading cause of global morbidity and mortality. This is in part because, despite an abundance of animal and in vitro models, it has been a challenge to date to study human heart tissue with sufficient depth and resolution to develop disease-modifying therapies for common cardiac conditions. Single-nucleus RNA sequencing (snRNA-seq) has emerged as a powerful tool capable of analyzing cellular function and signaling in health and disease, and has already contributed to significant advances in areas such as oncology and hematology. Employing snRNA-seq technology on flash-frozen human tissue has the potential to unlock novel disease mechanisms and pathways in any organ. Studying the human heart using snRNA-seq is a key priority for the field of cardiovascular sciences; however, progress to date has been slowed by numerous barriers. One key challenge is the fact that the human heart is very resistant to shearing and stress, making tissue dissociation and nuclear isolation difficult. Here, we describe a tissue dissociation method allowing the efficient and cost-effective isolation of high-quality nuclei from flash-frozen human heart tissue collected in surgical operating rooms. Our protocol addresses the challenge of nuclear isolation from human hearts, enables snRNA-seq of the human heart, and paves the way for an improved understanding of the human heart in health and disease. Ultimately, this will be key to uncovering signaling pathways and networks amenable to therapeutic intervention and the development of novel biomarkers and disease-modifying therapies. © 2022 Wiley Periodicals LLC. Basic Protocol: Human heart tissue dissociation and nuclear isolation for snRNA-seq.

Overcoming bioprocess bottlenecks in the large-scale expansion of high-quality hiPSC aggregates in vertical-wheel stirred suspension bioreactors.

BACKGROUND: Human induced pluripotent stem cells (hiPSCs) hold enormous promise in accelerating breakthroughs in understanding human development, drug screening, disease modeling, and cell and gene therapies. Their potential, however, has been bottlenecked in a mostly laboratory setting due to bioprocess challenges in the scale-up of large quantities of high-quality cells for clinical and manufacturing purposes. While several studies have investigated the production of hiPSCs in bioreactors, the use of conventional horizontal-impeller, paddle, and rocking-wave mixing mechanisms have demonstrated unfavorable hydrodynamic environments for hiPSC growth and quality maintenance. This study focused on using computational fluid dynamics (CFD) modeling to aid in characterizing and optimizing the use of vertical-wheel bioreactors for hiPSC production. METHODS: The vertical-wheel bioreactor was modeled with CFD simulation software Fluent at agitation rates between 20 and 100 rpm. These models produced fluid flow patterns that mapped out a hydrodynamic environment to guide in the development of hiPSC inoculation and in-vessel aggregate dissociation protocols. The effect of single-cell inoculation on aggregate formation and growth was tested at select CFD-modeled agitation rates and feeding regimes in the vertical-wheel bioreactor. An in-vessel dissociation protocol was developed through the testing of various proteolytic enzymes and agitation exposure times. RESULTS: CFD modeling demonstrated the unique flow pattern and homogeneous distribution of hydrodynamic forces produced in the vertical-wheel bioreactor, making it the opportune environment for systematic bioprocess optimization of hiPSC expansion. We developed a scalable, single-cell inoculation protocol for the culture of hiPSCs as aggregates in vertical-wheel bioreactors, achieving over 30-fold expansion in 6 days without sacrificing cell quality. We have also provided the first published protocol for in-vessel hiPSC aggregate dissociation, permitting the entire bioreactor volume to be harvested into single cells for serial passaging into larger scale reactors. Importantly, the cells harvested and re-inoculated into scaled-up vertical-wheel bioreactors not only maintained consistent growth kinetics, they maintained a normal karyotype and pluripotent characterization and function. CONCLUSIONS: Taken together, these protocols provide a feasible solution for the culture of high-quality hiPSCs at a clinical and manufacturing scale by overcoming some of the major documented bioprocess bottlenecks.

Molecular analyses of glioblastoma stem-like cells and glioblastoma tissue.

Glioblastoma is a common, malignant brain tumor whose disease incidence increases with age. Glioblastoma stem-like cells (GSCs) are thought to contribute to cancer therapy resistance and to be responsible for tumor initiation, maintenance, and recurrence. This study utilizes both SNP array and gene expression profiling to better understand GSCs and their relation to malignant disease. Peripheral blood and primary glioblastoma tumor tissue were obtained from patients, the latter of which was used to generate GSCs as well as a CD133pos./CD15pos. subpopulation. The stem cell features of GSCs were confirmed via the immunofluorescent expression of Nestin, SOX2, and CD133. Both tumor tissue and the isolated primary cells shared unique abnormal genomic characteristics, including a gain of chromosome 7 as well as either a partial or complete loss of chromosome 10. Individual genomic differences were also observed, including the loss of chromosome 4 and segmental uniparental disomy of 9p24.3→p21.3 in GSCs. Gene expression profiling revealed 418 genes upregulated in tumor tissue vs. CD133pos./CD15pos. cells and 44 genes upregulated in CD133pos./CD15pos. cells vs. tumor tissue. Pathway analyses demonstrated that upregulated genes in CD133pos./CD15pos. cells are relevant to cell cycle processes and cancerogenesis. In summary, we detected previously undescribed genomic and gene expression differences when comparing tumor tissue and isolated stem-like subpopulations.

Reversible Mitochondrial Fragmentation in iPSC-Derived Cardiomyocytes From Children With DCMA, a Mitochondrial Cardiomyopathy.

BACKGROUND: Dilated cardiomyopathy with ataxia syndrome (DCMA) is an understudied autosomal recessive disease caused by loss-of-function mutations in the poorly characterized gene DNAJC19. Clinically, DCMA is commonly associated with heart failure and early death in affected children through an unknown mechanism. DCMA has been linked to Barth syndrome, a rare but well-studied disorder caused by deficient maturation of cardiolipin (CL), a key mitochondrial membrane phospholipid. METHODS: Peripheral blood mononuclear cells from 2 children with DCMA and severe cardiac dysfunction were reprogrammed into induced pluripotent stem cells (iPSCs). Patient and control iPSCs were differentiated into beating cardiomyocytes (iPSC-CMs) using a metabolic selection strategy. Mitochondrial structure and CL content before and after incubation with the mitochondrially targeted peptide SS-31 were quantified. RESULTS: Patient iPSCs carry the causative DNAJC19 mutation (rs137854888) found in the Hutterite population, and the iPSC-CMs demonstrated highly fragmented and abnormally shaped mitochondria associated with an imbalanced isoform ratio of the mitochondrial protein OPA1, an important regulator of mitochondrial fusion. These abnormalities were reversible by incubation with SS-31 for 24 hours. Differentiation of iPSCs into iPSC-CMs increased the number of CL species observed, but consistent, significant differences in CL content were not seen between patients and control. CONCLUSIONS: We describe a unique and novel cellular model that provides insight into the mitochondrial abnormalities present in DCMA and identifies SS-31 as a potential therapeutic for this devastating disease.

Stirred suspension bioreactors maintain naïve pluripotency of human pluripotent stem cells.

Due to their ability to standardize key physiological parameters, stirred suspension bioreactors can potentially scale the production of quality-controlled pluripotent stem cells (PSCs) for cell therapy application. Because of differences in bioreactor expansion efficiency between mouse (m) and human (h) PSCs, we investigated if conversion of hPSCs, from the conventional "primed" pluripotent state towards the "naïve" state prevalent in mPSCs, could be used to enhance hPSC production. Through transcriptomic enrichment of mechano-sensing signaling, the expression of epigenetic regulators, metabolomics, and cell-surface protein marker analyses, we show that the stirred suspension bioreactor environment helps maintain a naïve-like pluripotent state. Our research corroborates that converting hPSCs towards a naïve state enhances hPSC manufacturing and indicates a potentially important role for the stirred suspension bioreactor's mechanical environment in maintaining naïve-like pluripotency.

Using computational fluid dynamics (CFD) modeling to understand murine embryonic stem cell aggregate size and pluripotency distributions in stirred suspension bioreactors.

Computational fluid dynamics (CFD) modeling can be applied to understand hydrodynamics in stirred suspension bioreactors, which can in turn affect cell viability, proliferation, pluripotency and differentiation. In this study, we developed a CFD model to determine the effects of average shear rates and turbulent eddies on the formation and growth of murine embryonic stem cell aggregates. We found a correlation between average eddy size and aggregate size, which depended on bioreactor agitation rates. By relating these computational and biological variables, CFD modeling can predict optimal agitation rates to grow embryonic stem cell aggregates in stirred suspension bioreactors. To examine the effect of hydrodynamics on pluripotency, mESCs cultured in bioreactors under various agitation rates were tested for SSEA-1, Sox-2, and Nanog expression. Cells maintained a minimum of 95% positive expression with no change in the intensity distribution pattern between the different bioreactor conditions. This indicates that the average level of pluripotency marker expression is independent of changes in the hydrodynamic profile and resulting aggregate size distribution. The findings here can be further extended to other cell types that grow as aggregates in stirred suspension bioreactors and offer important insights necessary to realize cell therapies.

Concise Review: Molecular Cytogenetics and Quality Control: Clinical Guardians for Pluripotent Stem Cells.

Now that induced pluripotent stem cell (iPSC)-based transplants have been performed in humans and organizations have begun producing clinical-grade iPSCs, it is imperative that strict quality control standards are agreed upon. This is essential as both ESCs and iPSCs have been shown to accumulate genomic aberrations during long-term culturing. These aberrations can include copy number variations, trisomy, amplifications of chromosomal regions, deletions of chromosomal regions, loss of heterozygosity, and epigenetic abnormalities. Moreover, although the differences between iPSCs and ESCs appear largely negligible when a high enough n number is used for comparison, the reprogramming process can generate further aberrations in iPSCs, including copy number variations and deletions in tumor-suppressor genes. If mutations or epigenetic signatures are present in parental cells, these can also be carried over into iPSCs. To maximize patient safety, we recommend a set of standards to be utilized when preparing iPSCs for clinical use. Reprogramming methods that do not involve genomic integration should be used. Cultured cells should be grown using feeder-free and serum-free systems to avoid animal contamination. Karyotyping, whole-genome sequencing, gene expression analyses, and standard sterility tests should all become routine quality control tests. Analysis of mitochondrial DNA integrity, whole-epigenome analyses, as well as single-cell genome sequencing of large cell populations may also prove beneficial. Furthermore, clinical-grade stem cells need to be produced under accepted regulatory good manufacturing process standards. The creation of haplobanks that provide major histocompatibility complex matching is also recommended to improve allogeneic stem cell engraftment. Stem Cells Translational Medicine 2018;7:867-875.

Expansion of Human Induced Pluripotent Stem Cells in Stirred Suspension Bioreactors.

Human induced pluripotent stem cells (hiPSCs) hold great promise as a cell source for therapeutic applications and regenerative medicine. Traditionally, hiPSCs are expanded in two-dimensional static culture as colonies in the presence or absence of feeder cells. However, this expansion procedure is associated with lack of reproducibility and low cell yields. To fulfill the large cell number demand for clinical use, robust large-scale production of these cells under defined conditions is needed. Herein, we describe a scalable, low-cost protocol for expanding hiPSCs as aggregates in a lab-scale bioreactor.

The aging signature: a hallmark of induced pluripotent stem cells?

The discovery that somatic cells can be induced into a pluripotent state by the expression of reprogramming factors has enormous potential for therapeutics and human disease modeling. With regard to aging and rejuvenation, the reprogramming process resets an aged, somatic cell to a more youthful state, elongating telomeres, rearranging the mitochondrial network, reducing oxidative stress, restoring pluripotency, and making numerous other alterations. The extent to which induced pluripotent stem cell (iPSC)s mime embryonic stem cells is controversial, however, as iPSCs have been shown to harbor an epigenetic memory characteristic of their tissue of origin which may impact their differentiation potential. Furthermore, there are contentious data regarding the extent to which telomeres are elongated, telomerase activity is reconstituted, and mitochondria are reorganized in iPSCs. Although several groups have reported that reprogramming efficiency declines with age and is inhibited by genes upregulated with age, others have successfully generated iPSCs from senescent and centenarian cells. Mixed findings have also been published regarding whether somatic cells generated from iPSCs are subject to premature senescence. Defects such as these would hinder the clinical application of iPSCs, and as such, more comprehensive testing of iPSCs and their potential aging signature should be conducted.

Mesenchymal stem cells repair germinal cells of seminiferous tubules of sterile rats.

BACKGROUND: Mesenchymal stem cells (MSCs) are undifferentiated cells that can differentiate and divide to other cell types. Transplantation of these cells to the different organs is used for curing various diseases. OBJECTIVE: The aim of this research was whether MSCs transplantation could treat the sterile testes. MATERIALS AND METHODS: In this experimental study, Donor MSCs were isolated from bone marrow of Wistar rats. The recipients were received 40 mg/kg of busulfan to stop endogenous spermatogenesis. The MSCs were injected into the left testes. Cell tracing was done by labeling the MSCs by 5-Bromo-2- Deoxy Uridine (BrdU). The immunohistochemical and morphometrical studies were performed to analysis the curing criteria. RESULTS: The number of spermatogonia (25.38±1.57), primary spermatocytes (55.41±1.62) and spermatozoids (4.95±1.30)×10(6) in busulfan treated animals were decreased significantly as compared to the control group (33.35±1.78, 64.44±2.00) and (10.50±1.82)×10(6) respectively but stem cells therapy help the spermatogenesis begin more effective in these animals (32.78±1.99, 63.59±2.01) and (9.81±1.33)×10(6) respectively than the control group. The injected BrdU labeled mesenchymal stem cells differentiated to spermatogonia and spermatozoa in the seminiferous tubules of the infertile testis and also to the interstitial cells between tubules. CONCLUSION: We concluded that testis of host infertile rats accepted transplanted MSCs. The transplanted MSCs could differentiate into germinal cells in testicular seminiferous tubules. This article extracted from M.Sc. Thesis. (Bentolhoda Fereydouni).