Nitric oxide-cyclic GMP signaling in stem cell differentiation

Regulation and Pharmacology of the Cyclic GMP and Nitric Oxide Pathway in Embryonic and Adult Stem Cells

This review summarizes recent advances in understanding the role of the nitric oxide (NO) and cyclic GMP (cGMP) pathway in stem cells. The levels of expression of various components of the pathway are changed during the differentiation of pluripotent embryonic stem cells. In undifferentiated stem cells, NO regulates self-renewal and survival predominantly through cGMP-independent mechanisms. Natriuretic peptides influence the growth of undifferentiated stem cells by activating particulate isoforms of guanylyl cyclases in a cGMP-mediated manner. The differentiation, recruitment, survival, migration, and homing of partially differentiated precursor cells of various types are sensitive to regulation by endogenous levels of NO and natriuretic peptides produced by stem cells, within surrounding tissues, and by the application of various pharmacological agents known to influence the cGMP pathway. Numerous drugs and formulations target various components of the cGMP pathway to influence the therapeutic efficacy of stem cell-based therapies. Thus, pharmacological manipulation of the cGMP pathway in stem cells can be potentially used to develop novel strategies in regenerative medicine.

Nitric oxide as a double-edged sword in pulmonary viral infections: Mechanistic insights and potential therapeutic implications

In the face of the global pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), researchers are tirelessly exploring novel therapeutic approaches to combat coronavirus disease 2019 (COVID-19) and its associated complications. Nitric oxide (NO) has appeared as a multifaceted signaling mediator with diverse and often contrasting biological activities. Its intricate biochemistry renders it a crucial regulator of cardiovascular and pulmonary functions, immunity, and neurotransmission. Perturbations in NO production, whether excessive or insufficient, contribute to the pathogenesis of various diseases, encompassing cardiovascular disease, pulmonary hypertension, asthma, diabetes, and cancer. Recent investigations have unveiled the potential of NO donors to impede SARS-CoV- 2 replication, while inhaled NO demonstrates promise as a therapeutic avenue for improving oxygenation in COVID-19-related hypoxic pulmonary conditions. Interestingly, NO's association with the inflammatory response in asthma suggests a potential protective role against SARS-CoV-2 infection. Furthermore, compelling evidence indicates the benefits of inhaled NO in optimizing ventilation-perfusion ratios and mitigating the need for mechanical ventilation in COVID-19 patients. In this review, we delve into the molecular targets of NO, its utility as a diagnostic marker, the mechanisms underlying its action in COVID-19, and the potential of inhaled NO as a therapeutic intervention against viral infections. The topmost significant pathway, gene ontology (GO)-biological process (BP), GO-molecular function (MF) and GO-cellular compartment (CC) terms associated with Nitric Oxide Synthase (NOS)1, NOS2, NOS3 were arginine biosynthesis (p-value = 1.15 x 10-9) regulation of guanylate cyclase activity (p-value = 7.5 x 10-12), arginine binding (p-value = 2.62 x 10-11), vesicle membrane (p-value = 3.93 x 10-8). Transcriptomics analysis further validates the significant presence of NOS1, NOS2, NOS3 in independent COVID-19 and pulmonary hypertension cohorts with respect to controls. This review investigates NO's molecular targets, diagnostic potentials, and therapeutic role in COVID-19, employing bioinformatics to identify key pathways and NOS isoforms' significance.

Intracellular delivery of nitric oxide enhances the therapeutic efficacy of mesenchymal stem cells for myocardial infarction

Cell therapy by autologous mesenchymal stem cells (MSCs) is a clinically acceptable strategy for treating various diseases. Unfortunately, the therapeutic efficacy is largely affected by the low quality of MSCs collected from patients. Here, we showed that the gene expression of MSCs from patients with diabetes was differentially regulated compared to that of MSCs from healthy controls. Then, MSCs were genetically engineered to catalyze an NO prodrug to release NO intracellularly. Compared to extracellular NO conversion, intracellular NO delivery effectively prolonged survival and enhanced the paracrine function of MSCs, as demonstrated by in vitro and in vivo assays. The enhanced therapeutic efficacy of engineered MSCs combined with intracellular NO delivery was further confirmed in mouse and rat models of myocardial infarction, and a clinically relevant cell administration paradigm through secondary thoracotomy has been attempted.

Association between the Polymorphisms rs2070744, 4b/a and rs1799983 of the NOS3 Gene with Chronic Kidney Disease of Uncertain or Non-Traditional Etiology in Mexican Patients

Background and Objectives: Chronic Kidney Disease of uncertain or non-traditional etiology (CKDnT) is a form of chronic kidney disease of undetermined etiology (CKDu) and is not associated with traditional risk factors. The aim of this study was to investigate the association of polymorphisms rs2070744, 4b/a and rs1799983 of the NOS3 gene with CKDnT in Mexican patients. Materials and Methods: We included 105 patients with CKDnT and 90 controls. Genotyping was performed by PCR-RFLP's, genotypic and allelic frequencies were determined and compared between the two groups using χ2 analysis, and differences were expressed as odd ratios with 95% confidence intervals (CI). Values of p < 0.05 were considered statistically significant. Results: Overall, 80% of patients were male. The rs1799983 polymorphism in NOS3 was found to be associated with CKDnT in the Mexican population (p = 0.006) (OR = 0.397; 95% CI, 0.192-0.817) under a dominant model. The genotype frequency was significantly different between the CKDnT and control groups (χ2 = 8.298, p = 0.016). Conclusions: The results of this study indicate that there is an association between the rs2070744 polymorphism and CKDnT in the Mexican population. This polymorphism can play an important role in the pathophysiology of CKDnT whenever there is previous endothelial dysfunction.

The Role of Nitric Oxide in Stem Cell Biology

Nitric oxide (NO) is a gaseous biomolecule endogenously synthesized with an essential role in embryonic development and several physiological functions, such as regulating mitochondrial respiration and modulation of the immune response. The dual role of NO in embryonic stem cells (ESCs) has been previously reported, preserving pluripotency and cell survival or inducing differentiation with a dose-dependent pattern. In this line, high doses of NO have been used in vitro cultures to induce focused differentiation toward different cell lineages being a key molecule in the regenerative medicine field. Moreover, optimal conditions to promote pluripotency in vitro are essential for their use in advanced therapies. In this sense, the molecular mechanisms underlying stemness regulation by NO have been studied intensively over the current years. Recently, we have reported the role of low NO as a hypoxia-like inducer in pluripotent stem cells (PSCs), which supports using this molecule to maintain pluripotency under normoxic conditions. In this review, we stress the role of NO levels on stem cells (SCs) fate as a new approach for potential cell therapy strategies. Furthermore, we highlight the recent uses of NO in regenerative medicine due to their properties regulating SCs biology.

Steering the multipotent mesenchymal cells towards an anti-inflammatory and osteogenic bias via photobiomodulation therapy: How to kill two birds with one stone

The bone marrow-derived multipotent mesenchymal cells (MSCs) have captured scientific interest due to their multi-purpose features and clinical applications. The operational dimension of MSCs is not limited to the bone marrow reservoir, which exerts bone-building and niche anabolic tasks; they also meet the needs of quenching inflammation and restoring inflamed tissues. Thus, the range of MSC activities extends to conditions such as neurodegenerative diseases, immune disorders and various forms of osteopenia. Steering these cells towards becoming an effective therapeutic tool has become mandatory. Many laboratories have employed distinct strategies to improve the plasticity and secretome of MSCs. We aimed to present how photobiomodulation therapy (PBM-t) can manipulate MSCs to render them an extraordinary anti-inflammatory and osteogenic instrument. Moreover, we discuss the outcomes of different PBM-t protocols on MSCs, concluding with some perplexities and complexities of PBM-t in vivo but encouraging and feasible in vitro solutions.

Expression of nitric oxide synthases in rat odontoblasts and the role of nitric oxide in odontoblastic differentiation of rat dental papilla cells

As precursor cells of odontoblasts, dental papilla cells (DPCs) form the dentin-pulp complex during tooth development. Nitric oxide (NO) regulates the functions of multiple cells and organ tissues, including stem cell differentiation and bone formation. In this paper, we explored the involvement of NO in odontoblastic differentiation. We verified the expression of NO synthase (NOS) in rat odontoblasts by nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) staining and immunohistochemistry in vivo. The expression of all three NOS isoforms in rat DPCs was confirmed by quantitative reverse-transcription polymerase chain reaction (qRT-PCR), immunofluorescence, and western blotting in vitro. The expression of neuronal NOS and endothelial NOS was upregulated during the odontoblastic differentiation of DPCs. Inhibition of NOS function by NOS inhibitor l-N^G -monomethyl arginine (L-NMMA) resulted in reduced formation of mineralized nodules and expression of dentin sialophosphoprotein (DSPP) and dentin matrix protein (DMP1) during DPC differentiation. The NO donor S-nitroso-N-acetylpenicillamine (SNAP, 0.1, 1, 10, and 100 μM) promoted the viability of DPCs. Extracellular matrix mineralization and odontogenic markers expression were elevated by SNAP at low concentrations (0.1, 1, and 10 μM) and suppressed at high concentration (100 μM). Blocking the generation of cyclic guanosine monophosphate (cGMP) with 1H-(1,2,4)oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ) abolished the positive influence of SNAP on the odontoblastic differentiation of DPCs. These findings demonstrate that NO regulates the odontoblastic differentiation of DPCs, thereby influencing dentin formation and tooth development.

Physical Exercise and Cardiac Repair: The Potential Role of Nitric Oxide in Boosting Stem Cell Regenerative Biology

Over the years strong evidence has been accumulated showing that aerobic physical exercise exerts beneficial effects on the prevention and reduction of cardiovascular risk. Exercise in healthy subjects fosters physiological remodeling of the adult heart. Concurrently, physical training can significantly slow-down or even reverse the maladaptive pathologic cardiac remodeling in cardiac diseases, improving heart function. The underlying cellular and molecular mechanisms of the beneficial effects of physical exercise on the heart are still a subject of intensive study. Aerobic activity increases cardiovascular nitric oxide (NO) released mainly through nitric oxidase synthase 3 activity, promoting endothelium-dependent vasodilation, reducing vascular resistance, and lowering blood pressure. On the reverse, an imbalance between increasing free radical production and decreased NO generation characterizes pathologic remodeling, which has been termed the "nitroso-redox imbalance". Besides these classical evidence on the role of NO in cardiac physiology and pathology, accumulating data show that NO regulate different aspects of stem cell biology, including survival, proliferation, migration, differentiation, and secretion of pro-regenerative factors. Concurrently, it has been shown that physical exercise generates physiological remodeling while antagonizes pathologic remodeling also by fostering cardiac regeneration, including new cardiomyocyte formation. This review is therefore focused on the possible link between physical exercise, NO, and stem cell biology in the cardiac regenerative/reparative response to physiological or pathological load. Cellular and molecular mechanisms that generate an exercise-induced cardioprotective phenotype are discussed in regards with myocardial repair and regeneration. Aerobic training can benefit cells implicated in cardiovascular homeostasis and response to damage by NO-mediated pathways that protect stem cells in the hostile environment, enhance their activation and differentiation and, in turn, translate to more efficient myocardial tissue regeneration. Moreover, stem cell preconditioning by and/or local potentiation of NO signaling can be envisioned as promising approaches to improve the post-transplantation stem cell survival and the efficacy of cardiac stem cell therapy.

A novel derivatization strategy for profiling phosphate ester/anhydride metabolic network and application on glioma rats using HILIC-MS/MS

Phosphate esters and anhydrides have great significance in the field of biochemical research and medical therapy. The genetic materials (DNA or RNA), most of the coenzymes, many intermediary metabolites, such as nucleotides and glycosyl phosphates in vivo are phosphodiesters, phosphoric acid or phosphates, respectively. It is important to monitor endogenous active phosphate metabolites for investigating many biological processes or drug mechanism. However, the detection and determination of those free active phosphate metabolites are challenged due to their unstable and easily hydrolyzed property and relatively low sensitivity, especially diphosphates and triphosphates. In the current study, we successfully developed a strategy by 3-aminomethyl pyridine (AMPy) derivatization coupled with hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) for simultaneous determination of multiple types of phosphate metabolites with good stability in 48 h and 29 to 126-fold improvement of the limit of detection (LOD). Based on the diagnostic fragment ions of different types of AMPy-derivatized phosphate metabolites, characteristic MRM ion pairs were successfully performed for global profiling of the phosphate metabolites in phosphate ester/anhydride metabolic network, including nucleotide/deoxynucleotide mono/di/triphosphates, glycosyl mono/diphosphates, and other key phosphates, such as 5-phosphoribosyl-1-pyrophosphate (PRPP), SAICARP and FAICARP in HPF, HUVEC and PBMCs cells without standards. The developed strategy greatly expanded the coverage of applying a single derivatization reaction to analyze active phosphate metabolites. Finally, the established method was performed to investigate the phosphate esters and anhydrides based on a glioma rat model. For the first time, phosphate metabolites were comprehensively characterized based on phosphate ester and anhydride metabolic network, covering nucleotide metabolism, glycolysis and pentose phosphate pathways, etc. The results demonstrated that the applicability of the method could be extended to a wider range of active phosphate compounds and could facilitate to related applications in the future studies.

Synthesis, characterization and in vitro biological evaluation of novel organotin(IV) compounds with derivatives of 2-(5-arylidene-2,4-dioxothiazolidin-3-yl)propanoic acid

Two novel triphenyltin(IV) compounds, [Ph₃SnL1] (L1 = 2-(5-(4-fluorobenzylidene)-2,4-dioxotetrahydrothiazole-3-yl)propanoate (1)) and [Ph₃SnL2] (L2 = 2-(5-(5-methyl-2-furfurylidene)-2,4-dioxotetrahydrothiazole-3-yl)propanoate (2)) were synthesized and characterized by FT-IR, (¹H and ¹³C) NMR spectroscopy, mass spectrometry, and elemental microanalysis. The in vitro anticancer activity of the synthesized organotin(IV) compounds was determined against four tumor cell lines: PC-3 (prostate), HT-29 (colon), MCF-7 (breast), and HepG2 (hepatic) using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-12 diphenyltetrazolium bromide) and CV (crystal violet) assays. The IC₅₀ values are found to be in the range from 0.11 to 0.50 μM. Compound 1 exhibits the highest activity toward PC-3 cells (IC₅₀ = 0.115 ± 0.009 μM; CV assay). The tin and platinum uptake in PC-3 cells showed a threefold lower uptake of tin in comparison to platinum (as cisplatin). Together with its higher activity this indicates a much higher cell inhibition potential of the tin compounds (calculated to ca. 50 to 100 times). Morphological analysis suggested that the compounds induce apoptosis in PC-3 cells, and flow cytometry analysis revealed that 1 and 2 induce autophagy as well as NO (nitric oxide) production.

Nitric-Oxide-Releasing Biomaterial Regulation of the Stem Cell Microenvironment in Regenerative Medicine

Stem cell therapy has proven to be an attractive solution for the treatment of degenerative diseases or injury. However, poor cell engraftment and survival within injured tissues limits the successful use of stem cell therapy within the clinical setting. Nitric oxide (NO) is an important signaling molecule involved in various physiological processes. Emerging evidence supports NO's diverse roles in modulating stem cell behavior, including survival, migration, differentiation, and paracrine secretion of proregenerative factors. Thus, there has been a shift in research focus to concentrate efforts on the delivery of therapeutic concentration ranges of NO to the target tissue sites. Combinatory therapies utilizing biomaterials that control NO generation and support stem cell delivery can be holistic and synergistic approaches to significantly improve tissue regeneration. Here, the focus is on recent developments of various therapeutic platforms, engineered to both transport NO and to enhance stem-cell-mediated regeneration of damaged tissues. New and emerging revelations of how the stem cell microenvironment can be regulated by NO-releasing biomaterials are also highlighted.

Generation of a nitric oxide signaling pathway in mesenchymal stem cells promotes endothelial lineage commitment

Enhancing differentiation of mesenchymal stem cells (MSCs) to endothelial cells may improve their ability to vascularize tissue and promote wound healing. This study describes a novel role for nitric oxide (NO) in reprogramming MSCs towards an endothelial lineage and highlights the role of Wnt signaling and epigenetic modification by NO. Rat MSCs were transduced with lentiviral vectors expressing endothelial nitric oxide synthase (pLV-eNOS) and a mutated caveolin gene (pLV-CAV-1^F92A ) to enhance NO generation resulting in increased in vitro capillary tubule formation and endothelial marker gene expression. An exogenous source of NO could also stimulate CD31 expression in MSCs. NO was associated with an arterial-specific endothelial gene expression profile of Notch1, Dll4, and Hey2 and significantly reduced expression of venous markers. Wnt signaling associated with NO was evident through increased gene expression of Wnt3a and β-catenin protein, and expression of the endothelial marker Pecam-1 could be significantly reduced by treatment with the Wnt signaling inhibitor Dkk-1. The role of NO as an epigenetic modifier was evident with reduced gene expression of the methyltransferase, DNMT1, and bisulfite sequencing of the endothelial Flt1 promoter region in NO-producing MSCs showed significant demethylation compared to control cells. Finally, subcutaneous implantation of NO-producing MSCs seeded in a biomaterial scaffold (NovoSorb®) resulted in survival of transplanted cells and the formation of blood vessels. In summary, this study describes, NO as a potent endothelial programming factor which acts as an epigenetic modifier in MSCs and may provide a novel platform for vascular regenerative therapy.

Validation of a LC/MSMS method for simultaneous quantification of 9 nucleotides in biological matrices

Nucleotides play a role in inflammation processes: cAMP and cGMP in the endothelial barrier function, ADP in platelet aggregation, ATP and UTP in vasodilatation and/or vasoconstriction of blood vessels, UDP in macrophages activation. The aim of this study is to develop and validate a LC/MS-MS method able to quantify simultaneously nine nucleotides (AMP, cAMP, ADP, ATP, GMP, cGMP, UMP, UDP and UTP) in biological matrixes (cells and plasma). The method we developed, has lower LOQ's than others and has the main advantage to quantify all nucleotides within one single injection in less than 10 min. The measured nucleotides concentrations obtained with this method are similar to those obtained with assay kits commercially available. Analysis of plasma and red blood cells from healthy donors permits to estimate the physiological concentration of those nucleotides in human plasma and red blood cells, such information being poorly available in the literature. Furthermore, the protocol presented in this paper allowed us to observe that AMP, ADP, ATP concentrations are modified in human red blood cells and plasma after a venous stasis of 4 min compared to physiological blood circulation. Therefore, this specific method enables future studies on nucleotides implications in chronic inflammatory diseases but also in other pathologies where nucleotides are implicated in.

Cell-specific proteome analyses of human bone marrow reveal molecular features of age-dependent functional decline

Diminishing potential to replace damaged tissues is a hallmark for ageing of somatic stem cells, but the mechanisms remain elusive. Here, we present proteome-wide atlases of age-associated alterations in human haematopoietic stem and progenitor cells (HPCs) and five other cell populations that constitute the bone marrow niche. For each, the abundance of a large fraction of the ~12,000 proteins identified is assessed in 59 human subjects from different ages. As the HPCs become older, pathways in central carbon metabolism exhibit features reminiscent of the Warburg effect, where glycolytic intermediates are rerouted towards anabolism. Simultaneously, altered abundance of early regulators of HPC differentiation reveals a reduced functionality and a bias towards myeloid differentiation. Ageing causes alterations in the bone marrow niche too, and diminishes the functionality of the pathways involved in HPC homing. The data represent a valuable resource for further analyses, and for validation of knowledge gained from animal models.

Ageing causes an inability to replace damaged tissue. Here, the authors perform proteomics analyses of human haematopoietic stem cells and other cells in the bone marrow niche at different ages and show changes in central carbon metabolism, reduced bone marrow niche function, and enhanced myeloid differentiation.

Differentiation of Human Induced Pluripotent or Embryonic Stem Cells Decreases the DNA Damage Repair by Homologous Recombination

The nitric oxide (NO)-cyclic GMP pathway contributes to human stem cell differentiation, but NO free radical production can also damage DNA, necessitating a robust DNA damage response (DDR) to ensure cell survival. How the DDR is affected by differentiation is unclear. Differentiation of stem cells, either inducible pluripotent or embryonic derived, increased residual DNA damage as determined by γ-H2AX and 53BP1 foci, with increased S-phase-specific chromosomal aberration after exposure to DNA-damaging agents, suggesting reduced homologous recombination (HR) repair as supported by the observation of decreased HR-related repair factor foci formation (RAD51 and BRCA1). Differentiated cells also had relatively increased fork stalling and R-loop formation after DNA replication stress. Treatment with NO donor (NOC-18), which causes stem cell differentiation has no effect on double-strand break (DSB) repair by non-homologous end-joining but reduced DSB repair by HR. Present studies suggest that DNA repair by HR is impaired in differentiated cells.

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Spontaneous and S-phase-specific chromosome aberrations in differentiated cells

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Higher frequency of residual γ-H2AX foci after exposure to DNA-damaging agents

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Higher frequency of cells with 53BP1 and RIF1 co-localization in differentiated cells

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Higher frequency of cells with a reduced number of RAD51 or BRCA1 foci

Contribution of the Microenvironmental Niche to Glioblastoma Heterogeneity

Glioblastoma is the most aggressive cancer of the brain. The dismal prognosis is largely attributed to the heterogeneous nature of the tumor, which in addition to intrinsic molecular and genetic changes is also influenced by the microenvironmental niche in which the glioma cells reside. The cancer stem cells (CSCs) hypothesis suggests that all cancers arise from CSCs that possess the ability to self-renew and initiate tumor formation. CSCs reside in specialized niches where interaction with the microenvironment regulates their stem cell behavior. The reciprocal interaction between glioma stem cells (GSCs) and cells from the microenvironment, such as endothelial cells, immune cells, and other parenchymal cells, may also promote angiogenesis, invasion, proliferation, and stemness of the GSCs and be likely to have an underappreciated role in their responsiveness to therapy. This crosstalk may also promote molecular transition of GSCs. Hence the inherent plasticity of GSCs can be seen as an adaptive response, changing according to the signaling cue from the niche. Given the association of GSCs with tumor recurrence and treatment sensitivity, understanding this bidirectional crosstalk between GSCs and its niche may provide a framework to identify more effective therapeutic targets and improve treatment outcome.

Sodium Nitroprusside Changed The Metabolism of Mesenchymal Stem Cells to An Anaerobic State while Viability and Proliferation Remained Intact

Objective

We used sodium nitroprusside (SNP), a nitric oxide (NO) releasing molecule, to understand its effect on viability and proliferation of rat bone marrow mesenchymal stem cells (BM-MSCs).

Materials and Methods

This experimental study evaluated the viability and morphology of MSCs in the presence of SNP (100 to 2000 µM) at 1, 5, and 15 hours. We chose the 100, 1000, and 2000 µM concentrations of SNP for one hour exposure for further analyses. Cell proliferation was investigated by the colony forming assay and population doubling number (PDN). Na⁺, K⁺, and Ca²⁺ levels as well as activities of lactate dehydrogenase (LDH), alkaline phosphatase (ALP), aspartate transaminase (AST), and alanine transaminase (ALT) were measured.

Results

The viability of MSCs dose-dependently reduced from 750 µM at one hour and 250 µM at 5 and 15 hours. The 100 µM caused no change in viability, however we observed a reduction in the cytoplasmic area at 5 and 15 hours. This change was not observed at one hour. The one hour treatment with 100 µM of SNP reduced the mean colony numbers but not the diameter when the cells were incubated for 7 and 14 days. In addition, one hour treatment with 100 µM of SNP significantly reduced ALT, AST, and ALP activities whereas the activity of LDH increased when incubated for 24 hours. The same treatment caused an increase in Ca²⁺ and reduction in Na⁺ content. The 1000 and 2000 µM concentrations reduced all the factors except Ca²⁺ and LDH which increased.

Conclusion

The high dose of SNP, even for a short time, was toxic. The low dose was safe with respect to viability and proliferation, especially over a short time. However elevated LDH activity might increase anaerobic metabolism.

NOTCH1-Dependent Nitric Oxide Signaling Deficiency in Hypoplastic Left Heart Syndrome Revealed Through Patient-Specific Phenotypes Detected in Bioengineered Cardiogenesis

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect (CHD) attributable to multifactorial molecular underpinnings. Multiple genetic loci have been implicated to increase the risk of disease, yet genotype-phenotype relationships remain poorly defined. Whole genome sequencing complemented by cardiac phenotype from five individuals in an HLHS-affected family enabled the identification of NOTCH1 as a prioritized candidate gene linked to CHD in three individuals with mutant allele burden significantly impairing Notch signaling in the HLHS-affected proband. To better understand a mechanistic basis through which NOTCH1 contributes to heart development, human induced pluripotent stem cells (hiPSCs) were created from the HLHS-affected parent-proband triad and differentiated into cardiovascular cell lineages for molecular characterization. HLHS-affected hiPSCs exhibited a deficiency in Notch signaling pathway components and a diminished capacity to generate hiPSC-cardiomyocytes. Optimization of conditions to procure HLHS-hiPSC-cardiomyocytes led to an approach that compensated for dysregulated nitric oxide (NO)-dependent Notch signaling in the earliest specification stages. Augmentation of HLHS-hiPSCs with small molecules stimulating NO signaling in the first 4 days of differentiation provided a cardiomyocyte yield equivalent to the parental hiPSCs. No discernable differences in calcium dynamics were observed between the bioengineered cardiomyocytes derived from the proband and the parents. We conclude that in vitro modeling with HLHS-hiPSCs bearing NOTCH1 mutations facilitated the discovery of a NO-dependent signaling component essential for cardiovascular cell lineage specification. Potentiation of NO signaling with small therapeutic molecules restored cardiogenesis in vitro and may identify a potential therapeutic target for patients affected by functionally compromised NOTCH1 variants. Stem Cells 2017;35:1106-1119.

Regulation of mitochondrial function and endoplasmic reticulum stress by nitric oxide in pluripotent stem cells

Mitochondrial dysfunction and endoplasmic reticulum stress (ERS) are global processes that are interrelated and regulated by several stress factors. Nitric oxide (NO) is a multifunctional biomolecule with many varieties of physiological and pathological functions, such as the regulation of cytochrome c inhibition and activation of the immune response, ERS and DNA damage; these actions are dose-dependent. It has been reported that in embryonic stem cells, NO has a dual role, controlling differentiation, survival and pluripotency, but the molecular mechanisms by which it modulates these functions are not yet known. Low levels of NO maintain pluripotency and induce mitochondrial biogenesis. It is well established that NO disrupts the mitochondrial respiratory chain and causes changes in mitochondrial Ca²⁺ flux that induce ERS. Thus, at high concentrations, NO becomes a potential differentiation agent due to the relationship between ERS and the unfolded protein response in many differentiated cell lines. Nevertheless, many studies have demonstrated the need for physiological levels of NO for a proper ERS response. In this review, we stress the importance of the relationships between NO levels, ERS and mitochondrial dysfunction that control stem cell fate as a new approach to possible cell therapy strategies.

A three-dimensional assemblage of gingiva-derived mesenchymal stem cells and NO-releasing microspheres for improved differentiation

Stem cell therapy is an attractive approach to bone tissue regeneration. Nitric oxide (NO) has been reported to facilitate osteogenic differentiation of stem cells. To enhance osteogenic differentiation of gingiva-derived mesenchymal stem cells (GMSCs), we designed a method for in situ delivery of exogenous NO to these cells. A NO donor, polyethylenimine/NONOate, was incorporated into poly(lactic-co-glycolic acid) microspheres to deliver NO to the cells for an extended period of time under in vitro culture conditions. A hybrid aggregate of GMSCs and NO-releasing microspheres was prepared by the hanging drop technique. Confocal microscopy revealed homogeneous arrangement of the stem cells and microspheres in heterospheroids. Western blot analysis and live-dead imaging showed no significant change in cell viability. Importantly, the in situ delivery of NO within the heterospheroids enhanced osteogenic differentiation indicated by a 1.2-fold increase in alkaline phosphatase activity and an approximately 10% increase in alizarin red staining. In addition, a low dose of NO promoted proliferation of the GMSCs in this 3D system. Thus, delivery of the NO-releasing microsphers to induce differentiation of stem cells within this three dimensional system may be one of possible strategies to direct differentiation of a stem cell-based therapeutic agent toward a specific lineage.

Effects of electromagnetic fields on osteoporosis: A systematic literature review

Electromagnetic fields (EMFs) as a safe, effective and noninvasive treatment have been researched and used for many years in orthopedics, and the common use clinically is to promote fracture healing. The effects of EMFs on osteoporosis have not been well concerned. The balance between osteoblast and osteoclast activity as well as the balance between osteogenic differentiation and adipogenic differentiation of bone marrow mesenchymal stem cells plays an important role in the process of osteoporosis. A number of recent reports suggest that EMFs have a positive impact on the balances. In this review, we discuss the recent advances of EMFs in the treatment of osteoporosis from basic research to clinical study and introduce the possible mechanism. In addition, we presented future perspectives of application of EMFs for osteoporosis.

Divergent modulation of normal and neoplastic stem cells by thrombospondin-1 and CD47 signaling

Thrombospondin-1 is a secreted matricellular protein that regulates the differentiation and function of many cell types. Thrombospondin-1 is not required for embryonic development, but studies using lineage-committed adult stem cells have identified positive and negative effects of thrombospondin-1 on stem cell differentiation and self-renewal and identified several thrombospondin-1 receptors that mediate these responses. Genetic studies in mice reveal a broad inhibitory role of thrombospondin-1 mediated by its receptor CD47. Cells and tissues lacking thrombospondin-1 or CD47 exhibit an increased capacity for self-renewal associated with increased expression of the stem cell transcription factors c-Myc, Sox2, Klf4, and Oct4. Thrombospondin-1 inhibits expression of these transcription factors in a CD47-dependent manner. However, this regulation differs in some neoplastic cells. Tumor initiating/cancer stem cells express high levels of CD47, but in contrast to nontransformed stem cells CD47 signaling supports cancer stem cells. Suppression of CD47 expression in cancer stem cells or ligation of CD47 by function blocking antibodies or thrombospondin-1 results in loss of self-renewal. Therefore, the therapeutic CD47 antagonists that are in clinical development for stimulating innate anti-tumor immunity may also inhibit tumor growth by suppressing cancer stem cells. These and other therapeutic modulators of thrombospondin-1 and CD47 signaling may also have applications in regenerative medicine to enhance the function of normal stem cells.

A Key Role of Autophagy in Osteoblast Differentiation on Titanium-Based Dental Implants

Autophagy plays an important role in embryogenesis, for the maintenance of tissue homeostasis and the elimination of damaged subcellular structures. Furthermore, autophagy could be a mode of physiological cell death and also be implicated in cell differentiation. Thus, we hypothesized that autophagy may have an impact on the differentiation of osteoblast cells influenced by various titanium-based surfaces. Interactions between smooth, commercially available pure titanium (Ti cp), rough Ticer, acid-etched Ti cp (SS) and M1-M3 (comprised of the monoclinic phase of sodium-titanium oxides and rutile; M2 contains amorphous calcium phosphates) and human osteoblast cells were investigated. Immunofluorescent staining was used for detecting autophagy, cell cluster formation and collagen type I (Col-1) expression. Flow cytometry was employed to identify autophagy, the production of endogenous nitric oxide (NO) and the size and granularity of the cells. Rough surfaces caused osteoblast differentiation via the autophagic-dependent PI3/Akt signalling pathway. These surfaces induced the formation of discrete populations of large, granular cells, i.e. mature osteoblasts. In addition, M1-M3 provoked the development of a third population of small, granular cells, responsible for cell cluster formation, which are important for the formation of bone noduli and mineralisation. The same surfaces induced faster osteoblast maturation and enhanced NO production, a hallmark of the already mentioned processes. Neither the mature osteoblasts nor the small cells appeared after the inhibition of autophagy. Inhibition of autophagy also prevented cell cluster formation. We demonstrate that autophagy plays an essential role in the osteoblast differentiation on titanium-based surfaces with rough topography.

[Preparation of rabbit monoclonal antibody against cGMP and development of competitive ELISA for cGMP]

OBJECTIVE

To prepare rabbit monoclonal antibody (RabMab) against guanosine 3', 5'-cyclic monophosphate (cGMP) and to develop a competitive ELISA for the detection of cGMP.

METHODS

New Zealand white rabbits were immunized with synthesized cGMP-keyhole limpet hemoeyanin (cGMP-KLH) to prepared a RabMAb with monoclonal antibody technique of Epitomics. A competitive ELISA kit was produced with cGMP RabMAb. The specificity, the precision and the recoveries of the method were determined.

RESULTS

The RabMAb with high sensitivity towards cGMP were prepared with an antibody timer of 3.1 ng/mL and 50% inhibitive concentration (IC50) of 12.57 ng/mL. The cGMP RabMAb had 33% cross-reactivity to inosine 3', 5'-cyclic monophosphate (cIMP) and little or no cross-reactivity to other compounds. A competitive ELISA was developed for detection of cGMP. The range of detection was 0~120 ng/mL with a minimal limit of 1.95 ng/mL. The recovery of assay was 89%~103%. The inter-assay and intra-assay coefficient variations were below 11.68% and 13.85%, respectively.

CONCLUSION

The RabMab against cGMP with high affinity and high specificity has been generated successfully, and a competitive ELISA for detection of cGMP has been developed with the prepared cGMP RabMAb.

Role of nitric oxide in the maintenance of pluripotency and regulation of the hypoxia response in stem cells

Stem cell pluripotency and differentiation are global processes regulated by several pathways that have been studied intensively over recent years. Nitric oxide (NO) is an important molecule that affects gene expression at the level of transcription and translation and regulates cell survival and proliferation in diverse cell types. In embryonic stem cells NO has a dual role, controlling differentiation and survival, but the molecular mechanisms by which it modulates these functions are not completely defined. NO is a physiological regulator of cell respiration through the inhibition of cytochrome c oxidase. Many researchers have been examining the role that NO plays in other aspects of metabolism such as the cellular bioenergetics state, the hypoxia response and the relationship of these areas to stem cell stemness.

Nitric oxide plays a role in stem cell niche homeostasis through its interaction with auxin

Nitric oxide (NO) is a unique reactive nitrogen molecule with an array of signaling functions that modulates plant developmental processes and stress responses. To explore the mechanisms by which NO modulates root development, we used a pharmacological approach and NO-deficient mutants to unravel the role of NO in establishing auxin distribution patterns necessary for stem cell niche homeostasis. Using the NO synthase inhibitor and Arabidopsis (Arabidopsis thaliana) NO biosynthesis mutants (nitric oxide-associated1 [noa1], nitrate reductase1 [nia1] and nia2, and nia1 nia2 noa1), we show that depletion of NO in noa1 reduces primary root elongation and increases flavonol accumulation consistent with elevated reactive oxygen species levels. The elevated flavonols are required for the growth effect, because the transparent testa4 mutation reverses the noa1 mutant root elongation phenotype. In addition, noa1 and nia1 nia2 noa1 NO-deficient mutant roots display small root meristems with abnormal divisions. Concomitantly, auxin biosynthesis, transport, and signaling are perturbed. We further show that NO accumulates in cortex/endodermis stem cells and their precursor cells. In endodermal and cortical cells, the noa1 mutant acts synergistically to the effect of the wuschel-related homeobox5 mutation on the proximal meristem, suggesting that NO could play an important role in regulating stem cell decisions, which has been reported in animals.

Slow and sustained nitric oxide releasing compounds inhibit multipotent vascular stem cell proliferation and differentiation without causing cell death

Atherosclerosis is the leading cause of cerebral and myocardial infarction. It is believed that neointimal growth common in the later stages of atherosclerosis is a result of vascular smooth muscle cell (SMC) de-differentiation in response to endothelial injury. However, the claims of the SMC de-differentiation theory have not been substantiated by monitoring the fate of mature SMCs in response to such injuries. A recent study suggests that atherosclerosis is a consequence of multipotent vascular stem cell (MVSC) differentiation. Nitric oxide (NO) is a well-known mediator against atherosclerosis, in part because of its inhibitory effect on SMC proliferation. Using three different NO-donors, we have investigated the effects of NO on MVSC proliferation. Results indicate that NO inhibits MVSC proliferation in a concentration dependent manner. A slow and sustained delivery of NO proved to inhibit proliferation without causing cell death. On the other hand, larger, single-burst NO concentrations, inhibits proliferation, with concurrent significant cell death. Furthermore, our results indicate that endogenously produced NO inhibits MVSC differentiation to mesenchymal-like stem cells (MSCs) and subsequently to SMC as well.

Curcumin induces differentiation of embryonic stem cells through possible modulation of nitric oxide-cyclic GMP pathway

Curcumin, an active ingredient of dietary spice used in curry, has been shown to exhibit anti-oxidant, anti-inflammatory and anti-proliferative properties. Using EB directed differentiation protocol of H-9 human embryonic stem (ES) cells; we evaluated the effect of curcumin (0-20 μmol/L) in enhancing such differentiation. Our results using real time PCR, western blotting and immunostaining demonstrated that curcumin significantly increased the gene expression and protein levels of cardiac specific transcription factor NKx2.5, cardiac troponin I, myosin heavy chain, and endothelial nitric oxide synthase during ES cell differentiation. Furthermore, an NO donor enhanced the curcumin-mediated induction of NKx2.5 and other cardiac specific proteins. Incubation of cells with curcumin led to a dose dependent increase in intracellular nitrite to the same extent as giving an authentic NO donor. Functional assay for second messenger(s) cyclic AMP (cAMP) and cyclic GMP (cGMP) revealed that continuous presence of curcumin in differentiated cells induced a decrease in the baseline levels of cAMP but it significantly elevated baseline contents of cGMP. Curcumin addition to a cell free assay significantly suppressed cAMP and cGMP degradation in the extracts while long term treatment of intact cells with curcumin increased the rates of cAMP and cGMP degradation suggesting that this might be due to direct suppression of some cyclic nucleotide-degrading enzyme (phosphodiesterase) by curcumin. These studies demonstrate that polyphenol curcumin may be involved in differentiation of ES cells partly due to manipulation of nitric oxide signaling.

Cell signaling and mitochondrial dynamics: Implications for neuronal function and neurodegenerative disease

Nascent evidence indicates that mitochondrial fission, fusion, and transport are subject to intricate regulatory mechanisms that intersect with both well-characterized and emerging signaling pathways. While it is well established that mutations in components of the mitochondrial fission/fusion machinery can cause neurological disorders, relatively little is known about upstream regulators of mitochondrial dynamics and their role in neurodegeneration. Here, we review posttranslational regulation of mitochondrial fission/fusion enzymes, with particular emphasis on dynamin-related protein 1 (Drp1), as well as outer mitochondrial signaling complexes involving protein kinases and phosphatases. We also review recent evidence that mitochondrial dynamics has profound consequences for neuronal development and synaptic transmission and discuss implications for clinical translation.