Evidence for the involvement of miRNA in redox regulated angiogenic response of human microvascular endothelial cells

miRNAs and their multifaceted role in cutaneous wound healing

The dynamic, complex process of cutaneous wound healing is required to restore skin integrity following an injury. This intricate process consists of four sequential and overlapping phases: hemostasis, inflammation, proliferation, and remodeling. Hemostasis immediately begins to function in response to vascular injury, forming a clot that stops the bleeding. To fight infection and remove debris, immune cells are enlisted during the inflammatory phase. Angiogenesis, re-epithelialization, and the creation of new tissue are all components of proliferation, whereas tissue maturation and scarring are the outcomes of remodeling. Chronic wounds, like those found in diabetic ulcers, frequently stay in a state of chronic inflammation because they are unable to go through these stages in a coordinated manner. The important regulatory roles that microRNAs (miRNAs) play in both normal and pathological wound healing have been highlighted by recent investigations. The miRNAs, small non-coding RNAs, modulate gene expression post-transcriptionally, profoundly impacting cellular functions. During the inflammatory phase, miRNAs control pro- and anti-inflammatory cytokines, as well as the activity of immune cells such as neutrophils and macrophages. Additionally, miRNAs are essential components of signaling networks related to inflammation, such as the toll-like receptor (TLR), nuclear factor kappa B (NF-kB), and Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathways. Some miRNAs have been discovered to either increase or alleviate inflammatory reactions, indicating their potential as therapeutic targets. Other miRNAs aid in angiogenesis by promoting the development of new blood vessels, which are essential for providing oxygen and nutrients to the healing tissue. They also affect keratinocyte migration and proliferation during the re-epithelialization phase, which involves growing new epithelial cells over the lesion. Another function of miRNAs is that they control the deposition of extracellular matrix (ECM) and the creation of scars during the remodeling phase. The abnormal expression of miRNAs in chronic wounds has led to the exploration of miRNA-based treatments. With a focus on resistant instances such as diabetic wounds, these therapeutic techniques seek to improve wound healing results by correcting the dysregulated miRNA expression.

Epigenetic Control of Redox Pathways in Cancer Progression

Significance: Growing evidence indicates the importance of redox reactions homeostasis, mediated predominantly by reactive oxygen species (ROS) in influencing the development, differentiation, progression, metastasis, programmed cell death, tumor microenvironment, and therapeutic resistance of cancer. Therefore, reviewing the ROS-linked epigenetic changes in cancer is fundamental to understanding the progression and prevention of cancer. Recent Advances: We review in depth the molecular mechanisms involved in ROS-mediated epigenetic changes that lead to alteration of gene expression by altering DNA, modifying histones, and remodeling chromatin and noncoding RNA. Critical Issues: In cancerous cells, alterations of the gene-expression regulatory elements could be generated by the virtue of imbalance in tumor microenvironment. Various oxidizing agents and mitochondrial electron transport chain are the major pathways that generate ROS. ROS plays a key role in carcinogenesis by activating pro-inflammatory signaling pathways and DNA damage. This loss of ROS-mediated epigenetic regulation of the signaling pathways may promote tumorigenesis. We address all such aspects in this review. Future Directions: Developments in this growing field of epigenetics are expected to contribute to further our understanding of human health and diseases such as cancer and to test the clinical applications of redox-based therapy. Recent studies of the cancer-epigenetic landscape have revealed pervasive deregulation of the epigenetic factors in cancer. Thus, the study of interaction between ROS and epigenetic factors in cancer holds a great promise in the development of effective and targeted treatment modalities. Antioxid. Redox Signal. 00, 000-000.

Redox signaling and skeletal muscle adaptation during aerobic exercise

Redox regulation is a fundamental physiological phenomenon related to oxygen-dependent metabolism, and skeletal muscle is mainly regarded as a primary site for oxidative phosphorylation. Several studies have revealed the importance of reactive oxygen and nitrogen species (RONS) in the signaling process relating to muscle adaptation during exercise. To date, improving knowledge of redox signaling in modulating exercise adaptation has been the subject of comprehensive work and scientific inquiry. The primary aim of this review is to elucidate the molecular and biochemical pathways aligned to RONS as activators of skeletal muscle adaptation and to further identify the interconnecting mechanisms controlling redox balance. We also discuss the RONS-mediated pathways during the muscle adaptive process, including mitochondrial biogenesis, muscle remodeling, vascular angiogenesis, neuron regeneration, and the role of exogenous antioxidants.

Coronary microvascular dysfunction

Coronary microvascular dysfunction (CMD) is a key mechanism underlying ischemic heart disease (IHD), yet its diagnosis and treatment remain challenging. This article presents a comprehensive overview of CMD research, covering its pathogenesis, diagnostic criteria, assessment techniques, risk factors, and therapeutic strategies. Additionally, it highlights the prospects for future CMD research. The article aims at advocating early and effective intervention for CMD and improving the prognosis of IHD.

Inducible miR-1224 silences cerebrovascular Serpine1 and restores blood flow to the stroke-affected site of the brain

The α-tocotrienol (TCT) form of natural vitamin E is more potent than the better known α-tocopherol against stroke. Angiographic studies of canine stroke have revealed beneficial cerebrovascular effects of TCT. This work seeks to understand the molecular basis of such effect. In mice, TCT supplementation improved perfusion at the stroke-affected site by inducing miR-1224. miRNA profiling of a laser-capture-microdissected stroke-affected brain site identified miR-1224 as the only vascular miR induced. Lentiviral knockdown of miR-1224 significantly blunted the otherwise beneficial effects of TCT on stroke outcomes. Studies on primary brain microvascular endothelial cells revealed direct angiogenic properties of miR-1224. In mice not treated with TCT, advance stereotaxic delivery of an miR-1224 mimic to the stroke site markedly improved stroke outcomes. Mechanistic studies identified Serpine1 as a target of miR-1224. Downregulation of Serpine1 augmented the angiogenic response of the miR-1224 mimic in the brain endothelial cells. The inhibition of Serpine1, by dietary TCT and pharmacologically, increased cerebrovascular blood flow at the stroke-affected site and protected against stroke. This work assigns Serpine1, otherwise known to be of critical significance in stroke, a cerebrovascular function that worsens stroke outcomes. miR-1224-dependent inhibition of Serpine1 can be achieved by dietary TCT as well as by the small-molecule inhibitor TM5441.

Molecular mechanisms behind ROS regulation in cancer: A balancing act between augmented tumorigenesis and cell apoptosis

ROS include hydroxyl radicals (HO.), superoxide (O2..), and hydrogen peroxide (H2O2). ROS are typically produced under physiological conditions and play crucial roles in living organisms. It is known that ROS, which are created spontaneously by cells through aerobic metabolism in mitochondria, can have either a beneficial or detrimental influence on biological systems. Moderate levels of ROS can cause oxidative damage to proteins, DNA and lipids, which can aid in the pathogenesis of many disorders, including cancer. However, excessive concentrations of ROS can initiate programmed cell death in cancer. Presently, a variety of chemotherapeutic drugs and herbal agents are being investigated to induce ROS-mediated cell death in cancer. Therefore, preserving ROS homeostasis is essential for ensuring normal cell development and survival. On account of a significant association of ROS levels at various concentrations with carcinogenesis in a number of malignancies, further studies are needed to determine the underlying molecular mechanisms and develop the possibilities for intervening in these processes.

A vicious circle in breast cancer: The interplay between inflammation, reactive oxygen species, and microRNAs

Breast cancer (BC) is the most common cancer in women worldwide. This highly heterogeneous disease is molecularly stratified into luminal A, luminal B, HER2, triple-negative/basal-like, and normal-like subtypes. An important aspect in BC progression is the activation of inflammatory processes. The activation of CD8+/Th1, NK, and M1 tumor associated macrophages (TAMs), leads to tumor destruction. In contrast, an anti-inflammatory response mediated by CD4+/Th2 and M2 TAMs will favor tumor progression. Inflammation also stimulates the production of inflammatory mediators like reactive oxygen species (ROS). In chronic inflammation, ROS activates oxidative stress and endothelial dysfunction. In cancer, ROS plays a dual role with anti-tumorigenic and pro-tumorigenic effects in cell signaling pathways that control proliferation, survival, apoptosis, and inflammation. MicroRNAs (miRNAs), which are known to be involved in BC progression and inflammation, can be regulated by ROS. At the same time, miRNAs regulate the expression of genes modulating oxidative stress. In this review, we will discuss the interplay between inflammation, ROS, and miRNAs as anticancer and tumor promoter molecules in BC. A clear understanding of the role of miRNAs in the regulation of ROS production and inflammation, may lead to new opportunities for therapy in BC.

NADPH-derived ROS generation drives fibrosis and endothelial-to-mesenchymal transition in systemic sclerosis: Potential cross talk with circulating miRNAs

Systemic sclerosis (SSc) is an immune disorder characterized by diffuse fibrosis and vascular abnormalities of the affected organs. Although the etiopathology of this disease is largely unknown, endothelial damage and oxidative stress appear implicated in its initiation and maintenance. Here, we show for the first time that circulating factors present in SSc sera increased reactive oxygen species (ROS) production, collagen synthesis, and proliferation of human pulmonary microvascular endothelial cells (HPMECs). The observed phenomena were also associated with endothelial to mesenchymal transition (EndMT) as indicated by decreased von Willebrand factor (vWF) expression and increased alpha-smooth muscle actin, respectively, an endothelial and mesenchymal marker. SSc-induced fibroproliferative effects were prevented by HPMECs exposition to the NADPH oxidase inhibitor diphenyleneiodonium, demonstrating ROS's causative role and suggesting their cellular origin. Sera from SSc patients showed significant changes in the expression of a set of fibrosis/EndMT-associated microRNAs (miRNA), including miR-21, miR-92a, miR-24, miR-27b, miR-125b, miR-29c, and miR-181b, which resulted significantly upregulated as compared to healthy donors sera. However, miR29b resulted downregulated in SSc sera, whereas no significant differences were found in the expression of miR-29a in the two experimental groups of samples. Taking together our data indicate NADPH oxidase-induced EndMT as a potential mechanism of SSc-associated fibrosis, suggesting fibrosis-associated miRNAs as potentially responsible for initiating and sustaining the vascular alterations observed in this pathological condition.

Epigenetics: key to improve delayed wound healing in type 2 diabetes

Diabetes-related delayed wound healing is a multifactorial, nuanced, and intertwined complication that causes substantial clinical morbidity. The etiology of diabetes and its related microvascular complications is affected by genes, diet, and lifestyle factors. Epigenetic modifications such as DNA methylation, histone modifications, and post-transcriptional RNA regulation (microRNAs) are subsequently recognized as key facilitators of the complicated interaction between genes and the environment. Current research suggests that diabetes-persuaded dysfunction of epigenetic pathways, which results in changed expression of genes in target cells and cause diabetes-related complications including cardiomyopathy, nephropathy, retinopathy, delayed wound healing, etc., which are foremost drivers to diabetes-related adverse outcomes. In this paper, we discuss the role of epigenetic mechanisms in controlling tissue repair, angiogenesis, and expression of growth factors, as well as recent findings that show the alteration of epigenetic events during diabetic wound healing.

Epigenetic basis of diabetic vasculopathy

Type 2 diabetes mellitus (T2DM) causes peripheral vascular disease because of which several blood-borne factors, including vital nutrients fail to reach the affected tissue. Tissue epigenome is sensitive to chronic hyperglycemia and is known to cause pathogenesis of micro- and macrovascular complications. These vascular complications of T2DM may perpetuate the onset of organ dysfunction. The burden of diabetes is primarily because of a wide range of complications of which nonhealing diabetic ulcers represent a major component. Thus, it is imperative that current research help recognize more effective methods for the diagnosis and management of early vascular injuries. This review addresses the significance of epigenetic processes such as DNA methylation and histone modifications in the evolution of macrovascular and microvascular complications of T2DM.

Cannabinoid-induced changes in the immune system: The role of microRNAs

Naturally occurring cannabinoids have been used by humans for their medicinal benefits for over several millennia. While the use of cannabinoids has been strictly regulated in the past century, easing of state regulations has been associated with an increase in use of cannabinoids in the United States. The potential therapeutic applications of cannabinoids have been explored and the anti-inflammatory effect of cannabis-derived cannabinoids has been well-documented. The pharmacological effects of cannabinoids are governed by the modulation of cannabinoid receptors, CB₁ and CB₂, expressed in the central and peripheral tissues. Moreover, growing scientific evidence suggests that the cannabinoid-mediated changes in the immune system involves change in expression of microRNAs (miRNAs). MiRNAs are short non-coding, single-stranded RNA which have the ability to affect post-translational regulation of gene expression. Studies over the past decade have investigated the changes in expression of miRNAs following treatment of various components of the immune system with different chemical modulators of the cannabinoid receptors. Such studies have highlighted the key role played by various miRNAs in driving the observed immunomodulatory effects of cannabinoids. The aim of this review article, therefore, is to summarize the role of miRNAs behind the observed effects of cannabinoids on the overall immune system, rather than focusing on a single disease state.

High Glucose Treatment Limits Drosha Protein Expression and Alters AngiomiR Maturation in Microvascular Primary Endothelial Cells via an Mdm2-dependent Mechanism

Diabetes promotes an angiostatic phenotype in the microvascular endothelium of skeletal muscle and skin. Angiogenesis-related microRNAs (angiomiRs) regulate angiogenesis through the translational repression of pro- and anti-angiogenic genes. The maturation of micro-RNA (miRs), including angiomiRs, requires the action of DROSHA and DICER proteins. While hyperglycemia modifies the expression of angiomiRs, it is unknown whether high glucose conditions alter the maturation process of angiomiRs in dermal and skeletal muscle microvascular endothelial cells (MECs). Compared to 5 mM of glucose, high glucose condition (30 mM, 6-24 h) decreased DROSHA protein expression, without changing DROSHA mRNA, DICER mRNA, or DICER protein in primary dermal MECs. Despite DROSHA decreasing, high glucose enhanced the maturation and expression of one angiomiR, miR-15a, and downregulated an miR-15a target: Vascular Endothelial Growth Factor-A (VEGF-A). The high glucose condition increased Murine Double Minute-2 (MDM2) expression and MDM2-binding to DROSHA. Inhibition of MDM2 prevented the effects evoked by high glucose on DROSHA protein and miR-15a maturation in dermal MECs. In db/db mice, blood glucose was negatively correlated with the expression of skeletal muscle DROSHA protein, and high glucose decreased DROSHA protein in skeletal muscle MECs. Altogether, our results suggest that high glucose reduces DROSHA protein and enhances the maturation of the angiostatic miR-15a through a mechanism that requires MDM2 activity.

Regulation of endothelial cell differentiation in embryonic vascular development and its therapeutic potential in cardiovascular diseases

During vertebrate development, the cardiovascular system begins operating earlier than any other organ in the embryo. Endothelial cell (EC) forms the inner lining of blood vessels, and its extensive proliferation and migration are requisite for vasculogenesis and angiogenesis. Many aspects of cellular biology are involved in vasculogenesis and angiogenesis, including the tip versus stalk cell specification. Recently, epigenetics has attracted growing attention in regulating embryonic vascular development and controlling EC differentiation. Some proteins that regulate chromatin structure have been shown to be directly implicated in human cardiovascular diseases. Additionally, the roles of important EC signaling such as vascular endothelial growth factor and its receptors, angiopoietin-1 and tyrosine kinase containing immunoglobulin and epidermal growth factor homology domain-2, and transforming growth factor-β in EC differentiation during embryonic vasculature development are briefly discussed in this review. Recently, the transplantation of human induced pluripotent stem cell (iPSC)-ECs are promising approaches for the treatment of ischemic cardiovascular disease including myocardial infarction. Patient-specific iPSC-derived EC is a potential new target to study differences in gene expression or response to drugs. However, clinical application of the iPSC-ECs in regenerative medicine is often limited by the challenges of maintaining cell viability and function. Therefore, novel insights into the molecular mechanisms underlying EC differentiation might provide a better understanding of embryonic vascular development and bring out more effective EC-based therapeutic strategies for cardiovascular diseases.

Antioxidant defense mechanisms and its dysfunctional regulation in the mitochondrial disease, Friedreich's ataxia

Redox stress is associated with the pathogenesis of a wide variety of disease states. This can be amplified potentially through redox active iron deposits in oxidatively active organelles such as the mitochondrion. There are a number of disease states, including Friedreich's ataxia (FA) and sideroblastic anemia, where iron metabolism is dysregulated and leads to mitochondrial iron accumulation. Considering FA, which is due to the decreased expression of the mitochondrial protein, frataxin, this iron accumulation does not occur within protective storage proteins such as mitochondrial ferritin. Instead, it forms unbound biomineral aggregates composed of high spin iron(III), phosphorous and sulfur, which probably contributes to the observed redox stress. There is also a dysregulated response to the ensuing redox assault, as the master regulator of oxidative stress, nuclear factor erythroid 2-related factor-2 (Nrf2), demonstrates marked down-regulation. The dysfunctional response of Nrf2 in FA is due to multiple mechanisms including: (1) up-regulation of Keap1 that is involved in Nrf2 degradation; (2) activation of the nuclear Nrf2 export/degradation machinery via glycogen synthase kinase-3β (Gsk3β) signaling; and (3) inhibited nuclear translocation of Nrf2. More recently, increased microRNA (miRNA) 144 expression has been demonstrated to down-regulate Nrf2 in several disease states, including an animal model of FA. Other miRNAs have also demonstrated to be dysregulated upon frataxin depletion in vivo in humans and animal models of FA. Collectively, frataxin depletion results in multiple, complex responses that lead to detrimental redox effects that could contribute to the mechanisms involved in the pathogenesis of FA.

Cross-talk between oxidative stress signaling and microRNA regulatory systems in carcinogenesis: Focused on gastrointestinal cancers

Molecular mechanisms underlying development and progression of gastrointestinal (GI) cancers are mediated by both oxidative stress (OS) and microRNAs (miRNAs) involvement. Notably, OS signaling may regulate the expression of miRNAs, and miRNAs function as imperative players in OS-initiated tumors. Given the defined biological roles of both OS systems and miRNAs in GI carcinogenesis, a possible interplay between these two key cellular networks is considered. A growing body of evidence has indicated a reciprocal connection between OS signaling pathways and miRNA regulatory machines in GI cancer development and progression. Illumination of the molecular cross-talking between miRNAs and the OS would improve our pathophysiological insight into carcinogens. Also, understanding the molecular mechanisms in which these systems are reciprocally regulated may imply in future medical practice mainly GI cancer therapy. Nowadays, therapeutic strategies focusing on miRNA and OS in GI cancer treatment are increasingly delineated. Since the use of antioxidants is limited owing to the contrasting consequences of OS signaling in cancer, the discovery of OS-responsive miRNAs may provide a potential new strategy to overcome OS-mediated GI carcinogenesis. Given the possible interaction between OS and miRNAs in GI cancers, this review aimed to elucidate the existing evidence on the interaction between OS and miRNA regulatory machinery and its role in GI carcinogenesis. In this regard, we will illustrate the function of miRNAs which target OS systems during homeostasis and tumorigenesis. We also discuss the biological cross-talk between OS systems and miRNAs and corresponding cell signaling pathways.

Exploring microRNAs in diabetic chronic cutaneous ulcers: Regulatory mechanisms and therapeutic potential

Diabetic chronic cutaneous ulcers (DCU) are one of the serious complications of diabetes mellitus, occurring mainly in diabetic patients with peripheral neuropathy. Recent studies have indicated that microRNAs (miRNAs/miRs) and their target genes are essential regulators of cell physiology and pathology including biological processes that are involved in the regulation of diabetes and diabetes-related microvascular complications. in vivo and in vitro models have revealed that the expression of some miRNAs can be regulated in the inflammatory response, cell proliferation, and wound remodelling of DCU. Nevertheless, the potential application of miRNAs to clinical use is still limited. Here, we provide a contemporary overview of the miRNAs as well as their associated target genes and pathways (including Wnt/β-catenin, NF-κB, TGF-β/Smad, and PI3K/AKT/mTOR) related to DCU healing. We also summarize the current development of drugs for DCU treatment and discuss the therapeutic challenges of DCU treatment and its future research directions.

MicroRNA Targeting Nicotinamide Adenine Dinucleotide Phosphate Oxidases in Cancer

Significance: Reactive oxygen species (ROS) production occurs primarily in the mitochondria as a by-product of cellular metabolism. ROS are also produced by nicotinamide adenine dinucleotide phosphate (NADPH) oxidases in response to growth factors and cytokines by normal physiological signaling pathways. NADPH oxidase, a member of NADPH oxidase (NOX) family, utilizes molecular oxygen (O2) to generate ROS such as hydrogen peroxide and superoxide. Imbalance between ROS production and its elimination is known to be the major cause of various human diseases. NOX family proteins are exclusively involved in ROS production, which makes them attractive target(s) for the treatment of ROS-mediated diseases including cancer. Recent Advances: Molecules such as Keap1/nuclear factor erythroid 2-related factor 2 (Nrf2), N-methyl-d-aspartic acid (NMDA) receptors, nuclear factor-kappaB, KRAS, kallistatin, gene associated with retinoic-interferon-induced mortality-19, and deregulated metabolic pathways are involved in ROS production in association with NADPH oxidase. Critical Issues: Therapeutic strategies targeting NADPH oxidases in ROS-driven cancers are not very effective due to its complex regulatory circuit. Tumor suppressor microRNAs (miRNAs) viz. miR-34a, miR-137, miR-99a, and miR-21a-3p targeting NADPH oxidases are predominantly downregulated in ROS-driven cancers. miRNAs also regulate other cellular machineries such as Keap1/Nrf2 pathway and NMDA receptors involved in ROS production and consequently drug resistance. Here, we discuss the structure, function, and metabolic role of NADPH oxidase, NOX family protein-protein interaction, their association with other pathways, and NADPH oxidase alteration by miRNAs. Moreover, we also discuss and summarize studies on NADPH oxidase associated with various malignancies and their therapeutic implications. Future Directions: Targeting NADPH oxidases through miRNAs appears to be a promising strategy for the treatment of ROS-driven cancer.

Redox Regulation of the Microcirculation

The microcirculation maintains tissue homeostasis through local regulation of blood flow and oxygen delivery. Perturbations in microvascular function are characteristic of several diseases and may be early indicators of pathological changes in the cardiovascular system and in parenchymal tissue function. These changes are often mediated by various reactive oxygen species and linked to disruptions in pathways such as vasodilation or angiogenesis. This overview compiles recent advances relating to redox regulation of the microcirculation by adopting both cellular and functional perspectives. Findings from a variety of vascular beds and models are integrated to describe common effects of different reactive species on microvascular function. Gaps in understanding and areas for further research are outlined. © 2020 American Physiological Society. Compr Physiol 10:229-260, 2020.

The Yin-Yang Regulation of Reactive Oxygen Species and MicroRNAs in Cancer

Reactive oxygen species (ROS) are highly reactive oxygen-containing chemical species formed as a by-product of normal aerobic respiration and also from a number of other cellular enzymatic reactions. ROS function as key mediators of cellular signaling pathways involved in proliferation, survival, apoptosis, and immune response. However, elevated and sustained ROS production promotes tumor initiation by inducing DNA damage or mutation and activates oncogenic signaling pathways to promote cancer progression. Recent studies have shown that ROS can facilitate carcinogenesis by controlling microRNA (miRNA) expression through regulating miRNA biogenesis, transcription, and epigenetic modifications. Likewise, miRNAs have been shown to control cellular ROS homeostasis by regulating the expression of proteins involved in ROS production and elimination. In this review, we summarized the significance of ROS in cancer initiation, progression, and the regulatory crosstalk between ROS and miRNAs in cancer.

Downregulation of microRNA-103a reduces microvascular endothelial cell injury in a rat model of cerebral ischemia by targeting AXIN2

Multiple microRNAs (miRNAs) have been found to be linked with cerebral ischemia. Thus, this study was employed to characterize the capabilities of miRNA-103a (miR-103a) on the brain microvascular endothelial cells (BMECs) injury in rat models of middle cerebral artery occlusion (MCAO) by regulating AXIN2. The MCAO rat model was developed by the suture method, where normal saline, miR-103a inhibitors, or its negative control were separately injected into the lateral ventricle to assess the function of miR-103a inhibitors in BMECs apoptosis, microvessel density, as well as angiogenesis. In addition, the oxygen-glucose deprivation model was induced in primarily cultured BMECs to unearth the functions of miR-103a inhibitors on cell viability and apoptosis, lactate dehydrogenase (LDH) release and tube formation ability. Furthermore, the relationship between miR-103a and AXIN2 was verified. The modeled rats of MCAO showed robustly expressed miR-103a, poorly expressed AXIN2, severe neurological deficits, accelerated apoptosis and reduced angiogenesis. miR-103a expression had a negative correlation with AXIN2 messenger RNA expression (r = -0.799; p < .05). In response to the treatment of miR-103a inhibitors, the BMECs apoptosis was suppressed and angiogenesis was restored, corresponding to upregulated Bcl-2, VEGF, and Ang-1, in addition to downregulated caspase-3 and Bax. Meanwhile, AXIN2 was verified to be the miR-103a's target gene. More important, miR-103a inhibitors led to promoted BMEC viability and tube formation and suppressed apoptosis and LDH release rate. This study highlights that miR-103a targets and negatively regulates AXIN2, whereby reducing BMEC injury in cerebral ischemia.

MicroRNA Networks Modulate Oxidative Stress in Cancer

Imbalanced regulation of reactive oxygen species (ROS) and antioxidant factors in cells is known as "oxidative stress (OS)". OS regulates key cellular physiological responses through signal transduction, transcription factors and noncoding RNAs (ncRNAs). Increasing evidence indicates that continued OS can cause chronic inflammation, which in turn contributes to cardiovascular and neurological diseases and cancer development. MicroRNAs (miRNAs) are small ncRNAs that produce functional 18-25-nucleotide RNA molecules that play critical roles in the regulation of target gene expression by binding to complementary regions of the mRNA and regulating mRNA degradation or inhibiting translation. Furthermore, miRNAs function as either tumor suppressors or oncogenes in cancer. Dysregulated miRNAs reportedly modulate cancer hallmarks such as metastasis, angiogenesis, apoptosis and tumor growth. Notably, miRNAs are involved in ROS production or ROS-mediated function. Accordingly, investigating the interaction between ROS and miRNAs has become an important endeavor that is expected to aid in the development of effective treatment/prevention strategies for cancer. This review provides a summary of the essential properties and functional roles of known miRNAs associated with OS in cancers.

Reactive Oxygen Species Drive Epigenetic Changes in Radiation-Induced Fibrosis

Radiation-induced fibrosis (RIF) develops months to years after initial radiation exposure. RIF occurs when normal fibroblasts differentiate into myofibroblasts and lay down aberrant amounts of extracellular matrix proteins. One of the main drivers for developing RIF is reactive oxygen species (ROS) generated immediately after radiation exposure. Generation of ROS is known to induce epigenetic changes and cause differentiation of fibroblasts to myofibroblasts. Several antioxidant compounds have been shown to prevent radiation-induced epigenetic changes and the development of RIF. Therefore, reviewing the ROS-linked epigenetic changes in irradiated fibroblast cells is essential to understand the development and prevention of RIF.

Stressing the (Epi)Genome: Dealing with Reactive Oxygen Species in Cancer

SIGNIFICANCE

Growing evidence indicates cross-talk between reactive oxygen species (ROS) and several key epigenetic processes such as DNA methylation, histone modifications, and miRNAs in normal physiology and human pathologies including cancer. This review focuses on how ROS-induced oxidative stress, metabolic intermediates, and epigenetic processes influence each other in various cancers. Recent Advances: ROS alter chromatin structure and metabolism that impact the epigenetic landscape in cancer cells. Several site-specific DNA methylation changes have been identified in different cancers and are discussed in the review. We also discuss the interplay of epigenetic enzymes and miRNAs in influencing malignant transformation in an ROS-dependent manner.

CRITICAL ISSUES

Loss of ROS-mediated signaling mostly by epigenetic regulation may promote tumorigenesis. In contrast, augmented oxidative stress because of high ROS levels may precipitate epigenetic alterations to effect various phases of carcinogenesis. We address both aspects in the review.

FUTURE DIRECTIONS

Several drugs targeting ROS are under various stages of clinical development. Recent analysis of human cancers has revealed pervasive deregulation of the epigenetic machinery. Thus, a better understanding of the cross-talk between ROS and epigenetic alterations in cancer could lead to the identification of new drug targets and more effective treatment modalities.

Redox Regulation and Noncoding RNAs

SIGNIFICANCE

RNA is a heterogeneous class of molecules with the minority being protein coding. Noncoding RNAs (ncRNAs) are involved in translation and epigenetic control mechanisms of gene expression. Recent Advances: In recent years, the number of identified ncRNAs has dramatically increased and it is now clear that ncRNAs provide a complex layer of differential gene expression control.

CRITICAL ISSUES

NcRNAs exhibit interplay with redox regulation. Redox regulation alters the expression of ncRNAs; conversely, ncRNAs alter the expression of generator and effector systems of redox regulation in a complex manner, which will be the focus of this review article.

FUTURE DIRECTIONS

Understanding the role of ncRNA in redox control will lead to the development of new strategies to alter redox programs. Given that many ncRNAs (particularly microRNAs [miRNAs]) change large gene sets, these molecules are attractive drug candidates; already, now miRNAs can be targeted in patients. Therefore, the development of ncRNA therapies focusing on these molecules is an attractive future strategy. Antioxid. Redox Signal. 29, 793-812.

MicroRNAs in the skin: role in development, homoeostasis and regeneration

The skin is the largest organ of the integumentary system and possesses a vast number of functions. Due to the distinct layers of the skin and the variety of cells which populate each, a tightly regulated network of molecular signals control development and regeneration, whether due to programmed cell termination or injury. MicroRNAs (miRs) are a relatively recent discovery; they are a class of small non-coding RNAs which possess a multitude of biological functions due to their ability to regulate gene expression via post-transcriptional gene silencing. Of interest, is that a plethora of data demonstrates that a number of miRs are highly expressed within the skin, and are evidently key regulators of numerous vital processes to maintain non-aberrant functioning. Recently, miRs have been targeted as therapeutic interventions due to the ability of synthetic 'antagomiRs' to down-regulate abnormal miR expression, thereby potentiating wound healing and attenuating fibrotic processes which can contribute to disease such as systemic sclerosis (SSc). This review will provide an introduction to the structure and function of the skin and miR biogenesis, before summarizing the literature pertaining to the role of miRs. Finally, miR therapies will also be discussed, highlighting important future areas of research.

Circulating progenitor cells in hypertensive subjects: Effectiveness of a treatment with olmesartan in improving cell number and miR profile in addition to expected pharmacological effects

CD34+ circulating progenitor cells (CD34+CPCs) are a population of multipotent cells which can delay the development of atherosclerosis and cardiovascular disease (CVD) in conditions of increased CV risk. MicroRNAs (miRs) 221 and 222 modulate different genes regulating angiogenesis and inflammation; moreover, miR221/22 have beenshown to participate in differentiation and proliferation of CD34+CPCs, inhibiting cell migration and homing. miR221/222 in CD34+CPCs from hypertensive subjects are also increased and associated with CD34+cell number and reactive oxygen species (ROS). We evaluated CD34+CPC number, intracellular miR221/222 and ROS levels, arterial stiffness (AS)and echocardiography indices at baseline (T0).Then, after a six-month treatment with olmesartan, 20 mg/day (T1), in 57 hypertensive patients with left ventricular hypertrophy (LVH) and with no additional risk factor for CVD, and in 29 healthy controls (baseline),fibrinogen, C-reactive protein (CRP), glucose and lipid profiles were also evaluated.At T1, blood pressure values, CRP and fibrinogen levels, ROS and miR221/222 were significantly decreased (all p <0.001), as were AS indices and LV mass index (p<0.001), while cell number was increased (p<0.001). Olmesartan is effective in reducing miR and ROS levels in CD34+CPCs from hypertensive subjects, as well as in increasing CD34+CPC number, providing multilevel CV protection, in addition to its expected pharmacological effects.

MicroRNAs as regulators of endothelial cell functions in cardiometabolic diseases

Endothelial cells (ECs) provide nutrients and oxygen essential for tissue homeostasis. Metabolic imbalances and other environmental stimuli, like cytokines or low shear stress, trigger endothelial inflammation, increase permeability, compromise vascular tone, promote cell proliferation, and ultimately cause cell death. These factors contribute to EC dysfunction, which is crucial in the development of cardiometabolic diseases. microRNAs (miRNAs) are small non-coding RNAs that have important functions in the regulation of ECs. In the present review, we discuss the role of miRNAs in various aspects of EC pathology in cardiometabolic diseases like atherosclerosis, type 2 diabetes, obesity, and the metabolic syndrome, and in complication of those pathologies, like ischemia. We also discuss the potential therapeutic applications of miRNAs in promoting angiogenesis and neovascularization in tissues where the endothelium is damaged in different cardiometabolic diseases. This article is part of a Special Issue entitled: MicroRNAs and lipid/energy metabolism and related diseases edited by Carlos Fernández-Hernando and Yajaira Suárez.

miRNA in Macrophage Development and Function

SIGNIFICANCE

MicroRNAs (miRNAs) control cellular gene expression via primarily binding to 3' or 5' untranslated region of the target transcript leading to translational repression or mRNA degradation. In most cases, miRNAs have been observed to fine-tune the cellular responses and, therefore, act as a rheostat rather than an on/off switch. Transcription factor PU.1 is a master switch that controls monocyte/macrophage development from hematopoietic stem cells. Recent Advances: PU.1 induces a specific set of miRNAs while suppressing the miR17-92 cluster to regulate monocyte/macrophage development. In addition to development, miRNAs tightly control the macrophage polarization continuum from proinflammatory M1 or proreparative M2 by regulating expression of key transcription factors involved in the process of polarization.

CRITICAL ISSUES

miRNAs are intricately involved with fine-tuning fundamental macrophage functions such as phagocytosis, efferocytosis, inflammation, tissue repair, and tumor promotion. Macrophages are secretory cells that participate in intercellular communication by releasing regulatory molecules and microvesicles (MVs). MVs are bilayered lipid membranes packaging a hydrophilic cargo, including proteins and nucleic acids. Macrophage-derived MVs carry functionally active miRNAs that suppress gene expression in target cells via post-transcriptional gene silencing, thus regulating cell function. In summary, miRNAs fine-tune several major facets of macrophage development and function. Such fine-tuning is critical in preventing exaggerated macrophage response to endogenous or exogenous stimuli.

FUTURE DIRECTIONS

A critical role of miRNAs in the regulation of innate immune response and macrophage biology, including development, differentiation, and activation, has emerged. A clear understanding of such regulation on macrophage function remains to be elucidated. Antioxid. Redox Signal. 25, 795-804.

Correction of MFG-E8 Resolves Inflammation and Promotes Cutaneous Wound Healing in Diabetes

Milk fat globule epidermal growth factor-factor 8 (MFG-E8) is a peripheral glycoprotein that acts as a bridging molecule between the macrophage and apoptotic cells, thus executing a pivotal role in the scavenging of apoptotic cells from affected tissue. We have previously reported that apoptotic cell clearance activity or efferocytosis is compromised in diabetic wound macrophages. In this work, we test the hypothesis that MFG-E8 helps resolve inflammation, supports angiogenesis, and accelerates wound closure. MFG-E8(-/-) mice displayed impaired efferocytosis associated with exaggerated inflammatory response, poor angiogenesis, and wound closure. Wound macrophage-derived MFG-E8 was recognized as a critical driver of wound angiogenesis. Transplantation of MFG-E8(-/-) bone marrow to MFG-E8(+/+) mice resulted in impaired wound closure and compromised wound vascularization. In contrast, MFG-E8(-/-) mice that received wild-type bone marrow showed improved wound closure and improved wound vascularization. Hyperglycemia and exposure to advanced glycated end products inactivated MFG-E8, recognizing a key mechanism that complicates diabetic wound healing. Diabetic db/db mice suffered from impaired efferocytosis accompanied with persistent inflammation and slow wound closure. Topical recombinant MFG-E8 induced resolution of wound inflammation, improvements in angiogenesis, and acceleration of closure, upholding the potential of MFG-E8-directed therapeutics in diabetic wound care.

The Pleiotropic Effects of miRNAs on Tumor Angiogenesis

Angiogenesis, the process of new blood vessel formation and growth from already existing venules is critical in vascular development and homeostasis controlled by the balance of pro- and anti-angiogenic factors. Emerging evidence indicates the development, progression, and metastasis of various human cancers are strongly relied on angiogenesis. However, molecular mechanisms that underlie the complex regulation of angiogenic processes are still not fully elucidated. Recent studies revealed that microRNAs (miRNAs) were important regulators of tumor angiogenesis and the entire research in this area has entered into a so-called "miRNAs era." Thus, miRNAs might be important therapeutic targets or biomarkers for cancer. Due to the complexity of miRNA regulating mechanisms, how specific miRNAs intersect with and modulate tumor angiogenesis is still unclear. The conflicting results of the same miRNAs from different groups indicated that miRNAs might possess potent activity in a cell type or cell context specific manner. Here, we present a summary of latest advances in understanding the roles of angiogenic miRNAs as potential tools or targets in cancer therapy.

Interplay between Reactive oxygen Species and MicroRNAs in Cancer

Since both reactive oxygen species (ROS) production and microRNAs expression signature have been associated with tumor development, progression, metastasis and therapeutic response, it is important to understand the crosstalk between ROS and microRNAs. Indeed, growing evidence suggests a reciprocal connection between ROS signaling and microRNAs pathway, resulting in diverse biological effects in cancer cells. In this mini review, we discussed the ROS-responsive microRNAs that have implications in cancer and the possible mechanisms in which ROS regulate microRNAs. We also highlighted the microRNAs which are able to modify cellular ROS homeostasis during tumorigenesis, their biological targets and subsequent functions. As the use of antioxidants is limited due to the diverse or even opposing roles of ROS signaling in cancer, the discovery of ROS-responsive microRNAs provides a potential new strategy to specifically overcome ROS-mediated tumor progression or benefit from ROS-induced apoptosis.

MicroRNAs in congenital heart disease

Congenital heart disease (CHD) is a broad term which encompasses a spectrum of pathology, the most common phenotypes include atrial septal defects (ASDs), ventricular septal defects (VSDs), patent ductus arteriosus (PAD) and tetralogy of Fallot (TOF). The impact of CHD is profound and it is estimated to be responsible for over 40% of prenatal deaths. MicroRNAs (miRs) are small, highly conserved, non-coding RNAs which have complex roles in a variety of pathophysiological states. miRs are post-transcriptional negative regulators of gene expression. Individual miRs are known to exert effects in multiple target genes, therefore the altered expression of a single miR could influence an entire gene network resulting in complex pathological states. Recent evidences suggest a role in the dysregulation of miRs in CHD. Mouse knock out models have contributed to our knowledge base revealing specific patterns of miR expression in cardiovascular physiology and pathological states. Specific miRs necessary for embryonic cardiac development have been revealed. Dysregulation of these miRs has been shown to cause structural abnormalities in the heart and vasculature, thus furthering our understanding of the processes which result in CHD. These advances have provided new insight into the signalling pathways responsible for CHD. Furthermore, this new appreciation for miRs in the development of CHD has uncovered their potential for new therapeutic targets where modulated miR activity may reduce the burden of disease. Here, we summarize current knowledge of the cause-effect relationships of miRs in CHD and consider their potential as a therapeutic targets and biomarkers in this clinical setting.

Noncoding RNAs in Tumor Angiogenesis

Solid tumors require angiogenesis to grow beyond 2 mm in size. In most cases, tumor cells undergo angiogenic switch and secrete substances that are required for generation of new capillary sprouting from existing blood vessels. Tumor angiogenesis is driven by a complex interplay between pro-angiogenic (VEGF/VEGFR, PDGF/PDGFR) and anti-angiogenic factors (TSP-1/TSP-2) within the tumor microenvironment. In addition, control of tissue remodeling and degradation by matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) contribute to tumor angiogenesis. Furthermore, tumor suppressors or oncogenes that control cellular motility and maintain or promote hypoxia (HIFs and MYC) are also actively playing roles in tumor angiogenesis. Noncoding RNAs (ncRNAs), including microRNAs, are a novel class of regulatory molecules that control the gene expression in a posttranscriptional manner. MicroRNAs regulate important physiological processes, such as proliferation, apoptosis, and differentiation, as well as pathological conditions including oncogenesis. Accumulating evidence suggests that microRNAs directly modulate the process of angiogenesis by targeting important angiogenic factors and signaling molecules. Understanding the molecular mechanism behind the regulation of angiogenesis by microRNAs is important due to their therapeutic potential which may lead to improving outcome for cancer patients. Besides, ncRNAs with a regulatory role in angiogenesis, such as long noncoding RNAs (lncRNAs), have been identified in the genome. However, the mechanisms of the vast majority of lncRNAs are currently unknown. For the few lncRNAs characterized at the functional level, accumulating evidence shows that they play important roles in malignant diseases. The function and mechanism in angiogenesis will be described in this chapter.

AngiomiRs: Potential Biomarkers of Pregnancy's Vascular Pathologies

In recent years, microRNAs (miRNAs) have been the focus of research for their role in posttranscriptional regulation and as potential biomarkers of risk for disease development. Their identification in specific physiological processes, like angiogenesis, a key pathway in placental vascular development in pregnancy, suggests an important role of miRNAs that regulate angiogenesis (angiomiRs). Many complications of pregnancy have in common placental vascular alterations, involving an imbalance in the angiogenesis process in the development of conditions such as preeclampsia, intrauterine growth restriction, and gestational diabetes, complications with the highest rates of morbimortality in pregnancy. Many studies have identified angiomiRs with differential expression profiles in each of these diseases; however, this evidence requires further studies focused on evaluating their potential as biomarkers of risk for the angiomiRs detected, to establish correlations between placental tissue and serum/plasma expression profiles. Therefore, the objective of this review is to highlight the best angiomiRs detected in placental tissue and serum/plasma in each of these three pathologies to show the current data available for potential biomarkers and to propose future research strategies on this topic.

MicroRNAs in tumor angiogenesis

As it is necessary for tumor growth, angiogenesis has been an attractive target for drug therapy. Accumulating evidences indicate that microRNAs (miRNAs), which are short non-coding RNAs, delicately regulate the angiogenic signals through targeting angiogenic factors and protein kinases. They can modulate pro-angiogenic signals induced by vascular endothelial growth factor (VEGF) and anti-angiogenic signals induced by thrombospondin-1 (TSP-1), and therefore promote or inhibit tumor angiogenesis. Receptor tyrosine kinases (RTKs) and hypoxia inducible factor (HIF) are also targeted by miRNAs. Moreover, miRNAs crosstalk with reactive oxygen species (ROS) influencing tumor angiogenesis. It is critical to understand the role of miRNAs in tumor angiogenesis due to their therapeutic potential to improve outcome for cancer patients. The following review discusses the current state of knowledge related to tumor angiogenesis-regulatory miRNAs and their targets.

MicroRNA-19b/221/222 induces endothelial cell dysfunction via suppression of PGC-1α in the progression of atherosclerosis

BACKGROUND

Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is a master regulator of cellular energy metabolism that is associated with many cardiovascular diseases, including atherosclerosis. However, the role and underling regulatory mechanisms of PGC-1α in the pathogenesis of atherosclerosis are not completely understood. Here, we identified the microRNAs that post-transcriptionally regulate PGC-1α production and their roles in the pathogenesis of atherosclerosis.

METHODS AND RESULTS

A significant down-regulation of PGC-1α protein was observed in human atherosclerotic vessel samples. Using microarray and bioinformatics analyses, PGC-1α was identified as a common target gene of miR-19b-3p, miR-221-3p and miR-222-3p, which are mainly located in the intima of atherosclerotic vessels. In vitro induction of miR-19b-3p, miR-221-3p and miR-222-3p by the inflammatory cytokines TNFα and IFNγ may affect PGC-1α protein production and consequently result in mitochondrial dysfunction in Human Aortic Endothelial Cells (HAECs). The overexpression of miR-19b-3p, miR-221-3p and miR-222-3p in HAECs caused intracellular ROS accumulation, which led to cellular apoptosis.

CONCLUSION

Taken together, these results demonstrate that PGC-1α plays a protective role against the vascular complications of atherosclerosis. Moreover, the posttranscriptional regulation of PGC-1α by miR-19b/221/222 was unveiled, which provides a novel mechanism in which a panel of microRNAs can modulate endothelial cell apoptosis via the regulation mitochondrial function.

microRNA-200b as a Switch for Inducible Adult Angiogenesis

SIGNIFICANCE

Angiogenesis is the process by which new blood vessels develop from a pre-existing vascular system. It is required for physiological processes such as developmental biology and wound healing. Angiogenesis also plays a crucial role in pathological conditions such as tumor progression. The underlying importance of angiogenesis necessitates a highly regulated process.

RECENT ADVANCES

Recent works have demonstrated that the process of angiogenesis is regulated by small noncoding RNA molecules called microRNAs (miRs). These miRs, collectively referred to as angiomiRs, have been reported to have a profound effect on the process of angiogenesis by acting as either pro-angiogenic or anti-angiogenic regulators.

CRITICAL ISSUES

In this review, we will discuss the role of miR-200b as a regulator of angiogenesis. Once the process of angiogenesis is complete, anti-angiogenic miR-200b has been reported to provide necessary braking. Downregulation of miR-200b has been reported across various tumor types, as deregulated angiogenesis is necessary for tumor development. Transient downregulation of miR-200b in wounds drives wound angiogenesis.

FUTURE DIRECTIONS

New insights and understanding of the molecular mechanism of regulation of angiogenesis by miR-200b has opened new avenues of possible therapeutic interventions to treat angiogenesis-related patho-physiological conditions. Antioxid. Redox Signal. 22, 1257-1272.

Oxidized high-density lipoprotein impairs endothelial progenitor cells' function by activation of CD36-MAPK-TSP-1 pathways

AIMS

High-density lipoprotein (HDL) levels inversely correlate with cardiovascular events due to the protective effects on vascular wall and stem cells, which are susceptible to oxidative modifications and then lead to potential pro-atherosclerotic effects. We proposed that oxidized HDL (ox-HDL) might lead to endothelial progenitor cells (EPCs) dysfunction and investigated underlying mechanisms.

RESULTS

ox-HDL was shown to increase apoptosis and intracellular reactive oxygen species levels, but to reduce migration, angiogenesis, and cholesterol efflux of EPCs in a dose-dependent manner. p38 mitogen-activated protein kinase (MAPK) and NF-κB were activated after ox-HDL stimulation, which also upregulated thrombospondin-1 (TSP-1) expression without affecting vascular endothelial growth factor. Effects caused by ox-HDL could be significantly attenuated by pretreatment with short hairpin RNA-mediated CD36 knockdown or probucol. Data of in vivo experiments and the inverse correlation of ox-HDL and circulating EPC numbers among patients with coronary artery diseases (CAD) or CAD and type 2 diabetes also supported it. Meanwhile, HDL separated from such patients could significantly increase cultured EPC's caspase 3 activity, further supporting our proposal.

INNOVATION

This is the most complete study to date of how ox-HDL would impair EPCs function, which was involved with activation of CD36-p38 MAPK-TSP-1 pathways and proved by not only the inverse relationship between ox-HDL and circulating EPCs in clinic but also pro-apoptotic effects of HDL separated from patients' serum.

CONCLUSION

Activation of CD36-p38 MAPK-TSP-1 pathways contributes to the pathological effects of ox-HDL on EPCs' dysfunction, which might be one of the potential etiological factors responsible for the disturbed neovascularization in chronic ischemic disease.

microRNA and Wound Healing

microRNAs (miRNAs) are small noncoding RNA molecules which play pivotal roles in wound healing. The increased expression of certain genes and expression of some others represent a key component of the wound biology and are largely under the regulation of naturally occurring miRNAs. Understanding the dysregulated miRNAs in chronic wound biology will therefore enable the development of newer therapies. This chapter focuses on the miRNAs that can be potentially targeted for improving skin wound healing and the challenges in miRNA therapy, including considerations in miRNA target identification and delivery.

Therapeutic Potential of Modulating MicroRNA in Peripheral Artery Disease

Peripheral artery disease (PAD) produces significant disability attributable to lower extremity ischemia. Limited treatment modalities exist to ameliorate clinical symptoms in patients with PAD. Growing evidence links microRNAs to key processes that govern disease expression in PAD including angiogenesis, endothelial function, inflammation, vascular regeneration, vascular smooth muscle cell function, restenosis, and mitochondrial function. MicroRNAs have been identified in circulation and may serve as novel biomarkers in PAD. This article reviews the potential contribution of microRNA to key pathways of disease development in PAD that may lead to microRNA-based diagnostic and therapeutic approaches.

Growing tissues in real and simulated microgravity: new methods for tissue engineering

Tissue engineering in simulated (s-) and real microgravity (r-μg) is currently a topic in Space medicine contributing to biomedical sciences and their applications on Earth. The principal aim of this review is to highlight the advances and accomplishments in the field of tissue engineering that could be achieved by culturing cells in Space or by devices created to simulate microgravity on Earth. Understanding the biology of three-dimensional (3D) multicellular structures is very important for a more complete appreciation of in vivo tissue function and advancing in vitro tissue engineering efforts. Various cells exposed to r-μg in Space or to s-μg created by a random positioning machine, a 2D-clinostat, or a rotating wall vessel bioreactor grew in the form of 3D tissues. Hence, these methods represent a new strategy for tissue engineering of a variety of tissues, such as regenerated cartilage, artificial vessel constructs, and other organ tissues as well as multicellular cancer spheroids. These aggregates are used to study molecular mechanisms involved in angiogenesis, cancer development, and biology and for pharmacological testing of, for example, chemotherapeutic drugs or inhibitors of neoangiogenesis. Moreover, they are useful for studying multicellular responses in toxicology and radiation biology, or for performing coculture experiments. The future will show whether these tissue-engineered constructs can be used for medical transplantations. Unveiling the mechanisms of microgravity-dependent molecular and cellular changes is an up-to-date requirement for improving Space medicine and developing new treatment strategies that can be translated to in vivo models while reducing the use of laboratory animals.

Circulating progenitor cells in hypertensive patients with different degrees of cardiovascular involvement

We investigated whether different degrees of hypertension-related cardiovascular involvement are associated with changes in circulating proangiogenic hematopoietic cell (PHC) numbers and/or phenotypes and/or in the PHC redox system in hypertensive individuals with isolated arterial stiffening (AS) hypertensives or with both carotid intima-media thickening and left ventricular hypertrophy (LVH) hypertensives. We also evaluated microRNA (miRs) 221 and 222 (miRs221/222) expression in CD34+ cells, the relationship between these miRs and cell number and reactive oxygen species (ROS) levels, and the expression of manganese superoxide dismutase (MnSOD), catalase (CAT) glutathione peroxidase type-1 (GPx-1) and gp91phox-containing nicotinamide-adenine-dinucleotide-phosphate-oxidase (NOX2). Proangiogenic hematopoietic cells (PHCs) from hypertensive patients and controls were isolated by flow cytometry. PHCs were higher in hypertensives than in controls but were lower in LVH than in AS hypertensives. In CD34+ cells from AS hypertensives, NOX2, MnSOD, CAT and GPx-1 were overexpressed; ROS, miRs and NOX2 were also increased and were associated with cell number. In LVH, we found an imbalance in the cell redox system; MnSOD showed the highest values, whereas CAT and GPx-1 were lower than in AS hypertensives. Intracellular ROS, miRs and NOX2 were higher and inversely associated with cell number. In AS hypertensives, the redox balance may sustain the increase in PHCs; by contrast, in hypertensives with more advanced lesions, redox imbalance may result in increased oxidative stress and cell reduction.

Dicer knockdown inhibits endothelial cell tumor growth via microRNA 21a-3p targeting of Nox-4

MicroRNAs (miR) are emerging as biomarkers and potential therapeutic targets in tumor management. Endothelial cell tumors are the most common soft tissue tumors in infants, yet little is known about the significance of miR in regulating their growth. A validated mouse endothelial cell (EOMA) tumor model was used to demonstrate that post-transcriptional gene silencing of dicer, the enzyme that converts pre-miR to mature miR, can prevent tumor formation in vivo. Tumors were formed in eight of eight mice injected with EOMA cells transfected with control shRNA but formed in only four of ten mice injected with EOMA cells transfected with dicer shRNA. Tumors that formed in the dicer shRNA group were significantly smaller than tumors in the control group. This response to dicer knockdown was mediated by up-regulated miR 21a-3p activity targeting the nox-4 3'-UTR. EOMA cells were transfected with miR 21a-3p mimic and luciferase reporter plasmids containing either intact nox-4 3'-UTR or with mutation of the proposed 3'-UTR miR21a-3p binding sites. Mean luciferase activity was decreased by 85% in the intact compared with the site mutated vectors (p < 0.01). Attenuated Nox-4 activity resulted in decreased cellular hydrogen peroxide production and decreased production of oxidant-inducible monocyte chemoattractant protein-1, which we have previously shown to be critically required for endothelial cell tumor formation. These findings provide the first evidence establishing the significance of dicer and microRNA in promoting endothelial cell tumor growth in vivo.

MicroRNA regulation of endothelial homeostasis and commitment-implications for vascular regeneration strategies using stem cell therapies

Human embryonic (hESC) and induced pluripotent (hiPSC) stem cells have broad therapeutic potential in the treatment of a range of diseases, including those of the vascular system. Both hESCs and hiPSCs have the capacity for indefinite self-renewal, in addition to their ability to differentiate into any adult cell type. These cells could provide a potentially unlimited source of cells for transplantation and, therefore, provide novel treatments, e.g. in the production of endothelial cells for vascular regeneration. MicroRNAs are short, noncoding RNAs that act posttranscriptionally to control gene expression and thereby exert influence over a wide range of cellular processes, including maintenance of pluripotency and differentiation. Expression patterns of these small RNAs are tissue specific, and changes in microRNA levels have often been associated with disease states in humans, including vascular pathologies. Here, we review the roles of microRNAs in endothelial cell function and vascular disease, as well as their role in the differentiation of pluripotent stem cells to the vascular endothelial lineage. Furthermore, we discuss the therapeutic potential of stem cells and how knowledge and manipulation of microRNAs in stem cells may enhance their capacity for vascular regeneration.

Regulation of the Nrf2 antioxidant pathway by microRNAs: New players in micromanaging redox homeostasis

MicroRNAs are now thought to play a central role in the regulation of many diverse aspects of cell biology; however, it remains to be fully elucidated how microRNAs can orchestrate cellular redox homeostasis, which plays a central role in a multitude of physiological and pathophysiological processes. The redox-sensitive transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) serves as a "master regulator" of cell survival through the coordinated induction of phase II and antioxidant defense enzymes to counteract oxidative stress and modulate redox signaling events. MicroRNAs are able to "fine-tune" the regulation of processes including those directly interacting with the Nrf2 pathway and the generation of reactive oxygen species (ROS). This review highlights that cellular redox homeostasis can be regulated by microRNAs through their modulation of Nrf2-driven antioxidant gene expression as well as key enzymes that generate ROS, which in turn can alter the biogenesis and processing of microRNAs. Therefore redox sensitive microRNAs or "redoximiRs" add an important regulatory mechanism for redox signaling beyond the well-characterized actions of Nrf2. The potential exists for microRNA-based therapies where diminished antioxidant defenses and dysregulated redox signaling can lead to cardiovascular diseases, cancers, neurodegeneration, and accelerated aging.