From cellular senescence to age-associated diseases: the miRNA connection

The Interplay Between Obesity and Aging in Breast Cancer and Regulatory Function of MicroRNAs in This Pathway

Breast cancer (BC) is a significant contributor to cancer-related deaths in women, and it has complex connections with obesity and aging. This review explores the interaction between obesity and aging in relation to the development and progression of BC, focusing on the controlling role of microRNAs (miRNAs). Obesity, characterized by excess adipose tissue, contributes to a proinflammatory environment and metabolic dysregulation, which are important in tumor development. Aging, associated with cellular senescence and systemic changes, further exacerbates these conditions. miRNAs, small noncoding RNAs that regulate gene expression, play key roles in these processes, impacting pathways involved in cell proliferation, apoptosis, and cancer metastasis, either as tumor suppressors or oncogenes. Importantly, specific miRNAs are implicated in mediating the impact of obesity and aging on BC. Exploring the regulatory networks controlled by miRNAs provides valuable information on new targets for therapy and predictive markers, demonstrating the potential for using miRNA-based interventions to treat BC in obese and elderly individuals. This review emphasizes the importance of integrated research strategies to understand the complex connections between obesity, aging, and miRNA regulation in BC.

The Intersection of Epigenetics and Senolytics in Mechanisms of Aging and Therapeutic Approaches

The biological process of aging is influenced by a complex interplay of genetic, environmental, and epigenetic factors. Recent advancements in the fields of epigenetics and senolytics offer promising avenues for understanding and addressing age-related diseases. Epigenetics refers to heritable changes in gene expression without altering the DNA sequence, with mechanisms like DNA methylation, histone modification, and non-coding RNA regulation playing critical roles in aging. Senolytics, a class of drugs targeting and eliminating senescent cells, address the accumulation of dysfunctional cells that contribute to tissue degradation and chronic inflammation through the senescence-associated secretory phenotype. This scoping review examines the intersection of epigenetic mechanisms and senolytic therapies in aging, focusing on their combined potential for therapeutic interventions. Senescent cells display distinct epigenetic signatures, such as DNA hypermethylation and histone modifications, which can be targeted to enhance senolytic efficacy. Epigenetic reprogramming strategies, such as induced pluripotent stem cells, may further complement senolytics by rejuvenating aged cells. Integrating epigenetic modulation with senolytic therapy offers a dual approach to improving healthspan and mitigating age-related pathologies. This narrative review underscores the need for continued research into the molecular mechanisms underlying these interactions and suggests future directions for therapeutic development, including clinical trials, biomarker discovery, and combination therapies that synergistically target aging processes.

Profiling microRNA expression during senescence and aging: mining for a diagnostic tool of senescent-cell burden

In the last decade cellular senescence, a hallmark of aging, has come into focus for pharmacologically targeting aging processes. Senolytics are one of these interventive strategies that have advanced into clinical trials, creating an unmet need for minimally invasive biomarkers of senescent cell load to identify patients at need for senotherapy. We created a landscape of miRNA and mRNA expression in five human cell types induced to senescence in-vitro and provide proof-of-principle evidence that miRNA expression can track senescence burden dynamically in-vivo using transgenic p21 high senescent cell clearance in HFD fed mice. Finally, we profiled miRNA expression in seven different tissues, total plasma, and plasma derived EVs of young and 25 months old mice. In a systematic analysis, we identified 22 candidate senomiRs with potential to serve as circulating biomarkers of senescence not only in rodents, but also in upcoming human clinical senolytic trials.

Calcium transferring from ER to mitochondria via miR-129/ITPR2 axis controls cellular senescence in vitro and in vivo

Senescent cells are known to be accumulated in aged organisms. Although the two main characteristics, cell cycle arrest (for dividing cells) and secretion of senescence-associated secretory phenotype (SASP) factors, have been well described, the lack of sufficient senescent markers and incomplete understanding of mechanisms have limited the progress of the anti-senescence field. Calcium transferred from the endoplasmic reticulum (ER) via inositol 1, 4, 5-trisphosphate receptor type 2 (ITPR2) to mitochondria has emerged as a key player during cellular senescence and aging. However, the internal regulatory mechanisms, particularly those of endogenous molecules, remain only partially understood. Here we identified miRNA-129 (miR-129) as a direct repressor of ITPR2. Interestingly, miR-129 controlled a cascade of intracellular calcium signaling, mitochondrial membrane potential (MMP), reactive oxygen species (ROS), DNA damage, and consequently cellular senescence through ITPR2 and mitochondrial calcium uniporter (MCU). In addition, miR-129 was repressed in different senescence models and delayed bleomycin-induced cellular senescence. Importantly, intraperitoneal injection of miR-129 partly postponed bleomycin-accelerated lung aging and natural aging markers as well as reduced immunosenescence markers in mice. Altogether, these findings demonstrated that miR-129 regulated cellular senescence and aging markers via intracellular calcium signaling by directly targeting ITPR2.

Genomic Instability and Epigenetic Changes during Aging

Aging is considered the deterioration of physiological functions along with an increased mortality rate. This scientific review focuses on the central importance of genomic instability during the aging process, encompassing a range of cellular and molecular changes that occur with advancing age. In particular, this revision addresses the genetic and epigenetic alterations that contribute to genomic instability, such as telomere shortening, DNA damage accumulation, and decreased DNA repair capacity. Furthermore, the review explores the epigenetic changes that occur with aging, including modifications to histones, DNA methylation patterns, and the role of non-coding RNAs. Finally, the review discusses the organization of chromatin and its contribution to genomic instability, including heterochromatin loss, chromatin remodeling, and changes in nucleosome and histone abundance. In conclusion, this review highlights the fundamental role that genomic instability plays in the aging process and underscores the need for continued research into these complex biological mechanisms.

AIMP3 induces laminopathy and senescence of vascular smooth muscle cells by reducing lamin A expression and leads to vascular aging in vivo

Aminoacyl-tRNA synthetase-interacting multifunctional protein 3 (AIMP3), a tumor suppressor, mediates a progeroid phenotype in mice by downregulating lamin A. We investigated whether AIMP3 induces laminopathy and senescence of human aortic smooth muscle cells (HASMCs) and is associated with vascular aging in mice and humans in line with decreased lamin A expression. Cellular senescence was evaluated after transfecting HASMCs with AIMP3. Molecular analyses of genes encoding AIMP3, lamin A, chemokine (C-C motif) ligand 2 (CCL2), and C-C chemokine receptor type 2 (CCR2) and histological comparisons of aortas were performed with mice at various ages (7 weeks, 5 months, 12 months, 24 months, and 32 months), AIMP3-transgenic mice, and human femoral arteries of cadavers. AIMP3-transfected HASMCs exhibited increased AIMP3 and senescence marker p16 protein expression and decreased lamin A protein expression in accordance with their disrupted nuclear morphology in histological analyses. AIMP3-transgenic mice displayed increased AIMP3 protein expression and decreased lamin A protein expression in aortas together with typical aging pathologies. Similar changes were observed in wild-type aging (24-month-old) mice but not in wild-type young (7-week-old) mice. In humans, AIMP3 and lamin A protein expression was higher and lower, respectively, in femoral arteries of elderly individuals than in those of their younger counterparts. This study found that AIMP3 overexpression in vitro decreased lamin A expression and induced nuclear laminopathy and cellular senescence. Similar findings were made in the vasculature of aging mice and elderly humans.

Mango (Mangifera indica L.) Leaves: Nutritional Composition, Phytochemical Profile, and Health-Promoting Bioactivities

Mangifera indica L. belongs to the family of Anacardiaceae and is an important fruit from South and Southeast Asia. India, China, Thailand, Indonesia, Pakistan, Mexico, Brazil, Bangladesh, Nigeria, and the Philippines are among the top mango producer countries. Leaves of the mango plant have been studied for their health benefits, which are attributed to a plethora of phytochemicals such as mangiferin, followed by phenolic acids, benzophenones, and other antioxidants such as flavonoids, ascorbic acid, carotenoids, and tocopherols. The extracts from mango leaves (MLs) have been studied for their biological activities, including anti-cancer, anti-diabetic, anti-oxidant, anti-microbial, anti-obesity, lipid-lowering, hepato-protection, and anti-diarrheal. In the present review, we have elaborated on the nutritional and phytochemical profile of the MLs. Further, various bioactivities of the ML extracts are also critically discussed. Considering the phytochemical profile and beneficial effects of the MLs, they can be used as a potential ingredient for the development of functional foods and pharmaceutical drugs. However, more detailed clinical trials still needed to be conducted for establishing the actual efficacy of the ML extracts.

Association study of leukocyte telomere length and genetic polymorphism within hTERT promoter with type 2 diabetes in Bangladeshi population

Telomeres are protective cap on the ends of DNA of non-coding tandem repeats of TTAGGG. Human telomerase reverse transcriptase (hTERT) is a catalytic subunit of telomerase that maintains the structure of telomeres. Type 2 diabetes (T2D) affects multi-organ and telomere length by altering telomerase activity. We aimed to evaluate the relative telomere length (RTL) and risk association of rs2853669 with T2D in Bangladeshi population. RTL was measured in 408 unrelated Bangladeshi (224 T2D and 184 healthy) using primers for target gene and reference gene albumin. Genotypic frequencies for rs2853669 were determined using TaqMan® probes. The mean level of age adjusted RTL (AARTL) varied significantly between the healthy and individuals with T2D for all the genotypes with respect to rs2853669. Moreover, healthy individuals had significantly higher AARTL than T2D. Similar findings were observed when study participants were stratified based on their gender. Association studies revealed that under codominant model of inheritance, TC genotype showed protective role against development of type 2 diabetes. This study suggests a possible role of telomere biology in T2DM, but their association needs to be evaluated further with a larger series and matched healthy controls.

Systems biology and network pharmacology of frailty reveal novel epigenetic targets and mechanisms

Frailty is an age-associated condition, characterized by an inappropriate response to stress that results in a higher frequency of adverse outcomes (e.g., mortality, institutionalization and disability). Some light has been shed over its genetic background, but this is still a matter of debate. In the present study, we used network biology to analyze the interactome of frailty-related genes at different levels to relate them with pathways, clinical deficits and drugs with potential therapeutic implications. Significant pathways involved in frailty: apoptosis, proteolysis, muscle proliferation, and inflammation; genes as FN1, APP, CREBBP, EGFR playing a role as hubs and bottlenecks in the interactome network and epigenetic factors as HIST1H3 cluster and miR200 family were also involved. When connecting clinical deficits and genes, we identified five clusters that give insights into the biology of frailty: cancer, glucocorticoid receptor, TNF-α, myostatin, angiotensin converter enzyme, ApoE, interleukine-12 and −18. Finally, when performing network pharmacology analysis of the target nodes, some compounds were identified as potentially therapeutic (e.g., epigallocatechin gallate and antirheumatic agents); while some other substances appeared to be toxicants that may be involved in the development of this condition.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

Short-term sustained hyperglycaemia fosters an archetypal senescence-associated secretory phenotype in endothelial cells and macrophages

Diabetic status is characterized by chronic low-grade inflammation and an increased burden of senescent cells. Recently, the senescence-associated secretory phenotype (SASP) has been suggested as a possible source of inflammatory factors in obesity-induced type 2 diabetes. However, while senescence is a known consequence of hyperglycaemia, evidences of SASP as a result of the glycaemic insult are missing. In addition, few data are available regarding which cell types are the main SASP-spreading cells in vivo. Adopting a four-pronged approach we demonstrated that: i) an archetypal SASP response that was at least partly attributable to endothelial cells and macrophages is induced in mouse kidney after in vivo exposure to sustained hyperglycaemia; ii) reproducing a similar condition in vitro in endothelial cells and macrophages, hyperglycaemic stimulus largely phenocopies the SASP acquired during replicative senescence; iii) in endothelial cells, hyperglycaemia-induced senescence and SASP could be prevented by SOD-1 overexpression; and iiii) ex vivo circulating angiogenic cells derived from peripheral blood mononuclear cells from diabetic patients displayed features consistent with the SASP. Overall, the present findings document a direct link between hyperglycaemia and the SASP in endothelial cells and macrophages, making the SASP a highly likely contributor to the fuelling of low-grade inflammation in diabetes.

Cost-utility analysis of fracture risk assessment using microRNAs compared with standard tools and no monitoring in the Austrian female population

BACKGROUND

Osteoporosis poses an immense burden to the society in terms of morbidity, mortality and financial cost. To reduce this burden, it is essential to accurately assess the individual patient's fracture risk and, where indicated, to initiate appropriate treatment that reduces fracture probability. Current screening and monitoring approaches include utilization of FRAX®, a web-based country-specific fracture risk assessment tool, and bone mineral density measurement by Dual Energy X-ray Absorptiometry (DXA). Recently, microRNAs have been recognized as important regulators of bone physiology and potential biomarkers for fracture risk assessment and monitoring. A fracture risk assessment tool based on microRNAs (osteomiR™ test) is currently being developed. The aim of this study was to estimate the cost-effectiveness of fracture risk screening, monitoring, and resulting treatment decisions for the Austrian female population using the osteomiR™ test compared with DXA, with FRAX®, or with no screening/monitoring.

METHODS

A cost-utility-model was developed to simulate long-term consequences of Austrian women from age 50 over lifetime or death with respect to osteoporosis. Markov-modelling techniques were used to calculate health state transitions of fracture incidence according to risk groups (high, intermediate, low). High-risk patients receive medical treatment. Probabilities were derived via systematic-literature-review; direct costs (2015, €) from published sources from the payer's perspective. Results evaluate the incremental cost-effectiveness ratios (ICER) for osteomiR™ against the comparators, gains or losses of fractures, life years (LYs), quality-adjusted life years (QALYs), and direct costs. QALYs, life years (LYs) and costs were discounted (3% p.a).

RESULTS

Fracture risk assessment and monitoring using the osteomiR™ test reduces fracture incidence compared with no monitoring, DXA alone, or FRAX® alone. In the per-patient analysis, the ICER/QALY of osteomiR™ vs. no-monitoring was 13,103 €, vs. FRAX® 37,813 €, and vs. DXA -19,605 €, indicating that costs can be saved while gaining QALYs. Considering the total cohort over lifetime, the osteomiR™ test can avoid 57,919 fractures compared with DXA, 31,285 fractures compared with FRAX® and 133,394 fractures compared with no monitoring. Sensitivity analysis confirmed the robustness of these findings.

CONCLUSION

Fracture risk assessment and monitoring using the osteomiR™ test dominates DXA-strategy and constitutes a cost-effective alternative to FRAX®, and no-monitoring, respectively.

miR-34c-5p promotes eradication of acute myeloid leukemia stem cells by inducing senescence through selective RAB27B targeting to inhibit exosome shedding

Leukemia stem cells (LSCs) are responsible for acute myeloid leukemia (AML) chemotherapy resistance and relapse. Here, we discovered that miR-34c-5p, a microRNA central to the senescence regulation network, was significantly down-regulated in AML (non-acute promyelocytic leukemia, non-APL) stem cells compared to that in normal hematopoietic stem cells (HSCs). The lower expression of miR-34c-5p in LSCs was closely correlated to the adverse prognosis and poor responses to therapy of AML patients. Increased miR-34c-5p expression induced LSCs senescence ex vivo, prevented leukemia development and promoted the eradication of LSCs in immune deficient mice. Mechanistically, forced expression of miR-34-5p induced senescence in LSCs through p53-p21^Cip1-Cyclin-dependent kinase (CDK)/Cyclin or p53-independent CDK/Cyclin pathways. Exosome-mediated transfer of miR-34c-5p was one of the reasons for miR-34c-5p deficiency in LSCs. Furthermore, miR-34c-5p could increase its intracellular level by inhibiting exosome-mediated transfer via a positive feedback loop through RAB27B, a molecule that promotes exosome shedding. Overall, this study establishes a new strategy for treatment of AML patients by targeting LSCs to reinitiate senescence via increased miR-34c-5p expression. This miRNA-mediated tumor stem cell senescence could also have important therapeutic value in other malignancies.

The Immortal Senescence

Activation of oncogenic signaling paradoxically results in the permanent withdrawal from cell cycle and induction of senescence (oncogene-induced senescence (OIS)). OIS is a fail-safe mechanism used by the cells to prevent uncontrolled tumor growth, and, as such, it is considered as the first barrier against cancer. In order to progress, tumor cells thus need to first overcome the senescent phenotype. Despite the increasing attention gained by OIS in the past 20 years, this field is still rather young due to continuous emergence of novel pathways and processes involved in OIS. Among the many factors contributing to incomplete understanding of OIS are the lack of unequivocal markers for senescence and the complexity of the phenotypes revealed by senescent cells in vivo and in vitro. OIS has been shown to play major roles at both the cellular and organismal levels in biological processes ranging from embryonic development to barrier to cancer progression. Here we will briefly outline major advances in methodologies that are being utilized for induction, identification, and characterization of molecular processes in cells undergoing oncogene-induced senescence. The full description of such methodologies is provided in the corresponding chapters of the book.

Noncoding RNAs in Cardiovascular Aging

With a progressively growing elderly population, aging-associated cardiovascular diseases and other pathologies have brought great burden to the economy, society, and individuals. Therefore, identifying therapeutic targets and developing effective strategies to prevent from cardiovascular aging are highly needed. Accumulating evidences suggest that noncoding RNAs (ncRNAs) such as microRNAs and long noncoding RNAs (lncRNAs) play important roles in regulating gene expression, which contributes to many pathophysiological processes of cellular senescence, aging, and aging-related diseases in cardiovascular systems. Here we provided a general overview of ncRNAs as well as the underlying mechanisms involved in cardiovascular aging. Although the importance of ncRNAs in cardiovascular aging has been reported and commonly acknowledged, further studies are still necessary to elucidate the underlying molecular mechanisms.

MicroRNA-212 negatively regulates starvation induced autophagy in prostate cancer cells by inhibiting SIRT1 and is a modulator of angiogenesis and cellular senescence

Among a number of non-coding RNAs, role of microRNAs (miRNAs) in cancer cell proliferation, cancer initiation, development and metastasis have been extensively studied and miRNA based therapeutic approaches are being pursued. Prostate cancer (PCa) is a major health concern and several deregulated miRNAs have been described in PCa. miR-212 is differentially modulated in multiple cancers however its function remains elusive. In this study, we found that miR-212 is downregulated in PCa tissues when compared with benign adjacent regions (n = 40). Also, we observed reduced levels of circulatory miR-212 in serum from PCa patients (n = 40) when compared with healthy controls (n = 32). Elucidating the functional role of miR-212, we demonstrate that miR-212 negatively modulates starvation induced autophagy in PCa cells by targeting sirtuin 1 (SIRT1). Overexpression of miR-212 also leads to inhibition of angiogenesis and cellular senescence. In conclusion, our study indicates a functional role of miR-212 in PCa and suggests the development of miR-212 based therapies.

Unexploited Antineoplastic Effects of Commercially Available Anti-Diabetic Drugs

The development of efficacious antitumor compounds with minimal toxicity is a hot research topic. Numerous cancer cell targeted agents are evaluated daily in laboratories for their antitumorigenicity at the pre-clinical level, but the process of their introduction into the market is costly and time-consuming. More importantly, even if these new antitumor agents manage to gain approval, clinicians have no former experience with them. Accruing evidence supports the idea that several medications already used to treat pathologies other than cancer display pleiotropic effects, exhibiting multi-level anti-cancer activity and chemosensitizing properties. This review aims to present the anticancer properties of marketed drugs (i.e., metformin and pioglitazone) used for the management of diabetes mellitus (DM) type II. Mode of action, pre-clinical in vitro and in vivo or clinical data as well as clinical applicability are discussed here. Given the precious multi-year clinical experience with these non-antineoplastic drugs their repurposing in oncology is a challenging alternative that would aid towards the development of therapeutic schemes with less toxicity than those of conventional chemotherapeutic agents. More importantly, harnessing the antitumor function of these agents would save precious time from bench to bedside to aid the fight in the arena of cancer.

MicroRNAs; easy and potent targets in optimizing therapeutic methods in reparative angiogenesis

The age‐related senescence of adult tissues is associated with the decreased level of angiogenic capability and with the development of a degenerative disease such as atherosclerosis which thereafter result in the deteriorating function of multiple systems. Findings indicate that tissue senescence not only diminishes repair processes but also promotes atherogenesis, serving as a double‐edged sword in the development and prognosis of ischaemia‐associated diseases. Evidence evokes microRNAs (miRNAs) as molecular switchers that underlie cellular events in different tissues. Here, miRNAs would promote new potential targets for optimizing therapeutic methods in blood flow recovery to the ischaemic area. Effectively beginning an ischaemia therapy, a more characteristic of miRNA changes in adult tissues is prerequisite and in the forefront. It may also be a preliminary phase in treatment strategies by stem cell‐based therapy.

MicroRNAs in skin tissue engineering

35.2 million annual cases in the U.S. require clinical intervention for major skin loss. To meet this demand, the field of skin tissue engineering has grown rapidly over the past 40 years. Traditionally, skin tissue engineering relies on the "cell-scaffold-signal" approach, whereby isolated cells are formulated into a three-dimensional substrate matrix, or scaffold, and exposed to the proper molecular, physical, and/or electrical signals to encourage growth and differentiation. However, clinically available bioengineered skin equivalents (BSEs) suffer from a number of drawbacks, including time required to generate autologous BSEs, poor allogeneic BSE survival, and physical limitations such as mass transfer issues. Additionally, different types of skin wounds require different BSE designs. MicroRNA has recently emerged as a new and exciting field of RNA interference that can overcome the barriers of BSE design. MicroRNA can regulate cellular behavior, change the bioactive milieu of the skin, and be delivered to skin tissue in a number of ways. While it is still in its infancy, the use of microRNAs in skin tissue engineering offers the opportunity to both enhance and expand a field for which there is still a vast unmet clinical need. Here we give a review of skin tissue engineering, focusing on the important cellular processes, bioactive mediators, and scaffolds. We further discuss potential microRNA targets for each individual component, and we conclude with possible future applications.

miRNA control of tissue repair and regeneration

Tissue repair and regeneration rely on the function of miRNA, molecular silencers that enact post-transcriptional gene silencing of coding genes. Disruption of miRNA homeostasis is developmentally lethal, indicating that fetal tissue development is tightly controlled by miRNAs. Multiple critical facets of adult tissue repair are subject to control by miRNAs, as well. Sources of cell pool for tissue repair and regeneration are diverse and provided by processes including cellular dedifferentiation, transdifferentiation, and reprogramming. Each of these processes is regulated by miRNAs. Furthermore, induced pluripotency may be achieved by miRNA-based strategies independent of transcription factor manipulation. The observation that miRNA does not integrate into the genome makes miRNA-based therapeutic strategies translationally valuable. Tools to manipulate cellular and tissue miRNA levels include mimics and inhibitors that may be specifically targeted to cells of interest at the injury site. Here, we discuss the extraordinary importance of miRNAs in tissue repair and regeneration based on emergent reports and rapid advances in miRNA-based therapeutics.

The master switchers in the aging of cardiovascular system, reverse senescence by microRNA signatures; as highly conserved molecules

The incidence of CVD increases with aging, because of long-term exposure to risk factors/stressors. Aging is a complex biological process resulting in progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death. The main hallmarks of aging are cellular senescence, stem cell exhaustion, and altered intracellular communication. The major hallmarks of senescence are mitochondrial dysfunction, genomic instability, telomere attrition and epigenetic alterations, all of which contributing to cellular aging. Such events are controls by a family of small, non-coding RNAs (miRNAs) that interact with component of cellular senescence pathway; mitochondrial biogenesis/removal, DNA damage response machinery and IGF-1 signaling pathway. Here, we review recent in vivo/in vitro reports that miRNAs are key modulators of heart senescence, and act as master switchers to influence reprogramming pathway. We discuss evidence that abrupt deregulation of some mit-miRNAs governing senescence programs underlies age-associated CVD. In particular, due to the highly conserved nature and well-recognized target sites, miRNAs have been defined as master switchers in controlling heart progenitor cell biology. Modulation of mit-miRNA expression holds the great promise in switching off/on cellular senescence/reprogramming to rejuvenate stem cells to aid regenerative process.

Integromics network meta-analysis on cardiac aging offers robust multi-layer modular signatures and reveals micronome synergism

Background

The avalanche of integromics and panomics approaches shifted the deciphering of aging mechanisms from single molecular entities to communities of them. In this orientation, we explore the cardiac aging mechanisms – risk factor for multiple cardiovascular diseases - by capturing the micronome synergism and detecting longevity signatures in the form of communities (modules).

For this, we developed a meta-analysis scheme that integrates transcriptome expression data from multiple cardiac-specific independent studies in mouse and human along with proteome and micronome interaction data in the form of multiple independent weighted networks. Modularization of each weighted network produced modules, which in turn were further analyzed so as to define consensus modules across datasets that change substantially during lifespan. Also, we established a metric that determines - from the modular perspective - the synergism of microRNA-microRNA interactions as defined by significantly functionally associated targets.

Results

The meta-analysis provided 40 consensus integromics modules across mouse datasets and revealed microRNA relations with substantial collective action during aging. Three modules were reproducible, based on homology, when mapped against human-derived modules. The respective homologs mainly represent NADH dehydrogenases, ATP synthases, cytochrome oxidases, Ras GTPases and ribosomal proteins. Among various observations, we corroborate to the involvement of miR-34a (included in consensus modules) as proposed recently; yet we report that has no synergistic effect. Moving forward, we determined its age-related neighborhood in which HCN3, a known heart pacemaker channel, was included. Also, miR-125a-5p/-351, miR-200c/-429, miR-106b/-17, miR-363/-92b, miR-181b/-181d, miR-19a/-19b, let-7d/-7f, miR-18a/-18b, miR-128/-27b and miR-106a/-291a-3p pairs exhibited significant synergy and their association to aging and/or cardiovascular diseases is supported in many cases by a disease database and previous studies. On the contrary, we suggest that miR-22 has not substantial impact on heart longevity as proposed recently.

Conclusions

We revised several proteins and microRNAs recently implicated in cardiac aging and proposed for the first time modules as signatures. The integromics meta-analysis approach can serve as an efficient subvening signature tool for more-oriented better-designed experiments. It can also promote the combinational multi-target microRNA therapy of age-related cardiovascular diseases along the continuum from prevention to detection, diagnosis, treatment and outcome.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1256-3) contains supplementary material, which is available to authorized users.

The role of microRNAs in cellular senescence and age-related conditions of cartilage and bone

BACKGROUND AND PURPOSE

We reviewed the current state of research on microRNAs in age-related diseases in cartilage and bone.

METHODS

PubMed searches were conducted using separate terms to retrieve articles on (1) the role of microRNAs on aging and tissue degeneration, (2) specific microRNAs that influence cellular and organism senescence, (3) microRNAs in age-related musculoskeletal conditions, and (4) the diagnostic and therapeutic potential of microRNAs in age-related musculoskeletal conditions.

RESULTS

An increasing number of studies have identified microRNAs associated with cellular aging and tissue degeneration. Specifically in regard to frailty, microRNAs have been found to influence the onset and course of age-related musculoskeletal conditions such as osteoporosis, osteoarthritis, and posttraumatic arthritis. Both intracellular and extracellular microRNAs may be suitable to function as diagnostic biomarkers.

INTERPRETATION

The research data currently available suggest that microRNAs play an important role in orchestrating age-related processes and conditions of the musculoskeletal system. Further research may help to improve our understanding of the complexity of these processes at the cellular and extracellular level. The option to develop microRNA biomarkers and novel therapeutic agents for the degenerating diseases of bone and cartilage appears to be promising.

Age and sex differences in kidney microRNA expression during the life span of F344 rats

Background

Growing evidence suggests that epigenetic mechanisms of gene regulation may play a role in susceptibilities to specific toxicities and adverse drug reactions. MiRNAs in particular have been shown to be important regulators in cancer and other diseases and show promise as predictive biomarkers for diagnosis and prognosis. In this study, we characterized the global kidney miRNA expression profile in untreated male and female F344 rats throughout the life span. These findings were correlated with sex-specific susceptibilities to adverse renal events, such as male-biased renal fibrosis and inflammation in old age.

Methods

Kidney miRNA expression was examined in F344 rats at 2, 5, 6, 8, 15, 21, 78, and 104 weeks of age in both sexes using Agilent miRNA microarrays. Differential expression was determined using filtering criteria of ≥1.5 fold change and ANOVA or pairwise t-test (FDR <5%) to determine significant age and sex effects, respectively. Pathway analysis software was used to investigate the possible roles of these target genes in age- and sex-specific differences.

Results

Three hundred eleven miRNAs were found to be expressed in at least one age and sex. Filtering criteria revealed 174 differentially expressed miRNAs in the kidney; 173 and 34 miRNAs exhibiting age and sex effects, respectively. Principal component analysis revealed age effects predominated over sex effects, with 2-week miRNA expression being much different from other ages. No significant sexually dimorphic miRNA expression was observed from 5 to 8 weeks, while the most differential expression (13 miRNAs) was observed at 21 weeks. Potential target genes of these differentially expressed miRNAs were identified.

Conclusions

The expression of 56% of detected renal miRNAs was found to vary significantly with age and/or sex during the life span of F344 rats. Pathway analysis suggested that 2-week-expressed miRNAs may be related to organ and cellular development and proliferation pathways. Male-biased miRNA expression at older ages correlated with male-biased renal fibrosis and mononuclear cell infiltration. These miRNAs showed high representation in renal inflammation and nephritis pathways, and included miR-214, miR-130b, miR-150, miR-223, miR-142-5p, miR-185, and miR-296*. Analysis of kidney miRNA expression throughout the rat life span will improve the use of current and future renal biomarkers and inform our assessments of kidney injury and disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-014-0019-1) contains supplementary material, which is available to authorized users.

Structure of precursor microRNA's terminal loop regulates human Dicer's dicing activity by switching DExH/D domain

Almost all pre-miRNAs in eukaryotic cytoplasm are recognized and processed into double-stranded microRNAs by the endonuclease Dicer protein comprising of multiple domains. As a key player in the small RNA induced gene silencing pathway, the major domains of Dicer are conserved among different species with the exception of the N-terminal components. Human Dicer’s N-terminal domain has been shown to play an auto-inhibitory function of the protein’s dicing activity. Such an auto-inhibition can be released when the human Dicer protein dimerizes with its partner protein, such as TRBP, PACT through the N-terminal DExH/D (ATPase-helicase) domain. The typical feature of a pre-miRNA contains a terminal loop and a stem duplex, which bind to human Dicer’s DExH/D (ATPase-helicase) domain and PAZ domain respectively during the dicing reaction. Here, we show that pre-miRNA’s terminal loop can regulate human Dicer’s enzymatic activity by interacting with the DExH/D (ATPase-helicase) domain. We found that various editing products of pre-miR-151 by the ADAR1P110 protein, an A-to-I editing enzyme that modifies pre-miRNAs sequence, have different terminal loop structures and different activity regulatory effects on human Dicer. Single particle electron microscopy reconstruction revealed that pre-miRNAs with different terminal loop structures induce human Dicer’s DExH/D (ATPase-helicase) domain into different conformational states, in correlation with their activity regulatory effects.

Secretion of microvesicular miRNAs in cellular and organismal aging

Changes of factors circulating in the systemic environment during human aging have been investigated for a long time. Only recently however, miRNAs have been found to be secreted into the systemic and tissue environments where they are protected from RNAses by either carrier proteins or by being packaged into microvesicles. These miRNAs are then taken up by recipient cells, changing the cellular behavior by the classical miRNA induced silencing of target mRNAs. The origin of circulating miRNAs, however, is in most instances unclear, but senescent cells emerge as a possible source of such secreted miRNAs. Since differences in the circulating miRNAs have been found in a variety of age-associated diseases, and accumulation of senescent cells in the elderly emerges as a possible detrimental factor in aging, it is well conceivable that these miRNAs might contribute to the functional decline observed during aging of organisms. Therefore, we here give an overview on current knowledge on microvesicular secretion of miRNAs, changes of the systemic and tissue environments during aging of cells and organisms. Finally, we summarize current knowledge on miRNAs that are found to be specific for age-associated diseases.

High levels of oncomiR-21 contribute to the senescence-induced growth arrest in normal human cells and its knock-down increases the replicative lifespan

Cellular senescence of normal human cells has by now far exceeded its initial role as a model system for aging research. Many reports show the accumulation of senescent cells in vivo, their effect on their microenvironment and its double-edged role as tumour suppressor and promoter. Importantly, removal of senescent cells delays the onset of age-associated diseases in mouse model systems. To characterize the role of miRNAs in cellular senescence of endothelial cells, we performed miRNA arrays from HUVECs of five different donors. Twelve miRNAs, comprising hsa-miR-23a, hsa-miR-23b, hsa-miR-24, hsa-miR-27a, hsa-miR-29a, hsa-miR-31, hsa-miR-100, hsa-miR-193a, hsa-miR-221, hsa-miR-222 and hsa-let-7i are consistently up-regulated in replicatively senescent cells. Surprisingly, also miR-21 was found up-regulated by replicative and stress-induced senescence, despite being described as oncogenic. Transfection of early passage endothelial cells with miR-21 resulted in lower angiogenesis, and less cell proliferation mirrored by up-regulation of p21^CIP1 and down-regulation of CDK2. These two cell-cycle regulators are indirectly regulated by miR-21 via its validated direct targets NFIB (Nuclear factor 1 B-type), a transcriptional inhibitor of p21^CIP1, and CDC25A, which regulates CDK2 activity by dephosphorylation. Knock-down of either NFIB or CDC25A shows a phenocopy of over-expressing miR-21 in regard to cell-cycle arrest. Finally, miR-21 over-epxression reduces the replicative lifespan, while stable knock-down by sponges extends the replicative lifespan of endothelial cells. Therefore, we propose that miR-21 is the first miRNA that upon its knock-down extends the replicative lifespan of normal human cells.