Ingo Volkmann

Regulation and function of miRNA-21 in health and disease

The small regulatory RNA microRNA-21 (miR-21) plays a crucial role in a plethora of biological functions and diseases including development, cancer, cardiovascular diseases and inflammation. The gene coding for pri-miR-21 (primary transcript containing miR-21) is located within the intronic region of the TMEM49 gene. Despite pri-miR-21 and TMEM49 are overlapping genes in the same direction of transcription, pri-miR-21 is independently transcribed by its own promoter regions and terminated with its own poly(A) tail. After transcription, primiR- 21 is finally processed into mature miR-21. Expression of miR-21 has been found to be deregulated in almost all types of cancers and therefore was classified as an oncomiR. During recent years, additional roles of miR-21 in cardiovascular and pulmonary diseases, including cardiac and pulmonary fibrosis as well as myocardial infarction have been described. MiR-21 additionally regulates various immunological and developmental processes. Due to the critical functions of its target proteins in various signaling pathways, miR-21 has become an attractive target for genetic and pharmacological modulation in various disease conditions.

Circulating Long Noncoding RNA, LIPCAR, Predicts Survival in Patients With Heart Failure

Rationale: Long noncoding RNAs represent a novel class of molecules regulating gene expression. Long noncoding RNAs are present in body fluids, but their potential as biomarkers was never investigated in cardiovascular disease. Objective: To study the role of long noncoding RNAs as potential biomarkers in heart disease. Methods and Results: Global transcriptomic analyses were done in plasma RNA from patients with or without left ventricular remodeling after myocardial infarction. Regulated candidates were validated in 3 independent patient cohorts developing cardiac remodeling and heart failure (788 patients). The mitochondrial long noncoding RNA uc022bqs.1 (LIPCAR) was downregulated early after myocardial infarction but upregulated during later stages. LIPCAR levels identified patients developing cardiac remodeling and were independently to other risk markers associated with future cardiovascular deaths. Conclusions: LIPCAR is a novel biomarker of cardiac remodeling and predicts future death in patients with heart failure.Rationale: Long non-coding RNAs (lncRNAs) represent a novel class of molecules regulating gene expression. LncRNAs are present in body fluids, but their potential as biomarkers was never investigated in cardiovascular disease. Objective: Role of lncRNAs as potential biomarkers in heart disease. Methods and Results: Global transcriptomic analyses were done in plasma RNA from patients with/without left ventricular (LV)-remodeling after myocardial infarction. Regulated candidates were validated in three independent patient cohorts developing cardiac remodeling and heart failure (788 patients). The mitochondrial lncRNA uc022bqs.1 ( LIPCAR ) was down-regulated early after MI but up-regulated during later stages. LIPCAR levels identified patients developing cardiac remodeling and were independently to other risk markers associated with future cardiovascular deaths. Conclusions: LIPCAR is a novel biomarker of cardiac remodeling and predicts future death in heart failure patients.

The Circulating Long Non-Coding RNA LIPCAR Predicts Survival in Heart Failure Patients

Rationale: Long noncoding RNAs represent a novel class of molecules regulating gene expression. Long noncoding RNAs are present in body fluids, but their potential as biomarkers was never investigated in cardiovascular disease. Objective: To study the role of long noncoding RNAs as potential biomarkers in heart disease. Methods and Results: Global transcriptomic analyses were done in plasma RNA from patients with or without left ventricular remodeling after myocardial infarction. Regulated candidates were validated in 3 independent patient cohorts developing cardiac remodeling and heart failure (788 patients). The mitochondrial long noncoding RNA uc022bqs.1 (LIPCAR) was downregulated early after myocardial infarction but upregulated during later stages. LIPCAR levels identified patients developing cardiac remodeling and were independently to other risk markers associated with future cardiovascular deaths. Conclusions: LIPCAR is a novel biomarker of cardiac remodeling and predicts future death in patients with heart failure.Rationale: Long non-coding RNAs (lncRNAs) represent a novel class of molecules regulating gene expression. LncRNAs are present in body fluids, but their potential as biomarkers was never investigated in cardiovascular disease. Objective: Role of lncRNAs as potential biomarkers in heart disease. Methods and Results: Global transcriptomic analyses were done in plasma RNA from patients with/without left ventricular (LV)-remodeling after myocardial infarction. Regulated candidates were validated in three independent patient cohorts developing cardiac remodeling and heart failure (788 patients). The mitochondrial lncRNA uc022bqs.1 ( LIPCAR ) was down-regulated early after MI but up-regulated during later stages. LIPCAR levels identified patients developing cardiac remodeling and were independently to other risk markers associated with future cardiovascular deaths. Conclusions: LIPCAR is a novel biomarker of cardiac remodeling and predicts future death in heart failure patients.

Transforming Growth Factor-β–Induced Endothelial-to-Mesenchymal Transition Is Partly Mediated by MicroRNA-21

Objective—MicroRNAs are a class of small ribonucleotides regulating gene/protein targets by transcript degradation or translational inhibition. Transforming growth factor-&bgr; (TGF-&bgr;) is involved in cardiac fibrosis partly by stimulation of endothelial-to-mesenchymal transition (EndMT). Here, we investigated whether microRNA (miR)-21, a microRNA enriched in fibroblasts and involved in general fibrosis, has a role in cardiac EndMT. Methods and Results—TGF-&bgr; treatment of endothelial cells significantly increased miR-21 expression and induced EndMT characterized by suppression of endothelial and increase of fibroblast markers. Overexpression of miR-21 alone also stimulated EndMT. Importantly, miR-21 blockade by transfection of specific microRNA inhibitors partly prevented TGF-&bgr;-induced EndMT. Mechanistically, miR-21 silenced phosphatase and tensin homolog in endothelial cells, resulting in activation of the Akt-pathway. Akt inhibition partly restored TGF-&bgr;-mediated loss of endothelial markers during EndMT. In vivo, pressure overload of the left ventricle led to increased expression of miR-21 in sorted cardiac endothelial cells, which displayed molecular and phenotypic signs of EndMT. This was attenuated by treatment of mice subjected to left ventricular pressure overload with an antagomir against miR-21. Conclusion—TGF-&bgr;-mediated EndMT is regulated at least in part by miR-21 via the phosphatase and tensin homolog/Akt pathway. In vivo, antifibrotic effects of miR-21 antagonism are partly mediated by blocking EndMT under stress conditions.

Urinary miR‐210 as a Mediator of Acute T‐Cell Mediated Rejection in Renal Allograft Recipients

MicroRNAs (miRNAs) are small ribonucleotides regulating gene expression. Circulating miRNAs are remarkably stable in the blood. We tested whether miRNAs are also detectable in urine and may serve as new predictors of outcome in renal transplant patients with acute rejection. We profiled urinary miRNAs of stable transplant patients and transplant patients with acute rejection. The miR‐10a, miR‐10b and miR‐210 were strongly deregulated in urine of the patients with acute rejection. We confirmed these data in urine of a validation cohort of 62 patients with acute rejection, 19 control transplant patients without rejection and 13 stable transplant patients with urinary tract infection by quantitative RT‐PCR. The miR‐10b and miR‐210 were downregulated and miR‐10a upregulated in patients with acute rejection compared to controls. Only miR‐210 differed between patients with acute rejection when compared to stable transplant patients with urinary tract infection or transplant patients before/after rejection. Low miR‐210 levels were associated with higher decline in GFR 1 year after transplantation. Selected miRNAs are strongly altered in urine of the patients with acute renal allograft rejection. The miR‐210 levels identify patients with acute rejection and predict long‐term kidney function. Urinary miR‐210 may thus serve as a novel biomarker of acute kidney rejection.

A signature of circulating microRNAs differentiates takotsubo cardiomyopathy from acute myocardial infarction

Aims Takotsubo cardiomyopathy (TTC) remains a potentially life-threatening disease, which is clinically indistinguishable from acute myocardial infarction (MI). Today, no established biomarkers are available for the early diagnosis of TTC and differentiation from MI. MicroRNAs (miRNAs/miRs) emerge as promising sensitive and specific biomarkers for cardiovascular disease. Thus, we sought to identify circulating miRNAs suitable for diagnosis of acute TTC and for distinguishing TTC from acute MI. Methods and results After miRNA profiling, eight miRNAs were selected for verification by real-time quantitative reverse transcription polymerase chain reaction in patients with TTC (n = 36), ST-segment elevation acute myocardial infarction (STEMI, n = 27), and healthy controls (n = 28). We quantitatively confirmed up-regulation of miR-16 and miR-26a in patients with TTC compared with healthy subjects (both, P < 0.001), and up-regulation of miR-16, miR-26a, and let-7f compared with STEMI patients (P < 0.0001, P < 0.05, and P < 0.05, respectively). Consistent with previous publications, cardiac specific miR-1 and miR-133a were up-regulated in STEMI patients compared with healthy controls (both, P < 0.0001). Moreover, miR-133a was substantially increased in patients with STEMI compared with TTC (P < 0.05). A unique signature comprising miR-1, miR-16, miR-26a, and miR-133a differentiated TTC from healthy subjects [area under the curve (AUC) 0.835, 95% CI 0.733–0.937, P < 0.0001] and from STEMI patients (AUC 0.881, 95% CI 0.793–0.968, P < 0.0001). This signature yielded a sensitivity of 74.19% and a specificity of 78.57% for TTC vs. healthy subjects, and a sensitivity of 96.77% and a specificity of 70.37% for TTC vs. STEMI patients. Additionally, we noticed a decrease of the endothelin-1 (ET-1)-regulating miRNA-125a-5p in parallel with a robust increase of ET-1 plasma levels in TTC compared with healthy subjects (P < 0.05). Conclusion The present study for the first time describes a signature of four circulating miRNAs as a robust biomarker to distinguish TTC from STEMI patients. The significant up-regulation of these stress- and depression-related miRNAs suggests a close connection of TTC with neuropsychiatric disorders. Moreover, decreased levels of miRNA125a-5p as well as increased plasma levels of its target ET-1 are in line with the microvascular spasm hypothesis of the TTC pathomechanism.

SERCA2a gene therapy restores microRNA-1 expression in heart failure via an Akt/FoxO3A-dependent pathway.

Aims Impaired myocardial sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) activity is a hallmark of failing hearts, and SERCA2a gene therapy improves cardiac function in animals and patients with heart failure (HF). Deregulation of microRNAs has been demonstrated in HF pathophysiology. We studied the effects of therapeutic AAV9.SERCA2a gene therapy on cardiac miRNome expression and focused on regulation, expression, and function of miR-1 in reverse remodelled failing hearts. Methods and results We studied a chronic post-myocardial infarction HF model treated with AAV9.SERCA2a gene therapy. Heart failure resulted in a strong deregulation of the cardiac miRNome. miR-1 expression was decreased in failing hearts, but normalized in reverse remodelled hearts after AAV9.SERCA2a gene delivery. Increased Akt activation in cultured cardiomyocytes led to phosphorylation of FoxO3A and subsequent exclusion from the nucleus, resulting in miR-1 gene silencing. In vitro SERCA2a expression also rescued miR-1 in failing cardiomyocytes, whereas SERCA2a inhibition reduced miR-1 levels. In vivo, Akt and FoxO3A were highly phosphorylated in failing hearts, but reversed to normal by AAV9.SERCA2a, leading to cardiac miR-1 restoration. Likewise, enhanced sodium–calcium exchanger 1 (NCX1) expression during HF was normalized by SERCA2a gene therapy. Validation experiments identified NCX1 as a novel functional miR-1 target. Conclusion SERCA2a gene therapy of failing hearts restores miR-1 expression by an Akt/FoxO3A-dependent pathway, which is associated with normalized NCX1 expression and improved cardiac function.

Diabetes-Associated MicroRNAs in Pediatric Patients With Type 1 Diabetes Mellitus: A Cross-Sectional Cohort Study

CONTEXT Circulating microRNAs (miRNAs/miRs) are used as novel biomarkers for diseases. miR-21, miR-126, and miR-210 are known to be deregulated in vivo or in vitro under diabetic conditions. OBJECTIVE The aim of this study was to investigate the circulating miR-21, miR-126, and miR-210 in plasma and urine from pediatric patients with type 1 diabetes and to link our findings to cardiovascular and diabetic nephropathy risk factors in children with type 1 diabetes. DESIGN miR-21, miR-126, and miR-210 concentrations were measured with quantitative RT-PCR in plasma and urine samples from 68 pediatric patients with type 1 diabetes and 79 sex- and age-matched controls. SETTING The study consisted of clinical pediatric patients with type 1 diabetes. PATIENTS OR OTHER PARTICIPANTS Inclusion criterion for patients was diagnosed type 1 diabetes. Exclusion criteria were febrile illness during the last 3 months; chronic inflammatory or rheumatic disease; hepatitis; HIV; glucocorticoid treatment; liver, renal, or cardiac failure; or hereditary dyslipidemia. Patients were age and sex matched to controls. MAIN OUTCOME MEASURE(S) Main outcome parameters were changes in miR-21, miR-126, and miR-210 concentration in plasma and urine from type 1 diabetic patients compared with corresponding controls. RESULTS Circulating miRNA levels of miR-21 and miR-210 were significantly up-regulated in the plasma and urine of the type 1 diabetic patients. Urinary miR-126 levels in diabetic patients were significantly lower than in age- and gender-matched controls and negatively correlated between the patients glycated hemoglobin mean and miR-126 concentration value. In contrast, circulating miR-126 levels in plasma were comparable in both cohorts. For urinary miR-21, we found by an adjusted receiver-operating characteristic-curve analysis with an area under the curve of 0.78. CONCLUSIONS Type 1 diabetic pediatric patients revealed a significant deregulation of miR-21, miR-126, and miR-210 in plasma and urinary samples, which might indicate an early onset of diabetic-associated diseases.

MicroRNA-Mediated Epigenetic Silencing of Sirtuin1 Contributes to Impaired Angiogenic Responses

Rationale: Transforming growth factor (TGF)-&bgr; was linked to abnormal vessel function and can mediate impairment of endothelial angiogenic responses. Its effect on microRNAs and downstream targets in this context is not known. Objective: To study the role of microRNAs in TGF-&bgr;–mediated angiogenic activity. Methods and Results: MicroRNA profiling after TGF-&bgr; treatment of endothelial cells identified miR-30a-3p, along with other members of the miR-30 family, to be strongly silenced. Supplementation of miR-30a-3p restored function in TGF-&bgr;–treated endothelial cells. We identified the epigenetic factor methyl-CpG-binding protein 2 (MeCP2) to be a direct and functional target of miR-30a-3p. Viral overexpression of MeCP2 mimicked the effects of TGF-&bgr;, suggesting that derepression of MeCP2 after TGF-&bgr; treatment may be responsible for impaired angiogenic responses. Silencing of MeCP2 rescued detrimental TGF-&bgr; effects on endothelial cells. Microarray transcriptome analysis of MeCP2-overexpressing endothelial cells identified several deregulated genes important for endothelial cell function including sirtuin1 (Sirt1). In vivo experiments using endothelial cell–specific MeCP2 null or Sirt1 transgenic mice confirmed the involvement of MeCP2/Sirt1 in the regulation of angiogenic functions of endothelial cells. Additional experiments identified that MeCP2 inhibited endothelial angiogenic characteristics partly by epigenetic silencing of Sirt1. Conclusions: TGF-&bgr; impairs endothelial angiogenic responses partly by downregulating miR-30a-3p and subsequent derepression of MeCP2-mediated epigenetic silencing of Sirt1.

Vascular importance of the miR-212/132 cluster

RATIONALE Many processes in endothelial cells including angiogenic responses are regulated by microRNAs. However, there is limited information available about their complex cross-talk in regulating certain endothelial functions. AIM The objective of this study is to identify endothelial functions of the pro-hypertrophic miR-212/132 cluster and its cross-talk with other microRNAs during development and disease. METHODS AND RESULTS We here show that anti-angiogenic stimulation by transforming growth factor-beta activates the microRNA-212/132 cluster by derepression of their transcriptional co-activator cAMP response element-binding protein (CREB)-binding protein (CBP) which is a novel target of a previously identified pro-angiogenic miRNA miR-30a-3p in endothelial cells. Surprisingly, despite having the same seed-sequence, miR-212 and miR-132 exerted differential effects on endothelial transcriptome regulation and cellular functions with stronger endothelial inhibitory effects caused by miR-212. These differences could be attributed to additional auxiliary binding of miR-212 to its targets. In vivo, deletion of the miR-212/132 cluster increased endothelial vasodilatory function, improved angiogenic responses during postnatal development and in adult mice. CONCLUSION Our results identify (i) a novel miRNA-cross-talk involving miR-30a-3p and miR-212, which led to suppression of important endothelial genes such as GAB1 and SIRT1 finally culminating in impaired endothelial function; and (ii) microRNAs may have different biological roles despite having the same seed sequence.