Abstract
MicroRNA (miRNA) are small, single strand non-coding RNA molecules involved in the post-transcriptional regulation of target genes. Since their discovery in 1993, over 2000 miRNAs have been identified in humans and there is growing interest in both the diagnostic and therapeutic potential of miRNA. The identification of biomarkers for human disease progression remains an active area of research, and there is a growing number of miRNA and miRNA combinations that have been linked to the development and progression of numerous cardiovascular diseases, including hypertension. In 2010, Chen et al. reported in Clinical Science that cell-free circulating miRNA could serve as novel biomarkers for acute myocardial infarction [1]. In this commentary, we expand on this topic to discuss the potential of using miRNA as biomarkers for hypertension and hypertension-related end-organ damage.
Cardiovascular disease (CVD) remains the leading cause of death among both men and women in the United States. Despite decades of research and advances in the treatment of CVD, the identification of novel, early stage biomarkers remains an area of great interest [2,3]. Biomarkers have the potential to allow for both the earlier detection cardiovascular disorders as well as the development of new therapeutics to limit CVD morbidity and mortality. Cheng et al. reported in Clinical Science in 2010 that circulating levels of microRNA (miRNA)-1 strongly correlates to infarct size and severity of disease in both patients with myocardial infarction as well as in a mouse model of ischemia reperfusion cardiac injury [1]. miRNAs are small (∼22 nucleotides), single strand non-coding RNA molecules involved in the post-transcriptional regulation of target genes. miRNA-1 is a cardiac-specific miRNA; therefore, biopsy of tissue and RT-qPCR is a viable approach to measure the levels of miRNA-1 in myocardial infarction patients. However, this approach is clinically impractical. Therefore, the authors devised an assay to measure circulating miRNA-1 levels and determined an association between infarct size and miRNA-1 expression. In addition to establishing this novel connection between infarct size and circulating miRNA-1 levels, the authors also significantly contributed to the field of the measure of circulating miRNAs (c-miRNAs) as biomarkers for disease.
The field of miRNAs as biomarkers for disease and disease severity has exponentially grown since 2010, both within the field of myocardial infarction [4] and beyond [5]. There remains significant interest in miRNA's in myocardial infarction and there are several recent reviews on the topic. In particular, recent work has expanded our understanding of how miRNAs impact damaged cardiac tissue via the regulation of apoptosis, inflammation, autophagy, proliferation, remodeling and fibrosis with the potential to target miRNAs to develop novel therapies [6–8]. Study of specific miRNA signatures have also been used to discriminate between sudden cardiac death, acute myocardial infarction, and ST-segment-elevation myocardial infarction [6]. The progress made in this area and the promising nature of harnessing the potential biomarker properties and therapeutic potential of miRNA have led to studies in additional diseases. Indeed, miRNAs have been implicated in a host of diseases including, but not limited to CVD, diabetes, HIV, aging-related disorders and cancer.
| microRNA . | Disease biomarker . | Change with disease . |
|---|---|---|
| miR-1 [1] | Cardiovascular | Increases |
| hsa-miR-320d [10] | Reference miR | – |
| miR-223-3p [11] | Reference miR | – |
| miR-126-5p [11] | Reference miR | – |
| miR-202-3p [12] | Hypertension | Increases |
| miR-510 [17] | Hypertension | Increases |
| miR-3656 [20] | Hypertension | Increases |
| miR-3135b [13] | Severe hypertension | Increases |
| miR-107 [13] | Severe hypertension | Increases |
| miR-423-5p [14] | Hypertension with HFrEF | Increases |
| miR-27a [15] | New-onset hypertension | Decreases |
| miR-133a [15] | New-onset hypertension | Decreases |
| miR-126 [16] | Increased blood pressure and new-onset hypertension | Decreases |
| miR-221 [16] | Increased blood pressure and new-onset hypertension | Decreases |
| miR-222 [16] | Increased blood pressure and new-onset hypertension | Decreases |
| miR-505 [18] | Hypertension-associated endothelial dysfunction and inflammation | Increases |
| miR-122 [19] | Endothelial dysfunction in essential hypertension | Increases |
| miR-7-5p [21] | Hypertension with left ventricular hypertrophy | Increases |
| miR-26b-5p [21] | Hypertension with left ventricular hypertrophy | Increases |
| miR-155 [22] | Hypertension with left ventricular hypertrophy | Increases |
| miR-145-5p [23] | Hypertension with left ventricular hypertrophy | Increases |
| miR-451 [23] | Hypertension with left ventricular hypertrophy | Increases |
| miR-let7c [23] | Hypertension with left ventricular hypertrophy | Increases |
| miR-92a [24] | Essential hypertension with atherosclerosis | Increases |
| miR-145-5p [25] | Hypertension with atherosclerotic plaques | Increases |
| miR-195-5p [26] | Essential hypertension with Type 2 diabetes mellitus | Decreases |
| miR-215 [27] | Preeclampsia | Increases |
| miR-155 [27] | Preeclampsia | Increases |
| miR-650 [27] | Preeclampsia | Increases |
| miR-210 [27] | Preeclampsia | Increases |
| miR-21 [27] | Preeclampsia | Increases |
| miR-18a [27] | Preeclampsia | Decreases |
| miR-19b1 [27] | Preeclampsia | Decreases |
| miR-31-5p [29] | Preeclampsia | Increases |
| miR155-5p [29] | Preeclampsia | Increases |
| miR-214-3p [29] | Preeclampsia | Increases |
| miR-1290-3p [29] | Preeclampsia | Decreases |
| miR-15a-5p [31] | Preeclampsia | Increases |
| miR-518b [27] | Severe preeclampsia | Increases |
| miR-29a [27] | Severe preeclampsia | Increases |
| miR-144 [27] | Severe preeclampsia | Decreases |
| miR-15b [27] | Severe preeclampsia | Decreases |
| miR-200a-3p [30] | Hypertensive disorders complicating pregnancy (gestational hypertension, mild preeclampsia, and severe preeclampsia) | Increases |
| microRNA . | Disease biomarker . | Change with disease . |
|---|---|---|
| miR-1 [1] | Cardiovascular | Increases |
| hsa-miR-320d [10] | Reference miR | – |
| miR-223-3p [11] | Reference miR | – |
| miR-126-5p [11] | Reference miR | – |
| miR-202-3p [12] | Hypertension | Increases |
| miR-510 [17] | Hypertension | Increases |
| miR-3656 [20] | Hypertension | Increases |
| miR-3135b [13] | Severe hypertension | Increases |
| miR-107 [13] | Severe hypertension | Increases |
| miR-423-5p [14] | Hypertension with HFrEF | Increases |
| miR-27a [15] | New-onset hypertension | Decreases |
| miR-133a [15] | New-onset hypertension | Decreases |
| miR-126 [16] | Increased blood pressure and new-onset hypertension | Decreases |
| miR-221 [16] | Increased blood pressure and new-onset hypertension | Decreases |
| miR-222 [16] | Increased blood pressure and new-onset hypertension | Decreases |
| miR-505 [18] | Hypertension-associated endothelial dysfunction and inflammation | Increases |
| miR-122 [19] | Endothelial dysfunction in essential hypertension | Increases |
| miR-7-5p [21] | Hypertension with left ventricular hypertrophy | Increases |
| miR-26b-5p [21] | Hypertension with left ventricular hypertrophy | Increases |
| miR-155 [22] | Hypertension with left ventricular hypertrophy | Increases |
| miR-145-5p [23] | Hypertension with left ventricular hypertrophy | Increases |
| miR-451 [23] | Hypertension with left ventricular hypertrophy | Increases |
| miR-let7c [23] | Hypertension with left ventricular hypertrophy | Increases |
| miR-92a [24] | Essential hypertension with atherosclerosis | Increases |
| miR-145-5p [25] | Hypertension with atherosclerotic plaques | Increases |
| miR-195-5p [26] | Essential hypertension with Type 2 diabetes mellitus | Decreases |
| miR-215 [27] | Preeclampsia | Increases |
| miR-155 [27] | Preeclampsia | Increases |
| miR-650 [27] | Preeclampsia | Increases |
| miR-210 [27] | Preeclampsia | Increases |
| miR-21 [27] | Preeclampsia | Increases |
| miR-18a [27] | Preeclampsia | Decreases |
| miR-19b1 [27] | Preeclampsia | Decreases |
| miR-31-5p [29] | Preeclampsia | Increases |
| miR155-5p [29] | Preeclampsia | Increases |
| miR-214-3p [29] | Preeclampsia | Increases |
| miR-1290-3p [29] | Preeclampsia | Decreases |
| miR-15a-5p [31] | Preeclampsia | Increases |
| miR-518b [27] | Severe preeclampsia | Increases |
| miR-29a [27] | Severe preeclampsia | Increases |
| miR-144 [27] | Severe preeclampsia | Decreases |
| miR-15b [27] | Severe preeclampsia | Decreases |
| miR-200a-3p [30] | Hypertensive disorders complicating pregnancy (gestational hypertension, mild preeclampsia, and severe preeclampsia) | Increases |
Of interest, there are growing evidence to implicate circulating miRs as emerging biomarkers for the risk, severity and potential treatment of hypertension (Table 1). Hypertension is a known risk factor for numerous CVDs, including myocardial infarction. Approximately half of adults in the United States are hypertensive, leading to premature CVD morbidity and mortality [9]. The therapeutic potential to use the measurement of c-miRNAs to gain insight into blood pressure control opens wide possibilities for the application of miRNAs as biomarkers of, and targets for disease in humans. Moreover, gaining disease insight from a routine blood draw for miRNA titration versus tissue-specific miRNA expression increases the practical and translational use of miRNAs in the diagnosis and treatment of CVD.
Despite the potential of miRNAs to serve as biomarkers, there are numerous challenges to the use of c-miRNA as a biomarker [1]. In particular, housekeeping genes for circulating miRNAs are not readily identifiable as normalization factors for PCR in tissues, such as 18s, and are not useful in the measurement of c-miRNAs due to the highly variable expression patterns of these gene expression between patients. One option is to utilize serum volume expressed as pmol/l as a normalization [1], yet other studies have identified additional circulating housekeeping genes including both individual miRNAs and combinations. A recent report indicates that hsa-miR-320d is an appropriate reference miRNA in reducing the technical variability among the experimental replicates, therefore highlighting inter-cohort differences [10]. To directly address concerns regarding data normalization strategies for microRNA studies in hypertension, genome-wide profiling of 754 miRNAs was performed in plasma of 36 European American individuals with uncomplicated hypertension [11]. Eighty-one miRNAs were consistently detected in all samples, and a combination of miR-223-3p and 126-5p were identified to normalize miRNA across microarrays, single qPCR assay platforms and ancestry groups.
miRNA in hypertension
Since the publication by Cheng et al. several c-miRNAs have been reported to increase in hypertensive patients. In a cohort of 182 essential hypertension patients and 159 healthy control patients, c-miRNA 202-3p levels were significantly higher in hypertension patients [12]. Interestingly, blood levels of miRNA-202-3p positively correlated with the male gender, drinking and body mass index (BMI), providing a more accurate prediction of hypertension when combined with traditional risk factors for hypertension. The severity of hypertension has also been linked to c-miRNAs. Circulating miRNA-3135b and miRNA-107 are more highly expressed in patients with severe hypertensive versus control patients [13]. In contrast, additional c-miRNAs are negative predictors of hypertension in clinical studies. MicroRNA-423-5p has been suggested to serve as a potential biomarker for assessing the therapeutic effect of cardiac rehabilitation in hypertensive patients with heart failure with a moderately reduced ejection fraction [14]. Moreover, the development of hypertension is associated with decreases in miRNA-27a and miRNA-133a [15], and a 5-year longitudinal study of 192 participants found that serum levels of miRNA-126, miRNA-221 and miRNA-222 were significantly and negatively associated with changes in systolic blood pressure (SBP) and the rate of change of SBP [16]. Post-translational modification of miRNAs, including methylation of c-miRNA 510 [17], has also been suggested to serve as promising biomarkers for hypertensive patients. Further studies are needed to fully define the relationship between miRNAs and the development and severity of hypertension to determine the predicative value of individual and combinations of c-miRNA in various cohorts of patients diversified by ethnicity, sex and age to enable clinical medicine to advance to including these measures as diagnostic tools in cardiovascular medicine.
Circulating miRNA as a marker of hypertensive injury
Hypertension is in and of itself a risk factor and marker of CVD and hypertension increases the risk of end-organ damage, including heart failure, endothelial dysfunction and pregnancy complications such as preeclampsia. The ability to measure and associate c-miRNAs in hypertensive cohorts with blood pressure values raises the potential to also use c-miRNA as predictors of end-organ damage. Indeed, miR-505 treatment increases blood pressure, endothelial dysfunction, vascular and renal inflammation in experimental animals, and plasma levels of miRNA-505 are positively correlated with SBP and C-reactive protein levels in human subjects [18]. Consistent with these findings, expression of miRNA-122 is significantly higher in plasma of patients with hypertension compared with control subjects, and among patients with hypertension high expression of miRNA-122 contributed to endothelial dysfunction by suppressing the expression of the cationic amino acid transporter 1 (CAT-1) [19]. Additional studies have found that miRNA-3656, which is up-regulated in patients with hypertension, induces injury in human umbilical venous endothelial cells (HUVECs) by uncoupling endothelial nitric oxide synthase (eNOS) [20]. Greater understanding of the molecular mechanisms by which circulating miRNAs regulate the vasculature will provide novel insight into the treatment of one of the primary hallmarks of hypertension, endothelial dysfunction.
Hypertension also induces stress on the heart, increasing the risk of heart failure, which is characterized by left ventricular hypertrophy (LVH). Using miRNA PCR arrays to screen serum miRNAs profiles of hypertensive patients with LVH, hypertensive patients without LVH and healthy control subjects, 69 miRNAs were differentially expressed between hypertensive patients and control subjects (24 up-regulated miRNAs and 45 down-regulated miRNAs), and 70 miRNAs were differentially expressed between hypertensive patients with LVH and those without (56 miRNAs up-regulated and 14 miRNAs down-regulated) [21]. The two most differentially expressed up-regulated miRNAs between the three groups were miRNA-7-5p and miRNA-26b-5p. Additional studies confirmed significantly greater circulating levels of miRNA-7-5p and miRNA-26b-5p in hypertensive patients with LVH. Circulating mRNA-155 is also positively associated with both the development of LVH and the severity of hypertension [22], and miRNA-145-5p, miRNA-451, and let7c are greater in hypertensive patients with LVH compared with hypertensive patients without LVH [23]. In addition, c-miRNA has been suggested to predict the development of atherosclerosis (c-miRNA 92a [24] and c-miRNA 145-5p [25]) and Type 2 diabetes (c-mRNA 195-5p [26]) in patients with hypertension. Together, these studies further support the use of c-miRNA as a potential non-invasive marker of hypertensive end organ damage. Moreover, the use of a c-mRNA panel in hypertensive patients may extend beyond simply prediction, and ideally prevention, of hypertension but also allow for the development of prevention strategies to limit injury and improve health outcomes.
Circulating miRNA as a marker of hypertension in pregnancy
Pregnancy-induced hypertension, notably preeclampsia, is a growing clinical burden with long-term health consequences for both the mother and offspring of the pregnancy. Preeclampsia is characterized by new-onset hypertension in pregnancy and is a difficult syndrome to predict and treat due to limitations regarding the use and safety of hypertension treatments in pregnant patients and lack of information regarding the mechanisms of disease that would lead to effective management or prevention strategies. Pregnancy is also a unique clinical challenge due to the short window for biomarker measurement, diagnosis and treatment within the gestation period. Therefore, easily identifiable circulating biomarkers are of significant clinical value in pregnancy-related complications, and c-mRNAs may provide increased accuracy to predict disorders in these vulnerable patients. miRNA expression profiles were examined in plasma of women with preeclampsia or uncomplicated pregnancies [27]. miRNA-215, miRNA-155, miRNA-650, miRNA-210 and miRNA-21 were up-regulated, and miRNA-18a and miRNA-19b1 were down-regulated in women with preeclampsia compared with control women. These same c-miRNAs were differentially expressed between women with severe versus mild preeclampsia, and severe preeclampsia was also associated with increased miRNA-518b and miRNA-29a and decreased miRNA-144 and miRNA-15b. A more comprehensive panel of c-mRNAs associated with both preeclampsia as well as small for gestational age births, a marker of fetal growth restriction, was recently reported [28] supporting the potential and interest in cataloging miRNA expressions as more specific markers of preeclamptic disease.
Individual miRNAs that have been implicated in disease have also been studied in hypertensive pregnancy disorders. Measurement of c-miRNA in serum from 92 patients with preeclampsia and an equal number of healthy controls identified elevated levels of miRNA-31-5p, miRNA-155-5p and miRNA-214-3p, which also correlated with clinical presentation of proteinuria, indicating renal complications in preeclampsia [29]. In contrast, miRNA-1290-3p level decreased with preeclampsia. Importantly, the level of each elevated miRNA had greater than 90% diagnostic accuracy, which was further increased by analyzing its ratio relative to that of miRNA-1290-3p. In a recent 2022 report, c-mRNA-200A was measured in women with gestational hypertension, mild preeclampsia, severe preeclampsia and normal pregnancy. C-miRNA-200A was increased in all women with hypertensive disorders compared with normal pregnant women, and the severity of hypertension positively correlated with the levels of c-miRNA-200A [30]. Interestingly, placental exosomes in circulation are also potential targets for biomarker identification in preeclamptic patients and in one cohort miRNA 15A-5p secreted by placental exosomes promoted preeclampsia [31]. Collectively, these studies indicate that c-mRNA may prove a useful obstetric tool to predict, and potentially prevent, preeclampsia in pregnant women; however, significantly more study is warranted.
miRNA therapeutic potential
The ability of miRNA to regulate gene transcription and the known impact of miRNA on the control of blood pressure make targeting miRNA to treat hypertension attractive. The potential for using miRNA in the treatment of a variety of human diseases is being explored, with a current focus on cancer treatment, and a handful of miRNA-based treatments are in the early stages of clinical trial [32,33]. While there are preclinical data supporting a functional role for c-miRNAs in the treatment of hypertension [34], much work remains to be done to understand how individual miRNAs control blood pressure and what miRNAs should be targeted in which populations. Regardless, continued growing interest in miRNAs and miRNA panels to predict how blood pressure will change and the impact on target organs in specific populations will continue to expand our understanding of the pathogenesis of disease and to provide evidentiary support for further study of c-miRNAs as a future clinical consideration in the treatment of hypertension. Continued study, of which Cheng et al. significantly contributed in 2010 [1], will determine whether future therapeutics will receive approval and provide novel approaches for hypertension treatment.
Data Availability
This commentary does not include any original data.
Competing Interests
The authors declare that there are no competing interests associated with the manuscript.
CRediT Author Contribution
Jessica L. Faulkner: Conceptualization, Writing—original draft, Writing—review & editing. Jennifer C. Sullivan: Conceptualization, Funding acquisition, Writing—original draft, Writing—review & editing.
