Detection and comparison of microRNA expression in the serum of Doberman Pinschers with dilated cardiomyopathy and healthy controls

A review on microRNA detection and expression studies in dogs

MicroRNAs (miRNAs) are small non-coding RNAs that function by post-transcriptional regulation of gene expression. Their stability and abundance in tissue and body fluids makes them promising potential tools for both the diagnosis and prognosis of diseases and attractive therapeutic targets in humans and dogs. Studies of miRNA expression in normal and disease processes in dogs are scarce compared to studies published on miRNA expression in human disease. In this literature review, we identified 461 peer-reviewed papers from database searches using the terms "canine," "dog," "miRNA," and "microRNA"; we screened 244 for inclusion criteria and then included a total of 148 original research peer-reviewed publications relating to specific miRNA expression in canine samples. We found an overlap of miRNA expression changes between the four groups evaluated (normal processes, non-infectious and non-inflammatory conditions, infectious and/or inflammatory conditions, and neoplasia) in 39 miRNAs, 83 miRNAs in three of the four groups, 110 miRNAs in two of the three groups, where 158 miRNAs have only been reported in one of the groups. Additionally, the mechanism of action of these overlapping miRNAs varies depending on the disease process, elucidating a need for characterization of the mechanism of action of each miRNA in each disease process being evaluated. Herein we also draw attention to the lack of standardization of miRNA evaluation, consistency within a single evaluation method, and the need for standardized methods for a direct comparison.

MicroRNA profiling of cerebrospinal fluid from dogs with steroid responsive meningitis-arteritis and meningoencephalitis of unknown origin

Introduction

Non-infectious inflammatory diseases of the central nervous system in dogs, such as steroid responsive meningitis-arteritis (SRMA) and meningoencephalitis of unknown origin (MUO), represent a common clinical challenge that needs extensive and multimodal work-up to reach a presumptive diagnosis. Both diseases are presumably caused by dysregulations of the immune system, but further research is needed in order to understand the molecular mechanisms behind each disease and to optimize treatment.

Methods

By next-generation sequencing and subsequent quantitative real-time PCR (qPCR) verification, we designed a prospective case-control pilot study to analyze the small RNA profiles of cerebrospinal fluid from dogs suffering from MUO (N = 5), dogs suffering from SRMA (N = 8), and healthy dogs (N = 5) presented for elective euthanasia used as the Control group.

Results

Our results showed an overall enrichment in Y-RNA fragments across all samples, followed by microRNAs (miRNAs) and ribosomal RNAs as the major findings. Additional traces of short RNA reads mapped to long non-coding RNAs and protein-coding genes were also found. From the detected canine miRNAs, miR-21, miR-486, miR-148a, miR-99a, miR-191 and miR-92a were among the most abundant. Dogs with SRMA showed higher differences in miRNA abundance than dogs with MUO when compared to healthy dogs, and miR-142-3p was consistently detected as differentially upregulated in both diseases, although at a low concentration. Moreover, miR-405-5p and miR-503-5p showed different profiles between SRMA and MUO dogs. Subsequent qPCR analyses confirmed miR-142-5p, miR-191-5p and miR-92a-3p as significantly upregulated miRNAs in dogs with SRMA and/or MUO.

Discussion

Cerebrospinal fluid is a challenging biological material to use for profiling miRNAs due to the low content of circulating RNAs. Despite this, we could confirm several miRNAs being differentially abundant when comparing healthy dogs and dogs with MUO and SRMA, respectively. The results of this study indicate a potential role of miRNAs in the underlying molecular mechanisms of these diseases and establish the basis for further studies.

Emerging Roles of Micrornas in Veterinary Cardiology

Over the last years, the importance of microRNAs (miRNAs) has increasingly been recognised. Each miRNA is a short sequence of non-coding RNA that influences countless genes' expression and, thereby, contributes to several physiological pathways and diseases. It has been demonstrated that miRNAs participate in the development of many cardiovascular diseases (CVDs). This review synopsises the most recent studies emphasising miRNA's influence in several CVDs affecting dogs and cats. It provides a concise outline of miRNA's biology and function, the diagnostic potential of circulating miRNAs as biomarkers, and their role in different CVDs. It also discusses known and future roles for miRNAs as potential clinical biomarkers and therapeutic targets. So, this review gives a comprehensive outline of the most relevant miRNAs related to CVDs in Veterinary Medicine.

Identification and Characterization of Circulating MicroRNAs as Novel Biomarkers in Dogs With Heart Diseases

Background: Previous studies in humans have confirmed dysregulations of circulating microRNAs (miRNAs) in patients with various cardiovascular diseases. However, studies on circulating miRNAs in dogs with various heart diseases are limited in number. This study aimed to identify significantly dysregulated circulating miRNAs and characterize them as novel biomarkers in dogs with heart diseases. Materials and Methods: Circulating levels of 11 miRNAs were investigated in serum samples of 82 dogs (72 with heart diseases and 10 healthy dogs) using quantitative reverse transcription-polymerase chain reaction. The results were correlated to clinical data including echocardiographic results and N-terminal pro B-type natriuretic peptide (NT-proBNP) levels. Results: Upregulation of cfa-miR-130b was observed in dogs with myxomatous mitral valve degeneration (MMVD) stage B, patent ductus arteriosus, and pulmonic stenosis. In dogs with MMVD stage B, cfa-miR-130b was upregulated and correlated with clinical indices. In receiver operating characteristic (ROC) analysis, cfa-miR-130b accurately distinguished dogs with diseases from healthy dogs. We also observed that cfa-miR-375 and cfa-let-7b were upregulated in dogs with concentric cardiac hypertrophy. The cfa-miR-375 was correlated with concentric hypertrophy indices and was an accurate indicator of concentric hypertrophy in ROC analysis. Conclusions: The miRNAs identified in this study may be used as novel biomarkers and possible candidates for therapeutic targets in various canine heart diseases.

Expression Profile of Circulating MicroRNAs in Dogs With Cardiac Hypertrophy: A Pilot Study

This study aimed to identify the expression profile of circulating microRNAs in dogs with eccentric or concentric cardiac hypertrophy. A total of 291 microRNAs in serum samples of five dogs with myxomatous mitral valve degeneration (MMVD) and five dogs with pulmonic stenosis (PS) were compared with those of five healthy dogs using microarray analysis. Results of microarray analysis revealed up-regulation of cfa-miR-130b [fold change (FC) = 2.13, p = 0.014), down-regulation of cfa-miR-375 (FC = 1.51, p = 0.014), cfa-miR-425 (FC = 2.56, p = 0.045), cfa-miR-30d (FC = 3.02, p = 0.047), cfa-miR-151 (FC = 1.89, p = 0.023), cfa-miR-19b (FC = 3.01, p = 0.008), and cfa-let-7g (FC = 2.53, p = 0.015) in MMVD group which showed eccentric cardiac hypertrophy, up-regulation of cfa-miR-346 (FC = 2.74, p = 0.032), down-regulation of cfa-miR-505 (FC = 1.56, p = 0.016) in PS group which showed concentric cardiac hypertrophy, and down-regulation of cfa-miR-30c (FC = 3.45, p = 0.013 in MMVD group; FC = 3.31, p = 0.014 in PS group) and cfa-let-7b (FC = 11.42, p = 0.049 in MMVD group; FC = 5.88, p = 0.01 in PS group) in both MMVD and PS groups. In addition, the unsupervised hierarchical clustering of differentially expressed microRNAs in each group resulted in complete separation of healthy dogs from dogs with heart diseases. Therefore, eleven microRNAs among 291 microRNAs were identified as differentially expressed circulating microRNAs related to MMVD or PS in dogs. This pilot study demonstrates that the microRNAs identified in this study could be possible candidates for novel biomarker or therapeutic target related to cardiac hypertrophy in dogs.

Liquid biopsy technologies for hematological diseases

Since the discovery of circulating tumor cells in 1869, technological advances in studying circulating biomarkers from patients' blood have made the diagnosis of nonhematologic cancers less invasive. Technological advances in the detection and analysis of biomarkers provide new opportunities for the characterization of other disease types. When compared with traditional biopsies, liquid biopsy markers, such as exfoliated bladder cancer cells, circulating cell-free DNA (cfDNA), and extracellular vesicles (EV), are considered more convenient than conventional biopsies. Liquid biopsy markers undoubtedly have the potential to influence disease management and treatment dynamics. Our main focuses of this review will be the cell-based, gene-based, and protein-based key liquid biopsy markers (including EV and cfDNA) in disease detection, and discuss the research progress of these biomarkers used in conjunction with liquid biopsy. First, we highlighted the key technologies that have been broadly adopted used in hematological diseases. Second, we introduced the latest technological developments for the specific detection of cardiovascular disease, leukemia, and coronavirus disease. Finally, we concluded with perspectives on these research areas, focusing on the role of microfluidic technology and artificial intelligence in point-of-care medical applications. We believe that the noninvasive capabilities of these technologies have great potential in the development of diagnostics and can influence treatment options, thereby advancing precision disease management.

Review of canine dilated cardiomyopathy in the wake of diet-associated concerns

Dilated cardiomyopathy (DCM) has been in the literature and news because of the recent opinion-based journal articles and public releases by regulatory agencies. DCM is commonly associated with a genetic predisposition in certain dog breeds and can also occur secondary to other diseases and nutritional deficiencies. Recent communications in veterinary journals have discussed a potential relationship between grain-free and/or novel protein diets to DCM, citing a subjective increase in DCM in dog breeds that are not known to have a genetic predisposition for the disease. This literature review describes clinical presentations of DCM, common sequelae, treatment and preventative measures, histopathologic features, and a discussion of the varied etiological origins of the disease. In addition, current literature limitations are addressed, in order to ascertain multiple variables leading to the development of DCM. Future studies are needed to evaluate one variable at a time and to minimize confounding variables and speculation. Furthermore, to prevent sampling bias with the current FDA reports, the veterinary community should be asked to provide information for all cases of DCM in dogs. This should include cases during the same time period, regardless of the practitioner's proposed etiology, due to no definitive association between diets with specific characteristics, such as, but not limited to, grain-free diets and those containing legumes, novel protein diets, and those produced by small manufacturers to DCM in dogs. In summary, in order to determine if certain ingredients, categories of diets, or manufacturing processes are related to an increased risk of DCM, further studies investigating these variables are necessary.

Diagnostic methods for the canine idiopathic dilated cardiomyopathy: A narrative evidence-based rapid review

Idiopathic dilated cardiomyopathy (DCM) is an important etiology of mortality and morbidity in dogs and its diagnosis relies on systolic dysfunction, chambers dilation, electrical instability and congestion. During the last decades veterinary cardiologists have been joining efforts to obtain diagnostic resources to correctly identify canine DCM in the preclinical stage. Unfortunately, most diagnostic resources have been used with the support of research with weak evidence, without high quality methodologies such as systematic reviews or meta-analysis. Therefore, the support of evidence-based medicine is tailored by empiricism and diagnostic criteria lose'out the ability to properly classify dogs suffering DCM. The presentation of the evidence in medicine is established by multiple sources and the most reliable source has been the presentation of evidence-based medicine from systematic reviews and meta-analysis. Rapid reviews can be interpreted as a pragmatic approach to systematic reviews and although a rapid review follows most of the critical steps of a systematic review to provide timely evidence, some components of a systematic review process are either simplified or omitted. The objective of this narrative evidence-based rapid review is twofold. First: To recognize and to stratify the level of evidence offered by rigorous selected papers about the diagnosis of DCM. Second: To classify the degree of clinical recommendation of the diagnostic resources available.

Analysis of Effect of Schisandra in the Treatment of Myocardial Infarction Based on Three-Mode Gene Ontology Network

Schisandra chinensis is a commonly used traditional Chinese medicine, which has been widely used in the treatment of acute myocardial infarction in China. However, it has been difficult to systematically clarify the major pharmacological effect of Schisandra, due to its multi-component complex mechanism. In order to solve this problem, a comprehensive network analysis method was established based-on “component–gene ontology–effect” interactions. Through the network analysis, reduction of cardiac preload and myocardial contractility was shown to be the major effect of Schisandra components, which was further experimentally validated. In addition, the expression of NCOR2 and NFAT in myocyte were experimentally confirmed to be associated with Schisandra in the treatment of AMI, which may be responsible for the preservation effect of myocardial contractility. In conclusion, the three-mode gene ontology network can be an effective network analysis workflow to evaluate the pharmacological effects of a multi-drug complex system.

Screening for Circulating MiR-208a and -b in Different Cardiac Arrhythmias of Dogs

Introduction

In recent years, the high sensitivity and specificity of novel miRNA biomarkers have been utilised for early diagnosis and treatment monitoring of various diseases. Previous reports showed that abnormal expression of miR-208 in mice resulted in the development of an aberrant cardiac conduction system and consecutive arrhythmias. On the other hand, a study on infarcted human heart tissue showed upregulation of miR-208a in subjects with ventricular tachyarrhythmias compared to healthy controls. We prospectively investigated the expression of miR-208a and -208b in the serum of dogs presenting different cardiac arrhythmias.

Material and Methods

A total of 28 dogs with atrial fibrillation (n = 8), ventricular premature contractions (n=6), conduction system disturbances (n = 7), and free of heart conditions (as controls) (n = 7) were enrolled in the study. Total RNA was extracted from serum samples and miR-208a and -b, miR-16 as well as a cel-miR-39-5p spike-in were analysed with qPCR and ddPCR.

Results

miR-208a and miR-208b were not expressed in any of the samples. The calculated ddPCR miR-16 relative expression (normalised with cel-miR-39 spike-in) showed a good correlation (r = 0.82; P < 0.001) with the qPCR results.

Conclusion

This outcome warrants further investigation, possibly focusing on tissue expression of miR-208 in the canine heart.

Inherited cardiomyopathies in veterinary medicine

Comparative and translation medicine is of particular value within the field of inherited cardiomyopathies. Despite massive advances in understanding the functional role of mutations in human cardiomyopathies, these advances have frequently failed to translate into medical discoveries that alter patient care. One potential explanation for this failure lies in the lack of suitable translational models that adequately recapitulate human cardiovascular physiology and disease expression. The vast genetic heterogeneity that complicates human cardiomyopathy research is potentially alleviated through the study of naturally occurring large animal models of disease, where incredibly homogenous populations, like those seen in a single breed of dog or cat, may exist (Kol et al., Sci Transl Med 7:308-321, 2015; Ueda and Stern, Yale J Biol Med 90:433-448, 2017). Veterinary medicine is in a unique position to provide research resources and information that may be readily applied to human disease (Kol et al., Sci Transl Med 7:308-321, 2015). Many inherited cardiomyopathies of humans are phenotypically and genotypically similar in veterinary species and ongoing research holds promise for aiding veterinary and human patients alike (Basso et al., Circulation 109:1180-1185, 2004; Fox et al., Cardiovasc Pathol 23:28-34, 2014; Fox et al., Circulation 102:1863-1870, 2000; Kittleson et al., J Vet Cardiol 17 Suppl 1:S53-73, 2015; Ueda and Stern, Yale J Biol Med 90:433-448, 2017). This article presents the current knowledge of inherited cardiomyopathies in dogs, cats, and non-human primates, with a goal of identifying areas of translational research and future directions.

An update on canine cardiomyopathies - is it all in the genes?

Dilated cardiomyopathy is the second most common cardiac disease in dogs and causes considerable morbidity and mortality. Primary dilated cardiomyopathy is suspected to be familial, and genetic loci have been associated with the disease in a number of breeds. Because it is an adult-onset disease, usually with late onset, testing breeding dogs and bitches before breeding for a genetic mutation that could lead to dilated cardiomyopathy would be helpful to prevent disease. There is growing evidence that the genetic basis may be multigenic rather than monogenic in the majority of studied breeds. This review article describes the known genetic aspects of canine dilated cardiomyopathy and the implications of genetic tests on heart testing and the future of veterinary cardiology.

MicroRNA expression patterns in canine mammary cancer show significant differences between metastatic and non-metastatic tumours

Background

MicroRNAs may act as oncogenes or tumour suppressor genes, which make these small molecules potential diagnostic/prognostic factors and targets for anticancer therapies. Several common oncogenic microRNAs have been found for canine mammary cancer and human breast cancer. On account of this, large-scale profiling of microRNA expression in canine mammary cancer seems to be important for both dogs and humans.

Methods

Expression profiles of 317 microRNAs in 146 canine mammary tumours of different histological type, malignancy grade and clinical history (presence/absence of metastases) and in 25 control samples were evaluated. The profiling was performed using microarrays. Significance Analysis of Microarrays test was applied in the analysis of microarray data (both unsupervised and supervised data analyses were performed). Validation of the obtained results was performed using real-time qPCR. Subsequently, predicted targets for the microRNAs were searched for in miRBase.

Results

Results of the unsupervised analysis indicate that the primary factor separating the samples is the metastasis status. Predicted targets for microRNAs differentially expressed in the metastatic vs. non-metastatic group are mostly engaged in cell cycle regulation, cell differentiation and DNA-damage repair. On the other hand, the supervised analysis reveals clusters of differentially expressed microRNAs unique for the tumour type, malignancy grade and metastasis factor.

Conclusions

The most significant difference in microRNA expression was observed between the metastatic and non-metastatic group, which suggests a more important role of microRNAs in the metastasis process than in the malignant transformation. Moreover, the differentially expressed microRNAs constitute potential metastasis markers. However, validation of cfa-miR-144, cfa-miR-32 and cfa-miR-374a levels in blood samples did not follow changes observed in the non-metastatic and metastatic tumours.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3751-1) contains supplementary material, which is available to authorized users.

Dissecting the Role of the Extracellular Matrix in Heart Disease: Lessons from the Drosophila Genetic Model

The extracellular matrix (ECM) is a dynamic scaffold within organs and tissues that enables cell morphogenesis and provides structural support. Changes in the composition and organisation of the cardiac ECM are required for normal development. Congenital and age-related cardiac diseases can arise from mis-regulation of structural ECM proteins (Collagen, Laminin) or their receptors (Integrin). Key regulators of ECM turnover include matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of matrix metalloproteinases (TIMPs). MMP expression is increased in mice, pigs, and dogs with cardiomyopathy. The complexity and longevity of vertebrate animals makes a short-lived, genetically tractable model organism, such as Drosophila melanogaster, an attractive candidate for study. We survey ECM macromolecules and their role in heart development and growth, which are conserved between Drosophila and vertebrates, with focus upon the consequences of altered expression or distribution. The Drosophila heart resembles that of vertebrates during early development, and is amenable to in vivo analysis. Experimental manipulation of gene function in a tissue- or temporally-regulated manner can reveal the function of adhesion or ECM genes in the heart. Perturbation of the function of ECM proteins, or of the MMPs that facilitate ECM remodelling, induces cardiomyopathies in Drosophila, including cardiodilation, arrhythmia, and cardia bifida, that provide mechanistic insight into cardiac disease in mammals.

Omics approaches to probe markers of disease resistance in animal sciences

Disease pathways can be explained into a list of biomarkers at different scales to develop applications.

Expression Profiling of Circulating MicroRNAs in Canine Myxomatous Mitral Valve Disease

MicroRNAs (miRNAs) are small non-coding RNAs that have shown promise as noninvasive biomarkers in cardiac disease. This study was undertaken to investigate the miRNA expression profile in dogs with myxomatous mitral valve disease (MMVD). 277 miRNAs were quantified using RT-qPCR from six normal dogs (American College of Veterinary Internal Medicine Stage A), six dogs with MMVD mild to moderate cardiac enlargement (ACVIM Stage B1/B2) and six dogs with MMVD and congestive heart failure (ACVIM Stage C/D). Eleven miRNAs were differentially expressed (False Discovery Rate < 0.05). Dogs in Stage B1/B2 or C/D had four upregulated miRNAs, including three cfa-let-7/cfa-miR-98 family members, while seven others were downregulated, compared to Stage A. Expression of six of the 11 miRNAs also were significantly different between dogs in Stage C/D and those in Stage B1/B2. The expression changes were greater as disease severity increased. These miRNAs may be candidates for novel biomarkers and may provide insights into genetic regulatory pathways in canine MMVD.

Plasma miRNAs as potential biomarkers of chronic degenerative valvular disease in Dachshunds

BACKGROUND

Endocardiosis is the most common heart disease in Dachshunds and is therefore an important cause of cardiac morbidity and death. In recent years we have observed an increasing interest in the development of new genetic and genomic markers of heart disease. The discovery of miRNAs circulating in biofluids such as plasma or serum aroused researchers' interest in using them as potential biomarkers. In the present study we analysed the expression of 9 miRNAs described in literature as being involved in cardiovascular pathology in the plasma of dogs suffering from endocardiosis.

RESULTS

Expression analysis using the Real-time PCR method revealed that two out of nine miRNAs were significantly downregulated: the expression of miR-30b differed between ACVIM stage B and stage A (control) dogs; the expression of mi-133b differed ACVIM stage C and stage A dogs. 5 miRNAs (miR-125, miR-126, miR-21, miR-29b and miR-30b) showed a trend of downregulation in the ACVIM C group. Levels of miR-423 were the same in healthy and diseased dogs. Expression of miR-208a and 208b was not detected.

CONCLUSIONS

miR-30b could be a potential biomarker of ACVIM stage B heart failure in Dachshunds with endocardiosis and miR-133b could be a potential biomarker of ACVIM stage C. The lack of expression or lack of significant changes in expression in 7 miRNAs which are potential biomarkers of heart diseases in humans proves that findings from human medicine are not always directly reflected in veterinary medicine.

Insights into morphology and disease from the dog genome project

Although most modern dog breeds are less than 200 years old, the symbiosis between man and dog is ancient. Since prehistoric times, repeated selection events have transformed the wolf into man's guardians, laborers, athletes, and companions. The rapid transformation from pack predator to loyal companion is a feat that is arguably unique among domesticated animals. How this transformation came to pass remained a biological mystery until recently: Within the past decade, the deployment of genomic approaches to study population structure, detect signatures of selection, and identify genetic variants that underlie canine phenotypes is ushering into focus novel biological mechanisms that make dogs remarkable. Ironically, the very practices responsible for breed formation also spurned morbidity; today, many diseases are correlated with breed identity. In this review, we discuss man's best friend in the context of a genetic model to understand paradigms of heritable phenotypes, both desirable and disadvantageous.

MicroRNAs: history, biogenesis, and their evolving role in animal development and disease

The discovery of microRNAs (miRNAs) in 1993 followed by developments and discoveries in small RNA biology have redefined the biological landscape by significantly altering the longstanding dogmas that defined gene regulation. These small RNAs play a significant role in modulation of an array of physiological and pathological processes ranging from embryonic development to neoplastic progression. Unique miRNA signatures of various inherited, metabolic, infectious, and neoplastic diseases have added a new dimension to the studies that look at their pathogenesis and highlight their potential to be reliable biomarkers. Also, altering miRNA functionality and the development of novel in vivo delivery systems to achieve targeted modulation of specific miRNA function are being actively pursued as novel approaches for therapeutic intervention in many diseases. Here we review the current body of knowledge on the role of miRNAs in development and disease and discuss future implications.

Analysis of circulating microRNAs in adrenocortical tumors

Differential diagnosis of adrenocortical adenoma (ACA) and carcinoma is of pivotal clinical relevance, as the prognosis and clinical management of benign and malignant adrenocortical tumors (ACTs) is entirely different. Circulating microRNAs (miRNAs) are promising biomarker candidates of malignancy in several tumors; however, there are still numerous technical problems associated with their analysis. The objective of our study was to investigate circulating miRNAs in ACTs and to evaluate their potential applicability as biomarkers of malignancy. We have also addressed technical questions including the choice of profiling and reference gene used. A total of 25 preoperative plasma samples obtained from patients with ACAs and carcinomas were studied by microarray and quantitative real-time PCR. None of the three miRNAs (hsa-miR-192, hsa-mir-197 and hsa-miR-1281) found as differentially expressed in plasma samples in our microarray screening could be validated by quantitative real-time PCR. In contrast, of the selected eight miRNAs reported in the literature as differentially expressed in ACT tissues, five (hsa-miR-100, hsa-miR-181b, hsa-miR-184, hsa-miR-210 and hsa-miR-483-5p) showed a statistically significant overexpression in adrenocortical cancer vs adenoma when normalized on hsa-miR-16 as a reference gene. Receiver operator characteristic analysis of data revealed that the combination of dCThsa-miR-210 - dCThsa-miR-181b and dCThsa-miR-100/dCThsa-miR-181b showed the highest diagnostic accuracy (area under curve 0.87 and 0.85, respectively). In conclusion, we have found significant differences in expression of circulating miRNAs between ACAs and carcinomas, but their diagnostic accuracy is not yet high enough for clinical application. Further studies on larger cohorts of patients are needed to assess the diagnostic and prognostic potential application of circulating miRNA markers.