Potential miRNAs as Diagnostic Biomarkers for Differentiating Disease States in Ulcerative Colitis: A Systematic Review

1. Introduction

Ulcerative colitis (UC) is a chronic inflammatory disorder that affects the colon and rectum. It is distinguished by continuous inflammation without healthy areas between affected regions. This inflammation is confined to the rectum and large intestine, specifically targeting the mucosal layers of the epithelium [1]. A hallmark of UC is the formation of inflammation-induced ulcers in the colon barrier. Symptoms include rectal bleeding, abdominal pain (usually in the lower left quadrant), need to defecate, and bloody diarrhea. Complications that typically arise include colonic issues such as toxic megacolons, perforations, and colitis-associated cancer. Extra-intestinal complications involve arthritis, primary sclerosing cholangitis (PSC), weight loss, anemia, and blood clots (thromboembolism), all of which significantly affect an individual's quality of life. The diagnosis is based on medical history, along with radiographic, histological, and endoscopic examinations [1,2]. Treatment options typically include immunosuppressants, anti-inflammatories, biologics, and surgery for severe cases [3,4,5]. Although its precise etiology is uncertain, UC is thought to have a complex etiology that includes both environmental and genetic variables [6]. Specific data on the global prevalence and incidence of UC are limited. However, inflammatory bowel disease (IBD) in general has a high prevalence in developed or industrialized countries, possibly due to longer life spans with disability, while its incidence appears to be decreasing. Conversely, newly or rapidly industrializing countries are experiencing an increase in incidence. For instance, the annual prevalence of UC per 100,000 persons increased significantly from 5 in 2010 to 98 in 2019 in Japan, and from 158 to 233 in the US during the same period. In the UK, as of December 2018, the prevalence and incidence of UC were reported to be 397 and 15.7 per 100,000 people, respectively, with age being a major factor influencing these trends [7,8,9,10]. Currently, UC diagnosis and monitoring rely on invasive methods like colonoscopy, alongside non-specific biomarkers such as C-reactive protein and erythrocyte sedimentation rate. While fecal calprotectin is more specific, there remains a need for improved biomarkers. MicroRNAs (miRNAs) have emerged as promising biomarkers for a variety of diseases due to their easy accessibility, and high stability, specificity, and sensitivity [11,12,13,14]. They are stable in numerous biological samples, including blood and other body fluids, and can be detected with great sensitivity. MiRNAs are small non-coding RNAs, typically 18-22 nucleotides in length, primarily involved in regulating gene expression, and have been associated with various physiological and pathological conditions, including UC. Their biogenesis involves transcription from DNA into pri-miRNA, processing into pre-miRNA, and finally maturation into miRNA. Their mechanism of action includes interaction with the 3’ UTR of target mRNA, leading to either target degradation or repression. Their presence has been detected in blood, feces, and tissue, and they have been found to be quite stable, making them excellent candidates as non-invasive biomarkers [12,15,16]. Therefore, the purpose of this systematic review is to address the question: "Do miRNAs possess the potential to serve as biomarkers for differentiating ulcerative colitis based on disease state?" This is conducted in line with the PICO ("population", "intervention", "comparison", "outcome") approach.

2.1. Search Strategy and Eligibility Criteria

The search for this systematic review was conducted from inception till 4th September 2024, in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines and registered on PROSPERO with registration No CRD42024597537 [17]. Databases utilized included PubMed, Embase and Web of Science. Search terms used included ("mir") OR ("microrna") OR ("mirna") AND ("biomarkers") AND ("ulcerative colitis") OR ("active ulcerative colitis") OR ("inactive ulcerative colitis"). Detailed search strategy is given in Table 1.

Screening of identified records was performed by two independent investigators (P.C.M and A.U.K) by title and abstract first, and later full text screening was carried out. Studies fulfilling the pre-defined inclusion criteria utilizing PICO approach were included as outlined in Table 2.

2.2. Quality Assessment and Critical Appraisal

Quality assessment of each individual study was carried out using the Newcastle–Ottawa Scale (NOS), which is based on three broad criteria the first being the Selection of population being studied, second Comparability checks for variables other than what is being studied and how well these are taken care of, and lastly how accurate are the procures carried out during these studies and are the same for both sets of populations under study. The assessment of all studies is presented in Table 3. The most frequently encountered risk of bias was that associated with control of confounding factors (all studies) and attrition bias (all studies). By adding up all the individual criteria to get the total score for each individual study according to which, five studies (71%) scored (≥56%) classified as “fair” quality with “moderate risk of bias” while two studies (29%) scored (77.77%) were classified as “good” quality having “low risk of bias”.

2.3. Data Extraction

Two reviewers independently extracted data using a standardized form. Information collected included study characteristics (first author, year, country, design), participant details (sample size, age, sex, disease status), and miRNA measurement methods (specimen type, extraction and quantification platforms, normalization techniques). Key findings on differential miRNA expression between active and inactive ulcerative colitis were recorded, along with reported diagnostic implications. Discrepancies were resolved through discussion or third-party consultation.

2.4. Data Synthesis

A narrative synthesis was conducted to evaluate the diagnostic potential of miRNAs in distinguishing active from inactive ulcerative colitis. Studies were analyzed thematically, focusing on consistent miRNA expression patterns, direction of regulation, and association with disease activity markers. Findings were grouped by miRNA identity and clinical context to identify recurring biomarkers and methodological trends.

2. Results

Seven studies have been included by following the search criteria in this systematic review. Studies included a total of 514 participants (Active UC 181, Inactive UC 116). Detailed selection strategy is given in Figure 1. Data extracted from each included study comprised of study characteristics (authors, year, design), participant details (sample size, demographics), miRNA measurement methods and key findings about miRNAs expression pattern in each individual study in different disease states, this information is collected and presented in Table 4 and Table 5.

3. Discussion

The data from the included studies reveal a significant variation in miRNA expression levels that correlate with disease activity in ulcerative colitis. Such findings offer valuable insights into miRNAs as potential diagnostic biomarkers for disease activity and progression in UC. This aligns with several reports that provide evidence of the promising role of miRNAs as diagnostic biomarkers of the development of colitis-associated cancer [18,19,20].

In this systemic review we have highlighted trends and patterns that result from differential expressions of miRNAs in active ulcerative colitis (aUC) and inactive ulcerative colitis (iUC).

In particular, Feng et al. (2012) showed a significant upregulation of miR-21 (14.7-fold) and miR-126 (18-fold) in colonic tissues of aUC vs healthy controls (HC) [15]. In contrast, there were no noticeable alterations in miRNA expression levels when comparing iUC to HC. These findings highlight the potential role of miR-21 and miR-126 as diagnostic biomarkers specifically for active UC. Indeed, miR-21's role in the negative regulation of PDCD4 [21,22], RhoB [21], and NOS-2 induced cellular damaging, while its suppression of PTEN led to PTEN repression an increase of PI3K/Akt activity, cellular pathwways that may be involved in the development of UC. Thus, the overexpression of miR-21 in macrophages could potentially trigger oxidative stress-induced cellular damage, which could be a contributing factor involved in UC pathogenesis [23,24,25,26].

Another study conducted by Coskun et al. (2013) identified a distinct set of differentially expressed miRNAs in aUC and iUC compared to HCs, such miRNAs include miR-20b (↑ P < 0.05) in aUC vs HC, miR-125b-1 (↑ P < 0.01) in aUC vs HC, let-7e (↑ P < 0.05) in iUC vs HC, miR-98 (↑ P < 0.05) in iUC vs aUC and HC [23,24,27,28]. Following up on these results, Van der Goten et al. (2014) expanded the panel of miRNAs with similar expression patterns and observed an increase of miR-21-5p, miR-31-5p, and miR-155-5pin aUC compared to HC [25,29,30,31,32]. To elucidate the functional relevance of these miRNAs, several have been investigated in the context of specific inflammatory signaling pathways. For instance, let-7e seems to be involved in Toll-like receptor (TLR)-associated signaling pathways, while miR-98 targeted pro-inflammatory genes such as MYC and IL-6 [33,34,35,36]. Notably, miR-155 inhibition reduced DSS-induced colonic damage, prevented the development of Th17 cells, and alleviated colitis associated inflammation by inactivating NF-κB signaling [37,38].Studies carried out by Yahong et al. (2018) revealed that miR-199a-5p and miR-223-3p were upregulated in aUC compared to iUC and HCs [38]. Specifically, miR-199a-5p was involved in intestinal barrier dysfunction, whereas the elevated levels of miR-223-3p might contribute to UC pathogenesis by negatively regulating autophagy and IKKα inhibition, which is a potential regulator of inflammation [24,39,40,41].

Interestingly, Peng et al. (2019) [42], reported that miR-146b-5p was overexpressed in serum samples of aUC in comparison to both iUC and HCs. These findings were further supported by El Sabbagh et al. (2023) [43], who confirmed the potential of miR-146b-5p as a biomarker indicative of active disease. Remarkably, multiple studies have identified an overlap in the overexpression of several miRNAs including miR-21, miR-223, and miR-146b-5p suggesting their promise as diagnostic biomarkers for monitoring disease activity in UC.

The consistent overexpression of miR-21, miR-223, and miR-146b-5p across multiple studies highlights their strong potential as diagnostic biomarkers. Moreover, their established roles in inflammatory pathways further support their suitability as targets for clinical research in ulcerative colitis.

4. Conclusion

Collectively these findings emphasize the involvement of specific miRNAs in ulcerative colitis pathogenesis indicating their potential as biomarkers for assessing disease activity. Future investigations involving larger cohorts are essential to further validate the diagnostic potential of miRNAs, and to explore their therapeutic applications which could ultimately enhance the clinical management of ulcerative colitis.