Evaluation of microRNA stability in feces from healthy dogs

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.

Characterization of canine intestinal microRNA expression in inflammatory bowel disease and T-cell lymphoma

Differentiating between canine inflammatory bowel disease (IBD) and intestinal T-cell lymphoma by histopathological examination of endoscopically-derived intestinal biopsies can be challenging and involves an invasive procedure requiring specialized equipment and training. A rapid, non-invasive method of diagnosis, such as blood or faecal analysis for a conserved and stable biomarker, would be a useful adjunct or replacement. Studies on dogs and humans with various types of lymphoma have shown altered microRNA (miRNA) expression patterns in blood, faeces and tissues indicating their potential use as biomarkers of disease. The present study used residual archived endoscopically-derived, formalin-fixed, paraffin-embedded (FFPE) duodenal tissue taken from pet dogs undergoing routine investigation of gastrointestinal disease. The dogs had previously been diagnosed with either normal/minimal intestinal inflammation, severe IBD or intestinal T-cell lymphoma. Next generation sequencing with qPCR validation was used to elucidate differentially expressed miRNAs between groups. Our results show that miRNA can be extracted from archived endoscopically-derived FFPE tissues from the canine duodenum and used to differentiate normal/minimally inflamed canine duodenal tissue from severe lymphoplasmacytic IBD and T-cell lymphoma.

Association of fecal and serum microRNA profiles with gastrointestinal cancer and chronic inflammatory enteropathy in dogs

BACKGROUND

Reliable biomarkers to differentiate gastrointestinal cancer (GIC) from chronic inflammatory enteropathy (CIE) in dogs are needed. Fecal and serum microRNAs (miRNAs) have been proposed as diagnostic and prognostic markers of GI disease in humans and dogs.

HYPOTHESIS/OBJECTIVES

Dogs with GIC have fecal and serum miRNA profiles that differ from those of dogs with CIE.

AIMS

(a) identify miRNAs that differentiate GIC from CIE, (b) use high-throughput reverse transcription quantitative real-time PCR (RT-qPCR) to establish fecal and serum miRNA panels to distinguish GIC from CIE in dogs.

ANIMALS

Twenty-four dogs with GIC, 10 dogs with CIE, and 10 healthy dogs, all client-owned.

METHODS

An international multicenter observational prospective case-control study. Small RNA sequencing was used to identify fecal and serum miRNAs, and RT-qPCR was used to establish fecal and serum miRNA panels with the potential to distinguish GIC from CIE.

RESULTS

The best diagnostic performance for distinguishing GIC from CIE was fecal miR-451 (AUC: 0.955, sensitivity: 86.4%, specificity: 100%), miR-223 (AUC: 0.918, sensitivity: 90.9%, specificity: 80%), and miR-27a (AUC: 0.868, sensitivity: 81.8%, specificity: 90%) and serum miR-20b (AUC: 0.905, sensitivity: 90.5%, specificity: 90%), miR-148a-3p (AUC: 0.924, sensitivity: 85.7%, specificity: 90%), and miR-652 (AUC: 0.943, sensitivity: 90.5%, specificity: 90%). Slightly improved diagnostic performance was achieved when combining fecal miR-451 and miR-223 (AUC: 0.973, sensitivity: 95.5%, specificity: 90%).

CONCLUSIONS AND CLINICAL IMPORTANCE

When used as part of a diagnostic RT-qPCR panel, the abovementioned miRNAs have the potential to function as noninvasive biomarkers for the differentiation of GIC and CIE in dogs.

Stability and profiling of urinary microRNAs in healthy cats and cats with pyelonephritis or other urological conditions

Background

Specific biomarkers of pyelonephritis (PN) in cats are lacking. MicroRNAs (miRNAs) have diagnostic potential in human nephropathies.

Objectives

To investigate the presence/stability of miRNAs in whole urine of cats and the discriminatory potential of selected urinary miRNAs for PN in cats.

Animals

Twelve healthy cats, 5 cats with PN, and 13 cats with chronic kidney disease (n = 5), subclinical bacteriuria (n = 3), and ureteral obstructions (n = 5) recruited from 2 companion animal hospitals.

Methods

Prospective case‐control study. Expression profiles of 24 miRNAs were performed by quantitative PCR (qPCR). Effect of storage temperature (4°C [24 hours], −20°C, and −80°C) was determined for a subset of miRNAs in healthy cats.

Results

Urinary miR‐4286, miR‐30c, miR‐204, miR4454, miR‐21, miR‐16, miR‐191, and miR‐30a were detected. For the majority of miRNAs tested, storage at 4°C and −20°C resulted in significantly lower miRNA yield compared to storage at −80°C (mean log2fold changes across miRNAs from −0.5  ± 0.4 SD to −1.20 ± 0.4 SD (4°C versus −80°C) and from −0.7 ± 0.2 SD to −1.20 ± 0.3 SD (−20°C versus −80°C)). Cats with PN had significantly upregulated miR‐16 with a mean log2fold change of 1.0 ± 0.4 SD, compared with controls (−0.1 ± 0.2, P = .01) and other urological conditions (0.6 ± 0.3, P = .04).

Conclusions

Upregulation of miR16 might be PN‐specific, pathogen‐specific (Escherichia coli), or both.

Evaluation of fecal microRNA stability in healthy cats

Background

Gastrointestinal (GI) cancer accounts for 14% of feline malignancies. There is a great need for reliable noninvasive diagnostic biomarkers to reach a timely diagnosis and initiate treatment. Fecal microRNAs (miRNAs) could be such a biomarker and have shown great potential in colorectal screening in people but have yet to be investigated in cats.

Objectives

We aimed to evaluate the presence and stability of feline fecal miRNA under different storage conditions (room temperature [RT], 4, and −20°C) and to evaluate the expression levels of specific fecal miRNAs collected on three separate days (days 1, 4, and 7) in healthy cats.

Methods

Healthy cats were prospectively recruited. Fecal samples were collected, aliquoted, and stored for 24 hours at RT and then transferred to −20°C, stored for 24 hours at 4°C and then transferred to −20°C, or were immediately placed at −20°C on day 1 or at −20°C on days 4 and 7 postcollection. Expression of 22 miRNAs was investigated using quantitative real‐time PCR.

Results

Ten miRNA assays worked well, and one, let‐7b, was used for normalization. No differences in miRNA expression were seen between the three storage temperatures for the nine miRNAs investigated. Only miR‐26a showed a significant increase in expression between samples of days 1 and 7. The rest of the miRNAs levels were stable over time.

Conclusions

Fecal miRNA can be isolated from healthy cats. The expression was stable at different temperatures and for most of the miRNAs over time. Prospective studies evaluating fecal miRNA as biomarkers in cats with GI neoplasia are warranted.