Reference microRNAs Research Articles

Identification of reference microRNAs in skeletal muscle of a canine model of Duchenne muscular dystrophy

Background Duchenne muscular dystrophy (DMD) is a fatal muscle wasting disease caused by mutations in the dystrophin gene. DE50-MD dogs are a canine model of DMD used as final translational models for evaluation of promising treatments. MicroRNA (miR) expressions in the muscle of DE50-MD dogs represent potential biomarkers, but stable reference miRs must first be identified. The aim of this paper was to establish a panel of reference miRs for WT and DE50-MD dogs over a range of ages and muscle groups. Methods RNA was extracted from WT and DE50-MD dog (N=6 per genotype) vastus lateralis muscle samples collected longitudinally at 3, 6, 9, 12, 15 and 18 months of age, and from muscles collected post-mortem (N=3 per genotype; cranial tibial, semimembranosus, lateral triceps and diaphragm). 87 RNAs were quantified in a subset of 6-month-old WT and DE50-MD muscles (N=4 per genotype) using the QIAcuity miFinder panel. GeNorm, BestKeeper and Normfinder were used to identify a candidate panel of the 8 most stable small RNAs, which were then quantified in all RNA samples, alongside the commonly used reference RNA snRNA U6. Results The most stable miRs of this subset were used to normalise quantities of dystromiRs miR-1, miR-133a and miR-206, and fibromiR miR-214. MicroRNAs miR-191, let-7b, miR-125a and miR-15a were the most stable miRs tested, while snRNA U6 performed poorly. DystromiR expression, normalised to the geometric mean of the panel of reference miRs, was lower for miR-1 and miR-133a in DE50-MD compared to WT muscles, while miR-206 levels did not significantly differ between genotypes. FibromiR miR-214 was 2- to 4-fold higher in DE50-MD versus WT muscles. Conclusions A normalisation factor derived from miR-191, let-7b, miR-125a and miR-15a is suitable for normalising miR expression data from WT and DE50-MD muscle over a range of ages and muscle types.

Addressing the unsolved challenges in microRNA-based biomarker development: Suitable endogenous reference microRNAs for SARS-CoV-2 infection severity

Circulating cell-free microRNAs (miRNAs) are promising biomarkers for medical decision-making. Suitable endogenous controls are essential to ensure reproducibility. We aimed to identify and validate endogenous reference miRNAs for qPCR data normalization in samples from SARS-CoV-2-infected hospitalized patients. We used plasma samples (n = 170) from COVID-19 patients collected at hospital admission (COVID-Ponent project, www.clinicaltrials.gov/NCT04824677). First, 179 miRNAs were profiled using RT–qPCR. After stability assessment, candidates were validated using the same methodology. miRNA stability was analyzed using the geNorm, NormFinder and BestKeeper algorithms. Stability was further evaluated using an RNA-seq dataset derived from COVID-19 hospitalized patients, along with plasma samples from patients with critical COVID-19 profiled using RT-qPCR. In the screening phase, after strict control of expression levels, stability assessment selected eleven candidates (miR-17-5p, miR-20a-5p, miR-30e-5p, miR-106a-5p, miR-151a-5p, miR-185-5p, miR-191-5p, miR-423-3p, miR-425-5p, miR-484 and miR-625-5p). In the validation phase, all algorithms identified miR-106a-5p and miR-484 as top endogenous controls. No association was observed between these miRNAs and clinical or sociodemographic characteristics. Both miRNAs were stably detected and showed low variability in the additional analyses. In conclusion, a 2-miRNA panel composed of miR-106a-5p and miR-484 constitutes a first-line normalizer for miRNA-based biomarker development using qPCR in hospitalized patients infected with SARS-CoV-2.

Factors influencing circulating microRNAs as biomarkers for liver diseases.

MicroRNAs (microRNAs) have been implicated to play crucial roles in various liver diseases. Hepatic microRNAs are released in to the circulation in a systematic fashion, and are, therefore, being extensively explored for their role as prognostic or diagnostic markers or therapeutic targets for numerous hepatic diseases. Advantages such as disease- or tissue-specific expression, and ease of detection have implicated circulating microRNAs (c-microRNAs) as the most desirable candidate for biomarker studies. Although several studies have explored c-microRNAs in serum or plasma, consistency of detection of microRNAs remains demanding because of many biological and methodological challenges. Lack of methodological consensus has limited the universal use of c-microRNAs as potential prognostic or diagnostic disease-specific biomarkers. In this review, we have discussed pre-analytical and analytical factors that might affect c-miRNA expression and selection of appropriate data normalization strategy by incorporating endogenous reference microRNAs. This review will aid designing of better approaches and protocols for future diagnostic research on hepatic c-microRNAs.

P029 Expression of miR-21 in mucosal biopsies give clues to anti-TNF treatment non-response in IBD children and adults

Abstract Background The use of anti-tumor necrosis factor (TNF) treatment has improved the treatment of IBD patients. However, approximately 30% of patients fail to respond to TNF inhibitors, and up to 50% of the patients who initially benefited from treatment with TNF inhibitors lose the response over time. Thus, identifying predictors of non-response and deciding on a treatment strategy according to biomarker profiles could enhance overall IBD disease management. MicroRNA-21 (miR-21) has been found to confer drug resistance to e.g. trastuzumab, 5-fluorouracil, and cisplatin. In this study, we hypothesized that miR-21 may play a role in anti-TNF drug resistance and therefore, miR-21 levels may be a predictive biomarker of anti TNF response in IBD. Methods Archived formalin-fixed, paraffin-embedded (FFPE) mucosal biopsies of IBD patients (30 adults and 27 children) were used in this study. All biopsies were collected at the time of initiation of biologics. Patients were stratified into three groups according to treatment response: Responders, Primary non-responders (PNR), and Secondary non-responders (SNR). Responders were treated with anti-TNF for a minimum of 3 years and did not experience loss of response thereafter. PNRs lost response during the first year of treatment. SNRs were treated for a minimum of 3 years with subsequent loss of response. MiR-21 expressions were quantified using Quantitative Real-Time PCR (miRCURY LNA RT Kit, Qiagen). Expression of miR-27a was used as the endogenous reference microRNA based on previous studies. Results In adults, responders had less miR-21 expression compared to PNRs and SNRs (relative median of miR-21 expression in folds [IQR]: 3.45[3.36 - 4.2], 5.05 [3.61 - 6.88], and 7.58 [6.21 - 8.2] in responders, PNRs, and SNRs respectively, p=0.04 and p=<0.01). In children, however, responders had an increased miR-21 expression compared to PNRs and SNRs (relative median of miR-21 expression in folds [IQR]: 19.94[15.88–24.59], 9.79[7.69– 14.44], and 10.58[5.66–12.91] in responders, PNRs, and SNRs respectively, p=0.03 and p=0.01). Expression of MiR-21 was found to be higher in children than adults (relative median of miR-21 expression in folds [IQR]: 4.65[3.45–7.21], and 13.6[8.37–19.05], respectively, p=<0.01). Conclusion Higher miR-21 expression indicates a higher response rate in children, whereas higher miR-21 expression could predict resistance to anti-TNF treatment in adults. MiR-21 expression could potentially be used as a predictive biomarker for anti-TNF treatment response in IBD patients with varying measures for children and adults.

Identification of Stably Expressed Reference microRNAs in Epithelial Ovarian Cancer.

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression and have been associated with the development of various cancers, including epithelial ovarian cancer (EOC). Accurate quantification of miRNA levels is important for determining their role in tumorigenesis and as biomarkers. Currently, U6 is widely used as a normalization control when investigating miRNAs in EOC; however, its variable expression across cancers has been reported. As only a few studies have been published to date on the identification of endogenous miRNA controls in EOC, our aim was to identify stable miRNAs based on global microarray profiling of 197 EOC patients and verify their stability in external datasets. We collected miRNA-microarray data from four datasets: the in-house "Pelvic Mass", and three public datasets with primary EOC patients: The Cancer Genome Atlas, GSE47841, and GSE73581. The expression stability of endogenous control candidates was evaluated by their coefficient of variation. All miRNA results in the used cohorts were produced by either Affymetrix or Agilent technologies, which show similar intra-platform patterns. Nonetheless, a clear difference in a cross-platform comparison was observed. We identified hsa-miR-92b-5p and hsa-miR-106b-3p as stable candidates shared between four datasets. Moreover, we investigated the stability performance of eight miRNAs that have been previously reported as stable endogenous controls in EOC and various performance was observed in four datasets. The selection of suitable endogenous miRNA normalization controls in EOC remains to be resolved, as variability in miRNA performance between platforms might have a crucial impact on the biological interpretation of data.

Oncomir MicroRNA-346 Is Upregulated in Colons of Patients With Primary Sclerosing Cholangitis

INTRODUCTION:Primary sclerosing cholangitis (PSC) is a cholestatic liver disorder that is frequently associated with ulcerative colitis (UC). Patients with PSC and UC (PSC-UC) have a higher risk of colorectal neoplasia compared with patients with UC. The oncogenic properties of microRNA-346 (miR-346) have been recently reported. We investigated the expression of miR-346 and its 2 target genes, the receptor of vitamin D (VDR), and the tumor necrosis factor-α (TNF-α), which are known to modulate carcinogenesis.METHODS:Ascending and sigmoid colon biopsies were obtained from patients with PSC, PSC and UC (PSC-UC), UC, and healthy controls (n = 10 in each group). Expressions of VDR, TNF-α, 18S RNA, p27Kip1, miR-346, and reference microRNA, miR-191, were evaluated by real-time PCR using human TaqMan Gene Expression and TaqMan MicroRNA Assays. Functional studies with miR-346 mimic and inhibitor were conducted in HepG2 and Caco-2 cells. The effect of ursodeoxycholic acid on miR-346 expression was examined in Caco-2 cells.RESULTS:An increased expression of miR-346 in the ascending colon of PSC-UC was observed (P < 0.001 vs all groups). In patients with UC, an exceptionally low colonic expression of miRNA-346 was accompanied by the extensive upregulation of VDR and TNF-α genes. A functional in vitro analysis demonstrated that inhibition of miR-346 resulted in the upregulation of VDR and TNF-α, whereas the induction of miR-346 activity suppressed VDR, TNF-α, and p27Kip1.DISCUSSION:The upregulation of miRNA-346 in the colon of patients with PSC may be responsible for the disturbance of VDR and TNF-α signaling pathway, which could result in an inadequate suppression of neoplasia.

Quantitative PCR Measurement of miR-371a-3p and miR-372-p Is Influenced by Hemolysis.

Cell-free microRNAs have been reported as biomarkers for several diseases. For testicular germ cell tumors (GCT), circulating microRNAs 371a-3p and 372-3p in serum and plasma have been proposed as biomarkers for diagnostic and disease monitoring purposes. The most widely used method for quantification of specific microRNAs in serum and plasma is reverse transcriptase real-time quantitative PCR (RT-qPCR) by the comparative Ct-method. In this method one or several reference genes or reference microRNAs are needed in order to normalize and calculate the relative microRNA levels across samples. One of the pitfalls in analysis of microRNAs from serum and plasma is the release of microRNAs from blood cells during hemolysis. This is an important issue because varying degrees of hemolysis are not uncommon in routine blood sampling. Thus, hemolysis must be taken into consideration when working with circulating microRNAs from blood. miR-93-5p, miR-30b-5p, and miR-20a-5p have been reported as reference microRNA in analysis of the miR-371a-373 cluster. We here show how these three microRNAs are influenced by hemolysis. We also propose a new reference microRNA, miR-191-5p, which is relatively stable in serum samples with mild hemolysis. In addition, we show how hemolysis can have effect on the reported microRNA levels in patient samples when these reference microRNAs are used in samples with varying levels of hemolysis.

Aberrant miRNA expression in glioma.

e13506 Background: Gliomas are the most common type of primary brain tumors, with a high level of recurrence and mortality. The purpose of the study was to determine the expression profile of micro-RNA targeting components of the Hedgehog, Notch, Wnt, EGFR, TGFβ, HIF1α signaling pathways according to MirTarBase, miRDB, TargetScan. Methods: The study included 30 patients (15 women and 15 men) aged 27 to 76 years with histologically verified glial brain tumors. The RT2-qPCR method in operational biopsy specimens determined the relative expression of 12 micro-RNAs: hsa-miR-17-3p, hsa-miR-20a-3p, hsa-miR-326, hsa-miR-330-3p, hsa-miR- 107, hsa-miR-143-3p, hsa-let-7a-5p, hsa-miR-146a-5p, hsa-miR-29a-3p, hsa-miR-92a-1-5p, hsa-miR-26b-3p, hsa-miR-96-5p. Hsa-miR-7-5p and hsa-miR-126-3p were used as reference micro-RNA. Results: A statistically significant increase in the expression of hsa-miR-143-3p, hsa-miR-146a-5p and hsa-miR-92a-1-5p by 2, 2.2 and 2.9 times, respectively, was found, as well as a decrease in the expression of hsa-miR-330- 3p by 4.1 times in tumor tissue of the brain relative to normal tissue (p &lt; 0.05). Reduced expression of micro-RNA hsa-miR-330-3p may increase the activity of the VEGFA gene, which leads to intensive vascularization of the tumor. In addition, hsa-miR-330-3p is a validated negative regulator of the E2F1 gene known as a regulator of the cell cycle and tumor suppressor proteins. The TRAF6 gene is the direct validated target of hsa-miR-146a-5p, and its overexpression is associated with the patient's chemoresistance to temozolomide. Increased hsa-miR-143-3p micro-RNA expression can reduce the activity of the EGLN1 gene that also mediates the adaptation of tumor cells to hypoxic conditions. Hsa-miR-92a-1-5p micro-RNA is a negative regulator of PTEN gene expression. Conclusions: A significant decrease in hsa-miR-330-3p expression and an increase in hsa-miR-146a-5p, hsa-miR-143-3p, and hsa-miR-92a-1-5p, which was found in gliomas, can potentially be used to develop prognostic markers and therapeutic targets for targeted therapy.

Identification of suitable reference microRNA for qPCR analysis in pediatric inflammatory bowel disease.

Pediatric inflammatory bowel disease (IBD) accounts for 10-15% of IBD and is associated with considerable morbidity for patients. Dysregulated microRNAs (miRNA, miR), small noncoding RNA molecules that modulate gene expression, have been the target of research in IBD diagnosis, surveillance, and therapy. Proper selection of reference genes, which are a prerequisite for accurate measurement of miRNA expression, is currently lacking. We hypothesize that appropriate normalization requires unique reference genes for different tissue and disease types. Through the study of 28 pediatric intestinal samples, we sought to create a protocol for selection of suitable endogenous reference genes. Candidate reference genes (miR-16, 193a, 27a, 103a, 191) were analyzed by RT-quantitative (q)PCR. Criteria used for designation of suitable reference genes were as follows: 1) ubiquitous: present in all tissue samples with quantification cycle value 15-35; 2) uniform expression: no differential expression between control and disease samples (P > 0.05); 3) stability: stability value <0.5 by NormFinder. Our results suggest the use of miR-27a/191 for Crohn's disease small bowel, none of the five candidate genes for Crohn's disease colon, and miR-16/27a for ulcerative colitis. Additionally, target miR-874 had differential expression when normalized with different reference genes. Our results demonstrate that reference gene choice for qPCR analysis has a significant effect on study results and that proper data normalization is imperative.

Extraction of RNA from formalin-fixed, paraffin-embedded equine placenta.

Archived formalin-fixed, paraffin-embedded (FFPE) samples represent a valuable resource for the determination of gene expression for physio/pathological conditions. In the present study, we validated a protocol for the extraction of RNA from FFPE samples collected from healthy and diseased equine placenta. The quality and quantity of the extracted RNA from the FFPE and matching RNAlater™-preserved samples and expression levels of common housekeeping genes and reference microRNAs were evaluated. Precision of the expression data was evaluated by comparing relative expression of CYP19A1 and HSD3B1 in FFPE and RNAlater™ samples. The median RNA concentration recovered from FFPE samples was 316.8ng/mm3 of tissue (ranging between 61.6 and 917.4ng/mm3 ), average RNA integrity number was 2.3±0.9 (mean±standard deviation), and 84% of samples had RNA fragments longer than 200 nucleotides (DV200 ). RNA concentrations and CT values for GAPDH, ACTB, miR-8908a and miR-369 in FFPE samples were significantly correlated (r=-0.8, -0.7, -0.4 and -0.4, respectively; p<0.001). Expression pattern of normalized CYP19A1 and HSD3B1 in paired FFPE and RNAlater™ samples was significantly correlated (r=0.97 for CYP19A1 and HSD3B1; p<0.001). This study demonstrates that RNA can be extracted from FFPE equine placental tissue and used for downstream transcriptomic analysis. Similar RNA expression patterns were obtained using RNAlater™ and FFPE tissue samples.

Reference MicroRNAs for RT-qPCR Assays in Cervical Cancer Patients and Their Application to Studies of HPV16 and Hypoxia Biomarkers

MicroRNA (miRNA) expressions in tumor biopsies have shown potential as biomarkers in cervical cancer, but suitable reference RNAs for normalization of reverse transcription quantitative polymerase chain reaction (RT-qPCR) assays in patient cohorts with different clinicopathological characteristics are not available. We aimed to identify the optimal reference miRNAs and apply these to investigate the potential of miR-9-5p as human papilloma virus (HPV) 16 biomarker and miR-210-3p as hypoxia biomarker in cervical cancer. Candidate reference miRNAs were preselected in sequencing data of 90 patients and ranked in a stability analysis by RefFinder. A selection of the most stable miRNAs was evaluated by geNorm and NormFinder analyses of RT-qPCR data of 29 patients. U6 small nuclear RNA (RNU6) was also included in the evaluation. MiR-9-5p and miR-210-3p expression was assessed by RT-qPCR in 45 and 65 patients, respectively. Nine candidates were preselected in the sequencing data after excluding those associated with clinical markers, HPV type, hypoxia status, suboptimal expression levels, and low stability. In RT-qPCR assays, the combination of miR-151-5p, miR-152-3p, and miR-423-3p was identified as the most stable normalization factor across clinical markers, HPV type, and hypoxia status. RNU6 showed poor stability. By applying the optimal reference miRNAs, higher miR-9-5p expression in HPV16- than HPV18-positive tumors and higher miR-210-3p expression in more hypoxic than less hypoxic tumors were found in accordance with the sequencing data. MiR-210-3p was associated with poor outcome by both sequencing and RT-qPCR assays. In conclusion, miR-151-5p, miR-152-3p, and miR-423-3p are suitable reference miRNAs in cervical cancer. MiR-9-5p and miR-210-3p are promising HPV16 and hypoxia biomarkers, respectively.

Normalizers for microRNA quantification in plasma of patients with vulvar intraepithelial neoplasia lesions and vulvar carcinoma.

The role of circulating microRNAs as a promising tool for diagnosing cancer and monitoring anticancer therapies has been widely studied in the past decades. To date, no suitable reference microRNAs for normalizing quantitative real-time polymerase chain reaction assays has been identified in vulvar intraepithelial neoplasia lesions and vulvar squamous cell carcinoma. The purpose of this study was to select appropriate references for gene expression studies in plasma of patients with these lesions. Expression levels of six microRNAs-hsa-miR-425-5p, hsa-miR-191-5p, hsa-miR-93-5p, hsa-miR-423-5p, hsa-miR-103a-3p, and hsa-miR-16-5p-were analyzed by quantitative reverse transcription polymerase chain reaction in plasma samples obtained from 17 patients with vulvar intraepithelial neoplasia lesion and 27 patients with vulvar squamous cell carcinoma. The expression stability of these candidate normalizers was assayed using geNorm algorithm. hsa-miR-93-5p was revealed as the most stably expressed reference in plasma samples of both vulvar intraepithelial neoplasia lesion and vulvar squamous cell carcinoma patients. The results pointed at hsa-miR-93-5p and hsa-miR-425-5p as microRNAs that retained the greatest robustness in plasma of vulvar intraepithelial neoplasia lesion and vulvar squamous cell carcinoma patients, respectively. Our work is the first report on reference microRNA selection for quantitative real-time polymerase chain reaction applications in vulvar intraepithelial neoplasia lesion and vulvar squamous cell carcinoma. The candidate microRNA stability values for the two types of lesions are provided and might serve for normalization of the future novel microRNA biomarkers in these rare entities.

MicroRNA Expression in Formalin-fixed Paraffin-embedded Cancer Tissue: Identifying Reference MicroRNAs and Variability.

BackgroundArchival formalin-fixed paraffin-embedded (FFPE) cancer tissue samples are a readily available resource for microRNA (miRNA) biomarker identification. No established standard for reference miRNAs in FFPE tissue exists. We sought to identify stable reference miRNAs for normalization of miRNA expression in FFPE tissue samples from patients with colorectal (CRC) and pancreatic (PC) cancer and to quantify the variability associated with sample age and fixation.MethodsHigh-throughput miRNA profiling results from 203 CRC and 256 PC FFPE samples as well as from 37 paired frozen/FFPE samples from nine other CRC tumors (methodological samples) were used. Candidate reference miRNAs were identified by their correlation with global mean expression. The stability of reference genes was analyzed according to published methods. The association between sample age and global mean miRNA expression was tested using linear regression. Variability was described using correlation coefficients and linear mixed effects models. Normalization effects were determined by changes in standard deviation and by hierarchical clustering.ResultsWe created lists of 20 miRNAs with the best correlation to global mean expression in each cancer type. Nine of these miRNAs were present in both lists, and miR-103a-3p was the most stable reference miRNA for both CRC and PC FFPE tissue. The optimal number of reference miRNAs was 4 in CRC and 10 in PC. Sample age had a significant effect on global miRNA expression in PC (50 % reduction over 20 years) but not in CRC. Formalin fixation for 2–6 days decreased miRNA expression 30–65 %. Normalization using global mean expression reduced variability for technical and biological replicates while normalization using the expression of the identified reference miRNAs reduced variability only for biological replicates. Normalization only had a minor impact on clustering results.ConclusionsWe identified suitable reference miRNAs for future miRNA expression experiments using CRC- and PC FFPE tissue samples. Formalin fixation decreased miRNA expression considerably, while the effect of increasing sample age was estimated to be negligible in a clinical setting.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-2030-2) contains supplementary material, which is available to authorized users.

Identification of reference genes for relative quantification of circulating microRNAs in bovine serum.

Circulating microRNAs in body fluids have been implicated as promising biomarkers for physiopathology disorders. Currently, the expression levels of circulating microRNAs are estimated by reverse transcription quantitative real-time polymerase chain reaction. Use of appropriate reference microRNAs for normalization is critical for accurate microRNA expression analysis. However, no study has systematically investigated reference genes for evaluating circulating microRNA expression in cattle. In this study, we describe the identification and characterization of appropriate reference microRNAs for use in the normalization of circulating microRNA levels in bovine serum. We evaluated the expression stability of ten candidate reference genes in bovine serum by using reverse transcription quantitative real-time polymerase chain reaction. Data were analyzed using geNorm, NormFinder, and BestKeeper statistical algorithms. The results consistently showed that a combination of miR-93 and miR-127 provided the most stably expressed reference. The suitability of these microRNAs was validated, and even when compared among different genders or breeds, the combination of miR-93 and miR-127 was ranked as the most stable microRNA reference. Therefore, we conclude that this combination is the optimal endogenous reference for reverse transcription quantitative real-time polymerase chain reaction-based detection of microRNAs in bovine serum. The data presented in this study are crucial to successful biomarker discovery and validation for the diagnosis of physiopathological conditions in cattle.

Identification of reference microRNAs for quantitative expression analysis in porcine peripheral blood mononuclear cells treated with polyinosinic-polycytidylic acid.

Peripheral blood mononuclear cells (PBMCs) are clinically important cells. Detection of microRNAs (miRNAs) expression in PBMCs can be useful for miRNA biomarker discovery for various diseases. Quantitative real-time PCR (qRT-PCR) has become an important method used for measuring miRNAs expression. However, the reliability of qRT-PCR data critically depends on proper selection of reference genes. Here, we performed qRT-PCR to quantify the expression levels of nine miRNAs (Ssc-miR-16, Hsa-miR-25, Ssc-miR-34a, Hsa-miR-93, Bta-miR-92b, Ssc-miR-103, Ssc-miR-106a, Ssc-miR-128 and Ssc-miR-107) and one small nuclear RNA (U6) in PBMCs treated with polyinosinic-polycytidylic acid [poly (I:C)] that widely used for simulating viral infection. We used the four statistical algorithms (GeNorm 3.5, NormFinder, BestKeeper and comparative ∆ Ct method) to evaluate gene expression stability and observed that Ssc-miR-34a was the best single reference gene and the pair of Ssc-miR-107 and Ssc-miR-103 was the best combination of reference miRNAs for porcine PBMCs treated with poly (I:C). Our study shows the first evidence of careful selection of reference miRNAs in porcine PBMCs and maybe helpful for discovering miRNA biomarkers for double-stranded RNA-induced disease.

Selection of endogenous reference microRNA genes for quantitative reverse transcription polymerase chain reaction studies of boar spermatozoa cryopreservation

It is important to select high-quality reference genes for the accurate interpretation of quantitative reverse transcription polymerase chain reaction data, in particular for certain miRNAs that may demonstrate unstable expression. Although several studies have attempted to validate reference miRNA genes in the porcine testis, spermatozoa, and other tissues, no validation studies have been carried out on cryopreserved boar spermatozoa. In this study, 15 commonly used reference miRNA genes (5S, let-7c-5p, ssc-miR-16-5p, ssc-miR-17-5p, ssc-miR-20a, ssc-miR-23a, ssc-miR-24-3p, ssc-miR-26a, ssc-miR-27a-3p, ssc-miR-92a, ssc-miR-103-3p, ssc-miR-106a, ssc-miR-107-3p, ssc-miR-186, and ssc-miR-221-3p) were selected to evaluate the expression stability of target miRNAs in boar spermatozoa under different experimental conditions and concentrations. The stability of the expression of these reference miRNAs across each sample was evaluated using geNorm, NormFinder, and BestKeeper software. The results showed that ssc-miR-186 (mean rank value = 5.00), ssc-miR-23a (5.33), and ssc-miR-27a (5.33) were the most suitable reference genes using three different statistical algorithms and comprehensive ranking. The identification of these reference miRNAs will allow for more accurate quantification of the changes in miRNA expression during cryopreservation of boar spermatozoa.

Identification of Urinary MicroRNAs That Are Discriminative of Acute Rejection in Kidney Transplantation.

RNA assessment in urine sediments from kidney transplant recipients may represent a non-invasive tool for detecting acute rejection.In a case-control study, we aimed to discover in an unbiased manner urinary microRNAs that best distinguish conditions of acute rejection. We first tested microRNA stability of artificially degraded RNA from isolated leukocytes. Then, expression of all known human microRNAs (Exiqon, PCR panel, n=742) was profiled in RNA from urinary sediment samples of 6 kidney transplant recipients with biopsy-supported acute rejection (80.0 ± 46.9 days posttransplant; 4 with T-cell mediated rejection, 2 with vascular rejection) and of 6 patients without rejection (84.0 ± 18.8 days posttransplant). For each patient, microRNA signals were standardized to the average signal of five reference microRNAs. We found that microRNA molecules remained stable, regardless of the extent of RNA degradation. Furthermore, microRNA expression could be reproducibly quantified in extremely low amounts of RNA (10 pg per reaction) with the help of locked nucleic acid (LNA)-enhanced PCR primers. In the case-control study, the level of 15 microRNAs significantly discriminated acute rejections from controls (Mann-Whitney rank test, P<0.05). MicroRNAs 451 and 25 represented the most promising discriminative analytes, since their expression levels were high in the sediments and were at least 13-fold increased (P≤0.017) during acute rejection compared to the control group. We identified microRNAs in the urinary sediment, of which the expression levels are associated with acute rejection. Predictive and diagnostic value of these levels for acute rejection will be verified in a larger patient cohort.

Selection of candidate reference genes for real-time PCR studies in lettuce under abiotic stresses.

The process of selection and validation of reference genes is the first step in studies of gene expression by real-time quantitative polymerase chain reaction (RT-qPCR). The genome of lettuce, the most popular leaf vegetable cultivated worldwide, has recently been sequenced; therefore, suitable reference genes for reliable results in RT-qPCR analyses are required. In the present study, 17 candidate reference genes were selected, and their expression stability in lettuce leaves under drought, salt, heavy metal, and UV-C irradiation conditions and under the application of abscisic acid (ABA) was evaluated using geNorm and NormFinder software. The candidate reference genes included protein-coding traditional and novel reference genes and microRNAs (miRNAs). The results indicate that the expression stability is dependent on the experimental conditions. The novel protein-coding reference genes were more suitable than the traditional reference genes under drought, UV-C irradiation, and heavy metal conditions and under the application of ABA. Only under salinity conditions were the traditional protein-coding reference genes more stable than the novel genes. In addition, the miRNAs, mainly MIR169, MIR171/170 and MIR172, were stably expressed under the abiotic stresses evaluated, representing a suitable alternative approach for gene expression data normalization. The expression of phenylalanine ammonia lyase (PAL) and 4-hydroxyphenylpyruvate dioxygenase (HPPD) was used to further confirm the validated protein-coding reference genes, and the expression of MIR172 and MIR398 was used to confirm the validated miRNA genes, showing that the use of an inappropriate reference gene induces erroneous results. This work is the first survey of the stability of reference genes in lettuce and provides guidelines to obtain more accurate RT-qPCR results in lettuce studies.

Abstract 172: Circulating Mirna Profiles Discriminate Stroke Severity Associated With Age and Sex

Background: Age and sex have significant effects on stroke outcomes, however, the precise mechanisms by which these factors affect stroke pathophysiology remains unclear. Small non-coding RNA (miRNA) found in circulation have been used successfully as biomarkers and mechanistic targets for chronic and acute diseases. The present study investigated the impact of age and sex on microRNA expression following ischemic stroke. Methods: Adult (6 mo) and middle aged (11-12 mo) female and male rats were subject to middle cerebral artery occlusion (MCAo) using Endothelin-1. Blood samples were drawn at 2d and 5d post stroke. All animals were terminated at 5d and the brains processed for infarct analysis by standard histological procedures. Total RNA isolated from serum was subject to QPCR amplification for serum microRNAs (168) and 7 reference microRNAs (Exiqon focus panels). Normalized miRNA values were analyzed by Genesifter program using a two-way ANOVA with Benjamini and Hochberg corrections for false discovery rates.. Results: Normalized infarct volume was significantly smaller in adult females (0.12+) as compared to middle-aged females (0.4; p&lt;0.05), young males (0.51 ) or middle aged males (0.51. p&lt;0.05). At 2d post stroke, 30 circulating miRNAs were differentially regulated and principal component analysis (PCA) confirmed that most of the variance was due to age. At 5d post stroke, 79 circulating miRNAs exhibited significantly different regulation, and PCA indicated that most of the variance was associated with sex. A small cohort (5) of miRNAs, miR-15a, -19b, -32, -136 and -199a-3p were found to be highly expressed in adult females compared to middle aged females, adult and middle-aged males. Predicted and experimentally validated gene targets for these 5 miRNAs analyzed for Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways revealed that the top 10 KEGG pathways (high p values, large gene numbers) were related to growth factor signaling, cell structure and MAPK signaling. Conclusion: Overall, the pattern of circulating miRNA expression suggests an early influence of age in stroke pathology, with a later emergence of sex as a factor for stroke severity. Furthermore, a small cohort of miRNAs were found to discriminate severe and mild stroke infarction.

38-OR

RNA assessment in urine sediments from kidney transplant recipients may represent a non-invasive tool for detecting acute rejection. MicroRNAs are small, non-coding RNA molecules that negatively regulate mRNA expression, and which have gained interest for their role in rejection of kidney transplants. In a case-control study, we aimed to discover in an unbiased manner urinary microRNAs that best distinguish conditions of acute rejection. We first tested microRNA stability of artificially degraded RNA from isolated leukocytes. Then, expression of all known human microRNAs (Exiqon, PCR panel, n = 742) was profiled in RNA from urinary sediment samples of 6 kidney transplant recipients with biopsy-supported acute rejection (80.0 ± 46.9 days posttransplant; 4 with T-cell mediated rejection, 2 with vascular rejection) and of 6 patients without rejection (84.0 ± 18.8 days posttransplant). For each patient, microRNA signals were standardized to the average signal of five reference microRNAs. We found that microRNA molecules remained stable, regardless of the extent of RNA degradation. Furthermore, microRNA expression could be reproducibly quantified in extremely low amounts of RNA (10 pg per reaction) with the help of locked nucleic acid (LNA)-enhanced PCR primers. In the case-control study, the level of 15 microRNAs significantly discriminated acute rejections from controls (Mann-Whitney rank test, P < 0.05). MicroRNAs 451 and 25 represented the most promising discriminative analytes, since their expression levels were high in the sediments and were at least 13-fold increased (P ⩽ 0.017) during acute rejection compared to the control group. We identified microRNAs in the urinary sediment, of which the expression levels are associated with acute rejection. Predictive and diagnostic value of these levels for acute rejection will be verified in a larger patient cohort.