The Orthology Clause in the Next Generation Sequencing Era: Novel Reference Genes Identified by RNA-seq in Humans Improve Normalization of Neonatal Equine Ovary RT-qPCR Data

Involvement of somatotrophic hormones in the postpartum regulation of ovarian activity in mares

Mares resume ovarian activity rapidly after foaling. Besides follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the pituitary synthesizes prolactin and growth hormone which stimulate insulin-like growth factor (IGF) synthesis in the liver. We tested the hypothesis that follicular growth is initiated already antepartum, mares with early and delayed ovulation differ in IGF-1 release and that there is an additional IGF-1 synthesis in the placenta. Plasma concentrations of LH, FSH, IGF-1, IGF-2, activin and prolactin. IGF-1, IGF-2, prolactin and their receptors in placental tissues were analyzed at the mRNA and protein level. Follicular growth was determined from 15 days before to 15 days after foaling in 14 pregnancies. Mares ovulating within 15 days postpartum formed group OV (n=5) and mares not ovulating within 15 days group NOV (n=9). Before foaling, follicles with a diameter >1 cm were present in all mares and their number increased over time (p<0.05). Follicle growth after foaling was more pronounced in OV mares (day p<0.001, group p<0.05, day x group p<0.05) in parallel to an increase in LH concentration (p<0.001, day x group p<0.001) while FSH increased (p<0.001) similarly in both groups. Plasma concentrations of IGF-1 and prolactin peaked one day after foaling (p<0.001). The IGF-1 mRNA abundance was higher in the allantochorion but lower in the amnion of OV versus NOV mares (group p=0.01, localization x group p<0.01). The IGF-1 receptor mRNA was most abundant in the allantochorion (p<0.001) and IGF-1 protein was expressed in placental tissue without differences between groups. In conclusion, follicular growth in mares is initiated before foaling and placental IGF-1 may enhance resumption of ovulatory cycles.

Endocrine changes induced by GnRH immunisation and subsequent early re-stimulation of testicular function with a GnRH agonist in stallions

CONTEXT

Resumption of testicular function after gonadotrophin-releasing hormone (GnRH) immunisation varies among individual animals and some stallions regain fertility only after a prolonged time.

AIMS

This study evaluated endocrine effects of GnRH immunisation and early subsequent re-stimulation with a GnRH agonist. We hypothesised that GnRH agonist treatment advances resumption of normal endocrine function in GnRH-vaccinated stallions.

METHODS

Shetland stallions were assigned to an experimental and a control group (n =6 each). Experimental stallions were GnRH-immunised twice, 4weeks apart. Each experimental stallion was hemicastrated together with an age-matched control animal when testosterone concentration decreased below 0.3ng/mL. Three weeks later, daily treatment with the GnRH agonist buserelin was initiated (4μg/day for 4weeks followed by 8μg/day). The remaining testicle was removed when testosterone concentration exceeded 0.5ng/mL in vaccinated stallions. Blood was collected for LH, FSH, oestradiol and anti-müllerian hormone (AMH) analyses, and testicular and epididymal tissue were conserved for real-time qPCR and histology.

KEY RESULTS

GnRH vaccination reduced blood concentrations of LH and FSH, with a structural deterioration of testicular tissue and disruption of spermatogenesis. Daily buserelin treatment for approximately 60days partially restored gonadotropin secretion and induced a recovery of the functional organisation of the testicular tissue with effective spermatogenesis.

CONCLUSIONS

Endocrine testicular function can be restored in GnRH-vaccinated stallions by daily low-dose buserelin treatment. The buserelin treatment protocol may potentially be improved regarding the dose, interval and duration.

IMPLICATIONS

Daily buserelin treatment can be recommended for treatment of GnRH-vaccinated stallions with prolonged inhibition of testicular function.

A Strategy for the Selection of RT-qPCR Reference Genes Based on Publicly Available Transcriptomic Datasets

In the next-generation sequencing era, RT-qPCR is still widely employed to quantify levels of nucleic acids of interest due to its popularity, versatility, and limited costs. The measurement of transcriptional levels through RT-qPCR critically depends on reference genes used for normalization. Here, we devised a strategy to select appropriate reference genes for a specific clinical/experimental setting based on publicly available transcriptomic datasets and a pipeline for RT-qPCR assay design and validation. As a proof-of-principle, we applied this strategy to identify and validate reference genes for transcriptional studies of bone-marrow plasma cells from patients with AL amyloidosis. We performed a systematic review of published literature to compile a list of 163 candidate reference genes for RT-qPCR experiments employing human samples. Next, we interrogated the Gene Expression Omnibus to assess expression levels of these genes in published transcriptomic studies on bone-marrow plasma cells from patients with different plasma cell dyscrasias and identified the most stably expressed genes as candidate normalizing genes. Experimental validation on bone-marrow plasma cells showed the superiority of candidate reference genes identified through this strategy over commonly employed "housekeeping" genes. The strategy presented here may apply to other clinical and experimental settings for which publicly available transcriptomic datasets are available.

Transcriptome sequencing of archived lymphoma specimens is feasible and clinically relevant using exome capture technology

Formalin-fixed, paraffin-embedded (FFPE) specimens are an underutilized resource in medical research, particularly in the setting of transcriptome sequencing, as RNA from these samples is often degraded. We took advantage of an exome capture-based RNA-sequencing protocol to explore global gene expression in paired fresh-frozen (FF) and FFPE samples from 16 diffuse large B-cell lymphoma (DLBCL) patients. While FFPE samples generated fewer mapped reads compared to their FF counterparts, these reads captured the same library complexity and had a similar number of genes expressed on average. Furthermore, gene expression demonstrated a high correlation when comparing housekeeping genes only or across the entire transcriptome (r = 0.99 for both comparisons). Differences in gene expression were primarily seen in lowly expressed genes and genes with small or large coding sequences. Using cell-of-origin classifiers and clinically relevant gene expression signatures for DLBCL, FF, and FFPE samples from the same biopsy paired nearly perfectly in clustering analysis. This was further confirmed in a validation cohort of 50 FFPE DLBCL samples. In summary, we found the biological differences between tumors to be far greater than artifacts created as a result of degraded RNA. We conclude that exome capture transcriptome sequencing data from archival samples can confidently be used for cell-of-origin classification of DLBCL samples.

Epigenetic Changes in Equine Embryos after Short-Term Storage at Different Temperatures

Simple Summary

In embryos subjected to assisted reproductive techniques, epigenetic modifications may occur that can influence embryonic development and establishment of pregnancy. In horses, the storage temperature during transport of fresh embryos before transfer is a major concern. The aim of this study was, therefore, to determine the effects of two storage temperatures (5 °C and 20 °C) on equine embryos, collected at day seven after ovulation and stored for 24 h, concerning morphological development, expression of candidate genes associated with embryo growth and development, maternal recognition of pregnancy, methylation, apoptosis and gene-specific and global DNA methylation. Temperature during storage did not affect embryo size. There were no changes in pH and lipid peroxidation of the medium irrespective of group. mRNA expression and gene-specific DNA methylation of genes related to growth and development, maternal recognition of pregnancy, DNA methylation and apoptosis in stored embryos (5 °C and 20 °C) were altered when compared to fresh embryos. Therefore, our study demonstrates for the first time the gene-specific and global DNA methylation status of fresh equine embryos collected on days seven and eight after ovulation. Short-term storage, regardless of temperature, may compromise embryo development after transfer.

Abstract

In embryos subjected to assisted reproductive techniques, epigenetic modifications may occur that can influence embryonic development and the establishment of pregnancy. In horses, the storage temperature during transport of fresh embryos before transfer is a major concern. The aim of this study was, therefore, to determine the effects of two storage temperatures (5 °C and 20 °C) on equine embryos, collected at day seven after ovulation and stored for 24 h, on: (i) morphological development; (ii) expression of candidate genes associated with embryo growth and development, maternal recognition of pregnancy, methylation and apoptosis, and (iii) gene-specific and global DNA methylation. Embryos (n = 80) were collected on day seven or day eight after ovulation and assigned to four groups: day seven control (E7F, fresh); day seven, stored for 24 h at 5 °C (E5C); day seven, stored for 24 h at 20 °C (E20C) and day eight control (E8F, fresh 24h time control). The embryos and the storage medium (EquiHold, holding medium, Minitube, Tiefenbach, Germany) from all treatment groups were analyzed for (i) medium temperature, pH, and lipid peroxidation (malondialdehyde; MDA) and (ii) embryo morphology, mRNA expression and DNA methylation (immunohistochemistry and gene-specific DNA methylation). The size of embryos stored at 5 °C was larger (p < 0.01), whereas embryos stored at 20 °C were smaller (p < 0.05) after 24 h. There were no changes in pH and MDA accumulation irrespective of the group. The mRNA expression of specific genes related to growth and development (POU5F1, SOX2, NANOG), maternal recognition of pregnancy (CYP19A1, PTGES2), DNA methylation (DNMT1, DNMT3A, DNMT3B) and apoptosis (BAX) in the E5C and E20C were either up or downregulated (p < 0.05) when compared to controls (E7F and E8F). The immune expression of 5mC and 5hmC was similar among treatment groups. Percentage of methylation in the CpG islands was lower in the specific genes ESR1, NANOG and DNMT1 (p < 0.001) in E20C embryos when compared to E8F (advanced embryo stage). Therefore, our study demonstrates for the first time the gene-specific and global DNA methylation status of fresh equine embryos collected on days seven and eight after ovulation. Although our results suggest some beneficial effects of storage at 20 °C in comparison to 5 °C, the short-term storage, regardless of temperature, modified gene expression and methylation of genes involved in embryo development and may compromise embryo viability and development after transfer.

Transcriptomic analysis to identify genes associated with selective hippocampal vulnerability in Alzheimer's disease

Selective vulnerability of different brain regions is seen in many neurodegenerative disorders. The hippocampus and cortex are selectively vulnerable in Alzheimer's disease (AD), however the degree of involvement of the different brain regions differs among patients. We classified corticolimbic patterns of neurofibrillary tangles in postmortem tissue to capture extreme and representative phenotypes. We combined bulk RNA sequencing with digital pathology to examine hippocampal vulnerability in AD. We identified hippocampal gene expression changes associated with hippocampal vulnerability and used machine learning to identify genes that were associated with AD neuropathology, including SERPINA5, RYBP, SLC38A2, FEM1B, and PYDC1. Further histologic and biochemical analyses suggested SERPINA5 expression is associated with tau expression in the brain. Our study highlights the importance of embracing heterogeneity of the human brain in disease to identify disease-relevant gene expression.

Expression of enzymes involved in polyunsaturated fatty acid synthesis in the stallion testis and epididymis

The aim of the present study was to characterise key enzymes involved in polyunsaturated fatty acid (PUFA) synthesis in the testis and epididymis collected from 2-year-old healthy warmblood stallions (n=10). The mRNA expression of fatty acid synthase, the Δ9-, Δ6-, Δ5- and Δ4-desaturases and elongases 6, 5 and 2 (encoded by the fatty acid synthase (FASN), the stearoyl-CoA desaturase (SCD), the fatty acid desaturase 2 (FADS2), the fatty acid desaturase 1 (FADS1), the delta 4-desaturase, sphingolipid 1 (DEGS1), ELOVL fatty acid elongase 6(ELOVL6), ELOVL fatty acid elongase 5 (ELOVL5), ELOVL fatty acid elongase 2 (ELOVL2) genes respectively) was determined in equine testis and epididymis. All enzymes were present in testicular tissue and along the epididymis, but mRNA expression differed among localisations. The protein localisation of FADS1, FADS2 and ELOVL5 was determined by immunohistochemistry. In the testes, FADS1 was expressed in the germinal cells and ELOVL5 was expressed in germinal and Leydig cells; FADS2 was not detected. In the epididymis, FADS1 and FADS2 were expressed in the principal and basal cells, whereas ELOVL5 was found only in the principal cells of the caput. All three enzymes were present in epididymal vesicles secreted by an apocrine mechanism. These results suggest active PUFA metabolism during spermatogenesis and epididymal sperm maturation in stallions.

Unique Role of Caffeine Compared to Other Methylxanthines (Theobromine, Theophylline, Pentoxifylline, Propentofylline) in Regulation of AD Relevant Genes in Neuroblastoma SH-SY5Y Wild Type Cells

Methylxanthines are a group of substances derived from the purine base xanthine with a methyl group at the nitrogen on position 3 and different residues at the nitrogen on position 1 and 7. They are widely consumed in nutrition and used as pharmaceuticals. Here we investigate the transcriptional regulation of 83 genes linked to Alzheimer’s disease in the presence of five methylxanthines, including the most prominent naturally occurring methylxanthines—caffeine, theophylline and theobromine—and the synthetic methylxanthines pentoxifylline and propentofylline. Methylxanthine-regulated genes were found in pathways involved in processes including oxidative stress, lipid homeostasis, signal transduction, transcriptional regulation, as well as pathways involved in neuronal function. Interestingly, multivariate analysis revealed different or inverse effects on gene regulation for caffeine compared to the other methylxanthines, which was further substantiated by multiple comparison analysis, pointing out a distinct role for caffeine in gene regulation. Our results not only underline the beneficial effects of methylxanthines in the regulation of genes in neuroblastoma wild-type cells linked to neurodegenerative diseases in general, but also demonstrate that individual methylxanthines like caffeine mediate unique or inverse expression patterns. This suggests that the replacement of single methylxanthines by others could result in unexpected effects, which could not be anticipated by the comparison to other substances in this substance class.

Classification models using circulating neutrophil transcripts can detect unruptured intracranial aneurysm

Background

Intracranial aneurysms (IAs) are dangerous because of their potential to rupture. We previously found significant RNA expression differences in circulating neutrophils between patients with and without unruptured IAs and trained machine learning models to predict presence of IA using 40 neutrophil transcriptomes. Here, we aim to develop a predictive model for unruptured IA using neutrophil transcriptomes from a larger population and more robust machine learning methods.

Methods

Neutrophil RNA extracted from the blood of 134 patients (55 with IA, 79 IA-free controls) was subjected to next-generation RNA sequencing. In a randomly-selected training cohort (n = 94), the Least Absolute Shrinkage and Selection Operator (LASSO) selected transcripts, from which we constructed prediction models via 4 well-established supervised machine-learning algorithms (K-Nearest Neighbors, Random Forest, and Support Vector Machines with Gaussian and cubic kernels). We tested the models in the remaining samples (n = 40) and assessed model performance by receiver-operating-characteristic (ROC) curves. Real-time quantitative polymerase chain reaction (RT-qPCR) of 9 IA-associated genes was used to verify gene expression in a subset of 49 neutrophil RNA samples. We also examined the potential influence of demographics and comorbidities on model prediction.

Results

Feature selection using LASSO in the training cohort identified 37 IA-associated transcripts. Models trained using these transcripts had a maximum accuracy of 90% in the testing cohort. The testing performance across all methods had an average area under ROC curve (AUC) = 0.97, an improvement over our previous models. The Random Forest model performed best across both training and testing cohorts. RT-qPCR confirmed expression differences in 7 of 9 genes tested. Gene ontology and IPA network analyses performed on the 37 model genes reflected dysregulated inflammation, cell signaling, and apoptosis processes. In our data, demographics and comorbidities did not affect model performance.

Conclusions

We improved upon our previous IA prediction models based on circulating neutrophil transcriptomes by increasing sample size and by implementing LASSO and more robust machine learning methods. Future studies are needed to validate these models in larger cohorts and further investigate effect of covariates.

Differentially Expressed miRNAs Influence Metabolic Processes in Pituitary Oncocytoma

Spindle cell oncocytomas (SCO) of the pituitary are rare tumors accounting for 0.1–0.4% of all sellar tumors. Due to their rarity, little information is available regarding their pathogenesis. Our aim was to investigate miRNA expression profile of pituitary oncocytomas. Total RNA was extracted from 9 formalin-fixed paraffin embedded pituitary samples (4 primary, 3 recurrent oncocytomas and 2 normal tissues). Next-generation sequencing was performed for miRNA profiling. Transcriptome data of additional 6 samples’ were obtained from NBCI GEO database for gene expression reanalysis and tissue-specific target prediction. Bioinformatical analysis, in vitro miRNA mimics transfection, luciferase reporter system and AlamarBlue assay were applied to characterize miRNA’s function. 54 differentially expressed miRNAs and 485 genes in pituitary SCO vs. normal tissue and 8 miRNAs in recurrent vs. primary SCO were determined. Global miRNA downregulation and decreased level of DROSHA were detected in SCO samples vs. normal tissue. Transcriptome analysis revealed cell cycle alterations while miRNAs influenced mainly metabolic processes (tricarboxylic acid cycle-TCA, carbohydrate, lipid metabolism). Through miRNA-target interaction network the overexpressed Aconitase 2 potentially targeted by two downregulated miRNAs (miR-744-5p, miR-127-3p) was revealed. ACO2 and miR-744-5p interaction was validated by luciferase assay. MiR-127-3p and miR-744-5p significantly decreased cell proliferation in vitro. Our study firstly reported miRNA profile of pituitary oncocytoma. Our results suggest that tumor suppressor miRNAs may have an essential role in the pathogenesis of pituitary oncocytoma. Earlier reports showed downregulated TCA cycle in SCO which is extended by our results adding the role of miR-744-5p targeting ACO2.

Analysis of mRNA abundance for histone variants, histone- and DNA-modifiers in bovine in vivo and in vitro oocytes and embryos

Transcript abundance of histone variants, modifiers of histone and DNA in bovine in vivo oocytes and embryos were measured as mean transcripts per million (TPM). Six of 14 annotated histone variants, 8 of 52 histone methyl-transferases, 5 of 29 histone de-methylases, 5 of 20 acetyl-transferases, 5 of 19 de-acetylases, 1 of 4 DNA methyl-transferases and 0 of 3 DNA de-methylases were abundant (TPM >50) in at least one stage studied. Overall, oocytes and embryos contained more varieties of mRNAs for histone modification than for DNA. Three expression patterns were identified for histone modifiers: (1) transcription before embryonic genome activation (EGA) and down-regulated thereafter such as PRMT1; (2) low in oocytes but transiently increased for EGA such as EZH2; (3) high in oocytes but decreased by EGA such as SETD3. These expression patterns were altered by in vitro culture. Additionally, the presence of mRNAs for the TET enzymes throughout pre-implantation development suggests persistent de-methylation. Together, although DNA methylation changes are well-recognized, the first and second orders of significance in epigenetic changes by in vivo embryos may be histone variant replacements and modifications of histones.

Differences in intestinal size, structure, and function contributing to feed efficiency in broiler chickens reared at geographically distant locations

The contribution of the intestinal tract to differences in residual feed intake (RFI) has been inconclusively studied in chickens so far. It is also not clear if RFI-related differences in intestinal function are similar in chickens raised in different environments. The objective was to investigate differences in nutrient retention, visceral organ size, intestinal morphology, jejunal permeability and expression of genes related to barrier function, and innate immune response in chickens of diverging RFI raised at 2 locations (L1: Austria; L2: UK). The experimental protocol was similar, and the same dietary formulation was fed at the 2 locations. Individual BW and feed intake (FI) of chickens (Cobb 500FF) were recorded from d 7 of life. At 5 wk of life, chickens (L1, n = 157; L2 = 192) were ranked according to their RFI, and low, medium, and high RFI chickens were selected (n = 9/RFI group, sex, and location). RFI values were similar between locations within the same RFI group and increased by 446 and 464 g from low to high RFI in females and males, respectively. Location, but not RFI rank, affected growth, nutrient retention, size of the intestine, and jejunal disaccharidase activity. Chickens from L2 had lower total body weight gain and mucosal enzyme activity but higher nutrient retention and longer intestines than chickens at L1. Parameters determined only at L1 showed increased crypt depth in the duodenum and jejunum and enhanced paracellular permeability in low vs. high RFI females. Jejunal expression of IL1B was lower in low vs. high RFI females at L2, whereas that of TLR4 at L1 and MCT1 at both locations was higher in low vs. high RFI males. Correlation analysis between intestinal parameters and feed efficiency metrics indicated that feed conversion ratio was more correlated to intestinal size and function than was RFI. In conclusion, the rearing environment greatly affected intestinal size and function, thereby contributing to the variation in chicken RFI observed across locations.

Cytokine-induced interleukin-1 receptor antagonist protein expression in genetically engineered equine mesenchymal stem cells for osteoarthritis treatment

BACKGROUND

A combination of tissue engineering methods employing mesenchymal stem cells (MSCs) together with gene transfer takes advantage of innovative strategies and highlights a new approach for targeting osteoarthritis (OA) and other cartilage defects. Furthermore, the development of systems allowing tunable transgene expression as regulated by natural disease-induced substances is highly desirable.

METHODS

Bone marrow-derived equine MSCs were transduced with a lentiviral vector expressing interleukin-1 receptor antagonist (IL-1Ra) gene under the control of an inducible nuclear factor-kappa B-responsive promoter and IL-1Ra production upon pro-inflammatory cytokine stimulation [tumor necrosis factor (TNF)α, interleukin (IL)-1β] was analysed. To assess the biological activity of the IL-1Ra protein that was produced and the therapeutic effect of IL-1Ra-expressing MSCs (MSC/IL-1Ra), cytokine-based two- and three-dimensional in vitro models of osteoarthritis using equine chondrocytes were established and quantitative real-time polymerase chain reaction (PCR) analysis was used to measure the gene expression of aggrecan, collagen IIA1, interleukin-1β, interleukin-6, interleukin-8, matrix metalloproteinase-1 and matrix metalloproteinase-13.

RESULTS

A dose-dependent increase in IL-1Ra expression was found in MSC/IL-1Ra cells upon TNFα administration, whereas stimulation using IL-1β did not lead to IL-1Ra production above the basal level observed in nonstimulated cells as a result of the existing feedback loop. Repeated cycles of induction allowed on/off modulation of transgene expression. In vitro analyses revealed that IL-1Ra protein present in the conditioned medium from MSC/IL-1Ra cells blocks OA onset in cytokine-treated equine chondrocytes and co-cultivation of MSC/IL-1Ra cells with osteoarthritic spheroids alleviates the severity of the osteoarthritic changes.

CONCLUSIONS

Thus, pro-inflammatory cytokine induced IL-1Ra protein expression from genetically modified MSCs might represent a promising strategy for osteoarthritis treatment.

Multi-omic network-based interrogation of rat liver metabolism following gastric bypass surgery featuring SWATH proteomics

Morbidly obese patients often elect for Roux-en-Y gastric bypass (RYGB), a form of bariatric surgery that triggers a remarkable 30% reduction in excess body weight and reversal of insulin resistance for those who are type II diabetic. A more complete understanding of the underlying molecular mechanisms that drive the complex metabolic reprogramming post-RYGB could lead to innovative non-invasive therapeutics that mimic the beneficial effects of the surgery, namely weight loss, achievement of glycemic control, or reversal of non-alcoholic steatohepatitis (NASH). To facilitate these discoveries, we hereby demonstrate the first multi-omic interrogation of a rodent RYGB model to reveal tissue-specific pathway modules implicated in the control of body weight regulation and energy homeostasis. In this study, we focus on and evaluate liver metabolism three months following RYGB in rats using both SWATH proteomics, a burgeoning label free approach using high resolution mass spectrometry to quantify protein levels in biological samples, as well as MRM metabolomics. The SWATH analysis enabled the quantification of 1378 proteins in liver tissue extracts, of which we report the significant down-regulation of Thrsp and Acot13 in RYGB as putative targets of lipid metabolism for weight loss. Furthermore, we develop a computational graph-based metabolic network module detection algorithm for the discovery of non-canonical pathways, or sub-networks, enriched with significantly elevated or depleted metabolites and proteins in RYGB-treated rat livers. The analysis revealed a network connection between the depleted protein Baat and the depleted metabolite taurine, corroborating the clinical observation that taurine-conjugated bile acid levels are perturbed post-RYGB.

Glucocorticoid metabolism in equine follicles and oocytes

The objective of this study was to determine whether (1) systemic and intrafollicular cortisol concentrations in horses are directly related and (2) supraphysiological levels of glucocorticoids affect in vitro maturation (IVM) rates of oocytes. Specifically, we studied the (1) changes in the intrafollicular cortisol and progesterone in context with granulosa cell gene expression during maturation of equine follicles (from 5-9 mm, 10-14 mm, 15-19 mm, 20-24 mm, and ≥25 mm in diameter) and (2) effects of cortisol supplementation on IVM rates and gene expression of equine cumulus-oocyte complexes (COCs). For these purposes, follicular fluid, granulosa cells, and COCs were collected from 12 mares (mean age 8.6 ± 0.5 yr) by transvaginal aspiration. Cortisol and progesterone concentrations in follicular fluid from follicles ≥25 mm were greater (P < 0.05) than in all other follicle classes and were positively correlated (r = 0.8; P < 0.001). Plasma concentrations of cortisol and progesterone did not differ before and after follicle aspiration (P > 0.05). In granulosa cells, gene expression of NR3C1, HSD11B1, HSD11B2, and CYP21A2 did not differ (P > 0.05) among different follicle classes. Maturation rates were similar (P > 0.05) among groups, regardless of the cortisol concentration in the IVM medium. In cumulus cells, messenger RNA expression of genes involved in glucocorticoid mechanism and apoptosis was either increased (NR3C1 and BCL2) or decreased (HSD11B2) by treatment (P < 0.01). In oocytes, gene expression of maturation markers (BMP15 and GDF9) was affected (P < 0.001) by cortisol treatment. This study demonstrates the involvement of glucocorticoids in follicle and oocyte maturation and cortisol modulation by HSD11B2 in equine COCs. Our data provide further information for understanding the normal ovarian endocrine physiology which might in turn also help improve equine assisted reproduction techniques.