scholarly journals Effect of preovulatory follicle size on cumulus cell and follicular wall transcript abundance in beef cows

2017 ◽  
Author(s):  
◽  
Jenna Marie Monnig

Gonadotropin releasing hormone (GnRH)-induced ovulation of small dominant follicles decreased pregnancy rates and increased late embryonic/fetal mortality in postpartum beef cows, which could be caused by inadequate oocyte competence and(or) maternal environment. Previous studies revealed that dominant follicle size at GnRHinduced ovulation in beef cows may affect oocyte competence, as higher fertilization rates and higher embryo quality were achieved as dominant follicle diameter at insemination increased. In addition, higher pregnancy rates and increased concentrations of circulating preovulatory estradiol and postovulatory progesterone were observed in recipient cows induced to ovulate large compared to small dominant follicles, which may affect the establishment of pregnancy. The objectives of the current study were to determine the effects of preovulatory follicle size and physiological status on the cumulus cell transcriptome (Experiment 1) and determine the effects of preovulatory follicle size and steroidogenic capacity (i.e. concentrations of circulating estradiol) on the dominant follicle wall transcriptome collected before the preovulatory gonadotropin surge (Experiment 2). In Experiment 1, ovulation was synchronized in suckled beef cows by administering an injection of GnRH on d-9, prostaglandin F2a (PG) on d-2, and a second injection of GnRH on d0. The dominant follicle was trans-vaginally aspirated on d1 and cumulus-oocyte complexes (COC) were collected. The cumulus cells were removed from the oocytes and assigned to one of the following follicle classifications based on follicle diameter and estrus expression: small (n=6; less than 11.7mm; no estrus expression), large (n=6; greater than 12.5 mm; no estrus expression), or spontaneous (n=5; 11.6-13.9 mm; estrus expression and endogenous gonadotropin surge). RNA was extracted from cumulus cells collected from pools of four oocytes and sequenced before being aligned to the Bos taurus genome (UMD3.1). When comparing the cumulus cell transcriptome of small versus large preovulatory follicles, 430 transcripts were more abundant at a false discovery rate (FDR) less than 0.10 in small follicles and 454 were more abundant in large follicles. The glycolytic pathway was enriched in the cumulus cells of large follicles compared to small follicles. In the small versus spontaneous preovulatory follicle comparison, 597 transcripts were more abundant in small follicles and 1012 transcripts were more abundant in spontaneous follicles. The steroid biosynthesis pathway (i.e. cholesterol synthesis) was enriched in the cumulus cells of spontaneous compared to small follicles. In the large versus spontaneous preovulatory follicle comparison, 541 transcripts were more abundant in cumulus cells from large follicles and 951 were more abundant in cumulus cells from spontaneous follicles. In summary, a greater abundance of transcripts encoding for members of the glycolytic pathway in large follicles and transcripts encoding for members of the steroid biosynthesis pathway in the cumulus cells of spontaneous compared to small follicles indicate that oocytes from small follicles may be less competent. Preovulatory follicle development was synchronized in Experiment 2 by administering GnRH on d-9 and PG on d-2 to non-lactating beef cows. The ovaries were harvested at slaughter 48 hr after PG (d0) and the dominant follicle collected. RNA was extracted from approximately half of the follicle wall and sequenced. Cows were divided into two classifications based on dominant follicle diameter at collection: small (n=4; less than 11.5 mm) and large (n=7; greater than 12.5 mm). Nine transcripts were more abundant in small follicles, and two transcripts were more abundant in large follicles. No significant pathways were found. The same 11 follicle walls were also divided into two classifications based on concentration of serum estradiol at 48 hr after PG: low (n=6; less than 4.0 pg/ml) and high (n=5; greater than or equal to 4.0 pg/ml). In the low estradiol classification, 281 transcripts were more abundant in the follicle wall and 40 were more abundant in the follicle wall of the high estradiol classification. No significant pathways were found. Transcripts were analyzed with PANTHER to find significant gene ontology (GO) terms. Differentially abundant transcripts in low estradiol follicles were more highly associated with mitosis, chromosome segregation, and regulation of biological processes. In summary, a small number of transcripts were differentially abundant in the follicle wall of small versus large dominant follicles prior to the preovulatory gonadotropin surge and no specific pathways were identified that might provide insight into how the physiological maturity of a dominant follicle can affect pregnancy rate. Comparisons made between follicle walls from follicles with low or high serum estradiol found a larger number of transcripts were more highly abundant in the low estradiol follicles, possibly indicating that a higher level of transcription is taking place in the low estradiol follicles, and therefore are less mature.

2005 ◽  
Vol 17 (2) ◽  
pp. 156 ◽  
Author(s):  
M. Colazo ◽  
M. Rutledge ◽  
J. Small ◽  
J. Kastelic ◽  
L. Siqueira ◽  
...  

The objectives were to investigate the effects of pretreatment with a used CIDR on follicle size and ovulation rate in cows after an injection of GnRH, and treatment with eCG at the time of PGF on preovulatory follicle size and fertility in cows subjected to a Cosynch protocol. Lactating crossbred beef cows (n = 292), 2 to 12 years of age were allocated to two groups to receive either a used CIDR (Bioniche Animal Health; Belleville, Ontario, Canada) for 15 days or no treatment (Control). At CIDR removal (Day 0), all cows received 100 μg of GnRH i.m. (Cystorelin, Merial Canada Inc., Victoriaville, Quebec, Canada). On Day 7, all cows received 500 μg of cloprostenol i.m. (PGF; Estrumate, Schering-Plough Animal Health, Pointe-Claire, Quebec, Canada) and were further allocated to receive either 400 IU of eCG i.m. (Pregnacol; Bioniche Animal Health) or no treatment (2 × 2 factorial design; n = 73 per group). On Day 9 (54 h after PGF), cows were given 100 μg of GnRH i.m., concurrent with timed AI (TAI). Transrectal ultrasonographic examinations were done on a subset of approximately 40 cows in each group on Days −15, 0, 7, and 9 to assess ovarian structures, and on all cows on Day 37 to confirm pregnancy. Data were analyzed by SAS CATMOD and ANOVA. Overall, 53% of cows had a CL present on Day −15 (P = 0.23). At first GnRH (Day 0), fewer CIDR-treated cows than Control cows had a CL (15.2 vs. 85.0%, respectively; P < 0.001), while mean (± SEM) diameters of the dominant follicle were larger in CIDR-treated cows (18.2 ± 0.4 vs. 13.8 ± 0.4 mm, respectively; P < 0.001). Moreover, the proportion of cows that ovulated following the first GnRH was higher (P < 0.001) in CIDR-treated (75.0%) than Control (48.7%) cows. Eight (10.0%) cows presynchronized with a CIDR did not ovulate and had a luteinized follicle (31.7 ± 1.9 mm) at the time of PGF. Although CIDR-treated cows had larger (P < 0.002) dominant follicles than Control cows on Day 9 (16.6 ± 0.3 vs. 15.2 ± 0.3 mm), presynchronization did not affect fertility (53.4 vs. 54.1%, respectively). However, diameter of the dominant follicle at TAI in cows that became pregnant was smaller in CIDR-treated vs. Control cows (15.3 ± 0.3 vs. 16.6 ± 0.3; P < 0.005). Treatment with eCG on Day 7 did not affect (P = 0.17) the diameter of the dominant follicle at TAI, but tended (P = 0.06) to increase pregnancy rate (58.9 vs. 48.6%). Furthermore, pregnancy rate tended to be higher (P = 0.08) in Control cows given eCG (47/73, 64.4%) than in the Control- (32/73, 43.8%), CIDR- (39/73, 53.4%) or CIDR/eCG- (39/73, 53.4%) treated cows. In addition, pregnancy rate was affected by parity; 2-yr-old cows had a lower (P < 0.04) pregnancy rate than older cows (42.9, 58.7, and 58.2% for 2, 3–4, and >5 years, respectively). Treatment with eCG increased pregnancy rate by 33% (P < 0.03) in 2-yr-old Control cows. In summary, presynchronization with a used CIDR prior to a Cosynch protocol increased the proportion of cows responding to the first GnRH. Although CIDR-treated cows had a smaller dominant follicle at TAI, pregnancy rate was not affected. Treatment with eCG increased fertility in Control cows; eCG may be useful in GnRH-based protocols in lactating beef cows.


Genes ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 893
Author(s):  
Sarah E. Moorey ◽  
Jenna M. Monnig ◽  
Michael F. Smith ◽  
M. Sofia Ortega ◽  
Jonathan A. Green ◽  
...  

Small dominant follicle diameter at induced ovulation, but not at spontaneous ovulation, decreased pregnancy rate, fertilization rate, and day seven embryo quality in beef cows. We hypothesized that the physiological status of the follicle at GnRH-induced ovulation has a direct effect on the transcriptome of the Cumulus-Oocyte complex, thereby affecting oocyte competence and subsequent embryo development. The objective of this study was to determine if the transcriptome of oocytes and associated cumulus cells (CC) differed among small (≤11.7 mm) and large follicles (≥12.7 mm) exposed to a GnRH-induced gonadotropin surge and follicles (11.7–14.0 mm) exposed to an endogenous gonadotropin surge (spontaneous follicles). RNA sequencing data, from pools of four oocytes or their corresponding CC, revealed 69, 94, and 83 differentially expressed gene transcripts (DEG) among oocyte pools from small versus large, small versus spontaneous, and large versus spontaneous follicle classifications, respectively. An additional 128, 98, and 80 DEG were identified among small versus large, small versus spontaneous, and large versus spontaneous follicle CC pools, respectively. The biological pathway “oxidative phosphorylation” was significantly enriched with DEG from small versus spontaneous follicle oocyte pools (FDR < 0.01); whereas the glycolytic pathway was significantly enriched with DEG from CC pools obtained from large versus small follicles (FDR < 0.01). These findings collectively suggest that altered carbohydrate metabolism within the Cumulus-Oocyte complex likely contributes to the decreased competency of oocytes from small pre-ovulatory follicles exposed to an exogenous GnRH-induced gonadotropin surge.


2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 423-423
Author(s):  
Alexandria E Crist ◽  
Jessica Cristina Lemos Motta ◽  
Cameron Hayden ◽  
Benjamin Duran ◽  
Martin Mussard

Abstract The 5-day CO-Synch is an extensively used TAI protocol; however, it requires multiple administrations of prostaglandin F2α (PGF). The objective of the present study was to evaluate the effect of increasing progesterone (P4) device insertion from 5 to 6 days during a TAI protocol on ovarian dynamics and fertility in beef cows. Suckled beef cows (n = 867) at six locations were randomly assigned to either a 5-day or 6-day CO-Synch. Cows received an intravaginal P4 device (CIDR, Zoetis) and 100 µg of gonadorelin acetate (GnRH, Parnell) on d-9 (6-day) or d-8 (5-day). On d-3 CIDR’s were removed, an estrus detection patch applied (Estrotect, Rockway Inc.) and either one (6-day) or two (5-day) doses of PGF (500 µg of cloprostenol sodium, Estroplan, Parnell) was administered. On d0 (72 h after CIDR removal) all cows received 100 µg of GnRH, estrus expression was evaluated, and AI was performed. Pregnancy was determined by ultrasonography 34 days after TAI. Ovarian dynamics were evaluated in a subset of animals (n = 20) between d-3 and d7 to determine preovulatory follicle size, time of ovulation and corpus luteum (CL) size. Data were analyzed using generalized linear mixed models (SAS 9.4). Cows in the 6-day group tended (P = 0.09) to have a larger maximum follicle diameter (16.2±0.4mm) than cows in the 5-day group (15.0±0.6mm). In addition, CL volume on d7 was greater (P = 0.01) in the 6-day (4302±495mm3) than 5-day (2406±455mm3) group. There were, however, no differences (P = 0.15) in the interval between CIDR removal and ovulation. Cows assigned to the 6-day group had greater (P &lt; 0.05) estrus expression [56.1% (215/385) vs 41.5% (161/388)] and pregnancy rate [54.6% (236/438) vs 47.4% (207/435)] than cows in the 5-day group. In conclusion, extension of the period of P4 device insertion in a prolonged proestrus protocol increases preovulatory follicle size, estrous expression, and fertility to TAI.


2022 ◽  
Author(s):  
Murat Can Demir ◽  
Cihan Kaçar ◽  
Umut Çağın Arı ◽  
Semra Kaya ◽  
Oğuz Merhan ◽  
...  

Abstract The present study aimed to determine the effects of progesterone-based gonadotropin-releasing hormone (GnRH), prostaglandin F2α (PGF2α), and equine chorionic gonadotropin (eCG) injections on progesterone profiles and pregnancy rates in cows with no estrus symptoms within 60 days after parturition. A total of 80 cows were included in the study. All animals had the progesterone-releasing device PRID®Delta placed intravaginally for nine days with an injection of GnRH. On the eighth day, PGF2α was injected, and PRID®Delta was removed from the vagina on day nine. Artificial insemination was carried out 60 hours after PRID®Delta removal. In half of the animals (n = 40), 600 IU of eCG was injected when PRID®Delta was removed on the ninth day before artificial insemination 60 hours later. Blood samples were taken from the tail vein on days 0 and 8 to determine progesterone levels. The pregnancy rate in the group that received eCG was 37.5%, while it was 27.5% in those that did not (P = 0.4). While the dominant follicle diameter was 15.5 mm in cows injected with eCG during timed artificial insemination, the follicle diameter was 12.4 mm in cows with no eCG injection (P <0.001). There were no differences in serum progesterone values in blood samples taken until the time of artificial insemination. However, progesterone values in the blood taken during artificial insemination were 0.94 ng/ml in the eCG- group and 0.72 ng/ml in the eCG+ group (P <0.05). As a result, it was determined that eCG injections, in addition to progesterone-based GnRH and PGF2α applications, increased the pregnancy rates in cows without symptoms of estrus. The dominant follicle diameter was larger in cows treated with eCG during artificial insemination; however, follicle size did not increase the pregnancy rate.


2010 ◽  
Vol 22 (1) ◽  
pp. 260
Author(s):  
M. Bertoldo ◽  
P. K. Holyoake ◽  
G. Evans ◽  
C. G. Grupen

Effective in vitro maturation (IVM) is essential for successful in vitro embryo production. The morphology of the cumulus investment before and after IVM may be a useful noninvasive indicator of oocyte quality. In pigs, oocyte developmental competence is reduced during the summer months. The aim of this study was to determine whether the morphology of cumulus-oocyte complexes (COC) before and after IVM are associated with oocyte quality, using COC collected from small and large follicles in summer and winter as models of poor and good oocyte quality. Ovaries were collected from sows slaughtered 4 days after weaning. The COC recovered from small (3-4 mm) and large (5-8 mm) antral follicles were morphologically graded and parthenogenetically activated following IVM during winter (n = 1419; 10 replicates) and summer (n = 2803; 10 replicates). Grade 1 and 2 COC had >2 layers of compact cumulus cells and a homogenous cytoplasm. Grade 3 COC were either partially or fully denuded, had a heterogeneous cytoplasm, or were vacuolated or dark in color. Grade 4 COC had expanded cumulus cells. Cumulus expansion was also assessed subsequent to IVM. The COC recorded as having a cumulus expansion index (CEI) of 1 had the poorest expansion with no detectable response to IVM, whereas those with a CEI of 4 had the greatest amount of expansion, including that of the corona radiata. Data were analyzed using a generalized linear mixed model in GenStat® (release 10, VSN International, Hemel Hempstead, UK). There was an effect of follicle size for Grade 1 COC, with COC from large follicles in both seasons yielding better quality COC (P < 0.05). The proportion of COC in Grade 2 was higher in small follicles during winter compared with large follicles, but there were no differences between follicle sizes during summer (P < 0.05). The proportion of COC with CEI 1 was highest in COC from small follicles during summer (P < 0.05). The proportion of COC from large follicles with CEI 2 was higher during summer compared with winter (P < 0.05). There were no seasonal or follicle size effects on COC with CEI 3 or 4 (P > 0.05). The proportion of oocytes that developed to blastocysts was greater in winter than in summer (39.06% ± 5.67 v. 22.27% ± 4.01; P < 0.05). Oocytes derived from large follicles had a greater ability to form blastocysts compared with those from small follicles (37.13% ± 5.65 v. 23.32% ± 4.56; P < 0.06). Morphological assessment of cumulus cells before and after IVM may be a useful tool to evaluate the effects of follicle size on oocyte developmental competence. However, the results of the present study indicate that cumulus cell morphology is not a good indicator of the effect of season on oocyte developmental competence.


Zygote ◽  
2017 ◽  
Vol 25 (3) ◽  
pp. 313-320 ◽  
Author(s):  
Swati Gupta ◽  
Sriti Pandey ◽  
Mehtab S. Parmar ◽  
Anjali Somal ◽  
Avishek Paul ◽  
...  

SummaryOocyte-secreted factors (OSFs) play an important role in the acquisition of oocyte developmental competence through bidirectional cross-talk between oocyte and cumulus cells via gap junctions. Thus, the present study was designed to investigate the effect of two OSFs, growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15), on the developmental competence of buffalo oocytes derived from two different follicle sizes. Cumulus–oocyte complexes (COCs) from large follicles (LF, >6 mm) or small follicles (SF, <6 mm) were collected and matured in vitro either in the presence of GDF9 or BMP15, or both, or with the denuded oocytes (DOs) as a source of native OSFs. Cleavage and blastocyst rates were significantly (P < 0.05) higher in LF-derived than SF-derived oocytes. Cleavage and blastocyst rates were significantly higher (P < 0.05) in the DOs and the combination groups compared with the control, GDF9 alone and BMP15 alone groups, both in LF-derived and SF-derived oocytes, although the cleavage and blastocyst rates did not differ significantly (P > 0.05) between DOs and combination groups. Relative mRNA analysis revealed significantly higher (P > 0.05) expression of the cumulus cell marker genes EGFR, HAS2, and CD44 in LF-derived than SF-derived oocyte; the expression of these markers was significantly higher (P > 0.05) in DOs and combination groups, irrespective of the follicle size. These results suggested that LF-derived oocytes have a higher developmental competence than SF-derived oocytes and that supplementation of GDF9 and BMP15 modulates the developmental competence of buffalo oocytes by increasing the relative abundance of cumulus-enabling factors and thereby increasing cleavage and the quality of blastocyst production.


2016 ◽  
Vol 28 (2) ◽  
pp. 203
Author(s):  
S. E. Dickinson ◽  
J. A. Green ◽  
T. W. Geary ◽  
K. G. Pohler ◽  
G. A. Bridges ◽  
...  

Inadequate oocyte competence is a potential explanation for reduced pregnancy rates and(or) embryonic/fetal mortality when small dominant follicles are induced to ovulate prematurely with gonadotropin releasing hormone (GnRH). Our hypothesis was that the physiological status of an ovulatory follicle has a direct effect on competence of the oocyte and resulting embryo. The objective was to determine if the transcriptome of oocytes differ depending on whether they are collected from small or large dominant follicles following a GnRH-induced gonadotropin surge. Suckled beef cows (n = 350) were pre-synchronized with a 5-day CIDR protocol. Following pre-synchronization, GnRH1 was administered on Day –9, prostaglandin F on Day –2, GnRH2 (to initiate the ovulatory process) on Day 0, and dominant follicles were transvaginally aspirated on Day 1 before follicular rupture. On Day 0, cows were divided into small (<11.7 mm; no oestrus expression), or large (>12.5 mm; no oestrus expression) groups based on dominant follicle diameter. Oocytes were individually collected after aspiration, and RNA was later extracted from pools of 4 oocytes (n = 6 oocyte pools from both small and large follicles) and sequenced on an Illumina HiSEqn 2000 (single reads, 100 bases; Illumina Inc., San Diego, CA, USA). The sequences were tiled against a ~23 500 member bovine transcript reference obtained from the National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/). Tiling to target transcripts required a minimum match of 50 bases with at least 96% identity. Tiling counts were displayed as reads per kilobase of transcript per million mapped reads (RPKM) values, which were obtained by correcting for the length of each target (in kb) and the number of total tiled reads (in millions). Differences between groups were defined by two-tailed t-test and gene lists were selected based on P-values <0.02. Numerous differences in transcript abundance were characterised between oocytes from small and large dominant follicles. Follistatin-like 5 expression was increased (P < 0.02) in oocytes collected from large dominant follicles compared with oocytes collected from small dominant follicles. Several genes were associated with the ubiquitin pathway (e.g. ubiquitin conjugating enzyme, ubiquitin like protein-7) and were up-regulated (P < 0.02) in oocytes from large versus small dominant follicles. In addition, 4 members of the zinc finger protein family were up-regulated (P < 0.02) and 4 members were down-regulated (P < 0.02) in oocytes from large compared with small dominant follicles. In summary, some of the genes that were highly differentially regulated in bovine oocytes between small and large dominant follicles included members of the zinc finger and ubiquitin pathways, which may reflect differences in transcriptional regulation and protein turnover, respectively, between oocytes collected from large and small follicles. Study was supported by AFRI Grant no. 2013–67015–21076 from the USDA National Institute of Food and Agriculture (Washington, DC).


Author(s):  
Harmeet Singh Sandhu ◽  
Shahbaz Singh Dhindsa ◽  
Harpreet Singh ◽  
Mrigank Honparkhe ◽  
Prahlad Singh

Background: Standard estrus synchronization regimens resulted in variable outcomes in buffaloes. The present study evaluated ovarian and fertility responses following presynchronization in Heatsynch protocol administered in postpartum buffaloes. Methods: In group-I (Presynch-Heatsynch group, n = 30), PGF2α was administered on days -14 and -2. Then, GnRH analogue, PGF2α (Cloprostenol) and Estradiol benzoate were administered on day 0, 7 and 8, respectively followed by fixed-time artificial insemination (FTAI) 48 hours later. In group-II (Heatsynch group, n = 30), rest protocol was same, except that first two PGF2α injections were not administered. Result: The progesterone concentrations differed (P less than 0.01) between the two groups on days -2, 0 and 7. Post-treatment, progesterone profiles were also higher in pregnant compared to non-pregnant buffaloes in both the groups except on day 10. CL diameter differed (P less than 0.01) between groups on days -2, 0 and 7. It was larger in pregnant than non-pregnant buffaloes on day 7 in both the groups. Dominant follicle diameter remained larger on days -2, 0 and 8 in group-I than -II. Buffaloes getting pregnant had a larger (P less than 0.01) dominant follicle size on the day of FTAI in group-I than of group-II. Ovulatory response of 93.33 and 90.00% was observed in group-I and II. The conception rate was higher (66.66 vs. 40.00%; P less than 0.05) in group-I than Group-II. Presynchronization improved reproductive efficiency in Heatsynch treatment and may aid for better fertility in buffaloes.


Zygote ◽  
2018 ◽  
Vol 26 (3) ◽  
pp. 224-231 ◽  
Author(s):  
Neda Taghizabet ◽  
Mohammad Ali Khalili ◽  
Fatemeh Anbari ◽  
Azam Agha-Rahimi ◽  
Stefania Annarita Nottola ◽  
...  

SummaryCumulus cells (CCs) play an important role in the regulation of female gamete development, meiotic maturation, oocyte–sperm interaction, capacitation and acrosome reaction. However, their role in maintaining oocyte competence after vitrification is unclear as controversial data on their protecting action against oocyte cryoinjuries are available. Here we described the effects of vitrification on the ultrastructure of human CCs collected from women undergoing assisted reproductive technologies (ARTs). In total, 50 patches of CCs, sampled from high-quality human cumulus–oocyte complexes, were randomly allocated into two groups after patient informed consent: 1, fresh CCs (controls, n = 25); 2, vitrified CCs (n = 25). Samples were then prepared and observed by transmission electron microscopy. In fresh CCs, in which small cell clusters were visible, cell membranes were joined by focal gap junctions. Microvilli were rare and short. Nuclei, mitochondria, smooth endoplasmic reticulum (SER), Golgi apparatus and lipid droplets appeared well preserved; vacuoles were scarce. After vitrification, we observed two populations of CCs: light CCs, with a smooth appearance and few short microvilli; and dark CCs, with numerous and long microvilli. In both, most of the organelles appeared similar to those of fresh CCs. Lipid droplets were denser and more numerous, with respect to fresh CCs. They were mainly located in the peri-nuclear and sub-plasmalemmal regions. Numerous packed electron-negative vacuoles were visible. The vitrification procedure did not cause alterations in the fine structure of major organelles, except for an increased amount of lipid droplets and vacuoles. This specific sensitivity of human CCs to vitrification should be considered during ARTs.


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