Ovulatory upregulation of angiotensin-converting enzyme 2, a receptor for SARS-CoV-2, in dominant follicles of the human ovary

New insights into the ovulatory process in the human ovary

BACKGROUND

Successful ovulation is essential for natural conception and fertility. Defects in the ovulatory process are associated with various conditions of infertility or subfertility in women. However, our understanding of the intra-ovarian biochemical mechanisms underlying this process in women has lagged compared to our understanding of animal models. This has been largely due to the limited availability of human ovarian samples that can be used to examine changes across the ovulatory period and delineate the underlying cellular/molecular mechanisms in women. Despite this challenge, steady progress has been made to improve our knowledge of the ovulatory process in women by: (i) collecting granulosa cells across the IVF interval, (ii) creating a novel approach to collecting follicular cells and tissues across the periovulatory period from normally cycling women, and (iii) developing unique in vitro models to examine the LH surge or hCG administration-induced ovulatory changes in gene expression, the regulatory mechanisms underlying the ovulatory changes, and the specific functions of the ovulatory factors.

OBJECTIVE AND RATIONALE

The objective of this review is to summarize findings generated using in vivo and in vitro models of human ovulation, with the goal of providing new insights into the mechanisms underlying the ovulatory process in women.

SEARCH METHODS

This review is based on the authors' own studies and a search of the relevant literature on human ovulation to date using PubMed search terms such as 'human ovulation EGF-signaling', 'human ovulation steroidogenesis', 'human ovulation transcription factor', 'human ovulation prostaglandin', 'human ovulation proteinase', 'human ovulation angiogenesis' 'human ovulation chemokine', 'human ovulatory disorder', 'human granulosa cell culture'. Our approach includes comparing the data from the authors' studies with the existing microarray or RNA-seq datasets generated using ovarian cells obtained throughout the ovulatory period from humans, monkeys, and mice.

OUTCOMES

Current findings from studies using in vivo and in vitro models demonstrate that the LH surge or hCG administration increases the expression of ovulatory mediators, including EGF-like factors, steroids, transcription factors, prostaglandins, proteolytic systems, and other autocrine and paracrine factors, similar to those observed in other animal models such as rodents, ruminants, and monkeys. However, the specific ovulatory factors induced, their expression pattern, and their regulatory mechanisms vary among different species. These species-specific differences stress the necessity of utilizing human samples to delineate the mechanisms underlying the ovulatory process in women.

WIDER IMPLICATIONS

The data from human ovulation in vivo and in vitro models have begun to fill the gaps in our understanding of the ovulatory process in women. Further efforts are needed to discover novel ovulatory factors. One approach to address these gaps is to improve existing in vitro models to more closely mimic in vivo ovulatory conditions in humans. This is critically important as the knowledge obtained from these human studies can be translated directly to aid in the diagnosis of ovulation-associated pathological conditions, for the development of more effective treatment to help women with anovulatory infertility or, conversely, to better manage ovulation for contraceptive purposes.

REGISTRATION NUMBER

N/A.

SARS-CoV-2 infection negatively impacts on the quality of embryos by delaying early embryonic development

BACKGROUND

The COVID-19 pandemic is an unprecedented health crisis that has affected in vitro fertilization practices globally. Previous studies have shown that SARS-CoV-2 impacts the quality of embryos by inducing an immunological response in infertile patients. In this study, the early embryonic development of SARS-CoV-2-infected infertile patients was investigated.

METHODS

Sixty-five SARS-CoV-2 infected infertile patients and 258 controls were involved in this study. The major outcome parameters for the cycle were analyzed, including the number of oocytes, maturation oocytes, available embryos per cycle, and embryo morpho kinetic characteristics.

RESULTS

From SARS-CoV-2 infection until oocyte retrieval, it took an average of 6.63 days. The results revealed that the number of oocytes and high-quality embryos on day 3 dramatically reduced in SARS-CoV-2-infected infertile patients. SARS-CoV-2 was detected in the follicular fluid of three infertile patients. SARS-CoV-2 infection had negatively impacted the number of oocytes in multivariate linear regression models. The early embryonic development in the SARS-CoV-2 infection group had a noticeable delay from the six-cell stage to blastocyst stage.

CONCLUSIONS

SARS-CoV-2 infection reduced the number of oocytes and high-quality embryos on day 3. It delays the early embryonic development from the six-cell stage to blastocyst stage and has a negative impact on the quality of embryos.

Effects of SARS-CoV-2 infection during ovarian stimulation on ART outcomes

RESEARCH QUESTION

Does severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection during ovarian stimulation affect assisted reproductive technology outcomes?

DESIGN

This retrospective cohort study conducted at the Reproductive Medicine Centre of The First Affiliated Hospital of Anhui Medical University aimed to assess the effects of acute SARS-CoV-2 infection during IVF on treatment outcomes and the reproductive system. The study included 151 treatment cycles involving couples with coronavirus disease 2019 (COVID-19) during ovarian stimulation, along with 224 cycles of non-infected couples as a control group. Clinical characteristics and laboratory parameters were analysed, including total gonadotrophin dosage, duration of ovarian stimulation, number of oocytes retrieved, fertilization method, fertilization rate, and number of blastocyst embryos available. Forty-six follicular fluid samples, 38 semen samples and 78 embryo culture medium samples from patients with COVID-19 were tested for SARS-CoV-2 RNA using reverse transcription polymerase chain reaction assay.

RESULTS

The treatment and control groups showed similar cycle characteristics, including fertilization method, total gonadotrophin dosage and duration of ovarian stimulation. The mean number of oocytes retrieved per cycle and rate of mature oocytes in intracytoplasmic sperm injection cycles were comparable. No significant difference was observed in the total number of blastocyst embryos available between the groups. Furthermore, no SARS-CoV-2 RNA was detected in any of the samples of patients with COVID-19.

CONCLUSIONS

In conclusion, acute SARS-CoV-2 infection during ovarian stimulation does not have a significant impact on IVF treatment outcomes. Additionally, no risk to the reproductive system was observed in patients infected with SARS-CoV-2. Therefore, individuals with asymptomatic or mild COVID-19 can safely continue IVF treatment. Future research is needed to investigate the long-term effects of COVID-19 on fertility and reproductive outcomes.

COVID-19-related premature ovarian insufficiency: case report and literature review

OBJECTIVE

The aim of this study is to present the case report of a 36-year-old woman developing premature ovarian insufficiency (POI) after COVID-19 and review the literature referring to the possible impact of SARS-CoV-2 infection on female reproduction.

METHODS

A 36-year-old nulligravida with normal menstrual cycles, non-smoker, with a normal body mass index and no pelvic surgery or oncological treatment in her medical history presented to the Infertility Center of the Institute of Mother and Child in Warsaw after a year of unsuccessful attempts to get pregnant. During diagnostic process she was affected by COVID-19 with a mild manifestation and thereafter she presented amenorrhea with intense hot flushes. Further diagnostic confirmed the diagnosis of POI.

RESULTS

There is a strong molecular basis for a possible effect of SARS-CoV-2 infection on the female reproductive system; however, the results of available research are conflicting. All of these aspects are discussed in detail.

CONCLUSIONS

SARS-CoV-2 infection may cause serious complications that cast a long shadow on a patient's future life and health. Further research is needed to assess the real impact of SARS-CoV-2 infection on female reproductive health, as well as potential preventive and therapeutic strategies for women affected with COVID-19.

Association of SARS-CoV-2 Infection During Controlled Ovarian Stimulation With Oocyte- and Embryo-Related Outcomes

Importance

SARS-CoV-2 infection has had significant effects on the health of people worldwide. Whether SARS-CoV-2 infection during controlled ovarian stimulation (COS) is associated with laboratory outcomes in assisted reproductive technology remains unclear.

Objective

To investigate the association between SARS-CoV-2 infection during COS with oocyte- and embryo-related outcomes.

Design, Setting, and Participants

A multicenter cohort study was conducted of couples undergoing assisted reproductive technology treatments in 7 reproductive centers in 4 provinces in China from October 1, 2022, to December 31, 2022. All couples received nucleic acid testing for SARS-CoV-2 during COS. The SARS-CoV-2-positive group included couples in which either partner was infected with SARS-CoV-2. The SARS-CoV-2-negative group comprised couples without infection.

Exposure

In the SARS-CoV-2-positive group, either partner was infected with SARS-CoV-2 during COS, defined as a positive test result for the SARS-CoV-2 antigen.

Main Outcomes and Measures

Primary outcomes were the available embryo and blastocyst and top-quality embryo and blastocyst rates. Secondary outcomes were the number of oocytes retrieved, the mature oocyte rate, normal fertilization (2 pronuclei observed on day 1 after insemination [2PN]), oocyte degeneration, 2PN cleavage, and blastocyst formation rates.

Results

A total of 585 heterosexual couples with infertility participated in the study (median [IQR] age for female partners, 33 [30-37] years), with 135 couples in the SARS-CoV-2-positive group and 450 in the SARS-CoV-2-negative group. The characteristics of the groups were similar. The SARS-CoV-2-positive group had a significantly lower top-quality embryo rate (odds ratio [OR], 0.83; 95% CI, 0.71-0.96), top-quality blastocyst rate (OR, 0.59; 95% CI, 0.45-0.77), available blastocyst rate (OR, 0.70; 95% CI, 0.59-0.82), and blastocyst formation rate (OR, 0.61; 95% CI, 0.52-0.71) than the SARS-CoV-2-negative group. Analysis of the associations of infection by sex showed that the female positive group had impaired oocyte and embryo quality regarding mature oocyte rate, 2PN cleavage rate, top-quality embryo rate, blastocyst formation rate, available blastocyst rate, and top-quality blastocyst rate compared with the SARS-CoV-2-negative group. Compared with the SARS-CoV-2-negative group, the male positive group and the group of couples with both positive partners had significantly decreased available blastocyst rate, top-quality blastocyst rate, and blastocyst formation rate compared with the SARS-CoV-2 negative group.

Conclusions and Relevance

In this cohort study, SARS-CoV-2 infection during COS was negatively associated with embryo and blastocyst quality. Reproductive physicians should be more attentive to patients with SARS-CoV-2 infection during COS and should give couples who have been infected adequate counseling.

SARS-CoV-2, fertility and assisted reproduction

BACKGROUND

In 2020, SARS-CoV-2 and the COVID-19 pandemic had a huge impact on the access to and provision of ART treatments. Gradually, knowledge of the virus and its transmission has become available, allowing ART activities to resume. Still, questions on the impact of the virus on human gametes and fertility remain.

OBJECTIVE AND RATIONALE

This article summarizes published data, aiming to clarify the impact of SARS-CoV-2 and the COVID-19 disease on human fertility and assisted reproduction, as well as the impact of vaccination, and from this, provide answers to questions that are relevant for people contemplating pregnancy and for health care professionals.

SEARCH METHODS

PUBMED/MEDLINE and the WHO COVID-19 database were searched from inception to 5 October 2022 with search terms focusing on 'SARS-CoV-2' and gametes, embryos, reproductive function, fertility and ART. Non-English studies and papers published prior to 2020 were excluded, as well as reviews and non-peer reviewed publications. Full papers were assessed for relevance and quality, where feasible.

OUTCOMES

From the 148 papers included, the following observations were made. The SARS-CoV-2-binding proteins, angiotensin-converting enzyme 2 (ACE2) and type II transmembrane serine protease (TMPRSS2), are expressed in the testis, but co-expression remains to be proven. There is some evidence of SARS-CoV-2 RNA in the ejaculate of COVID-19 patients with severe disease, but not in those with mild/moderate disease. SARS-CoV-2 infection can impair spermatogenesis, but this seems to resolve after one spermatogenic cycle. Testosterone levels seem to be lower during and after COVID-19, but long-term data are lacking; disease severity may be associated with testosterone levels. COVID-19 cannot be considered a sexually transmitted disease. There is no co-expression of ACE2 and TMPRSS2 in the myometrium, uterus, ovaries or fallopian tubes. Oocytes seem to have the receptors and protease machinery to be susceptible to SARS-CoV-2 infection; however, viral RNA in oocytes has not been detected so far. Women contemplating pregnancy following COVID-19 may benefit from screening for thyroid dysfunction. There is a possible (transient) impact of COVID-19 on menstrual patterns. Embryos, and particularly late blastocysts, seem to have the machinery to be susceptible to SARS-CoV-2 infection. Most studies have not reported a significant impact of COVID-19 on ovarian reserve, ovarian function or follicular fluid parameters. Previous asymptomatic or mild SARS-CoV-2 infection in females does not seem to negatively affect laboratory and clinical outcomes of ART. There are no data on the minimum required interval, if any, between COVID-19 recovery and ART. There is no evidence of a negative effect of SARS-CoV-2 vaccination on semen parameters or spermatogenesis, ovarian function, ovarian reserve or folliculogenesis. A transient effect on the menstrual cycle has been documented. Despite concerns, cross reactivity between anti-SARS-CoV-2 spike protein antibodies and Syncytin-1, an essential protein in human implantation, is absent. There is no influence of mRNA SARS-CoV-2 vaccine on patients' performance during their immediate subsequent ART cycle. Pregnancy rates post-vaccination are similar to those in unvaccinated patients.

WIDER IMPLICATIONS

This review highlights existing knowledge on the impact of SARS-CoV-2 infection or COVID-19 on fertility and assisted reproduction, but also identifies gaps and offers suggestions for future research. The knowledge presented should help to provide evidence-based advice for practitioners and couples contemplating pregnancy alike, facilitating informed decision-making in an environment of significant emotional turmoil.

Neurotensin expression, regulation, and function during the ovulatory period in the mouse ovary†

The luteinizing hormone (LH) surge induces paracrine mediators within the ovarian follicle that promote ovulation. The present study explores neurotensin (NTS), a neuropeptide, as a potential ovulatory mediator in the mouse ovary. Ovaries and granulosa cells (GCs) were collected from immature 23-day-old pregnant mare serum gonadotropin primed mice before (0 h) and after administration of human chorionic gonadotropin (hCG; an LH analog) across the periovulatory period (4, 8, 12, and 24 h). In response to hCG, Nts expression rapidly increased 250-fold at 4 h, remained elevated until 8 h, and decreased until 24 h. Expression of Nts receptors for Ntsr1 remained unchanged across the periovulatory period, Ntsr2 was undetectable, whereas Sort1 expression (also called Ntsr3) gradually decreased in both the ovary and GCs after hCG administration. To better understand Nts regulation, inhibitors of the LH/CG signaling pathways were utilized. Our data revealed that hCG regulated Nts expression through the protein kinase A (PKA) and p38 mitogen-activated protein kinase (p38MAPK) signaling pathways. Additionally, epidermal-like-growth factor (EGF) receptor signaling also mediated Nts induction in GCs. To elucidate the role of NTS in the ovulatory process, we used a Nts silencing approach (si-Nts) followed by RNA-sequencing (RNA-seq). RNA-seq analysis of GCs collected after hCG with or without si-Nts identified and qPCR confirmed Ell2, Rsad2, Vps37a, and Smtnl2 as genes downstream of Nts. In summary, these findings demonstrate that hCG induces Nts and that Nts expression is mediated by PKA, p38MAPK, and EGF receptor signaling pathways. Additionally, NTS regulates several novel genes that could potentially impact the ovulatory process.

The impact of past COVID-19 infection on pregnancy rates in frozen embryo transfer cycles

PURPOSE

To study the effect of SARS-CoV-2 infection on pregnancy rates in frozen embryo transfer (FET) cycles.

METHODS

A retrospective cohort study including women under the age of 42 with documented SARS-CoV-2 infection up to 1 year prior to treatment, undergoing FET cycles in the first half of 2021, with transfer of embryos generated prior to the infection. Controls were SARS-CoV-2 non-diagnosed, non-vaccinated women matched by age, number, and day of embryo transfer. Demographic and cycle characteristics and outcomes were compared.

RESULTS

Forty-one recovered women and 41 controls were included. Pregnancy rates were 29% and 49% respectively (p = 0.070). Stratification by time from SARS-CoV-2 infection to transfer into ≤ 60 and > 60 days revealed a difference in pregnancy rates, with women in the COVID group having lower pregnancy rates if infected in proximity to the transfer (21% vs. 55%; p = 0.006). In a logistic regression model, infection was a significant variable (p = 0.05, OR 0.325, 95% CI 0.106-0.998). Logistic regression applied on the subgroup of women infected in proximity to the transfer further strengthened the univariate results, with COVID-19 remaining a significant parameter (p = 0.005, OR 0.072, 95% CI 0.012-0.450).

CONCLUSIONS

In FET cycles of patients with past SARS-CoV-2 infection, in which oocytes were retrieved prior to infection, decreased pregnancy rates were observed, specifically in patients who recovered less than 60 days prior to embryo transfer. Pending further studies, in cases of FET cycles with limited number of embryos, postponing embryo transfer for at least 60 days following recovery from COVID-19 might be considered when feasible.

IVF under COVID-19: treatment outcomes of fresh ART cycles

Study Question

Does prior SARS-CoV-2 infection in women undergoing fertility treatments affect the outcomes of fresh ART cycles?

Summary Answer

SARS-CoV-2 infection does not affect fresh ART treatment outcomes, except for a possible long term negative effect on oocyte yield (>180 days post infection).

What Is Known Already

A single previous study suggested no evidence that a history of asymptomatic or mild SARS-CoV-2 infection in females caused impairment of fresh ART treatment outcomes.

Study Design, Size, Duration

Retrospective cohort study, including all SARS-CoV-2 infected women who underwent fresh ART cycles within a year from infection (the first cycle post infection), between October 2020 and June 2021, matched to non-diagnosed controls.

Participants/Materials, Setting, Methods

Patients from two large IVF units in Israel who were infected with SARS-CoV-2 and later underwent fresh ART cycles were matched by age to non-diagnosed, non-vaccinated controls. Demographics, cycle characteristics and cycle outcomes, including oocyte yield, maturation rate, fertilization rate, number of frozen embryos per cycle, and clinical pregnancy rates, were compared between groups.

Main Results And The Role Of Chance

One hundred and twenty-one infected patients and 121 controls who underwent fresh ART cycles were included. Oocyte yield (12.50 versus 11.29; p = 0.169) and mature oocyte rate (78% versus 82%; p = 0.144) in all fresh cycles were similar between groups, as were fertilization rates, number of frozen embryos per cycle and clinical pregnancy rates (43% versus 40%; p = 0.737) in fresh cycles with an embryo transfer. In a logistic regression model, SARS-CoV-2 infection more than 180 days prior to retrieval had a negative effect on oocyte yield (p = 0.018, Slope=-4.08, 95% CI -7.41 – -0.75), although the sample size was small.

Limitations, Reasons For Caution

A retrospective study with data that was not uniformly generated under a study protocol, no antibody testing for the control group.

Wider Implications Of The Findings

The study findings suggest that SARS-CoV-2 infection does not affect treatment outcomes, including oocyte yield, fertilization and maturation rate, number of good quality embryos, and clinical pregnancy rates, in fresh ART cycles, except for a possible long term negative effect on oocyte yield when retrieval occurs > 180 days post SARS-CoV-2 infection. Further studies are warranted to support these findings.

Study funding/competing interest(s)

None.

Trial registration number

0010-21-HMC, 0094-21-ASF