O-142 COVID19-free endometrium: Undetectable viral RNA in endometrial biopsies from positive symptomatic SARS-CoV-2 women
Authors: De Miguel-Gómez L , Romeu M , Pellicer N , Faus A , Pellicer A , Cervelló I 
Published: August 2021

Abstract

Study question
Does SARS-CoV-2 infect the endometrial tissue in women with coronavirus disease 2019 (COVID-19)?

Summary answer
Symptomatic women with COVID-19 report no presence, in the short term, of viral RNA from SARS-CoV-2 in the endometrium.

What is known already
The recent emergence of COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has not allowed yet to establish putative relations between this disorder and other existing pathologies. It is the case with fertility problems and the reproductive organs, including a possible endometrial disorder caused by the virus. Thus, an important step is to elucidate the viral presence in different human tissues to improve diagnostics, prevention and/or treatment. The hypothesis of the possible infection of the endometrial tissue comes from the described expression of ACE2 protein in the human endometrium, mainly in stromal cells during the secretory phase.

Study design, size, duration
15 endometrial biopsies from symptomatic and hospitalized women with COVID-19 were collected. Endometrial samples were obtained from August to November 2020 at the Hospital Universitari i Politècnic La Fe (Valencia, Spain); the project received the approval of the hospital’s medical ethics committee (registration number: 2020-268-1). The main objective was to study by real-time PCR (RT-PCR) the presence of viral RNA from SARS-CoV-2 as well as the expression of ACE2 receptor on the endometrial tissue.

Participants/materials, setting, methods
15 women in the reproductive age (24-46 years) accepted to participate in the study and signed the informed consent. All these patients tested positive for SARS-CoV-2 by RT-PCR of nasopharyngeal swabs (1-17 days before the biopsy collection) and were hospitalized due to health complications (pneumonia) derived from COVID-19. Endometrial biopsies were taken by aspiration and preserved in RNA-later until -80ºC cryopreservation in a biobank; RNA was extracted for RT-PCR for N1, N2, and ACE2 genes.

Main results and the role of chance
The 15 recruited patients represented the different phases of the menstrual cycle: proliferative (n = 3) and secretory (n = 10); 2 patients had amenorrhea. The viral RNA for SARS-CoV-2, measured by the detection of N1 and N2 gene targets (fragments of N gene, from the viral nucleocapsid) by RT-PCR methodology, was undetectable in all the endometrial biopsies analyzed (n = 15). In all the cases the housekeeping gene RPP30 was used as positive control and to check RNA integrity. To correlate the presence or absence of SARS-CoV-2 with the organ-specific expression of ACE2 (angiotensin-converting enzyme 2), the main postulated entry receptor of SARS-CoV-2, the endometrial RNA was also analyzed by RT-PCR for the ACE2 receptor gene. This gene was only detectable in 10 of the 15 biopsies, and the levels ranged from 28.65 to 36.19 Ct values, revealing a very low expression of ACE2 in the tissue. Moreover, ACE2 results did not report any correlation with the phase of the menstrual cycle.

Limitations, reasons for caution
These results imply endometrium is safe from SARS-CoV-2 infection, at least in the short term. All the endometrial samples were taken at maximum of 17 days after a positive test by RT-PCR of nasopharyngeal swabs (to note that all were hospitalized during the early stages of the disease).

Wider implications of the findings
In conclusion, the SARS-CoV-2 RNA is not present in the human endometrial tissue of positive patients. This hypothesis was reinforced by the low ACE2 receptor levels. However, an in-depth genetic analysis comparing to a negative control group could elucidate a systemic affectation of the endometrium, despite the negative RT-PCR results.

Trial registration number
not applicable