COVID-19 Latest: University Of California Research Shows That Female Reproductive Tract Not Affected By SARS-CoV-2 Coronavirus.
: Medical researchers from the University Of California-San Francisco (UCSF) report that the SARS-CoV-2 coronavirus is unlikely to negatively impact pregnancy-related outcomes such as premature birth, transmission to babies, and infertility issues as the female reproductive tract has very extremely low expression of ACE-2 receptors unlike the male testes which studies are showing is affected in many ways with possibility of infertility issues arising as a long term health complication in men.
Initially, during the start of the COVID-19 crisis, concerns were raised about the potential impacts of the disease on reproductive outcomes. A limited number of studies have suggested that the causative agent ie the SARS-CoV-2 coronavirus may cause miscarriages, premature birth, stillbirth, and restricted fetal growth due to placental abnormalities.
Shockingly however, Dr Aleksandar Rajkovic from the departments of both pathology and OB-Gyn at UCSF and colleagues found that none of the reproductive tissues they studied seemed to be susceptible to infection with SARS-CoV-2.
It was observed that none of the cells in the uterus, myometrium (uterine smooth muscle), ovary, fallopian tube, and breast expressed the combination of receptors ad proteases that would be needed to facilitate viral entry.
This may explain why the COVID-19 pandemic seems to have had little impact on the incidence of pregnancy complications and infertility.
The research findings that have yet to have been peer-reviewed are published on a preprint server. https://www.biorxiv.org/content/10.1101/2020.06.20.163097v1
Typically, SARS-CoV-2 binds to the host cell receptor ACE2 using the Spike protein on its surface, which is then primed by transmembrane protease serine 2 (TMPRSS2) to mediate viral entry. Alternatively, in the absence of TMPRSS2, the virus can use the proteases cathepsin B (CTSB) and cathepsin L (CTSL) to enter host cells.
Emerging studies of single-cell sequencing datasets have shown increased expression of ACE2 and TMPRSS2 in the nasal epithelium and lung. They have also shown susceptibility to SARS-CoV-2 in cells other than the respiratory tract, including the heart, colon, and cornea, which may account for symptoms such as cardiovascular inflammation, diarrhea, and conjunctivitis.
Since that SARS-CoV-2 can infect multiple organs, significant concerns have arisen regarding the impact that infected reproductive organs may have on pregnancy- and fertility-related outcomes.
A few past studies have suggested the virus can cause miscarriage, premature birth, stillbirth, and restricted fetal growth owing to placental abnormalities. But, these studies have been small and generated conflicting data, meaning the likelihood of SARS-CoV-2 affecting pregnancy and transmission to the neonate is still unclear.
This new study using single-cell RNA sequencing datasets from the uterus, myometrium, ovary, fallopian tube, and breast has given the researchers critical insights into the expression of SARS-CoV2 receptor and proteases TMPRSS2, CTSB/L in the female reproductive tract.
The researchers identified extremely low expression of ACE2 in stromal and endothelial cells of the uterus.
Significantly ACE2 was not co-expressed with any of the proteases implicated in viral host cell entry, leading the researchers to conclude, “it seems unlikely that the uterus will be affected by COVID-19.”
Also in the myometrium, which controls uterine contractions and plays a crucial role in labor onset, no co-expression of ACE2 with TMPRSS2, CTSB, or CTSL was identified, suggesting that tissue is also unlikely to be affected, say the researchers.
Dr Rajkovic told Thailand Medical News, “SARS-CoV-2 is therefore unlikely to directly contribute to abnormal uterine function which may result in implantation failure, preterm birth, and early placentation.”
Interestingly across eight types of ovarian cells, ACE2 was only expressed in about one percent of stromal and perivascular cells, TMPRSS2 were not expressed in any cell type.
Also very few cells in the fallopian tube expressed ACE2 and none co-expressed ACE2 and TMPRSS2.
The research team did not find any cells co-expressing ACE2 and TMPRSS2 or CTSB/L in either the ovary or the fallopian tube.
Dr Rajkovic added, “Together, these results suggest that SARS-CoV2 is unlikely to affect female fertility. Current obstetric protocols for infected mothers in labor, call for temporary separation of mother and baby to prevent SARS-CoV2 transmission”
Also on analyzing the dataset for breast epithelium, the researchers found low expression of ACE2 in luminal epithelium and myofibroblasts. Still, no ACE2 was co-expressed with TMPRSS2 or CTSB/L in any of the cell types.
Dr Jyoti Goad, a co-researcher on the study, also from UCSF said, “These findings suggest that the virus might not be able to penetrate the mammary gland cells. Therefore, the chances of transmission of the virus through breastfeeding are negligible.”
The study team says that the results suggest that none of the reproductive tissues investigated in this study are likely to be susceptible to SARS-CoV-2 infection.
Dr Joshua Rudolph another co-researcher from the study team and also from UCSF concluded, “Our findings suggest that COVID-19 is unlikely to contribute to pregnancy-related adverse outcomes such as preterm birth, the transmission of COVID-19 through breast milk, and female infertility. These data may explain the low incidence of complications among pregnant women and little evidence for higher infertility.”
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