SARS-CoV-2: Myth on Pregnancy Outcomes
A research report of University in San Francisco, California, reveals that COVID-19 shows badly impact on pregnancy related outcomes like premature birth, transmission to babies via breast milk and infertility.
During this pandemic, fear have arisen about the potential impact of the disease on reproductive outcomes.
But there are only few studies have suggested that the SARS-CoV-2 may cause miscarriages, premature birth, stillbirth and restricted foetal growth due to placental abnormalities.
However, the studies found that none of the reproductive tissues are susceptible to infection with SARS-CoV-2.
Entry of SARS-CoV-2 into Cells:
SARS-CoV-2 bind with ACE2 cell surface receptors of host cells using their spike protein, which is then primed by Transmembrane Protease Serine 2 [TMPRSS2] to facilitate viral entry.
In the absence of TMPRSS2, the virus can use alternatively Proteases Cathepsin B [CTSB] and Cathepsin L [CTSL] to enter host cells.
The study on Single-Cell Sequencing database have shown increased expression of ACE2 and TMPRSS2 in the Nostril and Lungs. SARS-CoV-2 also shown susceptibility to other than the Respiratory tract, including heart, colon and cornea.
Fear about the impact on Pregnancy:
According to the research studies SARS-CoV-2 can affect multiple organs, significant concerns have arisen regarding the impact on Pregnancy and fertility-related outcomes.
Only a number of research data available which have suggested the virus can cause Miscarriage, Premature birth, Stillbirth and Restricted foetal-growth owing to placental abnormalities.
However, these researches are too small and generated conflicting data, it is still unclear that SARS-CoV-2 affecting pregnancy and transmitted or not.
According to the reports, have investigated the cell-specific expression of ACE2 and the Proteases TMPRSS2, CTSB and CTSL in female reproductive organs.
The researchers used single-cell RNA sequencing datasets from the Uterus, Myometrium, Ovary, fallopian tube and Breast.
· Critical insights into expression of SARS-CoV-2 receptor and proteases TMPRSS2, CTSB/ CTSL in the female reproductive tract.
Presence of SARS-CoV-2 in Uterus and Myometrium:
The researchers identified very low expression of ACE2 in Stromal and Endothelial cells of the Uterus.
There is no any proteases expressed in uterus which can help ACE2 to facilitate viral-host cell entry. So, it seems unlikely that uterus will be affected by COVID-19.
In the Myometrium, that controls uterine contractions and plays a important role in labor onset, here is same no co-expression of ACE2 with TMPRSS2, CTSB or CTSL was identified, suggesting that tissue is also unlikely to be affected.
· SARS-CoV-2 is unlikely to directly contribute to abnormal uterine function which may result in implantation failure, preterm birth and early placentation.
Presence of SARS-CoV-2 in Ovary and Fallopian tube:
There are eight types of Ovarian cells, but ACE2 was expressed in about 1 % of Stromal and Perivascular cells, Proteases TMPRSS2 was not expressed in any cell type.
Same as, very few cells in the Fallopian tube expressed only ACE2 but not TMPRSS2.
· So, together these results suggest that SARS-CoV-2 is unlikely to affect female fertility.
Presence of SARS-CoV-2 in Breast:
There are low expression of ACE2 in Luminal epithelium and Myofibroblasts of Breast epithelium. Still no, co-expression of ACE2 and TMPRSS2, CTSB or CTSL in any of cell types.
· 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 breast feeding are negligible.
At the last, studies suggest that none of the reproductive tissues investigated are likely to be susceptible to SARS-CoV-2 infection.