Human eggs, zygotes, and embryos express the receptor ACE2 and protease TMPRSS2 protein necessary for SARS-CoV-2 infection

Rajput, Sandeep K.; Logsdon, Deirdre M.; Kile, Becca; Engelhorn, Heidi J.; Goheen, Ben; Khan, Shaihla; Swain, Jason; McCormick, Sue; Schoolcraft, William B.; Yuan, Ye; Krisher, Rebecca L.

Objective To study mRNA and protein expression of SARS-CoV-2 entry receptors (ACE2, CD147) and proteases (TMPRSS2, CTSL) in human oocytes, embryos, cumulus and granulosa cells. Design Research Study. Setting Clinical IVF treatment center Patient(s) IVF patients treated at the Colorado Center for Reproductive Medicine. Intervention(s) Oocytes (GV, MII) and embryos (1 cell (1C); blastocyst (BL)) were donated to research at disposition by IVF patients. Follicular cells (cumulus (CC); granulosa (GC)) were collected from women undergoing egg retrieval after ovarian stimulation without an ovulatory trigger for IVM/IVF treatment cycles Main Outcome Measure(s) The presence or absence of ACE2, CD147, TMPRSS2, and CTSL mRNA using RT-qPCR and protein using capillary Western blotting in human oocytes, embryos and ovarian follicular cells. Result (s) RT- q-PCR analysis revealed high abundance of ACE2 gene transcripts in GV and MII oocytes compared to CC, GC, and BL. ACE2 protein was only present in MII oocytes, 1C, and BL embryos, but other ACE2 protein variants were observed in all the samples. TMPRSS2 protein was present in all samples while mRNA was observed only at the blastocyst stage. All the samples were positive for CD147 and CTSL mRNA expression. However, cumulus and granulosa cells were the only samples that showed co-expression of both CD147 and CTSL proteins in low abundance. Conclusion(s) Cumulus and granulosa cells are least susceptible to SARS-CoV-2 infection due to the lack of required receptors and proteases combination (ACE2/TMPRSS2 or CD147/CTSL) in high abundance. Co-expression of the ACE2 and TMPRSS2 proteins in MII oocytes, zygotes, and blastocysts demonstrate that these gametes and embryos have the cellular machinery required and thus are potentially susceptible to SARS-CoV-2 infection if exposed to the virus. However, we do not yet know if infection occurs in vivo, or in vitro in an ART setting.