Objective: SARS-CoV-2 entry in host cells requires the presence of angiotensin-converting enzyme 2 (ACE2) as the extracellular receptor, and the serine protease TMPRSS2 to cleave the viral spike protein for incorporation into the host cell. Basigin (BSG/CD147) may also act as an ACE2 independent receptor mechanism. The cysteine protease cathepsin-L (CTSL) may also cleave the viral spike proteins and facilitate cell entry. The objective of this study was to characterize the mRNA and protein expression of these cellular entry receptors and proteases in female reproductive cells to determine their susceptibility to SARS-CoV-2 infection. Design: Prospective Research Study. Materials and Methods: Materials and Methods: Oocytes (GV, MII), follicular cells (cumulus, CC;granulosa, GC) and embryos (1 cell, 1C;blastocyst, BL) were collected from a minimum of three different patients per sample type, with consent. Samples were analyzed for mRNA expression of ACE2, CD147, TMPRSS2, and CTSL genes relative to GAPDH using RT-qPCR. Primers were validated using human mixed tissue cDNA. Protein quantification was performed by immunoblotting using the Jess system (ProteinSimple) optimized to detect over 10 proteins/5-10 oocytes or embryos. Antibodies for ACE2, CD147, TMPRSS2, and CTSL proteins were validated and then used to determine protein abundance relative to total protein. Data were obtained from three independent biological replicates and analyzed using one-way ANOVA. Results: Results from q-PCR analysis revealed high (p<0.05) abundance of ACE2 transcripts in GV and MII oocytes compared to CC, GC, and BL. ACE2 protein was present in all the samples, but was relatively higher (p<0.17) in M2 oocytes, 1C, BL, and CC compared to GV oocytes and GC. TMPRSS2 protein was abundant in MII oocytes, 1C, and BL, and was present but at low levels in GV oocytes and follicular cells. Protein abundance of CD147 was five-fold higher (p<0.05) in GV and ∼1.5 fold higher in GC compared to all other samples analyzed. No CTSL protein was observed with the expected molecular weight (38 kD), although a 55 kD band (a possible isoform) was detected in GV oocytes and CC. Conclusions: Cumulus and granulosa cells are least susceptible to SARS-CoV-2 infection due to the lack of required receptors and proteases. Co-expression of the protein for ACE2 and TMPRSS2 in MII oocytes, zygotes, and blastocysts suggests that these reproductive cells are susceptible to SARS-CoV-2 infection. In conclusion, using a combined approach of mRNA and protein analysis from the same samples suggests that mature human oocytes and preimplantation embryos have the cellular machinery required for SARS-Cov2 entry, although we do not know if this occurs in vivo. The potential for viral infection in oocytes and embryos has important ramifications for ART. Care must be taken to avoid introduction of the virus to the embryo while in the ART laboratory, as well as potentially introducing the virus from an infected embryo to laboratory workspaces.
MATURE HUMAN OOCYTES AND PRE-IMPLANTATION EMBRYOS ARE SUSCEPTIBLE TO SARS-COV-2 INFECTION BASED ON THE PRESENCE OF ACE2 AND TMPRSS2 PROTEINS