MSCs-derived secretome counteracts the effect of apoptosis inhibition by SARS-CoV-2 S protein on Calu-3 cells mediated lowered expression of PTGS2

Abstract

Evidence suggests that the safety and applicability of mesenchymal stem/stromal cells (MSCs) to ameliorate the COVID-19. The immunomodulatory and regenerative effects of MSC therapy are mediated via MSC-derived extracellular vesicles. In this direction, an in vitro anti-SARS-CoV-2 assay was simulated using a commercial S protein, the spike (S) glycoprotein of SARS-CoV-2 to stimulate human calu-3 cells. We firstly investigated the biological and molecular functions of S protein in infecting the Calu-3 cells by analyzing the apoptotic and proliferative effects of Calu-3 cells. We found S protein alone could significantly inhibit Calu-3 cell apoptosis with dose dependent manner, even in the presence of actinomycin D (Act D) stimulation. Second, we collected MSC-CM from IFN-γ-pretreated human umbilical cord MSCs (hUC-MSCs). Incubation of MSC-CM with Calu-3 cells revealed that MSC-CM counteracts the effect of apoptosis inhibition by S protein. Third, RNA-seq analysis were employed, and hundreds of RNAs including mRNAs, lncRNAs, and circRNAs were found differentially expressed at post-transcriptional level. Functional enrichment analysis suggested that the differential RNAs were highly enriched in inflammatory response, cell adhesion, and apoptotic process pathways. For a mechanistic insight, using differential analysis of key genes combined with PCR and western blots experiments, several molecules were targeted and PTGS2 was possibly considered that mediated the counteraction of the effect of apoptosis inhibition by S protein. Our study possibly put forward a novel function of SARS-CoV-2 S protein, which may have a potent anti-apoptotic ability. In addition, MSC-CM may serve as a potential strategy against SARS-CoV-2 infection in the near future.