In the last few years, microRNA-mediated regulation has been shown to be important in viral infections. In fact, viral microRNAs can alter cell physiology and act on the immune system; moreover, cellular microRNAs can regulate the virus cycle, influencing positively or negatively viral replication. Accordingly, microRNAs can represent diagnostic and prognostic biomarkers of infectious processes and a promising approach for designing targeted therapies. In the past 18 months, the COVID-19 infection from SARS-CoV-2 has engaged many researchers in the search for diagnostic and prognostic markers and the development of therapies. Although some research suggests that the SARS-CoV-2 genome can produce microRNAs and that host microRNAs may be involved in the cellular response to the virus, to date, not enough evidence has been provided. In this paper, using a focused bioinformatic approach exploring the SARS-CoV-2 genome, we propose that SARS-CoV-2 is able to produce microRNAs sharing a strong sequence homology with the human ones and also that human microRNAs may target viral RNA regulating the virus life cycle inside human cells. Interestingly, all viral miRNA sequences and some human miRNA target sites are conserved in more recent SARS-CoV-2 variants of concern (VOCs). Even if experimental evidence will be needed, in silico analysis represents a valuable source of information useful to understand the sophisticated molecular mechanisms of disease and to sustain biomedical applications.

The idea that proteins are the main determining factors in the functioning of cells and organisms, and their dysfunctions are the first cause of pathologies, has been predominant in biology and biom

MicroRNAs, secreted by the embryo in blastocoel fluid (BF) and embryo spent culture medium (SCM), regulate important cellular pathways controlling the stemness of inner cell mass, trophectoderm differentiation, and the dialogue between blastocyst and maternal tissues. In recent years, their role as non-invasive biomarkers of embryo quality has been deeply investigated. We compared the expression profiles of 96 microRNAs between BF and SCM from the same embryos, highlighting the differences between these two compartments. We found 10 and 6 microRNAs specifically expressed in BF and in SCM, respectively; 22 microRNAs significantly up-regulated in BF; and 2 significantly up-regulated in SCM. To investigate the role of SCM microRNAs in implantation, we focused on the microRNAs specifically expressed/up-regulated in SCM and absent in blank medium. We deepened our understanding of SCM microRNA’s biological role by building a network of miRNA–mRNA interaction within the signalling pathways crucial in embryo implantation success. We demonstrated that BF and SCM contain different sets of microRNAs playing different and unique roles in embryo implantation and development. Finally, we suggest that there is not a single “ideal” technique to identify the most competent embryo, but an integrated approach is needed to obtain informative results on the health of the embryo.