Gene expression profiling of human peripheral blood lymphocytes cultured in modeled microgravity

In the present study we analyzed miRNA and mRNA expression profiles in human peripheral blood lymphocytes (PBLs) incubated in microgravity condition, simulated by a ground-based Rotating Wall Vessel (RWV) bioreactor. Our results show that 42 miRNAs were differentially expressed in MMG-incubated PBLs compared with 1g-incubated ones. Among these, miR-9-5p, miR-9-3p, miR-155-5p, miR-150-3p, and miR-378-3p were the most dysregulated. To improve the detection of functional miRNA-mRNA pairs we performed gene expression profiles on the same samples assayed for miRNA profiling and we integrated miRNA and mRNA expression data. The functional classification of miRNA-correlated genes evidenced significant enrichments in the biological processes of immune/inflammatory response, signal transduction, regulation of response to stress, regulation of programmed cell death and regulation of cell proliferation. We identified the correlation between miR-9-3p, miR-155-5p, miR-150-3p and miR-378-3p expression with that of genes involved in immune/inflammatory response (eg. IFNG and IL17F), apoptosis (eg. PDCD4 and PTEN) and cell proliferation (eg. NKX3-1 and GADD45A). Experimental assays of cell viability and apoptosis induction validated the results obtained by bioinformatics analyses demonstrating that in human PBLs the exposure to reduced gravitational force increases the frequency of apoptosis and decreases cell proliferation. Gene expression profiling was carried out in MMG-incubated PBLs vs. 1g-incubated PBLs on total RNA extracted from the same PBL samples assayed for miRNA profiling. We used the Whole Human Genome Oligo Microarray (Agilent), consisting of ~41.000 (60-mer) oligonucleotide probes, which span conserved exons across the transcripts of the targeted full-length genes.