MiR-221 and miR-130 regulate Hox genes controlling vascular morphogenesis in developing lung

Hoxa5 and Hoxb5 have distinct important functions in lung airway and alveolar formation. In other cell types, Hoxa5 and Hoxb5 have opposing roles in vasculogenesis and are regulated by miR-130a and miR-221, respectively. Hoxb5 and Hoxa5 regulation by these miRNAs in developing lung is unknown. We have previously reported unique changes in miR-130a and miR-221 temporal and cellular expressions in E15–18 fetal mouse lungs. Lung-specific effects of miR130a and miR-221 were studied in mouse E14 whole lungs cultured 48 h with anti-miRs or mimics to miR-130a and miR-221. Anti-miR130a treatment led to smaller lungs with reduced airway branching with increased Hoxa5 and decreased VEGFR2 in mesenchyme. Mimic 130a treated lungs had numerous finely arborized branches extending into central lung regions with decreased Hoxa5 and increased VEGFR2 in mesenchyme. The distal airways of these lungs were lined with cuboidal cells. Conversely, anti-miR-221 treated lungs had more distal branch generations with increased Hoxb5 and VEGFR2 around airways. Mimic 221 treated lungs had reduced airway branching, dilated airway tips and decreased Hoxb5 and VEGFR2 in mesenchyme. Vascular morphology (Lectin immunofluorescence) showed that miR-221 inhibition and miR-130 enhancement of vascular plexus formation likely impact lung airway branching. MiR-130a and miR-221 temporal, spatial and cell-specific expressions and their opposing effects on airway branching support lung-specific regulation of Hoxa5 and Hoxb5 expressions by miR-130a and miR221, respectively. We speculate that miRNA–Hox regulatory interactions in developing lung contribute to vascular and epithelial differentiation.