Spherical nucleic acid targeting microRNA-99b enhances intestinal MFG-E8 gene expression and restores enterocyte migration in lipopolysaccharide-induced septic mice

Milk fat globule-EGF factor 8 (MFG-E8) maintains the intestinal homeostasis by enhancing enterocyte migration and attenuating inflammation. We previously reported that sepsis is associated with down-regulation of intestinal MFG-E8 and impairment of enterocyte migration. Here, we showed that impairment of intestinal epithelial cell migration occurred in lipopolysaccharide (LPS)-induced septic mice. Treatment of RAW264.7 cells (a murine macrophage-like cell line) with LPS increased expression of miR-99b, a microRNA that is predicted to target mouse MFG-E8 3'UTR. Using a luciferase assay, we showed that miR-99b mimic suppressed the activity of a reporter containing MFG-E8 3'UTR. This suggests the role of miR-99b in inhibition of MFG-E8 gene expression. In addition, we developed an anti-miR99b spherical nucleic acid nanoparticle conjugate (SNA-NC(anti-miR99b)). Treatment of both naïve and LPS-challenged cells with SNA-NC(anti-miR99b) enhanced MFG-E8 expression in the cells. Administration of SNA-NC(anti-miR99b) rescued intestinal MFG-E8 expression in LPS-induced septic mice and attenuated LPS inhibitory effects on intestinal epithelial cell migration along the crypt-villus axis. Collectively, our study suggests that LPS represses MFG-E8 expression and disrupts enterocyte migration via a miR-99b dependent mechanism. Furthermore, this work shows that SNA-NC(anti-miR99b) is a novel nanoparticle-conjugate capable of rescuing MFG-E8 gene expression and maintaining intestinal epithelial homeostasis in sepsis.