Fiorucci, Stefano

Mechanisms that mediate migration, homing and integration of blood outgrowth endothelial cells (BOEC) to sites of vascular injury are incompletely understood, although matrix metalloproteinases (MMPs) have been implicated in this process. Farnesoid X receptor (FXR) signaling pathway has recently been recognized to regulate vascular wall signaling. The aim of this study was to characterize the expression of FXR in human BOEC and examine signaling pathways relevant to BOEC migration. FXR mRNA and protein levels were detected by reverse‐transcriptase PCR and Western blot. Microarray analysis using a focused human endothelial cell biology array (Superarray) suggested that natural (Chenodeoxycholic acid (CDCA), 0.1–100μM) and synthetic (6‐ethylchenodeoxycholic acid (6‐ECDCA) 0.01–10μM) FXR ligands significantly increased MMP9 transcription which was confirmed by real time PCR and gelatin zymography. SiRNA based silencing of FXR prevented CDCA induced increases in MMP9 mRNA, while retroviral over‐expression of FXR in BOEC enhanced MMP9 mRNA levels. CDCA induced expression of Small Heterodimeric Partner (SHP), a downstream target of FXR. Retroviral over‐expression of SHP increased, whereas siRNA silencing of SHP inhibited CDCA induced MMP9 mRNA levels. Migration analysis using Boyden assay demonstrated that CDCA stimulated migration of BOEC which was blocked by transfection with FXR or MMP9 siRNA (p<0.05; n=5). These studies identify a novel signaling pathway by which a key protein important in cell homing and migration, MMP9, is regulated through a previously unrecognized FXR‐SHP pathway in BOEC. Funded by NIH Grant # DK59615