SLUG Is Expressed in Endothelial Cells Lacking Primary Cilia to Promote Cellular Calcification

Objective—

Arterial calcification is considered a major cause of death and disabilities worldwide because the associated vascular remodeling leads to myocardial infarction, stroke, aneurysm, and pulmonary embolism. This process occurs via poorly understood mechanisms involving a variety of cell types, intracellular mediators, and extracellular cues within the vascular wall. An inverse correlation between endothelial primary cilia and vascular calcified areas has been described although the signaling mechanisms involved remain unknown. We aim to investigate the signaling pathways regulated by the primary cilium that modulate the contribution of endothelial cells to vascular calcification.

Approach and Results—

We found that human and murine endothelial cells lacking primary cilia are prone to undergo mineralization in response to bone morphogenetic proteins stimulation in vitro. Using the Tg737 orpk/orpk cillium-defective mouse model, we show that nonciliated aortic endothelial cells acquire the ability to transdifferentiate into mineralizing osteogenic cells, in a bone morphogenetic protein–dependent manner. We identify β-CATENIN–induced SLUG as a key transcription factor controlling this process. Moreover, we show that the endothelial expression of SLUG is restricted to atheroprone areas in the aorta of LDLR −/− mice. Finally, we demonstrate that SLUG and phospho-homolog of the Drosophila protein, mothers against decapentaplegic (MAD) and the Caenorhabditis elegans protein SMA (from gene sma for small body size)-1/5/8 expression increases in endothelial cells constituting the vasa vasorum in the human aorta during the progression toward atherosclerosis.

Conclusions—

We demonstrated that the lack of primary cilia sensitizes the endothelium to undergo bone morphogenetic protein–dependent-osteogenic differentiation. These data emphasize the role of the endothelial cells on the vascular calcification and uncovers SLUG as a key target in atherosclerosis.

RhoA GTPase-induced ocular hypertension in a rodent model is associated with increased fibrogenic activity in the trabecular meshwork

Ocular hypertension arising from increased resistance to aqueous humor (AH) outflow through the trabecular meshwork is a primary risk factor for open-angle glaucoma, a leading cause of blindness. Ongoing efforts have found little about the molecular and cellular bases of increased resistance to AH outflow through the trabecular meshwork in ocular hypertension patients. To test the hypothesis that dysregulated Rho GTPase signaling and a resulting fibrotic activity within the trabecular meshwork may result in ocular hypertension, we investigated the effects of expressing a constitutively active RhoA GTPase (RhoAV14) in the AH outflow pathway in Sprague-Dawley rats by using lentiviral vector-based gene delivery. Rats expressing RhoAV14 in the iridocorneal angle exhibited a significantly elevated intraocular pressure. Elevated intraocular pressure in the RhoAV14-expressing rats was associated with fibrotic trabecular meshwork and increased levels of F-actin, phosphorylated myosin light chain, α-smooth muscle actin, collagen-1A, and total collagen in the trabecular AH outflow pathway. Most of these changes were ameliorated by topical application of Rho kinase inhibitor. Human autopsy eyes from patients with glaucoma exhibited significant increases in levels of collagen-1A and total collagen in the trabecular AH outflow pathway. Collectively, these observations indicate that increased fibrogenic activity because of dysregulated RhoA GTPase activity in the trabecular AH outflow pathway increases intraocular pressure in a Rho kinase-dependent manner.