Endothelial cells transduce mechanical forces from blood flow into intracellular signals required for vascular homeostasis. Here we show that endothelial NOTCH1 is responsive to shear stress, and is necessary for the maintenance of junctional integrity, cell elongation, and suppression of proliferation, phenotypes induced by laminar shear stress. NOTCH1 receptor localizes downstream of flow and canonical NOTCH signaling scales with the magnitude of fluid shear stress. Reduction of NOTCH1 destabilizes cellular junctions and triggers endothelial proliferation. NOTCH1 suppression results in changes in expression of genes involved in the regulation of intracellular calcium and proliferation, and preventing the increase of calcium signaling rescues the cell–cell junctional defects. Furthermore, loss of Notch1 in adult endothelium increases hypercholesterolemia-induced atherosclerosis in the descending aorta. We propose that NOTCH1 is atheroprotective and acts as a mechanosensor in adult arteries, where it integrates responses to laminar shear stress and regulates junctional integrity through modulation of calcium signaling.

The cellular and mechanistic bases underlying endothelial regeneration of adult large vessels have proven challenging to study. Using a reproducible in vivo aortic endothelial injury model, we characterized cellular dynamics underlying the regenerative process through a combination of multi-color lineage tracing, parabiosis, and single-cell transcriptomics. We found that regeneration is a biphasic process driven by distinct populations arising from differentiated endothelial cells. The majority of cells immediately adjacent to the injury site re-enter the cell cycle during the initial damage response, with a second phase driven by a highly proliferative subpopulation. Endothelial regeneration requires activation of stress response genes including Atf3, and aged aortas compromised in their reparative capacity express less Atf3. Deletion of Atf3 reduced endothelial proliferation and compromised the regeneration. These findings provide important insights into cellular dynamics and mechanisms that drive responses to large vessel injury.

Purpose of review Reception and transmission of signals across the plasma membrane has been a function generally attributed to transmembrane proteins. In the last three years, however, a growing number of reports have further acknowledged important contributions played by membrane lipids in the process of signal transduction. Recent findings In particular, the constituency of membrane lipids can regulate how proteins with SH2 domains and molecules like K-Ras expose their catalytic domains to the cytosol and interact with effectors and second messengers. Recent reports have also shown that the degree of saturation of phospholipids can reduce the activation of certain G-protein coupled receptors, as well as signaling downstream to Toll-like receptor 4 with consequences to NFkB activation and inflammation. Levels of specific gangliosides in the membrane were reported to activate integrins in a cell-autonomous manner affecting tumor cell migration. Furthermore, high resolution of the association of cholesterol with the Smoothened receptor has clarified its participation in sonic hedgehog signaling. These are some of the key advancements that have further propelled our understanding of the broad versatile contributions of membrane lipids in signal transduction. Summary As we gain definitive detail regarding the impact of lipid-protein interactions and their consequences to cell function, the options for therapeutic targeting expand with the possibility of greater specificity.

Background: This presentation of a six-year study processing human islets for research and transplantation includes a review of multi-center transplant studies identifying key variables critical for successful islet processing and defines standardized processing procedures required to provide highly purified, functional Human Islets. Methods: Human islet processing methods are defined in detail with pancreas retrieval, shipping, trimming for processing, collagenase distension, controlled digestion by digestion/filtration method, islet purification and islet culture. Islet processing results are summarized from 27 published reports (2003-2017) from 21 international clinical islet transplant centers with 13 single islet centers and 8 from multi-center clinical trials that averaged islet yields of 5,680 IEQ/Gm (Pre-Purification), 4,101 IEQ/Gm (Post-Purification), and 3,599 IEQ/Gm (Post-Culture) with 59.2% purity at time of islet transplant into the liver.

No abstract