No abstract

Mechanical signals regulate blood vessel development in vivo, and have been demonstrated to regulate signal transduction of endothelial cell (EC) and smooth muscle cell (SMC) phenotype in vitro. However, it is unclear how the complex process of angiogenesis, which involves multiple cell types and growth factors that act in a spatiotemporally regulated manner, is triggered by a mechanical input. Here, we describe a mechanism for modulating vascular cells during sequential stages of an in vitro model of early angiogenesis by applying cyclic tensile strain. Cyclic strain of human umbilical vein (HUV)ECs up-regulated the secretion of angiopoietin (Ang)-2 and PDGF-␤␤, and enhanced endothelial migration and sprout formation, whereas effects were eliminated with shRNA knockdown of endogenous Ang-2. Applying strain to colonies of HUVEC, cocultured on the same micropatterned substrate with nonstrained human aortic (HA)SMCs, led to a directed migration of the HASMC toward migrating HUVECs, with diminished recruitment when PDGF receptors were neutralized. These results demonstrate that a singular mechanical cue (cyclic tensile strain) can trigger a cascade of autocrine and paracrine signaling events between ECs and SMCs critical to the angiogenic process.angiogenesis ͉ angiopoietin-2 ͉ endothelial cells ͉ shRNA ͉ strain gradient

For over a century, amphibian embryos have been a source of significant insight into developmental mechanisms, including fundamental discoveries about the process of induction. The recently developed transgenesis for Xenopus offers new approaches to these poorly understood processes, particularly when undertaken in the quickly maturing species Xenopus tropicalis, which greatly facilitates establishment of permanent transgenic lines. Several X.

Pulmonary fibrosis is a fatal progressive disease with no effective therapy. Transforming growth factor (TGF)-β1 has long been regarded as a central mediator of tissue fibrosis that involves multiple organs including skin, liver, kidney, and lung. Thus, TGF-β1 and its signaling pathways have been attractive therapeutic targets for the development of antifibrotic drugs. However, the essential biological functions of TGF-β1 in maintaining normal immune and cellular homeostasis significantly limit the effectiveness of TGF-β1-directed therapeutic approaches. Thus, targeting downstream mediators or signaling molecules of TGF-β1 could be an alternative approach that selectively inhibits TGF-β1-stimulated fibrotic tissue response while preserving major physiological function of TGF-β1. Recent studies from our laboratory revealed that TGF-β1 crosstalk with epidermal growth factor receptor (EGFR) signaling by induction of amphiregulin, a ligand of EGFR, plays a critical role in the development or progression of pulmonary fibrosis. In addition, chitotriosidase, a true chitinase in humans, has been identified to have modulating capacity of TGF-β1 signaling as a new biomarker and therapeutic target of scleroderma-associated pulmonary fibrosis. These newly identified modifiers of TGF-β1 effector function significantly enhance the effectiveness and flexibility in targeting pulmonary fibrosis in which TGF-β1 plays a significant role.

In the nematode Caenorhabditis elegans, RNA interference (RNAi) triggered by double-stranded RNA (dsRNA) spreads systemically to cause gene silencing throughout the organism and its progeny. We confirm that Caenorhabditis nematode SID-1 orthologs have dsRNA transport activity and demonstrate that the SID-1 paralog CHUP-1 does not transport dsRNA. Sequence comparison of these similar proteins, in conjunction with analysis of loss-of-function missense alleles, identifies several conserved 2–7 amino acid microdomains within the extracellular domain (ECD) that are important for dsRNA transport. Among these missense alleles, we identify and characterize a sid-1 allele, qt95, which causes tissue-specific silencing defects most easily explained as a systemic RNAi export defect. However, we conclude from genetic and biochemical analyses that sid-1(qt95) disrupts only import, and speculate that the apparent export defect is caused by the cumulative effect of sequentially impaired dsRNA import steps. Thus, consistent with previous studies, we fail to detect a requirement for sid-1 in dsRNA export, but demonstrate for the first time that SID-1 functions in the intestine to support environmental RNAi (eRNAi).