Notch and transforming growth factor-␤ (TGF␤) play pivotal roles during vascular development and the pathogenesis of vascular disease. The interaction of these two pathways is not fully understood. The present study utilized primary human smooth muscle cells (SMC) to examine molecular cross-talk between TGF␤1 and Notch signaling on contractile gene expression. Activation of Notch signaling using Notch intracellular domain or Jagged1 ligand induced smooth muscle ␣-actin (SM actin), smooth muscle myosin heavy chain, and calponin1, and the expression of Notch downstream effectors hairy-related transcription factors. Similarly, TGF␤1 treatment of human aortic smooth muscle cells induced SM actin, calponin1, and smooth muscle protein 22-␣ (SM22␣) in a dose-and time-dependent manner. Hairy-related transcription factor proteins, which antagonize Notch activity, also suppressed the TGF␤1-induced increase in SMC markers, suggesting a general mechanism of inhibition. We found that Notch and TGF␤1 cooperatively activate SMC marker transcripts and protein through parallel signaling axes. Although the intracellular domain of Notch4 interacted with phosphoSmad2/3 in SMC, this interaction was not observed with Notch1 or Notch2. However, we found that CBF1 co-immunoprecipitated with phosphoSmad2/3, suggesting a mechanism to link canonical Notch signaling to phosphoSmad activity. Indeed, the combination of Notch activation and TGF␤1 treatment led to synergistic activation of a TGF␤-responsive promoter. This increase corresponded to increased levels of phosphoSmad2/3 interaction at Smad consensus binding sites within the SM actin, calponin1, and SM22␣ promoters. Thus, Notch and TGF␤ coordinately induce a molecular and functional contractile phenotype by co-regulation of Smad activity at SMC promoters.

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Notch signaling in the cardiovascular system is important during embryonic development, vascular repair of injury, and vascular pathology in humans. The vascular smooth muscle cell (VSMC) expresses multiple Notch receptors throughout its life cycle, and responds to Notch ligands as a regulatory mechanism of differentiation, recruitment to growing vessels, and maturation. The goal of this review is to provide an overview of the current understanding of the molecular basis for Notch regulation of VSMC phenotype. Further, we will explore Notch interaction with other signaling pathways important in VSMC.

Over the past twenty years, evidence has accumulated that biochemically and spatially defined networks of extracellular matrix, cellular components, and interactions dictate cellular differentiation, proliferation, and function in a variety of tissue and diseases. Modeling in vivo systems in vitro has been undeniably necessary, but when simplified 2D conditions rather than 3D in vitro models are used, the reliability and usefulness of the data derived from these models decreases. Thus, there is a pressing need to develop and validate reliable in vitro models to reproduce specific tissue-like structures and mimic functions and responses of cells in a more realistic manner for both drug screening/disease modeling and tissue regeneration applications. In adipose biology and cancer research, these models serve as physiologically relevant 3D platforms to bridge the divide between 2D cultures and in vivo models, bringing about more reliable and translationally useful data to accelerate benchtop to bedside research. Currently, no model has been developed for bone marrow adipose tissue (BMAT), a novel adipose depot that has previously been overlooked as "filler tissue" but has more recently been recognized as endocrine-signaling and systemically relevant. Herein we describe the development of the first 3D, BMAT model derived from either human or mouse bone marrow (BM) mesenchymal stromal cells (MSCs). We found that BMAT models can be stably cultured for at least 3 months in vitro, and that myeloma cells (5TGM1, OPM2 and MM1S cells) can be cultured on these for at least 2 weeks. Upon tumor cell co-culture, delipidation occurred in BMAT adipocytes, suggesting a bidirectional relationship between these two important cell types in the malignant BM niche. Overall, our studies suggest that 3D BMAT represents a "healthier," more realistic tissue model that may be useful for elucidating the effects of MAT on tumor cells, and tumor cells on MAT, to identify novel therapeutic targets. In addition, proteomic characterization as well as microarray data (expression of >22,000 genes) coupled with KEGG pathway analysis and gene set expression analysis (GSEA) supported our development of less-inflammatory 3D BMAT compared to 2D culture. In sum, we developed the first 3D, tissue-engineered bone marrow adipose tissue model, which is a versatile, novel model that can be used to study numerous diseases and biological processes involved with the bone marrow.

Blood vessel expansion is driven by sprouting angiogenesis of endothelial cells, and is essential for development, wound healing and disease. Membrane-localized vascular endothelial growth factor receptor-1 (mVEGFR1) is an endothelial cell-intrinsic decoy receptor that negatively modulates blood vessel morphogenesis. Here we show that dynamic regulation of mVEGFR1 stability and turnover in blood vessels impacts angiogenesis. mVEGFR1 is highly stable and constitutively internalizes from the plasma membrane. Post-translational palmitoylation of mVEGFR1 is a binary stabilization switch, and ligand engagement leads to depalmitoylation and lysosomal degradation. Trafficking of palmitoylation enzymes via Rab27a regulates mVEGFR1 stability, as reduced levels of Rab27a impaired palmitoylation of mVEGFR1, decreased its stability, and elevated blood vessel sprouting and in vivo angiogenesis. These findings identify a regulatory axis affecting blood vessel morphogenesis that highlights exquisite post-translational regulation of mVEGFR1 in its role as a molecular rheostat.

Rationale Deregulated vascular smooth muscle cell (VSMC) proliferation contributes to multiple vascular pathologies, and Notch signaling regulates VSMC phenotype. Objective Previous work focused on Notch1 and Notch3 in VSMC during vascular disease; however, the role of Notch2 is unknown. Because injured murine carotid arteries display increased Notch2 in VSMC as compared to uninjured arteries, we sought to understand the impact of Notch2 signaling in VSMC. Methods and Results In human primary VSMC, Jagged-1 (Jag-1) significantly reduced proliferation through specific activation of Notch2. Increased levels of p27kip1 were observed downstream of Jag-1/Notch2 signaling, and required for cell cycle exit. Jag-1 activation of Notch resulted in increased phosphorylation on serine 10, decreased ubiquitination and prolonged half-life of p27kip1. Jag-1/Notch2 signaling robustly decreased S-phase kinase associated protein (Skp2), an F-box protein that degrades p27kip1 during G1. Over expression of Skp2 prior to Notch activation by Jag-1 suppressed the induction of p27kip1. Additionally, increased Notch2 and p27kip1 expression was co-localized to the non-proliferative zone of injured arteries as indicated by co-staining with proliferating cell nuclear antigen (PCNA), whereas Notch3 was expressed throughout normal and injured arteries, suggesting Notch2 may negatively regulate lesion formation. Conclusions We propose a receptor specific function for Notch2 in regulating Jag-1-induced p27kip1 expression and growth arrest in VSMC. During vascular remodeling, co-localization of Notch2 and p27kip1 to the non-proliferating region supports a model where Notch2 activation may negatively regulate VSMC proliferation to lessen the severity of the lesion. Thus Notch2 is a potential target for control of VSMC hyperplasia.

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Authors are urged to introduce these corrections into any reprints they distribute. Secondary (abstract) services are urged to carry notice of these corrections as prominently as they carried the original abstracts.