Endothelial cell TIMP-1 is upregulated by shear stress via Sp-1 and the TGFβ1 signaling pathways

Endothelial Recovery in Bare Metal Stents and Drug-Eluting Stents on a Single-Cell Level

[Figure: see text].

It Takes Two to Tango: Endothelial TGFβ/BMP Signaling Crosstalk with Mechanobiology

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta (TGFβ) superfamily of cytokines. While some ligand members are potent inducers of angiogenesis, others promote vascular homeostasis. However, the precise understanding of the molecular mechanisms underlying these functions is still a growing research field. In bone, the tissue in which BMPs were first discovered, crosstalk of TGFβ/BMP signaling with mechanobiology is well understood. Likewise, the endothelium represents a tissue that is constantly exposed to multiple mechanical triggers, such as wall shear stress, elicited by blood flow or strain, and tension from the surrounding cells and to the extracellular matrix. To integrate mechanical stimuli, the cytoskeleton plays a pivotal role in the transduction of these forces in endothelial cells. Importantly, mechanical forces integrate on several levels of the TGFβ/BMP pathway, such as receptors and SMADs, but also global cell-architecture and nuclear chromatin re-organization. Here, we summarize the current literature on crosstalk mechanisms between biochemical cues elicited by TGFβ/BMP growth factors and mechanical cues, as shear stress or matrix stiffness that collectively orchestrate endothelial function. We focus on the different subcellular compartments in which the forces are sensed and integrated into the TGFβ/BMP growth factor signaling.

Influence of TGF-β1 expression in endothelial cells on smooth muscle cell phenotypes and MMP production under shear stress in a co-culture model

Recently, our group has contrasted an endothelial cell-smooth muscle cell (EC-SMC) co-culture model with 3D-cultured SMCs and found that SMCs could respond to high shear stress (SS), which has not been explored before. SMCs were not directly exposed to the flow but were under an EC monolayer; therefore, it is necessary to explore the influence of EC on SMC behaviors under high SS for understanding the mechanism of SMC response to various magnitudes of SS. In the present study, TGF-β1 expression in ECs in an EC-SMC co-culture model was suppressed by an siRNA transfection method. Next, phenotypic changes were observed and MMP-2 and -9 productions were measured in SMCs in the co-culture model after 72-h flow exposure to different SS levels. We confirmed that TGF-β1 expression in ECs could influence SMC phenotypic change under SS conditions and that TGF-β1 expression in ECs could also change MMP-2 production but not MMP-9 production in SMCs under SS conditions in the co-culture model. These results could be useful for understanding the mechanisms of SMC response to SS, particularly for understanding signal transduction emanating from ECs.

Crosstalk between Smad2/3 and specific isoforms of ERK in TGF-β1-induced TIMP-3 expression in rat chondrocytes

This study investigated the roles of ERK1 and ERK2 in transforming growth factor‐β1 (TGF‐β1)‐induced tissue inhibitor of metalloproteinases‐3 (TIMP‐3) expression in rat chondrocytes, and the specific roles of ERK1 and ERK2 in crosstalk with Smad2/3 were investigated to demonstrate the molecular mechanism of ERK1/2 regulation of TGF‐β1 signalling. To examine the interaction of specific isoforms of ERK and the Smad2/3 signalling pathway, chondrocytes were infected with LV expressing either ERK1 or ERK2 siRNA and stimulated with or without TGF‐β1. At indicated time‐points, TIMP‐3 expression was determined by real‐time PCR and Western blotting; p‐Smad3, nuclear p‐Smad3, Smad2/3, p‐ERK1/2 and ERK1/2 levels were assessed. And then, aggrecan, type II collagen and the intensity of matrix were examined. TGF‐β1‐induced TIMP‐3 expression was significantly inhibited by ERK1 knock‐down, and the decrease in TIMP‐3 expression was accompanied by a reduction of p‐Smad3 in ERK1 knock‐down cells. Knock‐down of ERK2 had no effect on neither TGF‐β1‐induced TIMP‐3 expression nor the quantity of p‐Smad3. Moreover, aggrecan, type II collagen expression and the intensity of matrix were significantly suppressed by ERK1 knock‐down instead of ERK2 knock‐down. Taken together, ERK1 and ERK2 have different roles in TGF‐β1‐induced TIMP‐3 expression in rat chondrocytes. ERK1 instead of ERK2 can regulate TGF‐β/Smad signalling, which may be the mechanism through which ERK1 regulates TGF‐β1‐induced TIMP‐3 expression.

Tissue Inhibitor of Metalloproteinase 1 Influences Vascular Adaptations to Chronic Alterations in Blood Flow

Remodeling of the skeletal muscle microvasculature involves the coordinated actions of matrix metalloproteinases (MMPs) and their endogenous inhibitors, tissue inhibitor of metalloproteinases (TIMPs). We hypothesized that the loss of TIMP1 would enhance both ischemia and flow-induced vascular remodeling by increasing MMP activity. TIMP1 deficient (Timp1^-/- ) and wild-type (WT) C57BL/6 mice underwent unilateral femoral artery (FA) ligation or were treated with prazosin, an alpha-1 adrenergic receptor antagonist, in order to investigate vascular remodeling to altered flow. Under basal conditions, Timp1^-/- mice had reduced microvascular content as compared to WT mice. Furthermore, vascular remodeling was impaired in Timp1^-/- mice. Timp1^-/- mice displayed reduced blood flow recovery in response to FA ligation and no arteriogenic response to prazosin treatment. Timp1^-/- mice failed to undergo angiogenesis in response to ischemia or prazosin, despite maintaining the capacity to increase VEGF-A and eNOS mRNA. Vascular permeability was increased in muscles of Timp1^-/- mice in response to both prazosin treatment and FA ligation, but this was not accompanied by greater MMP activity. This study highlights a previously undescribed integral role for TIMP1 in both vascular network maturation and adaptations to ischemia or alterations in flow. J. Cell. Physiol. 232: 831-841, 2017. © 2016 Wiley Periodicals, Inc.

Regulation of skeletal muscle capillary growth in exercise and disease

Capillaries, which are the smallest and most abundant type of blood vessel, form the primary site of gas, nutrient, and waste transfer between the vascular and tissue compartments. Skeletal muscle exhibits the capacity to generate new capillaries (angiogenesis) as an adaptation to exercise training, thus ensuring that the heightened metabolic demand of the active muscle is matched by an improved capacity for distribution of gases, nutrients, and waste products. This review summarizes the current understanding of the regulation of skeletal muscle capillary growth. The multi-step process of angiogenesis is coordinated through the integration of a diverse array of signals associated with hypoxic, metabolic, hemodynamic, and mechanical stresses within the active muscle. The contributions of metabolic and mechanical factors to the modulation of key pro- and anti-angiogenic molecules are discussed within the context of responses to a single aerobic exercise bout and short-term and long-term training. Finally, the paradoxical lack of angiogenesis in peripheral artery disease and diabetes and the implications for disease progression and muscle health are discussed. Future studies that emphasize an integrated analysis of the mechanisms that control skeletal muscle capillary growth will enable development of targeted exercise programs that effectively promote angiogenesis in healthy individuals and in patient populations.

Delivery and targeting of miRNAs for treating liver fibrosis

Liver fibrosis is a pathological condition originating from liver damage that leads to excess accumulation of extracellular matrix (ECM) proteins in the liver. Viral infection, chronic injury, local inflammatory responses and oxidative stress are the major factors contributing to the onset and progression of liver fibrosis. Multiple cell types and various growth factors and inflammatory cytokines are involved in the induction and progression of this disease. Various strategies currently being tried to attenuate liver fibrosis include the inhibition of HSC activation or induction of their apoptosis, reduction of collagen production and deposition, decrease in inflammation, and liver transplantation. Liver fibrosis treatment approaches are mainly based on small drug molecules, antibodies, oligonucleotides (ODNs), siRNA and miRNAs. MicroRNAs (miRNA or miR) are endogenous noncoding RNA of ~22 nucleotides that regulate gene expression at post transcription level. There are several miRNAs having aberrant expressions and play a key role in the pathogenesis of liver fibrosis. Single miRNA can target multiple mRNAs, and we can predict its targets based on seed region pairing, thermodynamic stability of pairing and species conservation. For in vivo delivery, we need some additional chemical modification in their structure, and suitable delivery systems like micelles, liposomes and conjugation with targeting or stabilizing the moiety. Here, we discuss the role of miRNAs in fibrogenesis and current approaches of utilizing these miRNAs for treating liver fibrosis.