Disturbed Flow Promotes Arterial Stiffening Through Thrombospondin-1

Abstract

Background Arterial stiffness and wall shear stress are powerful determinants of cardiovascular health, and arterial stiffness is associated with increased cardiovascular mortality. Low and oscillatory wall shear stress, termed disturbed flow (d-flow), promotes atherosclerotic arterial remodeling, but the relationship between d-flow and arterial stiffness is not well understood. The objective of this study was to define the role of d-flow on arterial stiffening and discover the relevant signaling pathways by which d-flow stiffens arteries. Methods D-flow was induced in the carotid arteries of young and old mice of both sexes. Arterial stiffness was quantified ex vivo with cylindrical biaxial mechanical testing and in vivo from duplex ultrasound and compared to unmanipulated carotid arteries from 80-week-old mice. Gene expression and pathway analysis was performed on endothelial cell-enriched RNA and validated by immunohistochemistry. In vitro testing of signaling pathways was performed under oscillatory and laminar wall shear stress conditions. Human arteries from regions of d-flow and stable flow (s-flow) were tested ex vivo to validate critical results from the animal model. Results D-flow induced arterial stiffening through collagen deposition after partial carotid ligation, and the degree of stiffening was similar to that of unmanipulated carotid arteries from 80-week-old mice. Intimal gene pathway analyses identified that transforming growth factor-beta (TGF-β) pathways having a prominent role in this stiffened arterial response, but that this was due to thrombospondin-1 (TSP-1) stimulation of profibrotic genes and not changes to TGF- β. In vitro and in vivo testing under d-flow conditions identified a possible role for TSP-1 activation of TGF-β in the upregulation of these genes. TSP-1 knockout animals had significantly less arterial stiffening in response to d-flow than wild type carotid arteries. Human arteries exposed to d-flow had similar increases TSP-1 and collagen gene expression as seen in our model. Conclusions TSP-1 has a critical role in shear-mediated arterial stiffening that is mediated in part through TSP-1’s activation of TGF-β’s profibrotic signaling pathways. Molecular targets in this pathway may lead to novel therapies to limit arterial stiffening and the progression of disease in arteries exposed to d-flow.

Role of Thrombospondin-1 in Mechanotransduction and Development of Thoracic Aortic Aneurysm in Mouse and Humans

“…TGFβ by forming a positive feedback loop, also induces Thbs1 expression in a Smad2-dependent manner 44 and this pathway can be amplified by Ang II, as TGFβ is a transcriptional target of Ang II 45 . In addition, recent studies have shown that physical factors such as hypoxia and disturbed flow induce Thbs1 36, 46 . In SMKO aortas, Thbs1 is highly upregulated in ECs and inner portions of SMCs in the ascending aortas, supporting the relationship between physical factors and Thbs1 expression.…”

Thrombospondin-1 regulation of latent TGF-β activation: A therapeutic target for fibrotic disease

“…Both TSP-1 and TGF-β are upregulated in pulmonary arterial hypertension due to chronic hypoxia, Schistosomiasis, and in scleroderma: recent studies show that thbs1 knockout or treatment with the peptide antagonist LSKL protected against development of pulmonary hypertension due to hypoxia or Schistosome infection and also reduced active TGF-β [116]. In models of disturbed arterial flow leading to arterial stiffness in aged mice, TSP-1 and markers of pro-fibrotic TGF-β pathways were upregulated: in thbs1 knockout mice or mice treated with LSKL via intraperitoneal administration and subjected to disturbed flow, there was reduced arterial collagen, connective tissue growth factor, and stiffening [117]. Other studies show that LSKL blocks the development of endomyocardial fibrosis in mice with genetic deletion of inhibitor of DNA binding 1 and 3 (Id1 and Id3), a suppressor of TSP-1 expression [118].…”

Feeling Things Out: Bidirectional Signaling of the Cell–ECM Interface, Implications in the Mechanobiology of Cell Spreading, Migration, Proliferation, and Differentiation

“…The adhesive glycoprotein thrombospondin is commonly observed in vasculature and isoform thrombospondin‐1 mediates cell behavior by sensing shear stresses, though the structural basis for this phenomenon is still poorly understood 35. In the arterial wall, disturbed flow upregulates thrombospondin‐1 expression and leads to wall stiffening through the activation of profibrotic genes and may contribute to the progression of vascular diseases such as atherosclerosis 36. Conversely, lack of hydrodynamic shear stress on thrombospondin‐1 initiates endothelial cell apoptosis through an autocrine loop containing thrombospondin‐1 and its cell surface receptor, αVβ3 35.…”