VascularPressure-induced cellular senescence: A mechanism linking venous hypertension to venous ulcers1
Introduction
Chronic venous insufficiency (CVI) is a debilitating condition which often produces painful ulcers that are difficult to heal [1, 2, 3]. CVI produces elevated ambulatory venous pressures and, while it is known that the risk of ulceration relates to the degree of venous pressure elevation [4, 5], the exact mechanism of ulceration and delayed healing is unknown [6]. We have previously shown that when fibroblasts (a dermal element critical to wound healing) are isolated from venous ulcers, they show slowed growth and elevated levels of senescence markers [7, 8]. These initial studies suggest that elevations in venous pressures are related to premature aging of fibroblasts from patients with CVI. To test the hypothesis that elevated pressure produces premature senescence in dermal fibroblasts, we have developed an in vitro model using a special pressurized incubator [9] and a methodology to specifically test for cellular senescence. In addition, because TGF-β has been implicated as a possible mediator of inflammation and delayed healing of venous ulcers [10, 11], we examined the effects of both pressure and TGF-β on cellular senescence, hypothesizing that TGF-β would accelerate the aging phenomenon.
Section snippets
Materials and methods
This study was approved by the University of Vermont Committee on Human Research (Protocol CRMS 02–156) and all procedures were in accordance with the ethical standards of the Committee as well as the Helsinki Declaration of 1975.
Cell morphology
Light microscopy demonstrated morphological differences between the two populations of cells: NNF grown at ATM appeared normal, with compact, tapered morphologies and well-defined, regular nuclei, while NNF grown at ATM +120 were larger and pleomorphic, demonstrating an increased cytoplasm-to-nuclear ratio and irregular nuclei (Fig. 1). With Trypan blue staining, all cells incubated under pressure had less than 0.5% positive staining. This is similar to previously reported findings with this
Discussion
Our previous work with this model [9] suggested that cells grown under pressure demonstrated morphology similar to cells from venous ulcers, with altered morphology and reduced growth rates compared to those grown under atmospheric pressure. While cells grown in culture may demonstrate differences in morphology based upon the degree of confluence, the pressure treated cells display slowed growth characteristics and morphologies that do not lead to confluence. The pictures supplied represent
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Venous Ulcers
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2017, Journal of Vascular Surgery: Venous and Lymphatic DisordersCitation Excerpt :Venous hypertension itself induces a senescence phenotype in dermal fibroblasts. This was shown by Stanley et al, who over several studies cultured dermal fibroblasts under varying levels of atmospheric pressure and found that senescence was seen after 14 days at 1 atm + 60 mm Hg and 1 atm + 120 mm Hg.44 The delineation and characteristics of senescence vs apoptosis have been previously reviewed by Raffetto et al.45 As these dermal fibroblasts enter a state of senescence under increased pressure, they then are resistant to apoptosis and more likely to undergo necrosis.
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Epithelial overexpression of SOCS-3 in transgenic mice exacerbates wound inflammation in the presence of elevated TGF-Β1
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Decreased osteogenesis, increased cell senescence and elevated Dickkopf-1 secretion in human fracture non union stromal cells
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