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Helm, Douglas

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Helm

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Douglas

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Helm, Douglas
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    Microdeformation of Three-Dimensional Cultured Fibroblasts Induces Gene Expression and Morphological Changes
    (Ovid Technologies (Wolters Kluwer Health), 2011) Lu, Feng; Ogawa, Rei; Nguyen, Dinh T.; Chen, Bin; Guo, Danfeng; Helm, Douglas; Zhan, Qian; Murphy, George; Orgill, Dennis
    Background: Vacuum-assisted closure induces microdeformations of the wound surface and accelerates healing of complex wounds; however, a thorough understanding of the biology of cellular mechanotransduction is lacking. We hypothesized that fibroblast shape and function can be altered in an in vitro vacuum-assisted closure device. Methods: A 3-dimensional fibrin matrix with cultured murine fibroblasts and an intervening polyurethane foam was exposed to 125 mm Hg suction and compared with similar wells without suction. We measured fibroblast proliferation and morphology using fluorescence microscopy and gene expression change using real-time reverse-transcriptase polymerase chain reaction at 24, 48, and 72 hours. Results: Wells exposed to suction induced significant proliferation of fibroblasts and morphologic changes visible by larger, rounder, and notable dendrite-like branching and process extensions. Type 1 collagen alpha 1 (COL1A1), fibroblast growth factor 2 (FGF2, bFGF), and transforming growth factor beta 1 (TGF[beta]1) were all up-regulated after 48 hours of exposure to suction. Smooth muscle actin alpha 2 (Acta2, [alpha]-SMA) was up-regulated after 72 hours. Conclusions: Microdeformations produced by the combination of polyurethane foam and suction are associated with increased fibroblast proliferation and up-regulation of gene expressions in fibroblasts.
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    Angiogenesis in Wounds Treated by Microdeformational Wound Therapy
    (Ovid Technologies (Wolters Kluwer Health), 2011) Erba, Paolo; Ogawa, Rei; Ackermann, Maximilian; Adini, Avner; Miele, Lino F.; Dastouri, Pouya; Helm, Douglas; Mentzer, Steven; D’Amato, Robert J.; Murphy, George; Konerding, Moritz A.; Orgill, Dennis
    Background: Mechanical forces play an important role in tissue neovascularization and are a constituent part of modern wound therapies. The mechanisms by which vacuum assisted closure (VAC) modulates wound angiogenesis are still largely unknown. Objective: To investigate how VAC treatment affects wound hypoxia and related profiles of angiogenic factors as well as to identify the anatomical characteristics of the resultant, newly formed vessels. Methods: Wound neovascularization was evaluated by morphometric analysis of CD31-stained wound cross-sections as well as by corrosion casting analysis. Wound hypoxia and mRNA expression of HIF-1α and associated angiogenic factors were evaluated by pimonidazole hydrochloride staining and quantitative reverse transcription-polymerase chain reaction (RT-PCR), respectively. Vascular endothelial growth factor (VEGF) protein levels were determined by western blot analysis. Results: VAC-treated wounds were characterized by the formation of elongated vessels aligned in parallel and consistent with physiologically function, compared to occlusive dressing control wounds that showed formation of tortuous, disoriented vessels. Moreover, VAC-treated wounds displayed a well-oxygenated wound bed, with hypoxia limited to the direct proximity of the VAC-foam interface, where higher VEGF levels were found. By contrast, occlusive dressing control wounds showed generalized hypoxia, with associated accumulation of HIF-1α and related angiogenic factors. Conclusions: The combination of established gradients of hypoxia and VEGF expression along with mechanical forces exerted by VAC therapy was associated with the formation of more physiological blood vessels compared to occlusive dressing control wounds. These morphological changes are likely a necessary condition for better wound healing.
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    Controlled induction of distributed microdeformation in wounded tissue via a microchamber array dressing
    (Wiley-Blackwell, 2010) Kane, Bartholomew J.; Younan, George; Helm, Douglas; Dastouri, Pouya; Prentice-Mott, Harrison; Irimia, Daniel; Chan, Rodney K.; Toner, Mehmet; Orgill, Dennis
    Mechanical stimuli are known to play an important role in determining the structure and function of living cells and tissues. Recent studies have highlighted the role of mechanical signals in mammalian dermal wound healing. However, the biological link between mechanical stimulation of wounded tissue and the subsequent cellular response has not been fully determined. The capacity for researchers to study this link is partially limited by the lack of instrumentation capable of applying controlled mechanical stimuli to wounded tissue. The studies outlined here tested the hypothesis that it was possible to control the magnitude of induced wound tissue deformation using a microfabricated dressing composed of an array of open-faced, hexagonally shaped microchambers rendered in a patch of silicone rubber. By connecting the dressing to a single vacuum source, the underlying wounded tissue was drawn up into each of the microchambers, thereby inducing tissue deformation. For these studies, the dressings were applied to full-thickness murine dermal wounds with 200 mmHg vacuum for 12 h. These studies demonstrated that the dressing was capable of inducing wound tissue deformation with values ranging from 11 to 29%. Through statistical analysis, the magnitude of the induced deformation was shown to be a function of both microchamber height and width. These results demonstrated that the dressing was capable of controlling the amount of deformation imparted in the underlying tissue. By allowing the application of mechanical stimulation with varying intensities, such a dressing will enable the performance of sophisticated mechanobiology studies in dermal wound healing.