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DDC: 610 × Publisher: Oxford [u.a.] : Wiley-Blackwell × WGL Institute: DWI ×

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    EndOxy: Mid-term stability and shear stress resistance of endothelial cells on PDMS gas exchange membranes
    (Oxford [u.a.] : Wiley-Blackwell, 2020) Hellmann, Ariane; Klein, Sarah; Hesselmann, Felix; Djeljadini, Suzana; Schmitz-Rode, Thomas; Jockenhoevel, Stefan; Cornelissen, Christian G.; Thiebes, Anja Lena
    Endothelialized oxygenator devices (EndOxy) with a physiological, nonthrombogenic, and anti-inflammatory surface offer the potential to overcome current shortcomings of conventional extracorporeal membrane oxygenation such as complications like thromboembolism and bleeding that deteriorate adequate long-term hemocompatibility. The approach of endothelialization of gas exchange membranes, and thus the formation of a nonthrombogenic and anti-inflammatory surface, is promising. In this study, we investigated the mid-term shear stress resistance as well as gas transfer rates and cell densities of endothelial cells seeded on RGD-conjugated polydimethylsiloxane (RGD-PDMS) gas exchange membranes under dynamic conditions. Human umbilical vein endothelial cells were seeded on RGD-PDMS and exposed to defined shear stresses in a microfluidic bioreactor. Endothelial cell morphology was assessed by bright field microscopy and immunocytochemistry. Furthermore, gas transfer measurement of blank, RGD-conjugated, and endothelialized PDMS oxygenator membranes was performed. RGD-PDMS gas exchange membranes proved suitable for the dynamic culture of endothelial cells for up to 21 days at a wall shear stress of 2.9 dyn/cm2. Furthermore, the cells resisted increased wall shear stresses up to 8.6 dyn/cm2 after a previous dynamic preculture of each one hour at 2.9 dyn/cm2 and 5.7 dyn/cm2. Also, after a longer dynamic preculture of three days at 2.9 dyn/cm2 and one hour at 5.7 dyn/cm2, increased wall shear stresses of 8.6 dyn/cm2 were tolerated by the cells and cell integrity could be remained. Gas transfer (GT) tests revealed that neither RGD conjugation nor endothelialization of RGD-PDMS significantly decrease the gas transfer rates of the membranes during short-term trials. Gas transfer rates are stable for at least 72 hours of dynamic cultivation of endothelial cells. Immunocytochemistry showed that the cell layer stained positive for typical endothelial cell markers CD31 and von Willebrand factor (VWF) after all trials. Cell density of EC on RGD-PDMS increased between 3 and 21 days of dynamic culture. In this study, we show the suitability of RGD-PDMS membranes for flow resistant endothelialization of gas-permeable membranes, demonstrating the feasibility of this approach for a biohybrid lung. © 2020 The Authors. Artificial Organs published by International Center for Artificial Organ and Transplantation (ICAOT) and Wiley Periodicals LLC
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    The more the merrier: effects of macromolecular crowding on the structure and dynamics of biological membranes
    (Oxford [u.a.] : Wiley-Blackwell, 2020) Löwe, Maryna; Kalacheva, Milara; Boersma, Arnold J.; Kedrov, Alexej
    Proteins are essential and abundant components of cellular membranes. Being densely packed within the limited surface area, proteins fulfil essential tasks for life, which include transport, signalling and maintenance of cellular homeostasis. The high protein density promotes nonspecific interactions, which affect the dynamics of the membrane-associated processes, but also contribute to higher levels of membrane organization. Here, we provide a comprehensive summary of the most recent findings of diverse effects resulting from high protein densities in both living membranes and reconstituted systems and display why the crowding phenomenon should be considered and assessed when studying cellular pathways. Biochemical, biophysical and computational studies reveal effects of crowding on the translational mobility of proteins and lipids, oligomerization and clustering of integral membrane proteins, and also folding and aggregation of proteins at the lipid membrane interface. The effects of crowding pervade to larger length scales, where interfacial and transmembrane crowding shapes the lipid membrane. Finally, we discuss the design and development of fluorescence-based sensors for macromolecular crowding and the perspectives to use those in application to cellular membranes and suggest some emerging topics in studying crowding at biological interfaces. © 2020 The Authors. The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies