Apical Actin-myosin Network Regulates the Tight Junction of Polarized Madin-Darby Canine Kidney Cells

The tight junction outlines the apicolateral border of epithelial cells like a belt, sealing the paracellular space when cells form contacts with each other. The permeability and morphology of tight junction are regulated by actomyosin contractility, which has been conventionally thought from the purse-string-like circumferential actomyosin belt along tight junction. Spatially, the tight junction is close to the apical actin network, which exerts inward contractions orthogonal to the tight junction. To test the contributions from apical actin network, we laser-ablated spots on the apical surface of polarized Madin-Darby Canine Kidney (MDCK) epithelial cells. Laser ablation severed the apical cytoskeleton network, decreased in-plane tension, increased the apical surface area, and rendered the tight junction less tortuous in shape. Consistent with these observations, changes in MDCK cell sheet morphology due to cell proliferation, or perturbation with the ROCK inhibitor Y27632 increased the density of the apical actin network and decreased tight junction tortuosity. The morphological analysis revealed scutoids in flat MDCK cell sheets, contrary to predictions from a previous model that only considered cell-cell interactions as line tension. Additional cell-cell interactions from apical in-plane tension provides probable cause for the occurrence of scutoids on flat geometry. Taken together, our findings identify the importance of the apical actin network exerting in-plane apical tension to regulate tight-junction mechanobiology and epithelial cell shape.

IN VITRO ANTI-VIRAL ACTIVITY OF HEXETIDINE (BACTIDOL®) ORAL MOUTHWASH AGAINST HUMAN CORONAVIRUS OC43 AND INFLUENZA A (H1N1) VIRUS

ABSTRACTMouthwashes are used to decrease oral cavity microbial load due to their antiseptic properties. Hexetidine is a broad-spectrum antiseptic used for minor infections of mucous membranes, and in particular as a 0.1% mouthwash for local infections and oral hygiene.This study determined the anti-viral activity of the mouthwash hexetidine (Bactidol®), specifically in reducing viral concentration of Human Coronavirus OC43 (HCoV OC43; ATCC® VR-1558™) and Influenza A virus (IAV H1N1; clinical strain) in Vero 6 and MDCK cell cultures respectively, using in-vitro suspension assay (ASTM E-1052-11) designed to evaluate virucidal property of microbicides like hexetidine.Study results indicated that hexetidine was able to reduce infectivity of HCoV OC43 and IAV H1N1 at 25%, 50% and 100% concentrations by more than 80% at 15- and 30-seconds exposure times. One hundred percent (100%) concentration of hexetidine was found to be cytotoxic to MDCK cell line used for IAV H1N1 propagation. Hexetidine-treated cell lines achieved >80% survival rate for MDCK and Vero E6 at a contact time of 15 seconds and 30 seconds (which are the approximate times of gargling with hexetidine mouthwash).The anti-viral activity of hexetidine mouthwash against other more virulent or pathogenic coronaviruses like SARS-CoV-2 can be explored further.

Quantitative proteomic analysis of MDCK cell adhesion

Establishing a stable MDCK suspension cell line by genetic engineering has significant potential to aid industrialization of vaccine production. In this study, quantitative proteomics was used to explore adhesion proteins in MDCK cells.

Highly efficient production of an influenza H9N2 vaccine using MDCK suspension cells

The use of H9N2 subtype avian influenza vaccines is an effective approach for the control of the virus spread among the poultry and for the upgrading of vaccine manufacturing cell culture-based production platform could overcome the limitations of conventional egg-based platform and alternate it. The development of serum-free suspension cell culture could allow even higher virus productivity, where a suspension cell line with good performance and proper culture strategies are required. In this work, an adherent Mardin-Darby canine kidney (MDCK) cell line was adapted to suspension growth to cell concentration up to 12 × 106 cells/mL in a serum-free medium in batch cultures. Subsequently, the H9N2 influenza virus propagation in this MDCK cell line was evaluated with the optimization of infection conditions in terms of MOI and cell concentration for infection. Furthermore, various feed strategies were tested in the infection phase for improved virus titer and a maximum hemagglutinin titer of 13 log2 (HAU/50 μL) was obtained using the 1:2 medium dilution strategy. The evaluation of MDCK cell growth and H9N2 virus production in bioreactors with optimized operating conditions showed comparable cell performance and virus yield compared to shake flasks, with a high cell-specific virus yield above 13000 virions/cell. With the purified H9N2 virus harvested from the bioreactors, the MDCK cell-derived vaccine was able to induce high titers of neutralizing antibodies in chickens. Overall, the results demonstrate the promising application of the highly efficient MDCK cell-based production platform for the avian influenza vaccine manufacturing.