Mucociliary flow is an important defense mechanism in the lung to remove inhaled pathogens and pollutants. A disruption of ciliary flow can lead to respiratory infections. Even though patients in the intensive care unit (ICU) either have or are very susceptible to respiratory infections, mucociliary flow is not well understood in the ICU setting. We recently demonstrated that hyperoxia, a consequence of administering supplemental oxygen to a patient in respiratory failure, can lead to a significant reduction of cilia-driven fluid flow in mouse trachea. There are other factors that are relevant to ICU medicine that can damage the ciliated tracheal epithelium, including inhalation injury and endotracheal tube placement. In this study we use two animal models, Xenopus embryo and ex vivo mouse trachea, to analyze flow defects in the injured ciliated epithelium. Injury is generated either mechanically with a scalpel or chemically by calcium chloride (CaCl2) shock, which efficiently but reversibly deciliates the embryo skin. In this study we used optical coherence tomography (OCT) and particle tracking velocimetry (PTV) to quantify cilia driven fluid flow over the surface of the Xenopus embryo. We additionally visualized damage to the ciliated epithelium by capturing 3D speckle variance images that highlight beating cilia. Mechanical injury disrupted cilia-driven fluid flow over the injured site, which led to a reduction in cilia-driven fluid flow over the whole surface of the embryo (n=7). The calcium chloride shock protocol proved to be highly effective in deciliating embryos (n=6). 3D speckle variance images visualized a loss of cilia and cilia-driven flow was halted immediately after application. We also applied CaCl2-shock to cultured ex vivo mouse trachea (n=8) and found, similarly to effects in Xenopus embryo, an extensive loss of cilia with resulting cessation of flow. We investigated the regeneration of the ciliated epithelium after an 8 day incubation period, and found that cilia had regrown and flow was completely restored. In conclusion, OCT is a valuable tool to visualize injury of the ciliated epithelium and to quantify reduction of generated flow. This method allows for systematic investigation of focal and diffuse injury of the ciliated epithelium and the assessment of mechanisms to compensate for loss of flow.
Ute A. Gamm, Brendan K. Huang, Emily K. Mis, Mustafa K. Khokha, and Michael A. Choma, "Quantification and visualization of injury and regeneration to the ciliated epithelium using quantitative flow imaging and speckle variance optical coherence tomography (Conference Presentation)," Proc. SPIE 10041, Optical Techniques in Pulmonary Medicine II, 1004104 (Presented at SPIE BiOS: January 28, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2252405.5370042036001.
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