In pulmonary ciliary physiology, most tissue-level measures of performance focus on flow velocity. However, as with the heart, fluid transport performance requires an understanding of force and power generation under various loading conditions. Here, we present our initial work in quantifying shearing force and net power dissipation from OCT-based cilia-driven fluid flow velocimetry. Typical measurements of force require invasive contact with the ciliated surface, while measurements of power rely on metabolic consumption that reflect energy consumption not just from cilia, but from the entirety of cellular processes. We will present two different approaches to non-contact, all-optical shear force and power dissipation physiology. First, we developed a lumped-parameter model of flow driven by a ciliated surface. The lumped-parameter model yields semi-quantitative, Ohm’s law-type relationships (F=U*R and P=U*F) between flow velocity (U), shear force (F), viscous resistance (R), and power dissipation (P). This model allows a lumped (spatially averaged) approach to evaluate force and power performance under viscous loading, an approach we demonstrated using ciliated Xenopus embryos. Second, we numerically estimate shear force and power dissipation using flow velocity fields acquired using OCT. Specifically, the velocity gradient tensor estimated from the flow velocity field contains the required information to estimate both shear force and net power dissipation. We have preliminary data using this numerical approach in Xenopus. Our results support the feasibility of an all-optical approach to estimating mesoscopic measures of force and power in ciliary physiology.
Brendan K. Huang, Mustafa K. Khokha, Michael Loewenberg, and Michael A. Choma, "Towards all-optical quantification of force- and power-based performance metrics in cilia-driven fluid flow physiology (Conference Presentation)," Proc. SPIE 9691, Endoscopic Microscopy XI; and Optical Techniques in Pulmonary Medicine III, 969119 (Presented at SPIE BiOS: February 13, 2016; Published: 27 April 2016); https://doi.org/10.1117/12.2212563.4828146971001.
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