Microchannel Platform for the Study of Endothelial Cell Shape and Function

Abstract

Microfabrication technology is implemented to realize a versatile platform for the study of endothelial cell (EC) shape and function. The platform contains arrays of microchannels, 25–225 μm wide, that are fabricated by deep reactive ion etching (DRIE) of silicon and anodic bonding to glass and within which ECs are cultured. Silicon fluidic port modules, fabricated using a combination of silicon fusion bonding and anisotropic etching in KOH, provide a simple and reversible means of coupling, via standard tubing, between an individual microchannel and off-platform devices for flow monitoring and control. For flow experiments where a well-defined flow field is required, the channels are capped with either a glass lid or a thin, self-sealing elastomer membrane that can be punctured to provide direct access to cells within the microchannels. Under static culture conditions, bovine aortic ECs (BAECs) become progressively more elongated as the channel width decreases. The shape index, a dimensionless measure of cell roundness, decreases from 0.75±0.01 (mean±SEM) for BAECs cultured in 225 μm-wide microchannels to 0.31±0.02 in 25 μm-wide channels. When cuboidal BAECs are grown in 200 μm-wide microchannels and then subjected to a fluid shear stress of approximately 20 dyne/cm2 (2 Pa), they progressively elongate and align in the direction of flow in a similar manner to cells cultured on plain surfaces. To demonstrate the utility of the microfabricated platform for studying aspects of EC function, whole-cell patch-clamp recordings were performed under static conditions in open microchannels. The platform is demonstrated to be a versatile tool for studying relationships between EC shape and function and for probing the effect of flow on ECs of different shapes. Specific future applications and extensions of platform function are discussed.