Ion Conductance-Based Perfusability Assay of Vascular Vessel Models in Microfluidic Devices

Abstract

We present a novel methodology based on ion conductance to evaluate the perfusability of vascular vessels in microfluidic devices without microscopic imaging. The devices consisted of five channels, with the center channel filled with fibrin/collagen gel containing human umbilical vein endothelial cells (HUVECs). Fibroblasts were cultured in the other channels to improve the vascular network formation. To form vessel structures bridging the center channel, HUVEC monolayers were prepared on both side walls of the gel. During the culture, the HUVECs migrated from the monolayer and connected to the HUVECs in the gel, and vascular vessels formed, resulting in successful perfusion between the channels after culturing for 3–5 d. To evaluate perfusion without microscopic imaging, Ag/AgCl wires were inserted into the channels, and ion currents were obtained to measure the ion conductance between the channels separated by the HUVEC monolayers. As the HUVEC monolayers blocked the ion current flow, the ion currents were low before vessel formation. In contrast, ion currents increased after vessel formation because of creation of ion current paths. Thus, the observed ion currents were correlated with the perfusability of the vessels, indicating that they can be used as indicators of perfusion during vessel formation in microfluidic devices. The developed methodology will be used for drug screening using organs-on-a-chip containing vascular vessels.

A Robust Method for Perfusable Microvascular Network Formation In Vitro

“…[ 34–37 ] In others, in which the microcirculation self assembles from cells (often ECs and FBs), small‐diameter vessels are possible, but even in this case, it is rare to find capillary‐sized structures. [ 3,5,8,9,13–30 ] A common reason for this is the need to generate perfusable vessels, and MVNs with larger diameters are more likely to be perfusable. In contrast, narrow, capillary‐like vessels are less likely to be perfusable because they fail to open at the interface to the media channel.…”

“…Ensuring perfusability may explain that many published reports show perfusable MVNs with both capillary‐like vessels and much larger vessels (Figure S1, Supporting Information). [ 3,5,8,9,13–30 ] To reliably form perfusable MVNs with the desired capillary‐like geometry, we investigated the effect of seeding parameters on MVN geometry and, in doing so, established a robust two‐step seeding strategy that allows us to provide favorable conditions for open vessels between microposts and capillary‐like MVNs throughout the central region.…”