Abstract 177: A Novel Vascular "Ring" Assay for Smooth Muscle Contractility Using Magnetic 3-Dimensional Bioprinting

Abstract

The current standard for studying pharmacodynamics on vascular smooth muscle contractility is wire myography with ex vivo tissue, which suffers from high cost low throughput, limiting its widespread use. Yet, in vitro alternatives are insufficient, as they are commonly two-dimensional (2D) monolayers on rigid surfaces unlike the soft vasculature. Thus, a rapid, robust in vitro assay is needed that mimics the native three-dimensional (3D) environment, while yielding high data throughput. Towards that goal, we introduce an 3D in vitro assay in which cellularized vascular "rings" are rapidly and magnetically bioprinted. In the assay, cells are incubated with magnetic nanoparticles to render them magnetic, then printed into 3D rings (1.5 x 10^5 cells/ring) in 96-well plates. The rings will then contract or dilate over a short amount of time (<5 h) in a dose-dependent manner visually similar to vessel contraction and dilation (Fig. 1A). This measurement is label-free, meaning that the rings can be experimented on afterwards to explore pharmacodynamics. Moreover, this assay is captured using an iPod-based imaging system programmed to take images of whole plates (Fig. 1B) instead of imaging individual wells under a microscope. This assay was validated for the evaluation of drug efficacy by measuring contractility in 3D bioprinted rings of A10 rat vascular smooth muscle cells. The compounds tested were either vasodilators (blebbistatin, forskolin, verapamil) or vasoconstrictors (norepinephrine, phenylephrine, U46619). Ring contraction was compared to the presence of phosphorylated myosin light chain-2 which is related to smooth muscle concentration. Furthermore, the gene expression profiles of rings exposed to specific compounds are compared to negative controls. The result of this study is the validation of the vascular assay that rapidly prints 3D environments similar to the native blood vessel, and efficiently measures smooth muscle contraction.