A Miniaturized EHT Platform for Accurate Measurements of Tissue Contractile Properties

Abstract

We present a wafer-scale fabricated, PDMS-based platform for culturing miniaturized engineered heart tissues (EHTs) which allows highly accurate measurements of the contractile properties of these tissues. The design of the platform is an anisometrically downscaled version of the Heart-Dyno system, consisting of two elastic micropillars inside an elliptic microwell with volume ranging from 3 down to 1µL which supports EHT formation. Size downscaling facilitates fabrication of the platform and makes it compatible with accurate and highly reproducible batch wafer-scale processing; furthermore, downscaling reduces the cost of cell cultures and increases assay throughput. After fabrication, the devices were characterized by nanoindentation to assess the mechanical properties of the pillars and transferred to 96-well plates for cell seeding. Regardless the size of the platform, cell seeding resulted in successful formation of EHTs and all tissues were functionally active (i.e. showed cyclic contractions). The precise characterization of the stiffness of the micropillars enabled accurate measurements of the contractile forces exerted by the cardiac tissues through optical tracking of micropillar displacement. The miniature EHT platforms described in this paper represent a proper microenvironment for culturing and studying EHTs.

Current strategies of mechanical stimulation for maturation of cardiac microtissues

“…Of note, to assess the maturation of cardiac models, methods to sense tissue properties have been developed: most systems able to perform a mechanical characterization rely on end-point analysis. However, technological solutions to perform online measurements are gaining interest, and such systems promise to quantify cell contractility changes over time during maturation, either through optical mapping or flexible micropillars (Dostanić et al 2020;Dou et al 2021;van Meer et al 2019). The addition of these new features in static or dynamic stimulation systems, combined with tunable stiffness and topography, is expected to dramatically contribute to achieve reliable cardiac models to study physiological and pathological mechanisms in the near future.…”

Generation, functional analysis and applications of isogenic three-dimensional self-aggregating cardiac microtissues from human pluripotent stem cells

“…Most of the designs are based on specific tissue-engineered formats using methods such as SU-8 photolithography 22,23 , bioprinting 24,25 , decellularization of whole hearts 26 , surface micropatterning [27][28][29] , biowires 23,30 , or casting molds as hydrogel (collagen, Matrigel or fibrinogens) scaffolds 22,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] . Engineered heart tissues (EHTs) are grown on mechanical supports or pillars providing mechanical load and have been described to induce hiPSC-CM maturation 35,37 .…”

“…One system uses forced supraphysiological pacing up to 6 Hz to facilitate this 40 . The initial designs 48 were low-throughput, time-consuming and costly for both academic laboratories and pharma but miniaturized versions have now been made 22,30,34,36,42,45,47 .…”

Engineered models of the human heart: Directions and challenges

“…This affects force analysis, tissue pre-load, tissue formation, cellular behavior, and variability in inter-hiPSC-line comparisons when experiments are performed at different times. Dostanic and colleagues have further miniaturized the standing pillar design and performed extensive mechanical characterization of the pillars ( Dostanic et al., 2020 ).…”