High-Throughput Measurements of Hydrogel Tissue Construct Mechanics

Abstract

Engineered tissues represent a natural environment for studying cell physiology, mechanics, and function. Cellular interactions with the extracellular matrix proteins are important determinants of cell physiology and tissue mechanics. Dysregulation of these parameters can result in diseases such as cardiac fibrosis and atherosclerosis. In this report we present a novel system to produce hydrogel tissue constructs (HTCs) and to characterize their mechanical properties. HTCs are grown in custom chambers and a robotic system is used to indent them and measure the resulting forces. Force measurements are then used to estimate HTC pretension (cellular contractility). Pretension was reduced in a dose-dependent manner by cytochalasin D (CD) treatment; the highest concentration (2 μM) resulted in ~10-fold decrease. On the other hand, treatment with fetal bovine serum (20%) resulted in approximately threefold increase in pretension. Excellent repeatability and precision were observed in measurements from replicate HTCs. The coefficient of statistical variance of quantified pretension ranged from 7% to 15% (n = 4). Due to the small size (4×4×0.8 mm) of the HTCs, this system of profiling HTC mechanics can readily be used in high-throughput applications. In particular, it can be used for screening chemical libraries in search of drugs that can alter tissue mechanics.

Passive and active contributions to generated force and retraction in heart valve tissue engineering

“…In literature, the reported active and passive cellular contributions to generated force are much higher. The active cellular contribution to force of fibroblasts in collagen gels was 35-65% (Marquez et al 2009;Youssef et al 2011;John et al 2010;Legant et al 2009) and lysation caused an additional 30% reduction of force below the level observed with CytoD treatment (Wakatsuki et al 2000). To measure a decrease in force within our model system, bending of the leaf springs must become less and this requires elongation of the TE constructs.…”

“…Active and passive phenomena have been investigated thoroughly in short-term studies with fibroblast-populated collagen and fibrin gel systems Marquez et al 2009;John et al 2010;Youssef et al 2011;Tomasek et al 1992;Grouf et al 2007;Balestrini and Billiar 2009). In tissue engineered heart valves, the ECM is developed during 4 weeks of tissue culture and is more mature than the generally investigated collagen and fibrin gels.…”

Tissue constructs: platforms for basic research and drug discovery

“…For example, the classical Langendorf preparation of an excised heart undergoes a significant deterioration of function over a few hours [27]. In contrast, cardiac tissue constructs preserve stable contractile function over many days [28]. (7) Applicability to screening.…”

Rapid Prototyping of Engineered Heart Tissues through Miniaturization and Phenotype-Automation

“…However, in these micro-scale tissues, it is yet to be determined if there is an improvement of the statistical significance of functional data over that from single cells. At present, ETs in millimeter scale have been used for the functional assays with relatively good data reproducibility [8] [9]. By using ETs, a statistically significant data can be obtained using only 4-8 samples [9] instead of collecting ranging 60-600 data points per well in cell-based assays [10].…”

“…At present, ETs in millimeter scale have been used for the functional assays with relatively good data reproducibility [8] [9]. By using ETs, a statistically significant data can be obtained using only 4-8 samples [9] instead of collecting ranging 60-600 data points per well in cell-based assays [10]. Unlike the rapid prototyping of parts with synthetic materials, the prototyping of engineered tissues with live cells has to consider the behavior of tissues after fabrication in a given culture condition.…”