Application of Organ-on-chips and micro-physiological systems
Stem cell technology holds great promise for mitigating the cost of drug development by properly modeling human biology in vitro. Assays based on these technologies have the potential to be more predictive of toxicity and efficacy when compared to simpler single molecule assays. Building these representative organ-on-chip models relies on generating hierarchically organized cells and tissues. In vivo, this organization is driven by a complex interplay of cells and their environment, including the extracellular matrix (ECM). Traditional cell culture environments—typically composed of hard and unstructured glass or plastic— fail to fulfill the role of the ECM in development. Consequently, many in vitro stem cell models often fall short in correctly reproducing critical in vivo phenotypes because cultured cells oftentimes lose type-specific characteristics or express phenotypes indicative of an immature developmental stage. Considerable effort is directed at fabricating biomimetic culture environments that maintain or promote mature phenotypes. However, making biomimetic substrates typically involves costly or hard-to-reproduce techniques that are often incompatible with many standard assays; these challenges are compounded when using high-throughput techniques. Our objective is to develop novel surfaces that mimic the mechanical and structural cues of the ECM without compromising compatibility with state-of-the-art assays and instruments. The fabrication scheme is based on high-precision photolithography techniques, and is thus highly reproducible, scalable, and amenable to integration with most industry-standard endpoint assays, including high-NA microscopy. Further, the approach is centered on SLAS/ANSI/SBS-compliant formats which are compatible with high-throughput automated platforms. Our data demonstrate that various cell types are amenable to this approach. hiPSC-derived cardiomyocytes (CMs) showed in vivo-like myofibril alignment, sarcomere spacing and width, and expression of CM-specific proteins that are present in mature myocytes. Higher-ordered 2D anisotropic myocyte tissues also showed adult-like structure and electrophysiological responses to drugs in vitro when compared to traditional unordered 2D isotropic constructs. Examples of phenotype enhancement of other adherent mammalian cell types will be presented, further demonstrating the utility of the approach for generating more representative cells and tissues. Finally, we extend this technique to pattern the surface of micro-electrode arrays, and demonstrate that these ECM-based cues enhance the electrophysiological response of cardiomyocytes to various drugs of known action. We conclude that our approach is a viable method for re-creating specific aspects of the ECM that are critical for driving the development and maturation of stem cells in culture.