Discussion

iPS-derived cells, primary cells and even immortal cell lines grown in standard monolayer culture conditions are valuable tools for drug discovery and drug safety. However, the selection and detection of active compounds based on such in vitro models has so far been of limited value, due to poor in vivo translatability. Two major limitations could explain this phenomenon. First, monolayer cells do not reflect properly native tissue physiology and second, available relevant readouts are limited. Consequently, there is increasing awareness that the development of cellular models with higher physiological relevance coupled to more informative readouts are prerequisite to improving cell-based assays.
In this context, we have developed several multi-cellular models fully compatible with High Content Analysis combining physiological relevance with throughput. Cellular systems considered to be the most physiologically similar to in vivo cells were used, namely iPS-derived cardiomyocytes (CDI Inc.), primary human skeletal muscle cells (Lonza) and native human tumor cell lines. We then compared the physiology of micropatterned cells with the same cells grown as conventional cultures in 96 well plate format.
Several key cellular features of cardiac and skeletal muscle indicating achievement of higher maturation levels (increased striation, increased level of connexin43 expression, highly organized sarcomeres) were observed in the cells grown on micropatterns and absent or rare in the same cells grown as monolayer cultures. The apparent resuscitation and/or stabilization of cellular function by micropatterns allow implementation of innovative readouts that are more relevant to the physiology of the systems, using imaging and High Content Analysis. Furthermore, the micropatterned tissue models consist of multiple homogeneous uniform structures per well, facilitating segmentation and identification of features such as width of myotubes for higher throughput automated image analysis.
This work suggests that control of cell adhesion and cell-cell interactions promotes multi-cellular self-organization and enhances overall function, opening up access to novel cellular readouts. Micropatterns offer an opportunity to improve upon conventional cultures of several cellular models, even for cells that are the closest representatives of in vivo functionalities, further upgrading their usefulness for screening and mechanistic investigation of candidate drugs.