Scientists at the U.S. Food and Drug Administration (FDA) demonstrated unexpected changes in the morphology (shape and size) of multipotent stromal cells (MSCs) when preparations of the cells interact with specific engineered culture systems. The finding is a step toward understanding how to accurately interpret studies that use such systems, called microfluidics platforms, so they can support the development of safe and effective medical products based on multipotent stromal cells.
MSCs can give rise to a variety of tissues (cartilage, bone, or fat) after being stimulated to differentiate by substances called growth factors. The ability of MSCs to differentiate has generated interest among researchers in using them to regenerate tissues and to treat various diseases or medical conditions.
Previously, FDA scientists showed it is possible to predict the behavior of stimulated MSCs by studying changes in their size and shape, using a strategy called “functionally- relevant morphological profiling.” The MSCs were placed in small wells on plastic plates and observed with powerful imaging equipment. Although such small-well studies reflect wide-spread MSC manufacturing techniques, they may not reflect the environment that MSCs encounter in patients. Therefore, there is great interest among researchers in using microfluidics, which may more closely mimic the 3D environment of cells once they are administered to a patient. Also, microfluidics systems enable high-speed, high-sample number imaging of stimulated MSCs.
This particular microfluidics system has a widely used format consisting of tiny channels constructed using silicon-based soft plastic, called polydimethylsiloxane (PDMS), bonded to a polystyrene (PS) surface, within which minute solutions containing MSCs can be injected. The MSCs placed in the channels are cultured on a PS surface and analyzed with high-throughput imaging techniques. Before adding a drop of solution containing stimulated MSCs, researchers commonly sterilize the engineered microfluidic platforms by exposing it to ultraviolet (UV) light. Surprisingly, the FDA scientists found that UV-treated platforms change the way they interact with drops of solution due to alterations in substrate properties, including flattening the drop on the surface, and lead to changes in the shape of the cells. This unintended consequence of UV sterilization, which was not immediately apparent when evaluated using standard small-well cell culture plates, could produce different conclusions about the biology of MSCs. The scientists studied whether additional parameters such as the physical scale of the cell culture microenvironment, type of polystyrene used (bacteriological grade PS substrates and tissue culture-treated PS substrates), as well as the density of the cells within the drops interplayed to influence their cell-material interactions.
The FDA findings are important because scientists need to understand interactions between cells and materials used in microfluidic systems. These findings will in turn enable rigorous and meaningful microfluidics system data to be used by both industry and FDA in facilitating development of MSC analysis and manufacturing using microfluidics.
Adaptation of a Simple Microfluidic Platform for High-Dimensional Quantitative Morphological Analysis of Human Mesenchymal Stromal Cells on Polystyrene-Based Substrates
SLAS Technology (2017) Vol. 22(6) 646-661
Johnny Lam1, Ross A. Marklein1, Jose A. Jimenez-Torres2, David J. Beebe2,Steven R. Bauer1, and Kyung E. Sung1 1Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
2Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA
Corresponding Author: Kyung E. Sung, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Ave., WO 52/72-3206, Silver Spring, MD 20993, USA.