(229h) Chemotaxis-Based Mesenchymal Stem Cell Migration in 2D Microfluidic Maze

Authors: 
Pham, L. Q., New Jersey Institute of Technology NJIT
Voronov, R., New Jersey Institute of Technology NJIT
The migration of cells is an important event that involves in embryonic morphogenesis, wound repair, and cancer invasion. Most migration studies focus on cancer and immune cell, whereas for tissue manufacturing stem-cells are more relevant. Yet, their migratory behavior is studied a lot less in comparison. Part of the reason for this is simply because stem cells are slower, and thus single cell studies require lengthy experiments with live imaging and incubation on the microscope (challenging). Another reason is that tissue engineering studies are frequently done by seeding cells on 3D scaffolds, in which real-time non-invasive observation is not possible. As a result, most of the analysis is done by performing bulk differentiation and proliferation assays on crushed samples (i.e., a single time point at the end of the experiment. Therefore here we utilize the most advanced aspects of cell cancer/immune migration studies and apply them specifically to mesenchymal stem cells (MSCs) - the most prominent cell type used tissue engineering. The few MSC migration studies we have found, so far have not considered heterogeneous-yet-well-defined chemoattractant gradient profile (the drivers of migration that the cells usually encounter in vivo). Hereby we endeavor to explore the long-term migration of MSCs in 2D microfluidic maze platforms which represent the complexity of the tissue geometry in vivo with long paths, short paths, and dead ends in which a multitude of cell directional decisions are possible through different chemical gradient scenarios. The migration of MSCs is chemotactically induced by diffusion-based concentration gradients of platelet-derived growth factor-BB (PDGF-BB) and fetal bovine serum (FBS). The gradients are maintained stable for more than 48 hours by means of slow diffusion of the chemoattractants. The whole cell migration process in the microfluidic device is monitored and imaged in real time using an inverted microscope (IX83, Olympus) installed with a custom culturing chamber. The stability of the chemical gradient is tracked by fluorescent 20 kDa Dextran-FITC while the initial concentration gradient of PDGF-BB and FBS is computationally predicted by COMSOL modeling basing on their molecular weights. Migratory cell decisions are quantified in terms of percentage of cells migrating across long path, or short path, or being trapped in dead ends. Different maze dimensions as well as various chemotactic profiles affecting the migration of cells are also investigated. For instance channel size must be large enough for the cell to be able to pass through, while small enough for it to be able to grab onto the walls; while at the same time, the chemoattractant gradient steepness is also affected by the maze geometry. The ultimate end-product of our work is a microfluidics platform custom-tailored to migration studies relevant to tissue engineering-like systems.