(10a) (Invited Talk) Engineered Tissue Microspheres for Regenerative Medicine and Disease Modeling Applications

Dr. Lipke’s research group employs biomimetic materials to guide induced pluripotent stem cell differentiation and maturation, particularly for the scalable production of human heart tissue, to support therapeutic cell delivery, and to create engineered cancer tissues that recapitulate aspects of the tumor microenvironment for use in drug testing. Most recently, we have established a rapid and readily replicable approach to encapsulate cells in poly(ethylene glycol)-fibrinogen (PEG-Fb) microspheres for a range of applications, including stem cell differentiation, cancer tissue engineering, tissue spheroid based drug-testing assays, and injectable therapeutic cell delivery. Using a microfluidic approach, hydrogel microspheres with uniform shape and size can be produced with high (20 million cells/mL) cell densities. To form the microspheres, aqueous PEG-Fb polymer precursor with suspended cells is infused through the upper inlet of a custom microfluidic device and the mineral oil carrier infused through the bottom inlet; microspheres form at the junction and traverse the outlet channel, where they are photocrosslinked in > 1 second and collected.

A range of cell types, including stem and progenitor cells and cancer cells, have been encapsulated with high maintenance of cell viability. By providing a tunable, biomimetic cellular microenvironment, these hydrogel microspheres have been shown to support stem cell proliferation and differentiation, including cardiac differentiation of human induced pluripotent stem cells. The established hydrogel microsphere system also can be employed for encapsulation and delivery of therapeutic cell types; fabricated microspheres supported maintenance of encapsulated endothelial progenitor cell phenotype and outgrowth in vitro and in vivo delivery through injection in an equine wound healing model. Encapsulated cancer cells also remodeled the PEG-Fb and formed dense tissues over time; engineered tumor spheroids were more uniform than spontaneously aggregated cancer cells and could be maintained for multiple weeks in culture for use in drug testing. Overall, rapid and reproducible cell encapsulation in hydrogel microspheres has advantages for use in regenerative medicine and disease modeling applications.