(574h) 3D Written Hydrogel Microfiber Mat Regulation of Cell Metabolism for Tissue Engineering

Tissue or organ generation has long been one of the core tasks in biomedical engineering and rehabilitation research. It could be done both in vitro and in vivo. Compared to most in vitro lab culturing, in vivo tissue production provides growth environment of real destination and shows several unique advantages such as complete supply of needed growth factors and/or stimuli and convenience for auto-vascularization. However, in vivo tissue generation require active regulation of the cell metabolism (cell cycle, proliferation, oxygen and glucose consumption, and so on). This is particular true when two or more types of cells must be co-culturing during tissue generation, in which synchronic proliferation is critical. Common approaches to prevent over growth of some types of cells lie on the treatment of irradiation or mitomycine C, which mainly limited for in vitro tissue culturing. By encapsulating fibroblast cells in spherical alginate beads, Hunt et al successfully demonstrated reversible metabolic control of cells, contributed by suppression of cell-cell interactions. One common issue associated with cell culturing in microcapsules lies on the heterogeneous distribution of oxygen, nutrients and toxic metabolic products in the radial direction. Necrotic tissues are often seen in microcapsules due to the mass transport limitation for their millimeter size. Reducing size is often not an option for the requirement of a relative large number of cells to meet minimum cell density in these applications. Microfiber format constructs have been recently developed to enhance the radial mass transport in cell culturing. Most of them liquefied the core to create many small three-dimensional “bioreactors”, similar to early microcapsule research. We here explore the feasibility of using microfiber hydrogels encapsulated with cells for better regulation of cell metabolism. Specifically, fibroblast cells (i.e., NIH 3T3 cells) and mouse embryonic stem cells (mES) were encapsulated in alginate microfibers as randomly constructed fiber nest. The individual alginate fibers have a diameter of 100-300 micrometer in diameter to reduce the radial diffusion distance while their decimeter- or longer length ensures sufficient cells are encapsulated. The void space in fiber nests further help fast inter-fiber mass transport of oxygen, nutrients and metabolic products. We systemically studied the cell viability, proliferation, short-period metabolism, and gene expression capability during and after encapsulation of various periods. For mES cells, we also evaluated the retaining of their self-renewal with Oct-4 assay.