title: Alginate encapsulation parameters influence the differentiation of microencapsulated embryonic stem cell aggregates.
abstract: Pluripotent embryonic stem cells (ESCs) have tremendous potential as tools for regenerative medicine and drug discovery, yet the lack of processes to manufacture viable and homogenous cell populations of sufficient numbers limits the clinical translation of current and future cell therapies. Microencapsulation of ESCs within microbeads can shield cells from hydrodynamic shear forces found in bioreactor environments while allowing for sufficient diffusion of nutrients and oxygen through the encapsulation material. Despite initial studies examining alginate microbeads as a platform for stem cell expansion and directed differentiation, the impact of alginate encapsulation parameters on stem cell phenotype has not been thoroughly investigated. Therefore, the objective of this study was to systematically examine the effects of varying alginate compositions on microencapsulated ESC expansion and phenotype. Pre-formed aggregates of murine ESCs were encapsulated in alginate microbeads composed of a high or low ratio of guluronic to mannuronic acid residues (High G and High M, respectively), with and without a poly-L-lysine (PLL) coating, thereby providing four distinct alginate bead compositions for analysis. Encapsulation in all alginate compositions was found to delay differentiation, with encapsulation within High G alginate yielding the least differentiated cell population. The addition of a PLL coating to the High G alginate prevented cell escape from beads for up to 14 days. Furthermore, encapsulation within High M alginate promoted differentiation toward a primitive endoderm phenotype. Taken together, the findings of this study suggest that distinct ESC expansion capacities and differentiation trajectories emerge depending on the alginate composition employed, indicating that encapsulation material physical properties can be used to control stem cell fate.
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Jenna L
authors.initials: JL
authors.lastname: Wilson
authors.forename: Mohamad Ali
authors.initials: MA
authors.lastname: Najia
authors.forename: Rabbia
authors.initials: R
authors.lastname: Saeed
authors.forename: Todd C
authors.initials: TC
authors.lastname: McDevitt
mesh_terms: D000464:Alginates / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods; D002454:Cell Differentiation; D018914:Cells, Immobilized / Q000502:physiology*; D053595:Embryonic Stem Cells / Q000502:physiology*; D020723:Glucuronic Acid / Q000737:chemistry / Q000378:metabolism; D006603:Hexuronic Acids / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008863:Microspheres; D011107:Polylysine / Q000032:analysis
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; C007896:guluronic acid; D011107:Polylysine; D020723:Glucuronic Acid; C008324:mannuronic acid
keywords: alginate; bioprocessing; microencapsulation; stem cells