(176c) Incorporation of Hydrolytically Degradable Poly(lactic acid) in a 3D PEG Hydrogel Guides Oligodendrocyte Precursor Cell Intracellular Redox State | AIChE

(176c) Incorporation of Hydrolytically Degradable Poly(lactic acid) in a 3D PEG Hydrogel Guides Oligodendrocyte Precursor Cell Intracellular Redox State

Authors 

Russell, L. - Presenter, University of Virginia
Lampe, K., University of Virginia
The intracellular redox state is indicative of a cell’s proliferation and differentiation capabilities as well as the cell’s ability to build and maintain cellular structures. In the central nervous system, this could correlate to an oligodendrocyte’s ability to generate segments of the myelin sheath, the electrically insulating layer around neuronal axons. This myelin sheath enables neurons to send quick and efficient electrical signals to surrounding neurons, and is the main tissue component that is damaged in demyelinating diseases like multiple sclerosis. Additionally as a result of insults from demyelinating diseases like multiple sclerosis, the myelin sheath often fails to regenerate between relapses, compounding the patient’s symptoms with each insult. Biomaterials can be used as a tissue engineering tool to mimic native healthy or diseased tissue in vitro, however little is known about what biomaterial factors stimulate functional regrowth and subsequent remyelination of oligodendrocytes from their parent cells: oligodendrocyte precursor cells.

Here we investigate how tuning the biomaterial properties and degradability of a poly(ethylene glycol)-based hydrogel affects the intracellular redox state and myelin production of an oligodendrocyte precursor cell line. Nondegradable PEG-dimethacrylate hydrogels with storage moduli from 230-1900 Pa were formed by tuning the concentration and molecular weight from 6 to 10% and 4600 to 8000 Da, respectively. When poly(lactic acid) is built into the PEG backbone, lactic acid, a weak antioxidant and metabolite, is slowly released as the hydrogel crosslinks hydrolytically degrade. Hydrogels with polylactic acid can be engineered to degrade from 7 days to a month and release varying lactic acid amounts. In compliant, nondegradable materials, cells proliferate more and have a more reduced intracellular redox state. The intracellular redox state can be measured through a simple assay kit which measures amounts of glutathione in the reduced, GSH, and oxidized GSSG form. After 1 day in 3D culture, cells in the compliant nondegradable hydrogel had a 40% increase in reduced glutathione compared to the stiffer material, and a 60% increase at 7 days. Incorporating soluble lactic acid in nondegradable hydrogels or releasing lactic acid from degradable hydrogels both increased the ratio of glutathione in the reduced form; 5μmol/mL of soluble lactic acid reduced the intracellular redox state by 40%. Mitotracker Orange staining of the mitochondrial intracellular redox state further confirmed redox state differences in response to the lactic acid concentration. In addition to differences in redox state, cells encapsulated in degradable materials were found to extend more processes, morphologically similar to the processes oligodendrocyte precursor cells extend in vivo to generate the myelin sheath. These results together suggest the potential use of an engineered PEG hydrogel environment to guide the intracellular redox state and therefor promote oligodendrocyte precursor cell maturation and myelin production.

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