Delivery of cytokines via encapsulated human astrocytes for neural immunomodulation

Modulating neuroinflammation with biomaterial advancements has potential for restoring normative function in a wide variety of neuropathologic conditions. Because astrocytes dynamically react to the microenvironment and contribute to the neuroinflammatory process, they are well situated as initiators and/or targets for biomaterial-based immunomodulation strategies. To achieve this, we devised and validated an alginate hydrogel encapsulation approach using human pluripotent stem cell-derived astrocytes that enabled a novel coculture system with organoids composed of neurons, astrocytes, and microglia. Encapsulated human astrocytes were able to secrete proteins to the external environment and become reactive in response to stimuli. When engineered to express the clinically relevant cytokine interleukin-1 receptor antagonist (IL-1Ra), astrocytes reduced organoid reactivity to inflammatory cytokines in both direct and indirect co-cultures. Furthermore, astrocytes engineered for regulated cytokine production through NFκB-mediated expression of an internal reporter (luciferase) or IL-1Ra demonstrated dose-dependent responsive behavior to a panel of stimuli. Encapsulated astrocytes were also able to be stably implanted into the rodent brain while secreting IL-1Ra. Altogether, these studies clarify human astrocyte inflammatory reactivity, deliver a novel coculture platform to test neuroinflammatory modulators in vitro, and demonstrate an implantation approach to provide astrocyte-derived proteins to the nervous system in vivo.