Controlled microenvironments to evaluate chemotactic properties of cultured Müller glia.

Emerging therapies have begun to evaluate the abilities of Müller glial cells (MGCs) to protect and/or regenerate neurons following retina injury. The migration of donor cells is central to many reparative strategies, where cells must achieve appropriate positioning to facilitate localized repair. Although chemical cues have been implicated in the MGC migratory responses of numerous retinopathies, MGC-based therapies have yet to explore the extent to which external biochemical stimuli can direct MGC behavior. The current study uses a microfluidics-based assay to evaluate the migration of cultured rMC-1 cells (as model MGC) in response to quantitatively-controlled microenvironments of signaling factors implicated in retinal regeneration: basic Fibroblast Growth factor (bFGF or FGF2); Fibroblast Growth factor 8 (FGF8); Vascular Endothelial Growth Factor (VEGF); and Epidermal Growth Factor (EGF). Findings indicate that rMC-1 cells exhibited minimal motility in response to FGF2, FGF8 and VEGF, but highly-directional migration in response to EGF. Further, the responses were blocked by inhibitors of EGF-R and of the MAPK signaling pathway. Significantly, microfluidics data demonstrate that changes in the EGF gradient (i.e. change in EGF concentration over distance) resulted in the directional chemotactic migration of the cells. By contrast, small increases in EGF concentration, alone, resulted in non-directional cell motility, or chemokinesis. This microfluidics-enhanced approach, incorporating the ability both to modulate and asses the responses of motile donor cells to a range of potential chemotactic stimuli, can be applied to potential donor cell populations obtained directly from human specimens, and readily expanded to incorporate drug-eluting biomaterials and combinations of desired ligands.

A Magnetically Responsive Biomaterial System for Flexibly Regulating the Duration between Pro- and Anti-Inflammatory Cytokine Deliveries.

While inflammation can be problematic, it is nonetheless necessary for proper tissue regeneration. However, it remains unclear how the magnitude and duration of the inflammatory response impacts regenerative outcome. This is partially due to the difficulty in temporally regulating macrophage phenotype at wound sites. Here, a magnetically responsive biomaterial system potentially capable of temporally regulating macrophage phenotypes through sequential, on-demand cytokine deliveries is presented. This material system is designed to (i) rapidly recruit proinflammatory macrophages (M1) through initial cytokine deliveries and (ii) subsequently transition macrophages toward anti-inflammatory phenotypes (M2s) through delayed, magnetically triggered cytokine release. Here, the ability of this system to initially deliver proinflammatory cytokines (i.e., monocyte chemoattractant protein-1 and interferon gamma), recruit, and harbor an expanding macrophage population, and delay deliveries of anti-inflammatory cytokines (i.e., IL-4 and IL-10) until the application of magnetic fields from simple hand-held magnets is demonstrated. Critically, the timing and rate of these delayed deliveries can be remotely/magnetically controlled. This biomaterial system can provide a powerful tool in (i) understanding the relationship between inflammation and regenerative outcome, (ii) developing optimized cytokine delivery strategies, and (iii) clinically implementing those optimized delivery strategies with the on-demand versatility needed to alter the course of therapies in real time.