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Retinal pathologies have been heavily studied in response to radiation and microgravity, including spaceflight-associated neuro-ocular syndrome (SANS), which is commonly developed in space flight. SANS has been characterized in clinical studies of astronauts returning to Earth and includes a range of symptoms, such as globe flattening, optic-disc edema, retinal folds, and retinal ischemia. In cases of retinal insult, Müller glia (MG) cells respond via neuroprotective gliotic responses that may become destructive to produce glial scarring and vison loss over time. Retinal pathology is further impacted by the production of excessive reactive oxygen species (ROS) that stimulate retinal inflammation and furthers the gliosis of MG. Neuroprotectants derived from natural products (NPs) able to scavenge excess ROS and mitigate long-term, gliotic responses have garnered recent interest, especially among mature and aging adults. The natural antioxidants aloin and ginkgolide A flavonoids, derived from Aloe vera and Ginkgo biloba species, respectively, have been of particular interest due to their recent use in other nervous-system studies. The current study examined MG behaviors in response to different doses of aloin and ginkgolide A over time by measuring changes in morphology, survival, and ROS production within microscale assays. The study was further enhanced by using galactic cosmic rays (GCR) at the Brookhaven NASA Space Radiation Laboratory to simulate ionizing radiation in low- and high-radiation parameters. Changes in the survival and ROS production of radiation-treated MG were then measured in response to varying dosage of NPs. Our study used in vitro systems to evaluate the potential of NPs to reduce oxidative stress in the retina, highlighting the underexplored interplay between NP antioxidants and MG endogenous responses both in space and terrestrially. 

Millions of adults are affected by progressive vision loss worldwide. The rising incidence of retinal diseases can be attributed to damage or degeneration of neurons that convert light into electrical signals for vision. Contemporary cell replacement therapies have transplanted stem and progenitor-like cells (SCs) into adult retinal tissue to replace damaged neurons and restore the visual neural network. However, the inability of SCs to migrate to targeted areas remains a fundamental challenge. Current bioengineering projects aim to integrate microfluidic technologies with organotypic cultures to examine SC behaviors within biomimetic environments. The application of neural phantoms, or eye facsimiles, in such systems will greatly aid the study of SC migratory behaviors in 3D. This project developed a bioengineering system, called the μ-Eye, to stimulate and examine the migration of retinal SCs within eye facsimiles using external chemical and electrical stimuli. Results illustrate that the imposed fields stimulated large, directional SC migration into eye facsimiles, and that electro-chemotactic stimuli produced significantly larger increases in cell migration than the individual stimuli combined. These findings highlight the significance of microfluidic systems in the development of approaches that apply external fields for neural repair and promote migration-targeted strategies for retinal cell replacement therapy. 

Bioengineering systems have transformed scientific knowledge of cellular behaviors in the nervous system (NS) and pioneered innovative, regenerative therapies to treat adult neural disorders. Microscale systems with characteristic lengths of single to hundreds of microns have examined the development and specialized behaviors of numerous neuromuscular and neurosensory components of the NS. The visual system is comprised of the eye sensory organ and its connecting pathways to the visual cortex. Significant vision loss arises from dysfunction in the retina, the photosensitive tissue at the eye posterior that achieves phototransduction of light to form images in the brain. Retinal regenerative medicine has embraced microfluidic technologies to manipulate stem-like cells for transplantation therapies, where de/differentiated cells are introduced within adult tissue to replace dysfunctional or damaged neurons. Microfluidic systems coupled with stem cell biology and biomaterials have produced exciting advances to restore vision. The current article reviews contemporary microfluidic technologies and microfluidics-enhanced bioassays, developed to interrogate cellular responses to adult retinal cues. The focus is on applications of microfluidics and microscale assays within mammalian sensory retina, or neuro retina, comprised of five types of retinal neurons (photoreceptors, horizontal, bipolar, amacrine, retinal ganglion) and one neuroglia (Müller), but excludes the non-sensory, retinal pigmented epithelium. 

Contemporary regenerative therapies have introduced stem-like cells to replace damaged neurons in the visual system by recapitulating critical processes of eye development. The collective migration of neural stem cells is fundamental to retinogenesis and has been exceptionally well-studied using the fruit fly model of Drosophila Melanogaster. However, the migratory behavior of its retinal neuroblasts (RNBs) has been surprisingly understudied, despite being critical to retinal development in this invertebrate model. The current project developed a new microfluidic system to examine the collective migration of RNBs extracted from the developing visual system of Drosophila as a model for the collective motile processes of replacement neural stem cells. The system scales with the microstructure of the Drosophila optic stalk, which is a pre-cursor to the optic nerve, to produce signaling fields spatially comparable to in vivo RNB stimuli. Experiments used the micro-optic stalk system, or μOS, to demonstrate the preferred sizing and directional migration of collective, motile RNB groups in response to changes in exogenous concentrations of fibroblast growth factor (FGF), which is a key factor in development. Our data highlight the importance of cell-to-cell contacts in enabling cell cohesion during collective RNB migration and point to the unexplored synergy of invertebrate cell study and microfluidic platforms to advance regenerative strategies.