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1. Müller Glia Co-Regulate Barrier Permeability with Endothelial Cells in an Vitro Model of Hyperglycemia

   https://doi.org/10.3390/ijms252212271  

   Peña, Juan S; Berthiaume, François; Vazquez, Maribel (November 2024, International Journal of Molecular Sciences)

   Diabetic retinopathy is a complex, microvascular disease that impacts millions of working adults each year. High blood glucose levels from Diabetes Mellitus lead to the accumulation of advanced glycation end-products (AGEs), which promote inflammation and the breakdown of the inner blood retinal barrier (iBRB), resulting in vision loss. This study used an in vitro model of hyperglycemia to examine how endothelial cells (ECs) and Müller glia (MG) collectively regulate molecular transport. Changes in cell morphology, the expression of junctional proteins, and the reactive oxygen species (ROS) of ECs and MG were examined when exposed to a hyperglycemic medium containing AGEs. Trans-endothelial resistance (TEER) assays were used to measure the changes in cell barrier resistance in response to hyperglycemic and inflammatory conditions, with and without an anti-VEGF compound. Both of the cell types responded to hyperglycemic conditions with significant changes in the cell area and morphology, the ROS, and the expression of the junctional proteins ZO-1, CX-43, and CD40, as well as the receptor for AGEs. The resistivities of the individual and dual ECs and MG barriers decreased within the hyperglycemia model but were restored to that of basal, normoglycemic levels when treated with anti-VEGF. This study illustrated significant phenotypic responses to an in vitro model of hyperglycemia, as well as significant changes in the expression of the key proteins used for cell–cell communication. The results highlight important, synergistic relationships between the ECs and MG and how they contribute to changes in barrier function in combination with conventional treatments. 

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2. Neurovascular Relationships in AGEs-Based Models of Proliferative Diabetic Retinopathy

   https://doi.org/10.3390/bioengineering11010063  

   Peña, Juan S.; Ramanujam, Ranjini K.; Risman, Rebecca A.; Tutwiler, Valerie; Berthiaume, Francois; Vazquez, Maribel (January 2024, Bioengineering)

   Diabetic retinopathy affects more than 100 million people worldwide and is projected to increase by 50% within 20 years. Increased blood glucose leads to the formation of advanced glycation end products (AGEs), which cause cellular and molecular dysfunction across neurovascular systems. These molecules initiate the slow breakdown of the retinal vasculature and the inner blood retinal barrier (iBRB), resulting in ischemia and abnormal angiogenesis. This project examined the impact of AGEs in altering the morphology of healthy cells that comprise the iBRB, as well as the effects of AGEs on thrombi formation, in vitro. Our results illustrate that AGEs significantly alter cellular areas and increase the formation of blood clots via elevated levels of tissue factor. Likewise, AGEs upregulate the expression of cell receptors (RAGE) on both endothelial and glial cells, a hallmark biomarker of inflammation in diabetic cells. Examining the effects of AGEs stimulation on cellular functions that work to diminish iBRB integrity will greatly help to advance therapies that target vision loss in adults. 

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3. Antioxidants Derived from Natural Products Reduce Radiative Damage in Cultured Retinal Glia to Prevent Oxidative Stress

   https://doi.org/10.3390/neuroglia3030006  

   Cliver, Richard N.; Castro, Natalia; Russomano, Thais; Lardieri, Gaetano; Quarrie, Lindsay; van der Merwe, Helena; Vazquez, Maribel (September 2022, Neuroglia)

   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. 

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4. Induced pluripotent stem cell-derived cells model brain microvascular endothelial cell glucose metabolism

   https://doi.org/10.1186/s12987-022-00395-z  

   Weber, Callie M.; Moiz, Bilal; Zic, Sophia M.; Alpízar Vargas, Viviana; Li, Andrew; Clyne, Alisa Morss (December 2022, Fluids and Barriers of the CNS)

   Abstract Glucose transport from the blood into the brain is tightly regulated by brain microvascular endothelial cells (BMEC), which also use glucose as their primary energy source. To study how BMEC glucose transport contributes to cerebral glucose hypometabolism in diseases such as Alzheimer’s disease, it is essential to understand how these cells metabolize glucose. Human primary BMEC (hpBMEC) can be used for BMEC metabolism studies; however, they have poor barrier function and may not recapitulate in vivo BMEC function. iPSC-derived BMEC-like cells (hiBMEC) are readily available and have good barrier function but may have an underlying epithelial signature. In this study, we examined differences between hpBMEC and hiBMEC glucose metabolism using a combination of dynamic metabolic measurements, metabolic mass spectrometry, RNA sequencing, and Western blots. hiBMEC had decreased glycolytic flux relative to hpBMEC, and the overall metabolomes and metabolic enzyme levels were different between the two cell types. However, hpBMEC and hiBMEC had similar glucose metabolism, including nearly identical glucose labeled fractions of glycolytic and TCA cycle metabolites. Treatment with astrocyte conditioned media and high glucose increased glycolysis in both hpBMEC and hiBMEC, though hpBMEC decreased glycolysis in response to fluvastatin while hiBMEC did not. Together, these results suggest that hiBMEC can be used to model cerebral vascular glucose metabolism, which expands their use beyond barrier models. 

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5. 3D microfluidics-assisted modeling of glucose transport in placental malaria

   https://doi.org/10.1038/s41598-022-19422-y  

   Mosavati, Babak; Oleinikov, Andrew; Du, E. (December 2022, Scientific Reports)

   Abstract The human placenta is a critical organ, mediating the exchange of nutrients, oxygen, and waste products between fetus and mother. Placental malaria (PM) resulted from Plasmodium falciparum infections causes up to 200 thousand newborn deaths annually, mainly due to low birth weight, as well as 10 thousand mother deaths. In this work, a placenta-on-a-chip model is developed to mimic the nutrient exchange between the fetus and mother under the influence of PM. In this model, trophoblasts cells (facing infected or uninfected blood simulating maternal blood and termed “trophoblast side”) and human umbilical vein endothelial cells (facing uninfected blood simulating fetal blood and termed “endothelial” side) are cultured on the opposite sides of an extracellular matrix gel in a compartmental microfluidic system, forming a physiological barrier between the co-flow tubular structure to mimic a simplified maternal–fetal interface in placental villi. The influences of infected erythrocytes (IEs) sequestration through cytoadhesion to chondroitin sulfate A (CSA) expressed on the surface of trophoblast cells, a critical feature of PM, on glucose transfer efficiency across the placental barrier was studied. To create glucose gradients across the barrier, uninfected erythrocyte or IE suspension with a higher glucose concentration was introduced into the “trophoblast side” and a culture medium with lower glucose concentration was introduced into the “endothelial side”. The glucose levels in the endothelial channel in response to CSA-adherent erythrocytes infected with CS2 line of parasites in trophoblast channel under flow conditions was monitored. Uninfected erythrocytes served as a negative control. The results demonstrated that CSA-binding IEs added resistance to the simulated placental barrier for glucose perfusion and decreased the glucose transfer across this barrier. The results of this study can be used for better understanding of PM pathology and development of models useful in studying potential treatment of PM. 

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