Brogden, N. K. | bioRxiv Science

bioRxiv2024

Development of self-healing hydrogels to support choroidal endothelial cell transplantation for the treatment of early age related macular degeneration

In retinal diseases such as age-related macular degeneration (AMD) and choroideremia, a key pathophysiologic step is loss of endothelial cells of the choriocapillaris, the dense vascular bed required for maintaining health and function of the retina. As such, repopulation of choroidal vasculature early in the disease process may halt disease progression. Prior studies have shown that injection of donor cells in suspension results in significant cellular efflux and poor cell survival. As such, the goal of this study was to develop a hydrogel system designed to support CEC transplantation. A library of hydrogels was synthesized using laminin (i.e., LN111, LN121, and LN421), carboxy methyl chitosan, and oxidized dextran via reversible Schiff base chemistry. Each of the developed hydrogels was readily injectable into the suprachoroidal space, with excellent gelation, mechanical, and degradation properties. Laminin-based hydrogels were compatible with immortalized CEC survival in vitro, and suprachoroidal injection of LN111 and LN121 containing gels were well-tolerated in an in vivo rat model, whereas LN421 containing gels caused significant chorioretinal inflammation. Hydrogels were detected in the suprachoroidal space of immunosuppressed rats at 1-week post-injection and were completely resorbed by 1-month post-injection. There were significantly more CECs retained in immunosuppressed rats that received cell laden hydrogels than those that received unsupported cell suspensions (i.e., CECs only). These findings pave the way for future CEC replacement studies in animal models of choroidal cell loss toward the development of future therapies. Statement of significanceAge related macular degeneration (AMD) is a leading cause of untreatable blindness in the industrial world. A key pathologic step in AMD is loss of the choriocapillaris endothelial cells, which provide vascular support to the overlying retina, including the light-sensing photoreceptors. We believe that choroidal cell replacement early in disease may prevent retinal cell death and subsequent vision loss. In this study, we present a strategy for repopulating the choriocapillaris using choroidal endothelial cell laden hydrogels. Specifically, we demonstrate the synthesis and characterization of 3 different laminin-based hydrogel systems. LN111 and LN121 hydrogels were found to increase retention of choroidal endothelial cells following suprachoroidal transplantation. These findings pave the way for future cell replacement studies in animal models of choroidal cell dropout.

bioengineering↗

bioRxiv2019

Vascular endothelial growth factor (VEGF) expression and neuroinflammation is increased in the frontopolar cortex of individuals with autism spectrum disorder

Autism spectrum disorder (ASD) etiology is a complex mixture of genetic and environmental factors, the relative contributions of which varies across patients. Despite complex etiology, researchers observe consistent neurodevelopmental features in ASD patients, notably atypical forebrain cortical development. Growth factors, cytokines, and chemokines are important mediators of forebrain cortical development, but have not been thoroughly examined in brain tissues from individuals with autism. Here, we performed an integrative analysis of RNA and protein expression using frontopolar cortex tissues dissected from individuals with ASD and controls, hypothesizing that ASD patients will exhibit aberrant expression of growth factors, cytokines, and chemokines critical for neurodevelopment. We performed group-wise comparisons of RNA expression via RNA-Seq and growth factor, cytokine, and chemokine expression via multiplex enzyme-linked immunosorbent assay (ELISA). We also analyzed single cell sequencing data from the frontopolar cortex of typically developed individuals to identify cell types that express the growth factors we found differentially expressed in ASD. Our RNA-Seq analysis revealed 11 differentially expressed genes in ASD versus control brains, the most significant of which encodes for vascular endothelial growth factor (VEGF-A). Both RNA and protein levels of VEGF-A were upregulated in ASD brains. Our single cell analysis revealed that VEGF is expressed primarily by non-neuronal cells. We also found that the differentially expressed genes from our RNA-Seq analysis are enriched in microglia. The increased VEGF-A expression we observed in ASD, coupled with the enrichment of differentially expressed genes in microglia, begs the question of the role VEGF-A is playing in ASD. Microglia activation, as indicated by our RNA-Seq results, and the VEGF-A isoform expression we see in the ASD cortex, leads us to conclude that VEGF-A is playing a pro-inflammatory role, perhaps with unwanted long-term consequences for neurodevelopment.

genomics↗