Investigation of Retinal Hemodynamics in a Diabetic Animal Model and VEGF Induced Animal Model

Diabetic retinopathy (DR) is a complication of diabetes that can ultimately lead to vision loss. Early changes of DR include leukocyte adhesion, pericyte loss, and alterations in retinal blood flow. These changes typically occur prior to clinical diagnosis and can develop into more severe problems such as neovascularization and angiogenesis. The objective of the current study was to investigate retinal hemodynamics in early stages of DR in a diabetic animal model and to evaluate the effect of insulin therapy on retinal hemodynamics in diabetic rats in order to demonstrate how controlled blood glucose levels may regulate changes in vasculature. Lastly, the role of vascular endothelial growth factor (VEGF) on retinal hemodynamics of a normal animal were studied to determine the effects of elevated levels of VEGF on retinal vasculature. Volumetric blood flow (VBF) was quantified using average blood velocity and average diameter measured by using the scanning laser ophthalmoscope (SLO) and the particle tracking method. Pericyte coverage was also quantified with a whole-mount retina technique. In diabetic rats, it was shown that arterial and venous VBF decreased beginning at two weeks post onset of diabetes and continued to decrease throughout the eight week time period. There was no significant loss of pericytes at the eight week time point, however, structural abnormalities were observed at the capillary level. Following insulin therapy, the VBF values of treated diabetic animals were comparable to normal animal VBF values and insulin therapy seemed to normalize VBF of diabetic animals. Exogenous levels of VEGF in normal animals showed significant changes in retinal hemodynamics and vasculature. Future experiments should include investigation of factors that may alter retinal blood flow and quantification of VEGF levels in diabetic animals.Ph.D. in Biomedical Engineering, May 201

Somatic loss of PIK3R1 may sensitize breast cancer to inhibitors of the MAPK pathway

Purpose: The PI3K pathway, which includes the PI3K catalytic subunits p110α (PIK3CA) and the PI3K regulatory subunit p85α (PIK3R1), is the most frequently altered pathway in cancer. We encountered a breast cancer patient whose tumor contained a somatic alteration in PIK3R1. Some commercial sequencing platforms suggest that somatic mutations in PIK3R1 may sensitize cancers to drugs that inhibit the mammalian target of rapamycin (mTOR). However, a review of the preclinical and clinical literature did not find evidence substantiating that hypothesis. The purpose of this study was to knock out PIK3R1 in order to determine the optimal therapeutic approach for breast cancers lacking p85α. Methods: We created an isogenic cellular system by knocking out both alleles of the PIK3R1 gene in the non-tumorigenic human breast cell line MCF-10A. Knockout cells were compared with wild-type cells by measuring growth, cellular signaling, and response to drugs. Results: We observed hyperphosphorylation of MEK in these knockouts, which sensitized PIK3R1-null cells to a MEK inhibitor, trametinib. However, they were not sensitized to the mTOR inhibitor, everolimus. Conclusions: Our findings suggest that breast cancers with loss of p85α may not respond to mTOR inhibition, but may be sensitive to MEK inhibition

Inactivation of the microRNA-183/96/182 cluster results in syndromic retinal degeneration

The microRNA-183/96/182 cluster is highly expressed in the retina and other sensory organs. To uncover its in vivo functions in the retina, we generated a knockout mouse model, designated “miR-183C(GT/GT),” using a gene-trap embryonic stem cell clone. We provide evidence that inactivation of the cluster results in early-onset and progressive synaptic defects of the photoreceptors, leading to abnormalities of scotopic and photopic electroretinograms with decreased b-wave amplitude as the primary defect and progressive retinal degeneration. In addition, inactivation of the miR-183/96/182 cluster resulted in global changes in retinal gene expression, with enrichment of genes important for synaptogenesis, synaptic transmission, photoreceptor morphogenesis, and phototransduction, suggesting that the miR-183/96/182 cluster plays important roles in postnatal functional differentiation and synaptic connectivity of photoreceptors