Retinal pigment epithelial cells reduce vascular leak and proliferation in retinal neovessels.

In multiple neurodegenerative diseases, including age-related macular degeneration, retinitis pigmentosa, and macular telangiectasia type 2 (MacTel), retinal pigment epithelial (RPE)-cells proliferate and migrate into the neuroretina, forming intraretinal pigment plaques. Though these pigmentary changes are hallmarks of disease progression, it is unknown if their presence is protective or detrimental.Here, we first evaluated the impact of pigment plaques on vascular changes and disease progression in MacTel.

The effect of phosphorylation efficiency on the oncogenic properties of the protein E7 from high-risk HPV.

The Human papillomavirus (HPV) causes tumors in part by hijacking the host cell cycle and forcing uncontrolled cellular division. While there are >200 genotypes of HPV, 15 are classified as high-risk and have been shown to transform infected cells and contribute to tumor formation. The remaining low-risk genotypes are not considered oncogenic and result in benign skin lesions.

A novel method of screening combinations of angiostatics identifies bevacizumab and temsirolimus as synergistic inhibitors of glioma-induced angiogenesis.

Tumor angiogenesis is critical for the growth and progression of cancer. As such, angiostasis is a treatment modality for cancer with potential utility for multiple types of cancer and fewer side effects. However, clinical success of angiostatic monotherapies has been moderate, at best, causing angiostatic treatments to lose their early luster.

Serine biosynthesis defect due to haploinsufficiency of PHGDH causes retinal disease.

Macular telangiectasia type 2 (MacTel) is a progressive, late-onset retinal degenerative disease linked to decreased serum levels of serine that elevate circulating levels of a toxic ceramide species, deoxysphingolipids (deoxySLs); however, causal genetic variants that reduce serine levels in patients have not been identified. Here we identify rare, functional variants in the gene encoding the rate-limiting serine biosynthetic enzyme, phosphoglycerate dehydrogenase (PHGDH), as the single locus accounting for a significant fraction of MacTel. Under a dominant collapsing analysis model of a genome-wide enrichment analysis of rare variants predicted to impact protein function in 793 MacTel cases and 17,610 matched controls, the PHGDH gene achieves genome-wide significance (P = 1.

Retinal microglia are critical for subretinal neovascular formation.

Abnormal subretinal neovascularization is a characteristic of vision-threatening retinal diseases, including macular telangiectasia (MacTel) and retinal angiomatous proliferation (RAP). Subretinal neovascular tufts and photoreceptor dysfunction are observed in very-low-density lipoprotein receptor (Vldlr-/-) mutant mice. These changes mirror those observed in patients with MacTel and RAP, but the pathogenesis is largely unknown.

Serine and Lipid Metabolism in Macular Disease and Peripheral Neuropathy.

Background: Identifying mechanisms of diseases with complex inheritance patterns, such as macular telangiectasia type 2, is challenging. A link between macular telangiectasia type 2 and altered serine metabolism has been established previously.

Methods: Through exome sequence analysis of a patient with macular telangiectasia type 2 and his family members, we identified a variant in encoding a subunit of serine palmitoyltransferase (SPT).

miR-30a-5p inhibition promotes interaction of Fas endothelial cells and FasL microglia to decrease pathological neovascularization and promote physiological angiogenesis.

Ischemia-induced angiogenesis contributes to various neuronal and retinal diseases, and often results in neurodegeneration and visual impairment. Current treatments involve the use of anti-VEGF agents but are not successful in all cases. In this study we determined that miR-30a-5p is another important mediator of retinal angiogenesis.

Angiogenesis and Eye Disease.

The retina consists of organized layers of photoreceptors, interneurons, glia, epithelial cells, and endothelial cells. The economic model of supply and demand used to appropriately determine cost is highly applicable to the retina, in which the extreme metabolic demands of phototransduction are met by precisely localized and designed vascular networks. Proper development and maintenance of these networks is critical to normal visual function; dysregulation is characteristic of several devastating human diseases, including but not limited to age-related macular degeneration and diabetic retinopathy.

Neurovascular crosstalk between interneurons and capillaries is required for vision.

Functional interactions between neurons, vasculature, and glia within neurovascular units are critical for maintenance of the retina and other CNS tissues. For example, the architecture of the neurosensory retina is a highly organized structure with alternating layers of neurons and blood vessels that match the metabolic demand of neuronal activity with an appropriate supply of oxygen within perfused blood. Here, using murine genetic models and cell ablation strategies, we have demonstrated that a subset of retinal interneurons, the amacrine and horizontal cells, form neurovascular units with capillaries in 2 of the 3 retinal vascular plexuses.

Astrocyte hypoxic response is essential for pathological but not developmental angiogenesis of the retina.

Vascular/parenchymal crosstalk is increasingly recognized as important in the development and maintenance of healthy vascularized tissues. The retina is an excellent model in which to study the role of cell type-specific contributions to the process of blood vessel and neuronal growth. During retinal vascular development, glial cells such as astrocytes provide the template over which endothelial cells migrate to form the retinal vascular network, and hypoxia-regulated vascular endothelial growth factor (VEGF) has been demonstrated to play a critical role in this process as well as pathological neovascularization.

Maintaining retinal astrocytes normalizes revascularization and prevents vascular pathology associated with oxygen-induced retinopathy.

Astrocytes are well known modulators of normal developmental retinal vascularization. However, relatively little is known about the role of glial cells during pathological retinal neovascularization (NV), a leading contributor to vision loss in industrialized nations. We demonstrate that the loss of astrocytes and microglia directly correlates with the development of pathological NV in a mouse model of oxygen-induced retinopathy (OIR).

Antioxidant or neurotrophic factor treatment preserves function in a mouse model of neovascularization-associated oxidative stress.

In several disease states, abnormal growth of blood vessels is associated with local neuronal degeneration. This is particularly true in ocular diseases such as retinal angiomatous proliferation (RAP) and macular telangiectasia (MacTel), in which, despite the absence of large-scale leakage or hemorrhage, abnormal neovascularization (NV) is associated with local neuronal dysfunction. We describe here a retinal phenotype in mice with dysfunctional receptors for VLDL (Vldlr-/- mice) that closely resembles human retinal diseases in which abnormal intra- and subretinal NV is associated with photoreceptor cell death.

Chapter 6. Ocular models of angiogenesis.

During normal retinal vascular development, vascular endothelial cells proliferate and migrate through the extracellular matrix in response to a variety of cytokines, leading to the formation of new blood vessels in a highly ordered fashion. However, abnormal angiogenesis contributes to the vast majority of diseases that cause catastrophic loss of vision. During abnormal neovascularization of the iris, retina, or choroid, angiogenesis is unregulated and usually results in the formation of dysfunctional blood vessels.

Progenitor cells and retinal angiogenesis.

Nothing more dramatically captures the imagination of the visually impaired patient or the ophthalmologist treating them than the possibility of rebuilding a damaged retina or vasculature with "stem cells." Stem cells (SC) have been isolated from adult tissues and represent a pool of cells that may serve to facilitate rescue/repair of damaged tissue following injury or stress. We propose a new paradigm to "mature" otherwise immature neovasculature or, better yet, stabilize existing vasculature to hypoxic damage.

Ocular neovascularization: basic mechanisms and therapeutic advances.

The vast majority of diseases that cause catastrophic loss of vision do so as a result of ocular neovascularization. During normal retinal vascular development, vascular endothelial cells proliferate and migrate through the extracellular matrix in response to a variety of cytokines, leading to the formation of new blood vessels in a highly ordered fashion. During abnormal neovascularization of the iris, retina, or choroid, angiogenesis is unregulated and usually results in the formation of dysfunctional blood vessels.

Combination angiostatic therapy completely inhibits ocular and tumor angiogenesis.

Angiostatic therapies designed to inhibit neovascularization associated with multiple pathological conditions have only been partially successful; complete inhibition has not been achieved. We demonstrate synergistic effects of combining angiostatic molecules that target distinct aspects of the angiogenic process, resulting in the complete inhibition of neovascular growth associated with development, ischemic retinopathy, and tumor growth, with little or no effect on normal, mature tissue vasculature. Tumor vascular obliteration using combination angiostatic therapy was associated with reduced tumor mass and increased survival in a rat 9L gliosarcoma model, whereas individual monotherapies were ineffective.

Myeloid progenitors differentiate into microglia and promote vascular repair in a model of ischemic retinopathy.

Vision loss associated with ischemic diseases such as retinopathy of prematurity and diabetic retinopathy are often due to retinal neovascularization. While significant progress has been made in the development of compounds useful for the treatment of abnormal vascular permeability and proliferation, such therapies do not address the underlying hypoxia that stimulates the observed vascular growth. Using a model of oxygen-induced retinopathy, we demonstrate that a population of adult BM-derived myeloid progenitor cells migrated to avascular regions of the retina, differentiated into microglia, and facilitated normalization of the vasculature.

T2-TrpRS inhibits preretinal neovascularization and enhances physiological vascular regrowth in OIR as assessed by a new method of quantification.

Purpose: A carboxyl-terminal fragment of tryptophan tRNA synthetase (T2-TrpRS) has demonstrated potent angiostatic activity during retinal developmental neovascularization in vivo. The effects of T2-TrpRS on pathologic neovascularization were tested and compared with a potent VEGF antagonist using the mouse model of oxygen-induced retinopathy (OIR).

Methods: C57BL/6J mice were transiently exposed to hyperoxic conditions (75% O2) between postnatal day 7 (P7) and P12 and then returned to room air.

Mechanisms of endothelial cell guidance and vascular patterning in the developing mouse retina.

The appropriate guidance and patterning of vessels during vascular development is critical for proper tissue function. The loss of these guidance mechanisms can lead to abnormal vascularization and a number of pathological conditions. The molecular basis of endothelial cell guidance and subsequent tissue specific vascular patterning remains largely unknown in spite of its clinical relevance and biological importance.

Identifying potential regulators of infantile hemangioma progression through large-scale expression analysis: a possible role for the immune system and indoleamine 2,3 dioxygenase (IDO) during involution.

Hemangiomas are benign endothelial tumors. Often referred to as hemangiomas of infancy (HOI), these tumors are the most common tumor of infancy. Most of these lesions proliferate rapidly in the first months of life, and subsequently slowly involute during early childhood without significant complications.

Rescue of retinal degeneration by intravitreally injected adult bone marrow-derived lineage-negative hematopoietic stem cells.

Inherited retinal degenerations afflict 1 in 3,500 individuals and are a heterogeneous group of diseases that result in profound vision loss, usually the result of retinal neuronal apoptosis. Atrophic changes in the retinal vasculature are also observed in many of these degenerations. While it is thought that this atrophy is secondary to diminished metabolic demand in the face of retinal degeneration, the precise relationship between the retinal neuronal and vascular degeneration is not clear.

Regulation of angiogenesis by tissue factor cytoplasmic domain signaling.

Hemostasis initiates angiogenesis-dependent wound healing, and thrombosis is frequently associated with advanced cancer. Although activation of coagulation generates potent regulators of angiogenesis, little is known about how this pathway supports angiogenesis in vivo. Here we show that the tissue factor (TF)-VIIa protease complex, independent of triggering coagulation, can promote tumor and developmental angiogenesis through protease-activated receptor-2 (PAR-2) signaling.

Global gene expression analysis of the developing postnatal mouse retina.

Purpose: Postnatal mouse retinal development involves glial and neuronal differentiation, vascularization, and the onset of vision. In the current study, the gene expression profiles of thousands of genes in the developing postnatal mouse retina were analyzed and compared in a large-scale, unbiased microarray gene expression analysis.

Methods: For each of eight different time points during postnatal mouse retinal development, two separate sets of 30 retinas were pooled for RNA isolation, and gene expression was analyzed by hybridization to gene chips in triplicate (Mu74Av2; Affymetrix, Santa Clara, CA).

Adult bone marrow-derived stem cells use R-cadherin to target sites of neovascularization in the developing retina.

Adult bone marrow contains a population of hematopoietic stem cells (HSCs) that can give rise to cells capable of targeting sites of neovascularization in the peripheral or retinal vasculature. However, relatively little is known about the mechanism of targeting of these cells to sites of neovascularization. We have analyzed subpopulations of HSCs for the expression of a variety of cell surface adhesion molecules and found that R-cadherin, a calcium-dependent cell-cell adhesion molecule important for normal retinal endothelial cell guidance, was preferentially expressed by functionally targeting HSCs.

Retinal vascular development is mediated by endothelial filopodia, a preexisting astrocytic template and specific R-cadherin adhesion.

Purpose: A neonatal mouse retina developmental model was used to study endothelial cell guidance and subsequent formation of vascular patterns. Since most diseases that cause catastrophic loss of vision do so as a result of abnormal ocular angiogenesis, a better understanding of events regulating normal retinal vascular growth may provide insight into pathologic angiogenesis.

Methods: Development of the retinal vasculature at various postnatal and embryonic time points was analyzed by collagen IV immunohistochemistry and staining with isolectin Griffonia simplicifolia.