Abstract: Pathological retinal neovascularization is the hallmark of primary blinding diseases across all age groups, yet surprisingly little is known about the causative factors. These diseases include diabetic retinopathy and retinopathy of prematurity where progressive decay of retinal vasculature yields zones of neural ischemia. These avascular zones and the hypoxic neurons and glia that reside in them are the source of pro-angiogenic factors that mediate destructive pre-retinal angiogenesis. Central neurons such as retinal ganglion cells (RGCs), which are directly apposed to degenerating vasculature in ischemic retinopathies, require stable metabolic supply for proper function. However, we unexpectedly found that RGCs are resilient to hypoxia/ischemia and a generally compromised metabolic supply and instead of degenerating, trigger protective mechanisms of cellular senescence. Paradoxically, while potentially favoring neuronal survival, the senescent state of RGCs is incompatible with vascular repair as they adopt a senescence-associated secretory phenotype (SASP) that provokes release of a secretome of inflammatory cytokines that drives paracrine senescence and further exacerbates pathological angiogenesis. The mechanisms that lead to retinal cellular senescence and dormancy as well as the therapeutic potential of targeting these pathways will be discussed.

Abstract: Subretinal inflammation plays a critical role in retinal degenerative diseases. Although activated macrophages have been shown to play a key role in the progression of retinopathies and specifically in age-related macular degeneration, little is known about the mechanisms involved in the loss of photoreceptors leading to vision impairment. In our study on retinal damages induced by photo-oxidative stress, we have observed that CD36-deficient mice featured less subretinal macrophage accumulation with attenuated photoreceptor degeneration compared to wild-type (WT) mice. Treatment with CD36-selective azapeptide ligand (labelled MPE-001) as modulator of the inflammatory environment of the retina reduced subretinal macrophage/activated microglia accumulation with preservation of photoreceptor layers and function assessed by ERG in WT, in a CD36-dependent manner. The azapeptide modulated the transcriptome of subretinal macrophage/activated microglia by reducing pro-inflammatory markers. In isolated macrophages, the CD36-selective azapeptide induced dissociation of the CD36-TLR2/6 heterodimer complex (using FRET) altering the TLR2 signaling pathway, thus decreasing NF-KB activation and inflammasome activity. The azapeptide also incurred cytoprotection against photoreceptor apoptosis elicited by activated macrophages. These findings suggest that the azapeptide as ligand of co-receptor CD36 decreases the inflammatory response by modulating CD36-TLR2/6 complex signaling pathway in macrophages, and suggests its potential application in the treatment of retinal degenerative diseases.

Abstract: The bone morphogenetic protein (BMP) family of proteins has a multitude of roles throughout the body. It plays important roles in development and in the adult vascular endothelium, by modulating the angiogenic response. The endothelial-specific receptor BMP receptor Alk1 is of particular importance in the proper remodeling of the vasculature and its ligand BMP9 has been shown to be a potent inhibitor of neovascularization. Dysregulated BMP signaling has been linked to multiple vascular diseases and can lead to the abnormal angiogenesis. We therefore investigated the role of BMP9/Alk1 signaling in retinal angiogenesis, and its therapeutic implications for vascular pathologies of the eye.

Abstract: Autophagy recycles intracellular substrate in part to fuel mitochondria during starvation. Deregulated autophagy caused by dyslipidemia, oxidative stress, and aging is associated with early signs of age-related macular degeneration (AMD), such as lipofuscin and perhaps drusen accumulation. Intracellular nutrient sensors for glucose and amino acids regulate autophagy. The role of lipid sensors in controlling autophagy, however, remains ill-defined. Here we will show that abundant circulating lipids trigger a satiety signal through FA receptors that restrain autophagy and oxidative mitochondrial metabolism. In the presence of excess dietary lipids, fatty acid sensors might protect tissues with high metabolic rates against lipotoxicity, favoring their storage, instead, in adipose tissues. However, sustained exposure to lipid reduces retinal metabolic efficiency. In photoreceptors with high metabolic needs, it predisposes to an energy failure and triggers compensatory albeit pathological angiogenesis, leading to blinding neovascular AMD.

Abstract: The inverted retina is a basic characteristic of the vertebrate eye. This implies that vertebrates must have a common ancestor with an inverted retina. Of the two groups of chordates, cephalochordates have an inverted retina and urochordates a direct retina. Surprisingly, recent genetics studies favor urochordates as the closest ancestor to vertebrates. The evolution of increasingly complex organs such as the eye implies not only tissular but also structural modifications at the organ level. How these configurational modifications give rise to a functional eye at any step is still subject to debate and speculation. Here we propose an orderly sequence of phylogenetic events that closely follows the sequence of developmental eye formation in extant vertebrates. The progressive structural complexity has been clearly recorded during vertebrate development at the period of organogenesis. Matching the chain of increasing eye complexity in Mollusca that leads to the bicameral eye of the octopus and the developmental sequence in vertebrates, we delineate the parallel evolution of the two-chambered eye of vertebrates starting with an early ectodermal eye. This sequence allows for some interesting predictions regarding the eyes of not preserved intermediary species. The clue to understanding the inverted retina of vertebrates and the similarity between the sequence followed by Mollusca and chordates is the notion that the eye in both cases is an ectodermal structure, in contrast to an exclusively (de novo) neuroectodermal origin in the eye of vertebrates. This analysis places cephalochordates as the closest branch to vertebrates contrary to urochordates, claimed as a closer branch by some researchers that base their proposals in a genetic analysis.

Abstract: Pediatric neuro-ophthalmology is a subspecialty within neuro-ophthalmology. Pediatric neuro-ophthalmic diseases must be considered separate from their adult counterparts, due to the distinctive nature of the examination, clinical presentations, and management choices. This manuscript will highlight four common pediatric neuro-ophthalmic disorders by describing common clinical presentations, recommended management, and highlighting recent developments. Diseases discussed include pediatric idiopathic intracranial hypertension (IIH), pseudopapilledema, optic neuritis (ON) and optic pathway gliomas (OPG). The demographics, diagnosis and management of common pediatric neuro-ophthalmic disease require a working knowledge of the current research presented herein. Special attention should be placed on the differences between pediatric and adult entities such that children can be appropriately diagnosed and treated.