In the current investigation, the single-cell level of resolution allows for the characterization of regionally specific expression patterns that are not susceptible to differences in population density. While 174 endothelial cells were recovered in our first single-cell RNA-sequencing experiment, all of these cells were grouped in the same cluster Caspofungin and we were unable to detect a distinct populace of choriocapillaris endothelial cells. the retinal pigment epithelium and all major choroidal cell populations. Unique gene expression signatures of arterial, venous, and choriocapillaris vascular beds within the choroid were recognized. was the most up-regulated choriocapillaris gene in a donor diagnosed with AMD. These results provide a characterization of the human RPE and choriocapillaris transcriptome, offering potential insight into the mechanisms of choriocapillaris response to complement Caspofungin injury and choroidal vascular disease in age-related macular degeneration. In human vision, the neural retina serves as a specialized light-sensitive tissue necessary for visual perception. Photoreceptor cells located in the outer retina perform phototransduction, the process of converting a photon of light into a neurochemical signal that will eventually be interpreted as vision. The highly precise physiology of photoreceptor cells relies on support from 2 underlying tissues: the retinal pigment epithelium (RPE) and choroid. The RPE consists of a monolayer of pigmented cells that play an essential role in supporting the retina. The RPE promotes proper photoreceptor cell function by enzymatically preparing retinoids needed for visual transduction (1) and phagocytizing phototransduction machinery (photoreceptor outer segments), allowing for its renewal (2). In addition, the RPE absorbs excess light to minimize nonspecific light scattering (3), quenches oxidative stress (4), and provides metabolic support to photoreceptor cells (5). The RPE overlays the choroid, a heterogeneous connective tissue that supports both the RPE and the outer retina. The choroid houses several cells types found in other connective tissues, including fibroblasts, melanocytes, contractile pericytes/smooth muscle cells, and infiltrating immune cells (6). In addition, the choroid contains a rich vascular system that has the critical role of providing oxygenated blood to the RPE and photoreceptor cells. This choroidal vascular bed provides 85% of blood to the retina (7) and anatomically consists of a very dense superficial capillary system known as the choriocapillaris, as well as underlying medium (Sattlers layer) and large-diameter (Hallers layer) vessels. The choriocapillaris is an exceptionally specialized capillary bed that is imperative for proper retinal function. Developmentally, the choriocapillaris arises from distinct hemangioblast precursor cells, unlike the underlying choroidal vessels (8). In contrast to the retinal vasculature, the choriocapillaris has large-diameter vessels that are fenestrated (6), permitting the dissemination of small molecules through the endothelial layer. Functionally, the choriocapillaris highly expresses HLA class I self-peptides (9), ICAM-1 (10), and carbonic anhydrase 4 (CA4) (11), which help regulate the metabolic and inflammatory environment within the choroid and the tissues it supports. As the RPE and choroid provide crucial support to the retina, diseases affecting the RPE and choroid are responsible for many of the most common causes of vision loss. In particular, age-related macular degeneration (AMD) is a major cause of irreversible blindness in the western world, with a prevalence of 12.3 to 30% in individuals of European descent (12). Dysfunction of both the RPE Caspofungin and the choroid have been widely implicated in AMD pathogenesis. RPE degeneration has been purported to lead to downstream formation of drusen and inflammation (13), and oxidative stress secondary to RPE dysfunction has been postulated as a major source of photoreceptor cell damage (14). Within the choroid, vascular dropout has been observed to precede RPE perturbations (15C17), and such vascular disease has been proposed as the seminal event leading to subsequent retinal degeneration. In particular, the membrane attack complex (MAC), a lytic multiprotein pore forming complex that assembles as a result of complement activation, is elevated in the choriocapillaris with both advancing age and AMD (18). To date, most gene expression studies of the RPE and Caspofungin the choroid have utilized mRNA from pooled RPE and choroidal cell lysates, as these tissues are technically Rabbit polyclonal to ZBTB6 challenging to separate (19C23). Moreover, the cellular diversity of the choroid prevents defining gene expression patterns unique to individual cell populations, hampering further understanding of normal choroidal physiology. Recent advances in single-cell RNA sequencing are capable of addressing these limitations and provide a powerful approach to study gene expression.