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Retinopathy is any damage to the retina of the eyes, which may cause vision impairment. Retinopathy often refers to retinal vascular disease, or damage to the retina caused by abnormal blood flow. Age-related macular degeneration is technically included under the umbrella term retinopathy but is often discussed as a separate entity. Retinopathy, or retinal vascular disease, can be broadly categorized into proliferative and non-proliferative types. Frequently, retinopathy is an ocular manifestation of systemic disease as seen in diabetes or hypertension. Diabetes is the most common cause of retinopathy in the U.S. as of 2008. Diabetic retinopathy is the leading cause of blindness in working-aged people. It accounts for about 5% of blindness worldwide and is designated a priority eye disease by the World Health Organization.
Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature mainly by processes of sprouting and splitting, but processes such as coalescent angiogenesis, vessel elongation and vessel cooption also play a role. Vasculogenesis is the embryonic formation of endothelial cells from mesoderm cell precursors, and from neovascularization, although discussions are not always precise. The first vessels in the developing embryo form through vasculogenesis, after which angiogenesis is responsible for most, if not all, blood vessel growth during development and in disease.
Pericytes are multi-functional mural cells of the microcirculation that wrap around the endothelial cells that line the capillaries throughout the body. Pericytes are embedded in the basement membrane of blood capillaries, where they communicate with endothelial cells by means of both direct physical contact and paracrine signaling. The morphology, distribution, density and molecular fingerprints of pericytes vary between organs and vascular beds. Pericytes help to maintain homeostatic and hemostatic functions in the brain, one of the organs with higher pericyte coverage, and also sustain the blood–brain barrier. These cells are also a key component of the neurovascular unit, which includes endothelial cells, astrocytes, and neurons. Pericytes have been postulated to regulate capillary blood flow and the clearance and phagocytosis of cellular debris in vitro. Pericytes stabilize and monitor the maturation of endothelial cells by means of direct communication between the cell membrane as well as through paracrine signaling. A deficiency of pericytes in the central nervous system can cause increased permeability of the blood–brain barrier.
Vascular endothelial growth factor, originally known as vascular permeability factor (VPF), is a signal protein produced by many cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors, the platelet-derived growth factor family of cystine-knot growth factors. They are important signaling proteins involved in both vasculogenesis and angiogenesis.
An angiogenesis inhibitor is a substance that inhibits the growth of new blood vessels (angiogenesis). Some angiogenesis inhibitors are endogenous and a normal part of the body's control and others are obtained exogenously through pharmaceutical drugs or diet.
Neovascularization is the natural formation of new blood vessels, usually in the form of functional microvascular networks, capable of perfusion by red blood cells, that form to serve as collateral circulation in response to local poor perfusion or ischemia.
Endothelial stem cells (ESCs) are one of three types of stem cells found in bone marrow. They are multipotent, which describes the ability to give rise to many cell types, whereas a pluripotent stem cell can give rise to all types. ESCs have the characteristic properties of a stem cell: self-renewal and differentiation. These parent stem cells, ESCs, give rise to progenitor cells, which are intermediate stem cells that lose potency. Progenitor stem cells are committed to differentiating along a particular cell developmental pathway. ESCs will eventually produce endothelial cells (ECs), which create the thin-walled endothelium that lines the inner surface of blood vessels and lymphatic vessels. The lymphatic vessels include things such as arteries and veins. Endothelial cells can be found throughout the whole vascular system and they also play a vital role in the movement of white blood cells
Angiopoietin is part of a family of vascular growth factors that play a role in embryonic and postnatal angiogenesis. Angiopoietin signaling most directly corresponds with angiogenesis, the process by which new arteries and veins form from preexisting blood vessels. Angiogenesis proceeds through sprouting, endothelial cell migration, proliferation, and vessel destabilization and stabilization. They are responsible for assembling and disassembling the endothelial lining of blood vessels. Angiopoietin cytokines are involved with controlling microvascular permeability, vasodilation, and vasoconstriction by signaling smooth muscle cells surrounding vessels. There are now four identified angiopoietins: ANGPT1, ANGPT2, ANGPTL3, ANGPT4.
VEGF receptors (VEGFRs) are receptors for vascular endothelial growth factor (VEGF). There are three main subtypes of VEGFR, numbered 1, 2 and 3. Depending on alternative splicing, they may be membrane-bound (mbVEGFR) or soluble (sVEGFR).
Vascular endothelial growth factor receptor 1 is a protein that in humans is encoded by the FLT1 gene.
Vascular endothelial growth factor C (VEGF-C) is a protein that is a member of the platelet-derived growth factor / vascular endothelial growth factor (PDGF/VEGF) family. It is encoded in humans by the VEGFC gene, which is located on chromosome 4q34.
Neuropilin-1 is a protein that in humans is encoded by the NRP1 gene. In humans, the neuropilin 1 gene is located at 10p11.22. This is one of two human neuropilins.
Pigment epithelium-derived factor (PEDF) also known as serpin F1 (SERPINF1), is a multifunctional secreted protein that has anti-angiogenic, anti-tumorigenic, and neurotrophic functions. Found in vertebrates, this 50 kDa protein is being researched as a therapeutic candidate for treatment of such conditions as choroidal neovascularization, heart disease, and cancer. In humans, pigment epithelium-derived factor is encoded by the SERPINF1 gene.
C-fos-induced growth factor (FIGF) is a vascular endothelial growth factor that in humans is encoded by the FIGF gene.
Vascular endothelial growth factor A (VEGF-A) is a protein that in humans is encoded by the VEGFA gene.
Angiogenesis is the process of forming new blood vessels from existing blood vessels, formed in vasculogenesis. It is a highly complex process involving extensive interplay between cells, soluble factors, and the extracellular matrix (ECM). Angiogenesis is critical during normal physiological development, but it also occurs in adults during inflammation, wound healing, ischemia, and in pathological conditions such as rheumatoid arthritis, hemangioma, and tumor growth. Proteolysis has been indicated as one of the first and most sustained activities involved in the formation of new blood vessels. Numerous proteases including matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase domain (ADAM), a disintegrin and metalloproteinase domain with throbospondin motifs (ADAMTS), and cysteine and serine proteases are involved in angiogenesis. This article focuses on the important and diverse roles that these proteases play in the regulation of angiogenesis.
Tumstatin is a protein fragment cleaved from collagen that serves as both an antiangiogenic and proapoptotic agent. It has similar function to canstatin, endostatin, restin, and arresten, which also affect angiogenesis. Angiogenesis is the growth of new blood vessels from pre-existing blood vessels, and is important in tumor growth and metastasis. Angiogenesis is stimulated by many growth factors, the most prevalent of which is vascular endothelial growth factor (VEGF).
Neuroangiogenesis is the coordinated growth of nerves and blood vessels. The nervous and blood vessel systems share guidance cues and cell-surface receptors allowing for this synchronised growth. The term neuroangiogenesis only came into use in 2002 and the process was previously known as neurovascular patterning. The combination of neurogenesis and angiogenesis is an essential part of embryonic development and early life. It is thought to have a role in pathologies such as endometriosis, brain tumors, and Alzheimer's disease.
Tumor-associated endothelial cells or tumor endothelial cells (TECs) refers to cells lining the tumor-associated blood vessels that control the passage of nutrients into surrounding tumor tissue. Across different cancer types, tumor-associated blood vessels have been discovered to differ significantly from normal blood vessels in morphology, gene expression, and functionality in ways that promote cancer progression. There has been notable interest in developing cancer therapeutics that capitalize on these abnormalities of the tumor-associated endothelium to destroy tumors.
Endothelial cell anergy is a condition during the process of angiogenesis, where endothelial cells, the cells that line the inside of blood vessels, can no longer respond to inflammatory cytokines. These cytokines are necessary to induce the expression of cell adhesion molecules to allow leukocyte infiltration from the blood into the tissue at places of inflammation, such as a tumor. This condition, which protects the tumor from the immune system, is the result of exposure to angiogenic growth factors.
References
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- ↑ Aillaud, Chrystelle; Bosc, Christophe; Peris, Leticia; Bosson, Anouk; Heemeryck, Pierre; Dijk, Juliette Van; Friec, Julien Le; Boulan, Benoit; Vossier, Frédérique (2017-12-15). "Vasohibins/SVBP are tubulin carboxypeptidases (TCPs) that regulate neuron differentiation". Science. 358 (6369): 1448–1453. Bibcode:2017Sci...358.1448A. doi: 10.1126/science.aao4165 . ISSN 0036-8075. PMID 29146868.
- ↑ Masuda, Kana; Tanabe, Katsuyuki; Ujike, Haruyo; Hinamoto, Norikazu; Miyake, Hiromasa; Tanimura, Satoshi; Sugiyama, Hitoshi; Sato, Yasufumi; Maeshima, Yohei (2018-04-11). "Deletion of pro-angiogenic factor vasohibin-2 ameliorates glomerular alterations in a mouse diabetic nephropathy model". PLOS ONE. 13 (4): e0195779. Bibcode:2018PLoSO..1395779M. doi: 10.1371/journal.pone.0195779 . ISSN 1932-6203. PMC 5895058 . PMID 29641565.