Growth Of Retinal Blood Vessels Research Articles

Photoreceptors inhibit pathological retinal angiogenesis through transcriptional regulation of Adam17 via c-Fos

Pathological retinal angiogenesis profoundly impacts visual function in vascular eye diseases, such as retinopathy of prematurity (ROP) in preterm infants and age-related macular degeneration in the elderly. While the involvement of photoreceptors in these diseases is recognized, the underlying mechanisms remain unclear. This study delved into the pivotal role of photoreceptors in regulating abnormal retinal blood vessel growth using an oxygen-induced retinopathy (OIR) mouse model through the c-Fos/A disintegrin and metalloprotease 17 (Adam17) axis. Our findings revealed a significant induction of c-Fos expression in rod photoreceptors, and c-Fos depletion in these cells inhibited pathological neovascularization and reduced blood vessel leakage in the OIR mouse model. Mechanistically, c-Fos directly regulated the transcription of Adam17 a shedding protease responsible for the production of bioactive molecules involved in inflammation, angiogenesis, and cell adhesion and migration. Furthermore, we demonstrated the therapeutic potential by using an adeno-associated virus carrying a rod photoreceptor-specific short hairpin RNA against c-fos which effectively mitigated abnormal retinal blood vessel overgrowth, restored retinal thickness, and improved electroretinographic (ERG) responses. In conclusion, this study highlights the significance of photoreceptor c-Fos in ROP pathology, offering a novel perspective for the treatment of this disease.

4 Severity of Retinopathy of Prematurity and Motor Skills Development in Preschoolers

AbstractObjective:Children born preterm are at increased risk of deviation from the typical developmental trajectory. The probability of adverse developmental sequelae is increased in those with history of major perinatal complications. Retinopathy of prematurity (ROP) is a pathological disordered growth of retinal blood vessels occurring in very preterm neonates who require supplemental oxygen. ROP has been linked to intermittent hypoxemic events and blood gas derangements occurring in the Neonatal Intensive Care Unit (NICU), particularly in ventilated infants. Though presence and severity of ROP have been linked to neurodevelopmental impairment, little is known about the relationship between ROP severity and motor development in the preschool age. Because the same hypoxemic events and blood gas changes that lead to severe ROP may also lead to greater developmental deficits in motor control, we hypothesized that ROP severity will be inversely linked to the quality of motor functioning even in NICU graduates without neurological impairments.Participants and Methods:We included 95 preterm (23.6 - 33.6 weeks gestation) preschoolers (49 females, 44 members of twin pairs or triplets). The participants' age ranged from 3.3 - 4.1 years (adjusted for prematurity). ROP screening was conducted during NICU stay and rated from immature retina (0) to grade 4. Motor abilities were assessed with the Peabody Developmental Motor Scales (PDMS-2). Cases with diagnosed perinatal brain pathology (moderate to severe) or cerebral palsy were excluded from analyses.Results:We used linear mixed regression analyses with multiple gestation as a random factor. Severity of ROP was our predictor of interest, whereas socioeconomic status, sex, gestational age, and birth-weight SD served as covariates. Separate analyses were conducted using the PDMS-2 Total Motor, Fine Motor, and Gross Motor Quotients as dependent variables. ROP severity explained a unique portion of the variance in the Total Motor Quotient (F[1, 89] = 5.59, p = .02). Examination of the relationship between ROP severity and motor skill domains yielded a significant association for the Fine Motor Quotient (F[1, 89] = 6.19, p = .015) and a trend for the Gross Motor Quotient (F[1, 89] = 3.64, p = .06).Conclusions:The results of this study reveal that increase in ROP severity is linked to poorer motor skills in preterm-born preschoolers without major disabilities or perinatal diagnosis of moderate to severe brain pathology. This association was evident for both fine and gross motor skills, though only the relationship between ROP severity and the former motor index reached conventional statistical significance. Importantly, ROP severity accounted for a unique portion of the variance in motor performance, over and above the variance explained by other perinatal risk factors. This result is consistent with previous research findings indicating that ROP is linked to the occurrence of multiple, subtle hypoxemic events and 'exposure' to blood gas derangements during NICU stay in very preterm neonates who require respiratory support.

Blocking endothelial apoptosis revascularizes the retina in a model of ischemic retinopathy.

Aberrant, neovascular retinal blood vessel growth is a vision-threatening complication in ischemic retinal diseases. It is driven by retinal hypoxia frequently caused by capillary nonperfusion and endothelial cell (EC) loss. We investigated the role of EC apoptosis in this process using a mouse model of ischemic retinopathy, in which vessel closure and EC apoptosis cause capillary regression and retinal ischemia followed by neovascularization. Protecting ECs from apoptosis in this model did not prevent capillary closure or retinal ischemia. Nonetheless, it prevented the clearance of ECs from closed capillaries, delaying vessel regression and allowing ECs to persist in clusters throughout the ischemic zone. In response to hypoxia, these preserved ECs underwent a vessel sprouting response and rapidly reassembled into a functional vascular network. This alleviated retinal hypoxia, preventing subsequent pathogenic neovascularization. Vessel reassembly was not limited by VEGFA neutralization, suggesting it was not dependent on the excess VEGFA produced by the ischemic retina. Neutralization of ANG2 did not prevent vessel reassembly, but did impair subsequent angiogenic expansion of the reassembled vessels. Blockade of EC apoptosis may promote ischemic tissue revascularization by preserving ECs within ischemic tissue that retain the capacity to reassemble a functional network and rapidly restore blood supply.

The progress of prophylactic treatment in retinopathy of prematurity.

Retinopathy of prematurity (ROP) is a retinal vascular disorder frequently found in premature infants. Different therapeutic strategies have been developed to treat ROP. However, there are still many children with ROP suffering by severe limitations in vision or even blindness. Recently, ROP has been suggested to be caused by abnormal development of the retinal vasculature, but not simply resulted by retinal neovascularization which takes about 4 to 6wk after birth in premature infants. Thus, instead of focusing on how to reduce retinal neovascularization, understanding the pathological changes and mechanisms that occur prior to retinal neovascularization is meaningful, which may lead to identify novel target(s) for the development of novel strategy to promote the healthy growth of retinal blood vessels rather than passively waiting for the appearance of retinal neovascularization and removing it by force. In this review, we discussed recent studies about, 1) the pathogenesis prior to retinal neovascularization in oxygen-induced retinopathy (OIR; a ROP in animal model) and in premature infants with ROP; 2) the preclinical and clinical research on preventive treatment of early OIR and ROP. We will not only highlight the importance of the mechanisms and signalling pathways in regulating early stage of ROP but also will provide guidance for actively exploring novel mechanisms and discovering novel treatments for early phase OIR and ROP prior to retinal neovascularization in the future.

Hot Topics in Retinopathy of Prematurity.

Retinopathy of prematurity (ROP) is a condition seen in premature infants that is characterized by abnormal retinal blood vessel growth incited by relative hyperoxia and followed by hypoxia. It can have severe consequences ranging from high myopia to blindness. This article reviews recent "hot" topics related to ROP, specifically the changing incidence of ROP worldwide, the advent of predictive algorithms for screening for ROP, the emerging data behind efficacy of anti-vascular endothelial growth factor treatments for ROP, and advanced retinal imaging in children who were born premature. [Pediatr Ann. 2017;46(11):e415-e422.].

Rasip1 is essential to blood vessel stability and angiogenic blood vessel growth

Cardiovascular function depends on patent, continuous and stable blood vessel formation by endothelial cells (ECs). Blood vessel development initiates by vasculogenesis, as ECs coalesce into linear aggregates and organize to form central lumens that allow blood flow. Molecular mechanisms underlying in vivo vascular 'tubulogenesis' are only beginning to be unraveled. We previously showed that the GTPase-interacting protein called Rasip1 is required for the formation of continuous vascular lumens in the early embryo. Rasip1(-/-) ECs exhibit loss of proper cell polarity and cell shape, disrupted localization of EC-EC junctions and defects in adhesion of ECs to extracellular matrix. In vitro studies showed that Rasip1 depletion in cultured ECs blocked tubulogenesis. Whether Rasip1 is required in blood vessels after their initial formation remained unclear. Here, we show that Rasip1 is essential for vessel formation and maintenance in the embryo, but not in quiescent adult vessels. Rasip1 is also required for angiogenesis in three models of blood vessel growth: in vitro matrix invasion, retinal blood vessel growth and directed in vivo angiogenesis assays. Rasip1 is thus necessary in growing embryonic blood vessels, postnatal angiogenic sprouting and remodeling, but is dispensable for maintenance of established blood vessels, making it a potential anti-angiogenic therapeutic target.

The effect of oxygen saturation targeting on retinal blood vessel growth using retinal image data from the BOOST-II UK Trial.

PurposeRetinopathy of prematurity (ROP) is a disorder of developing retinal blood vessels in preterm infants. The purpose of this nested study was to investigate the effects of higher (91–95%) and lower (85–89%) oxygen saturation (SpO2) targeting on retinal blood vessel growth in preterm infants.MethodsRetinal blood vessel growth in the higher (91–95%) and lower (85–89%) oxygen saturation (SpO2) targeting groups was compared. Suitable RetCam (Clarity, Pleasanton, CA, USA) images collected in the BOOST-II UK trial were used. The distances between the centre of the optic disc and the ROP ridge in the temporal and nasal retina were measured in pixel units.ResultsImages from 38 infants were studied, 20 from the higher SpO2 target group and 18 from the lower SpO2 target group. On average, temporal blood vessels extended further from the optic disc than nasal blood vessels, mean (standard deviation (SD)) 463.39 (55.05) pixels compared with 360.13 (44.47) pixels, respectively, P<0.0001. Temporal blood vessels extended less far from the optic disc in the higher SpO2 target group than in the lower SpO2 target group: mean (SD) 449.83 (56.16) pixels compared with 480.02 (49.94), respectively, P=0.055. Nasal retinal blood vessel measurements were broadly similar in the higher and lower SpO2 target groups; mean (SD) 353.96 (41.95) compared with 370.00 (48.82) pixels, respectively, P=0.38.ConclusionsRelatively high oxygen saturation targeting (91–95%) was associated with a trend (P=0.055) towards reduced retinal blood vessel growth in this study of preterm infants.

Laminins containing the β2 and γ3 chains regulate astrocyte migration and angiogenesis in the retina

Pathologies of retinal blood vessels are among the major causes of blindness worldwide. A key cell type that regulates retinal vascular development is the astrocyte. Generated extrinsically to the retina, astrocytes migrate into the retina through the optic nerve head. Even though there is a strong correlation between astrocyte distribution and retinal vascular development, the factors that guide astrocytes into the retina remain unclear. In this study, we show that astrocytes migrate within a laminin-containing basement membrane - the inner limiting membrane. Genetic deletion of the laminin β2 and γ3 chains affects astrocyte migration and spatial distribution. We show that laminins act as haptotactic factors in vitro in an isoform-specific manner, inducing astrocyte migration and promoting astrocyte differentiation. The addition of exogenous laminins to laminin-null retinal explants rescues astrocyte migration and spatial patterning. Furthermore, we show that the loss of laminins reduces β1 integrin expression in astrocytes. Culturing laminin-null retinal astrocytes on laminin substrates restores focal localization of β1 integrin. Finally, we show that laminins containing β2 and γ3 chains regulate subsequent retinal blood vessel growth and maintain vascular integrity. These in vivo and in vitro studies demonstrate clearly that laminins containing β2 and γ3 chains are indispensable for migration and spatial organization of astrocytes and that they play a crucial role during retinal angiogenesis in vivo.

Early retinal blood vessel growth in normal and growth restricted rat pups raised in oxygen and room air

Background/aimsPremature infants are born with incompletely vascularised retinas and are at a risk of developing retinopathy of prematurity (ROP). Rate of prenatal and postnatal body growth is important in the...

Diabetic Retinopathy and Angiogenesis

Diabetic retinopathy, a secondary microvascular complication of diabetes mellitus is the leading cause of blindness in the Unites States amongst individuals age 20 to 64. Two major retinal problems cause most of the diabetes-related vision loss: diabetic macular edema and complications from abnormal retinal blood vessel growth, angiogenesis. Secondary to angiogenesis, increased retinal blood flow is of pathogenic importance in the progression of diabetic retinopathy. Understanding the role of hyperglycemia seems to be the most critical factor in regulating retinal blood flow, as increased levels of blood glucose are thought to have a structural and physiological effect on retinal capillaries causing them to be both functionally and anatomically incompetent. High blood glucose induces hypoxia in retinal tissues, thus leading to the production of VEGF-A (vascular endothelial growth factor protein). Hypoxia is a key regulator of VEGF-induced ocular neovascularization. Secondary to the induction of VEGF by hypoxia, angiogenesis can be controlled by angiogenic inducers and inhibitors. The balance between VEGF and angiogenic inhibitors may determine the proliferation of angiogenesis in diabetic retinopathy. Since VEGF-A is a powerful angiogenic inducer, utilizing anti-VEGF treatments has proved to be a successful protocol in the treatment of proliferative diabetic retinopathy.

Early Manifestations of Postnatal Hyperoxia on the Retinal Structure and Function of the Neonatal Rat

Postnatal hyperoxia in rats causes an arrest in growth of retinal blood vessels, along with severe changes in retinal ultrastructure and function. Previous studies focused on consequences of postnatal hyperoxia at time points substantially removed from the hyperoxic insult. In this study, the earliest manifestations of this retinopathy were examined. Newborn rats were exposed to 80% O(2) from birth to postnatal day 14. The retinas were collected for vascular assessment at postnatal days 6, 9, 12, and 14, and electroretinograms were recorded at postnatal days 15, 16, 17, 19, 24, 30, and 60, after which retinal histology was performed. Hyperoxia significantly attenuated vascular development, especially after 6 and 9 days of exposure which resulted in 64% and 72% of normal coverage, respectively. Vascular growth continued despite hyperoxic exposure, reaching 87% of normal by postnatal day 14. Electroretinograms of hyperoxic rats retained very immature features throughout with nearly abolished b-waves and relatively preserved a-waves. Finally, while retinal structure was virtually complete in the control animals by postnatal day 15, hyperoxic rats always showed a significantly thinner outer plexiform layer (OPL) and lower horizontal cell count (P < 0.05), irrespective of the duration of exposure. The findings confirm previous reports of reduced retinal vascular coverage that accompanies the earliest manifestation of postnatal hyperoxia in rats and suggest increased retinal susceptibility to hyperoxia within the first week of life. However, despite the fact that vasculature appears to repair itself, irreversible cytoarchitectural and functional changes occur, the consequences of which are documented immediately after the cessation of hyperoxia.

Diabète et ischémie des membres inférieurs : bénéfice potentiel des stratégies d'angiogenèse thérapeutique

Cardiovascular complications are the leading cause of morbidity and mortality in patients with diabetes mellitus; up to 80% of deaths in patients with diabetes are closely associated with vascular disease. The ability of the organism to form a collateral network of blood vessels constitutes an important response to vascular occlusive disease and determines to a large part the clinical consequences and severity of tissue ischemia. The development of new vessels is significantly reduced in diabetic patients with coronary or peripheral artery disease. This probably contributes to the severe course of limb ischemia in diabetic patients, in which peripheral artery disease often results in foot ulceration and lower extremity amputation. Diabetic retinopathy remains one of the major causes of acquired blindness in developed nations. This is true despite the development of laser treatment, which can prevent blindness in the majority of those who develop macular edema or proliferative diabetic retinopathy. The hallmark of diabetic retinopathy is the lack of microvessels in the macula, leading to hypoxia, associated with peripheral retinal neovascularization that may ultimately cause severe vitreous cavity bleeding and/or retinal detachment. The factors that stimulate retinal blood vessel growth have not been fully defined, but there is accumulating evidence that the renin-angiotensin-bradykinin system may be involved in a number of retinal vascular disorders, including retinopathy of prematurity and proliferative diabetic retinopathy. Only a few studies have specifically evaluated the effect of diabetes on angiogenesis in ischemic vascular disease and in the retina. Moreover, the mechanisms by which diabetes could both limit the formation of new blood vessels in most organs and simultaneously induce proliferative diabetic retinopathy remain largely undefined. In the present review, we aimed to briefly describe the main molecular mechanisms involved in the ischemia-induced angiogenesis, and their alterations in diabetes. Possible therapeutic strategies to restore angiogenesis in diabetic patients are also listed.

Molecular Basis of Angiopathy in Diabetes Mellitus

See related article, pages 55–62 Cardiovascular complications are the leading cause of morbidity and mortality in patients with diabetes mellitus; up to 80% of deaths in patients with diabetes are closely associated with vascular disease. The ability of the organism to form a collateral network of blood vessels constitutes an important response to vascular occlusive disease and determines to a large part the clinical consequences and severity of tissue ischemia. The development of new vessels is significantly reduced in diabetic patients with coronary or peripheral artery disease.1,2 This probably contributes to the severe course of limb ischemia in diabetic patients, in which peripheral artery disease often results in foot ulceration and lower extremity amputation. Diabetic retinopathy remains one of the major causes of acquired blindness in developed nations. This is true despite the development of laser treatment, which can prevent blindness in the majority of those who develop macular edema or proliferative diabetic retinopathy. The hallmark of diabetic retinopathy is the lack of microvessels in the macula, leading to hypoxia, associated with peripheral retinal neovascularization that may ultimately cause severe vitreous cavity bleeding and/or retinal detachment. The factors that stimulate retinal blood vessel growth have not been fully defined, but there is accumulating evidence that the renin-angiotensin-bradykinin system (RAKS) may be involved in a number of retinal vascular disorders, including retinopathy of prematurity and proliferative diabetic retinopathy3,4 Only a few studies have specifically evaluated the effect of diabetes on angiogenesis in ischemic vascular disease and in the retina. Moreover, the mechanisms by which …

Angiogenesis and Antiangiogenesis in the Neonate: Relevance to Retinopathy of Prematurity

After completing this article, readers should be able to: 1. Delineate the major stimulus for growth of retinal blood vessels by angiogenesis in utero. 2. Describe the pathogenesis of retinal neovascularization in preterm infants. 3. List the angiogenic factors that regulate growth of new blood vessels. 4. List potential antiangiogenesis therapies. The molecular mechanisms underlying new blood vessel growth currently are being investigated in several laboratories. Angiogenesis or neovascularization has been implicated in various unrelated disease processes, such as retinopathy of prematurity (ROP), diabetic retinopathy, choroidal neovascularization, macular degeneration, and tumor angiogenesis. On the other hand, growth of new blood vessels is desired and beneficial in wound healing and myocardial and limb ischemia. All of these unrelated conditions likely share several common mechanisms in the final pathway that culminates in angiogenesis. Identification of a number of growth factors along with the ability to manipulate the mouse embryo genetically has resulted in increased understanding of the molecular mechanisms regulating angiogenesis. This review summarizes current knowledge of the factors regulating new blood vessel growth and its relevance to retinal neovascularization in preterm infants. The outer layers of the retina are supplied by the choroid plexus, which lies between the outermost layer of the retina and the retinal pigment epithelium (RPE). The inner layers are supplied by a superficial plexus beneath the inner limiting membrane and a deep plexus in the inner nuclear layer (Figs 1 and 2). Vascularization of the retina in utero, where arterial oxygen tension is less than 30 mm Hg, occurs by a process of vasculogenesis and angiogenesis. Vasculogenesis, the de novo formation of capillaries from endothelial cells that have differentiated from mesodermal precursors at approximately 16 weeks’ gestation in the posterior region around the optic disc, is seen only during embryonic development. Angiogenesis, the formation of blood vessels from existing blood vessels, …

Does my child really need to wear these glasses? a review of retinopathy of prematurity and long-term outcomes

Technological advances in neonatology create new challenges for patients, their families, and health care providers. Retinopathy of prematurity (ROP), a condition frequently seen in the premature infant, remains one of these challenges. Physiological stressors cause abnormal growth of retinal blood vessels and may result in vision loss. Common long-term sequelae include myopia, strabismus, and amblyopia; visual difficulties range from minor, correctible deficits to blindness. While research related to ROP continues, the question regarding long-term outcomes is a difficult one to answer for those families in the midst of this life-long challenge.

Retinal Neovascularization Is Prevented by Blockade of the Renin-Angiotensin System

Both angiotensin II and vascular endothelial growth factor are angiogenic agents that have recently been implicated in the pathogenesis of proliferative diabetic retinopathy. In this study, retinal neovascularization was examined in a model of retinopathy of prematurity with the use of neonatal transgenic (mRen-2)27 rats, which overexpress renin in tissues, and Sprague-Dawley rats. Blockers of the renin-angiotensin system were administered during the neovascularization period. The ACE inhibitor lisinopril and the angiotensin type 1 receptor antagonist losartan both increased retinal renin levels and prevented inner retinal blood vessel growth. Quantitative in situ hybridization revealed that the expression of vascular endothelial growth factor and its type 2 receptor in the inner retina and proliferating blood vessels were increased in rats with retinopathy of prematurity. Lisinopril reduced both retinal vascular endothelial growth factor and its type 2 receptor mRNA in retinopathy of prematurity rats, whereas losartan had no effect. It is predicted that agents that interrupt the renin-angiotensin system may play an important role as retinoprotective agents in various forms of proliferative retinopathy.

Regulation of vascular endothelial growth factor by oxygen in a model of retinopathy of prematurity.

To investigate the role of vascular endothelial growth factor (VEGF) in the pathogenesis of the first phase of retinopathy of prematurity (ROP) and to examine the mechanism by which supplemental oxygen therapy might inhibit neovascularization in the second phase of ROP. A novel combination of fluorescein-dextran perfusion and colorimetric whole-retina in situ hybridization was used to evaluate the expression of VEGF messenger RNA in relationship to the location of blood vessels in retinas from neonatal mice that were exposed to hyperoxia. Northern blot and immunoblot analyses were used to quantify the changes in VEGF messenger RNA and protein expression caused by hyperoxia. The ability of VEGF to prevent hyperoxia-induced vaso-obliteration was evaluated by injecting exogenous VEGF into the vitreous cavity prior to oxygen exposure. Vascular endothelial growth factor messenger RNA was produced in a reticular pattern just anterior to the developing blood vessels in normal retina on postnatal day 7. The expression of VEGF in the peripheral retina was down-regulated by hyperoxia in conjunction with the arrest of growth and the loss of some of the developing vasculature. Total VEGF messenger RNA and protein levels in retinas from animals on postnatal day 7 were decreased 55% and 85%, respectively, after 6 hours in 75% oxygen. Vaso-obliteration was inhibited 57% by pretreatment of animals with exogenous VEGF. In animals with retinal ischemia secondary to loss of vasculature, treatment with supplemental oxygen therapy decreased stimulated retinal VEGF levels by approximately 70%. Down-regulation of VEGF expression by hyperoxia may be partly responsible for the vaso-obliteration and cessation of normal retinal blood vessel growth observed in premature infants in whom ROP develops. Hyperoxia also has the potential to be used therapeutically to down-regulate VEGF expression in hypoxic retina in the hope of limiting the neovascular complications of ROP. Based on these findings about the regulation of VEGF expression in the retina, an explanation of the pathogenesis of ROP is proposed.