Pups from other litters were used to supplement deficient litters
Pups from other litters were used to supplement deficient litters. vascularized in the model but fully vascularized in RA, VEGF164expression was threefold greater in the model compared to RA. On p18, intravitreous neovascularization was associated with a 5-fold increase in VEGF164mRNA in the model compared to RA. By analysis of variance, VEGF164and VEGFR2 mRNAs were up-regulated in association with increasing developmental age (P<.0001 for both comparisons) or exposure to the model compared to RA (P<.0001 andP=.0247, respectively), whereas increasing developmental age was associated only with up-regulated VEGF120(P=.0006), VEGF188(P=.0256), and VEGFR1 (P<.0001) mRNAs. VEGF protein increased significantly in the model and on p14 and p18 compared to RA (P<.0001). == Conclusions: == The model mimics contemporary severe ROP in the United States unlike other models of oxygen-induced retinopathy. Compared to RA retinas, VEGF significantly increased in association with avascular retina and intravitreous neovascularization. A hypothesis is usually proposed that VEGF up-regulation plays a role in the development of both important features. == INTRODUCTION == Retinopathy of prematurity PP242 (Torkinib) (ROP) affects about 16,000 preterm infants in the United States annually. Of these, 1,100 infants require treatment, and blindness is usually estimated to develop in 550.1,2ROP is one of the earliest and the most prevalent causes of visual impairment in children in the United Says3and a leading cause of childhood blindness worldwide.4 Preterm birth results in incomplete retinal vascular development and areas of peripheral avascular retina. In ROP, changes at the junction of the vascularized retina and the peripheral avascular region can lead to the growth of blood vessels into the vitreous and later a fibrovascular tractional PP242 (Torkinib) retinal detachment. An early hypothesis proposed by Michaelson,5Ashton and Cook,6and Patz and associates7posed that an angiogenic factor or factors were involved. Studies within the last decades have identified several factors, most notably vascular endothelial growth factor (VEGF). Since the early description and understanding of ROP, 57technological advances have permitted monitoring and regulation of oxygen to the preterm infant. Yet, most animal models now used to study the pathophysiology of severe ROP deliver very high and constant oxygen, no longer pertinent to most cases of severe ROP in locations that have implemented the technology to monitor and regulate oxygen. This thesis uses an animal model representative of peripheral severe ROP (rat 50/10 OIR model) to better understand the role of contemporary oxygen stresses around the expression of angiogenic factors in developmental angiogenesis, neovascularization into the vitreous, and peripheral avascular retina. In this thesis, specifically, the expression of VEGF and its receptors was decided in the rat 50/10 OIR model and in room airraised pups at the same developmental ages. The following hypotheses were resolved: (1) that at the developmental age when retinal vascularization was incomplete in the 50/10 OIR model but complete in room air, VEGF would be relatively down-regulated in the 50/10 OIR model compared to room air, and (2) that when Alas2 neovascularization into the vitreous occurred, VEGF would be up-regulated in the 50/10 OIR model compared to age-matched pups raised in room air. Based on the analyses and literature review, a refined hypothesis is presented to explain why blood vessels grow into the vitreous in severe ROP and not into the retina as occurs in natural retinal vascular development. If blood vessel growth were redirected from the vitreous into the retina in the preterm infant, this strategy would reduce blindness from ROP, improve blood flow and nutrition to the peripheral avascular retina, and potentially improve visual field. The thesis first reviews what is currently known about ROP and its evolution and then presents a study to test the hypotheses above. Following the results, a refined hypothesis is usually presented and discussed. == CLINICAL ASPECTS OF ROP == == Impact == Preterm births have increased 30% since 1981 and now account for almost 12.5% of all births in the United States.2In developing countries worldwide, ROP is now a leading cause of childhood blindness. 4Besides the deserving goal of preventing blindness in even a few infants, there are also substantial benefits in reducing medical and societal costs associated with raising blind children to adulthood.8 == Classification and Management of ROP == Although controversy exists regarding the exact mechanisms in the human infant, retinal vascular development is believed to begin adjacent to the optic nerve through a process of vasculogenesis, in which circulating angioblasts develop early retinal vessels in the region surrounding the optic nerve. From these initial blood vessels, angiogenesis then proceeds to extend the retinal vasculature to the ora serrata. Angiogenesis includes processes of proliferation and migration of endothelial cells toward a PP242 (Torkinib) gradient and the.