Extremely preterm infants are at increased risk for retinopathy of prematurity (ROP). We previously identified several inflammatory proteins that were expressed early in life and are associated with an increased risk of ROP and several angiogenic and neurotrophic growth factors in the neonatal systemic circulation that are associated with a lower risk of ROP. In this paper, we report the results of a set of analyses designed to test the hypothesis that placental CpG methylation levels of 12 inflammation-, angiogenic-, and neurotrophic-associated genes predict the occurrence of prethreshold ROP in extremely preterm newborns.
We used placental CpG methylation data from 395 newborns from the Extremely Low Gestational Age Newborns study.
Multivariable regression models revealed that placental DNA methylation of 16 CpG sites representing 8 genes were associated with prethreshold ROP. Specifically, CpG methylation in the serum amyloid A SAA1 and SAA2, brain-derived neurotrophic factor (BDNF), myeloperoxidase (MPO), C-reactive protein (CRP), angiopoietin 1 (ANGPT1), and tumor necrosis factor receptor superfamily member 1B (TNFRSF1B) genes was associated with a lower risk of prethreshold ROP. Conversely, CpG methylation at three probes within tumor necrosis factor receptor superfamily member 1A (TNFRSF1A) and in two alternative probes within the BDNF and ANGPT1 genes was associated with an increased risk of ROP.
CpG methylation may be a useful marker for improving ROP prediction, opening the opportunity for early intervention to lessen disease severity.
Seminars in Perinatology
Retinopathy of prematurity, visual and neurodevelopmental outcome, and imaging of the central nervous system.
Morken, T. S., Dammann, O., Skranes, J. Austeng, D.
Recent findings indicate that retinopathy of prematurity (ROP), presently classified by clinical examinations of retinal vascular tissue, is associated with structural alterations of the central nervous system. Such alterations may be the correlate of the association between ROP and impaired long-term neurocognitive and visual development. The advent of imaging techniques such as structural and diffusion tensor magnetic resonance imaging of the brain, and optical coherence tomography of the retina, will allow the complete visual system to be characterized in greater detail. It has been suggested that ROP may be not only a vascular, but a neurovascular disease, being part of a spectrum that includes pathological development in both the retinal and cerebral neurovascular interphase. We review the present knowledge in the field and point to future directions for research to tackle these questions.
Investigative Ophthalmology & Visual Science
Systemic Inflammation-Associated Proteins and Retinopathy of Prematurity in Infants Born Before the 28th Week of Gestation.
Holm, M., Morken, T. S., Fichorova, R. N., VanderVeen, D. K., Allred, E. N., Dammann, O., Leviton, A., & ELGAN Study Neonatology and Ophthalmology Committees
To assess the association between systemic levels of inflammation-associated proteins and severe retinopathy of prematurity (ROP) in extremely preterm infants.
We collected whole blood on filter paper on postnatal days 1, 7, 14, 21, and 28 from 1205 infants born before the 28th week of gestation, and measured the concentrations of 27 inflammation-associated, angiogenic, and neurotrophic proteins. We calculated odds ratios with 95% confidence intervals for the association between top quartile concentrations of each protein and prethreshold ROP.
During the first three weeks after birth, high concentrations of VEGF-R1, myeloperoxidase (MPO), IL-8, intercellular adhesion molecule (ICAM)-1, matrix metalloproteinase 9, erythropoietin, TNF-α, and basic fibroblast growth factor were associated with an increased risk for prethreshold ROP. On day 28, high levels of serum amyloid A, MPO, IL-6, TNF-α, TNF-R1/-R2, IL-8, and ICAM-1 were associated with an increased risk. Top quartile concentrations of the proinflammatory cytokines TNF-α and IL-6 were associated with increased risks of ROP when levels of neuroprotective proteins and growth factors, including BDNF, insulin-like growth factor 1, IGFBP-1, VEGFR-1 and -2, ANG-1 and PlGF, were not in the top quartile. In contrast, high concentrations of NT-4 and BDNF appeared protective only in infants without elevated inflammatory mediators.
Systemic inflammation during the first postnatal month was associated with an increased risk of prethreshold ROP. Elevated concentrations of growth factors, angiogenic proteins, and neurotrophins appeared to modulate this risk, and were capable of reducing the risk even in the absence of systemic inflammation.
Journal of Neuroinflammation
Retinopathy of prematurity: inflammation, choroidal degeneration, and novel promising therapeutic strategies
Rivera, J. C., Holm, M., Austeng, D., Sund-Morken, T., Zhou, T. E., Beaudry-Richard, A., Sierra, E. M., Dammann, O., Chemtob, S.
Retinopathy of prematurity (ROP) is an important cause of childhood blindness globally, and the incidence is rising. The disease is characterized by initial arrested retinal vascularization followed by neovascularization and ensuing retinal detachment causing permanent visual loss. Although neovascularization can be effectively treated via retinal laser ablation, it is unknown which children are at risk of entering this vision-threatening phase of the disease. Laser ablation may itself induce visual field deficits, and there is therefore a need to identify targets for novel and less destructive treatments of ROP. Inflammation is considered a key contributor to the pathogenesis of ROP. A large proportion of preterm infants with ROP will have residual visual loss linked to loss of photoreceptor (PR) and the integrity of the retinal pigment epithelium (RPE) in the macular region. Recent studies using animal models of ROP suggest that choroidal degeneration may be associated with a loss of integrity of the outer retina, a phenomenon so far largely undescribed in ROP pathogenesis. In this review, we highlight inflammatory and neuron-derived factors related to ROP progression, as well, potential targets for new treatment strategies. We also introduce choroidal degeneration as a significant cause of residual visual loss following ROP. We propose that ROP should no longer be considered an inner retinal vasculopathy only, but also a disease of choroidal degeneration affecting both retinal pigment epithelium and photoreceptor integrity.
Prethreshold retinopathy in premature infants with intrauterine growth restriction.
Lee, J. W., VanderVeen, D., Allred, E. N., Leviton, A., & Dammann, O.
To determine, among very preterm newborns, whether those who are growth-restricted are at increased risk of retinopathy of prematurity (ROP), and to explore whether the mixed findings of prior studies are the consequence of sampling based upon birthweight instead of gestational age.
Using data from the ELGAN Study, we created logistic regression models of prethreshold ROP risk to adjust for confounders and calculate odds ratios and 99% confidence intervals. We created scatter plots to display the gestational age/birthweight relationship in infants enrolled in studies with different selection criteria.
Low gestational age [23-24 weeks, OR 11.6 (2.9, 47); 25-26 weeks, 8.1 (2.1, 32)] and severe growth restriction [birthweight Z-score <-2, OR 9.1 (1.1, 76)] were associated with increased risk of prethreshold ROP. We documented in scatter plots that a sample defined by birthweight has an excess of gestationally older, severely growth-restricted newborns.
In this sample, low gestational age and severe growth restriction were associated with increased risk of prethreshold ROP.
Journal of AAPOS
Retinopathy of prematurity and brain damage in the very preterm newborn.
Allred, E. N., Capone, A Jr., Fraioli, A., Dammann, O., Droste, P., Duker, J., GIse, R., Kuban, K., Leviton, A., O’Shea, T. M., Paneth, N., Petersen, R., Trese, M., Stoessel, K., VanderVeen, D., Wallace, D. K., Weaver, G.
To explain why very preterm newborns who develop retinopathy of prematurity (ROP) appear to be at increased risk of abnormalities of both brain structure and function.
A total of 1,085 children born at < 28 weeks’ gestation had clinically indicated retinal examinations and had a developmental assessment at 2 years corrected age. Relationships between ROP categories and brain abnormalities were explored using logistic regression models with adjustment for potential confounders.
The 173 children who had severe ROP, defined as prethreshold ROP (n = 146) or worse (n = 27) were somewhat more likely than their peers without ROP to have brain ultrasound lesions or cerebral palsy. They were approximately twice as likely to have very low Bayley Scales scores. After adjusting for risk factors common to both ROP and brain disorders, infants who developed severe ROP were at increased risk of low Bayley Scales only. Among children with prethreshold ROP, exposure to anesthesia was not associated with low Bayley Scales.
Some but not all of the association of ROP with brain disorders can be explained by common risk factors. Most of the increased risks of very low Bayley Scales associated with ROP are probably not a consequence of exposure to anesthetic agents.
The immature retinas of preterm neonates are susceptible to insults that disrupt neurovascular growth, leading to retinopathy of prematurity. Suppression of growth factors due to hyperoxia and loss of the maternal-fetal interaction result in an arrest of retinal vascularisation (phase 1). Subsequently, the increasingly metabolically active, yet poorly vascularised, retina becomes hypoxic, stimulating growth factor-induced vasoproliferation (phase 2), which can cause retinal detachment. In very premature infants, controlled oxygen administration reduces but does not eliminate retinopathy of prematurity. Identification and control of factors that contribute to development of retinopathy of prematurity is essential to prevent progression to severe sight-threatening disease and to limit comorbidities with which the disease shares modifiable risk factors. Strategies to prevent retinopathy of prematurity will depend on optimisation of oxygen saturation, nutrition, and normalisation of concentrations of essential factors such as insulin-like growth factor 1 and ω-3 polyunsaturated fatty acids, as well as curbing of the effects of infection and inflammation to promote normal growth and limit suppression of neurovascular development.
Early Nutrition and Weight Gain in Preterm Newborns and the Risk of Retinopathy of Prematurity.
VanderVeen, D. K., Martin, C. R., Mehendale, R., Allred, E. N., Dammann, O., Leviton, A. ELGAN Study Investigators
To identify nutritional and weight gain limitations associated with retinopathy of prematurity (ROP) severity among very preterm newborns.
Patients and Methods: 1180 infants < 28 weeks GA at birth with ROP examination results were grouped and analysed by quartile of weekly total calorie, carbohydrate, protein, and lipid intake, as well as growth velocity between postnatal days 7 and 28 (adjusted for GA and birth weight Z-score). ROP was categorized by development of no, mild (< pre threshold), type 2, or type 1 ROP, as well as markers of ROP severity including stage 3 ROP, zone 1 disease, and plus disease. Associations between nutritional intake and ROP severity were compared.
Greater risk for Type 1 ROP (risk/95% confidence intervals) was found for infants with lowest quartile receipt of lipids (2.1/1.1, 3.8), total calories (2.2/1.4, 3.6), and carbohydrates (1.7/1.1, 2.9). Development of zone 1 ROP was associated with lipid or total calorie intake in the lowest quartile, and development of stage 3 ROP was associated with lowest quartile of total calorie intake. Growth velocity in the lowest quartile was associated with increased risk of any ROP, including type 1 ROP.
The risk of developing severe ROP in extremely premature infants might be reduced by improving nutritional support, specifically targeting lipids and total calories, and perhaps by improving weight gain.
The Journal of Maternal-Fetal & Neonatal Medicine
Pregnancy disorders appear to modify the risk for retinopathy of prematurity associated with neonatal hyperoxemia and bacteremia.
Lee, J. W., McElrath, T., Chen, M., Wallace, D. K., Allred, E. N., Leviton, A., & Dammann, O.
To explore (1) whether extremely low gestational age newborns exposed to inflammation-associated pregnancy disorders differ in retinopathy of prematurity (ROP) risk from infants exposed to placenta dysfunction-associated disorders, and (2) whether ROP risk associated with postnatal hyperoxemia and bacteremia differs among infants exposed to these disorders.
Pregnancy disorders resulting in preterm birth include inflammation-associated: preterm labor, prelabor premature rupture of membranes (pPROM), cervical insufficiency, and abruption and placenta dysfunction-associated: preeclampsia and fetal indication. The risk of severe ROP associated with pregnancy disorders was evaluated by multivariable analyses in strata defined by potential effect modifiers, postnatal hyperoxemia and bacteremia.
Compared to preterm labor, infants delivered after pPROM were at reduced risk of plus disease (Odds ratio = 0.4, 95% confidence interval: 0.2-0.8) and prethreshold/threshold ROP (0.5, 0.3-0.8). Infants delivered after abruption had reduced risk of zone I ROP (0.2, 0.1-0.8) and prethreshold/threshold ROP (0.3, 0.1-0.7). In stratified analyses, infants born after placenta dysfunction had higher risks of severe ROP associated with subsequent postnatal hyperoxemia and bacteremia than infants born after inflammation-associated pregnancy disorders.
Infants exposed to placenta dysfunction have an increased risk of severe ROP following postnatal hyperoxemia and bacteremia compared to infants exposed to inflammation-associated pregnancy disorders.
Seminars in Fetal & Neonatal Medicine
Perinatal infection, inflammation, and retinopathy of prematurity.
The major known risk factors for retinopathy of prematurity (ROP) are extremely low gestational age, exposure to high levels of oxygen early after birth (phase I) and relatively lower oxygen levels later (phase II). In this review, we summarize recent data suggesting that exposure to perinatal infection/inflammation is associated with an increased risk for ROP. Part of this effect might be due to direct exposure of the developing retina to circulating products of infection and/or inflammation. Another potential mechanism that deserves exploration is that inflammation and/or oxidative stress can modify the known increased risk of oxygen-associated ROP. Taken together, accumulating evidence suggests that prenatal, perinatal, and postnatal systemic inflammation contribute to a 'pre-phase', sensitizing the pre-ROP retina for subsequent insults, setting the stage for what are now called phase I and phase II of ROP pathogenesis. Strategies targeting inflammatory responses might help reduce the risk for ROP in extremely low gestational age newborns.
Retinopathy of prematurity (ROP) is a disorder of retinal vasoproliferation that occurs mainly in extremely preterm infants . The long-term visual outcome among children with ROP includes a prominently increased risk of a range of visual disabilities . Understanding the etiology and pathogenesis of ROP is crucial for the design of strategies to prevent and treat this potentially disabling disease.
Less than a decade ago, one review included the statement “only low birth weight, low gestational age, and supplemental oxygen therapy following delivery have been consistently associated with disease” . This statement was made despite the recognition by others that other antecedents might be important, including insufficient levels of vitamin E, indomethacin treatment for patent ductus arteriosus, hypercapnia, maternal aspirin use, and transfusion of blood and blood products or the need for such transfusions .
While immaturity at birth and exposure to supplemental oxygen unquestionably play important etiologic roles in ROP , the possibility that exposures to infectious and inflammatory stimuli contribute to ROP is only gradually receiving attention. As recently as 2003 one review included the statement that “the relationships between infections and the development of ROP remain unclear” , while another stated that “the role of an inflammatory reaction in the pathophysiology of ROP has not been thoroughly investigated” .
Exposure to infection and elevated concentrations of inflammation-related proteins in the placenta and/or neonatal body fluids are associated with an increased risk for preterm delivery , respiratory dysfunctions , as well as brain damage and subsequent disability among preterm infants . This concept that fetal/neonatal inflammation has adverse effects has been expanded to include ROP and other visual disturbances in preterm infants . Indeed, some of the data in papers discussed below support the impression that ROP pathogenesis begins in utero.
Archives of Ophthalmology
Neonatal bacteremia and retinopathy of prematurity: the ELGAN study.
Tolsma, K. W., Allred, E. N., Chen, M. L., Duker, J., Leviton, A., & Dammann, O.
OBJECTIVE: To explore whether early or late and presumed or definite neonatal bacteremia are associated with an increased risk of severe retinopathy of prematurity (ROP).
METHODS: We evaluated 1059 infants born before week 28 of gestation for ROP. Infants were classified as having early (postnatal week 1) or late (weeks 2-4) definite (culture-proven) or presumed (antibiotics taken for >72 hours despite negative blood culture results) bacteremia. Severe ROP was defined as stage 3 to 5, zone 1, pre-threshold/threshold, or plus disease. We used time-oriented risk models to adjust for confounders.
RESULTS: In univariable, but not multivariable, analysis, newborns with presumed early bacteremia were at increased risk for plus disease (odds ratio [OR], 1.7; 95% CI, 1.1-2.7), and those with definite early bacteremia were at increased risk for stage 3 to 5 disease (1.9; 1.1-3.2). Infants who had presumed or definite late bacteremia were at increased risk for all 4 indicators of severe ROP in univariable analysis. In multivariable analysis, newborns with presumed late bacteremia were at increased risk for pre-threshold/threshold ROP (OR, 1.8; 95% CI, 1.02-3.2), and those with definite late bacteremia were at increased risk for pre-threshold/threshold ROP (1.8; 1.1-2.9) and plus disease (1.8; 1.05-2.9).
CONCLUSIONS: Definite late neonatal bacteremia seems to be an independent risk factor for pre-threshold/threshold ROP and plus disease, and presumed late bacteremia seems to be related to pre-threshold/threshold ROP.
Investigative Ophthalmology & Visual Science
Placenta Microbiology and Histology and the Risk for Severe Retinopathy of Prematurity.
Chen, M. L., Allred, E. N., Hecht, J. L., Onderdonk, A., VanderVeen, D., Wallace, D. K., Leviton, A., Dammann, O., & ELGAN Study
Purpose: To test the hypothesis that the presence of bacteria and/or histologic inflammation in the placenta of infants born preterm is associated with an increased risk for severe retinopathy of prematurity (ROP).
Methods: This was a prospective cohort study. Exploratory and multivariable data analyses were used, including logistic regression models with interaction terms. Main outcomes were four definitions of severe ROP: stage 3 or higher, any ROP in zone I, pre-threshold/threshold, and plus disease.
Results: Individually, placenta bacteria and histologic inflammation were not associated with severe ROP in univariable analyses among 1064 infants with gestational age <28 weeks or among 715 infants with gestational age <27 weeks (we excluded infants with a gestational age of 27 weeks because of the very small number of ROP cases). However, the co-occurrence of bacteria and inflammation was associated with an increased risk for ROP in zone I (odds ratio, 3.1; 95% confidence interval, 1.02–9.5). Among 339 infants with any placental bacteria, the co-occurrence of (1) inflammation and a gestational age of 23 to 24 weeks and (2) inflammation and hyperoxia were associated with prominent increases in risk for all definitions of severe ROP.
Conclusions: While antenatal exposure to infection or inflammation alone does not appear to convey risk information for severe ROP, their co-occurrence does. This finding supports the hypothesis that a fetal inflammatory response to antenatal infection might be part of the etiology of severe ROP.
Blood gases and retinopathy of prematurity: the ELGAN Study.
Hauspurg, A. K., Allred, E. N., Vanderveen, D. K., Chen, M., Bednarek, F. J., Cole, C., Ehrenkranz, R. A., Leviton, A., & Dammann, O.
OBJECTIVE: This study tested the hypothesis that preterm infants who had a blood gas derangement on at least 2 of the first 3 postnatal days are at increased risk for more severe retinopathy of prematurity (ROP).
METHOD: 1,042 infants born before 28 weeks' gestational age (GA) were included. An infant was considered to be exposed if his/her blood gas measure was in the highest or lowest quartile for GA on at least 2 of the first 3 postnatal days.
RESULTS: Multivariable models adjusting for confounders indicate that exposure to a PCO(2) in the highest quartile predicts ROP (stage 3, 4 or 5: OR = 1.6, 95% CI = 1.1-2.3); zone 1: 2.0, 1.1-3.6; pre-threshold/threshold: 1.9, 1.2-3.0; plus disease: 1.8, 1.1-2.9). Estimates are similar for a low pH for zone 1 (2.1, 1.2-3.8), pre-threshold/threshold (1.8, 1.1-2.8), but did not quite achieve statistical significance for ROP stage 3, 4, or 5 (1.4, 0.9-2.0) and plus disease (1.5, 0.9-2.4). A PaO(2) in the highest quartile for GA on at least 2 of the first 3 postnatal days was associated with a doubling of the risk of ROP in zone 1 (2.5, 1.4-4.4) and of pre-threshold/threshold disease (2.1, 1.4-3.3), a 70% risk increase for plus disease (1.7, 1.04-2.8), while a 40% risk increase for ROP stage 3 or higher did not achieve statistical significance (1.4, 0.96-2.0).
CONCLUSION: Infants exposed to high PCO(2), low pH and high PaO(2) appear to be at increased risk of more severe ROP.
Infection, oxygen, and immaturity: interacting risk factors for retinopathy of prematurity.
Chen, M., Citil, A., McCabe, F., Leicht, K. M., FIascone, J., Dammann, C. E., & Dammann, O.
BACKGROUND: Interactions among known risk factors for retinopathy of prematurity (ROP) remain to be clarified.
OBJECTIVES: The aim of this study was to identify risk factors associated with ROP and to explore the interrelationships between prominent risk factors for ROP.
METHODS: From an institutional cohort of 1,646 very preterm newborns with gestational age <30 weeks or birth weight <1,501 g, we selected infants with a gestational age <30 weeks who met the criteria for ROP screening (n = 622) for a nested case-control analysis.
RESULTS: Of the 622 eligible newborns, 293 (47%) were diagnosed with ROP. From multivariable analyses, gestational age <26 weeks (OR 2.9, CI 1.7-4.9), oxygen exposure at 28 days (OR 1.7, CI 1.0-2.7), and neonatal sepsis (OR 2.1, CI 1.4-3.2) emerged as prominent risk factors for ROP. Oxygen- associated ROP risk was more prominent among infants of 23-25 weeks' gestational age, while infection-associated ROP risk was higher among infants born at 28-29 weeks. The OR for the joint effect of all 3 risk factors (23.5) was higher than would have been expected under the additive (8.6) and the multiplicative (16.5) patterns of interaction.
CONCLUSIONS: Our study suggests that neonatal sepsis, oxygen exposure, and low gestational age are not only independently associated with a significantly increased risk of ROP, but also interact beyond additive and even multiplicative patterns.
High or low oxygen saturation and severe retinopathy of prematurity: a meta-analysis.
Chen, M. L., Guo, L., Smith, L. E., Dammann, C. E., Dammann, O.
CONTEXT: Low oxygen saturation appears to decrease the risk of severe retinopathy of prematurity (ROP) in preterm newborns when administered during the first few weeks after birth. High oxygen saturation seems to reduce the risk at later postmenstrual ages (PMAs). However, previous clinical studies are not conclusive individually.
OBJECTIVE: To perform a systematic review and meta-analysis to report the association between severe ROP incidence of premature infants with high or low target oxygen saturation measured by pulse oximetry.
METHODS: Studies were identified through PubMed and Embase literature searches through May 2009 by using the terms "retinopathy of prematurity and oxygen" or "retinopathy of prematurity and oxygen therapy." We selected 10 publications addressing the association between severe ROP and target oxygen saturation measured by pulse oximetry. Using a random-effects model we calculated the summary-effect estimate. We visually inspected funnel plots to examine possible publication bias.
RESULTS: Low oxygen saturation (70%-96%) in the first several postnatal weeks was associated with a reduced risk of severe ROP (risk ratio [RR]: 0.48 [95% confidence interval (CI): 0.31-0.75]). High oxygen saturation (94%-99%) at > or = 32 weeks' PMA was associated with a decreased risk for progression to severe ROP (RR: 0.54 [95% CI: 0.35-0.82]).
CONCLUSIONS: Among preterm infants with a gestational age of < or = 32 weeks, early low and late high oxygen saturation were associated with a reduced risk for severe ROP. We feel that a large randomized clinical trial with long-term developmental follow-up is warranted to confirm this meta-analytic result.
Early Human Development
Immaturity, perinatal inflammation, and retinopathy of prematurity: a multi-hit hypothesis.
Dammann, O., Brinkhaus, M. J., Bartels, D. B., Dördelmann, M., Dressler, F., Kerk, J., Dörk, T., & Dammann, C. E.
OBJECTIVE: To explore the relationship among markers of infection/inflammation in their association with retinopathy of prematurity (ROP).
METHODS: We studied clinical characteristics and 4 single nucleotide polymorphisms in infection/inflammation-associated genes in a group of 73 children with a gestational age < 32 weeks. Forty-four children (60%) had ROP, of whom 13 (30% of those with ROP) progressed to stage 3 ROP. No child had grade 4 or 5 ROP. We employed both descriptive and analytic statistical methods.
RESULTS: Clinical variables of infection/inflammation were consistently associated with an increased risk of ROP. Among infants with ROP, they were also associated with progression to ROP grade 3. Genetic markers were not associated with ROP occurrence, but with progression to high grade disease. In tri-variable analyses exploring the effects of gestational age < 29 weeks, clinical chorioamnionitis (CAM) and neonatal systemic inflammatory response syndrome (SIRS) on ROP occurrence, low gestational age was the most important antecedent, while additional individual or joint exposure to SIRS and CAM add appreciably to this risk of progression to high grade disease.
CONCLUSION: Both antenatal and neonatal exposure to inflammation appear to contribute to the increased ROP risk in preterm infants.
An Affiliation of TUFTS UNIVERSITY, School of Public Health and Community Medicine