Oral Propranolol Versus Placebo for Early Stages of Retinopathy of Prematurity: A Randomized and Prospective Study
Oral Propranolol Versus Placebo for Early Stages of Retinopathy of Prematurity: A Randomized and Prospective Study
In premature infants, propranolol (Prop) treatment might suppress continuing
 neo-vascularization (NV) and decelerate the progression of retinopathy of prematurity (ROP)
 towards its severe stages (III-V), thus avoiding the need of interventions (CRYO and/or LASER
 photo-coagulation of the ischemic retina and preventing severe ocular sequelae. We therefore
 plan to prospectively investigate the influence of prop versus placebo in VLBW infants with
 ROP stage 1 (zone I), with stage 2 or higher (any zone) or with Plus disease, along with
 close follow up regarding safety of prop administration and its effect on ROP.
Retinopathy of prematurity (ROP) affects the retinal microvasculature, mostly of
 very-low-birth-weight (VLBW: < 1500g) premature infants, and is a significant complication of
 extreme prematurity leading sometimes to devastating consequences. Although ROP is usually
 mild with no harm, it happens not very rarely to be aggressive causing neo-vascularization
 (NV) in the immature retina that at times can progress to severe fibrovascular proliferation,
 retinal detachment and blindness (1). Major risk factors for ROP are low gestational age, low
 birth weight, hyperoxia, respiratory distress syndrome (RDS) and intraventricular hemorrhage
 (IVH) (2) as well as postnatal steroid therapy (3). Of note is one report showing that the
 use of beta-blocking agents by the mother before birth was found to be associated with the
 development of ROP (4). However, so far no one reported a similar effect of the postnatal use
 of beta blockers on ROP.

 The incidence of ROP is inversely related to gestational age (GA) and birth weight (BW). The
 condition develops in 51% of infants with a birth weight (BW) <1700 g (5). In infants
 weighing less than 1250 g, 50% show some evidence of ROP and 10% progress to stage III ROP.
 According to the Israeli VLBW-Database in 2007, 23.9% of infants develop ROP (all stages),
 while 4.8% develop severe ROP (stage III-IV) (4). Worldwide, at least 50,000 children are
 blind from ROP (2,7). In South Africa it accounts for 10.6% of cases of childhood blindness
 (8). In the US, annually, 500-700 children become blind due to ROP, and 2100 infants will be
 affected by cicatricial sequelae, such as myopia, strabismus, as well as late-onset retinal
 detachment (1).

 LASER photocoagulation of the ischemic retina is the therapy of choice for moderate to severe
 ROP and is required in 19.8%, 7.7%. 1.5% and 0.6% of infants weighing 500-749g, 750-999g,
 1000-1249g, 1250-1499g, respectively (2). In Israel, 4% of VLBW infants needed LASER
 photocoagulation or cryo therapy during 2007 (6).

 The pathogenesis of ROP is multifactorial and two pathogenetic theories have been proposed:

 (A) One-phase theory: Mesenchymal spindle cells when exposed to extrauterine hyperoxia,
 develop gap junctions that interfere with normal vascular formation and trigger a neovascular
 response (9).

 (B) Two-phase theory: The first phase (hyperoxic phase, vaso-obliterative), consists of
 retinal vasoconstriction and irreversible capillary endothelial cell damage. As the retinal
 area that is supplied by the affected vessels becomes ischemic, angiogenic factors, such as
 vascular endothelial growth factor (VEGF) are produced by mesenchymal spindle cells in that
 ischemic retina to provide neo vascularization (NV) channels (second phase,
 vaso-proliferative)(10).

 Increasing evidence supports the key role of VEGF in the pathogenesis of ROP, wherein VEGF is
 down-regulated in the vaso-obliterative first phase and up-regulated in the
 vaso-proliferative second phase (11). Numerous studies have been performed in an animal model
 of oxygen-induced retinopathy (OIR), wherein newborn rats, mice, kitten and beagle puppies
 were exposed to 75-100% O2 for 5 days starting at day 7 of life (11). ROP usually develops in
 100% of the O2-exposed rats (12).

 The expression of various angiogenetic and inflammation genes has been studied in
 oxygen-induced retinopathy (OIR). Sato et al (13) investigated the expression of 94 genes in
 OIR using microarray analysis and reverse transcriptase-polymerase chain reaction (RT-PCR).
 They observed that: (a) Inflammation genes were up-regulated at days 12-13 of life when the
 degree of both central avascular area and central vasoconstriction were maximal; this
 up-regulation continued until day 21 of life; (b) Extra retinal vascularization was most
 noticeable at days 16-17 of life, when angiogenesis genes (VEGF-A, angiopoietin-2) were at
 their highest expression.

 There is also increasing evidence of up-regulation of VEGF by sympathomimetic agents. In this
 regard, norepinephrine has been shown to stimulate myocardial angiogenesis in rats (14). In
 cultured retinal endothelial cells, Steinle et al (15) showed that significantly increased
 expression of beta-3 receptors could promote migration and proliferation (two markers of
 angiogenic phenotype) of retinal endothelial cells.

 In addition, in cancer cell cultures, catecholamines (norepinephrine and epinephrine) induced
 an increase of VEGF expression in a tissue culture of nasopharyngeal carcinoma, an effect
 that was blocked by propranolol (prop) (a non-selective beta blocker) (16). Evidence exists
 for norepinephrine-induced invasiveness with increased VEGF in human pancreatic cell lines,
 could also be blocked by prop (17). Blockade of these effects by prop raised the prospects of
 a possible chemo-prevention of vascularization-rich tumors by propranolol.

 Recent studies have shown that administration of beta-blockers (both locally and systemic)
 can mitigate NV, probably by down regulation of VEGF. In an animal model of OIR, topical
 timolol (a beta blocker) prevented the development of OIR in 40% of rats and mitigated the
 severity of OIR in the remaining 60% of rats that had developed OIR (12,18). In addition,
 timolol had a protective effect, whereby NV occurred in 65% of timolol-treated as compared to
 100% NV in untreated rats (19). Furthermore, VEGF expression was lower in timolol-treated
 rats than in controls (room air). In contrast, Zheng et al (20) found no effect of prop on
 the VEGF protein and on messenger ribonucleic acid (mRNA) expression in the retina of
 diabetic rats with retinopathy.

 ROP and infantile hemangiomas (a rather common phenomena in premature infants) supposedly
 share the same pathogenetic role of angiogenic factors such as VEGF (21). In a recent report
 by Praveen et al (22), a possible association between ROP and infantile hemangiomas at
 discharge was studied in premature infants weighing <1250 g. Infantile hemangiomas were found
 to be independently associated with any stage of ROP: infantile hemangiomas were present in
 16.8% of neonates with ROP as compared with 6.7% of those without ROP. However, neither the
 size nor the number of infantile hemangiomas showed any association with the severity of ROP.

 The above-mentioned published findings point to a VEGF-mediated pathogenesis of both ROP and
 infantile hemangiomas, wherein VEGF expression is reportedly up-regulated by sympathomimetic
 agents and blocked by beta blockers. Furthermore, on the clinical scene, the usefulness of
 prop in mitigating the progression of infantile hemangiomas has been recently reported
 (23-32). Infants with severe or life-threatening hemangiomas were successfully treated with
 prop, with no adverse effects. One potential explanation for the effect of prop on
 hemangiomas includes: (a) vasoconstriction, or (b) decreased expression of VEGF and basic
 fibroblast growth factor (bFGF) genes through the down-regulation of RAF-mitogen-activated
 protein kinase pathway (33) (which explains the progressive improvement of hemangioma), or
 (c) a triggering of capillary endothelial cells apoptosis (34).

 Prop administration has been observed to be safe in infants and toddlers (23-32, 35). Love et
 al (35) found that after 40 years of clinical use in infants and toddlers, there is no
 documented case of death or serious cardiovascular disease as a direct result of exposure to
 beta-blockers. Furthermore, prop was also reported to be safe when given to premature infants
 for treatment of neonatal thyrotoxicosis, neonatal arrhythmia or life-threatening hemangioma
 (32, 36-39). In five extreme-low-birth weight infants (weight <1000 g), the use of prop for
 neonatal thyrotoxicosis was beneficial and had no adverse effects (36). The safety of prop
 use was also reported in a 34-week infant (37) and a for 37-week infant (38) with
 thyrotoxicosis, and also in a 35-week infant with neonatal arrhythmia (39). Furthermore, a
 28-week premature infant was treated for18 weeks with prop for a thoracic hemangioma without
 untoward effects (32).
Inclusion Criteria:

 Evidence for ROP that might progress and that includes any one of the following:

 -  Stage 1 (zone I)

 -  Stage 2 or higher (zones I, II or III), or Plus disease. The classification of ROP is
 according to International Classification of Retinopathy of Prematurity (ICROP) 2005
 (40) (Appendix I, with scheme of retina showing zones and clock hours).Zone III ROP is
 not included since it will always regress spontaneously.

 Exclusion Criteria:

 -  The presence of one or more of the following conditions at enrollment in the study:

 -  More than 10 episodes of bradycardia of prematurity/day (HR< 90 bpm) [

 -  Atrio-ventricular (A-V) block [2nd or 3rd degree]

 -  Significant congenital heart anomaly [not including patent ductus arteriosus, patent
 foramen ovale or small ventricular septal defect]

 -  Heart failure

 -  Hypotension (mean blood pressure <45 mmHg)

 -  Hypoglycemia (<50mg/dL)

 -  Platelet count <100000/mm3