Erythropoietin protects the developing retina in an ovine model of endotoxin-induced retinal injury.

PURPOSE: Intrauterine infection is a common antecedent of preterm birth. Infants born very preterm are at increased risk for neurologic dysfunction, including visual deficits. With increasing survival of very preterm infants, there is a need for therapies that prevent adverse neurologic outcomes. Using an ovine model, the authors investigated the neuroprotective potential of recombinant human erythropoietin (rhEPO) on retinal injury induced by intrauterine inflammation. METHODS: At 107 ± 1 days of gestational age (DGA), chronically catheterized fetal sheep received either of the following on 3 consecutive days: intravenous (IV) bolus dose of lipopolysaccharide (LPS; ∼0.9 µg/kg; n = 8); IV bolus dose of LPS, followed at 1 hour by 5000 IU/kg rhEPO (LPS + rhEPO; n = 8); rhEPO alone (n = 5). Untreated fetuses (n = 8) were used for comparison with the three treatment groups. Fetal physiological parameters were monitored. At 116 ± 1 DGA, fetal retinas were assessed quantitatively for morphologic and neurochemical alterations. RESULTS: Exposure to LPS alone, but not to rhEPO alone, resulted in fetal hypoxemia and hypotension (P < 0.05). Exposure to LPS alone caused retinal changes, including reductions in thickness of the inner nuclear layer (INL), somal areas of INL neurons, process growth in the plexiform layers, and numbers of ganglion and tyrosine hydroxylase immunoreactive (TH-IR) dopaminergic amacrine cells. Treatment of LPS-exposed fetuses with rhEPO did not alter the physiological effects of LPS but significantly reduced alterations in retinal layers and ganglion and TH-IR cell numbers. CONCLUSIONS: rhEPO treatment was beneficial in protecting the developing retina after LPS-induced inflammation. Retinal protection could occur by the antiapoptotic or anti-inflammatory actions of EPO.

Cerebellar development in a baboon model of preterm delivery: impact of specific ventilatory regimes.

Premature infants now have an improved chance of survival, but the impact of respiratory therapies on the brain, particularly the cerebellum, remains unclear. We examined the effects of early nasal continuous positive airway pressure (EnCPAP) ventilation and delayed (Dn) CPAP on the development of the cerebellum in prematurely delivered baboons. The baboons were delivered at 125 +/- 2days of gestation and ventilated for 28 days with either EnCPAP commencing at 24 hours (n = 5) or DnCPAP commencing at 5 days (n = 5). Gestational controls (n = 4) were delivered at 153 days. Cerebella were assessed histologically, and an ontogeny study (90 days to term) was performed to establish values for key cerebellar developmental indicators. Cerebellar weight was reduced in DnCPAP but not EnCPAP animals versus controls; cerebellar/total brain weight ratio was increased in EnCPAP (p < 0.05) versus control and DnCPAP animals. There was no overt damage in the cerebella of any animals, but a microstructural alteration index based on morphological developmental parameters and microglial immunoreactivity was increased in both prematurely delivered cohorts versus controls (p < 0.001) and was higher in DnCPAP than EnCPAP animals (p < 0.05). These results indicate that respiratory regimens can influence cerebellar development and that early compared with delayed extubation to nCPAP seems to be beneficial.

BDNF increases survival of retinal dopaminergic neurons after prenatal compromise.

PURPOSE: Chronic placental insufficiency (CPI) severe enough to cause growth restriction (GR) results in alterations to the retina, including a reduction in tyrosine hydroxylase immunoreactive (TH-IR)-dopaminergic amacrine cells. Brain-derived neurotrophic factor (BDNF) plays a role in the development of the retinal dopaminergic network and may therefore be an appropriate therapy for restoring dopaminergic cells after prenatal compromise. This study was conducted (1) to establish whether BDNF and its receptor NTRK2 (Trk B) are altered in the retina after CPI and (2) to explore the potential of BDNF to enhance dopaminergic cell survival in organotypic retinal cultures from prenatally compromised animals. METHODS: CPI was induced in pregnant guinea pigs at 30 days' gestation (dg; term, approximately 67 dg) via unilateral ligation of the uterine artery. Fetuses were euthanatized at 60 dg and the retinas prepared for enzyme-linked immunosorbent assay (ELISA) analysis of BDNF protein levels and for immunohistochemistry to localize BDNF and NTRK2. Organotypic cultures of retinas from GR and control fetuses at 50 to 52 dg were treated with BDNF, and dopaminergic amacrine cells counts were assessed. RESULTS: Retinal BDNF protein levels and the intensity of BDNF-immunoreactivity (IR) in the ganglion cell layer were reduced (P < 0.05) in GR fetuses compared with control fetuses. Addition of BDNF to organotypic cultures increased (P < 0.05) the survival and neurite growth of dopaminergic neurons from both control and GR fetuses. CONCLUSIONS: Alterations to BDNF levels may underlie reductions in dopaminergic amacrine cells observed after CPI. The addition of BDNF has the potential to increase survival and neurite growth of dopaminergic amacrine cells.