Abstract 2008 Perinatal Brain Injury: Patterns and Mechanisms Platform, Tuesday, 5/4

Background: Association between intrauterine infection and brain white matter diseases in preterm neonates is suggested by clinical studies. Apoptotic cell death seems to play an important role in these cerebral lesions. Experimental models could be useful to explain this association and to test neuroprotective therapies. Recently, one was developed in the rabbit but cerebral apoptosis was present in only 6% of live fetuses (Yoon BH, Am J Obstet Gynecol 1997; 177: 797-802). Aim: To develop a new model of cerebral apoptosis by intrauterine infection with a better reproductibility. Methods: Timed-pregnant rabbit infection was performed at 24-30 days of a 33 day gestation. Under analgesia, during laparotomy, we injected 1ml of E Coli inoculum (104CFU/ml) into intrauterine horn. Then, two phases of experiments were conducted: first, cesarean section (C-section) was carried out at different times after inoculation (H12, H24, H48) in pregnant rabbits not treated with antibiotics (Group A). In the second phase, animals were treated with ceftriaxone IV (100mg/kg/day) at 24 hours after inoculation and C-section was made 24 hours after the start of this therapy (Group B). After delivery, maternal and fetal blood culture were performed. Brain study was conducted only in live-fetuses. Apoptotic brain cells were identified by morphologic criteria and by presence of DNA fragmentation using TUNEL method. Results: In group A, 14 pregnant rabbits were inoculated and all had positive blood culture at the time of cesaerean. In this group, all the rabbits born at H48 after inoculation (n = 27) were stillborn with positive blood culture and no brain study could be performed. For rabbits delivered at H24 (n = 60) and H12 (n = 51) after inoculation, the rate of positive blood culture was 87% and 82% respectively but the rate of infected and live fetuses was 37% and 66%. For these, no apoptotic cells were found at histologic examination. In group B, 2 pregnant rabbits were inoculated and treated at H24 after inoculation. 19 rabbits were born and 42% were live fetuses at delivery. All had apoptosis brain cells at histologic examination and there were located in the periventricular regions and cortex area. This result was confirmed by the presence of DNA fragmentation in the same regions. Conclusion: Brain white matter apoptosis is consistently obtained in 100% of live fetuses with a delay of 48 hours after the start of intrauterine infection. In this model, to obtain live fetuses at 48 hours after inoculation, an antibiotherapy is necessary. This treatment, delivered 24 hours after inoculation, has no neuroprotective effect. Because of its better reproductibility, this model may allow to study other neuroprotective strategies.