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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, METHODS, RESULTS. Meshes: Animals, Blood Gas Analysis, Collagen Type IV, Disease Models, Animal, Electrolytes, Female, Hemorrhage, Hypoxia, Inflammation, Intracranial Hemorrhages, Ischemia, Laminin, Maternal Exposure, Matrix Metalloproteinase 9, Neovascularization, Pathologic, Pregnancy, Pregnancy, Animal, Rats, Rats, Wistar, Respiration, Artificial, Risk Factors, Time Factors, Vascular Endothelial Growth Factor A.
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Does angiogenesis induced by prenatal ischemia predispose to periventricular hemorrhage during postnatal mechanical ventilation? Context: Three risk factors are associated with hemorrhagic forms of encephalopathy of prematurity (EP): (i) prematurity, (ii) in utero ischemia (IUI) or perinatal ischemia, and (iii) mechanical ventilation. We hypothesized that IUI would induce an angiogenic response marked by activation of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9), the latter degrading vascular basement membrane and increasing vulnerability to raised intravenous pressure during positive pressure mechanical ventilation. We studied a rat model of hemorrhagic-EP characterized by periventricular hemorrhages in which a 20-min episode of IUI is induced at E19, pups are born naturally at E21-22, and on P0, are subjected to a 20-min episode of positive pressure mechanical ventilation. Tissues were studied by H&E staining, immunolabeling, immunoblot, and zymography. Mechanical ventilation of rat pups 2-3 d after 20-min IUI caused widespread hemorrhages in periventricular tissues. IUI resulted in upregulation of VEGF and MMP-9. Zymography confirmed significantly elevated gelatinase activity. MMP-9 activation was accompanied by severe loss of MMP-9 substrates, collagen IV and laminin, in microvessels in periventricular areas.
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Our findings are consistent with the hypothesis that positive pressure mechanical ventilation of the newborn in the context of recent prenatal ischemia/hypoxia can predispose to periventricular hemorrhages. Final Decision: yes