The role of complement in neurodevelopmental impairment following neonatal hypoxic-ischemic encephalopathy.

Evidence has accumulated implicating complement activation in the pathogenesis of acute post-hypoxic-ischemic cerebral injury in infants who develop hypoxic-ischemic encephalopathy (HIE). However, the relationship between complement activation and subsequent neurological impairment is not known. We tested the hypothesis that in human neonates, post-hypoxic-ischemic complement activation within the central nervous system is positively associated with the acquisition of subsequent neurodevelopmental abnormalities. This prospective study included 18 full-term infants diagnosed with HIE following resuscitation at birth and seven control infants. Cerebrospinal fluid (CSF) samples were obtained from all infants in the first 24 hours of life as part of routine investigations to exclude sepsis and meningitis. Concentrations of terminal complement complexes (TCC), complement component 9 (C9), and albumin were quantified by enzyme-linked immunosorbent assay in all CSF samples. Neurological examination and Denver Developmental Screening Test II were performed at 6 and 12 months of life. Of the 18 HIE subjects, nine died, six survived with significant neurological impairment, and three had normal neurological outcomes. In the CSF of the 15 HIE infants who died or survived with abnormal outcomes, the mean concentration of TCC was increased compared with controls (p = 0.026) and the mean C9 concentration appeared to be decreased but the difference was not statistically significant (p = 0.056). Similar to the TCC concentration, the concentration of albumin in the CSF was significantly increased in infants with abnormal outcomes (p = 0.005). This study indicates that complement activation following resuscitation at birth, as manifested by increased TCC in the CNS, is positively correlated with the combination of the development of subsequent neurological sequelae and death. Further study incorporating larger sample sizes will be required to confirm this association. This step is essential before clinical trials of complement inhibitors can be justified in human neonates who suffer birth asphyxia.

Complement component 9 activation, consumption, and neuronal deposition in the post-hypoxic-ischemic central nervous system of human newborn infants.

The role of complement in neonatal hypoxic-ischemic brain injury is not known. Therefore, cerebral spinal fluid (CSF) and post-mortem cerebral tissue were analyzed to determine whether complement is activated and complement component 9 (C9) is deposited on neurons in the central nervous systems (CNS) of newborn infants who developed moderate to severe hypoxic-ischemic encephalopathy (HIE). Control CSF samples were obtained during routine evaluation for possible sepsis from infants who were not depressed at birth. In ELISA assays of CSF obtained from 16 infants with HIE, compared to CSF from 7 control infants, the mean concentration of terminal complement complexes was elevated and the mean C9 concentration was diminished. Immunofluorescence microscopy of post-mortem frozen brain tissue obtained from two infants who expired at 4-5 days of life after severe HIE revealed that activated C9 was deposited on cells in all lobes. Double label immunofluorescence microscopy demonstrated that nearly all of the C9-positive cells were neurons and essentially all of the neurons were C9-positive. Immunoperoxidase immunohistochemistry of formalin-fixed tissue also confirmed the presence of many C9-positive cells, particularly in the hippocampus. The C9-positive cells usually manifested morphology consistent with neurons, most of which contained fragmented nuclei. In summary, complement was activated in the CNS of newborn infants who developed moderate to severe HIE. C9 was deposited on neurons, including morphologically apoptotic neurons. Further investigations into a possible role of complement in the pathogenesis of neonatal hypoxic-ischemic cerebral injury are warranted.

Indices of hemodynamic and respiratory functions in premature infants at risk for the development of cerebral white matter injury.

OBJECTIVE: To examine potential differences in clinical risk factors, including indices of hemodynamic and respiratory functions, of premature infants developing periventricular hemorrhagic infarction (PHI) or periventricular leukomalacia (PVL). STUDY DESIGN: Indices of hemodynamic stability and respiratory function were measured prospectively during the first week of life in a cohort of 100 premature infants with respiratory distress. Maternal history was retrospectively reviewed. These data were correlated with cranial ultrasonography using one-way ANOVA, Bonferroni multiple comparisons, and Wilcoxon rank sum tests. Longitudinal analysis was performed using Generalized Estimating Equations. RESULTS: Fifty-two infants with normal cranial ultrasound studies were compared to 12 with PHI and 9 with PVL. Infants developing PHI had significantly lower birth weights, lower Apgar scores, were more often male and multiple gestations, and required more vasopressor support than infants with normal ultrasound studies. Infants with PHI had significantly worse indices of respiratory function than either normal infants or those with PVL. PVL was significantly associated with maternal chorioamnionitis, whereas PHI was not. CONCLUSION: These data suggest that there are important differences in the pathogenesis of PHI and PVL. A clear understanding of these differences is required before future preventive strategies can be formulated.