Permeability Of Exogenetic BDNF Through Placental Barrier And Blood-brain Barrier In Rats With Transient Uteroplacental Ischemia And Its Effection On Apoptosis Of Embryo Brain And Its Signal Pathways

Part 1: Permeability of Exogenetic BDNF through placental barrier of pregnant rats and blood-brain barrier of fetus with transient uteroplacental ischemiaObjective To investigate the potential of BDNF to penetrate the placental barrier and get into the fetus and pass through the blood-brain barrier of fetus to play neuroprotective function in the condition of transient ischemia. Methods Rats of 17 days of gestation were selected. Uterine arteries of the rats in the experimental group were clamped for 30 minutes, followed by intravenous injection of BDNF labeled with ¹²⁵I through the caudal vein. The radioactivity of BDNF in amniotic fluid, placentas and different organs of fetuses was detected at 24h, 48h, and 72 h post-injection time points. Results (1) ¹²⁵I-BDNF was detected in amniotic fluid, placentas and fetal organs including brain, heart, lungs, liver and kidneys. (2) The permeability of BDNF to the placenta barrier and the concentration of BDNF in organs of fetus increased along with the increase of the dose injected. (3) BDNF wasable to pass through the blood-brain barrier into fetus brain. (4) The penetration rates of BDNF through placental barrier and blood-brain barrier increased under the condition of fetal ischemia and hypoxia. Conclusions BDNF is, to some extent, able to permeate the placental barrier and blood-brain barrier and get into the fetal brain in pathological condition of ischemia and hypoxia. It will be possible for BDNF to be applied to the fetus suffered from intrauterine hypoxia-ischemia as a therapeutic agent.Part 2: Study on pathological changes and apoptosis of rat embryo brain cells suffered with intrauterine hypoxia-ischemic injuryObjective: To observe the pathological changes of rat fetal brain cells caused by transient intrauterine ischemia in pregnant rats so as to investigate the possible pathological mechanism of neonatal brain cells suffered from intrauterine hypoxia-ischemic injury.Methods: The uterine arteries of the pregnant rats in the seventeenth gestational days were clamped for 30 min in the experimental group. The samples were collected at 24-, 48- and 72-hour respectively after artery clamping. In control group rat abdomens were cut open and closed without uterine arteries clamping. Control group samples were collected at the same time as the experimental group. The pathological changes of brain tissues were observed under light microscope by HE, Nissl, cholinesterase staining, sequential Tunel technique, and by electron microscopy as well. The expression of Nuclear Transcription Factor (NF- k B) in brains were detected by immumohistochemical technique. The content of Evans Blue in neonatalbrain were measured.Results: The edema, degeneration of neural cells and the hemorrhage ofbrain were observed in the experimental group. Nissl bodies and the activityof cholinesterase decreased. The apoptosis cells appeared 24hr afterhypoxia-ischemia injury and increased progressively with time. Theexpression of NF- k B increased in the experimental group comparing withthat of the control group, with statistical significance (p<0.05). The content ofEvans blue in the neonatal brains of experimental group were more thanthose in the control group.Conclusions: Uterine hypoxia and ischemia can cause severe damage toneural cells.Part 3: Effect of exogenetic Brain-derived Neurotrophic Factor on apoptosis of embryo brain suffered from intrauterine hypoxia- ischemic injury and its signal pathwaysObjective: To investigate the effect and possible signal pathways of BDNF on apoptosis of rat embryo brain cells suffered from intrauterine hypoxia-ischemic injury.Methods: Seventeen-gestational day rats were selected. The uterine arteries of the rats were clamped for 30 minutes in both the experimental group (n=9 ) and the control group (n=12). 2 u g BDNF was injected into the rats in the experimental group while saline was injected into the rats in the control group through caudal veins. The samples were collected at 24-, 48- and 72-hour respectively after artery clamping. Rats' abdomens in the sham operation group (n=14) were cut open and closed without uterine arteriesclamping. Neuroapoptosis of different groups induced by ischemic damage was measured by terminal deoxynucleotidy transferase-mediated dUTP nick end labeling (Tunel) assay. The expression of extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK) were observed by immunohistochemistry. The images were analyzed with image pro plus 4.01 edition software. SPSS 11.0 software was used to carry out statistic analysis. Results: Few apoptosis cells could be found in the sham operation group, which may be a phenomenon of physiological death of neural cells. Apoptosis cells could be observed at 24hr, 48hr and 72hr point after ischemia in both the experimental group and the ischemic control group. The number of apoptosis cells after hypoxia-ischemia injury increased progressively with time. The apoptosis cells in the experimental group is much lower in number than that of the control group (24hr: 11.50±1.87 vs 16.00±1.41, p<0.05; 48hr: 16.01+1.41 vs 22.83±1.94, p<0.01; 72hr. 24.17+1.72 vs 39.01±2.61, p<0.01). The expression of ERK increased while the expression of JNK decreased in the experimental group, comparing with that of the control group, with statistical significance (p<0.05).Conclusions: BDNF demonstrated neuroprotective effects on rat embryo brain cells suffered from intrauterine hypoxia-ischemic injury, its mechanism might be associated with erecting antiapoptotic function on rat embryo brain cells through activating the ERK signal pathway.