Effects Of Hyperbaric Oxygen On Neural Stem Cells Of Subventricular Zone And Brain Functional Outcome Of Rats With Hypoxic-ischemic Brain Damage

【Objective】To investigate effect of hyperbaric oxygen (HBO) on neural stem cells (NSCs) and brain function of neonatal rats with hypoxic-ischemic brain damage (HIBD) and provide experimental and theoretical evidences for the rehabitation of HIBD by HBO .【Methods】A rat model of HIBD in uterus was established by ligating uterine horn vessel of pregnant rats on one side, and the HIBD rats were divided into three groups: HIBD group (n=30), HIBD with HBO group (n=30), HIBD with normobaric oxygen (NBO) group (n=30). Rats (n=90) in the other side without ligating uterine horn vessel were also divided into three groups as the normal control group: the control group (n=30), the normal with HBO group (n=30), the normal with NBO group (n=30). The rats with HBO or NBO intervention were treated by oxygen under 2ATA pressure (HBO) or the usual pressure (NBO) separately one hour a day for 14 days from postnatal 24 hours. The rats in non-intervention groups were kept in a standard condition without HBO or NBO intervention. At postnatal 12h, 15d and 28d, rats'brain were taken out to detected the levels of superoxide dismutase (SOD) and malonyldialdehyde (MDA) with the methods of xanthine oxidase and thiobarbituric acid (TBA). The subventricular zone (SVZ) were separated for short-term cultivation and neural stem cells (NSCs) in SVZ were detected by immunofluorescence staining with nestin antibody after the flash-visual evoked potentials (F-VEP) and learning and memory function ( water maze test) were tested in P28d rats of the six groups.【Results】1. The level of SOD in P12h rats'brain with HIBD (71.54±4.00 U/mgprot) was lower than that in the control group (91.52±6.90 U/mgprot), while MDA (27.53±4.11 nmol/mgprot) was higher than that in the control group (16.25±2.42 nmol/mgprot) (P < 0.01). There were no significant differences in the levels of SOD and MDA of P15d rats'brain between in HIBD with HBO group and the control group ( P > 0.05), but the level of SOD was higher and the level of MDA was lower in HIBD with HBO group compared with those in HIBD with NBO group and in HIBD group (P < 0.01). There were no significant differences in the level of SOD and MDA of P15d rats'brain between in HIBD with NBO group and HIBD group (P > 0.05) or among in the normal with NBO group, the normal with HBO group and the control group (P > 0.05). There were also no significant differences in the levels of SOD and MDA of P28d rats'brain among six groups ( P > 0.05).2. The number of NSCs in the SVZ of P12h rats in the HIBD group (M = 3.36%) was obviously less than that in the control group (M = 6.03%) (P < 0.01). After HBO intervention, the cell counting of NSCs of the HIBD rats (P15d and P28d) had no significant differences compared with those in the control group (P > 0.05), but was increasing than those in both HIBD with NBO group and HIBD group (P < 0.01). NSCs in the normal with HBO group (P15d and P28d) were also more than that in the control group (P < 0.01). There were no significant differences between in the HIBD with NBO group and HIBD group (P > 0.05) or between in the normal with NBO group and the control group (P15d and P28d) (P > 0.05).3. The main wave P1 latency of F-VEP of P28d rats in HIBD group (58.60±5.12 ms) was prolonged significantly than that in the control group (48.67±4.15 ms) (P < 0.01), but there were no significant differences between in the HIBD with HBO group and the control group (P > 0.05) or between in HIBD with NBO group and HIBD group (P > 0.05) or among the normal with NBO group, the normal with HBO group and the control group (P > 0.05).4. The training times of reaching the platform correctly of P28d rats in HIBD group (15.90±2.13 times) was more than that in the control group (9.10±1.29 times) ( P < 0.01). The training times in HIBD with HBO group were less than in HIBD group (P < 0.01), but more than in the control group (P < 0.01).There were no significant differences in the training times between in HIBD with NBO group and HIBD group (P > 0.05) or among the normal with NBO group, the normal with HBO group and the control group (P > 0.05).【Conclusions】The neonatal rats with HIBD were treated with HBO for 14 days beginning with postnatal 24h, which can enhance antioxidant capacity, promote the survival of NSCs in SVZ, shorten the latency of F-VEP and improve learning and memory function. Improving antioxidant capacity and survival of NSCs in SVZ, and promoting myelinization of nerve fibre and efficiency of synaptic connection maybe relate to the mechanism of the rehabitation of hypoxic-ischemic brain damage by HBO.