RNA干扰AQP4对创伤性脑水肿血脑屏障的保护作用

目的探讨RNA干扰（RNAi）水通道蛋白4（AQP4）对创伤性脑水肿血脑屏障（BBB）的保护作用。方法雄性成年Wistar大鼠,随机分为假手术组、对照质粒组、单纯创伤组和创伤后RNAi组。参照Marmarou法制作创伤性脑损伤（TBI）模型。采用侧脑室注射途径给药,应用免疫组织化学观测AQP4、微血管内皮细胞紧密连接闭合小环蛋白（ZO-1）,原位杂交法观测AQP4mRNA,光电镜观察脑组织超微结构。结果RNAi质粒可有效减少AQP4在受损脑组织的表达;RNAi组在各检测时间点脑组织含水量和BBB透性均小于TBI组和对照质粒组（P〈0．05）;TBI后RNAi组ZO-1表达水平各时间点明显高于单纯创伤组和对照粒组（P〈0．05）。结论TBI后损伤区AQP4的表达变化趋势和脑水肿的发展变化趋势相一致（r=0．982,P〈0．01）;应用RNA干扰途径减少AQP4表达,可有效保护TBI后脑水肿BBB结构的破坏。     

AQP4-siRNA alleviates traumatic brain edema by altering post-traumatic AQP4 polarity reversal in TBI rats

The spatial and temporal distribution of aquaporin-4 (AQP4) expression in rat brain following brain trauma and AQP4-siRNA treatment, as well as corresponding pathological changes, were studied to explore the mechanism underlying the effect of AQP4-siRNA treatment on traumatic brain injury (TBI). The rats in the sham operation group had normal structure, with AQP4 located in the perivascular end-foot membranes and astrocytic membranes in a polarized pattern. The accelerated polarity reversal was observed in the TBI group in 1–12 h after TBI. During this period, AQP4 abundance on the astrocytic membrane is gradually increased, while AQP4 abundance on the perivascular end-foot membrane declined rapidly. Twelve hours after TBI, AQP4 expression was depolarized, showing a shift from the perivascular end-foot membrane to the astrocytic membrane. Pathological observation showed that vasogenic edema occurred immediately after TBI, at which time the extracellular space was expanded, leading to severe intracellular edema. AQP4-siRNA reduced the polarity reversal index at the early stage of TBI recovery and reduced edema, demonstrating the potential benefit of reduced AQP4 expression during recovery from TBI.     

大鼠实验性脑创伤挫伤灶内皮屏障抗原和Ⅳ型水通道蛋白免疫反应性的动态改变

目的研究实验性脑创伤中内皮细胞屏障的损伤修复以及与位于星形细胞足突的Ⅳ型水通道的关系。方法成年雄性SD大鼠32只,随机分入对照组,伤后1h组,4h组,1d组,3d组,6d组和11d组。在大鼠重度冲击加速性伤模型中,应用免疫组化法观察脑创伤灶中内皮屏障抗原(EBA)和Ⅳ型水通道蛋白(AQP4)免疫反应性在不同时点的动态改变。采用图像分析技术对挫伤病灶免疫反应性进行定量分析。结果在血脑屏障损伤的皮质挫伤灶,伤后1dAQP4和EBA免疫反应性明显消失,AQP4阴性反应区面积明显大于EBA阴性反应区(P<0.05)。伤后3d,EBA表达重新出现。伤后6d,EBA表达延伸至挫伤中心区,AQP4表达始见于边缘。伤后11d,二者免疫反应性基本恢复。结论挫伤灶血管源性水肿形成同时伴有内皮屏障功能和星形细胞足突水通道的改变。同一创伤强度下,星形细胞足突AQP4损伤范围较内皮EBA大,恢复较慢。     

脑损伤后水通道蛋白4表达与血脑屏障通透性的关系

目的研究脑损伤后，水通道蛋白4（AQP4）的表达变化与血脑屏障（BBB）通透性之间的关系。方法健康成年Wistar大鼠，随机分成创伤性（TBI）组和假手术（SO）组。自由落体硬膜外撞击方法致重度脑创伤模型。于伤后4h、8h、12h、1d、3d、5d、7d取出大鼠脑组织，进行以下实验：①测创伤脑组织中伊文思蓝（EB）外渗的量，以EB外渗的量反应BBB通透性的变化；②免疫组化（IHC）和原位杂交（ISH）检测AQP4的表达变化。结果脑损伤后，BBB通透性增加，其增加有两个高峰，分别在TBI后12h和3d，后者尤为更明显。IHC和ISH显示，脑损伤后AQP4在脑组织中的表达逐渐上调，1d达高峰，持续至3d后下降，7d接近SO组水平。AQP4的表达变化与脑组织伊文思蓝（EB）含量的变化呈正相关（r=0．894，P〈0．05）。结论脑损伤后BBB通透性的增加与脑水肿的形成密切相关。TBI后BBB通透性增加，可能与AQP4表达上调有关，两者的变化影响TBI后脑水肿的发生、发展。     

人脑挫裂伤早期周围组织AQP4表达及血脑屏障超微结构观察

目的观察人脑挫裂伤后AQP4和血脑屏障超微结构在脑水肿形成中不同时间点的变化特征,探讨脑水肿的形成机制。方法取脑挫裂伤区组织标本60例(观察组),10例非功能区正常脑组织标本(对照组)。采用免疫组化和图像分析技术测定正常组及观察组伤后2～72 h相应时间点水肿区AQP4的表达水平,同时观察脑水肿含水量,血脑屏障指数,血脑屏障超微结构的变化。结果与正常组相比较,脑挫裂伤组在伤后2 h后AQP4表达开始增加(P<0.05),6 h、8 h、12 h明显增加(P<0.01),24～72 h达到最高(P<0.01)。AQP4表达与脑含水量的变化趋于一致(r=0.912,P<0.01);血脑屏障(BBB)指数与脑含水量的变化趋于一致(r=0.877,P<0.01);水通道蛋白4表达与BBB指数呈显著正相关(r=0.908,P<0.01)。伤后早期血脑屏障结构即发生改变,随后血脑屏障结构被明显破坏,24 h、72 h血脑屏障破坏最为严重。结论脑挫裂伤后AQP4表达明显增强,BBB的通透性增加,提示AQP4在损伤后脑水肿的形成过程中起重要作用。     

Glial swelling following human cerebral contusion: an ultrastructural study.

The ultrastructural features of cerebral contusion seen three hours to 11 days after head injury were studied in 18 patients undergoing surgery. Massive astrocytic swelling ("cytotoxic" oedema) was seen three hours to three days after injury, maximal in perivascular foot processes, and compressing some of the underlying capillaries. The tight junctions were not disrupted. Neuronal damage was most marked three to 11 days after injury. The pathophysiological mechanisms leading to oedema formation and neuronal degeneration are discussed.     

大鼠重型颅脑损伤急性期水通道蛋白4的表达

目的探讨水通道蛋白（AQP4）在大鼠重型脑外伤急性期的表达变化及其与脑水肿间的关系。方法49只成年雄性SD大鼠,随机分为对照组及实验组（伤后4h、8h、12h、24h、5d共5组）。制作重度冲击加速性损伤模型,分别于伤后4h、8h、12h、24h、72h、5d采用干湿比重法测脑组织含水量,原子吸收分光光度法测定Na^＋、K^＋含量,Evans Blue（EB）测定法观察大鼠血-脑屏障（BBB）通透性变化,半定量逆转录聚合酶链反应（RT-PCR）检测脑组织AQP4 mRNA表达及其变化。结果脑组织AQP4 mRNA在伤后4h开始表达上调,8h、12h依次增高,24h达到峰值（P〈0.05）,3d时仍维持较高水平,伤后5d有所降低。脑含水量、Na^＋含量的变化与AQP4 mRNA表达变化一致。经相关性分析,AQP4 mRNA的表达与脑含水量及脑EB含量均呈正相关（P〈0.05）。结论重型脑损伤急性期,AQP4 mRNA表达的变化与颅脑损伤后BBB的破坏及脑水肿的形成和发展密切相关。AQP4可能参与重型脑损伤后脑水肿的形成并起重要作用。     

Loss of astrocyte polarity marks blood–brain barrier impairment during experimental autoimmune encephalomyelitis

In multiple sclerosis (MS), and its animal model experimental autoimmune encephalomyelitis (EAE), dysfunction of the blood–brain barrier (BBB) leads to edema formation within the central nervous system. The molecular mechanisms of edema formation in EAE/MS are poorly understood. We hypothesized that edema formation is due to imbalanced water transport across the BBB caused by a disturbed crosstalk between BBB endothelium and astrocytes. Here, we demonstrate at the light microscopic and ultrastructural level, the loss of polarized localization of the water channel protein aquaporin-4 (AQP4) in astrocytic endfeet surrounding microvessels during EAE. AQP4 was found to be redistributed over the entire astrocytic cell surface and lost its arrangement in orthogonal arrays of intramembranous particles as seen in the freeze-fracture replica. In addition, immunostaining for the astrocytic extracellular matrix receptor β-dystroglycan disappeared from astroglial membranes in the vicinity of inflammatory cuffs, whereas immunostaining for the dystroglycan ligands agrin and laminin in the perivascular basement membrane remained unchanged. Our data suggest that during EAE, loss of β-dystroglycan-mediated astrocyte foot process anchoring to the basement membrane leads to loss of polarized AQP4 localization in astrocytic endfeet, and thus to edema formation in EAE. An erratum to this article can be found at     

Altered blood-brain barrier integrity in adult aquaporin-4 knockout mice

To investigate the role of astroglial water channel aquaporin-4 (AQP4) in maintaining blood-brain barrier integrity, structure and permeability of the brain microvessels were investigated in adult AQP4 knockout mice. Altered ultrastructure of brain microvessels, including open tight junctions and swollen perivascular astrocytic endfeet, were frequently observed in the AQP4 null mice. Likewise, AQP4 deficiency significantly downregulated expression of glial fibrillary acidic protein in perivascular processes of astrocytes. Furthermore, the horseradish peroxidase analysis demonstrated hyperpermeability of the blood-brain barrier in AQP4 knockout mice. These findings provide direct evidence that AQP4 is essential for the maintenance of blood-brain barrier integrity.     

X-irradiation of the contusion site improves locomotor and histological outcomes in spinal cord-injured rats.

We have determined whether X-irradiation of the injury site can oppose tissue loss and improve recovery of locomotor function following contusion injury of the spinal cord. Contusion injury was produced in rats at the level of T10 with a weight drop device. Localized X-irradiation (20 Gy) of the injury site was performed at 20 min and 1, 2, 4, 7, and 17 days postinjury. Locomotor recovery was then determined with the 21-point Basso, Beattie, and Bresnahan (BBB) scale. X-irradiation enhanced recovery of locomotor function during a subsequent 6-week observation period when administered 20 min and 1 or 2 days following contusion injury (final BBB score approximately 7-8). X-irradiation at 4-17 days postinjury did not significantly affect final locomotor scores compared with unirradiated rats (final BBB score approximately 2), in marked contrast to previous studies where X-irradiation applied only at 17-18 days benefitted transection injury. The extent of recovery was directly related to measurements of sparing of spinal cord tissue at the contusion center. Because the treatment time window occurred earlier in contusion than reported for transection injury, the results suggest that contusion injury rapidly initiates underlying radiation-sensitive processes that occur only following a delay of several weeks after transection injury. Further optimization of X-ray treatment may lead to a useful therapeutic modality for use in spinal cord contusion injury.     

Blood-brain barrier disruption highly induces aquaporin-4 mRNA and protein in perivascular and parenchymal astrocytes: protective effect by estradiol treatment in ovariectomized animals

Strong evidence involves aquaporin-4 (AQP4) in the physiopathology of brain edema. Two major points remain unsolved: (1) the capacity of perivascular glial cells to regulate AQP4 in response to disruption of the blood-brain barrier (BBB); and (2) the potential beneficial role of AQP4 in the clearance of brain edema. We used intraparenchymal injection of lipopolysaccharide (LPS) as an efficient model to induce BBB disruption. This was monitored by IgG extravasation and AQP4 was studied at the mRNA and protein level. The first signs of BBB disruption coincided with strong induction of AQP4 mRNA in perivascular glial cells. At the early phase, estradiol treatment highly prevented the LPS-induced disruption of the BBB and the induction of AQP4. Efficient clearance of vasogenic edema is supposed to occur once BBB is restored. This phase coincided with high induction of AQP4 mRNA in parenchymal reactive astrocytes and perivascular glial processes. High levels of AQP4 mRNA may be beneficial under these conditions. Our data may clarify why estradiol treatment reduces mortality in conditions typically associated with edema formation, like stroke.     

Spinal Cord Compression Injury in Guinea Pigs: Structural Changes of Endothelium and Its Perivascular Cell Associations after Blood–Brain Barrier Breakdown and Repair

This study examines morphological changes of the blood–brain barrier (BBB) after spinal cord compression. The lowest thoracic segment (T13) of female guinea pigs was injured and the BBB was tested from 7 days to 5.5 months postinjury using intravenously injected horseradish peroxidase (HRP) as a tracer. Tracer leakage in the injured segment was verified with the light microscope and the fine structure of capillaries was examined. Diffuse tissue staining was observed at T13 up to 2 weeks following injury. A leaky BBB correlated with expected changes in the fine structure of endothelial cell junctions. These were predominantly nonoverlapping cell junctions which, in many instances, were separated by clefts between adjacent cells. At early survival times, numerous capillary profiles with juxtaposed astrocyte foot processes were noted in addition to altered cell associations. Complete sealing of the BBB against interstitial HRP leakage was not observed until 17 days postinjury. After the first week, some of the endothelial cells were contacted by macrophages, processes of perivascular microglia, and processes of swollen and degenerating astrocytes. Perivascular spaces varied in extent and contained amorphous deposits of extracellular materials in addition to supernumerary layers of basal lamina. The early changes were followed by profound tissue restructuring due to loss of both neurons and glia. At longer survival times the BBB to HRP repaired. Endothelial cells formed complex overlapping junctions with zonulae occludentes. Most of the capillaries in the injured segment were no longer in direct contact with astrocyte foot processes, although reactive astrocytes constituted the predominant cell type in the remaining gray matter. Substantial expansion of perivascular spaces was evident. The cytoplasm of endothelial cells had numerous pinocytotic vesicles. Perivascular spaces contained layers of assembled collagen arranged perpendicularly to each other in addition to amorphous matrix materials. The findings suggest that decoupling of astrocyte foot processes from endothelial cell surfaces does not prevent reformation of tight junctions. It remains to be examined what effects the larger perivascular spaces, extracellular matrix deposits, and changes of cell associations may have on transport systems and ionic buffering. The data are relevant for estimating an opportune time for application of barrier-impermeable drugs to the lesion area.     

‘Hit & Run' model of closed-skull traumatic brain injury (TBI) reveals complex patterns of post-traumatic AQP4 dysregulation

Cerebral edema is a major contributor to morbidity associated with traumatic brain injury (TBI). The methods involved in most rodent models of TBI, including head fixation, opening of the skull, and prolonged anesthesia, likely alter TBI development and reduce secondary injury. We report the development of a closed-skull model of murine TBI, which minimizes time of anesthesia, allows the monitoring of intracranial pressure (ICP), and can be modulated to produce mild and moderate grade TBI. In this model, we characterized changes in aquaporin-4 (AQP4) expression and localization after mild and moderate TBI. We found that global AQP4 expression after TBI was generally increased; however, analysis of AQP4 localization revealed that the most prominent effect of TBI on AQP4 was the loss of polarized localization at endfoot processes of reactive astrocytes. This AQP4 dysregulation peaked at 7 days after injury and was largely indistinguishable between mild and moderate grade TBI for the first 2 weeks after injury. Within the same model, blood–brain barrieranalysis of variance permeability, cerebral edema, and ICP largely normalized within 7 days after moderate TBI. These findings suggest that changes in AQP4 expression and localization may not contribute to cerebral edema formation, but rather may represent a compensatory mechanism to facilitate its resolution.     

Gliovascular changes precede white matter damage and long‐term disorders in juvenile mild closed head injury

Traumatic brain injury (TBI) is a leading cause of hospital visits in pediatric patients and often leads to long‐term disorders even in cases of mild severity. White matter (WM) alterations are commonly observed in patients months or years after the injury assessed by magnetic resonance imaging (MRI), but little is known about WM pathophysiology early after mild pediatric TBI. To evaluate the status of the gliovascular unit in this context, mild TBI was induced in postnatal‐day 17 mice using a closed head injury model with two grades of severity (G1, G2). G2 resulted in significant WM edema (increased T2‐signal) and BBB damage (IgG‐extravasation immunostaining) whereas decreased T2 and the increased levels of astrocytic water‐channel AQP4 were observed in G1 mice 1 day post‐injury. Both severities induced astrogliosis (GFAP immunolabeling). No changes in myelin and neurofilament were detected at this acute time point. One month after injury G2 mice exhibited diffusion tensor imaging MRI alterations (decreased fractional anisotropy) accompanied by decreased neurofilament staining in the WM. Both severities induced behavioral impairments at this time point. In conclusion, long‐term deficits and WM changes similar to those found after clinical TBI are preceded by distinct early gliovascular phenotype alterations after juvenile mild TBI, revealing AQP4 as a potential candidate for severity‐based treatments.     

Acutely increased cyclophilin a expression after brain injury: a role in blood-brain barrier function and tissue preservation

Blood-brain barrier (BBB) compromise is a significant pathologic event that manifests early following traumatic brain injury (TBI). Because many signaling cascades are initiated immediately after the traumatic event, we were interested in examining acute differential protein expression that may be involved in BBB function. At acute time points postinjury, altered protein expression may result from altered translation efficiency or turnover rate rather than from a genomic response. The application of tandem 2-D gel electrophoresis and mass spectrometry analysis is a powerful approach for directly screening differential protein expression following TBI. Using comparative 2-D gel analysis, we selected candidate protein spots with apparent altered expression and identified them by mass spectrometry. Cyclophilin A was selected for further analysis because it has been implicated in endothelial cell activation and inflammation, and studies have suggested cyclosporine A, an inhibitor of all cyclophilin isoforms, might be beneficial after TBI. We examined if altered expression of cyclophilin A in the brain vasculature might play a role in BBB function. We found significantly increased cyclophilin A levels in isolated brain microvessels 30 min following injury. Postinjury administration of cyclosporine A significantly attenuated BBB permeability measured 24 hr postinjury, suggesting cyclophilin activity after TBI may be detrimental. However, direct injection of purified recombinant cyclophilin A attenuated both BBB permeability and tissue damage in a stab wound model of injury. These findings suggest that increased expression of cyclophilin A may play a protective role after TBI, whereas other cyclophilin isoforms may be detrimental.     

尼膜同对大鼠脑出血后血脑屏障通透性及水通道蛋白4mRNA表达的影响

目的研究大鼠脑出血后血脑屏障(BBB)通透性与水通道蛋白4(AQP4)的关系及尼膜同的干预作用。方法采用自体动脉血注入尾状核法制成大鼠脑出血模型,RT-PCR法观察AQP4mRNA的表达,伊文思兰法测量BBB通透性,干湿重法计算脑含水量表示脑水肿。结果与对照组相比,脑出血组及尼膜同组BBB通透性均在出血后6h开始升高(0.5955±0.0956、0.5092±0.0309),1d~3d最高(0.8889±0.0968、0.7826±0.0339和0.7914±0.0520、0.7442±0.0753),尼膜同组低于脑出血组(P<0.05);两组AQP4mRNA表达也于6h即开始升高(1.06±0.12、0.90±0.15),3d时达到高峰(1.34±0.14对1.27±0.14),尼膜同组低于脑出血组(P<0.05);BBB通透性与AQP4mRNA表达呈显著正相关(r=0.686,P<0.01),与脑水肿变化趋势一致。结论脑出血后可能通过上调APQ4mRNA表达,增加BBB通透性,参与脑水肿形成,尼膜同可抑制此过程。     

Severe alterations of endothelial and glial cells in the blood-brain barrier of dystrophic mdx mice

In this study, we investigated the involvement of the blood-brain barrier (BBB) in the brain of the dystrophin-deficient mdx mouse, an experimental model of Duchenne muscular dystrophy (DMD). To this purpose, we used two tight junction markers, the Zonula occludens (ZO-1) and claudin-1 proteins, and a glial marker, the aquaporin-4 (AQP4) protein, whose expression is correlated with BBB differentiation and integrity. Results showed that most of the brain microvessels in mdx mice were lined by altered endothelial cells that showed open tight junctions and were surrounded by swollen glial processes. Moreover, 18% of the perivascular glial endfeet contained electron-dense cellular debris and were enveloped by degenerating microvessels. Western blot showed a 60% reduction in the ZO-1 protein content in mdx mice and a similar reduction in AQP4 content compared with the control brain. ZO-1 immunocytochemistry and claudin-1 immunofluorescence in mdx mice revealed a diffuse staining of microvessels as compared with the control ones, which displayed a banded staining pattern. ZO-1 immunogold electron microscopy showed unlabeled tight junctions and the presence of gold particles scattered in the endothelial cytoplasm in the mdx mice, whereas ZO-1 gold particles were exclusively located at the endothelial tight junctions in the controls. Dual immunofluorescence staining of alpha-actin and ZO-1 revealed colocalization of these proteins. As in ZO-1 staining, the pattern of immunolabeling with anti-alpha-actin antibody was diffuse in the mdx vessels and pointed or banded in the controls. alpha-actin immunogold electron microscopy showed gold particles in the cytoplasms of endothelial cells and pericytes in the mdx mice, whereas alpha-actin gold particles were revealed on the endothelial tight junctions and the cytoskeletal microfilaments of pericytes in the controls. Perivascular glial processes of the mdx mice appeared faintly stained by anti-AQP4 antibody, while in the controls a strong AQP4 labeling of glial processes was detected at light and electron microscope level. The vascular permeability of the mdx brain microvessels was investigated by means of the horseradish peroxidase (HRP). After HRP injection, extensive perivascular areas of marker escape were observed in mdx mice, whereas HRP was exclusively intravascularly localized in the controls. Inflammatory cells, CD4-, CD8-, CD20-, and CD68-positive cells, were not revealed in the perivascular stroma of the mdx brain. These findings indicate that dystrophin deficiency in the mdx brain leads to severe injury of the endothelial and glial cells with disturbance in alpha-actin cytoskeleton, ZO-1, claudin-1, and AQP4 assembly, as well as BBB breakdown. The BBB alterations suggest that changes in vascular permeability are involved in the pathogenesis of the neurological dysfunction associated with DMD.     

盐酸纳美芬对大鼠颅脑损伤后脑水肿的影响

目的探讨盐酸纳美芬对大鼠颅脑损伤后脑水肿的影响。方法将54只Wistar大鼠按随机数字表法随机分为假手术组、颅脑损伤组及纳美芬治疗组。采用自由落体法建立大鼠颅脑损伤模型,分别于伤后6 h、1 d、3 d、7 d,采用干湿重法检测脑组织含水量,应用免疫组织化学法检测损伤脑组织中水通道蛋白4（AQP4）的表达。结果与假手术组比较,颅脑损伤组和纳美芬治疗组的脑组织含水量及AQP4水平明显升高（P〈0.05）;与颅脑损伤组相比,纳美芬治疗组脑组织含水量及AQP4表达水平明显降低（P〈0.05）。通过相关性分析发现,大鼠颅脑损伤后脑组织AQP4表达水平与脑含水量呈明显正相关性（r=0.676,P〈0.01）。结论盐酸纳美芬可能通过抑制AQP4表达,减轻脑水肿,发挥神经保护作用。     

神经干细胞移植联用神经节苷脂对脑损伤大鼠神经学功能恢复的影响*

背景：研究表明, 神经节苷脂(GM1)通过激活神经营养因子,抑制毒性产物对神经元的损害,并且能够减少兴奋性氨基酸所引起的神经细胞的死亡起到促进神经细胞修复的作用。 目的：神经干细胞移植同时应用GM1,观察两者对脑损伤大鼠恢复的影响。 方法：取健康Wistar大鼠制成重型液压颅脑损伤模型,随机分成3组：损伤组(培养液移植组),神经干细胞移植组,神经干细胞+GM1组。脑损伤后4 d用RT-PCR、Western Blot检测脑组织中AQP4基因表达和蛋白合成的变化,并于脑损伤后24 h,3 d及伤后1,2,3,4 周行动物神经学缺损评分,在脑损伤后21~28 d进行Morris水迷宫试验。4周后处死大鼠行免疫组化、苏木精-伊红染色组织学观察。 结果及结论：脑损伤后4 d脑损伤周围组织AQP4及其mRNA的表达损伤组高于神经干细胞移植组,神经干细胞移植组高于神经干细胞+ GM1组(P < 0.05);移植后1,2,3,4 周,大鼠神经学缺损评分及水迷宫测试结果显示,神经干细胞移植可明显改善重型颅脑损伤后大鼠的神经功能,联合应用GM1有协同效果。移植4周后苏木精-伊红染色神经干细胞+ GM1组出现典型的神经细胞样形态学改变且软化灶消失。免疫组化染色结果显示大鼠损伤灶脑组织中的BrdU阳性细胞数神经干细胞+GM1组高于NSCs移植组和损伤组。提示神经干细胞移植可明显改善重型颅脑损伤后大鼠的神经学功能,联合应用GM1有协同效果。     

The roles of aquaporin-4 in brain edema following neonatal hypoxia ischemia and reoxygenation in a cultured rat astrocyte model

Aquaporin-4 (AQP4), a water channel protein, is abundantly expressed in astrocytes and plays a key role in the development of brain edema. However, it is not clear whether AQP4 contributes to astrocytic swelling in hypoxia-ischemia (HI). To investigate the roles of AQP4 in astrocytic swelling during HI and reoxygenation, we measured AQP4 expression and astrocytic cellular volume in cultured rat astrocytes following HI and reoxygenation. RNA interference was used to knockdown AQP4 expression (AQP4(-/-)). Real-time polymerase chain reaction and Western blot analysis were used to detect the inhibitory efficiency of AQP4. We found that the maximal inhibition of AQP4 mRNA and protein in astrocytes after AQP4 siRNA transfection (AQP4(-/-)) was approximately 77 and 85%, respectively, compared to wild-type AQP4 (AQP4(+/+)) expression. Cellular volume in both AQP4(-/-) and AQP4(+/+) astrocytes was significantly increased during HI compared to cells cultured in normoxia (P<0.05). However, cellular volume during HI in AQP4(-/-) astrocytes was significantly less than that in AQP4(+/+) astrocytes (P<0.05). After reoxygenation, the cellular volume gradually decreased to control levels at 7 days in AQP4(-/-) but at 5 days in AQP4(+/+) astrocytes. The different roles of AQP4 during HI and reoxygenation suggest that AQP4 knockdown may protect against water influx in the formation of astrocyte swelling during HI, and may also delay water clearance in the resolution of astrocyte swelling during reoxygenation. In conclusion, AQP4 mediates bidirectional transport of water across astrocytes during HI and reoxygenation. AQP4 manipulation may serve as a novel therapeutic strategy during different periods of hypoxic-ischemic brain edema in neonates.