siRNA下调星形胶质细胞中PTEN表达对缺氧复氧诱导细胞凋亡影响

目的研究siRNA下调星形胶质细胞中第10号染色体同源缺失性磷酸酶-张力蛋白(PTEN)表达对缺氧复氧诱导的细胞凋亡影响。方法分离培养乳鼠星形胶质细胞,用携带PTEN siRNA的慢病毒载体感染星形胶质细胞,经缺氧复氧处理后,用Real time PCR和Western blot检测细胞中PTEN表达变化。MTT测定细胞增殖活力,二硝基苯肼比色法检测乳酸脱氢酶(LDH)漏出率,流式细胞术测定周期和凋亡变化,Western blot检测细胞中细胞周期依赖性蛋白激酶4(Cdk4)、p21蛋白水平和胞质中细胞色素C(Cytochrome C)蛋白水平,JC-1法测定线粒体膜电位。结果携带PTEN siRNA的慢病毒载体感染后的星形胶质细胞中PTEN表达水平降低。缺氧复氧处理后的星形胶质细胞活力降低,细胞LDH漏出率升高,细胞凋亡率升高,细胞G1期比例升高,Cdk4蛋白水平降低,p21蛋白水平升高,胞质中Cytochrome C蛋白增多,线粒体膜电位降低。敲低PTEN可以提高缺氧复氧条件下星形胶质细胞活力,降低细胞LDH漏出率,减少G1期细胞比例,降低细胞凋亡率,促进细胞表达Cdk4蛋白,减少细胞表达p21,减少胞质中Cytochrome C蛋白,提高线粒体膜电位。结论敲低PTEN可以减少缺氧复氧诱导的星形胶质细胞凋亡,作用机制与线粒体凋亡途径有关。     

RNA干扰PDGF-B基因对胶质瘤U251细胞凋亡和增殖的影响

目的利用RNA干扰(RNA interference,RNAi)技术特定沉默胶质瘤U251细胞株的血小板源生长因子-B(PDGF-B)基因,观察其对U251细胞株细胞凋亡和增殖的影响。方法利用脂质体将针对PDGF-B基因的siRNA转染进入U251细胞,利用实时荧光定量多聚核苷酸链式反应(RTPCR)检测PDGF-B基因表达;Western blot检测显示siRNA转染组PDGF-B蛋白表达,采用MTT法检测胶质瘤U251细胞的增殖,应用流式细胞计数观察抑制PDGF-B基因后胶质瘤U251细胞的凋亡情况。结果 RT-PCR检测PDGF-B基因表达明显下降;Western blot检测显示siRNA转染组PDGF-B蛋白表达明显抑制(抑制率60%),MTT结果显示siRNA转染组U251细胞增殖较对照组明显降低;流式细胞学检测提示降低PDGF-B在胶质瘤细胞的表达能抑制胶质瘤细胞的有丝分裂,促进细胞的凋亡。结论构建针对胶质瘤细胞PDGF-B的RNA干扰质粒并转染人胶质瘤U251细胞株后,可明显抑制U251细胞株PDGF的表达,对人胶质瘤U251细胞株有明显的生长抑制和促进凋亡作用。     

星形胶质细胞连接蛋白43及其半通道在脑缺血再灌注损伤中的作用

目的探讨星形胶质细胞连接蛋白43(Cx43)及其半通道在缺血再灌注(IR)损伤中的作用。方法 32只Wistar鼠被随机分为IR 0 h组、IR 4 h组和IR 24 h组和对照组,每组8只鼠。用免疫组化和Western印迹法检测各组大鼠星形胶质细胞Cx43、半通道抗体1(HC1)和半胱天冬酶3(Casp3)的表达。在氧葡萄糖剥夺-再恢复(OGDR)0 h,4 h和24 h,用MTT法检测星形胶质细胞活性,用免疫组化和Western印迹法检测Cx43,HC1和Casp3表达的改变。结果大鼠星形胶质细胞中HC1的表达明显少于Cx43的表达。与对照组比较,IR 4 h组大鼠脑组织中Cx43、HC1和Casp3的表达明显增加(均P0.05),而IR 0 h组和IR 24 h组却没有明显的变化。OGDR后星形胶质细胞cell line和Psup细胞中Cx43、HC1和Casp3的表达在OGDR 4h组明显高于对照组(均P0.05),在OGDR 24 h组则与对照组差异无统计学意义。OGDR后shRNA星形胶质细胞中Cx43、HC1和Casp3的表达无统计学意义上变化。结论 Cx43及HCl在星形胶质细胞凋亡过程中起到了促进作用,这可能是IR损伤发生及发展的机制之一。     

星形胶质细胞AQP4蛋白在缺氧/复氧条件下表达变化的研究

目的观察缺氧/复氧条件下星形胶质细胞形态和AQP4蛋白的表达变化以及葛根素对其表达变化的影响,探讨脑缺血再灌注损伤与AQP4的关系以及葛根素的干预作用。方法原代培养星形胶质细胞,用5%CO2+95%N2混合气体造成缺氧,以LDH漏出率及MTT降解率作为细胞受损指标,应用Western blot技术检验星形胶质细胞缺氧/复氧各个时间点AQP4蛋白的表达变化及葛根素的干预效果。结果体外培养的星形胶质细胞在缺氧环境下损伤不明显,随着复氧时间的延长细胞损害加重。AQP4蛋白在缺氧时表达与正常对照组无明显差异,复氧后表达升高并随时间延长呈增高趋势(P0.05)。葛根素干预组AQP4蛋白表达丰度与缺氧/复氧组无明显差异(P0.05)。结论星形胶质细胞AQP4蛋白表达变化与细胞损伤有明显相关性,葛根素对星形胶质细胞损伤的保护作用不是通过改变AQP4的表达来实现的。     

氧糖剥离对星形胶质细胞CX43蛋白表达及分布的影响

目的探讨氧糖剥离(oxygen-glucose deprivation,OGD)对星形胶质细胞缝隙连接蛋白Cx43蛋白表达及分布的影响,为急性脑缺血早期临床治疗提供理论基础。方法通过OGD模拟缺血缺氧诱导激活培养的原代星形胶质细胞,采用免疫印迹及荧光显微镜观察缝隙连接蛋白Cx43的蛋白表达变化及细胞内亚分布特点。结果星形胶质细胞经OGD诱导后在再灌12h Cx43表达上调约1.5倍(P0.01),有统计学意义;再灌24h时Cx43表达轻度下调(P=0.13),无统计学意义;在再灌48h其下降约34%,与对照组相比,有统计学意义(P0.01)。同时在再灌24h时可见部分Cx43定位分布到细胞核。结论 OGD导致星形胶质细胞Cx43蛋白表达呈先升高后下降的动态变化并且有部分Cx43蛋白定位到细胞核,提示针对Cx43蛋白的干预治疗应考虑治疗时间窗。     

缺氧/复氧对体外培养星形胶质细胞脑源性神经营养因子合成及释放的影响

目的观察缺氧/复氧条件下体外培养星形胶质细胞活力变化及脑源性神经营养因子(BDNF)释放和表达的变化。方法采用原代培养的大鼠皮质星形胶质细胞,实验分为正常组(N)及缺氧/复氧组(H/R)。在缺氧/复氧各个时间点,应用MTT法检测缺氧/复氧时培养星形胶质细胞的活力变化,应用Western blot检测BDNF的表达水平;ELISA检测星形胶质细胞条件培养液上清中BDNF的含量。结果与对照组相比,在缺氧6 h、复氧72 h以内体外培养星形胶质细胞,细胞活力不会发生明显改变,BDNF的释放量无明显变化,但是缺氧/复氧可诱导体外培养星形胶质细胞BDNF表达量的增加。结论单纯的缺氧/复氧条件可影响体外培养星形胶质细胞BDNF的合成,但不足以引起BNDF的释放改变以及细胞的活力变化。     

凋亡敏感基因在短暂性缺氧再复氧复注血清后的大鼠星形胶质细胞中的表达及其意义

目的研究一种新发现的抗氧化蛋白质--凋亡敏感基因(SAG)在短暂性缺氧再复氧复注血清诱导的细胞坏死和凋亡中的作用.方法用短暂性缺氧再复氧复注血清来诱导原代培养的大鼠大脑皮质星形胶质细胞损伤,用免疫细胞化学方法检测凋亡敏感基因的表达,并作图像分析;用流式细胞仪检测胶质细胞在短暂缺氧再复氧复注血清后不同时间点的凋亡率.结果凋亡敏感基因在缺氧15 min再复氧复注血清5 h后表达最高,在复氧复注血清16 h后恢复至对照组水平;细胞凋亡率在缺氧15 min再复氧复注血清1h时达到最高,而在再复氧复注血清5 h后降至对照组水平.结论凋亡敏感基因具有抗凋亡的作用,可减轻星形胶质细胞的缺血再灌注损伤.     

脑白质低灌注损伤后星形胶质细胞缝隙连接蛋白43的表达变化

目的研究慢性脑白质缺血后星形胶质细胞和缝隙连接蛋白Connexin43(Cx43)的变化。方法原代培养星形胶质细胞,建立体外慢性缺氧模型;双侧颈总动脉狭窄法,建立慢性低灌注脑白质损伤小鼠模型;免疫荧光共染观察星形胶质细胞活化与Cx43表达。Western蛋白定量分析髓鞘相关指标髓鞘相关糖蛋白MAG,星形胶质细胞标记物GFAP和Cx43的表达。结果与对照组相比,细胞慢性缺氧7d后,星形胶质细胞明显增生活化,伴随Cx43表达水平明显上调。Western blot发现,在慢性脑白质缺血过程中,MAG的表达逐渐降低,GFAP持续增高,Cx43表达明显上调。免疫荧光共标记可见,星形胶质细胞中Cx43表达上调,主要分布于胼胝体中央区。结论慢性脑白质缺血损伤过程伴随星形胶质细胞Cx43表达增加,Cx43可能成为临床治疗血管性认知障碍的新靶点。     

特异性siRNA抑制髓母细胞瘤c-MYC基因表达研究

目的研究siRNA(small interference RNA)对c-MYC基因表达的抑制作用。方法通过脂质体将合成的c-MYC siRNA转入D425细胞株,以未转染细胞以及通用阴性对照为对照组,经MTT法检测siRNA对细胞生长的抑制,用RT-PCR和Western Blotting法检测siRNA对c-MYC表达的抑制作用,使用流式细胞仪检测由siRNA转染引起的细胞凋亡情况。结果MTT显示各时点细胞存活率,在Lipofectamine-siRNA组以及对照组和脂质体组在24h、48h及72h时均有显著差异(P<0.05)。RT-PCR以及Western Blotting法检测显示Lipofectamine-siRNA组c-MYC基因表达明显低于对照组、脂质体组、阴性对照组(P<0.05)。流式细胞仪检测凋亡结果显示,Lipofectamine-siRNA组的凋亡情况较其他组明显(P<0.05)。结论体外转染c-MYC siRNA可有效抑制D425细胞c-MYC基因的表达,效率可达50%以上。     

沉默Cdk5对星形胶质细胞活化增殖和细胞周期的影响

目的 观察沉默细胞周期蛋白依赖性激酶5(Cdk5)对星形胶质细胞活化增殖和细胞周期的影响。方法 培养及鉴定SD大鼠星形胶质细胞,设计合成针对星形胶质细胞Cdk5的小干扰RNA(siRNA),将Cdk5 siRNA转染入星形胶质细胞,通过Real-time PCR和Western blot检测沉默效率; 分为对照组及Cdk5 siRNA干预组,在不同时间点(3、6、12及24 h)采用Edu染色及流式细胞术检测细胞增殖及细胞周期情况。结果 成功利用Cdk5 siRNA沉默星形胶质细胞Cdk5; Edu染色显示Cdk5 siRNA干预组干预3、6、12 h Edu染色阳性率较对照组显著降低(P<0.01); 流式细胞术显示 Cdk5 siRNA干预组干预3、6、12 h处于S期的星形胶质细胞比例较对照组显著降低(P<0.05)。结论 沉默Cdk5可抑制星形胶质细胞的增殖及细胞周期进展,提示Cdk5在星形胶质细胞增殖过程中起到重要作用。     

Downregulation of spinal astrocytic connexin43 leads to upregulation of interleukin‐6 and cyclooxygenase‐2 and mechanical hypersensitivity in mice

Connexin43 (Cx43), involved in intercellular signaling, is expressed in spinal dorsal horn astrocytes and crucial in the maintenance of neuropathic pain. Downregulation of spinal astrocytic Cx43 in mice enhances glutamatergic neurotransmission by decreasing glutamate transporter GLT‐1 expression, resulting in cutaneous hypersensitivity. Decreased expression of astrocytic Cx43 could lead to altered expression of other nociceptive molecules. Transfection of Cx43‐targeting siRNA in cultured spinal astrocytes increased expression of the pronociceptive cytokine interleukin‐6 (IL‐6) and the prostaglandin synthesizing enzyme cyclooxygenase‐2 (COX‐2). Increased expression of IL‐6 and COX‐2 was due to decreased Cx43 expression rather than due to diminished Cx43 channel function. In mice, downregulation of spinal Cx43 expression by intrathecal treatment with Cx43‐targeting siRNA increased IL‐6 and COX‐2 expression and induced hind paw mechanical hypersensitivity. Cx43 siRNA‐induced mechanical hypersensitivity was attenuated by intrathecal treatment with anti‐IL‐6 neutralizing antibody and intraperitoneal treatment of selective COX‐2 inhibitor celecoxib, demonstrating that these molecules play a role in nociceptive processing following Cx43 downregulation. Restoring spinal Cx43 by intrathecal injection of an adenovirus vector expressing Cx43 in mice with a partial sciatic nerve ligation reduced spinal IL‐6 and COX‐2 expression. Suppression of glycogen synthase kinase‐3β (GSK‐3β), a serine/threonine protein kinase, prevented upregulation of IL‐6 and COX‐2 expression induced by Cx43 downregulation in both cultured astrocytes and in mouse spinal dorsal horn. Inhibition of spinal GSK‐3β also ameliorated Cx43 siRNA‐induced mechanical hypersensitivity. The current findings indicate that downregulation of spinal astrocytic Cx43 leads to changes in spinal expression of pronociceptive molecules underlying the maintenance of pain following nerve injury.     

Tumor necrosis factor-mediated downregulation of spinal astrocytic connexin43 leads to increased glutamatergic neurotransmission and neuropathic pain in mice

Spinal cord astrocytes are critical in the maintenance of neuropathic pain. Connexin 43 (Cx43) expressed on spinal dorsal horn astrocytes modulates synaptic neurotransmission, but its role in nociceptive transduction has yet to be fully elaborated. In mice, Cx43 is mainly expressed in astrocytes, not neurons or microglia, in the spinal dorsal horn. Hind paw mechanical hypersensitivity was observed beginning 3 days after partial sciatic nerve ligation (PSNL), but a persistent downregulation of astrocytic Cx43 in ipsilateral lumbar spinal dorsal horn was not observed until 7 days post-PSNL, suggesting that Cx43 downregulation mediates the maintenance and not the initiation of nerve injury-induced hypersensitivity. Downregulation of Cx43 expression by intrathecal treatment with Cx43 siRNA also induced mechanical hypersensitivity. Conversely, restoring Cx43 by an adenovirus vector expressing Cx43 (Ad-Cx43) ameliorated PSNL-induced mechanical hypersensitivity. The sensitized state following PSNL is likely maintained by dysfunctional glutamatergic neurotransmission, as Cx43 siRNA-induced mechanical hypersensitivity was attenuated with intrathecal treatment of glutamate receptor antagonists MK801 and CNQX, but not neurokinin-1 receptor antagonist CP96345 or the Ca²⁺ channel subunit α₂δ₁ blocker gabapentin. The source of this dysfunctional glutamatergic neurotransmission is likely decreased clearance of glutamate from the synapse rather than increased glutamate release into the synapse. Astrocytic expression of glutamate transporter GLT-1, but not GLAST, and activity of glutamate transport were markedly decreased in mice intrathecally injected with Cx43-targeting siRNA but not non-targeting siRNA. Glutamate release from spinal synaptosomes prepared from mice treated with either Cx43-targeting siRNA or non-targeting siRNA was unchanged. Intrathecal injection of Ad-Cx43 in PSNL mice restored astrocytic GLT-1 expression. The cytokine tumor necrosis factor (TNF) has been implicated in the induction of central sensitization, particularly through its actions on astrocytes, in the spinal cord following peripheral injury. Intrathecal injection of TNF in naïve mice induced the downregulation of both Cx43 and GLT-1 in spinal dorsal horn, as well as hind paw mechanical hypersensitivity, as observed in PSNL mice. Conversely, intrathecal treatment of PSNL mice with the TNF inhibitor etanercept prevented not only mechanical hypersensitivity but also the downregulation of Cx43 and GLT-1 expression in astrocytes. The current findings indicate that spinal astrocytic Cx43 are essential for the maintenance of neuropathic pain following peripheral nerve injury and suggest modulation of Cx43 as a novel target for developing analgesics for neuropathic pain.     

Connexin43 null mice reveal that astrocytes express multiple connexins

The gap junction protein connexin43 (Cx43) is the primary component of intercellular channels in cardiac tissue and in astrocytes, the most abundant type of glial cells in the brain. Mice in which the gene for Cx43 is deleted by homologous recombination die at birth, due to profound hypertrophy of the ventricular outflow tract and stenosis of the pulmonary artery. Despite this significant cardiovascular abnormality, brains of connexin43 null [Cx43 (−/−)] animals are shown to be macroscopically normal and to display a pattern of cortical lamination that is not detectably different from wildtype siblings. Presence of Cx40 and Cx45 in brains and astrocytes cultured from both Cx43 (−/−) mice and wildtype littermates was confirmed by RT-PCR, Northern blot analyses and by immunostaining; Cx46 was detected by RT-PCR and Northern blot analyses. Presence of Cx26 in astrocyte cultures was indicated by RT-PCR and by Western blot analysis, although we were unable to resolve whether it was contributed by contaminating cells; Cx30 mRNA was detected by Northern blot in long term (2 weeks) but not fresh cultures of astrocytes. These studies thus reveal that astrocyte gap junctions may be formed of multiple connexins. Presumably, the metabolic and ionic coupling provided by these diverse gap junction types may functionally compensate for the absence of the major astrocyte gap junction protein in Cx43 (−/−) mice, providing whatever intercellular signaling is necessary for brain development and cortical lamination.     

Proteomic analysis of astroglial connexin43 silencing uncovers a cytoskeletal platform involved in process formation and migration

Connexin43 (Cx43) is the most abundant gap junction protein of the brain, where it is predominantly expressed in astrocytes. Recent studies imply a role of Cx43 in the regulation of important cellular processes, including migration, proliferation, and shape formation. These processes are assumed to be reflected by the proteome of the Cx43 expressing cells. To analyze the influence of Cx43 on the astrocytic proteome, we used RNA interference to downregulate the expression of this connexin in cultures of mouse astrocytes. We applied difference gel electrophoresis (DIGE) to compare silenced astrocytes with control cells. The differential proteome analysis revealed 15 significantly regulated proteins (between 1.2‐ and 1.6‐fold), of which six are known to belong to a group of cytoskeletal proteins involved in cortical platform formation. Astrocytes treated with Cx43 small interfering (si)RNA showed an increased expression of the cytoskeletal proteins: actin, tropomyosin, microtubule‐associated protein RP/EB1, transgelin, and GFAP, and a decreased expression of cofilin‐1. Quantitative immunocytochemistry and Western blotting revealed similar results showing an upregulation of actin, tubulin, tropomyosin, EB1, transgelin and GFAP, and a downregulation of Ser‐3‐phosphorylated cofilin. Furthermore, Cx43 silencing led to phenotypical changes in cell morphology, migratory activity, and cell adhesion. Our results provide mechanistic clues for an understanding of Cx43 interaction with cellular motor activities such as migration and process formation in astrocytes. © 2009 Wiley‐Liss, Inc.     

Inhibition of connexin43 improves functional recovery after ischemic brain injury in neonatal rats

Connexin43 (Cx43) is one of the most abundant gap junction proteins in the central nervous system. Abnormal opening of Cx43 hemichannels after ischemic insults causes apoptotic cell death. In this study, we found persistently increased expression of Cx43 8 h to 7 d after hypoxia/ischemia (HI) injury in neonatal rats. Pre‐treatment with Gap26 and Gap27, two Cx43 mimetic peptides, significantly reduced cerebral infarct volume. Gap26 treatment at 24 h after ischemia improved functional recovery on muscle strength, motor coordination, and spatial memory abilities. Further, Gap26 inhibited Cx43 expression and reduced active astrogliosis. Gap26 interacted and co‐localized with Cx43 together in brain tissues and cultured astrocytes. After oxygen glucose deprivation, Gap26 treatment reduced the total Cx43 level in cultured astrocytes; but Cx43 level in the plasma membrane was increased. Degradation of Cx43 in the cytoplasm was mainly via the ubiquitin proteasome pathway. Concurrently, phosphorylated Akt, which phosphorylates Cx43 on Serine³⁷³ and facilitates the forward transport of Cx43 to the plasma membrane, was increased by Gap26 treatment. Microdialysis showed that increased membranous Cx43 causes glutamate release by opening Cx43 hemichannels. Extracellular glutamate concentration was significantly decreased by Gap26 treatment in vivo. Finally, we found that cleaved caspase‐3, an apoptosis marker, was attenuated after HI injury by Gap26 treatment. Effects of Gap27 were analogous to those of Gap26. In summary, our findings demonstrate that modulation of Cx43 expression and astroglial function is a potential therapeutic strategy for ischemic brain injury. GLIA 2015;63:1553–1567     

高渗刺激后大鼠视上核星形胶质细胞和神经元的反应及其相互关系的光、电镜研究

目的探讨大鼠尾静脉注射高渗盐水(9％NaCl，5．5mL／kg)后，视上核(SON)内星形胶质细胞和神经元的可塑性反应及相互间的关系。方法用免疫组织化学和免疫电镜技术，观察刺激后15，45，90，180和360minSON内缝隙连接蛋白43(Cx43)和蛋白32(Cx32)的变化及超微结构。结果光镜下观察到Cx43阳性星形胶质细胞在15min出现，45min达到高峰；Cx32阳性神经元90min达到高峰。电镜下在SON内，观察到下列四种超微结构：(1)突触样结构(synapse like structure)，位于神经元的轴突末梢与Cx43阳性的星形胶质细胞突起之间；(2)三成分的突触复合体(tripartite synaptic structure)，由突触前膜、突触后膜和靠近此突触的星形胶质细胞突起共同组成；(3)同源性缝隙连接(gap junction，GJ)，位于星形胶质细胞突起之间，两侧均为Cx43；(4)“异源性缝隙连接样结构”(heterotypic gap junctions，HGJ)，是由Cx32阳性神经元和Cx43阳性星形胶质细胞突起组成的一种超微结构。结论高渗刺激后，SON内Cx43阳性星形胶质细胞和Cx32阳性神经元明显增加，前者出现和高峰的时间早于神经元；两者之间的HGJ数量明显增加，其他结构的数量变化不明显，因此两者可能是通过HGJ进行快速的信息交流。     

Astrocytic CX43 hemichannels and gap junctions play a crucial role in development of chronic neuropathic pain following spinal cord injury

Chronic neuropathic pain is a frequent consequence of spinal cord injury (SCI). Yet despite recent advances, upstream releasing mechanisms and effective therapeutic options remain elusive. Previous studies have demonstrated that SCI results in excessive ATP release to the peritraumatic regions and that purinergic signaling, among glial cells, likely plays an essential role in facilitating inflammatory responses and nociceptive sensitization. We sought to assess the role of connexin 43 (Cx43) as a mediator of CNS inflammation and chronic pain. To determine the extent of Cx43 involvement in chronic pain, a weight‐drop SCI was performed on transgenic mice with Cx43/Cx30 deletions. SCI induced robust and persistent neuropathic pain including heat hyperalgesia and mechanical allodynia in wild‐type control mice, which developed after 4 weeks and was maintained after 8 weeks. Notably, SCI‐induced heat hyperalgesia and mechanical allodynia were prevented in transgenic mice with Cx43/Cx30 deletions, but fully developed in transgenic mice with only Cx30 deletion. SCI‐induced gliosis, detected as upregulation of glial fibrillary acidic protein in the spinal cord astrocytes at different stages of the injury, was also reduced in the knockout mice with Cx43/Cx30 deletions, when compared with littermate controls. In comparison, a standard regimen of post‐SCI treatment of minocycline attenuated neuropathic pain to a significantly lesser degree than Cx43 deletion. These findings suggest Cx43 is critically linked to the development of central neuropathic pain following acute SCI. Since Cx43/Cx30 is expressed by astrocytes, these findings also support an important role of astrocytes in the development of chronic pain. © 2012 Wiley Periodicals, Inc.     

Astrocyte cultures from conditional connexin43-deficient mice

Connexin43 (Cx43) mainly provides the molecular basis for astrocytic gap junctions. Interastrocytic coupling is thought to mediate extracellular ion homeostasis, long-range signaling, and neuroprotection in the brain. Cx43 has been implicated in astrocytic growth control and is also expressed in other cell types in the brain, such as leptomeningeal and vascular cells. Cx43 function has been studied in astrocyte cultures of Cx43-deficient mice, which lack Cx43 in all cell types. We have generated conditionally deficient mice with an astrocyte-directed inactivation of Cx43, which leaves expression in other cell types unaffected. Other connexins have been detected in astrocytes. For the study of astrocytes lacking Cx45 and Cx26 in vitro, which deficiencies are embryonic lethal, conditionally deficient astrocyte cultures are essential. In the present study, we describe the developmental kinetics of Cx43 inactivation and loss of intercellular communication in astrocyte cultures derived from conditional Cx43-deficient mice. Conditional ablation of Cx43 is efficient, reaches a plateau at 4 weeks in culture, but retains Cx43 expression in contaminating nonastrocytic cells. Our findings indicate that conditional knockout astrocytes are a promising tool for the study of embryonic lethal genes in astrocyte cultures.