Rapamycin promotes autophagy and reduces neural tissue damage and locomotor impairment after spinal cord injury in mice

The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that negatively regulates autophagy. Rapamycin, an inhibitor of mTOR signaling, can promote autophagy and exert neuroprotective effects in several diseases of the central nervous system (CNS). In the present study, we examined whether rapamycin treatment promotes autophagy and reduces neural tissue damage and locomotor impairment after spinal cord injury (SCI) in mice. Our results demonstrated that the administration of rapamycin significantly decreased the phosphorylation of the p70S6K protein and led to higher expression levels of LC3 and Beclin 1 in the injured spinal cord. In addition, neuronal loss and cell death in the injured spinal cord were significantly reduced in the rapamycin-treated mice compared to the vehicle-treated mice. Furthermore, the rapamycin-treated mice showed significantly higher locomotor function in Basso Mouse Scale (BMS) scores than did the vehicle-treated mice. These results indicate that rapamycin promoted autophagy by inhibiting the mTOR signaling pathway, and reduced neural tissue damage and locomotor impairment after SCI. The administration of rapamycin produced a neuroprotective function at the lesion site following SCI. Rapamycin treatment may represent a novel therapeutic strategy after SCI.     

Wnt signaling has opposing roles in the developing and the adult brain that are modulated by Hipk1

The canonical Wnt/Wingless pathway is implicated in regulating cell proliferation and cell differentiation of neural stem/progenitor cells. Depending on the context, β-Catenin, a key mediator of the Wnt signaling pathway, may regulate either cell proliferation or differentiation. Here, we show that β-Catenin signaling regulates the differentiation of neural stem/progenitor cells in the presence of the β-Catenin interactor Homeodomain interacting protein kinase-1 gene (Hipk1). On one hand, Hipk1 is expressed at low levels during the entire embryonic forebrain development, allowing β-Catenin to foster proliferation and to inhibit differentiation of neural stem/progenitor cells. On the other hand, Hipk1 expression dramatically increases in neural stem/progenitor cells, residing within the subventricular zone (SVZ), at the time when the canonical Wnt signaling induces cell differentiation. Analysis of mouse brains electroporated with Hipk1, and the active form of β-Catenin reveals that coexpression of both genes induces proliferating neural stem/progenitor cells to escape the cell cycle. Moreover, in SVZ derive neurospheres cultures, the overexpression of both genes increases the expression of the cell-cycle inhibitor P16Ink4. Therefore, our data confirm that the β-Catenin signaling plays a dual role in controlling cell proliferation/differentiation in the brain and indicate that Hipk1 is the crucial interactor able to revert the outcome of β-Catenin signaling in neural stem/progenitor cells of adult germinal niches.     

分泌型卷曲相关蛋白2在心肌再生治疗中的作用

干细胞的旁分泌机制已被认为是促进梗死区心肌再生、修复损伤心肌细胞的主要途径.随着进一步的深入研究,发现分泌型卷曲相关蛋白2(secreted frizzled-related protein2,Sfrp 2)与于细胞的旁分泌机制有着密切的联系,它通过竞争结合Wnt信号通路的特异性卷曲受体(Fz),从而抑制Wnt通路的信号传导,调控细胞的凋亡、分化等生命过程,成为近年来研究的热点.我们就Sfrp 2通过Wnt信号途径参与调节干细胞治疗心肌梗死的机制作一综述.     

MTOR信号通路在脊髓损伤中的研究进展

哺乳动物雷帕霉素靶蛋白(Mammalian target of rapamycin,mTOR)信号通路在细胞代谢,增殖与存活,血管生成,延缓细胞衰老中发挥着关键作用。另外,mTOR信号通路在各种中枢神经系统疾病和中枢神经系统创伤及修复中起着非常关键的作用。近年来,mTOR信号通路相关抑制药物相继问世,并在免疫抑制和抗肿瘤方面取得了一定的临床疗效。mTOR信号通路的细胞分子机制已成为研究热点。本文就调节mTOR信号通路在脊髓损伤中产生神经保护、神经再生效应的研究进展进行综述。     

大鼠脊髓损伤后Wnt信号分子的表达变化

目的:探讨大鼠脊髓损伤后不同时期Wnt信号分子Wnt-1、β-连锁蛋白(β-catenin)及糖原合成酶激酶-3β(GSK-3β)在脊髓损伤局部的表达情况.方法:50只成年雌性SD大鼠随机均分为对照组和实验组,麻醉下手术显露T9～T11椎板,切除T10全椎板,实验组大鼠用NYU打击器以10g×5cm的打击能量致伤T10脊髓,对照组只行全椎板切除,不致伤脊髓.分别于术后1d、3d、5d、7d、14d每组各取5只大鼠,取以损伤区为中心共15mm范围内(对照组取相应部位)脊髓组织,提取总RNA,采用半定量RT-PCR的方法检测脊髓组织中Wnt-1、β-catenin及GSK-3β的mRNA表达量.结果:脊髓损伤后1d和3d时Wnt-1和β-catenin出现高表达,5d后其表达逐渐减弱,14d左右其表达基本恢复到正常水平,而在脊髓损伤后1d和3d时GSK-3β呈低表达,5d后其表达逐渐增强,各时间点之间差异有显著性(P<0.05).对照组中Wnt-1和β-catenin及GSK-3β均呈低表达,各时间点表达无显著差异(P<0.05).结论:大鼠脊髓损伤后损伤局部脊髓组织中Wnt-1,β-catenin及GSK-3β的表达发生变化,提示Wnt信号在脊髓损伤后的早期被激活,其可能与脊髓损伤后的修复再生有关.     

Stem cell-based cell therapy for spinal cord injury

Traumatic injuries to the spinal cord lead to severe and permanent neurological deficits. Although no effective therapeutic option is currently available, recent animal studies have shown that cellular transplantation strategies hold promise to enhance functional recovery after spinal cord injury (SCI). This review is to analyze the experiments where transplantation of stem/progenitor cells produced successful functional outcome in animal models of SCI. There is no consensus yet on what kind of stem/progenitor cells is an ideal source for cellular grafts. Three kinds of stem/progenitor cells have been utilized in cell therapy in animal models of SCI: embryonic stem cells, bone marrow mesenchymal stem cells, and neural stem cells. Neural stem cells or fate-restricted neuronal or glial progenitor cells were preferably used because they have clear capacity to become neurons or glial cells after transplantation into the injured spinal cord. At least a part of functional deficits after SCI is attributable to chronic progressive demyelination. Therefore, several studies transplanted glial-restricted progenitors or oligodendrocyte precursors to target the demyelination process. Directed differentiation of stem/progenitor cells to oligodendrocyte lineage prior to transplantation or modulation of microenvironment in the injured spinal cord to promote oligodendroglial differentiation seems to be an effective strategy to increase the extent of remyelination. Transplanted stem/progenitor cells can also contribute to promoting axonal regeneration by functioning as cellular scaffolds for growing axons. Combinatorial approaches using polymer scaffolds to fill the lesion cavity or introducing regeneration-promoting genes will greatly increase the efficacy of cellular transplantation strategies for SCI.     

Notch信号通路在脊髓损伤中的研究进展

脊髓损伤是一种严重的中枢神经系统疾病,会引起一系列复杂的病理生理学变化,激活包括Notch信号在内的多种信号通路.研究证实Notch信号通路的激活不利于脊髓损伤后神经修复和症状改善,其机制包括抑制神经元分化和轴突再生,促进反应性星形胶质细胞增生,促进M1型巨噬细胞极化和促炎因子的释放,抑制新生血管的生成.因此,以抑制N...     

mTOR 信号通路和肿瘤治疗

PI3K蛋白激酶类家族的mTOR作为信号传导分子,在细胞的生长、增殖、分化和凋亡等许多生理过程中起着重要的控制作用,笔者就其信号通路的构成以及其上、下游信号的特点作一概述,并初步阐明mTOR信号通路与肿瘤治疗的关系.     

Blood supply and vascular reactivity of the spinal cord under normal and pathological conditions

The authors present a review of spinal cord blood supply, discussing the anatomy of the vascular system and physiological aspects of blood flow regulation in normal and injured spinal cords. Unique anatomical functional properties of vessels and blood supply determine the susceptibility of the spinal cord to damage, especially ischemia. Spinal cord injury (SCI), for example, complicating thoracoabdominal aortic aneurysm repair is associated with ischemic trauma. The rate of this devastating complication has been decreased significantly by instituting physiological methods of protection. Traumatic SCI causes complex changes in spinal cord blood flow, which are closely related to the severity of injury. Manipulating physiological parameters such as mean arterial blood pressure and intrathecal pressure may be beneficial for patients with an SCI. Studying the physiopathological processes of the spinal cord under vascular compromise remains challenging because of its central role in almost all of the body's hemodynamic and neurofunctional processes.     

毛囊干细胞定向分化过程中Wnt信号通路介导的基因调控

皮肤的毛囊干细胞具有自我复制以及多向分化潜能，在毛囊形态发育和定向分化过程中，Wnt信号通路起决定性作用。参与这条信号通路的重要蛋白质，如Wnt蛋白、Frizzled、B—catenin、GSK313、APC、Axin等研究相对较早，且颇为深入。但对于这条通路下游的调节因子，尤其是细胞核内关键性转录因子Tcf3、Lef1，以及它们所调控的一些重要基因c—myc、eyelinDl等的研究仍处于起步阶段。本文就Wnt信号通路介导的基因调节毛囊干细胞定向分化的研究现状进行综述．为构建组织工程皮肤提供理论参考。     

Notch信号通路在骨髓间充质干细胞及骨代谢疾病中的功能研究进展

骨髓间充质干细胞是存在于骨髓基质中的一种多能干细胞,具有多向分化的潜能,其天然再生能力对骨骼的生长代谢和骨转换起着至关重要的作用。Notch信号通路是一条在进化中高度保守的信号转导通路,与骨髓间充质干细胞的增殖、分化与凋亡密切相关,影响人体骨骼发育,也是多种骨代谢疾病的重要调节通路。以往对Notch信号通路的研究主要集中在神经干细胞,对骨髓间充质干细胞的研究较少。本文通过查阅文献,阐述不同的影响因素介导Notch信号通路对骨髓间充质干细胞分化的调节,并总结了Notch信号通路在骨代谢疾病如Alagille综合征、Adams Oliver综合征、脊椎肋骨发育不良、HajduCheney综合征、骨折愈合中的研究近况。     

Bcl-xL expression after contusion to the rat spinal cord.

After contusion-derived spinal cord injury, (SCI) there is localized tissue disruption and energy failure that results in early necrosis and delayed apoptosis, events that contribute to chronic central pain in a majority of patients. We assessed the extent of contusion-induced apoptosis of neurons in a known central pain-signaling pathway, the spinothalamic tract (STT), which may be a contributor to SCI-induced pain. We observed the loss of STT cells and localized increase of DNA fragmentation and cytoplasmic histone-DNA complexes, which suggested potential apoptotic changes among STT neurons after SCI. We also showed SCI-associated changes in the expression of the antiapoptotic protein Bcl-xL, especially among STT cells, consistent with the hypothesis that Bcl-xL regulates the extent of apoptosis after SCI. Apoptosis in the injured spinal cord correlated well with prompt decreases in Bcl-xL protein levels and Bcl-xL/Bax protein ratios at the contusion site. We interpret these results as evidence that regulation of Bcl-xL may play a role in neural sparing after spinal injury and pain-signaling function.     

Present situation and future aspects of spinal cord regeneration

The central nervous system (CNS) has a limited capacity for regeneration after injury. In spinal cord injury (SCI) patients, total loss of all motor and sensory function occurs below the level of injury. Advances in treatment are expected for orthopedic and spinal surgeons. Recently, evidence of axonal regeneration and functional recovery has been reported in animal spinal cord injury models. Our studies on the roles of inhibitory molecules with a comparison between neonatal and adult animals may help serve as therapeutic targets to enhance axonal regeneration for the injured spinal cord. Also, our cell replacement study indicates the possibility of transplanting neural stem cells to supply the cell source for immature oligodendrocytes, which are thought to be essential for both the myelination and trophic support of regenerating axons in the spinal cord. Administration of neurotrophic factors, prevention of inhibitory factors, and stem cell technology have clinical applications in SCI patients. However, spinal cord regeneration involves a multistep process, and several factors have to be controlled after injury. A combination of several treatments could overcome a nonpermissive environment for spinal cord regeneration. Further understanding of the mechanisms and finding optimal targets of spinal cord regeneration are necessary to obtain successful therapies for SCI patients.Presented at the 76th Annual Meeting of the Japanese Orthopaedic Association, Kanazawa, Japan, May 23, 2003     

Wnt信号通路与骨关节炎

Wnt信号通路广泛地存在于各种属生物体中,调节控制着许多生命过程,如细胞形态与功能的分化及维持、免疫、应激、凋亡等。随着对其研究的不断深入,发现Wnt信号通路对早期软骨的化生与形成、体外软骨细胞的增殖与分化具有重要的作用,并已成为骨关节炎(osteoarthritis,OA)发病机制研究的新热点。     

钙调素拮抗剂对大鼠脊髓损伤的作用及意义

目的观察钙调素（ＣａＭ）特异性拮抗剂三氟啦嗪（ＴＦＰ）对脊髓损伤（ＳＣＩ）的影响,探讨ＣａＭ在ＳＣＩ病理机制中的作用。方法采用氢清除法、斜板试验和电生理技术,以６４只大鼠为实验对象观察ＴＦＰ对ＳＣＩ后脊髓血流量（ＳＣＢＦ）、运动功能和诱发电位（ＭＥＰ）的影响。结果在肾上腺素维持系统动脉压的条件下,ＴＦＰ可明显改善ＳＣＩ后ＳＣＢＦ、ＭＥＰ和运动功能。结论ＣａＭ拮抗剂对ＳＣＩ具有保护作用,ＣａＭ可能是参与ＳＣＩ病理机制的重要因素     

Down-regulation of the Wnt, estrogen receptor, insulin-like growth factor-I, and bone morphogenetic protein pathways in osteoblasts from rats with chronic spinal cord injury

Objectives

To investigate the anabolic response of osteoblasts to chronic spinal cord injury and to identify potential signaling pathways that are associated with the osteogenic response after spinal cord injury by using in-house microarray analyses in osteoblasts.

Methods

Ten young male Sprague-Dawley rats were randomized into spinal cord injury (SCI) and SHAM groups. The tibiae were assessed for DXA and bone histomorphometry, and osteoblasts from femora were used for microarray analysis.

Results

SCI rats showed lower BMD and deteriorated microstructure in the proximal tibiae as compared with SHAM rats. The Wnt, BMP/TGF, estrogen receptor (ER), and IGF-I pathways were down-regulated in osteoblasts from spinal cord-injured rats.

Conclusion

Down-regulation of the Wnt, BMP/TGF, ER, and growth hormone/IGF-I pathways is associated with decreased bone formation after spinal cord injury.     

FasL, Fas, and death-inducing signaling complex (DISC) proteins are recruited to membrane rafts after spinal cord injury

The Fas/CD95 receptor-ligand system plays an essential role in apoptosis that contributes to secondary damage after spinal cord injury (SCI), but the mechanism regulating the efficiency of FasL/Fas signaling in the central nervous system (CNS) is unknown. Here, FasL/Fas signaling complexes in membrane rafts were investigated in the spinal cord of adult female Fischer rats subjected to moderate cervical SCI and sham operation controls. In sham-operated animals, a portion of FasL, but not Fas was present in membrane rafts. SCI resulted in FasL and Fas translocation into membrane raft microdomains where Fas associates with the adaptor proteins Fas-associated death domain (FADD), caspase-8, cellular FLIP long form (cFLIPL ), and caspase-3, forming a death-inducing signaling complex (DISC). Moreover, SCI induced expression of Fas in clusters around the nucleus in both neurons and astrocytes. The formation of the DISC signaling platform leads to rapid activation of initiator caspase-8 and effector caspase-3, and the modification of signaling intermediates such as FADD and cFLIP(L) . Thus, FasL/Fas-mediated signaling after SCI is similar to Fas expressing Type I cell apoptosis.     

Neurogenesin-1基因促进脊髓损伤后功能修复的实验研究

目的 探讨Neurogenesin-1(Ng1)基因对脊髓损伤后功能恢复的影响.方法 将36只大鼠随机分为实验组和对照组,每组18只.采用改良Allen法制备大鼠胸10脊髓损伤模型后,通过Alzet微泵分别向实验组和对照组持续转染入Ng1重组质粒和空白质粒.术后各时间点BBB评分系统监测大鼠运动功能恢复情况,并于术后第2周和第4周时分别取材,应用神经细胞特异性免疫荧光双标染色和组织学观察Ng1基因对内源性神经干细胞分化的影响以及脊髓组织病理变化情况.结果 自损伤后1周起实验组大鼠的BBB评分明显高于对照组.组织学观察实验组脊髓形态恢复较好逐渐趋于正常.实验组脊髓组织中新分化的神经元细胞数较对照组明显增多,同时新分化的星型胶质细胞数显著减少.结论 Ng1基因能够诱导脊髓损伤后内源性神经干细胞分化为神经元,促进脊髓运动功能的修复.     

Neurogenesin-1基因促进脊髓损伤后功能修复的实验研究

目的 探讨Neurogenesin-1(Ng1)基因对脊髓损伤后功能恢复的影响.方法 将36只大鼠随机分为实验组和对照组,每组18只.采用改良Allen法制备大鼠胸10脊髓损伤模型后,通过Alzet微泵分别向实验组和对照组持续转染入Ng1重组质粒和空白质粒.术后各时间点BBB评分系统监测大鼠运动功能恢复情况,并于术后第2周和第4周时分别取材,应用神经细胞特异性免疫荧光双标染色和组织学观察Ng1基因对内源性神经干细胞分化的影响以及脊髓组织病理变化情况.结果 自损伤后1周起实验组大鼠的BBB评分明显高于对照组.组织学观察实验组脊髓形态恢复较好逐渐趋于正常.实验组脊髓组织中新分化的神经元细胞数较对照组明显增多,同时新分化的星型胶质细胞数显著减少.结论 Ng1基因能够诱导脊髓损伤后内源性神经干细胞分化为神经元,促进脊髓运动功能的修复.     

Neurogenesin-1基因促进脊髓损伤后功能修复的实验研究

目的 探讨Neurogenesin-1(Ng1)基因对脊髓损伤后功能恢复的影响.方法 将36只大鼠随机分为实验组和对照组,每组18只.采用改良Allen法制备大鼠胸10脊髓损伤模型后,通过Alzet微泵分别向实验组和对照组持续转染入Ng1重组质粒和空白质粒.术后各时间点BBB评分系统监测大鼠运动功能恢复情况,并于术后第2周和第4周时分别取材,应用神经细胞特异性免疫荧光双标染色和组织学观察Ng1基因对内源性神经干细胞分化的影响以及脊髓组织病理变化情况.结果 自损伤后1周起实验组大鼠的BBB评分明显高于对照组.组织学观察实验组脊髓形态恢复较好逐渐趋于正常.实验组脊髓组织中新分化的神经元细胞数较对照组明显增多,同时新分化的星型胶质细胞数显著减少.结论 Ng1基因能够诱导脊髓损伤后内源性神经干细胞分化为神经元,促进脊髓运动功能的修复.