脂肪干细胞移植治疗脊髓损伤研究进展

丛培芳， 柳云恩， 张玉彪， 佟昌慈， 史秀云， 刘 颖， 毛 舜， 佟 周， 施 琳， 金红旭， 侯明晓

沈阳军区总医院 急诊医学部 全军重症(战)创伤救治中心实验室 辽宁省重症创伤和器官保护重点实验室，辽宁 沈阳 110016

·干细胞研究·

脂肪干细胞移植治疗脊髓损伤研究进展

丛培芳， 柳云恩， 张玉彪， 佟昌慈， 史秀云， 刘 颖， 毛 舜，
佟 周， 施 琳， 金红旭， 侯明晓

沈阳军区总医院 急诊医学部 全军重症(战)创伤救治中心实验室 辽宁省重症创伤和器官保护重点实验室，辽宁 沈阳 110016

脂肪干细胞； 脊髓损伤； 血脊髓屏障

Adipose-derived stem cells； Spinal cord indury； Blood spinal cord barrier

脊髓损伤(spinal cord injury，SCI)由于其损伤位置的特殊性，常导致损伤平面以下肢体不可逆的神经功能丧失，造成截瘫、四肢瘫等严重的并发症，给工作和生活带来毁灭性的打击，同时，也为社会带来沉重的经济负担[1]。目前，我国经济的不断发展，机动车事故、跌倒以及暴力行为等造成的SCI患者不断增加，而治疗却仅限于早期使用大剂量类固醇和急性外科干预，以尽量减少脊髓水肿和随后的继发性或迟发性损伤[2-4]。因此，寻找治疗SCI的有效手段已经成为现代医学工作者需要面对的一大难题。

脂肪组织是一种高度特化的结缔组织，是指成熟的脂肪细胞在体内聚集成团，由薄层疏松结缔组织分隔成小叶，不均匀地分布在身体的各个部位，并有机械性和审美功能。其在体内含量丰富，含有的干祖细胞能够分化为成骨细胞、软骨细胞、脂肪细胞谱系等[5]。近年来，干细胞以其向多种组织细胞分化的能力而成为多种机体损伤的治疗热点，与骨髓间充质干细胞和脐带血干细胞等其他种类的干细胞相比，脂肪干细胞(adipose-derived stem cells，ADSCs)的获取方式更为便利，并且不受特定时间限制，可通过微创的吸脂术大量获取[6]。研究证实，ADSCs可以通过分泌各种细胞因子、调节炎症反应、改善缺氧、促进血管新生、抑制细胞凋亡或直接分化替代受损细胞，协同治疗难愈性创面、放射性膀胱损伤、放射性唾液腺损伤、造血功能障碍以及SCI等[7-12]。本研究就ADSCs治疗SCI方面的研究进展进行简单概述。

1 ADSCs的神经分化能力

神经细胞由于分化程度高，所以一旦受损，修复起来十分缓慢，严重时还可能造成不可修复的损伤。药物对于修复神经元的效果也不是十分理想，因此干细胞治疗中，其具有的神经分化能力对于SCI的修复十分重要。ADSCs具有很强的神经分化能力，其分化方法方便，分化率高[13-14]，分化后的细胞可表达巢蛋白和神经元特异性烯醇化酶等神经细胞特异性标志物，其形态也与神经细胞相似。而Ji等[15]的研究更进一步表明，在脑源性神经营养因子(brain-derived neurotrophic factor，BDNF)和神经营养因子-3(neurotrophin-3，NT-3)的诱导下，ADSCs更容易进行神经分化。

2 ADSCs与骨髓间质干细胞治疗SCI比较

一些研究发现，神经干细胞的标记物在骨髓间质干细胞(bone marrow derived mesenchymal stem cells，BMSCs)与ADSCs中也有存在，表明二者均有神经分化的潜能[16-17]。利用化学药物，如β-巯基乙醇、二甲基亚砜和叔丁基羟基茴香醚可以使BMSCs分化为神经球[18]，但分化中所使用的化学物质的毒性限制了其在临床试验中的使用[19]。因此，现在更多的使用碱性成纤维细胞生长因子和表皮生长因子进行神经分化诱导[20]。一直以来，BMSCs辅助治疗SCI的研究更多，在治疗中，BMSCs可以释放神经营养因子，减少白细胞介素-1β等炎症因子的表达，并减少凋亡反应的发生，行为学实验也证明其有助于SCI后功能的恢复，并且不良反应很小[21-25]。

ADSCs进行神经分化诱导的方法与BMSCs相同，但Chung等[26]研究发现，ADSCs具有更强的神经分化能力，在同等培养条件下，ADSCs可形成约500 μm的神经球，而骨髓干细胞仅能形成不到100 μm直径的神经球，因此，同等量的ADSCs与BMSCs进行神经诱导分化的效率更高，治疗效果也更好。另外，也有研究证实，相比于BMSCs，ADSCs表达BDNF、血管内皮细胞生长因子(vascular endothelial cell growth factor，VEGF)与肝细胞生长因子(hepatocyte growth factor，HGF)的水平更高，更有增殖速度快、不易老化以及运动功能恢复更好等优点[27]。

3 ADSCs治疗SCI的可能机制

ADSCs治疗SCI的可能机制中，其对血脊髓屏障的保护作用是其中之一。血脊髓屏障(blood spinal cord barrier，BSCB)主要由毛细血管基底膜、血管内皮细胞、星形胶质细胞等构成，对维持脊髓内环境的稳定、维持正常的神经功能具有重要作用。其在SCI中的破坏通常被认为是脊髓继发性损伤加重的重要原因[28- 29]。SCI发生后，ADSCs移植可能通过抑制过氧化物酶的表达和小胶质细胞的活化，减少继发性炎症反应和细胞凋亡，进而减少BSCB的破坏，促进大鼠后肢运动功能的恢复[30]。

缺氧、炎症因子、理化损伤和水肿等同样是造成SCI的原因[31-33]。多个研究表明，ADSCs可以通过分泌的前列腺素E2和白细胞介素-10并且抑制基质金属蛋白酶-9来进行免疫抑制，同时可以下调炎症反应，缓解疼痛[34-36]。而由于其神经分化的特性，ADSCs还可以分泌BDNF、亲胆碱能神经元因子(cholinergic neuronotrophic factor，CTNF)等神经营养因子，进一步的修复神经损伤，有助于后续肢体功能上的恢复[6,37-39]。

4 经神经营养因子修饰的ADSCs治疗脊髓损伤

ADSCs可以分泌神经生长因子帮助损伤修复，而近年来，经神经营养因子修饰的ADSCs治疗SCI更是研究的热点[40-42]。多个研究表明，经BDNF、17β-雌二醇和神经钙黏蛋白等修饰的ADSCs能进入受损脊髓组织内促进受损脊髓节段神经元的修复，促进轴突再生，并能有效缩短神经元的修复时间[43-46]。熊敏等[43]研究发现，ADSCs对于SCI大鼠可有显著的治疗效果，而经BDNF转染的ADSCs移植于SCI大鼠与单纯应用ADSCs治疗的SCI大鼠相比，其运动功能评分(Basso Beattie Bresnahan,BBB)明显更高，BDNF和神经生长因子的表达也更多，神经损伤标志物神经胶质纤维酸性蛋白的表达则被抑制，表明经BDNF转染的ADSCs治疗SCI大鼠，其神经结构以及神经功能恢复更好。

综上所述，ADSCs对于SCI的恢复具有积极作用，其易获得性、神经分化率高等特点相比于BMSCs而言，更有利于临床的应用。但其现今研究大都仍停留在实验室阶段，研究结果缺乏有效的临床数据的支持。有理由相信，随着研究的不断深入，ADSCs将在SCI治疗中发挥更大作用，为更多的患者带来福音。

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全军十二五面上项目(CSY12J002)；全军重大新药创制项目(2013ZX09J13109-02B)；全军十二五面上项目(CSY13J002)；总后卫生部重大新上(ASM14L008)

丛培芳(1987-)，女，辽宁沈阳人，药师，硕士

侯明晓，E-mail：houmingxiao188@163.com

2095-5561(2017)05-0298-04DOI∶10.16048/j.issn.2095-5561.2017.05.10

2017-09-08