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[交流分享] Nature News 干细胞治疗可能逆转多发性硬化症状

Nature News 干细胞治疗可能逆转多发性硬化症状

英文版:
       MS stem-cell trial shows promise - Multiple sclerosis treatment seems to reverse symptoms.
       Bone marrow stem cells may have helped patients with multiple sclerosis.
       A stem-cell therapy appears to help some patients with early-stage multiple sclerosis recover, according to results from a preliminary study.
       Multiple sclerosis (MS) is a chronic disease where the body's immune system attacks the central nervous system. White blood cells in the body attack the protective myelin sheaths surrounding nerve fibres in the brain and spinal cord. Although symptoms of the disease wax and wane, they generally grow worse over time and include fatigue, blurred vision and difficulty walking.
       In the new trial, the patients' immune cells were first destroyed and they were then injected with blood stem cells taken from their bone marrow. Seventeen of the 21 patients treated in his study improved, suffering fewer problems with their balance or vision, and none declined over the 2-4 years they took part in the study.        
       This marks the first time a technique "has actually shown reversal" of neurologic loss caused by this disease, says Richard Burt of Northwestern University in Chicago, who led the study.
       Normally, when MS drugs fail to calm the immune system, doctors may adapt a strategy currently used for blood cancers: a combination of toxins and radiation to destroy the bone marrow â??which contains the patient's blood-forming system â??followed by a transplant of healthy cells to restore it.
       Though such techniques can be effective, they carry the risk of serious side-effects and death.

Early chance
       The current work uses less toxic drugs to primarily kill one type of immune cell â??the white blood cells known as T-cells. Burt and colleagues were also able to administer the stem cells at earlier stages of MS, when the brain is more capable of repairing damage.
       Edwin McClure, a 24-year-old advertising student at Virginia Commonwealth University, was one of the patients treated. He says his neurologist referred him to the study after he'd tried "three different drugs over three years that were all pretty much ineffective". Before the study, he says, he had to give himself a shot every other day; nonetheless, fatigue, poor balance and dimmed vision limited his activities. Now, McClure says, he no longer has those problems or takes medications for MS.
       A lot of research suggests that the early "relapsing-remitting" stage of MS is the most treatable, says Patricia O'Looney, vice president for biomedical research at the National Multiple Sclerosis Society in New York. This is when the inflammation that destroys myelin sheaths is at its peak.        
       "To try to stop progression and loss of tissue, you have to try to get that inflammation under control," she says. Safer, earlier ways of destroying and replacing the immune system might do that, she says, but, she still recommends caution about the transplantation technique. "It's not an easy procedure," she says. "Although they are impressive results, it's a preliminary study."

Larger trial
       Burt's therapy is probably less toxic than other forms of intense immunosuppression, says Gianluigi Mancardi of University of Genova in Italy, who wrote a commentary accompanying the study2. But, he says, "Burt's therapy cannot be considered gentle, because there are certainly side-effects of some importance".
       Burt believes that the risk of death from this procedure is less than 1%. In comparison, the MS drug Tysabri (natalizumab), a monoclonal antibody, has about a 1 in 1000 chance of causing a serious viral infection, but those risks were considered so serious that it was initially withdrawn from sale by the manufacturer. It is now only prescribed under a special prescription programme in the United States and carries serious warnings in Europe.
Walter Royal, director of the Maryland Center for Multiple Sclerosis at the University of Maryland, Baltimore, highlights some of the study's strengths. He notes the researchers tried to control for the wide fluctuations often observed in MS, by recruiting patients only after their condition stabilized following a relapse. The patients were also monitored over an average of three years, he says, "which certainly was long enough to know if improvement was transient". Nonetheless, larger studies in multiple centres are now needed, particularly to assess risks, Royal adds.
Burt agrees that his team's study is small and lacked a control or comparison group. He is currently recruiting patients for a larger, randomized trial. Even if further work shows that the treatment is effective for the early stage of the disease, the technique does not help patients with later "progressive" MS, says Burt. Though bone marrow stem cells reboot the immune system, they cannot repair myelin after axons have been very badly damaged.


中文版:
干细胞治疗可能逆转多发性硬化症状

       骨髓干细胞可能对多发性硬化病人有帮助。一项前期试验表明,干细胞疗法可以帮助早期多发性硬化病人康复。
多发性硬化(MS)是自身免疫系统攻击中枢神经系统的慢性疾病。体内的白细攻击包绕在脑和脊髓神经纤维外的保护性髓鞘。虽然症状时好时坏,但经过一段时间还是逐渐恶化,包括疲劳、视力模糊和行走困难。
       在这个新的试验中,将先清除病人的免疫细胞,然后注入从自体骨髓动员出来的外周血干细胞。试验的21名病人中有17名得到改善,包括平衡功能和视力改善,且2-4年不等没有出现恶化。
       该研究带头人、西北大学的Richard Burt说,这标志着该项技术第一次成功逆转了MS引起的神经功能丢失。
       通常情况下,当抗MS药物对免疫系统的镇静作用失败时,医生会采用目前用来对抗白血病的疗法治疗MS:用化疗和放疗的方法摧毁骨髓造血系统,然后移植健康的细胞修复。虽然此方法有效,但副作用大,甚至可能死亡。

早期机会
       目前的工作是运用减毒性的药物主要杀灭一种被称为“T细胞”的免疫细胞。Burt和同事们同时尽可能的在大脑还具有修复损伤功能的时候及早给予干细胞治疗。
       弗吉尼亚大学的学生Edwin McClure,是其中的一位患MS的受试者。他说他的神经科医生推荐他参与该项试验,之前他3年内尝试了3种不同的疗法,但均效果不佳。他说,在此试验之前,他每隔一天就要进行一次注射,但是疲劳、平衡功能差和视力模糊任然限制了其活动。现在,McClure说他已经没有了这些毛病,也不用再服药了。
       很多研究表明早期的复发缓解型MS疗效最好,纽约国家多发性硬化生物医药研究协会副主席Patricia O'Looney说,因为这一时期是炎症损伤髓鞘最严重的时候。
       她说:“要想阻止疾病进展和组织丢失,必须控制炎症反应”。而越安全越早的摧毁和替代免疫系统能够做到。但她同时推荐对移植持谨慎态度。“这并不是一个容易的过程”她说,“虽然结果令人鼓舞,但毕竟还只是前期研究”。

大量试验
       Burt的疗法虽然相对于其他的高强度免疫抑制疗法毒性较低,但是任然具有一定的副作用,意大利Genova大学的Gianluigi Mancardi说。
       Burt相信这项试验的死亡率低于1%。相比而言,抗MS药Tysabri(那他珠单抗)有近1/1000的机会引起严重的病毒感染,生产商甚至开始的时候考虑到其严重性将其退出销售。现在该药在美国只出现在一些特殊的处方中,在欧洲运用也有告诫事项。
       马里兰大学多发性硬化治疗中心的Walter Royal主任强调了这次研究的强度。他说研究者通过选择那些复发后比较稳定的病人来控制MS病人的症状波动情况。治疗后对病人的观察达到了平均3年,以确保这种改善不是暂时的。尽管如此,仍需要进行大量的试验,特别是对安全性进行评价。
       Burt说他团队的这个试验是一组小的且缺乏对照组的试验。他目前正在招募病人以进行更大的随机试验。Burt说即使以后的结果显示该疗法对早期MS有效,也不能够治疗迟发型进行性MS。虽然骨髓干细胞能够重建免疫系统,但是不能在轴突严重损伤的情况下修复髓鞘。
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