《INTERNATIONAL CIRCULATION》: Before stem cell transplantation can become widely applicable， questions remain about the optimal site of delivery and timing of transplantation. There seems to be increasing evidence that intravascular cell delivery after stroke is a viable alternative to intracerebral transplantation. So which one is a more favorable site of delivery and why?
在广泛开展干细胞移植治疗之前，研究者对干细胞移植的方式和时机仍未达成共识。目前似乎有越来越多的证据显示，除了脑内移植这一途径以外，卒中后也可以考虑实施干细胞的血管内移植。您认为，哪一种移植方式更具优势？原因何在？

Dr. Lindvall: We are talking about two different objectives， one is， if you inject intravenously， you are delivering cells not to generate neurons in the brain， but you want to do other things like modulating inflammation or increasing angiogenesis. And that is something， of course， which we know that can be achieved but for example human mesenchymal stem cells. But if we want to， in my view， an efficient recovery of function， we must try to increase the number of neurons in the brain and to replace neurons and that can only be done if we either transplant stem cells into the brain or if we stimulate the formation of neurons from the brain阵 own neuronal stem cells. So if you want to do something modulating inflammation， it would be fine to do it with intravenous delivery. But that is not at all useful for replacing neurons in the stroke damaged brain.   
我们所说的是两种不同的移植目的。一种是静脉注射干细胞，其目的不是为了在脑中产生神经元，而是为了达到诸如调节炎症反应或是促进血管生成等目的。我们知道，采用人间充质干细胞就可以达到上述目的。但是，我认为，如果想有效恢复功能的话，就必须增加脑内神经元的数目，替换坏死神经元，这只有通过干细胞的脑内移植或者是刺激脑组织自身的神经干细胞分化成神经元才能够实现。因此，如果想要调节炎症反应的话，静脉输注干细胞是可以的。但是，对于替代卒中损伤脑组织中的神经元来说，则毫无帮助。

《INTERNATIONAL CIRCULATION》:Initially， it was thought that stem cell therapy work by a ’cell replacement’ mechanism. In recent years， a large body of evidence is emerging that other potential mechanisms may be involved in the action of cell-based therapies in stroke to improve the functional outcome.What is the progress in this field?
以往认为，干细胞通过“替代受损细胞”这一机制发挥治疗作用。但是近年来，大量证据提示，卒中后干细胞移植对功能的改善作用还有其他机制参与。该领域的进展有哪些？

Dr. Lindvall: I think you are absolutely right that stem cells apply as it has been over the past years mainly act not by neuronal replacement. And I think in the short term clinical trials would properly be done with mesenchymal stem cells delivered intravenously. But in the long term I am convinced that we have to develop stem therapies where you replace neurons. Now we know for example that you can generate neurons from different types of stem cells， then you can get them to survive in the stroke damage animal brain and they can also be functional and they can get the improvement. And now it is time to translate this into clinic but it will take long time because there is too much left to do. But that is I think ultimately， at the end， this is really very important to do.
你说的很有道理，在过去几年中，发现干细胞不仅仅是通过替代神经元发挥作用。我认为，从短期来讲，对于静脉输注间充质干细胞开展临床试验是没有问题的。但是，从长远上来看，我认为必须开发出能够替换神经元的干细胞治疗。目前，我们知道多种干细胞都可以分化为神经元，并且能够在卒中脑损伤的动物模型中得以存活和发挥功能，产生改善作用。现在应当开始将干细胞转入临床应用，但是还有很长一段时间才能够实现，因为还有很多问题需要解决。但是，我认为最终转入临床应用是非常重要的。

《INTERNATIONAL CIRCULATION》: Although stem cells hold great promise as a therapeutic strategy for many neurological diseases， their unlimited self-renewal and high differentiation potential poses the risk of tumor induction after engraftment. In what way can we reduce the tumorigenesis of stem cells and what are the recent findings with regarding to this issue?
尽管干细胞移植治疗对于很多神经系统疾病来讲都是非常有前景的治疗手段。但是，干细胞自身所具有的自我更新能力和高度分化潜能有导致移植后肿瘤形成的风险。我们该采取哪些手段来降低干细胞的成瘤性，该领域的进展有哪些？

Dr. Lindvall: Tumorgenesis is something that we have to solve when it comes to human embryonic stem cells and also these news induced pluripotent stem cells. They all have this problem. And there are several ideas how we can solve that problem. For example， by cell sorting， by manipulating the cells in different ways. So I am sure that this can be solved， but there is still a problem with present stem cells.
对于胚胎干细胞和新型的多能干细胞来说，成瘤性确实是个需要解决的问题。这些细胞都存在成瘤性的问题。目前解决成瘤性问题有几种方法。比如说进行细胞分选或者是采用不同的方法处理干细胞。我确信，成瘤性的问题能够得以解决，但是就目前的干细胞来讲，仍然存在成瘤性的问题。