Podcasts 科学播客 | 「单次“表观遗传”治疗能控制高胆固醇血症吗？」

Nick Petrić Howe

High cholesterol affects millions of people worldwide, increasing their risk of heart disease. To reduce cholesterol many people take statins, but these drugs have to be taken every single day which can be a burden. But maybe that won’t always be the case. A new paper in Nature shows a step towards making a single treatment which could reduce cholesterol forever, by tweaking epigenetics. 

Epigenetics, in general terms, refers to the regulation of gene expression but does not change the DNA sequence itself. Instead epigenetic changes are controlled by things like methyl groups being added to DNA and can increase or decrease the expression of genes. The researchers hope to take advantage of this using a pharmaceutical intervention that contain molecules known as epigenetic effectors which influences genetic expression – in this case – silencing a particular gene that can cause disease. Now this has been shown to work well in cells in a dish, so in the new paper the team were interested to see if it would work in a full-fledged living organism. Their target was Pcsk9, a gene linked to high cholesterol. I asked one of the authors, Angelo Lombardo and asked him why the team picked this gene.

高胆固醇血症影响着全球数百万人，增加了他们患心脏病的风险。为了降低血浆胆固醇水平，许多人服用他汀类药物，但这些药物需要天天服用，这对患者来说可能是个负担。不过，这种情况或许不会一直如此。一篇发表在《Nature》杂志上的新论文尝试研发一种可以永久降低胆固醇水平的单次治疗方法，该方法通过调控表观遗传来实现。表观遗传从广义上来说是指在不改变DNA序列的基础上调控基因表达。实际上，调控表观遗传是通过诸如DNA甲基化修饰等方式来改变基因表达的。研究人员希望利用这一机制，引入一种含有“表观遗传效应器”的药物干预基因表达——（在本研究中）即沉默一个可能引发疾病的特定基因。目前，这种方法在细胞实验中表现良好，因此该团队在新论文中希望测试它在活体动物中是否同样有效。他们的目标是Pcsk9基因，这是一个诱导高胆固醇血症的基因。我询问了该论文作者之一的Angelo Lombardo，为什么他们团队选择了这个基因。

Angelo Lombardo

Pcsk9 is a modern gene actually it has been used since quite many years, actually. So it’s a well-known gene that needs to be shut off to decrease the level of cholesterol in the blood. So that was a very, let's say, nice and convenient gene to target for this specific group of physical experiments which actually, the biggest question was, is that the genetic technology that we are using sufficient enough now to silence a gene in a living organism for a long period of time.

Pcsk9 是一个近年来广泛研究的基因，已经被使用了相当长的时间。众所周知，沉默它可以降低血液中的胆固醇水平。因此，Pcsk9是一个非常理想的靶基因。而这个实验的最大问题是，我们所使用的基因技术是否足够成熟，是否能够实现在活体动物中长时间沉默一个基因。

Nick Petrić Howe

And in this paper, you tried to do this silencing in a mouse model. What was your approach?

在这篇论文中，你们尝试对小鼠模型进行基因沉默。你们采用了什么方法？

Angelo Lombardo

Well the approach is, well, similar to COVID the see so we exploited lipid nanoparticles to encapsulate messenger RNA that qualify for these epigenetic effectors and injected them into mice. So we're not discussing about or talking about vaccination in this specific case, we're talking about transient expression in the liver, which is the organ target, in this specific case, to Pcsk9 transient suppression of these epigenetic effector.

这个方法，嗯，有点类似于新冠疫苗的思路，我们利用脂质纳米颗粒来包裹能够发挥表观遗传作用的信使RNA（mRNA），并将其注射到小鼠体内。mRNA在肝脏内介导特定表观遗传编辑蛋白的瞬时表达（肝脏是本案例中的靶器官），以实现对Pcsk9基因表观遗传效应的短期抑制。

Nick Petrić Howe

As you said, you were trying to see if you could get sort of long-term silencing or less expression of that particular gene, how successful were you in that?

正如你所说，你们是想看看是否能实现该基因的长期沉默或减少其表达，那么你们在这方面取得了多大成功？

Angelo Lombardo

We were quite successful actually, we can achieve significant level of reduction of Pcsk9. The level of reduction that we achieved, were also linked to the delivery that they use, in this case on the specific lipid nanoparticle that we that we use in our study. We haven't yet reached 100% of repression, we were confident that playing with the delivery with the particles that we use, we can further increase efficiencies.

实际上，我们相当成功，能够显著降低Pcsk9的表达水平。基因表达的降幅与使用的递送方法有关，在这项研究中我们使用了特定的脂质纳米颗粒。虽然尚未实现100%的抑制效果，但我们有信心，通过调整递送方式和使用的颗粒，能够进一步提高效率。

Nick Petrić Howe

And in the paper, you were able to show that this sort of epigenetic silencing this repression of the genes happened for a whole year for the mice. But you know, I would have thought that as cells divide, maybe they wouldn't have these epigenetic marks on them still. So did you need to like reapply this at any point? Or was this just a case of one and done?

在这篇论文中，通过表观遗传学沉默基因的效果在小鼠体内持续了一整年。但是我原本以为随着细胞分裂，这些表观遗传标记可能会消失。那么你们是否需要在某个阶段重新施加处理，还是说只需一次处理就可以完成？

Angelo Lombardo

Well, in this study, not only we follow the mice for one year, but you also perform a surgical procedure which actually activates liver proliferation. You know, liver is a highly regenerative organ when damage and these regeneration implies a significant proliferation of liver petasites And also in that specific experimental context, actually digitally signs in remain stable, indicating really that the epigenetic modification imposed by the technology were, indeed editable. So you hit once it says, memorised that you silence the gene. And these memory remains also to the daughter cells.

在这项研究中，我们不仅跟踪了小鼠长达一年，还进行了外科手术激活肝脏的增殖。众所周知，肝脏是一个高度再生的器官，在受损时会进行显著的细胞增殖。而在这种特定的实验条件下，表观遗传标记依然保持稳定，这表明通过这项技术引入的表观遗传修饰确实是可遗传的。也就是说，一旦你沉默了基因，它就会被“记住”，这种记忆还会传递给子代细胞。

Nick Petrić Howe

And so you showed this occurred for a year. But do you suspect that this would last much longer than that?

这种效果持续了一年，你认为它可能会持续更久吗？

Angelo Lombardo

That’s the hope, of course, actually, the epigenetic proteins that we use in our editors, they do come from a complex of protein, which is active early during embryogenesis. And these complex of proteins silence endogenous retroelements or retroviruses, which are spread throughout our genome. And the silencing falls early during development in the first same moment of life. Weeks, if not months of life, these epigenetic information are then propagated throughout the entire life of an individual. So I think that's an interesting parallelism, you know, with our technology, and hopefully, also our technology will do the very same, so it wants and then for the entire life of the …..,

我们当然希望能持续更久。实际上，实验中涉及的表观遗传编辑蛋白来源于一种在胚胎发育早期活跃的蛋白复合物。这些蛋白复合物会在生命的初期阶段沉默内源性逆转录元件或逆转录病毒。而这些表观遗传信息随后会在个体的整个生命中得以延续。所以，我认为这与我们的技术形成了一个有趣的类比，希望我们的技术也能做到这一点——只需一次干预，便可在个体的整个生命中持续发挥作用。

Nick Petrić Howe

What do you think that this shows is possible?

你认为这表明了什么可能性？

Angelo Lombardo

I think that's the first time to our knowledge, at least that someone showed that this transient expression of these proteins is sufficient to impose long lasting no and efficient epigenetic science. So that opens basically, the possibility of using the platform more broadly than before. And then before was proof of principle of the activity of the platform in cell lines. So now that we have indication that this pattern was also in Devo open up so many, many different possibilities.

我认为这是首次发现表观遗传编辑蛋白的短暂表达足以实现长期且有效的表观遗传沉默，这就意味着推广该技术应用范围的可能性大大增加。之前我们只是证明了表观遗传治疗在细胞中的有效性，有了活体动物的尝试，这就开启了许多不同的可能性。

Nick Petrić Howe

And obviously, in this study, you looked at this gene that's associated with cholesterol, like a lot of people use statins in order to control their cholesterol levels. Could this be an alternative to that?

显然，在这项研究中，你们关注了与高胆固醇血症相关的基因。目前很多患者使用他汀类药物来控制血浆胆固醇水平，你觉得这项研究的结果是否可以成为一种替代方案？

Angelo Lombardo

Yes, it might well be. So, well the advantage here is that is a single, one and done treatment. So single treatment, instead of taking pills every day, you make a single treatment, and you achieve long-term reduction of Pcsk9 and has no reduction of your blood cholesterol. There are also other editing technology that are similar to this. So can inactivate the gene stably, like for instance, gene editing no, by– by conventional CRISPR cast. An advantage of our technologies is that we are not cleaning the DNA so genome– genome editing acts on the primary DNA sequence by cleaning the double stranded helix of the DNA, this cleavage of the double strand helix may come with some potential no, adverse events, outcomes that probably our technology may have solved. There is another advantage actually, in our technology that there is a potential to revert, eventually, these epigenetic marks that we deposed, so epigenetics can be the cause, and then also eventually reverted sort of antidote eventually.

是的，这确实有可能。其优势在于这是一种“一次性”的治疗方式。也就是说，使用单次治疗而不是每天服药，可以实现长期减少Pcsk9表达，从而降低血胆固醇水平的效果。此外，还有其他类似的基因编辑技术，例如传统的CRISPR/Cas9基因编辑技术，这些技术可以稳定地敲除基因。然而，表观遗传编辑的一个优势是，它不涉及直接切割DNA。基因组编辑通过切割DNA的双链螺旋作用于原始DNA序列，这种切割可能会带来一些潜在的不良事件，而我们的技术可能可以回避这些不良事件。另一个实际的优势是，我们的技术有可能最终逆转某些基因表观遗传标记，使其成为某种解药。

Nick Petrić Howe

What might we need to do now in order to make this a reality to be used in treatment? This is a mouse study, what do we need to do to sort of scale it up to be used in humans?

为了将这项研究成果转化为实际治疗，我们需要做些什么呢？这是一个小鼠研究，我们还需要做什么才能将其推广应用到人类身上？

Angelo Lombardo

Well first of all, we need to identify effective and safe reagents to silence the human gene. We are still dealing with species specific reagents, the ones that we have used have been designed to recognise the mouse genome. So we need to identify and develop now reagents that can do the very same in the human genome, and then try to scale up the process to move first eventually, in other animal models, bigger animal models, again, to test the efficacy and safety did eventually in human beings.

首先，我们需要找到有效且安全的试剂来沉默人类基因。目前我们使用的试剂是针对小鼠基因组设计的，我们需要开发出能够对人类基因组同样有效的试剂。接下来，我们需要循序渐进，首先在其他较大的动物模型中进行测试，然后最终进行人体试验，以验证其效果和安全性。

Nick Petrić Howe

That was Angelo Lombardo, from the San Raffaele Telethon Institute for Gene Therapy, in Italy. For more on that story, check out a link to the paper in the show notes.

这位是来自意大利San Raffaele Telethon基因治疗研究所的Angelo Lombardo。想了解这个故事的更多信息，请查看节目备注中的论文链接。