Esteban Hoijman: "I swapped architecture and anthropology for science"

Esteban Hoijman is a developmental cell mechanics biologist thanks to a philosophy teacher who spoke to him about HIV, the virus that causes AIDS. Hoijman obtained his degree and doctorate in biological sciences at the University of Buenos Aires (Argentina) and specialised in advanced microscopy, research into the zebra fish and mechanobiology at the University of Buenos Aires’ Centro de Microscopía Avanzada and in the Hubrecht Institute (Netherlands). He undertook his first post-doctorate at Barcelona’s Pompeu Fabra University, where he developed a system to obtain images of cellular dynamics during the morphogenesis of tissues in live embryos. For his second post-doctorate, in 2017, he joined Verena Ruprecht’s group at the Centre for Genomic Regulation, where he brought his previous experience in images of individual cells within live embryos and his knowledge of epithelial biology and cell death. While there, he discovered a phagocyte capable of eliminating defective stem cells of embryos at an early stage before development of the immune system, revealing an earlier protective function of a tissue during ontogenesis (Hoijman et al. Nature2021; featured in Nature Reviews Molecular Cell Biology). In 2021 he joined the University of Barcelona as Serra Hunter Lecturer Professor and head of group and was recently awarded a grant from the Spanish Ministry of Science and Innovation.

You were going to be an architect or an anthropologist. What happened?

It was thanks to a philosophy teacher who one day decided to explain some things about biology that I found incredible. He explained how HIV works, how it affected the organism, its mechanisms to infect a cell and so on. I was hooked! I swapped architecture and anthropology for science. Those talks about the mechanisms of biology in general, and HIV in particular, awoke an interest in biology that I have never lost.

Now you have your own group at the University of Barcelona-IBIDELL…

We started off studying embryonic development and how embryos and tissues in general can defend themselves from problematic situations like stress, independently of the immune system’s function; how they are able to protect themselves from different types of disturbance. Although we focus on the embryo, we are also interested in other tissues and adult organs.

What differences are there between being in a group and having your own group?

It is a difficult situation that depends on several factors, like the available funding. Being the head of a group implies taking on a lot of tasks that are almost entrepreneurial, for which we do not have much training, but if you are in an institution with resources, it is easier to delegate to other people. If, on the other hand, those resources are not available, you have to do that type of task yourself, which is a difficult challenge. However, that challenge motivates you to continue, to develop more ideas.

What qualities do you look for in a researcher?

The only essential requirement is, of course, that they have a great interest in what they are going to do, and by that, I mean passion. And that they have it for any task they are going to carry out, whether it is research or something more technical. Passion for science is undebatable.

I give my all, but not only for the objectives we are going to achieve, which are important, but for the work in itself. What motivates me is the task of discovering, researching. So, anyone who is very capable and gets the top marks but is not interested in what they do, is never going to fit into my group. However, for a person who is really motivated, although they find some things more difficult, I personally will find a way to get the best out of them. Of course, we need the best people in my group, but the indispensable requirement is that they have to come with a passion for what they do. In most cases, research is not an activity where you earn a lot of money. It is not where people are going to get fame or anything like it; it is a very vocational task.

This vocational task is something I see in all of the researchers I admire: they have that great passion for research itself.

Regeneration, how it works and how to promote it. How long have you wanted to study this field?

I always had it clear that I was interested in embryonic development, how structures are formed. At first, I was attracted by the idea of building houses, but I changed that for building biological structures. The field of regeneration is also highly related with early development, which is no other than forming structures from the zero of embryonic development.

What similarities are there between embryo development and the processes of regeneration in adults?

They are not dissimilar, although there are some differences that are so important, they mean that, as adults, we are not capable of regenerating and producing tissues or parts of organs as well as we did during the embryonic development phase. However, they share many structures, and that is basically why advances in regeneration mechanisms are based on the knowledge of embryonic development mechanisms. We know that signalling molecules, the genes that determine processes, are the same, but there are small differences that change everything. Animal regeneration models are very important. There are animals that can regenerate their hearts, like a fish, and even others that can regenerate a head, like worms. This animal, as an adult, retains the capacity of embryonic development.

From a functional perspective, although they have some differences, the heart of a fish and the heart of a human share many similarities. The question is to find out why humans cannot regenerate like a fish. If we find out what these small differences are, we can try to bridge the gap and determine how to regenerate ourselves.

Is it true that the more complex an organism, the less the regenerative capacity?

A bit. There is a lot of evidence to suggest that complexity is what hinders the capacity to regenerate, although I think that it is not the only explanation. We are missing some links that we still don’t understand. Of course, as we find out more and see that there are genes that are silenced, genes that stop being expressed in an adult, the fact of expressing them again would require reactivating programmes that we don’t want to activate because, for instance, they could be dangerous and produce differentiation or pathological proliferation in tissues.

What other lines of research are you pursuing in your laboratory?

My laboratory basically focuses on trying to study how one type of tissue, the epithelial, is able to carry out immune functions. The immune system has different functions; not only to defend us against infectious agents, but also, for instance, to combat carcinogenic cells, eliminate them, etc. It also destroys the cells that die in a tissue, whether due to normal replacement that occurs in all tissues or due to occasional damage. And we have known for some time that epithelial tissues are capable of participating in this function of elimination.

What we discovered is that at a very primigenious phase the embryo has an epithelium that carries out a protective role, because it is able to eliminate the cells that die in its interior. This happens at a stage in which the embryo does not have any immune cells and apparently no cellular differentiation. In the embryonic context, what we are asking is whether this epithelium is capable of protecting the embryo when there is no immune system. It would be something like an immune system. In fact, it is the first tissue formed in all vertebrates, including humans. And among other functions it has the capacity to protect the embryo in some way. That means, the first thing formed is a tissue that protects the embryo itself.

We are now attempting to analyse whether this function of epithelial cells is also present in adult organs. We were interested to study how the embryo can respond to stress and whether it can defend itself, and what we were able to observe, because we filmed the dynamics, is how this process changes over time.

From a functional perspective, although they have some differences, the heart of a fish and the heart of a human share many similarities. The question is to find out why humans cannot regenerate like a fish. If we find out what the small differences are, we can try to bridge the gap and determine how to regenerate ourselves

Do you think there is a generational gap between today’s researchers and your generation?

I notice a change that is related to several factors. On the one hand, it seems that opportunities in the world of science have become limited in recent years because the number of people who are devoted to research has increased a lot; what I mean is that there has been an increase in the number of researchers, but not in the number of group leaders. There are also a lot of regulations related to very high requirements, not only to be successful, if by being successful we understand being able to do relevant research, but simply to survive in the field of science.

There is a science policy, not only in Spain, but in general, which decides that there has to be a very limited number of research groups, which reduces the space for all people who want to research. Not only that, but there also has to be a limited number of research groups.

But, in contrast, many researchers see that their future is too difficult because they have to work, without rest, seven days a week, including weekends, for a very low salary, and that doesn’t even guarantee that you’ll necessarily be able to remain in the world of science, because it depends on chance as well as, of course, on capacity and effort. But there are times that capacity and effort are not enough.

Likewise, there is the historical perception that a researcher has to suffer, that it is a part of their lives. Before, it was something that was acceptable, but I think it is right that younger generations question their working conditions, which should be better, and demand a code of ethics, something that is respected in other areas but in the field of science, sometimes, not so much.

Regardless of the reasons I have just mentioned, there may be other reasons, such as it being a generation that wants things more quickly or more easily. There are some aspects that can be overcome and others that cannot, like cultural ones.

Do you think there is enough information about career options during the university years?

As a university professor, I come into contact with students, and in some cases I see many professors who have an outdated view of education. There are some structures that could be renovated or modified in terms of university teaching, which would make students more motivated and not so downhearted.

As a researcher, have you always been able to work on your own ideas?

In my case, yes, but it was not always like that since it depends on the context. I have found research groups that have allowed me to do what I wanted. I haven’t encountered difficulty in developing my own ideas.

But we can’t forget that in science there is a logic that establishes very hierarchical structures, with a head of group who makes all of the decisions, followed by the people who work in the group. In my opinion, this hierarchy should be eliminated. There are very talented people who do not necessarily have to be the ones who lead a group; however, the head of group should be the person who is the best manager. Sometimes in research, tasks of group management are superimposed on tasks of generating ideas, which seems to me to be a conceptual mistake. The person who is going to have the best ideas is not necessarily the best team leader. Now, here we’re talking about a deeper transformation of the structure of how science works in the world.

There is an idea that if you are not the head of your own group by a certain age, your scientific career is stagnant.

That’s true. In any company, the director is not the person who knows the technical details of how things work. There could be a manager who manages very well, but within the group there must be other people who have the scientific ideas and carry them out without managing aspects of organisation, administration, finance, etc. In any case, the head of group has to do many of these tasks without necessarily knowing how to do them or perform them in the most efficient way.

Nowadays, there is a constant fight for resources because the person who has to get the funding is the person who has to have the ideas. It is possible to have a strategy that gets funding based on the ideas of another person and a division of tasks would make this process more efficient.

Esteban Hoijman presented the seminar “Epithelial surveillance of stem cells: imaging embryonic dynamics across scales,” at the invitation of Dr. Miguel Torres.