Meet Ariel Waisman. 

Why don't mammalian hearts regenerate? What happens during the formation of the heart that shuts down its cells' ability to divide and repair? These are the fundamental questions at the core of Ariel Waisman’s research.

From the Discovery Channel to stem cells 

Ariel’s path into developmental biology was driven by a deep curiosity about the natural world. Growing up in Buenos Aires, Argentina, he was strongly influenced by his father’s passion for science fiction and space. Although he was not always the most dedicated student in his early teenage years, documentaries on the Discovery Channel about DNA and animals, little by little, sparked a lasting interest in biology.

He completed his rigorous seven-year Biology degree at the University of Buenos Aires, exploring a wide range of topics, from plant molecular biology to virology, before finding his home in stem cell research. During his undergraduate studies, PhD, and part of his postdoc, he studied mouse embryonic stem cells, aiming to find a relationship between cell cycle events, like DNA replication and mitosis, and the epigenetic transformations that lead to changes in cell identity during differentiation. Along the way, he discovered that this seemingly simple question was not easy at all to answer. 

A major challenge was that he had to establish most of the necessary techniques himself. This included developing a neural differentiation model, generating reporter lines to track the cell cycle, finding ways to synchronize cells, setting up time-lapse experiments, and learning to program in Python to analyze complex datasets. In retrospect, this experience provided him with a broad and versatile technical foundation that continues to shape his work today.

Later, as a Fulbright fellow at Rockefeller University in the lab of Dr. Ali Brivanlou, Ariel  encountered a different perspective on developmental biology, one in which stem cells played a central role. He also attended the Embryology course at the Marine Biological Laboratory in  Woods Hole (2019),where he deepened his understanding of how developmental principles connect to stem cell biology and met incredible people he remains close to today. These experiences clarified his scientific direction: to study mammalian development and regeneration using pluripotent stem cells. After his PhD in Argentina, he transitioned to human stem cells and cardiac differentiation, captivated by a central question: why don't mammalian hearts regenerate? A key part of the answer is that mature cardiomyocytes stop dividing after birth. This question felt like a natural extension of his earlier work, now in a different biological context and with clear translational relevance. 

“Moving from mouse to human cells and from basic pluripotency biology to cardiac regeneration was motivated by both scientific fascination and a strategic decision to find a niche where I could build something unique. Of course, transitioning into cardiac biology also meant I had a lot to learn, and I still do every day. But I genuinely enjoy that challenge. I believe doing science is, at its core, a commitment to never stop learning.”

Building a lab in Buenos Aires: unlocking the heart’s capacity to heal

During embryonic development, cardiomyocytes proliferate actively, and early postnatal mammals retain the capacity for full cardiac regeneration. Something changes during maturation that shuts down this potential. Identifying that mechanism and determining whether it can be reversed are the driving forces behind Ariel’s research. Nevertheless, addressing these questions presents significant challenges: Mature cardiomyocytes are complex cells; they are binucleated, polyploid, and undergo deep metabolic changes, making their proliferative behavior difficult to study with conventional tools. While many studies rely on immature, embryonic-like cardiomyocytes, understanding why adult cells fail to proliferate requires models that closely resemble mature cells. For this reason, Ariel and his research group are developing maturation protocols that push human pluripotent stem cell-derived cardiomyocytes toward a postnatal phenotype with mature metabolism, sarcomere organization, and electrophysiology. Achieving this level of maturity is essential for accurately modeling cardiac regeneration, and there is still much work to do.

"We are building new approaches, combining reporter cell lines, automated imaging, and computational analysis, to rigorously assess whether these cells can be pushed to truly divide again.”

His group is part of the Stem Cells Institute (LIAN) at FLENI (Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia), a private, non-profit neurological hospital in Buenos Aires. He leads a growing team of seven people, including PhD students and undergraduate trainees. What makes FLENI special, particularly in Argentina, is its active support of basic research. While most science in the country depends entirely on public funding, FLENI provides institutional backing and infrastructure that are essential for working with human pluripotent stem cells, which is inherently expensive and technically demanding. LIAN hosts five independent groups working with human pluripotent stem cells in cardiac and neural differentiation, creating a collaborative ecosystem of about 30 researchers. This critical mass is unique in the region and means that their students benefit from shared expertise, joint seminars, and a culture of collective problem-solving that would be impossible to replicate working in isolation. Within this environment, Ariel is creating a lab environment where rigor and warmth coexist.

“I want my students to feel comfortable asking questions, challenging ideas, and bringing their whole selves to work while also holding each other to high standards of scientific integrity. I believe the best science comes from groups where people genuinely enjoy working together, and building that culture is something I take as seriously as the research itself.”

One of the main challenges he faced when establishing his lab was narrowing down his scientific interests. He mentioned, “During the initial setup of my group, I had many simultaneous interests I wanted to pursue. Cardiac differentiation and regeneration using human pluripotent stem cells were always central, but I wanted to continue projects with mouse cells; I was also very interested in developmental tempo between species using mouse and human cells, and I was establishing naive human pluripotent stem cell culture and placental differentiation.” Over time, he recognized that spreading efforts across too many areas made it difficult to develop deep expertise, something essential for early-career group leaders.

Championing Science in the Global South

Ariel decided to build his independent career in Argentina rather than moving abroad. He strongly believes in the potential of Latin American students and feels a strong responsibility to train the next generation of scientists locally. Ariel also embraces the unique resilience required to do science amidst the region's challenges: limited funding, delayed reagents, economic instability, and the political landscape. However, he mentions that these challenges also foster creativity and strategic thinking.

“I believe Latin America has incredibly talented and motivated students who deserve access to cutting-edge research without having to leave their countries. If all of us leave, who trains the next generation? I take that responsibility seriously. I also think there is real scientific value in working from this region: the constraints force you to be creative, resourceful, and strategic in ways that shape you as a scientist. You learn to do a lot with little, and that makes you appreciate every experiment and think harder about what questions are truly worth pursuing.”

Self-care as a base of good mentorship 

Beyond the bench, Ariel is navigating the beautifully complex challenge of raising his three-year-old son while growing his lab. This balancing act was especially demanding in the beginning; just as he was establishing his group, his son required multiple surgeries during his first year. This limited Ariel's presence in the lab at a critical time when his first students were just starting their projects.

“I stayed present as much as I could, mostly online, but it was an incredibly demanding time. It taught me a lot about combining a scientific career with family life and about the importance of having students and colleagues you can trust. What helps me is trying to be intentional about boundaries, even imperfect ones. When I'm at home, I try to be present with my family, and when I'm at the lab, I try to make that time count. I also make sure to keep some space for myself.”

He emphasizes that self-care, such as maintaining his regular swimming routine, and family time are not luxuries but absolute components for being both a supportive mentor and scientist. 

“I think the key is accepting that perfect balance doesn't exist. Some weeks the lab demands more, some weeks the family does, and the goal is to make sure neither one loses for too long. I also think it's important to talk about this openly, especially with students, so they know that building a scientific career and having a personal life are not mutually exclusive, even if combining them takes effort and a fair amount of improvisation.”