Stellar Lab Radio – Episode 2
Guest: Dr. Yo Mabuchi
Inside our bodies lie mesenchymal stem cells. Research into unlocking their potential extends far beyond wound healing, opening unexpected possibilities such as the development of cultured meat and cell cultivation in space. In this episode of Stellar Lab Radio, we welcome Dr. Yo Mabuchi, Associate Professor at Fujita Health University, who is at the forefront of this exciting field.
Stellar Lab Radio is a talk program that shines a light on “world-changing research that no one knows yet.” Leading researchers from around the globe share their cutting-edge discoveries, the untold stories behind their breakthroughs, and their visions for the future.
In Part 1, Dr. Mabuchi walks us through the basics of stem cell research, the surprising stress resistance of cells, and the potential of organoid technology in creating “cultured meat.” We explore how fundamental research connects with broader societal challenges and future possibilities.
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The World’s Most Advanced Way to Identify Stem Cells
Sean: Today’s guest is Dr. Yo Mabuchi, Associate Professor at Fujita Health University. Dr. Mabuchi, welcome—it’s so nice to have you here today.
Mabuchi: Thank you very much. My name is Yo Mabuchi from Fujita Health University.
Sean: Great to have you. I can hardly imagine that anyone wouldn’t know you already (laughs), but just in case—could you start by telling us what kind of research you do?
Mabuchi: Sure. My research focuses on mesenchymal stem cells, which are a type of stem cell found in the body. These cells play roles such as supporting wound healing and suppressing inflammation. In other words, they’re one of the stem cell populations that everyone naturally carries inside their body.
Sean: Thank you. So, has this research always been your central theme?
Mabuchi: Yes, that’s always been at the core. I’ve branched into new projects along the way, but in one way or another, everything ties back to mesenchymal stem cells.
Sean: I see. Since I’ve been in touch with you for some time, I have some idea, but if someone unfamiliar with your work were to ask, “What’s the most impressive part of Dr. Mabuchi’s research?”—what would you say?
Mabuchi: Well, when people didn’t really understand mesenchymal stem cells very well, I painstakingly examined them one by one, screening the types of proteins expressed on their surface. Through this, I discovered that mesenchymal stem cells can be identified as those that simultaneously express two particular proteins. That became one of my key achievements. Thanks to this, if you use a cell-sorting machine, you can pick out a single stem cell with high precision. A few researchers around the world are doing this, but as of now, I hold what you might call the “world record”—I developed the most efficient method, and I’ve patented it.
Sean: That’s amazing. So, in a way, you’re like the “father of mesenchymal stem cells.” And researchers who study stem cells can now isolate them using your method, which means your approach may shape a lot of stem cell research going forward—is that right?
Mabuchi: That’s exactly what I hope. In fact, one of my former supervisors has already launched a startup based on this technique—it’s a technology for isolating human mesenchymal stem cells, now being advanced for medical applications. Knowing that my method might directly help people gives me great joy.
“What Separates a Healing Wound from One That Won’t Heal”
Sean: I believe your focus is on mesenchymal stem cells, or MSCs, and also on regenerative medicine that uses iPS cells, as well as disease modeling. Given how quickly research is advancing today, could you tell us what area you’re particularly focused on right now? Maybe we could even start with the basics—what exactly are mesenchymal stem cells?
Mabuchi: Of course. My research is on stem cells. Everyone has stem cells within their body, and they are cells with extraordinary potential. For example, they can proliferate and differentiate into various cell types. Medicine that harnesses these abilities is rapidly advancing now—what we often call regenerative medicine. Among the stem cells used in regenerative medicine, I focus on mesenchymal stem cells.
Take this example: when you get injured, Sean, sometimes the wound just heals on its own, right? That happens because the surrounding stem cells send out signals saying “there’s an injury,” and the wound heals in response. If you flip this around, it suggests that for large wounds that don’t heal naturally, adding mesenchymal stem cells could promote healing. Likewise, transplanting these cells could even help treat diseases that otherwise don’t heal. That’s the kind of research I’m doing.
Sean: Thank you. I think a lot of people misunderstand stem cells—they imagine they have to be taken from unborn babies, for instance. But from what you’re saying, stem cells already exist throughout our bodies, and they have powerful capabilities that help us when we’re injured. Is that a fair way to put it?
Mabuchi: Exactly. For example, when babies get injured, the wounds heal very quickly and without scars—that’s because they have a lot of stem cells. But as we age, injuries are more likely to leave scars. That difference comes from stem cell capacity. With age, the number of stem cells decreases bit by bit. The proportion goes down, but importantly, they do remain.
Sean: So rather than their “power” diminishing, it’s more that their numbers decrease somewhat—is that correct?
Mabuchi: Yes. Based on my research, the number of stem cells declines slightly. Even in older individuals, the highly capable cells are still there. Their functional capacity declines gradually, but they do persist.
Sean: I see. So earlier you mentioned that some wounds heal naturally, while larger ones may not. What determines whether a wound heals or doesn’t—and how does that connect with stem cells?
Cells That Can Withstand “Harassment”?
Mabuchi: One factor might be age. When you’re young, not only are your stem cells more active, but the surrounding blood supply and neighboring cells also play a role. Softer tissue and better blood flow make healing easier. Those differences matter a lot.
Recently, I’ve been investigating which cells are actually responsible for those differences—using techniques like cell sorting and culture dish analysis. And here’s what I found: surprisingly, there are cells that are resistant to what I jokingly call “harassment”—in other words, stress. These “stress-resistant” cells turn out to have the highest potential.
This is fresh data we’re just publishing, but for example: normally, stem cells are cultured in nutrient-rich media. But if you culture them in an extremely nutrient-poor, almost starvation-like condition, only the stem cells with what I call “stress-tolerance genes” survive. And those surviving cells are extraordinarily powerful.
Sean: That’s incredible.
Mabuchi: I was amazed myself. When I talked about this with Takayoshi Takebe, we joked that researchers are the same: only those who are stress-resistant—who can endure the “harassment”—remain, and they end up doing the best work (laughs).
It comes down to Darwin’s theory of evolution. It’s not the strongest who survive, but those who adapt to their environment. Likewise, stem cells that can keep proliferating under extreme stress are the most capable. And I suspect that outstanding scientists—the ones Stellar Science gathers—probably all carry a “stress-resistant gene,” so to speak (laughs).
Sean: That’s fascinating. It makes me curious how much harassment researchers actually endure, though maybe that’s something we shouldn’t ask on record (laughs). Before we go too far in that direction, just to clarify: are you saying that within stem cells, some are stress-resistant and others are not? And the differences between these populations are what your research aims to define more precisely?
Mabuchi: Exactly. We’ve already secured a patent, so I can share this. The difference largely comes down to metabolism. As we age, metabolism declines, which may explain reduced resilience. Young cells can process nutrients and eliminate waste very effectively, so even when stress or harmful signals appear, they can easily clear them away. Older cells, by contrast, don’t cycle as efficiently. As a result, their tolerance weakens—they may die off quickly or enter senescence under stress. This aligns with theories beyond mesenchymal stem cells as well, and my research supports that view.
Sean: I see. And by patenting this, you’re suggesting that in the future we might be able to distinguish between high- and low-metabolism stem cells, and then use that knowledge in drug development or regenerative medicine?
Mabuchi: Exactly. That’s very possible. And it ties into common concerns we hear today—for example, that younger people may be more stress-sensitive, or how to identify the best employees. You could imagine giving a “stress shower”—a small stress test—to see how someone responds, and use that as part of selection.
From the medical side, this technology could be used for therapies. Or perhaps one day there will be a drug that activates those stress-resistant genes. Imagine you’re nervous about a tough discussion with your professor—you take this pill, and suddenly you’re calm and resilient, with your “stress-tolerance power” switched on. That might actually be possible. I may be exaggerating a little, but…
Sean: Not at all—it sounds like a kind of defense you can drink.
Mabuchi: Exactly, like a “drinkable protector.”
Sean: Right.
Mabuchi: Physical protectors are easy—clothes, gear, whatever. But people rarely have psychological protectors. Usually, we rely on words, expressions, gestures. But imagine if a drug could give you that—“I’m fine, I can handle this.” That could become a kind of mental protector.
Sean: Amazing. So not only would it shield you from external stress, but it could also help treat existing internal conditions—diseases or dysfunctions in the body?
Mabuchi: I think so. For example, it’s been observed that the more intelligent a person is, the higher the likelihood of developing mental disorders. At the University of Tokyo, I’ve heard statistics about how many students face such challenges. It’s a human cost of overthinking. It’s difficult to balance deep, critical thinking with a positive outlook. But if we could intentionally create that balance—through science—it could be revolutionary. Perhaps even dangerously so (laughs). But still, it’s a fascinating approach.
Of course, the actual connection between stem cells and mental health is still a long road to explore.
The Possibility of Rejuvenation—and Unexpected Challenges
Sean: So, the stress-resistant cells you’ve been describing—those are mesenchymal stem cells, right? Could all of the body’s stem cells become like that? Or why isn’t it the case that all stem cells naturally have those qualities?
Mabuchi: Well, if you apply my research directly to the body, it essentially points to calorie restriction. Many health-conscious people already practice this. For example, if you go 16 hours without eating, your metabolism activates and your body enters a healthier state. That’s the theory.
My findings support that: if you constantly take in too many nutrients, you’ll gain weight, but if you lower your calorie intake somewhat—without going into complete starvation—and combine that with exercise, your metabolism activates. That shift can make you feel rejuvenated. It’s a way to change the state of your cells throughout your body, not just mesenchymal stem cells.
At the recent ISSCR (International Society for Stem Cell Research) meeting in Hong Kong, there were presentations showing that calorie restriction revitalizes stem cells across the body. So, this is becoming scientifically validated.
But there’s one catch: hair cells. There are findings that hair follicle cells may actually age faster under calorie restriction. So while your overall health improves, your hair condition could worsen.
In other words, it’s not as simple as saying calorie restriction is universally good for every cell type.
Organoids Connecting Food and Health
Sean: I see—it’s like asking, “Would you choose health or beauty?” Fascinating. Now, since mesenchymal stem cells are stress-resistant, we’ve talked about how nutrition balance might strengthen them inside the body. But I also know your research looks at applications outside the body—for example, meat organoids. That’s a really exciting area, and I’d love to hear more about it.
Mabuchi: Absolutely. They’re closely connected. The organoid technique involves clustering cells together so that, instead of a uniform group, you get small clumps with different functions depending on location. That’s what an organoid is. Within one clump, different regions take on different properties.
As you mentioned, the outer cells and the inner cells are in very different environments. Inside, there’s less oxygen and fewer nutrients compared to the outside. Inner cells often die quickly, but researchers are investigating conditions that allow them to survive. In that sense, organoids partially recreate a starvation-like state for a subset of cells.
This technique also links to what you mentioned earlier—meat organoids. Originally, mesenchymal stem cells were studied to repair bone and cartilage, but they can also differentiate into fat. Since mesenchymal stem cells are the progenitors of these tissues, researchers wondered: if you extract stem cells from, say, steak, and culture them to form organoids, could you keep producing meat entirely in the lab? That was the idea behind cultured meat.
Now, startups abroad are very active in this field, and I myself have created meat organoids using mesenchymal stem cells.
Sean: That’s incredible. A year or two ago, it was such a hot topic—people were saying meat production harms the environment, and with the growing global population, how can we supply enough protein? Cultured meat seemed like a possible solution. It was said to grow quickly, opening up all sorts of possibilities. In your own lab experiments, did you ever have that moment of, “Oh wow, this really could work”?
Mabuchi: Plenty of times. But think about it, Sean—if I ask you, “Would you rather eat a steak or cultured meat?” you’d probably say steak, right?
Sean: I don’t know—it depends how delicious you can make cultured meat (laughs).
Mabuchi: Well, people who have tried it say it has no flavor!
Sean: No flavor?
Mabuchi: Exactly. Muscle cells and mesenchymal stem cells on their own don’t generate taste.
Sean: I see, so it’s flavorless.
Mabuchi: Right. So for people to choose cultured meat, there has to be another motivation—like superior nutrition or added value. Think about how people chug protein shakes without even knowing what’s in them, just because they believe it’s good for their bodies. They could just eat meat, but instead they drink protein for efficiency and health benefits.
In my lab, we worked on fat. Fat is necessary for the body, but too much isn’t good. And not all fats are equal—beef fat isn’t as healthy, while fish oils like DHA and EPA are considered beneficial. So, we engineered a kind of “super organoid”—a piece of meat that actually contains fish oil. In other words, a meatball that delivers healthy fats.
For vegans, who don’t eat meat or fish, essential fatty acids are still critical for life. But since they refuse animal sources, they often lack these nutrients. If cultured meat could provide them, it wouldn’t involve killing animals, and it could motivate vegans to eat it. That was our approach: to engineer organoids with new nutritional qualities.
Ideas Born from Balancing “Interesting” and “Useful”
Sean: That’s fascinating. When non-researchers try to imagine what drives research, sometimes it seems like researchers study mesenchymal stem cells simply because they’re interesting and worth understanding. Other times, it looks like they’re driven by social issues—thinking, “Maybe this research could help solve that problem.” In the end, you have both: a desire to deeply understand something, and then the question of how to apply it—whether to solve problems or contribute to society. I wonder about this difference. Maybe you don’t choose one or the other, but how do you see yourself balancing those approaches?
Mabuchi: That’s actually become a very important question nowadays. As you said, one kind of research comes from curiosity—diving deep into what fascinates you. For me, that’s mesenchymal stem cells. I find it fun and exciting. But if you ask, “Who does this really help?”—the answer is mostly patients with injuries. For someone like you, Sean, if you’re not injured, you might think, “Well, MSCs don’t matter to me.”
But with cultured meat, suddenly everyone feels involved. When I presented my work on meat organoids, people were fascinated. I’d start by saying, “I’m originally a mesenchymal stem cell researcher…” but the response was, “That’s fine, we know it can be used in medicine. But tell us about the meat!” (laughs)
So, while research for treating patients is essential, it doesn’t always capture wide attention. Without that attention, it’s hard to secure funding, and without funding, you can’t do research. That’s why the balance you mentioned is so important. Having both—research that directly helps patients, and research that people can broadly relate to as solving future societal challenges—makes it much easier to continue as a researcher today.
Sean: That makes sense. It seems like going back and forth between the two perspectives gives you new insights—so each approach influences the other positively. Do you feel that way?
Mabuchi: Definitely. For me, it started with working on how MSCs differentiate into fat. Then, Takayoshi Takebe made an offhand comment—something like, “If MSCs can make meatballs, you could even design your own marbling!” (laughs) Since he works on liver organoids, he added, “Then we could mass-produce liver, or even create foie gras from goose cells.” That kind of thinking really opened my mind. What used to be limited to patient treatment suddenly expanded into all sorts of new possibilities.
Sean: That’s really interesting. Depending on what problem you’re trying to solve, you look at different aspects of the science. But along the way, you discover new perspectives, and even seemingly unrelated areas of research can positively influence each other.
Mabuchi: Exactly. One thing I forgot to mention earlier—when culturing human stem cells, we usually add FBS (fetal bovine serum) to the media to help them grow. But because those are bovine components, you can’t transplant those cells into humans. So researchers avoid it in medical contexts. But when it comes to cultured meat, well, the end product is beef, so using bovine serum isn’t an issue at all. The whole framework flips completely.
Doing the same basic tasks—isolating and culturing MSCs—feels like a completely different mindset depending on the purpose. It was like a refreshing change of perspective.
“Living with Walls” in a Researcher’s Life
Sean: So, you’ve talked about learning from both approaches—adjusting methods and perspectives. But when it comes to creating something entirely new, whether through a novel line of research or a new technology, challenges and barriers are inevitable. In your recent work, what has been the most difficult obstacle, the wall you’ve found hardest to overcome?
Mabuchi: Research is really a matter of continually overcoming walls. Things I couldn’t do as a student are now easy, thanks to new technology—especially new machines.
For example, when I was a student, I thought: stem cells divide first into two, then four, and so on—but how many people had actually watched and confirmed that carefully? We couldn’t just sit at a microscope all day. But today’s incubators have built-in cameras. They can automatically track when a single cell divides into two, then into four, and log, “Yes, these all came from the same original cell.” So now, even while sleeping, you can check and say, “Oh, these thousand cells actually grew from four stem cells.”
This allows us to record stem cell behavior like a video. Twenty years ago, I considered marking each cell with a needle, or labeling them somehow. Now, machines do it effortlessly. Breakthroughs like this come from new technology.
So when I hit a wall, instead of exhausting myself and giving up, I think it’s okay to pause and reflect. Maybe it’s not possible right now—but in ten years, it could be easy. So I don’t always force it. For me, doing research “loosely” like that is part of the joy.
Sean: That makes sense—waiting for the right timing, watching how technology evolves, and then pulling out the “card” you’ve been holding onto. It’s not just about your research, but aligning with technological progress as well.
Mabuchi: Exactly. Some people talk about “a wall” as if it’s one thing, but for me, there are many, at different stages. I live with these walls. Maybe that connects back to stress resistance. Instead of quitting when faced with a wall, I keep moving with it. Then one day, a new technology arrives, and suddenly I realize, “Oh, now I can overcome this wall.” Or, “If I can get past this one, maybe I can go around behind it too.” Of course, another wall will be waiting. So I live with them—“with walls I abide,” so to speak (laughs). For a researcher, that mindset may be essential.
Sean: That’s really interesting. It’s almost like cultivating resilience—rather than quitting when you hit a barrier, you move along with it, adapting. That feels connected to stress tolerance, not in the sense of enduring harassment, but more like a mental toughness that allows you to persist despite limitations.
Mabuchi: Exactly. “Harassment” sounds negative, but really, it’s about adapting to stress and learning to live with it. Carrying these walls with you makes you more sensitive to new opportunities. If you gave up, you’d simply stop looking. But if you keep those walls in mind, you remain open to new technologies and ready to try them. That heightened sensitivity is actually a great advantage.
Space Medicine: Possibilities Born from Zero Gravity
Sean: Earlier you mentioned the importance of balancing curiosity-driven research with work that addresses social challenges. Looking ahead—say, over the next three to five years—what challenges do you want to tackle? What areas are you aiming for?
Mabuchi: Oh, there are many. But the hottest area right now has to be space. I’m actually working on a project already. Space is full of unknowns, so whatever you do, you’re bound to discover something new.
Sean: Right.
Mabuchi: Currently, Fujita Health University, a company, and a startup are collaborating to send mesenchymal stem cells into space to see what happens when they’re cultured there. How do MSCs behave in microgravity? Conversely, maybe zero gravity allows you to culture cells in three dimensions, from all 360 degrees, much more efficiently. That could enable analyses impossible on Earth. We’re working on this with real excitement.
Sean: That’s amazing. So it’s not just about the possibility of humans living in space someday. Even if you bring the results back to Earth, it could enable treatments that aren’t possible under gravity.
Mabuchi: Exactly. Actually, Sean, this project is preparing to launch you into space one day (laughs).
Sean: Wait—me? I have to go? (laughs)
Mabuchi: Well, think about diseases caused by gravity. For example, as people age, knee problems are common. If you inject MSCs on Earth, the cells are influenced by gravity and may not distribute evenly, sometimes limiting the effect. But imagine a patient taking a one-month space trip—receiving MSC transplants in microgravity. The cells could distribute uniformly, and when they return to Earth, they might say, “I can walk again, it feels so much easier!” That kind of space medicine could help not just knees but many areas where cells don’t spread well on Earth. The possibilities are limitless.
Sean: Incredible. Space medicine sounds groundbreaking.
Mabuchi: Space really is amazing.
Sean: For many people, space feels scary—empty, unknown, unpredictable. But hearing you describe it, it seems like precisely because it’s so different, it could enable medical breakthroughs impossible on Earth. That’s an exciting thought.
Mabuchi: Exactly. There’s actually a whole field called space biology, with its own conferences. People are studying fascinating things—for instance, how cancer develops in space. If tumor growth is slower in microgravity, maybe you could treat it more effectively. Or drug delivery: on Earth, gravity spreads medicine throughout the body, but in space, an injection could stay localized, making it far more potent.
And circling back to our cultured meat discussion—food supply is a huge issue in space. But since space has sunlight, algae can grow rapidly with just light and water. Some researchers are using that principle to engineer meat cells enriched with algal nutrients. Ideas like this suggest we might really be able to sustain life in space.
Sean: That’s fascinating. Next-generation medicine usually makes us think about working within the body. But your perspective suggests that by going to space, whole new possibilities open up. Thank you for sharing that.
That concludes the first part of our episode with Dr. Hiroshi Mabuchi.
What did you think?
In the second half, we’ll dive deeper—exploring the research Dr. Mabuchi finds most fascinating and hearing about his passion for science. Be sure to check out Part 2!
Stellar Lab Radio – exploring world-changing research that nobody knows about yet.
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