Rethinking the Human Heart
Eileen McNamara ’11 is part of a Stanford collaboration working to create transplantable hearts in the lab
Next Generation Innovation Series
BY JESSICA HALSTEAD
What if a failing heart could be replaced not by a donor, but by one grown and printed in a lab—made from a patient’s own cells, ready when they need it?
That’s the vision behind a groundbreaking project at Stanford University, where Eileen McNamara is helping coordinate one of the most ambitious efforts in modern medicine. As a Research Program Manager for the ARPA-H HEART initiative, Eileen works at the center of a 15-lab collaboration attempting something once confined to science fiction: 3D bioprinting a functional human heart.
The project could fundamentally change the organ transplant landscape as we know it. In the current system, thousands of patients face up to years-long waits for donor organs, and those who receive them face risks of rejection and a lifetime of immunosuppressive drugs.
But if the ARPA-H HEART initiative is successful, a simple skin swab and a few months could be all that’s needed to print an on-demand heart from a patient’s own cells. Wait times would be significantly reduced, and so would the likelihood of post-transplant complications.
It won’t be easy—there’s a reason Eileen calls it a “moonshot goal.” But that hasn’t stopped her and the rest of the Stanford team from pushing forward in hopes of redefining what’s possible in regenerative medicine.
From Plastic Printers to Living Tissue
Traditional 3D printing involves loading plastic filament into a machine that prints objects layer by layer. 3D bioprinting borrows from that concept—but instead of plastic filament, the “ink” is living cells that have been grown in a lab setting.
While promising, the process is rife with challenges. For one, living tissue is shapeless, delicate and subject to gravity. If printed in open air, the tissues would collapse immediately. The solution? Hair gel. (Kind of.) The bio-ink, which Eileen likens to mayonnaise, is printed directly into a substance reminiscent of hair gel, which holds together the tissue in its final form. “That helps to be able to print softer tissues,” she explains.
Another hurdle is vasculature. Without vessels, living tissue dies quickly. But embedding vessels just so in tissue, especially if it’s thick, can be complicated. Add the fact that researchers aren’t working with just one cell type, but 11, and you can see why an effort like this takes immense coordination, resources, and time.
The project is about halfway through its five-year grant. Much progress has been made, with researchers successfully printing full-scale heart models, though without living cells. (That’s the next step.) “It realistically will take several more years to be able to get this into clinical trials with humans,” she says. Before clinical trials can start, more research and development has to happen in order to strengthen the groundwork for the project’s major goal—a 3D-bioprinted heart, printed on-demand in less than an hour.
Eileen’s love of nature and biology was ignited by an SSSAS summer camp, Eco-Adventures.
A Cultivated Journey
The science itself is complex, and so is the structure behind it. The HEART project brings together 15 labs, each focused on different aspects of the heart, from cell production and printing to electrical signaling and valve design. Eileen’s role is to keep all of those moving parts aligned.
Her work involves leading meetings, tracking progress, and reporting updates to ARPA-H, the federal agency funding the project. But perhaps most importantly, she acts as a bridge between disciplines, understanding the intricate details across the program.
“Sometimes there are ways that we can collaborate that don’t really seem apparent at first,” she explains. “So I’m really being that bridge and making sure people are connecting.”
Eileen’s journey to the forefront of regenerative medicine has been propelled by her passion for science. It’s a passion fueled, in part, by her early experiences at SSSAS. She points to Beth Barrow’s Eco-Adventures camp as a catalyst. “That was the start of falling in love with nature and biology,” she says.
Eileen’s interest in science sharpened in courses like AP Chemistry and AP Psychology, where her fascination with the human brain—“what makes us who we are”—grew. At Wake Forest University, she designed her own neurobiology-focused major and then went on to the Uniformed Services University of the Health Sciences in Bethesda, where she earned a Ph.D. in neuroscience. While there, Eileen was part of a team studying how to identify biomarkers indicating traumatic brain injury. The work honed her skills in research and data analysis. “I learned what types of questions to ask and how to figure out what story is being told by the data,” she says.
Those skills served her well in her next career move, one that departed from her work in neuroscience. As she wrapped up her Ph.D., the COVID-19 pandemic was taking hold and food insecurity was rampant across the country. “I was looking for a way to combine my scientific background with the food space,” Eileen says, “and I stumbled upon cultivated meat.”
The cultivated meat sector, within the broader cellular agriculture industry, is doing exactly as you might expect—growing meat from cells in a lab. The practice seeks to reduce the costs and environmental impacts of raising and slaughtering animals. Potential benefits aren’t just environmental; on a mass scale, cellular agriculture can be a solution for food insecurity.
Eileen “hopped around” the cultivated food space for a bit before joining the ARPA-H project at Stanford, which wasn’t a far leap from her previous work in cellular agriculture. Both involve cultivating cells and scaling them up, albeit for different end goals. “The techniques that are being used to build a full-scale organ are similar to the cultivated meat space,” she says. “But here, we’re making a functional organ instead of a tasty food product.”
Eileen and Yoshi
Meg’s Marvels Photography
Eyes on the Future
For Eileen, the potential impact of the work she does with the HEART project extends far beyond heart transplants, calling the project a “game-changer.” The same technologies being developed for organs could also eventually apply to other areas, like lab-grown blood, joints, or tissues. “It opens up a whole new box of regenerative medicine,” she adds.
Reflecting on her own path, Eileen emphasizes that there is no single route into science or innovation. Her suggestion for students wanting to get involved with regenerative medicine is to “be curious and keep an open mind.” Rather than focusing on a rigid career plan, she encourages students to build foundational skills, especially the ability to think critically and ask good questions.
“Learning how to analyze data and think about the questions to ask goes a long way,” she explains. Those skills, she notes, are transferable across fields and can open unexpected doors.
The idea of printing a human heart may still sound futuristic, but at Stanford and across the broader scientific community, it is steadily becoming more real. Challenges remain—in biology, engineering, and scaling. But the foundation is being built layer by layer, and cell by cell.
And at the center of it all are researchers like Eileen, helping turn a once-impossible idea into a tangible goal.