A University of North Texas engineering doctoral candidate who’s hoping to shape the future of cardiac research has now earned a prestigious predoctoral fellowship award from the National Institutes of Health (NIH).

“It feels like it’s going to give me a lot more opportunities in the future,” said Marcel El-Mokahal. “Having the security of funding feels really good, too.”

El-Mokahal is also the first doctoral student in the College of Engineering’s biomedical engineering department to earn the NIH F31 fellowship award. The fellowship is for predoctoral students training in health-related areas and will cover three years of his research stipend along with 60% of his tuition.

“This provides an unprecedented training and research opportunity for mentoring Marcel as a next-generation biomedical scientist and engineer in the field of cardiovascular science,” said Assistant Professor Huaxiao Adam Yang, Director of the Cardiovascular Tissue Engineering Lab at the Department of Biomedical Engineering, El-Mokahal’s primary mentor and sponsor for his NIH F31 fellowship. He will also be co-mentored and co-sponsored by Joseph Hill at the University of Texas Southwestern Medical Center on cardiac biology and medicine.

El-Mokahal is researching human cardiac organoids, tiny lab-grown human stem cell-derived heart tissue constructs that mimic the heart structure, function, and cellular composition. Yang specializes in this research, and his lab produces cardiac organoids that feature a blood vessel network, which is crucial to El-Mokahal’s research.

“My research tied to this fellowship focuses on two approaches to achieve cardiac organoid maturation,” El-Mokahal said. “The first is switching the metabolism of the organoids, and the second is stepwise changing the stiffness of the environment engulfing the organoids.”

The organoids grown in the lab resemble a fetal heart, but El-Mokahal wants to mature the organoids so that they accurately reflect an adult heart or certain aspects of it. Outside of his fellowship research, El-Mokahal wants to be able to use the mature organoids to model late-onset cardiac diseases.

“I’m interested in heart medicine because my father had heart complications from malaria, and listening to his doctor explain his condition made me want to become a cardiologist,” El-Mokahal said. “When I came to the U.S., I volunteered at clinics, and I realized I didn’t just want to administer the cure, I wanted to find the cure.”

For his research, El-Mokahal will be using the specialized organoids from Yang’s lab, something he can’t get anywhere else. These organoids survive on glucose, just like fetal hearts, but as hearts mature, they also start to depend on fatty acids. He’ll be finding the proper balance between the two.

“Many labs can make that switch to just fatty acids, which makes the cardiac muscle cells happy. However, our organoids have those blood vessel cells, and other cardiac cells, that still rely on glucose. My research is on finding that sweet spot.”

Keeping those cells helps maintain a more true-to-life organoid heart. For stiffness, El-Mokahal uses a special type of hydrogel that engulfs the organoid as it develops. That special hydrogel is developed through collaboration with Yi Hong at the University of Texas at Arlington Bioengineering.

“We use visible light to stiffen it up to a degree, wait a couple of days, and then use visible light again to further crosslink to stiffen up a bit more. This is something that has never been done before to our knowledge,” El-Mokahal said. “It’s been shown that stiffness has an impact on the maturation of the heart, so we believe this will be very important to model diseases.”

El-Mokahal’s research will take place over the next three years, the length of the fellowship. Once he earns his doctoral degree, he aims to join academia so he can continue his research.

“Maturation of stem cell-derived cardiac muscle cells has been an issue in the past decade. I believe further progress is limited by the lack of cellular diversity in other reported heart models. If we can at least mature our cardiac organoids at the metabolic level so that we can model late-onset cardiometabolic diseases while preserving cellular diversity, then that’s a great achievement.”