Ask researcher Mariah Hahn what she wants to be known for, and she doesn’t talk about results. “Questions,” she said. Hahn talks about asking the right questions.
That might come as a surprise from a leader in the field of tissue engineering that focuses on whether cell tissues can be “convinced” to grow into a body part or organ.
“Anyone can do research, but the difference between researchers and their quality is really to identify key questions in the field,” she said. “I hope I’m one of those researchers who can identify those key questions, and in the end, people say that I contributed in a major way.”
Hahn, a professor in the department of chemical engineering at Texas A&M, is asking how cells can redo what they did in development. “And that’s a really complex question,” she said.
In her research, Hahn takes cells and places them in microenvironments called scaffolds that induce the cells to grow into a new, working organ. The scaffolds, often made of proteins like elastin or collagen, look almost like balls of yarn with cells enmeshed in them.
“With the scaffolds, we want to give the cells that initial environment to say, ‘OK, you need to make new skin cells.’ And with time, the scaffold will go away, and it will be replaced by new tissue – hopefully new skin that the cells have produced. Give the cells a home to trick them into thinking, ‘OK, I’ve got to make a new tissue,'” she said.
Hahn’s journey toward tissue engineering began when she decided to major in chemical engineering at the University of Texas.
“I got into chemical engineering because I didn’t know what chemical engineering really was,” she said. “All I knew was that I liked chemistry. I liked biology.”
The further she got into her major, however, the more unsure about it she became she said.
“The third year they start taking you to chemical plants,” she said. “They take you to these itty-bitty towns in the middle of nowhere, and some people actually have to work there. And the biggest thing the town has is a gas station that serves also as the grocery store and as the dining facility. I just wasn’t attracted to working in a plant at all.”
Hahn considered medical school and enjoyed the required biology classes she took but realized that it was hard for her to see patients in pain.
“It just didn’t feel like a good fit,” she said. “At the same time, it was a better fit than traditional chemical engineering.”
Toward the end of her undergraduate years, Hahn became interested in tissue engineering after meeting a tissue engineer who worked at the University of Texas.
“I talked more with that professor and found out the opportunities that were in other parts of the country that involved chemical engineering,” Hahn said. “And I thought, ‘I really could do this. This is something I could get excited about because it’s interesting to me. I feel like it’s useful.'”
Hahn received her master’s at Stanford University and her doctorate at Massachusetts Institute of Technology, where she studied tissue engineering under Robert Langer, one of the pioneers of the field and head of the largest biomedical engineering laboratory in the world.
Tissue engineering began about 30 years ago. Scientists worked with patients who needed organ transplants or who had other problems, such as neurological disorders.
Development of tissues is still in the experimental phase. Scientists have had a hard time figuring out which scaffolds the cells best respond to, and the ability to consistently grow a complete organ for use in a patient’s body is still a long way from reality.
Some research in tissue engineering has been conducted using stem cells. Hahn uses mouse embryonic stem cells along with adult cells because the mouse embryonic stem cells tend to be more responsive.
“The reason why embryonic stem cells are important is because those cells haven’t yet lost that ability to form those organs,” Hahn said. “The question with the adult cells is, ‘How can I get you to think you’re younger and have you make what I want?'”
Hahn does not use human embryonic stem cells, a practice that has been extremely controversial because of ethical disagreements about the destruction of human embryos.
Those involved in tissue engineering tend to come from either a medical or scientific background – especially from chemical engineering.
Hahn said many medical doctors approach the field with a trial-and-error mentality in an effort to find faster solutions.
“A lot of tissue engineers are medical doctors who do research on trying to get something to work now because they have patients who have devastating diseases of different organs,” she said. “They want to be able to have a replacement because right now we don’t have enough organ donors to meet the need for organs or the other treatments.”
As a chemical engineer, Hahn approaches tissue engineering with a different perspective than that of other researchers.
“My research is more fundamentally based because I don’t think that [the trial-and-error approach] is going to work in the long term,” she said. “I think that might help a few people, but I don’t think that’s going to lead to long-term success. I think both approaches are needed, though, because we do need some short-term successes.”
Hahn said the field has likely moved forward without enough time spent in the primary stages, something she focuses on in her research.
“I think we need to back it up and try to look more fundamentally,” she said. “I think to do that we need to move outside the body and do a bunch of experiments outside the body growing these vessels in scaffolds, comparing what they do and then try to understand what is giving me the best results and why.”
Hahn collaborates with several Texas A&M professors to conduct research, including Melissa Grunlan, an assistant professor of biomedical engineering. As a polymer chemist, Grunlan uses her knowledge of biomedical properties to help create scaffolds for the tissue-engineering experiments.
“I can define the scaffolds. I can tailor properties,” Grunlan said. “And as a tissue engineer, she knows what to do with those scaffolds. It’s a good collaboration.”
Grunlan said once she creates the scaffolds, she takes them to Hahn’s lab to have cells placed in them. Hahn then grows the cells in scaffolds for six to eight weeks, and afterwards, the cells and scaffolds are analyzed.
“Then we say, ‘OK. This one came off pretty strong. What are the properties of this scaffold? What led to that?'” Grunlan said.
Hahn also works with Elizabeth Cosgriff-Hernandez, an assistant professor of biomedical engineering, in developing scaffolds that can be injected into bone. Cosgriff-Hernandez said the two are working to create a scaffold that is both porous and strong enough to withstand the weight constantly placed on bone.
Langer, who was named one of the 25 most important people in biotechnology in the world by Forbes Magazine and Bio World, lauded Hahn’s research.
“She is doing wonderful work on tissue engineering in general and repair of damaged vocal cords in particular,” Langer said. “We started the field of tissue engineering and are working on everything from stem cell engineering to new biomaterials to creating tissues such as pancreas, spinal cords, heart tissue and others.”
Langer said he expects tissue engineering to advance to the point of being able to consistently produce high quality tissues in the next five years.
One high profile example of trying to develop new tissue was with actress and singer Julie Andrews.
Hahn worked with Langer to help develop vocal cords for Andrews, who had her vocal cords damaged by a surgery to remove nodules on them. However, the project has been unable to help the singer.
“For me, that was a very hard thing because you could see that she hoped that it would fix her, but research is slow,” Hahn said.
For all she’s accomplishing in her field, Hahn said she takes her greatest joy in the legacy she’s leaving with her graduate students.
“Now that some of my students are three and a half years into grad school, I can see how they’ve progressed,” she said. “They’re approaching problems in a much more analytic manner. That’s been really enjoyable to me to be able to see my students progress in that way. It’s been neat to see them look at experiments in different ways and asking the questions they should ask.”
She’s interested in questions.
And yet, it’s not as if she wouldn’t mind finding some answers.
“I want to be able to say that there were people who benefited from what I did, and that I really did something important for this field in terms of translating into helping people,” she said.