Editor’s note: The following article appears in the Spring 2009 department magazine, available for download here.
Faculty Profile
Dr. Mariah Hahn
Engineering a Healthier Future
As much as Mariah Hahn would like to hearken back to that one magical childhood moment during which she decided to embark on a career in science, the assistant professor in Texas A&M University’s Artie McFerrin Department of Chemical Engineering confesses she didn’t have one. In fact, she candidly admits that she wasn’t even very inquisitive as a child.
“I was never one of those kids who asked why the sky was blue; I was just happy knowing it was blue,” Hahn joked.
Oh, how things have changed.
These days Hahn spends her time in a world of questions, asking and attempting to answer some very complex ones.
A bright, young chemical engineer whose focus is on biological processes, specifically cell-material interactions, Hahn is one of the up-and-coming minds in the rapidly advancing field of tissue engineering. She’s recently been named a “Texas Engineering Experiment Station Select Young Faculty” member. And last year Hahn was recognized as a “rising star” by the American Chemical Society, receiving the organization’s “PROGRESS/Dreyfus Lectureship Award” in recognition of her research contributions in the areas of soft tissue engineering.
It’s a field that at one time seemed the stuff of science fiction with its focus on regeneration and growth of man-made, living replacement parts for the human body. Advances in science and medicine throughout the last few decades however have resulted in serious progress in the field, making what once seemed unimaginable now chock-full of potential.
In addition to reducing the number of lives lost due to shortages of transplantable organs, tissue engineering may lead to more effective treatments for burn victims as well as those suffering from injuries and even degenerative or congenital defects.
Hahn focuses on studying regeneration of organs for which mechanical functionality is vital. She’s particularly interested in blood vessels, bone and vocal cords.
Her work with vocal folds began when she was a graduate student at MIT under the guidance of Robert S. Langer, a distinguished and highly regarded researcher in the field.
Prior to that, Hahn had earned her master’s degree in electrical engineering from Stanford University and attended the University of Texas at Austin as an undergraduate where she received her bachelor’s in chemical engineering. The plan back then, said Hahn, was to utilize her electrical engineering background and work with medical imaging technology, such as that used in MRI scans.
But events at MIT took a somewhat fortuitous turn.
In 2001, Langer’s research group was seeking two graduate students to assist in a new vocal cord regeneration project – one who would focus on designing the biomaterials needed for regeneration and another who would focus on developing measures for evaluating biomaterial success, including the use of imaging technology. Ultimately, only one student was hired – Hahn. She was selected however with the expectation that she focus on biomaterials research rather than imaging. She accepted the challenge and began tackling a serious and compelling problem.
Vocal cord disorders have affected millions of people. Damage to the cords can be attributed to scarring from surgical procedures, including intubation, or to lesions caused by excessive talking, yelling, coughing, smoking, and even throat clearing. In worst-case scenarios, vocal cord damage can result in permanent voice dysfunction or loss.
Hahn’s role in the research initiative focused on developing materials that would allow cells in the vocal fold to begin repairing the damage. It is work she continues to expand on as an assistant professor at Texas A&M.
“We want cells to reproduce what is native for that organ,” Hahn explained. “For example, if we are trying to restore damaged bone, we want the material to instruct the cells to produce normal bone. This means that cells should deposit what we call an ‘extracellular matrix,’ and the proteins composing this extracellular matrix should be present in the same amount and organization as in normal bone. It’s not enough just to have the proper ingredients; you also must mix it together properly. Think of making a cake. It’s the amount and how it’s organized spatially.”
Towards that goal of identifying a material that would allow cells to produce vocal cord extracellular matrix, Hahn developed a composite “hydrogel” made of collagen, the major structural protein of the human body, and alginate, a sugar-like substance found in the cell walls of algae. A hydrogel, explains Hahn, is a water-absorbent gel, much like Jell-O, that allows cells to conduct normal physiological processes.
Hahn’s hydrogel maintains its original shape and mass significantly longer than most materials currently used for vocal cord repair while simultaneously allowing cells to synthesize new extracellular matrix. This is significant, since it could potentially avert the need for multiple surgical procedures.
As with lip augmentation, multiple injections are required in vocal cord repair if the injected material does not maintain its original volume for a long enough time. But for the vocal cords, multiple procedures carry a high risk of causing further injury and should be avoided. An additional benefit of Hahn’s material is that its mechanical properties can be readily tailored to the individual patient.
These features potentially mean Hahn’s hydrogel may be an important tool in restoring the normal shape and physiology of the vocal cords over time.
In addition to her continued work with vocal cord restoration, Hahn also is focusing on vascular tissue engineering – trying to effectively recreate small-diameter blood vessels such as coronary arteries. It’s a complex process with progress measured in inches rather than miles, but it’s one for which there is a pressing need.
“A lot of people have coronary artery bypass procedures, and right now there are no good replacements for coronary arteries other than taking tissue from another part of your body,” Hahn said. “About 20 percent of bypass patients have no such suitable tissue. Tissue engineering has the potential to fill this clinical need.
“We understand cells so imperfectly. There is so much to discover about them. How can we get cells to do what we want them to do? Even after 30 years of research into tissue engineering we still can’t replace or regenerate certain aspects of skin, for example. We can’t yet engineer capillary beds.
“There are so many questions, and they’re questions I’m interested in; they’re questions I get excited about.”
