For children born with microtia, a congenital deformity of the external ear, reconstructive surgery solutions can involve long, painful operations or prosthetics that rarely resemble the real thing.
However, Cornell bioengineers and physicians have offered new hope by using 3-D printing and injectable gel molds to create an artificial ear that looks, feels and functions like a natural one.
Dr. Jason Spector, director of the Laboratory for Bioregenerative Medicine and Surgery and associate professor of plastic surgery at Weill Cornell Medical College, said this method is "absolutely" the best option reconstructive surgeons have for helping kids with microtia or those who've lost part of an ear to trauma or cancer.
“This approach really combines the cutting edge of imaging, simple biology and our bioengineering know-how," Spector told Discovery News. "What it does, essentially, is create an exact replica of the patient’s contralateral ear.”
Along with Dr. Lawrence Bonassar, associate professor of biomedical engineering at Cornell, Spector co-authored a study published in PLOS ONE detailing their innovative methods, which vastly improve on the two previous options for treatment -- the first being the creation of an implant using an artificial, Styrofoam-like material.
"There’s a big problem with these implants actually extruding through the skin after they’re implanted," Bonassar said. "That can be dangerous and painful.”
The second option involves harvesting rib cartilage from the patient and carving it into the shape of ear, which Spector says requires two long and painful surgeries.
To create these new, bioengineered ears, Spector and colleagues began by making a digital 3-D image of a human's ear. Next, they converted that image into a solid ear using a 3-D printer to make a mold, into which they injected a high-density gel that acts as a scaffold upon which cartilage can grow.
"The reason why cartilage tissue engineering lends itself to this type of approach is that cartilage is unique -- it doesn’t require an immediate blood supply to survive,” Spector said. "The use of our special collagen hydro-gel allows the cells to not only survive, but thrive, and lay down a cartilaginous matrix.”
Another added bonus: the process is fast. Bonassar says it takes half a day to design the mold, a day or so to print and a half hour to inject the hydro-gel. The ear can be removed 15 minutes later where it's then left in a nourishing cell culture for several days before being implanted.
While this study only used cartilage cells from bovine sources, Spector says they are testing ways to expand the pool of cartilage cells by putting them in different environments.
"One of the really promising things we’re doing is mixing them with stem cells that are derived from bone marrow,” he added. "You could imagine doing this on a child – taking the cartilage remnant from the microtic ear, taking a small graft from the contralateral side and then taking a little bone marrow. It all can be done rapidly in 20 to 30 minutes, rather than the five to six hour rib harvest."
Spector added the best time to implant a bioengineered ear would be when a child was 5 or 6 years old -- when the head and ears are almost 80 percent of adult size. That way, even if it didn't grow to it's full potential, the ear would still look proportionately similar.
But before this procedure is tried on human subjects, more efficacy tests must be conducted.
“Optimistically, it would be four or five years before we see this going to widespread clinical trials," Bonassar said.