Researchers at the Medical University of South Carolina, led by Xuejun Wen, professor of bioengineering and regenerative medicine at Clemson University and the Medical University of South Carolina, tried to closely mimic the natural architecture of the disc, so that it can perform the same functions as the original.
First, they modeled the complex inner structure of the disc on a computer. Then they extruded dissolved polyurethane through a fine glass micropipette tip onto a platform kept at -4 degrees Celsius. The cool temperature of the base caused each printed layer to solidify quickly and allowed successive layers to stack on and maintain their shape. “If you don’t cool it really quickly, you won’t get the structure you want,” says Wen. Finally, the group seeded bovine cells on the scaffold, to test if the structure supported cell growth. These grew to fill it over 19 days, after which the cells were found to have arranged themselves as they would in a natural disc.
“It’s a clever application of additive manufacturing and an exciting piece of work,” says James Iatridis, professor of orthopedics and neurosurgery at the Mount Sinai School of Medicine, in New York. But Iatridis adds that “several alternate approaches involving biological repair are nearing clinical trials or at more advanced stages of development.”
While the new work by Wen and his group comes closest to replicating the microstructure of a real disc, its performance has yet to be tested. In the next few months, the discs will be tested in rats. “We’re still trying to understand how complicated our engineered solutions need to be in order to restore function,” says Mauck.