By removing a female mouse's ovary and replacing it with a bioprosthetic ovary, the mouse was able to not only ovulate but also give birth to healthy pups. The moms were even able to nurse their young. The bioprosthetic ovaries are constructed of 3-D printed scaffolds that house immature eggs, and have been successful in boosting hormone production and restoring fertility in mice, which was the ultimate goal of the research.
3-D printing an ovary structure is similar to a child using Lincoln Logs, said Alexandra Rutz, co-lead author of the study and a former biomedical engineering graduate fellow in Shah's Tissue Engineering and Additive Manufacturing (TEAM) lab at the Simpson Querrey Institute. Children can lay the logs at right angles to form structures. Depending on the distance between the logs, the structure changes to build a window or a door, etc.
"3-D printing is done by depositing filaments," said Rutz, who is now a Whitaker International Postdoctoral Scholar at École Des Mines De Saint-Étienne in Gardanne, France. "You can control the distance between those filaments, as well as the advancing angle between layers, and that would give us different pore sizes and different pore geometries."
What sets this research apart from other labs is the architecture of the scaffold and the material, or "ink," the scientists are using, said Ramille Shah, assistant professor of materials science and engineering at McCormick and of surgery at Feinberg.
That material is gelatin, which is a biological hydrogel made from broken-down collagen that is safe to use in humans. The scientists knew that whatever scaffold they created needed to be made of organic materials that were rigid enough to be handled during surgery and porous enough to naturally interact with the mouse's body tissues.
"Most hydrogels are very weak, since they're made up of mostly water, and will often collapse on themselves," Shah said. "But we found a gelatin temperature that allows it to be self-supporting, not collapse, and lead to building multiple layers. No one else has been able to print gelatin with such well-defined and self-supported geometry."
That geometry directly links to whether or not the ovarian follicles, organized hormone-producing support cells surrounding an immature egg cell, will survive in the ovary, which was one of the bigger findings in the study.
"This is the first study that demonstrates that scaffold architecture makes a difference in follicle survival," Shah said. "We wouldn't be able to do that if we didn't use a 3-D printer platform."