Writing about their advancement in the Proceedings of the National Academy of Sciences, the researchers have revealed that the artificial bones display a gradual change from bone to softer tissue rather than the sudden shift of previously developed artificial tissue, providing better integration with the body and allowing them to handle weight more successfully.
"One of the biggest challenges in regenerative medicine is to have a graded continuous interface, because anatomically that's how the majority of tissues appear and there are studies that strongly suggest that the graded interface provides better integration and load transfer," said Andres Garcia, professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology.
The researchers were not only able to create artificial bone that melds into softer tissues, but also to implant the technology in vivo for several weeks.
They created the tissue by coating a three-dimensional polymer scaffold with a gene delivery vehicle that encodes a transcription factor known as Runx2.
The team generated a high concentration of Runx2 at one end of the scaffold, and decreased that amount until they ended up with no transcription factor on the other end, resulting in a precisely controlled spatial gradient of Runx2.
Thereafter, the researchers seeded skin fibroblasts uniformly onto the scaffold.
The researchers said that the skin cells on the parts of the scaffold containing a high concentration of Runx2 turned into bone, while those on the scaffold end with no Runx2 turned into soft tissue.
This resulted in an artificial bone that gradually turned into soft tissue, such as tendons or ligaments, the researchers added.
According to them, if the technology passes further testing, it should find an application in anterior cruciate ligament (ACL) surgery that often fails at the point where the ligament meets the bone.
The researchers believe that an artificial bone or ligament made by such types of graded transitions might lead to more successful outcomes for patients.
"Every organ in our body is made up of complex, heterogeneous structures, so the ability to engineer tissues that more closely mimic these natural architectures is a critical challenge for the next wave of tissue engineering," said Phillips, who is now working at Emory University as a postdoctoral research fellow in developmental biology.
The researchers say that their next step is to see whether the tissue can handle weight for an even longer period of time.