Washington: MIT scientists, led by an Indian-origin researcher, have designed a new implantable tissue scaffold that induces the body to rapidly form new bone which looks and behaves just like the original tissue.
The scaffold coated with bone growth factors that are released slowly over a few weeks could offer a dramatic improvement over the current standard for treating bone injuries, which involves transplanting bone from another part of the patient's body.
Patients with severe bone injuries, such as soldiers wounded in battle; people who suffer from congenital bone defects, such as craniomaxillofacial disorders; and patients in need of bone augmentation prior to insertion of dental implants could benefit from the new tissue scaffold, the researchers said.
"It's been a truly challenging medical problem, and we have tried to provide one way to address that problem," said Nisarg Shah, lead author of the study.
Two of the most important bone growth factors are platelet-derived growth factor (PDGF) and bone morphogenetic protein 2 (BMP-2).
As part of the natural wound-healing cascade, PDGF is one of the first factors released immediately following a bone injury, such as a fracture.
The Massachusetts Institute of Technology (MIT) team created a very thin, porous scaffold sheet coated with layers of PDGF and BMP.
Using a technique called layer-by-layer assembly, they first coated the sheet with about 40 layers of BMP-2; on top of that are another 40 layers of PDGF.
This allowed PDGF to be released more quickly, along with a more sustained BMP-2 release, mimicking aspects of natural healing.
The scaffold sheet is about 0.1 millimetre thick; once the growth-factor coatings are applied, scaffolds can be cut from the sheet on demand, and in the appropriate size for implantation into a bone injury or defect.
The researchers tested the scaffold in rats with a skull defect large enough - 8 millimetres in diameter - that it could not heal on its own.
After the scaffold was implanted, growth factors were released at different rates. PDGF, released during the first few days after implantation, helped initiate the wound-healing cascade and mobilise different precursor cells to the site of the wound.
These cells are responsible for forming new tissue, including blood vessels, supportive vascular structures, and bone.
BMP, released more slowly, then induced some of these immature cells to become osteoblasts, which produce bone. When both growth factors were used together, these cells generated a layer of bone, as soon as two weeks after surgery, that was indistinguishable from natural bone in its appearance and mechanical properties, the researchers said.
The research appears in the journal PNAS.