New hydrogels show promise in treating bone defects
Bioengineers and dentists at UCLA's Faculty of Dentistry have developed a new hydrogel that is more porous and effective in promoting tissue repair and regeneration than the hydrogels currently available. Once injected into a mouse model, the new hydrogel induces the migration of naturally occurring stem cells to promote bone healing. Current experimental applications using hydrogels and stem cells introduced into the body or expensive biological agents can have negative side effects.
The results, published online in the journal Nature Communications, suggest that in the near future, the next generation of hydrogel systems could greatly improve current biomaterial-based treatments for bone defect repair.
Hydrogels are biomaterials made up of a three-dimensional network of polymer chains. Because of the network's ability to absorb water and its structural similarities with living tissues, it can be used to transport cells to defective areas to regenerate lost tissues. However, the small pore size of hydrogels limits the survival of transplanted cells, their expansion and the formation of new tissues, which is not ideal for tissue regeneration.
One of the materials that has spread in the field of biomaterials is clay, a mineral of natural origin. Clay has become an ideal additive for medical products without reported adverse effects. It has been shown to be biocompatible and readily available.
The clay is structured in layers, the surface having a negative charge. The layered structure and unique charge were important to the researchers because their hydrogels had a positive or opposite charge. When the hydrogel was inserted into the clay layers, through a process called intercalation chemistry, the final result was an improved clay hydrogel with a much more porous structure that could better facilitate bone formation.
Once they had their improved clay hydrogel, the researchers used a process called photo-induction, or the introduction of light, to transform their new biomaterial into a gel, which would facilitate its injection into their mouse model.
The mouse model had a non-healing cranial defect that the researchers injected with their improved clay hydrogel. After six weeks, they found that the model showed significant bone healing due to the natural migration and growth of stem cells.
"This research will help us develop the next generation of high-porosity hydrogel systems and could greatly improve current bone graft materials," said lead author Min Lee, professor of biomaterial science at the UCLA School of Dentistry and member of the Jonsson Comprehensive Cancer Center. "Our nanocomposite hydrogel system will be useful for many applications, including therapeutic administration, cell support and tissue engineering."
Injectable combinations of living cells and bioactive molecules using hydrogels would be a preferred medical application to treat unhealthy or damaged areas of the body rather than more invasive surgery.
Further research is planned to discover how the physical properties of nanocomposite hydrogels affect cell migration and function, as well as blood vessel formation.
The other authors of the study are Zhong-Kai Cui, Assistant Professor of Cell Biology at Southern Medical University in China, and Drs. Benjamin Wu, Tara Aghaloo, Jessalyn Baljon and Soyon Kim, all from UCLA.
The study was funded by the National Institute of Dental and Craniofacial Research, the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the US Department of Defense and MTF Biologics. The authors have no conflicting interests.
