This story is part of a series on the current progression in Regenerative Medicine. This piece discusses the regeneration of the skeletal system.
In 1999, I defined regenerative medicine as the collection of interventions that restore to normal function tissues and organs that have been damaged by disease, injured by trauma, or worn by time. I include a full spectrum of chemical, gene, and protein-based medicines, cell-based therapies, and biomechanical interventions that achieve that goal.
New artificial implant scaffolding methods may be the next great leap in bone healing medicine. Osteoporosis affects 10 million Americans, while an even greater 44 million more Americans struggle with low bone density. Degenerative bone conditions lead to increased risk for fractures, limited mobility, chronic pain, and lower life expectancy.
In recent years, bone grafting has been refined as a suitable regenerative method for poor bone health. Bone grafting is the replacement of human bone with artificial bone. Once made of metal or ceramic, artificial bone has progressed to advanced compounds such as hydroxyapatite that mimic the rigidity yet elasticity of human bone.
However, hydroxyapatite and similar compounds have notable drawbacks. They lack significant mechanical strength, meaning the patient would need to be conscious of load bearing on the grafted bones, and they interfere with natural bone healing, which could present issues later on for the patient.
Dr. Mozhgan Keshavarz and colleagues at Tarbiat Modares University in Tehran investigated new methods to circumvent the unfortunate drawbacks of existing bone grafting compounds. Here I analyze their findings and how they may affect the future of bone graft regenerative medicine.
As Keshavarz points out, regenerative bone methods to this point have mostly involved mimicking bone structures and pasting the material to the bone, akin to a skeletal bandaid. The researchers take bone grafting in another direction, using stem cell growth to catalyze bone regeneration and healing.
To do this, they isolated alginate from seaweed and modified it with calcium atoms to create an alginate hydrogel for its softness, biocompatibility, biodegradability, and low immune response. They then combined this material with exfoliated clay nanoparticles for dexterity. The resulting combination is nanosilicate-alginate. This compound, when combined with bone-marrow-derived stem cells, yields osteoblasts that work to regrow bone tissue.
The nanosilicate-alginate represents the soft inner tissue of the bone. For the hard outer bone, Keshavarz and colleagues implemented bioglass: a ceramic material with both crystalline and glassy phases that bonds strongly with existing bone tissue.
FIGURE 1: Development of biomimetic scaffolds containing the various steps for preparing a combinatorial hydrogel/scaffold.
In essence, the bioglass scaffolding would be implanted into degenerated bone filled with the nanosilicate-alginate. The stem cells would then recognize the material and use it to build authentic bone around the bioglass scaffolding, reincorporating it into the larger bone group.
The researchers tested the process with in vivo rat models, finding that impacted areas with bone regression regained 83.66% of previous bone volume after only eight weeks. Such bone healing is rarely seen in cases of osteoporosis and could be a game changer in regard to regenerative bone healing in the years to come.
While the results here are promising, we must note that bioglass, while slightly stronger than hydroxyapatite, remains relatively limited in terms of mechanical strength compared to the healthy human bone comprised of calcium and other materials. Natural bone will grow around the bioglass over time, improving its capped mechanical load, but patients should continue to exercise caution with activity involving affected bones.
Ultimately, though, the bioglass nanosilicate method of bone regeneration is more than exciting. I cannot wait to see how and how quickly this method is implemented on a global scale in the coming years.
To read more of this series, please visit www.williamhaseltine.com