How do you do it? Running? Boxing? Jane Fonda work out videos? Whatever the method, we all need exercise to keep our bodies and minds healthy and functional, and it now turns out that stem cells benefit from exercise too! Researchers have demonstrated that remote mechanical stimulation of transplanted mesenchymal stem cells (MSCs) is a potentially useful therapeutic option to treat bone-related disorders, which currently relies on painful and invasive bone grafts.
The group of Alicia J. El Haj knew that exercising, or mechanically stimulating, MSCs improved their bone forming (osteogenic) capabilities after transplantation, but lacked an effective method to non-invasively stimulate injected MSCs. In a new study, they investigated the use of targeted magnetic nanoparticles to transmit mechanical forces to MSCs and boost bone formation capacity.
In order to do this, the group coated magnetic nanoparticles with antibodies that target specific receptors on MSCs, which, when stimulated with an oscillating electromagnetic field, pass an external force to the cell interior. They used MSCs coated with these antibody laden nanoparticles in two model systems: an organotypic culture model (ex vivo developing chick fetal femur) and a tissue-engineered collagen hydrogel. This resulted in a boost in bone formation and density by over 30% when remotely stimulated through incubation in the presence of the magnetic field.
Encouragingly, this treatment did not lead to harmful mechanical stress, which may reduce effectiveness, and addition of bone morphogenetic protein 2 (BMP2)-releasing polymer microspheres further boosted bone growth by providing an additional growth stimulus. Importantly, the boost in bone formation was lost when the researchers switched off the magnetic field, demonstrating that unstimulated MSCs lacked functionality.
Controlled mechanotransduction represents an exciting advance, and could be immediately clinically applicable. Nanoparticles have existing regulatory approval as magnetic resonance imaging contrast agents, and the promise of further refinements and improvements to this treatment makes their potential as injectable therapies for regenerative medicine plain to see.
So get those fingers warmed up, and click the link to “bone-up” on this stimulating study (Henstock et al, Stem Cells Transl Med, 2014).