In vitro effects of nanoparticles on bone remodelling in microgravity

Exposure to microgravity has been associated with several physiological changes in astronauts, including an osteoporosis-like loss in bone mass. Osteoporosis is a disease of bones which leads to a high risk of fracture and other problems, mainly due to the reduction of the bone mineral density. The lack of weight-bearing forces makes microgravity an ideal physical stimulus to assess bone cell responses. In this study, we aimed to determine the effect of nanoparticles (NPs) as a countermeasure to microgravity-induced osteoporosis on bone cells using a nanotechnology approach. To this end, NPs made of hydroxyapatite (HA-NPs) and HA-NPs doped with Strontium (Sr-HA-NPs) were produced and finely characterized by different techniques such as induced coupled plasma (ICP), X-Ray Diffraction (XRD), N2 sorption, Scanning Electron Microscopy (SEM) and Trasmission Electron Microscopy (TEM) analysis. Both types of NPs were then incubated in a dose- and time-dependence manner with human mesenchymal stem cells on earth and in simulated microgravity. Finally, the experiment was launched on the International Space Station (ISS) with the rocket SpX-6, on April 14, 2015. The in vitro cell experiment was perfomed and completed on the ISS by the ESA Astronaut and the italian Military Airforce, Samantha Cristoforetti (NATO project of the Futura Mission). The preliminary results are quite interesting and seem to show the powerfulness of the NPs as a valid countermeasure to microgravity disease. Further in vitro and in vivo experiments need to be performed to validate the developped nanonystems.