Anabolic Effects of Ultrasound as Countermeasures of Simulated Microgravity in In-Vitro and In-Vivo Functional Disuse Models

Microgravity (MG) during space flight has been known to cause adverse effect on bone quality. Data collected from studies done on spaceflights show loss of 1–1.6% bone mineral density (BMD) per space-flight-month[1]. Most BMD has been recorded in load-bearing bones [2]. Some studies has considered using drugs and different growth factors to maintain bone mass in microgravity conditions but it can be too expensive to maintain over longer periods of time besides the systematic effects of such treatments [3]. Considering the effects of microgravity are partially attributed to lack of mechanical force on bone tissue, which alters gene expression, reduction in transcription factors and growth factors. Furthermore, lack of gravity effects cell growth, proliferation, differentiation, cytoskeleton polymerization and cellular morphology [4, 5]. Thus to reverse these adverse effects on bone physiology, it is important to provide cells with mechanical stimulus which can provide essential mechanical signal for cells to counter the effects of microgravity. Ultrasound acoustic vibrations can be readily applied in, in vivo and human studies and has shown anabolic effects on osteopenic bone tissue [6]. Furthermore, ultrasound is a non-invasive and more target specific treatment relative to cyclic strain and vibration. The objective of this study is to see effects of low intensity pulsed ultrasound (LIPUS) on disused bone model and osteogenic activity of osteoblast cells cultures in simulated microgravity. This will help us understand that effects of ultrasound on microgravity and mechanotransduction pathway responsible for anabolic effect on bone cells.