Metabolic Response of Osteoblast-Like and Osteocyte-Like Cells to Extracorporeal Shock Waves (ESW)

Abstract

Osteoporosis is a disease that has a profound impact on the aging individual in which bone mass is lost (World Health Organization). Similar to osteoporotic patients, astronauts experience permanent bone loss while living without the effects of gravity (Morey and Baylink, 1978). Extracorporeal shock waves (ESW) are applied routinely to break up kidney stones (Pettersson and Tiselius, 1988), and have recently been implemented by our group to produce controlled microdamage in bone as a countermeasure for loss of bone on Earth and in space. In the current study, cell viability, cytoskeletalmorphology, and cellular metabolism were evaluated in osteoblastic and osteocytic cells exposed to ESW in order to understand cellular mechanisms of shock wave therapy in bone. The cells were exposed to two different treatment regimes of specific peak energy levels (43 - 100 MPa) and energy densities (0.46 mJ/mm2 - 1.06 mJ/mm2), respectively, and for 500 cycles. Following ESW treatment, cell viability, cytoskeletal morphology, and cellular metabolism were evaluated. Based on this study, in conjunction with our research on ESW inducing microfractures, it appears that ESW is a promising treatment for maintenance and restoration of bone density in orthopaedic diseases and disuse on Earth and in space. Our current working hypothesis is that, at non-lethal or traumatic levels, stress through shock waves enhances cellular metabolism, alters cytoskeletal conformation, and increases cellular signaling providing a potential cellular level mechanism for tissue adaptation.