Gravitational Regulation of Osteoblast Genomics and Metabolism (NIH-Osteo) - 09.30.14
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Millions of Americans experience bone loss, which results from disease or the reduced effects of gravity that can occur in bed-ridden patients. New ground-based studies are using magnetic levitation equipment to simulate these gravity-related changes. Gravitational Regulation of Osteoblast Genomics and Metabolism (NIH-Osteo) tests whether magnetic levitation accurately simulates the free-fall conditions of microgravity by comparing genetic expression in osteoclast and osteoblast cells, which are different types of bone cells. This information helps scientists determine the molecular changes that take place in magnetic levitation and real microgravity.
Science Results for Everyone
BioServe Space Technologies, University of Colorado, Boulder, CO, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
National Laboratory - National Institutes of Health (NL-NIH)
Scientific Discovery, Earth Benefits
ISS Expedition Duration
March 2015 - October 2015
Previous ISS Missions
- Approximately 18 million Americans experience osteopenia, which is a disease that reduces bone mass because of an imbalance in bone remodeling. In healthy bones, formation of bone and dissolution of bone are equal. This balance occurs as a result of physical cues from the environment, such as stress and strain on the cell level, which activates signaling pathways among bone cells to create a biochemical response.
- Reducing gravitational loading to skeletal tissues accelerates bone loss and fracture. This is evident in bed-ridden patients and astronauts in orbital free fall. Microgravity provides an accelerated model for bone loss and presents the researcher with a unique tool to study the mechanisms behind this loss via the study of signaling pathways and gene and protein expression.
Studying bone physiology in a levitation magnet provides a new ground-based environment to study bone loss mechanisms. Gravitational Regulation of Osteoblast Genomics and Metabolism (NIH-Osteo) tests the hypothesis that ground-based magnetic levitation simulates orbital free fall by comparing osteoblast and osteoclast genomics, signaling pathways proteomics and metabolomics in both environments. Increased understanding of the mechanisms of rapid bone loss associated with orbital free fall allows the extension of this knowledge to an understanding of the mechanisms of osteoporosis of other etiologies on Earth.
The skeletal system is a dynamic organ that affects human health on many levels. Chemical messengers released from bone tissue have an impact on obesity, diabetes, kidney function and bone integrity. Bone is in dynamic equilibrium between bone matrix resorption, via osteoclastic (bone consumption) activity, and bone matrix synthesis via osteoblastic (bone building) activity. When the equilibrium is no longer in balance, bones can demineralize, become fragile, and fracture. This is clinically referred to as osteopenia with progression toward osteoporosis. Conversely, when bone matrix production exceeds bone resorption, the outcome is bone malformation and compromised structural stability, i.e., Paget’s disease. The key to proper bone homeostasis is cellular communication and control via cytokines, growth factors and hormones.
Bone biology research during the past two decades resulted in the discovery of signaling pathways and gene expression that correlate with osteopenia. This led to the development of pharmaceutical compounds to mitigate the cause and symptoms of bone loss. For example, bisphosphonates can initiate apoptosis in osteoclasts, and acts as an antiresorptive agent resulting in less breakdown of bone. Another antiresorptive compound is an osteoprotegerin analog, e.g., Denosumab, which blocks the binding of RANKL to RANK on osteoclasts, thus preventing osteoclasts from dissolving bone. A bone anabolic agent, e.g., Teriparatide, mimics parathyroid hormone and stimulates osteoblasts to create bone matrix.
Older individuals are at risk for significant loss of bone integrity and subsequent fracture associated with a loss of mobility / bed rest, menopause, and pathology at a rate of loss around 1 – 3.5% per year (Hansen 1991). The loss of bone mass and integrity with exposure to the microgravity environment of orbital spaceflight is roughly 1 – 3% per month during space flight for weight bearing bones (Tilton 1980). The reason for accelerated bone loss in space is controversial and may be due to increased osteoclast activity and/or decreased osteoblast activity and/or a derangement in osteocyte signaling, or a combination of all. Enhanced bone loss in microgravity provides a more sensitive environment for testing therapeutic regimes to discover molecular targets and mechanisms. Increased understanding of the mechanisms of amplified bone loss associated with orbital space flight allows the extension of this knowledge to an understanding of the mechanisms of osteoporosis of other etiologies on earth.
Gravitational Regulation of Osteoblast Genomics and Metabolism (NIH-Osteo) aims to validate if magnetic levitation is a reasonable simulation of orbital free fall by measuring biological endpoints, such as signaling pathways and gene expression in osteoblast and osteoclast cells. Cells are exposed to a microgravity environment and ground based cells are exposed to magnetic levitation. All cells are preserved or fixed for analysis after a certain time point. If the validation is successful, then ground-based magnetic levitation will be an important ground-based tool to investigate the effect of gravitational force on biological systems.
Crewmembers experience bone loss in orbit, stemming from the lack of gravity acting on their bones. NIH-Osteo investigates the molecular mechanisms that dictate this bone loss by examining osteoblasts, which form bone, and osteoclasts, which dissolves bone. Improved understanding of these mechanisms could lead to more effective countermeasures to prevent bone loss during space missions.
Understanding the cellular mechanisms of bone loss associated with microgravity helps researchers understand the mechanisms of bone loss in a wide range of disorders. This leads to better preventative care or therapeutic treatments for people suffering bone loss as a result of bone diseases like osteopenia and osteoporosis, or for patients on prolonged bed rest.
The Experiment must be transported to the ISS in -80°C. The experiment requires thermal control of 37°C while active on board the ISS and inside of CGBA. The experiment occurs over a 30 day time period with automated media exchanges over several days and sampling and preservation and fixation of samples at three different time points during the 30 day period. The samples must be stored once preserved or fixed at -80°C or 4°C until they are returned to Earth.
Hardware with cells ascends to ISS in -80°C. Once the experiment reaches the ISS the crew transfers the experiment from the launch vehicle to CGBA on board the ISS. CGBAs temperature is set to 37°C. Over the next 30 days, sampling, preservation or fixation time points that could possibly require crew interaction occur - approximately, at 6, 10 and 30 days. Crew manipulation of the experiment may require a disposable glove bag. Once cells are sampled, preserved or fixed, the cells within the associated hardware are stowed at -80°C and 4°C. The hardware with the preserved/fixed cells remains at the correct stowage temperature until they are returned to Earth.
Osteoblast and osteoclast cells are levitated in a magnetic field for 48 hours, then fixed and stained to examine the actin cytoskeleton for Gravitational Regulation of Osteoblast Genomics and Metabolism (NIH-Osteo). Confocal microscopy of MC3T3 osteoblast stained for actin (red, rhodamine phalloidin), focal adhesions (green, anti-vinculin) and DNA (blue, DAPI). Image courtesy of Bruce Hammer.
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Osteoblast and osteoclast cells are levitated in a magnetic field for 48 hours, then fixed and stained to examine the actin cytoskeleton for Gravitational Regulation of Osteoblast Genomics and Metabolism (NIH-Osteo). Confocal microscopy of primary monocytes/macrophages isolated from mouse long-bone marrow and cultured in the presence of M-CSF for 5 days, followed by 3 days in the presence of RANKL to promote differentiation. Image courtesy of Bruce Hammer.
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Gravitational Regulation of Osteoblast Genomics and Metabolism (NIH-Osteo) used the 17 Tesla magnet to stimulate microgravity. Osteoblast cells are loaded into a bioreactor and placed in the magnet bore where the magnetic force counterbalances the gravitational force, resulting in a simulated microgravity environment. Image courtesy of Bruce Hammer.
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