The purpose of this study is to understand bone loss and sustained bone loss after prolonged spaceflight using state-of-the-art 3D imaging methods (high resolution peripheral computed tomography, HR-pQCT) in combination with novel image analysis techniques. Bone health has been the subject of many space flight studies in the past but new 3D methods enable the adaptation of bone to spaceflight to be monitored at a much smaller scale than previously. HR-pQCT allows the clinical measurement of human 3D bone architecture at sufficient resolution to assess morphological parameters at a trabecular level. Past studies have demonstrated its precision, good correlations with various gold standard methodologies to quantify bone architecture, its modest but significant correlation of bone architecture and mechanical strength with other sites in the body and, when combined with finite element analysis (FEA), its strong ability to predict bone strength. The use of 3D image registration, developed at the University of Calgary, has been shown to improve the sensitivity of longitudinal studies for detecting bone loss and allows the tracking of individual trabeculae over time. Specific objectives include:
(1) To investigate bone loss patterns in subjects exposed to microgravity. This shall be accomplished by using new non-invasive longitudinal three-dimensional measures of high-resolution peripheral quantitative computed tomography (HR-pQCT) of bone structure in addition to standard analysis techniques of DXA and analysis of biomarkers for bone formation and resorption.
(2) To determine parameters that may identify individuals with heightened sensitivity to sustained bone loss / loss of bone strength using the micro-structural parameter outcomes such as bone volume ratio and trabecular thickness, and magnitude and rate of bone loss.
APPROACH:
Three types of data collection are planned for both preflight and postflight data collection: Blood and 48 hour urine samples, DXA scans of the whole body, hip, spine, wrist and calcaneus (heel), and HR-pQCT scans of all four limbs (left and right distal tibia and left and right distal radius).
There will be a 10.2 ml blood draw and a 48hour void-by-void urine collection. Bone biomarkers shall be quantified from the samples. Collection days are Launch minus 180 days (L-180d), L-60d ± 30d, Return to earth plus 180 days (R+180d), and R+360d. Where possible, data will be shared to TBone from either MedB Clinical Nutrition Assessment or HRP Biochemical Profile experiment. In the event that neither protocol is otherwise planned for a particular subject at the required time point, data collection specifically for TBone will be accomplished according to the HRP Biochemical Profile protocol.
DXA scans include a whole body scan and regional scans of both proximal femurs (hips), spine, calcaneus (heel), and wrist. The technician positions the crewmember for each scan. The scan data are stored as digital information on the densitometer’s computer; analysis is performed later by the technician and a summary report generated. DXA scans planned for L-360d to L-45d preflight and (R+12d ± 9d) and R+360d ± 15d postflight are expected to be shared to TBone from MedB11.1 Medical Assessment Test. DXA scans at R+180d ± 15d and R+360d ± 15d are specifically required for this experiment and will be performed using the MedB11.1 Medical Assessment Test protocol.
At each HR-pQCT scanning session, left and right distal radius as well as left and right distal tibia will be scanned. High-resolution CT images will be created from these scans from which bone micro-architecture can be quantified. The subject will complete a health history questionnaire that details a brief medical history, medications, and supplements in addition to a few vital statistics necessary for data analysis. Questions shall focus on bone health. One pre-flight HR-pQCT will be performed at L-80d ± 20d. Postflight, HR-pQCT scans are planned for R+12d ± 9d, R+180d ± 15d and R+360d ± 15d.
There are no specific in-flight operations required for this experiment. Data on in-flight blood and urine biomarkers will be obtained through data sharing. If the HRP Biochemical Profile is not part of the subject’s complement, only pre and post-flight data is required. Inflight food intake and exercise data will also be obtained through MedB Clinical Nutrition.
RESULTS:
Results for this investigation are unavailable. This is an international experiment. NASA does not currently have an agreement with international space partners to archive their data in the LSDA.