Cortical and Trabecular Bone Microstructure Did Not Recover at Weight-Bearing Skeletal Sites and Progressively Deteriorated at Non-Weight-Bearing Sites During the Year Following International Space Station Missions

Abstract

Risk for premature osteoporosis is a major health concern in astronauts and cosmonauts; the reversibility of the bone lost at the weight-bearing bone sites is not established, although it is suspected to take longer than the mission length. The bone three-dimensional structure and strength that could be uniquely affected by weightlessness is currently unknown. Our objective is to evaluate bone mass, microarchitecture, and strength of weight-bearing and non-weight-bearing bone in 13 cosmonauts before and for 12 months after a 4-month to 6-month sojourn in the International Space Station (ISS). Standard and advanced evaluations of trabecular and cortical parameters were performed using high-resolution peripheral quantitative computed tomography. In particular, cortical analyses involved determination of the largest common volume of each successive individual scan to improve the precision of cortical porosity and density measurements. Bone resorption and formation serum markers, and markers reflecting osteocyte activity or periosteal metabolism (sclerostin, periostin) were evaluated. At the tibia, in addition to decreased bone mineral densities at cortical and trabecular compartments, a 4% decrease in cortical thickness and a 15% increase in cortical porosity were observed at landing. Cortical size and density subsequently recovered and serum periostin changes were associated with cortical recovery during the year after landing. However, tibial cortical porosity or trabecular bone failed to recover, resulting in compromised strength. The radius, preserved at landing, unexpectedly developed postflight fragility, from 3 months post-landing onward, particularly in its cortical structure. Remodeling markers, uncoupled in favor of bone resorption at landing, returned to preflight values within 6 months, then declined farther to lower than preflight values. Our findings highlight the need for specific protective measures not only during, but also after spaceflight, because of continuing uncertainties regarding skeletal recovery long after landing. © 2017 American Society for Bone and Mineral Research.

Prediction of Fractures in Men Using Bone Microarchitectural Parameters Assessed by High-Resolution Peripheral Quantitative Computed Tomography—The Prospective STRAMBO Study

“…A cross‐sectional analysis may be influenced by bone loss developing after fracture due to low physical activity. In experimental and clinical studies, unloading (hindlimb suspension) and weightlessness result in a similar bone loss in cortical and trabecular compartments . The strong fracture prediction by Tb.N in both sexes is not explained by different age‐related bone loss in these compartments either.…”

Effects of Long-Duration Spaceflight on Vertebral Strength and Risk of Spine Fracture

“…It may be that in‐flight exercise loads the spine relatively more than the hip. Of note, at both skeletal sites, there is tremendous heterogeneity in the rates of bone loss, as noted . The sources of this heterogeneity are not well understood, but demand further attention to identify which crewmembers may benefit most from pharmacologic therapy to maintain skeletal health.…”

“…(3) One approach that overcomes the limitations of DXA-BMD measurements involves the use of three-dimensional (3D) computed tomography (CT) scans, that can be used to measure bone density, geometry, and strength via finite element analysis. (4)(5)(6)(7) A few studies have demonstrated the utility of CT scans for assessing the impact of spaceflight on skeletal health, (8)(9)(10)(11)(12) reporting that hip strength, assessed by CT-based finite element analysis (CT-FEA), declines at approximately twice the rate as hip DXA-BMD. (8) Moreover, there was no correlation between the femoral strength declines and hip DXA-BMD declines, (8) highlighting that DXA-BMD may not be a sufficient surrogate for spaceflight-induced changes in bone strength.…”

“…After return to Earth, bone recovery is variable and can take years to approach preflight values. (10)(11)(12)14) In particular, there is minimal total volumetric BMD (vBMD) recovery in the tibia (12) and femoral neck (10) after 1 year of Earth recovery, whereas total vBMD of the lumbar spine shows nearly complete recovery in the same timeframe. (11) When considering fracture risk, it is important to consider not only bone strength, but also the load that the bone must support.…”

Periostin function in communication with extracellular matrices

“…Although there was a beneficial effect on airflow obstruction in all the patients treated with lebrikizumab, the effect was greater in patients who had circulating levels of periostin, indicating that periostin is a good biomarker for determining candidates for lebrikizumab treatment (Zhu et al 2017). With regards to mechanical stress, under microgravity, periostin can be utilized as a marker of periosteal metabolism because of the fact that periostin concentration in serum increased transiently along with 15% increase in cortical porosity, which indicates that periostin is a good marker of cortical porosity (Vico et al 2017).…”