Bone health in spacefaring rodents and primates: systematic review and meta-analysis

Abstract

Animals in space exploration studies serve both as a model for human physiology and as a means to understand the physiological effects of microgravity. To quantify the microgravity-induced changes to bone health in animals, we systematically searched Medline, Embase, Web of Science, BIOSIS, and NASA Technical reports. We selected 40 papers focusing on the bone health of 95 rats, 61 mice, and 9 rhesus monkeys from 22 space missions. The percentage difference from ground control in rodents was –24.1% [Confidence interval: −43.4, −4.9] for trabecular bone volume fraction and –5.9% [−8.0, −3.8] for the cortical area. In primates, trabecular bone volume fraction was lower by –25.2% [−35.6, −14.7] in spaceflight animals compared to GC. Bone formation indices in rodent trabecular and cortical bone were significantly lower in microgravity. In contrast, osteoclast numbers were not affected in rats and were variably affected in mice. Thus, microgravity induces bone deficits in rodents and primates likely through the suppression of bone formation.

Bone strength and composition in spacefaring rodents: systematic review and meta-analysis

“…The systematic searches were performed on Medline, Embase, PubMed, BIOSIS Previews, and Web of Science using the search strategy reported in Fu, Goldsmith et al 13 . Additionally, 9 articles were identified from other sources including the NASA Technical Reporting Service and articles referenced in the compendium of NASA’s animal and cell spaceflight experiments compiled by Ronca et al 12 .…”

“…Following title and abstract screening, 1159 were determined to be concerning animals sent to space. Previously, we identified that a majority of bone health-focused animal studies reported findings in mice, rats and primates (348 articles) 13 . In this study, we performed the full text screening of the these articles and identified 54 articles 14 – 66 that contained quantitative measures of bone strength, bone mineral density (BMD) and composition (included parameters are presented in Table 1 and Supplementary Table 2 ).…”

“…Comparing the change in BMD to the changes in bone strength support the notion that changes to BMD alone may not explain the changes to bone strength 9 , 11 . We previously reported that in SF animals cortical bone area decreased significantly by −5.9% [−8.0, −3.8] and cortical thickness decreased by −4.7% [−13.7,4.4] while there was no significant change to marrow area 13 . Thus, cortical bone mass decreased during spaceflight with no increase in total cross-sectional area, which otherwise may have increased bone strength 10 , 70 .…”

“…Moreover, summarizing all the missions that occurred in different crafts that flew to space over 40–50 years, allows to separate the common effects of spaceflight from hazards and potential mishaps occurring within individual missions. The current study serves as a continuation of our team’s series of systematic reviews and meta-analyses regarding spaceflight-induced changes to bone in humans 6 and animals 13 . Previously, we demonstrated a significant deterioration of both cortical and trabecular bone architecture in spaceflight rodents and found bone turnover to be significantly affected 13 .…”

“…The current study serves as a continuation of our team’s series of systematic reviews and meta-analyses regarding spaceflight-induced changes to bone in humans 6 and animals 13 . Previously, we demonstrated a significant deterioration of both cortical and trabecular bone architecture in spaceflight rodents and found bone turnover to be significantly affected 13 . Here, we analyzed the data reporting changes to bone mechanical properties, bone mass, characterized by bone tissue mineral density (BMD) and bone composition in spaceflight animals.…”