Abstract
The Mongolian gerbil displays unique physiological and anatomical features that make this species an attractive object for biological experiments in space. However, until recently, the Mongolian gerbil has remained a novel, mostly unstudied animal model in investigating bone loss in weightlessness (G0). After 12 days of orbital Foton-M3 mission, the humerus of Mongolian gerbils has been studied here via micro-computed tomography (micro-CT) to quantify bone morphometric parameters. The samples from the flight group, delayed synchronous ground-control group, and basal control group were investigated, and main morphometric parameters were reported in the article. The accurate selection of a region of interest is an essential step for a correct assessment of bone parameters. We proposed a new, easy and efficient method for delimiting the bone’s basic regions in the humerus. It is based on quantitative estimation of X-ray attenuation in the cortical bone as a function of humerus bone length. The micro-CT analysis of the basic bone regions revealed a difference in bone morphometric parameters between the flight and control gerbils. The most significant bone loss was observed in the cortical part of the proximal humeral zone in the flight group. No statistically significant changes of volume fraction in the cancellous tissue of proximal and distal epiphyses and metaphyses were observed. A statistically significant increase in both cancellous bone volume and bone X-ray attenuation in the flight group was detected in the proximal part of the diaphyses. We assume that enhanced calcium deposition in the diaphyseal cancellous tissue occurred due to a bone response to G0 conditions.
Highlights
After 12 days of orbital Foton-M3 mission, the humerus of the Mongolian gerbil has been studied by us via X-ray micro-computed tomography to identify bone morphometric parameters
We found that bone volume fraction (BV/total volume (TV)) in the gerbils of the flight group was 9.1% less than that in the control group
The humerus mineral loss began from dense cortical areas; the most significant alteration was observed in the proximal EM-zone
Summary
After 12 days of orbital Foton-M3 mission, the humerus of the Mongolian gerbil has been studied by us via X-ray micro-computed tomography (micro-CT) to identify bone morphometric parameters. The negative impact of spaceflight on the human and animal skeleton is well known and remains a critical issue until nowadays (Clément, 2011; Nagaraja and Risin, 2013; Berg-Johansen et al, 2016). Studies of a human bone system in G0 detected an average bone loss of 1–2% per month, during the flight at the Russian “Mir” spacecraft and International Space Station (ISS) (Lang et al, 2004; Clément, 2011; Sibonga et al, 2015). Most of the current publications reported cancellous tissue loss in the weight-bearing bones (Lang et al, 2004, 2017; Bloomfield et al, 2011; Nagaraja and Risin, 2013; Gerbaix et al, 2017; Maupin et al, 2019; Tominari et al, 2019). The appropriate animal model has become increasingly important for space-based biomedical research
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