Short-term, daily exposure to cold temperature may be an efficient way to prevent muscle atrophy and bone loss in a microgravity environment

Bone mineral metabolism and different indices of skeletal health of Ladakhi women living at high altitude

Objectives

High altitude possesses a great challenge for human survival owing to low oxygen tension and has been reported to cause bone deterioration among sojourns of high altitude. The bone health of Ladakhi women is investigated for the first time in this study.

Methods

Dual energy X-ray absorptiometry of Ladakhi women and sea level women was done at the radius and calcaneus using EXA-3000 (Osteosys, Korea), followed by colorimetric and Enzyme Linked Immunosorbent Assay analysis of parameters regulating bone health.

Results

There was no statistically significant difference between bone mineral density of Ladakhi women and sea level women at radius (P = 0.287) or calcaneus (P = 0.839). Almost similar cases of osteopenia were reported at both sites measured in the study among both groups. Two post-menopausal Ladakhi women however, had osteoporosis at the radius while 4 had osteoporosis at calcaneus. Significant increase in calcium levels with a decrease in intact parathyroid hormone and an increase in calcitonin levels were observed in Ladakhi women as compared to sea level women. Though there was no significant difference in 25-hydroxy vitamin D levels of both groups, a higher percentage of 25-hydroxy vitamin D deficiency (77% vs 23%) was observed in Ladakhi women as compared to sea level women. Estradiol levels were similar in both groups.

Conclusions

The present study suggest that there is no significant relationship between high altitude living and bone mineral density among Ladakhi women.

Media Exchange Performance Test Using the Bradford Assay in an Automated Bioreactor Engineering Model for Space Experiments

Life science research has been actively carried out in space for a long time using bioreactor equipment, in anticipation of manned space exploration and space tourism. Such studies have reported that the microgravity environment has a negative effect on the human body, including the musculoskeletal system, nervous system, and endocrine system. Bone loss and muscular atrophy are issues that need to be resolved before long-term exposure of the human body to a space environment. To address this problem, Y. K. Kim et al. designed a system in 2015 and performed an evaluation of an automated bioreactor development model (DM) for space experiments. In this study, we developed an automated bioreactor engineering model (EM) based on the previous literature, and conducted media exchange performance testing using the Bradford assay. We used a novel method that allowed quantitative assessment of the media exchange rate versus the conventional assessment method using visual observation with a camera. By measuring the media exchange rate of the automated bioreactor EM, we attempted to verify applicability for the system for space experiments. We expect that the experimental method proposed in this study is useful for logical determination of liquid exchange or circulation in different closed systems.

Mimicking the effects of spaceflight on bone: Combined effects of disuse and chronic low-dose rate radiation exposure on bone mass in mice

During spaceflight, crewmembers are subjected to biomechanical and biological challenges including microgravity and radiation. In the skeleton, spaceflight leads to bone loss, increasing the risk of fracture. Studies utilizing hindlimb suspension (HLS) as a ground-based model of spaceflight often neglect the concomitant effects of radiation exposure, and even when radiation is accounted for, it is often delivered at a high-dose rate over a very short period of time, which does not faithfully mimic spaceflight conditions. This study was designed to investigate the skeletal effects of low-dose rate gamma irradiation (8.5 cGy gamma radiation per day for 20 days, amounting to a total dose of 1.7 Gy) when administered simultaneously to disuse from HLS. The goal was to determine whether continuous, low-dose rate radiation administered during disuse would exacerbate bone loss in a murine HLS model. Four groups of 16 week old female C57BL/6 mice were studied: weight bearing + no radiation (WB+NR), HLS + NR, WB + radiation exposure (WB+RAD), and HLS+RAD. Surprisingly, although HLS led to cortical and trabecular bone loss, concurrent radiation exposure did not exacerbate these effects. Our results raise the possibility that mechanical unloading has larger effects on the bone loss that occurs during spaceflight than low-dose rate radiation.

CKIP-1 knockout offsets osteoporosis induced by simulated microgravity

Casein kinase 2-interacting protein 1 (CKIP-1) is a negative regulator for bone formation. CKIP-1 knockout (KO) mice are very important for research on countermeasures to bone loss induced by space microgravity. Under simulated microgravity, the bone metabolism of CKIP-1 KO mice was different than that of wild-type (WT) mice. Many experiments all showed that the KO mice had significantly enhanced ossification in the tail suspension conditions, and the differences were closely related to the time the mice were exposed to the microgravity environment. Our results reveal the effect of CKIP-1 on the regulation of bone metabolism and osteogenesis in vivo and the ability of this gene to offset osteoporosis, and they suggest an approach to the treatment of osteoporosis induced by microgravity in space.