Weightless osteoporosis

Weightlessness environment can lead to the muscle atrophy and body fluid distribution upward,which can cause the bone calcium metabolism disorder and always accompanied by the loss of bone microstructure and increased rate of bone fracture. Under microgravity,the astronauts are much easier to decrease the Ca2+ ion in bone, which can cause serious osteoporosis. However the bone lost is not equilibrium, it is especially serious in the mechanism loading bone and the recovery process is more difficult. These are very different from the osteoporosis in older people and postmenopausal osteoporosis...

A prolonged stay in microgravity has various negative effects on the human body; one of these problems is a noticeable demineralization of bone tissues. Such effects are quite similar to those experienced by subjects on earth affected by osteoporosis; therefore it seems quite straightforward to adopt a similar pharmacological therapy during the stay in the space. In this paper a first step in the identification of a monitoring procedure for the bone demineralization in microgravity, as well as some guidelines for the choice of adequate therapies are given...

UNLABELLED: Treatment with molecular hydrogen alleviates microgravity-induced bone loss through abating oxidative stress, restoring osteoblastic differentiation, and suppressing osteoclast differentiation and osteoclastogenesis. INTRODUCTION: Recently, it has been suggested that hydrogen gas exerts a therapeutic antioxidant activity by selectively reducing cytotoxic reactive oxygen species (ROS). The aim of the present study was to elucidate whether treatment with molecular hydrogen alleviated bone loss induced by modeled microgravity in rats...

An innovative anti-osteoporosis herbal formula containing epimedii herba, ligustri lucidi fructus and psoraleae fructus (ELP) has been previously shown its bone protecting effects in ovariectomized osteoporotic rats and also in post-menopausal osteopenic women. This study aimed to investigate the efficacy of ELP against bone loss during physical inactivity or weightlessness. A hindlimb unloading tail-suspended rat model was used for studying the effects of ELP on bone mineral density (BMD) and bone micro-architecture...

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The aim of current study was to elucidate whether aquaporin-9 (AQP9) expression was involved in the progression of bone loss induced by microgravity. We used the hind-limb suspension (HLS) mice model to simulate microgravity and induce bone loss. It was found that HLS exposure decreased femur bone mineral density (BMD), and enhanced femur AQP9 mRNA and protein levels. Then, the relationship between AQP9 mRNA expression and BMD was studied and it was showed that femur AQP9 mRNA level was negatively related to femur BMD in mice exposed to HLS...

Parathyroid hormone (PTH) is available for the treatment of osteoporosis in Japan. PTH is administered subcutaneously daily or weekly. According to the results of animal experiments, the anabolic action of PTH on bone depends on dosage, condition of loading, and region of bone. Administration of PTH preserved trabecular bone formation rate reduced by immobilization or unloading at the same level of that under the normal mobilization or loading condition, but at low dose did not preserve periosteal bone formation rate reduced by unloading...

In adulthood, bone tissue is continuously renewed by processes governed by basic multicellular units composed of osteocytes, osteoclasts and osteoblasts, which are subjected to local mechanical loads. Osteocytes are known to be integrated mechanosensors that regulate the activation of the osteoclasts and osteoblasts involved in bone resorption and apposition processes, respectively. After collagen tissue apposition, a process of collagen mineralisation takes place, gradually increasing the effective stiffness of bone...

Analysis of the results of long-term investigations of bones in cosmonauts flown on the orbital station MIR and International space station (n = 80) was performed. Theoretically predicted (evolutionary predefined) change in mass of different skeleton bones was found to correlate (r = 0.904) with position relatively the Earth's gravity vector. Vector dependence of bone loss ensues from local specificity of expression of bone metabolism genes which reflects mechanic prehistory of skeleton structures in the evolution of Homo erectus...

Microgravity environment like space flight or a condition requiring long-term bed-rest increase bone resorption and decrease bone formation, inducing the rapid decrease of bone minerals to osteoporosis. Bone mineral loss increases urinary calcium excretion and the risk of urinary stone formation. To clarify the influence of the conditions on renal stone formation, a 90-day bed rest test was performed to analyze the mechanism of microgravity or bed rest-induced stone formation and prevention by bisphosphonate medication and bed-rest exercise...

No abstract text is available yet for this article.

Exposure to microgravity has been associated with several physiological changes in astronauts, including an osteoporosis-like loss in bone mass. Despite many in vivo and in vitro studies in both microgravity and simulated microgravity conditions, the mechanism for bone loss is still not clear. The lack of weight-bearing forces makes microgravity an ideal physical stimulus to assess bone cell responses. In this work, we conduct a unique investigation of the effects of microgravity on bone-producing osteoblasts and, in parallel, on bone-resorbing osteoclasts...

Osteoporosis, or rather the localised bone loss observed in patients with spinal cord injury, as well as during any type of immobilisation involves various processes and structures including the direct response of the musculoskeletal system to unloading, the central and peripheral nervous systems and their effects on bone cells and on the vascular system, the bone remodelling unit in its marrow compartment and a number of local factors controlling cell-cell cross-talk as well as calciotropic hormones. The authors present a detailed review of these different mechanisms which are all involved regardless of the type of immobilisation: pathological, environmental, or experimental...

It has always been a desire of mankind to conquest Space. A major step in realizing this dream was the completion of the International Space Station (ISS). Living there for several months confirmed early observations of short-term spaceflights that a loss of gravity affects the health of astronauts. Space medicine tries to understand the mechanism of microgravity-induced health problems and to conceive potent countermeasures. There are four different aspects which make space medicine appealing: i) finding better strategies for adapting astronauts to weightlessness; ii) identification of microgravity-induced diseases (e...

Bone loss is one of the most important complications for astronauts who are exposed to long-term microgravity in space and also for bedridden elderly people. Recent studies have indicated that the sympathetic nervous system plays a role in bone metabolism. This paper reviews findings concerning with sympathetic influences on bone metabolism to hypothesize the mechanism how sympathetic neural functions are related to bone loss in microgravity. Animal studies have suggested that leptin stimulates hypothalamus increasing sympathetic outflow to bone and enhances bone resorption through noradrenaline and β-adrenoreceptors in bone...

In astronauts and cosmonauts, exposure to microgravity has been associated with several physiological changes, including an osteoporosis like loss of bone mass. It has been reported that head-down tilt bed-rest studies mimic many of the observations seen in space flights. There has been no study of the effects of mandibular bone and alveolar bone loss in both sexes under conditions of simulated microgravity. This study was designed to investigate bone mineral density; bone mineral content; matrix metalloproteinase (MMP)-8, MMP-9, cathepsin K, and osteocalcin levels in gingival crevicular fluid (GCF); and salivary and serum osteocalcin levels in normal healthy men and women under conditions of simulated microgravity, namely, -6° head-down-tilt (HDT) bed rest...

Long-term bed-rest is used to simulate the effect of spaceflight on the human body and test different kinds of countermeasures. The 2nd Berlin BedRest Study (BBR2-2) tested the efficacy of whole-body vibration in addition to high-load resisitance exercise in preventing bone loss during bed-rest. Here we present the protocol of the study and discuss its implementation. Twenty-four male subjects underwent 60-days of six-degree head down tilt bed-rest and were randomised to an inactive control group (CTR), a high-load resistive exercise group (RE) or a high-load resistive exercise with whole-body vibration group (RVE)...

OBJECTIVE: To study the effect of microfilament cytoskeleton changes induced by simulated microgravity on the NO/NOS system of osteoblasts, and explore the mechanism of weightlessness leading to osteoporosis. METHODS: Mouse osteoblast-like cell line MC3T3-E1 were divided into simulated microgravity (by rotating clinostat) group, 0.5 microg/ml cytochalasins B group, simulated microgravity+cytochalasins B group, and normal gravity group. After cell culture for 48 h with corresponding treatments, immunofluorescence staining of the cells by FITC-phallacidin was performed to observe the changes of microfilament under laser confocal microscope...

Astronauts experience bone loss after the long spaceflight missions. Identifying specific regions that undergo the greatest losses (e.g. the proximal femur) could reveal information about the processes of bone loss in disuse and disease. Methods for detecting such regions, however, remains an open problem. This paper focuses on statistical methods to detect such regions. We perform statistical parametric mapping to get t-maps of changes in images, and propose a new cross-validation method to select an optimum suprathreshold for forming clusters of pixels...

Bone loss and renal stone are significant medical concerns for bed rest subjects and space flight astronauts. Bone mineral loss occurs as secondary osteoporosis due to the unloading of weight bearing bones during bed rest and space flight. Increased bone resorption and bone metabolic uncoupling promote bone loss through the release of calcium from unloaded weight bearing bones. The rate of bone mineral loss during bed rest and space flight is about 1-2 percent per month, and recovery requires a period three or four times longer...