Microgravity-Related Changes in Bone Density and Treatment Options: A Systematic Review.

Space travelers are exposed to microgravity (µg), which induces enhanced bone loss compared to the age-related bone loss on Earth. Microgravity promotes an increased bone turnover, and this obstructs space exploration. This bone loss can be slowed down by exercise on treadmills or resistive apparatus. The objective of this systematic review is to provide a current overview of the state of the art of the field of bone loss in space and possible treatment options thereof. A total of 482 unique studies were searched through PubMed and Scopus, and 37 studies met the eligibility criteria. The studies showed that, despite increased bone formation during µg, the increase in bone resorption was greater. Different types of exercise and pharmacological treatments with bisphosphonates, RANKL antibody (receptor activator of nuclear factor κß ligand antibody), proteasome inhibitor, pan-caspase inhibitor, and interleukin-6 monoclonal antibody decrease bone resorption and promote bone formation. Additionally, recombinant irisin, cell-free fat extract, cyclic mechanical stretch-treated bone mesenchymal stem cell-derived exosomes, and strontium-containing hydroxyapatite nanoparticles also show some positive effects on bone loss.

Latest knowledge about changes in the proteome in microgravity.

INTRODUCTION: A long-term stay of humans in space causes health problems and changes in protists and plants. Deep space exploration will increase the time humans or rodents will spend in microgravity (µg). Moreover, they are exposed to cosmic radiation, hypodynamia, and isolation. OMICS investigations will increase our knowledge of the underlying mechanisms of µg-induced alterations in vivo and in vitro. AREAS COVERED: We summarize the findings over the recent 3 years on µg-induced changes in the proteome of protists, plants, rodent, and human cells. Considering the thematic orientation of microgravity-related publications in that time frame, we focus on medicine-associated findings, such as the µg-induced antibiotic resistance of bacteria, the myocardial consequences of µg-induced calpain activation, and the role of MMP13 in osteoarthritis. All these point to the fact that µg is an extreme stressor that could not be evolutionarily addressed on Earth. EXPERT OPINION: In conclusion, when interpreting µg-experiments, the direct, mostly unspecific stress response, must be distinguished from specific µg-effects. For this reason, recent studies often do not consider single protein findings but place them in the context of protein-protein interactions. This enables an estimation of functional relationships, especially if these are supported by epigenetic and transcriptional data (multi-omics).

The Effect of Continuous Positive Airway Pressure Therapy on Obstructive Sleep Apnea-Related Hypertension.

Obstructive sleep apnea (OSA) is a common disease, with approximately 3-7% of men and 2-5% of women worldwide suffering from symptomatic OSA. If OSA is left untreated, hypoxia, microarousals and increased chemoreceptor stimulation can lead to complications like hypertension (HT). Continuous positive airway pressure (CPAP) is the most common treatment for OSA, and it works by generating airway patency, which will counteract the apnea or hypopnea. More than one billion people in the world suffer from HT, and the usual treatment is pharmacological with antihypertensive medication (AHM). The focus of this review will be to investigate whether the CPAP therapy for OSA affects HT.

The Cardiovascular System in Space: Focus on In Vivo and In Vitro Studies.

On Earth, humans are subjected to a gravitational force that has been an important determinant in human evolution and function. During spaceflight, astronauts are subjected to several hazards including a prolonged state of microgravity that induces a myriad of physiological adaptations leading to orthostatic intolerance. This review summarises all known cardiovascular diseases related to human spaceflight and focusses on the cardiovascular changes related to human spaceflight (in vivo) as well as cellular and molecular changes (in vitro). Upon entering microgravity, cephalad fluid shift occurs and increases the stroke volume (35-46%) and cardiac output (18-41%). Despite this increase, astronauts enter a state of hypovolemia (10-15% decrease in blood volume). The absence of orthostatic pressure and a decrease in arterial pressures reduces the workload of the heart and is believed to be the underlying mechanism for the development of cardiac atrophy in space. Cellular and molecular changes include altered cell shape and endothelial dysfunction through suppressed cellular proliferation as well as increased cell apoptosis and oxidative stress. Human spaceflight is associated with several cardiovascular risk factors. Through the use of microgravity platforms, multiple physiological changes can be studied and stimulate the development of appropriate tools and countermeasures for future human spaceflight missions in low Earth orbit and beyond.