Mineralization and growth of cultured embryonic skeletal tissue in microgravity

Genetic variability affects the skeletal response to immobilization in founder strains of the diversity outbred mouse population

Mechanical unloading decreases bone volume and strength. In humans and mice, bone mineral density is highly heritable, and in mice the response to changes in loading varies with genetic background. Thus, genetic variability may affect the response of bone to unloading. As a first step to identify genes involved in bones' response to unloading, we evaluated the effects of unloading in eight inbred mouse strains: C57BL/6J, PWK/PhJ, WSB/EiJ, A/J, 129S1/SvImJ, NOD/ShiLtJ, NZO/HlLtJ, and CAST/EiJ. C57BL/6J and NOD/ShiLtJ mice had the greatest unloading-induced loss of diaphyseal cortical bone volume and strength. NZO/HlLtJ mice had the greatest metaphyseal trabecular bone loss, and C57BL/6J, WSB/EiJ, NOD/ShiLtJ, and CAST/EiJ mice had the greatest epiphyseal trabecular bone loss. Bone loss in the epiphyses displayed the highest heritability. With immobilization, mineral:matrix was reduced, and carbonate:phosphate and crystallinity were increased. A/J mice displayed the greatest unloading-induced loss of mineral:matrix. Changes in gene expression in response to unloading were greatest in NOD/ShiLtJ and CAST/EiJ mice. The most upregulated genes in response to unloading were associated with increased collagen synthesis and extracellular matrix formation. Our results demonstrate a strong differential response to unloading as a function of strain. Diversity outbred (DO) mice are a high-resolution mapping population derived from these eight inbred founder strains. These results suggest DO mice will be highly suited for examining the genetic basis of the skeletal response to unloading.

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Mouse strain affects bone's response to immobilization.

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Magnitude of bone loss from immobilization is heritable.

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Bone transcriptomic response to immobilization is influenced by genetic variation.

Influence of Microgravity on Apoptosis in Cells, Tissues, and Other Systems In Vivo and In Vitro

All life forms have evolved under the constant force of gravity on Earth and developed ways to counterbalance acceleration load. In space, shear forces, buoyance-driven convection, and hydrostatic pressure are nullified or strongly reduced. When subjected to microgravity in space, the equilibrium between cell architecture and the external force is disturbed, resulting in changes at the cellular and sub-cellular levels (e.g., cytoskeleton, signal transduction, membrane permeability, etc.). Cosmic radiation also poses great health risks to astronauts because it has high linear energy transfer values that evoke complex DNA and other cellular damage. Space environmental conditions have been shown to influence apoptosis in various cell types. Apoptosis has important functions in morphogenesis, organ development, and wound healing. This review provides an overview of microgravity research platforms and apoptosis. The sections summarize the current knowledge of the impact of microgravity and cosmic radiation on cells with respect to apoptosis. Apoptosis-related microgravity experiments conducted with different mammalian model systems are presented. Recent findings in cells of the immune system, cardiovascular system, brain, eyes, cartilage, bone, gastrointestinal tract, liver, and pancreas, as well as cancer cells investigated under real and simulated microgravity conditions, are discussed. This comprehensive review indicates the potential of the space environment in biomedical research.

Effects of spaceflight on cartilage: implications on spinal physiology

Spaceflight alters normal physiology of cells and tissues observed on Earth. The effects of spaceflight on the musculoskeletal system have been thoroughly studied, however, the effects on cartilage have not. This area is gaining more relevance as long duration missions, such as Mars, are planned. The impact on intervertebral discs and articular cartilage are of particular interest to astronauts and their physicians. This review surveys the literature and reports on the current body of knowledge regarding the effects of spaceflight on cartilage, and specifically changes to the spine and intervertebral disc integrity and physiology. A systematic literature review was conducted using PubMed, MEDLINE, and Google Scholar. Eighty-six unique papers were identified, 15 of which were included. The effect of spaceflight on cartilage is comprehensively presented due to limited research on the effect of microgravity on the spine/intervertebral discs. Cellular, animal, and human studies are discussed, focusing on human physiologic changes, cartilage histology, mineralization, biomechanics, chondrogenesis, and tissue engineering. Several common themes were found, such as decreased structural integrity of intervertebral disks and impaired osteogenesis/ossification. However, studies also presented conflicting results, rendering strong conclusions difficult. The paucity of human cartilage studies in spaceflight leaves extrapolation from other model systems the only current option for drawing conclusions despite known and unknown limitations in applicability to human physiology, especially spinal pathophysiology which is special interest. The aerospace and biomedical research communities would benefit from further human spaceflight articular cartilage and intervertebral disc studies. Further research may yield beneficial application for spaceflight, and crossover in understanding and treating terrestrial diseases like osteoarthritis and vertebral disc degeneration.

Norman K. Wessells: a life in science

"In its triple role as locomotory organelle, as a site of deposition of new surface material for the elongating axon, and a source of microspikes (sensory probes), the growth cone becomes the key to axon elongation" Yamada et al. (1971).

Invited review: what do we know about the effects of spaceflight on bone?

This review of the peer-reviewed literature focuses on the effects of spaceflight on bone. Studies performed in humans and laboratory animals have revealed abnormalities in bone and mineral metabolism that suggest that long-duration spaceflight will have detrimental effects on the skeleton. However, because of large gaps in our knowledge, it is not presently possible to estimate the magnitude of the health risk, individual variations in risk, effective countermeasures, or mechanism(s) of action. Specific recommendations are made for future research to ascertain risk and develop appropriate countermeasures.