Among the physiological consequences of extended spaceflight are loss of skeletal muscle and bone mass. One signaling pathway that plays an important role in maintaining muscle and bone homeostasis is that regulated by the secreted signaling proteins myostatin (MSTN) and activin A. Here we used both genetic and pharmacological approaches to investigate the effect of targeting MSTN/activin A signaling in mice that were sent to the International Space Station. Wild type mice lost significant muscle and bone mass during the 33 d spent in microgravity. Muscle weights of Mstn -/- mice which are about twice those of wild type mice were largely maintained during spaceflight. Systemic inhibition of MSTN/activin A signaling using a soluble form of the activin type IIB receptor (ACVR2B) which can bind each of these ligands led to dramatic increases in both muscle and bone mass with effects being comparable in ground and flight mice. Exposure to microgravity and treatment with the soluble receptor each led to alterations in numerous signaling pathways which were reflected in changes in levels of key signaling components in the blood as well as their RNA expression levels in muscle and bone. These findings have implications for therapeutic strategies to combat the concomitant muscle and bone loss occurring in people afflicted with disuse atrophy on Earth as well as in astronauts in space especially during prolonged missions.

The general objective of the study was to determine modulation of gene expression by environmental factors, with a special emphasis on bone formation. For this reason, the specific period of treatment was chosen between 5-6 days post-fertilization (dpf), when bone formation and calcification are taking place. Zebrafish larvae were placed at 5 dpf into a Large Diameter Centrifuge and brought to a gravitational force of 3g or 5g for 24 hours. We show that this treatment causes a clear increase of bone formation, as illustrated by cranial skeleton staining of the bone matrix by Alizarin Red, by morphometric analysis of the resulting images and by gene expression studies of selected genes. Thus, a whole genome micro-array experiment was conducted to identify genes that may be involved in the observed effect on bone formation.

The general objective of the study was to determine modulation of gene expression by environmental factors with a special emphasis on bone formation. For this reason the specific period of treatment was chosen between 5-6 days post-fertilization (dpf) when bone formation and calcification are taking place. This experiment was designed as a new type of gravitational experiment which we like to call relative microgravity referring to the fact that the larvae first grow in hyper gravity for 5 days and are then returned to 1g normal gravity for 1 day. Zebrafish embryos were placed on a Large Diameter Centrifuge at 3 hpf brought to a gravitational force of 3 g until 5 dpf. Reference embryos were kept in parallel at 1g (Inc). At 5dpf one batch was left at 3g (3g) one batch was returned to 1g (3g>1g) while a third batch was returned to 1g but left on the axis of the centrifuge (Axe; 3g>Axe). The experiment was repeated 4 times each time with 4 batches of 60 larvae.

Gene expression profile of two-week-old etiolated Arabidopsis seedlings under microgravity on board space flight BRIC16 were compared with ground grown control in both wild-type and act2-3 mutant plants.

Comparative gene expression in skin between mice maintained in microgravity (0g) and normogravity (1g) environment. Six male C57Bl/J10 mice were housed for 91 days in the specially designed Mouse Drawer System in weightlessness aboard the International Space Station. Three wild-type mice (WT) and three transgenic mice overexpressing the osteogneic factor PTN/OSF1 under the control of the human bone specific ostecalcin promoter (Tg) were used in the experiment. During the 3-month stay on the ISS 3 mice unfortunately died leaving 2 Tg and 1 WT. MDS tissue sharing program allowed several teams to study various tissues from these mice. Our aim was to investigate the effect of such a long period of microgravity on skin physiology by morphological biochemical and genomewide analyses by comparison to similar mice on ground. Gene expression in the skin of 3 space mice and of 3 ground mice was analyzed by microarray. As this unique experiment performed on 3 mice limits the power of statistical analyis as the transgene PTN/OSF1 was not overexpressed in skin and as a pair wise Pearson s correlation rates between the individual levels of expressed transcripts in the WT and the Tg mice were not significantly different from each other in one experimental group (space or ground) data from the 3 mice were combined to compare results from the space an ground groups.

Arabidopsis were grown on horizontal or vertical clinostat for 4 8 or 12 days. Seedlings on horizontal clinostat were in simulated microgravity and seedlings on vertical clinostat are considered as a control. Comparison was made between plants grown on simulated microgravitry and vertical position. 6 dye-swap - treated vs untreated comparison

Arabidopsis were grown on horizontal or vertical clinostat for 4 8 or 12 days. Seedlings on horizontal clinostat were in simulated microgravity and seedlings on vertical clinostat are considered as a control. Comparison was made between plants grown on simulated microgravitry and vertical position. 6 dye-swap - treated vs untreated comparison

Gene expression profile of two-week-old etiolated Arabidopsis seedlings under microgravity on board space flight BRIC16 were compared with ground grown control in both wild-type and act2-3 mutant plants.

Comparitive gene expression in skin between mice maintained in microgravity (0g) and normogravity (1g) environment. Six male C57Bl/J10 mice were housed for 91 days in the specially designed Mouse Drawer System in weightlessness aboard the International Space Station. Three wild-type mice (WT) and three transgenic mice overexpressing the osteogneic factor PTN/OSF1 under the control of the human bone specific ostecalcin promoter (Tg) were used in the experiment. During the 3-month stay on the ISS 3 mice unfortunately died leaving 2 Tg and 1 WT. MDS tissue sharing program allowed several teams to study various tissues from these mice. Our aim was to investigate the effect of such a long period of microgravity on skin physiology by morphological biochemical and genomewide analyses by comparison to similar mice on ground. Gene expression in the skin of 3 space mice and of 3 ground mice was analyzed by microarray. As this unique experiment performed on 3 mice limits the power of statistical analyis as the transgene PTN/OSF1 was not overexpressed in skin and as a pair wise Pearson s correlation rates between the individual levels of expressed transcripts in the WT and the Tg mice were not significantly different from each other in one experimental group (space or ground) data from the 3 mice were combined to compare results from the space an ground groups.

The general objective of the study was to determine modulation of gene expression by environmental factors with a special emphasis on bone formation. For this reason the specific period of treatment was chosen between 5-6 days post-fertilization (dpf) when bone formation and calcification are taking place. Zebrafish larvae were placed at 5 dpf into a Large Diameter Centrifuge and brought to a gravitational force of 3g or 5g for 24 hours. We show that this treatment causes a clear increase of bone formation as illustrated by cranial skeleton staining of the bone matrix by Alizarin Red by morphometric analysis of the resulting images and by gene expression studies of selected genes. Thus a whole genome micro-array experiment was conducted to identify genes that may be involved in the observed effect on bone formation.