Timo Frett

Moderate alterations of the cytoskeleton in human chondrocytes after short-term microgravity produced by parabolic flight maneuvers could be prevented by up-regulation of BMP-2 and SOX-9

Real and simulated microgravity induce a variety of changes in human cells. Most importantly, changes in the cytoskeleton have been noted, and studies on microtubules have shown that they are gravisensitive. This study focuses on the effects of short‐term real microgravity on gene expression, protein content, and cytoskeletal structure of human chondrocytes. We cultivated human chondrocytes, took them along a parabolic flight during the 24th Deutsches Zentrum für Luft‐ und Raumfahrt Parabolic (DLR) Flight Campaign, and fixed them after the 1st and the 31st parabola. Immunofluorescence microscopy revealed no changes after the 1st parabola, but disruptions of β‐tubulin, vimentin, and cytokeratin networks after the 31st parabola. No F‐actin stress fibers were detected even after 31 parabolas. Furthermore, mRNA and protein quantifications after the 31st parabola showed a clear up‐regulation of cytoskeletal genes and proteins. The mRNAs were significantly up‐regulated as follows: TUBB, 2‐fold; VIM, 1.3‐fold; KRT8, 1.8‐fold; ACTB, 1.9‐fold; ICAM1, 4.8‐fold; OPN, 7‐fold; ITGA10, 1.5‐fold; ITGB1, 1.2‐fold; TGFB1, 1.5‐fold; CAV1, 2.6‐fold; SOX9, 1.7‐fold; BMP‐2, 5.3‐fold. However, SOX5 (‐25%) and SOX6 (‐28%) gene expression was decreased. Contrary, no significant changes in gene expression levels were observed during vibration and hypergravity experiments. These data suggest that short‐term microgravity affects the gene expression of distinct proteins. In contrast to poorly differentiated follicular thyroid cancer cells or human endothelial cells, chondrocytes only exert moderate cytoskeletal alterations. The up‐regulation of BMP‐2, TGF‐β1, and SOX9 in chondrocytes may play a key role in preventing cytoskeletal alterations.—Aleshcheva, G., Wehland, M., Sahana, J., Bauer, J., Corydon, T. J., Hemmersbach, R., Frett, T., Egli, M., Infanger, M., Grosse, J., Grimm, D. Moderate alterations of the cytoskeleton in human chondrocytes after short‐term microgravity produced by parabolic flight maneuvers could be prevented by up‐regulation of BMP‐2 and SOX‐9. FASEB J. 29, 2303‐2314 (2015). www.fasebj.org

Differential gene expression of human chondrocytes cultured under short-term altered gravity conditions during parabolic flight maneuvers

BackgroundChondrocytes are the main cellular component of articular cartilage. In healthy tissue, they are embedded in a strong but elastic extracelluar matrix providing resistance against mechanical forces and friction for the joints. Osteoarthritic cartilage, however, disrupted by heavy strain, has only very limited potential to heal. One future possibility to replace damaged cartilage might be the scaffold-free growth of chondrocytes in microgravity to form 3D aggregates.ResultsTo prepare for this, we have conducted experiments during the 20th DLR parabolic flight campaign, where we fixed the cells after the first (1P) and the 31st parabola (31P). Furthermore, we subjected chondrocytes to isolated vibration and hypergravity conditions. Microarray and quantitative real time PCR analyses revealed that hypergravity regulated genes connected to cartilage integrity (BMP4, MMP3, MMP10, EDN1, WNT5A, BIRC3). Vibration was clearly detrimental to cartilage (upregulated inflammatory IL6 and IL8, downregulated growth factors EGF, VEGF, FGF17). The viability of the cells was not affected by the parabolic flight, but showed a significantly increased expression of anti-apoptotic genes after 31 parabolas. The IL-6 release of chondrocytes cultured under conditions of vibration was not changed, but hypergravity (1.8 g) induced a clear elevation of IL-6 protein in the supernatant compared with corresponding control samples.ConclusionTaken together, this study provided new insights into the growth behavior of chondrocytes under short-term microgravity.

Gender bias in the influence of gravity on perception

INTRO Females are influenced more than males by visual cues during many spatial orientation tasks; but females rely more heavily on gravitational cues during visual-vestibular conflict. Are there gender biases in the relative contributions of vision, gravity and the internal representation of the body to the perception of upright? And might any such biases be affected by low gravity? METHODS 16 participants (8 female) viewed a highly polarized visual scene tilted ±112° while lying supine on the European Space Agency’s short-arm human centrifuge. The centrifuge was rotated to simulate 24 logarithmically spaced g-levels along the long axis of the body (0.04-0.5g at ear-level). The perception of upright was measured using the Oriented Character Recognition Test (OCHART). OCHART uses the ambiguous symbol “p“ shown in different orientations. Participants decided whether it was a “p“ or a “d“ from which the perceptual upright (PU) can be calculated for each visual/gravity combination. The relative contribution of vision, gravity and the internal representation of the body were then calculated. Experiments were repeated while upright. RESULTS The relative contribution of vision on the PU was less in females compared to males (t=-18.48, p≤0.01). Females placed more emphasis on the gravity cue instead (f:28.4%, m:24.9%) while body weightings were constant (f:63.0%, m:63.2%). When upright (1g) in this and other studies (e.g., Barnett-Cowan et al. 2010, EJN, 31,1899) females placed more emphasis on vision in this task. CONCLUSIONS The shift in weight allocated by females to vision when in simulated low-gravity conditions, may be related to females’ response to other instances of visual-vestibular conflict. Why this is the case and at which point the perceptual change happens requires further research.