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Cellular Mechanics and Gene Expression under Microgravity

   Oxygen utilization by and oxygen dependence of cellular processes may be different in biological systems that are exposed to microgravity.  A baseline in which cellular changes in oxygen sensitive molecular processes occur during microgravity conditions would be important to pursue this question.  Cellular mechanics and oxygen-sensitive gene expression under simulated microgravity have been investigated and correlated to the patho-physiological changes that occur at the cellular and molecular (DNA, RNA, and Protein) level.

 

In-Vitro Cell Culture Study:

i) DNA Microarray study: This study uses the rotating wall vessel bioreactor designed at NASA to simulate microgravity.  Gene expression in PC12 cells in response to microgravity was analyzed by DNA microarray technology.  The microarray analysis of PC12 cells cultured for four days under simulated microgravity under standardized oxygen environment conditions revealed more than 100 genes whose expression levels were changed at least two fold compared with those from cells in the unit gravity control.  This study observed that genes involved in the oxidoreductase activity category were most significantly differentially expressed under microgravity conditions. A typical up and down regulation of genes is shown below (Fig. 1).

 microgravity1

 

ii) Protein study: Based on the DNA microarray results, nuclear translocation of the nuclear factor kappa B (NF-kB) p65 in a cardiomyocyte cell line (H9c2), which has relevance to the astronauts’ cardiac physiology, was assessed by monitoring the levels of p65 in the nuclear lysates.  NF-κB p65 protein revealed differential expression under MG and DC conditions.  Mean activations of p65 protein were 69% for MG and 46% for DC as compared to positive control which were stimulated with TNF-a for 30 min (* p<0.05, n=3, Fig. 2).  The results from western blots were confirmed by enzyme-linked immunosorbent assay (ELISA), which showed 66% for MG and 45% for DC.  This transcription-factor result establishes a foundation for further exploration on specific physiological endpoints such as muscle atrophy phenomena.

 microgravity2

 

iii) Computational Analysis of O2 Transport in RWV: The present study is to determine the appropriate suspension conditions for the microcarrier beads/cell distribution and evaluate oxygen transport and to validate the physio-chemical changes in the RWV bioreactor.The rotating speed of the vessel needed to increase as the cell/bead diameters became larger, implying the growth of cell aggregates (Fig. 3).

 

microgravity3

 

This research is partially funded by NASA-Glenn: Microgravity Division.

by zopeown last modified 2008-03-17 23:06