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Cell behaviour in simulated microgravity: a comparison of results obtained with RWV and RPM.   1A. Villa, 1S. Versari, 1S. Bradamante , 2S. Cotrupi, 2D. Ranzani, 2J.A.M. Maier, 1CNR-ISTM, Via Golgi 19, Milan, and 2Dept. Preclinical Sciences-LITA Vialba, University of Milan, Via GB Grassi, Milan — Italy.

   It is now clear that some pathological conditions described in astronauts - such as motion sickness, muscular atrophy, bone demineralization, cardiovascular deconditioning — represent the adaptative response to the absence of gravity and are due, at least in part, to the effects exerted by microgravity at the cellular level. Indeed, a number of studies have indicated that gravity affects mammalian cell growth and differentiation through the modulation of gene expression.  We have shown that human macrovascular endothelial cells cultured in the NASA-developed bioreactor Rotating Well Vessel (RWV) grow faster than controls because they downregulate interleukin 1 , an inhibitor of endothelial growth. In addition, the cells rapidly remodel their cytoskeleton. The same results were obtained when we utilized the ESA-developed bioreactor denominated Random Positioning Machine (RPM) to simulate microgravity. All the effects we observed are promptly reversible upon return to normal culture conditions.

   We also compared the growth of the human monocytic cell line U937 in the RWV and in the RPM and found a reversible inhibition of cell growth. Under both conditions, U937 cells maintain their capability to differentiate in response to the phorbol ester PMA.

   We conclude that culture in the RWV and RPM exert similar effects on cell behaviour and represent a good tool to characterize cell behaviour in simulated microgravity.