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Vitamin D pathway mediates production of active forms of vitamin D during space flight and ground based simulations.  T.G. Hammond and P.L. Allen. Tulane University Health Sciences Center and VA Medical Center, New Orleans, LA.

   Keeping the specialized features of cells intact in tissue culture continues to be a roadblock for many applications related to bioproduction of pharmaceuticals, and testing of drug effects and interactions.  We tested for the best mechanical culture conditions to optimize expression of vitamin D pathway molecules in renal cell culture.  Human renal cells were cultured in the rotating wall vessel (RWV), a form of suspension culture optimized to minimize shear (and mimicking some of the conditions of space flight), in the true microgravity of space, and in static ground based controls. The human renal cells expressed the vitamin D receptor, and parathyroid hormone receptor as evidenced by gene expression assayed on gene arrays, and protein expression assayed by flow cytometry antibody binding.  Confocal microscopy confirms translocation of the vitamin D receptor from cytoplasm to nucleus in space.   The 1-alpha hydroxylase enzyme, which catalyzes the production of the active 1-25-diOH form of Vitamin D, was expressed in RWV cultures, but not static controls, and greatly increased in space. Hence, the renal cell gene and protein expression changes observed in space and RWV are partly vitamin D receptor mediated, and these cultures provide a unique tool in which regulatory elements of the vitamin D pathway are expressed concomitantly.