EFFECTS OF MICROGRAVITY ON THE ACTION OF VITAMIN D IN OSTEOBLASTS (VITAMIN D)
Research Area: Cellular Biology
Expedition(s): 5
Principal Investigator(s): ● Roger Bouillon, Katholieke Universiteit Leuven, Leuven,
Belgium
RESEARCH OBJECTIVES
The first objective of the Effects of Microgravity on the Action of Vitamin D in Osteoblasts
(Vitamin D) is to elucidate whether space-induced alterations in 1, 25(OH) 2vitaminD3
regulated gene expression is a generalized phenomenon or species-specific. The second
objective is to study the mechanisms underlying space-related alterations in gene expression in
osteoblasts.
RESULTS
After transfection and selection, 3 MC3T3-VDRE colonies showed a time- and dose-dependent
increase in growth hormone release following treatment with 1,25(OH)2D3. Noteworthy, the
induction of growth hormone was less in the stable transfectants than after transient
transfection, most likely because less copies of the construct were present in the former. The
growth hormone response of the selected MC3T3-VDRE cell line was not manifestly altered
when cells were cultured in the plunger box units and when the temperature profile of the
spaceflight was applied. The preparation and course of both spaceflight and ground experiment
went uncomplicated.
Five days of microgravity during the Odissea mission (Soyuz 5S/Soyuz 4S exchange) did not
affect the level of 1, 25(OH) 2D3-induced growth hormone expression per cell, which was used
as reporter. It has, however, to be remarked that no 1-g centrifuge was present during the
flight. An inflight 1-g experiment remains the ideal control as gravity is at that moment the only
parameter differing between the 2 conditions. These data indicate that in this model where
only certain aspects of the 1, 25(OH) 2D3 signaling cascade are analyzed, the endpoint of the 1,
25(OH) 2D3 signaling cascade, namely gene transcription and protein synthesis of a reporter
gene, was not altered by microgravity. However changes in the different aspects of the 1,
Vitamin D plunger box unit. ESA image.