Vitamin D

1. R. Bouillon - G. Carmeliet Legendo K.U. Leuven Herestraat 49, 3000 Leuven tel: 32-16-34.60.23 e-mail : geert.carmeliet@med.kuleuven.ac.be Vitamin D

2. Introduction: normal bone metabolism bone resorption bone formation equilibrium osteoclast osteoblast osteoid osteocyte mineralized matrix

3. Introduction: spaceflight induces bone loss 1 2 3 weeks 0 resorption -2 formation % difference from control -4 bone mass -6

4. UNLOADING    Introduction: spaceflight decreases bone formation bone marrow stromal cell  proliferation + preosteoblast osteoclast osteoid mineralized matrix

5.  Introduction: spaceflight induces changes in osteoblast characteristics change in gene expression change in gravity growth factors growth factor receptors ? change in adhesion extracellular matrix

6. characterization of effect of microgravity on gene expression by osteoblasts identification of effect of microgravity on intracellular pathways AIM of microgravity project

7. previous MG63 cells: human osteosarcoma cell line stimulus: vitamin D + Transforming Growth Factor  endpoints: change in matrix proteins, growth factors present different species, correlation with transgenic mice MC3T3-E1 cells: mouse osteoblastic cells stimulus: vitamin D endpoints: matrix proteins, growth factors, metabolism Model: cellular mechanisms

8. Model: molecular mechanisms NUCLEUS Vitamin D GENE TRANSCRIPTION VDR VDR DNA interaction of vitamin D receptor (VDR) and DNA: stable cell line with reporter construct

9. Technical outline : cell culture unit L M S L M M M: medium S: stimulus L: lysis MC3T3-E1 cells on thermanox slide

10. 1 Technical outline: manipulations and timeline t0 =start of exp. timeline Transfer CTA from Soyuz to ISS Set CTA temperature to +37°C Medium Exchange (4 plungers) Cell lysis (4 plungers) Activate 4 plungers 2 3 4 5 22°C 0xg 22°C >> 37°C 37°C 48 h 37°C 72 h CTR CTR VITA 1 VITA 2 2 EC’s Type II/E stored at +22°C in CTA for 3 days (tbc) Activator unit Activator unit Activator unit Chemicals used inside the plunger boxes and Type II/E containers: 1) Activation: αMEM medium + 10% FCS 2) Medium exchange: αMEM medium + 10% FCS + 1,25- dihydroxyvitamin D3 10-8 M 3) Termination: Buffer (hypotonic) 1 = Crew activity

11. insight in the effects of spaceflight on osteoblast function better prevention of bone loss in astronauts insight in fundamental process of normal (cell) physiology: mechanisms by which bone responds to mechanical (un)loading influence treatment of other etiologies of osteoporosis Benefits