Simulated microgravity using the Random Positioning Machine inhibits differentiation and alters gene expression profiles of 2T3 preosteoblasts

Exposure to microgravity causes bone loss in humans, and the underlying mechanism is thought to be at least partially due to a decrease in bone formation by osteoblasts. In the present study, we examined the hypothesis that microgravity changes osteoblast gene expression profiles, resulting in bone...

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Published inAmerican Journal of Physiology: Cell Physiology Vol. 57; no. 6; pp. C1211 - C1221
Main Authors PARDO, Steven J, PATEL, Mamta J, SYKES, Michelle C, PLATT, Manu O, BOYD, Nolan L, SORESCU, George P, MIN XU, VAN LOON, Jack J. W. A, WANG, May D, JO, Hanjoong
Format Journal Article
LanguageEnglish
Published Bethesda, MD American Physiological Society 01.06.2005
Subjects
Arrays
Biological and medical sciences
Bones
Cell culture
Cell differentiation, maturation, development, hematopoiesis
Cell physiology
Cellular biology
Fundamental and applied biological sciences. Psychology
Gene expression
Gravity
Inflammation
Molecular and cellular biology
Alkaline phosphatase
Enzyme
Phosphoric monoester hydrolases
Esterases
Gene expression
bone loss
Osteoarticular system
osteomodulin
microarray
runx2
Hydrolases
Bone
Differentiation
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Summary:Exposure to microgravity causes bone loss in humans, and the underlying mechanism is thought to be at least partially due to a decrease in bone formation by osteoblasts. In the present study, we examined the hypothesis that microgravity changes osteoblast gene expression profiles, resulting in bone loss. For this study, we developed an in vitro system that simulates microgravity using the Random Positioning Machine (RPM) to study the effects of microgravity on 2T3 preosteoblast cells grown in gas-permeable culture disks. Exposure of 2T3 cells to simulated microgravity using the RPM for up to 9 days significantly inhibited alkaline phosphatase activity, recapitulating a bone loss response that occurs in real microgravity conditions without altering cell proliferation and shape. Next, we performed DNA microarray analysis to determine the gene expression profile of 2T3 cells exposed to 3 days of simulated microgravity. Among 10,000 genes examined using the microarray, 88 were downregulated and 52 were upregulated significantly more than twofold using simulated microgravity compared with the static 1-g condition. We then verified the microarray data for some of the genes relevant in bone biology using real-time PCR assays and immunoblotting. We confirmed that microgravity downregulated levels of alkaline phosphatase, runt-related transcription factor 2, osteomodulin, and parathyroid hormone receptor 1 mRNA; upregulated cathepsin K mRNA; and did not significantly affect bone morphogenic protein 4 and cystatin C protein levels. The identification of gravisensitive genes provides useful insight that may lead to further hypotheses regarding their roles in not only microgravity-induced bone loss but also the general patient population with similar pathological conditions, such as osteoporosis. [PUBLICATION ABSTRACT]
ISSN:0363-6143
1522-1563