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Centrifugation of Cultured Osteoblasts And Macrophages as a Model To Study How Gravity Regulates The Function of Skeletal CellsMechanical loading helps define the architecture of weight-bearing bone via the tightly regulated process of skeletal turnover. Turnover occurs by the concerted activity of osteoblasts, responsible for bone formation. and osteoclasts, responsible for bone resorption. Osteoclasts are specialized megakaryon macrophages, which differentiate from monocytes in response to resorption stimuli, such as reduced weight-bearing. Habitation in space dramatically alters musculoskeletal loading, which modulates both cell function and bone structure. Our long-term objective is to define the molecular and cellular mechanisms that mediate skeletal adaptations to altered gravity environments. Our experimental approach is to apply hypergravity loads by centrifugation to rodents and cultured cells. As a first step, we examined the influence of centrifugation on the structure of cancellous bone in rats to test the ability of hypergravity to change skeletal architecture. Since cancellous bone undergoes rapid turnover we expected the most dramatic structural changes to occur in the shape of trabeculae of weight-bearing, cancellous bone. To define the cellular responses to hypergravity loads, we exposed cultured osteoblasts and macrophages to centrifugation. The intraosseous and intramedullary pressures within long bones in vivo reportedly range from 12-40 mm Hg, which would correspond to 18-59 gravity (g) in our cultures. We assumed that hydrostatic pressure from the medium above the cell layer is at least one major component of the mechanical load generated by centrifuging cultured cells. and therefore we exposed the cells to 10-50g. In osteoblasts, we examined the structure of their actin and microtubule networks, production of prostaglandin E2 (PGE2), and cell survival. Analysis of the shape of the cytoskeletal networks provides evidence for the ability of centrifugation to affect cell structure, while the production of PGE2 serves as a convenient marker for mechanical stimulation. We examined cell survival, reasoning that osteoblasts might mold skeletal structure in a hypergravity environment in part by regulating apoptosis and thus the duration of osteoblast productivity. Finally, we tested the influence of centrifugation on microbial activation of a macrophage cell line (RAW264.7). In response to the appropriate hormonal stimulation, this cell line is reportedly capable of undergoing differentiation to express osteoclast markers. In addition, a component of the cell wall of gram-negative bacteria, lipopolysaccaride (LPS), stimulates the formation of osteoclasts in vivo. Thus we tested the influence on centrifugation on RAW264.7 cells stimulated with LPS to provide an index of the function of osteoclast precursors.
Document ID
20010084719
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Globus, Ruth K.
(NASA Ames Research Center Moffett Field, CA United States)
Searby, Nancy D.
(NASA Ames Research Center Moffett Field, CA United States)
Almeida, Eduardo A. C.
(California Univ. San Francisco, CA United States)
Sutijono, Darrell
(NASA Ames Research Center Moffett Field, CA United States)
Yu, Joon-Ho
(NASA Ames Research Center Moffett Field, CA United States)
Malouvier, Alexander
(NASA Ames Research Center Moffett Field, CA United States)
Doty, Steven B.
(Hospital for Special Surgery United States)
Morey-Holton, Emily
(NASA Ames Research Center Moffett Field, CA United States)
Weinstein, Steven L.
(San Francisco State Univ. CA United States)
Dalton, Bonnie P.
Date Acquired
August 20, 2013
Publication Date
December 29, 2000
Subject Category
Life Sciences (General)
Meeting Information
Meeting: Future of Chronic Acceleration
Location: Davis, CA
Country: United States
Start Date: January 28, 2001
End Date: January 31, 2001
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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