Despite an intensive research effort, very little is known about the cellular mechanism underlying osteoarthritis. As the aged population continues to increase, the number of individuals afflicted with arthritis will increase emphasizing the critical need for insights into the pathophysiology of this costly disease. The investigators believe that a better understanding of biophysical signal transduction in chondrocytes is a critical first step in understanding osteoarthritis. They propose to characterize mechano-chemical signal transduction, in response to fluid flow, in chondrocytes isolated from bovine articular cartilage. Their central hypothesis is that biophysical signal transduction in chondrocytes is at least partly defined by stretch activated (SA) channels which activate cytosolic Ca2+ mobilization. Their long term goals are to characterize fluid flow effects on cytosolic Ca2+ and proteoglycan synthesis and the role SA channels play in linking these two responses. These goals will be accomplished through the completion of four specific aims. 1) Quantify, in real time, the cytosolic Ca2+ concentration of bone articular chondrocytes (BAC) exposed to steady and oscillatory fluid flow; 2) Examine membrane stretch-induced channel activity BAC; 3) Quantify [Ca2+]i in BAC exposed to fluid flow in the presence and absence of factors which regulate specific signalling pathways; and 4) Quantify aggrecan mRNA and proteoglycan synthesis in BAC exposed fluid flow. BAC will be isolated and used after only subculture. Type II collagen expression will be monitored with indirect immunofluorescence and type I and II collagen mRNA by nuclease protection assays. Fluid flow effects on [Ca2+]i will be quantified by microspectrofluometry. SA channel function and expression will be quantified by patch clamp electrophysiology and nuclease protection assays, respectively. Aggrecan mRNA expression and proteoglycan synthesis, in response to fluid flow, will be quantified by nuclease protection assays and 35S-sulfate incorporation. These experiments will be repeated in the presence of specific inhibitors of fluid flow-induced cytosolic CA2+ mobilization. The results of this project will provide insights into the mechanism by which biophysical signals regulate chondrocyte metabolism.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
5R01AG015107-03
Application #
6137065
Study Section
Special Emphasis Panel (ZRG4-GRM (04))
Program Officer
Tyree, Bernadette
Project Start
1998-01-01
Project End
2000-12-31
Budget Start
2000-01-15
Budget End
2000-12-31
Support Year
3
Fiscal Year
2000
Total Cost
$196,683
Indirect Cost
Name
Pennsylvania State University
Department
Orthopedics
Type
Schools of Medicine
DUNS #
129348186
City
Hershey
State
PA
Country
United States
Zip Code
17033
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Sharma, Ritu; Yellowley, Clare E; Civelek, Mete et al. (2002) Intracellular calcium changes in rat aortic smooth muscle cells in response to fluid flow. Ann Biomed Eng 30:371-8
Yellowley, Clare E; Hancox, Jules C; Donahue, Henry J (2002) Effects of cell swelling on intracellular calcium and membrane currents in bovine articular chondrocytes. J Cell Biochem 86:290-301
Edlich, M; Yellowley, C E; Jacobs, C R et al. (2001) Oscillating fluid flow regulates cytosolic calcium concentration in bovine articular chondrocytes. J Biomech 34:59-65
Saunders, M M; You, J; Trosko, J E et al. (2001) Gap junctions and fluid flow response in MC3T3-E1 cells. Am J Physiol Cell Physiol 281:C1917-25
Yellowley, C E; Jacobs, C R; Donahue, H J (1999) Mechanisms contributing to fluid-flow-induced Ca2+ mobilization in articular chondrocytes. J Cell Physiol 180:402-8