It is well known that mechanical loading increases formation and remodeling of bone. Bone mass is increased in response to exercise, while chronic unloading of bone, such as occurs during prolonged bed rest and in microgravity during space flight, results in atrophy of bone. The broad aim of our research is to understand the cellular and molecular mechanisms that regulate mechanically-induced bone formation. Experimental studies suggest that mechanically-induced bone formation may be stimulated by fluid shear stress (FSS)-induced activation of osteoblasts. Mechanical activation of osteoblasts is thought to result from the movement of interstitial fluid through the porous spaces inside bone that subjects osteoblasts to FSS during high impact loading. However, the cellular mechanisms through which FSS promotes an anabolic response in osteoblasts are not clearly understood. Interestingly, a large proportion of osteoblasts at sites of bone remodeling are destined to undergo programmed cell death (apoptosis). Therefore, processes that inhibit osteoblast apoptosis may be effective in increasing bone formation and improving bone strength in normal and disease states. Our preliminary studies indicate that mechanical stimulation of osteoblasts in vitro, by exposure to steady fluid shear stress, inhibits osteoblast apoptosis. Therefore, in this application we propose experiments that are designed to investigate the signaling mechanisms through which FSS promotes the survival of osteoblasts. We will: (1) determine the mechanisms through which FSS regulates intracellular signaling pathways involved in control of apoptosis, and (2) determine the role of temporal shear gradients in the anti-apoptotic response of osteoblasts to FSS. The long-term goal of this research is to identify strategies for improving bone health by better understanding the cellular and molecular mechanisms that regulate osteoblast survival. In this application, we propose to use an in vitro cell culture model to test the hypothesis that exposure of cells to either steady or pulsatile fluid shear stress regulates osteoblast survival through specific cellular processes, including activation of the PI3-kinase/Akt and MAPK signaling pathways and inhibition of caspase activation. We will use primary cultures of rat calvarial osteoblasts, and osteoblast cell lines, including MC3T3-E1 and UMR106.01 cells, to investigate the cellular mechanisms that regulate apoptosis. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR049728-05
Application #
7215632
Study Section
Orthopedics and Musculoskeletal Study Section (ORTH)
Program Officer
Sharrock, William J
Project Start
2003-04-01
Project End
2009-03-31
Budget Start
2007-04-01
Budget End
2009-03-31
Support Year
5
Fiscal Year
2007
Total Cost
$279,339
Indirect Cost
Name
Indiana University-Purdue University at Indianapolis
Department
Physiology
Type
Schools of Medicine
DUNS #
603007902
City
Indianapolis
State
IN
Country
United States
Zip Code
46202
Young, Suzanne R L; Hum, Julia M; Rodenberg, Eric et al. (2011) Non-overlapping functions for Pyk2 and FAK in osteoblasts during fluid shear stress-induced mechanotransduction. PLoS One 6:e16026
Bidwell, Joseph P; Pavalko, Fredrick M (2010) The Load-Bearing Mechanosome Revisited. Clin Rev Bone Miner Metab 8:213-223
Young, Suzanne R L; Gerard-O'Riley, Rita; Kim, Jae-Beom et al. (2009) Focal adhesion kinase is important for fluid shear stress-induced mechanotransduction in osteoblasts. J Bone Miner Res 24:411-24
Triplett, Jason W; O'Riley, Rita; Tekulve, Kristyn et al. (2007) Mechanical loading by fluid shear stress enhances IGF-1 receptor signaling in osteoblasts in a PKCzeta-dependent manner. Mol Cell Biomech 4:13-25
Ponik, Suzanne M; Triplett, Jason W; Pavalko, Fredrick M (2007) Osteoblasts and osteocytes respond differently to oscillatory and unidirectional fluid flow profiles. J Cell Biochem 100:794-807
Triplett, Jason W; Pavalko, Fredrick M (2006) Disruption of alpha-actinin-integrin interactions at focal adhesions renders osteoblasts susceptible to apoptosis. Am J Physiol Cell Physiol 291:C909-21
Triplett, Jason W; Herring, B Paul; Pavalko, Fredrick M (2005) Adenoviral transgene expression enhanced by cotreatment with etoposide in cultured cells. Biotechniques 39:826, 828, 830, passim
Norvell, S M; Alvarez, M; Bidwell, J P et al. (2004) Fluid shear stress induces beta-catenin signaling in osteoblasts. Calcif Tissue Int 75:396-404
Norvell, Suzanne M; Ponik, Suzanne M; Bowen, Deidre K et al. (2004) Fluid shear stress induction of COX-2 protein and prostaglandin release in cultured MC3T3-E1 osteoblasts does not require intact microfilaments or microtubules. J Appl Physiol 96:957-66
Ponik, Suzanne M; Pavalko, Fredrick M (2004) Formation of focal adhesions on fibronectin promotes fluid shear stress induction of COX-2 and PGE2 release in MC3T3-E1 osteoblasts. J Appl Physiol 97:135-42

Showing the most recent 10 out of 11 publications