Both parathyroid hormone (PTH) and mechanical stimulation (MS) have been shown to stimulate net bone formation, in vivo. An early response to both stimuli in cultured osteoblasts is a rapid increase in intracellular Ca2+ ([Ca2+]i) that is mediated by both extracellular Ca2+ entry and intracellular Ca2+ release (iCaR). In this proposal, the principal investigator postulates that PTH lowers the mechanical threshold of osteoblasts by altering the mechanisms involved in modulating [Ca2+]i, thereby promoting net bone formation at more physiologic levels of MS. PTH and MS activate a number of responses in osteoblasts capable of mediating this rise in [Ca2+]i, including mechanosensitive, cation-selective channels (MSCC), IP3-induced iCaR and actin cytoskeletal rearrangement, that could act as sites of convergence for these stimuli. Here, the principal investigator proposes to examine the complex interactions of these responses on [Ca2+]i, and the role they play in gene expression and signal amplification in osteoblasts in response to fluid shear and PTH treatment. In this proposal, the principal investigator will use cell biologic, immunofluorescent staining, patch clamp and [Ca2+]i imaging techniques to examine the interaction of fluid shear and PTH stimulation on [Ca2+]i, expression and production of anabolic markers and paracrine release in osteoblasts. He will focus these studies on channel production and function and iCaR in relation to cellular differentiation and cytoskeletal reorganization.
The aims of this proposal are to: (1) determine the interaction of PTH and fluid shear on the expression and production of anabolic markers and paracrine factors associated with bone formation and assess the role of the [Ca2+]i increase in these responses; (2) examine the function of MSCC and Ca2+ channels and iCaR in the [Ca2+]i response to fluid shear and PTH as a function of the differentiated state of the cell; and (3) examine the role of the cytoskeleton in activation and """"""""priming"""""""" of channels subjected to PTH and fluid forces. These studies are intended to provide new insight into the mechanisms of transduction of the biophysical signal into osteoblastic function and methods to change this response.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK058246-04
Application #
6617926
Study Section
Orthopedics and Musculoskeletal Study Section (ORTH)
Program Officer
Malozowski, Saul N
Project Start
2000-08-15
Project End
2005-03-31
Budget Start
2003-08-01
Budget End
2005-03-31
Support Year
4
Fiscal Year
2003
Total Cost
$223,500
Indirect Cost
Name
Indiana University-Purdue University at Indianapolis
Department
Orthopedics
Type
Schools of Medicine
DUNS #
603007902
City
Indianapolis
State
IN
Country
United States
Zip Code
46202
Gardinier, Joseph; Yang, Weidong; Madden, Gregory R et al. (2014) P2Y2 receptors regulate osteoblast mechanosensitivity during fluid flow. Am J Physiol Cell Physiol 306:C1058-67
Gong, Xiaoyuan; Yang, Weidong; Wang, Liyun et al. (2014) Prostaglandin E2 modulates F-actin stress fiber in FSS-stimulated MC3T3-E1 cells in a PKA-dependent manner. Acta Biochim Biophys Sin (Shanghai) 46:40-7
Li, J; Zhao, L; Ferries, I K et al. (2010) Skeletal phenotype of mice with a null mutation in Cav 1.3 L-type calcium channel. J Musculoskelet Neuronal Interact 10:180-7
Shao, Ying; Czymmek, Kirk J; Jones, Patricia A et al. (2009) Dynamic interactions between L-type voltage-sensitive calcium channel Cav1.2 subunits and ahnak in osteoblastic cells. Am J Physiol Cell Physiol 296:C1067-78
Zhang, Jinsong; Ryder, Kimberly D; Bethel, Jody A et al. (2006) PTH-induced actin depolymerization increases mechanosensitive channel activity to enhance mechanically stimulated Ca2+ signaling in osteoblasts. J Bone Miner Res 21:1729-37
Li, Jiliang; Duncan, Randall L; Burr, David B et al. (2003) Parathyroid hormone enhances mechanically induced bone formation, possibly involving L-type voltage-sensitive calcium channels. Endocrinology 144:1226-33
Ryder, K D; Duncan, R L (2001) Parathyroid hormone enhances fluid shear-induced [Ca2+]i signaling in osteoblastic cells through activation of mechanosensitive and voltage-sensitive Ca2+ channels. J Bone Miner Res 16:240-8