Treatment of osteopenic disorders has relied, to-date, on anti-resorptive drugs such as estrogens and bisphosphonates. While these agents often retard progressive bone loss, they are not effective in reversing the established osteoporotic lesion, nor are they typically capable of curing patients already afflicted with the disease. The dramatic effect of parathyroid hormone as a potential clinical bone anabolic drug underscores the hypothesis that substantial enhancement of skeletal mass requires stimulation of bone formation. Thus, identification of molecules, which promote systemic osteogenesis, is a major focus of anti-osteoporosis research. We have made the surprising observation that the key osteoclastogenic cytokine, RANK ligand (RANKL), when administered subcutaneously as a GST-fusion protein, is a potent bone anabolic agent. This compound dramatically enhances osteoblastogenesis and, within one week, stimulates exuberant bone formation, as detected radiographically, histologically and densitometrically. Importantly, GST-RANKL, at doses inducing as much as a 25-fold increase in osteoblast (OB) number, does not promote osteoclastogenesis in vivo. We also have established that OBs, and their precursors, are direct targets of GST-RANKL and have shown that collagen type I synthesis, by these cells, is greatly accelerated when they are exposed to the fusion protein. These data position GST-RANKL, or its derivatives, as potential bone anabolic, anti-osteoporosis agents. We therefore hypothesize that (1) GST-RANKL enhances OBs function by distinct signal pathways; (2) GST-RANKL, transcriptionally and/or post-transcriptionally, induces collagen type I synthesis by OBs; and (3) GST-RANKL prevents and/or reverses osteoporosis.
Our Specific Aims are therefore to: (1) identify the signal pathways by which GST-RANKL enhances OB function; (2) identify the mechanism by which GST-RANKL induces collagen type I synthesis by OBs; and (3) determine if GST-RANKL prevents and/or reverses osteoporosis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
1R01AR048853-01
Application #
6508327
Study Section
Orthopedics and Musculoskeletal Study Section (ORTH)
Program Officer
Sharrock, William J
Project Start
2002-08-01
Project End
2003-07-31
Budget Start
2002-08-01
Budget End
2003-07-31
Support Year
1
Fiscal Year
2002
Total Cost
$349,093
Indirect Cost
Name
Barnes-Jewish Hospital
Department
Type
DUNS #
City
Saint Louis
State
MO
Country
United States
Zip Code
63110
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