Work

Roles of stromal cell RANKL, OPG, and M‐CSF expression in biphasic TGF‐β regulation of osteoclast differentiation

Year: 2004

Type: article

Abstract: To better understand the complex roles of transforming growth factor-beta (TGF-beta) in bone metabolism, we examined the impact of a range of TGF-beta concentrations on osteoclast differentiation. In co-cultures of support cells and spleen or marrow osteoclast precursors, low TGF-beta concentrations stimulated while high concentrations inhibited differentiation. We investigated the influences of TGF-beta on macrophage colony stimulating factor (M-CSF), receptor activator of NF-kappaB ligand (RANKL), and osteoprotegerin (OPG) expression and found a dose dependent inhibition of M-CSF expression. RANKL expression was elevated at low TGF-beta concentrations with a less dramatic increase in OPG. Addition of OPG blocked differentiation at the stimulatory TGF-beta dose. Thus, low TGF-beta concentrations elevated the RANKL/OPG ratio while high concentrations did not, supporting that, at low TGF-beta concentrations, there is sufficient M-CSF and a high RANKL/OPG ratio to stimulate differentiation. At high TGF-beta concentrations, the RANKL/OPG ratio and M-CSF expression were both repressed and there was no differentiation. We examined whether TGF-beta-mediated repression of osteoclasts differentiation is due to these changes by adding M-CSF and/or RANKL and did not observe any impact on differentiation repression. We studied direct TGF-beta impacts on osteoclast precursors by culturing spleen or marrow cells with M-CSF and RANKL. TGF-beta treatment dose-dependently stimulated osteoclast differentiation. These data indicate that low TGF-beta levels stimulate osteoclast differentiation by impacting the RANKL/OPG ratio while high TGF-beta levels repress osteoclast differentiation by multiple avenues including mechanisms independent of the RANKL/OPG ratio or M-CSF expression regulation.

Source: Journal of Cellular Physiology

DOI: 10.1002/jcp.20036

Authors: Mary Karst, Genevieve Gorny, Rachelle J. Sells Galvin, Merry Jo Oursler

Institutions: University of Minnesota, Duluth, Eli Lilly (United States), Mayo Clinic

Language: English

Topic: Bone Metabolism and Diseases

Subfield: Molecular Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

SDG: Good health and well-being

Open Access status: green

Funder: National Institute of Dental and Craniofacial Research