Mechanical loading prevents the stimulating effect of IL-1β on osteocyte-modulated osteoclastogenesis

R.N. Kulkarni, A.D. Bakker, V. Everts, J. Klein-Nulend

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Inflammatory diseases such as rheumatoid arthritis are often accompanied by higher plasma and synovial fluid levels of interleukin-1β (IL-1β), and by increased bone resorption. Since osteocytes are known to regulate bone resorption in response to changes in mechanical stimuli, we investigated whether IL-1β affects osteocyte-modulated osteoclastogenesis in the presence or absence of mechanical loading of osteocytes.

MLO-Y4 osteocytes were pre-incubated with IL-1β (0.1-1 ng/ml) for 24 h. Cells were either or not subjected to mechanical loading by 1 h pulsating fluid flow (PFF; 0.7 ± 0.3 Pa, 5 Hz) in the presence of IL-1β (0.1-1 ng/ml). Conditioned medium was collected after 1 h PFF or static cultures. Subsequently mouse bone marrow cells were seeded on top of the IL-1β-treated osteocytes to determine osteoclastogenesis. Conditioned medium from mechanically loaded or static IL-1β-treated osteocytes was added to co-cultures of untreated osteocytes and mouse bone marrow cells. Gene expression of cysteine-rich protein 61 (CYR61/CCN1), receptor activator of nuclear factor kappa-B ligand (RANKL), and osteoprotegerin (OPG) by osteocytes was determined immediately after PFF.

Incubation of osteocytes with IL-1β, as well as conditioned medium from static IL-1β-treated osteocytes increased the formation of osteoclasts. However, conditioned medium from mechanically loaded IL-1β-treated osteocytes prevented osteoclast formation. Incubation with IL-1β upregulated RANKL and downregulated OPG gene expression by static osteocytes. PFF upregulated CYR61, RANKL, and OPG gene expression by osteocytes.

Our results suggest that IL-1β increases osteocyte-modulated osteoclastogenesis, and that mechanical loading of osteocytes may abolish IL-1β-induced osteoclastogenesis.
Original languageEnglish
Pages (from-to)11-16
JournalBiochemical and Biophysical Research Communications
Volume420
Issue number1
DOIs
Publication statusPublished - 2012

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