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A novel osteoblast-derived C-type lectin that inhibits osteoclast formation
H Zhou1, V Kartsogiannis, Y S Hu
1Department of Medicine, University of Melbourne, St. Vincent's Hospital, and St. Vincent's Institute of Medical Research, Fitzroy, Victoria 3065, Australia.
Abstract:
We have cloned and expressed murine osteoclast inhibitory lectin (mOCIL), a 207-amino acid type II transmembrane C-type lectin. In osteoclast formation assays of primary murine calvarial osteoblasts with bone marrow cells, antisense oligonucleotides for mOCIL increased tartrate-resistant acid phosphatase-positive mononucleate cell formation by 3-5-fold, whereas control oligonucleotides had no effect. The extracellular domain of mOCIL, expressed as a recombinant protein in Escherichia coli, dose-dependently inhibited multinucleate osteoclast formation in murine osteoblast and spleen cell co-cultures as well as in spleen cell cultures treated with RANKL and macrophage colony-stimulating factor. Furthermore, mOCIL acted directly on macrophage/monocyte cells as evidenced by its inhibitory action on adherent spleen cell cultures, which were depleted of stromal and lymphocytic cells. mOCIL completely inhibited osteoclast formation during the proliferative phase of osteoclast formation and resulted in 70% inhibition during the differentiation phase. Osteoblast OCIL mRNA expression was enhanced by parathyroid hormone, calcitriol, interleukin-1alpha and -11, and retinoic acid. In rodent tissues, Northern blotting, in situ hybridization, and immunohistochemistry demonstrated OCIL expression in osteoblasts and chondrocytes as well as in a variety of extraskeletal tissues. The overlapping tissue distribution of OCIL mRNA and protein with that of RANKL strongly suggests an interaction between these molecules in the skeleton and in extraskeletal tissues.
Insights
Murine osteoclast inhibitory lectin (mOCIL) inhibits osteoclast formation by acting directly on monocytes. mOCIL plays a key role in skeletal and extraskeletal tissues, suggesting interactions with RANKL.
Area of Science:
- Biochemistry
- Cell Biology
- Immunology
Background:
- Osteoclast formation is crucial for bone remodeling and is regulated by various factors.
- C-type lectins are involved in cell-cell recognition and signaling pathways.
- Murine osteoclast inhibitory lectin (mOCIL) is a type II transmembrane C-type lectin with potential roles in bone biology.
Purpose of the Study:
- To investigate the role of mOCIL in osteoclast formation.
- To characterize the function and expression of mOCIL.
- To explore the potential interaction of mOCIL with RANKL.
Main Methods:
- Cloning and expression of mOCIL.
- Osteoclast formation assays using primary murine cells and recombinant mOCIL.
- Antisense oligonucleotide treatment to inhibit mOCIL expression.
- Northern blotting, in situ hybridization, and immunohistochemistry for tissue distribution analysis.
Main Results:
- Antisense oligonucleotides against mOCIL significantly increased osteoclast formation.
- Recombinant mOCIL dose-dependently inhibited multinucleated osteoclast formation.
- mOCIL directly inhibited osteoclastogenesis in macrophage/monocyte cultures.
- mOCIL expression was regulated by hormones and cytokines, and found in various tissues, overlapping with RANKL distribution.
Conclusions:
- mOCIL is a potent inhibitor of osteoclast formation, acting directly on monocytes/macrophages.
- mOCIL plays a significant role in both skeletal and extraskeletal tissues.
- The overlapping expression with RANKL suggests a potential functional interaction in regulating bone metabolism and other physiological processes.