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-1␣ 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.

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The hOCIL gene is 25 kb in length, comprised of five exons, and is a member of a superfamily of natural killer (NK) cell receptors encoded by the NK gene complex located on chromosome 12. Human OCIL mRNA expression is upregulated by interleukin (IL)-1alpha and prostaglandin E2 (PGE2) in a time-dependent manner in human osteogenic sarcoma MG63 cells, but not by dexamethasone or 1,25 dihydroxyvitamin D3. Soluble recombinant hOCIL had biological effects comparable with recombinant mOCIL on human and murine osteoclastogenesis. In addition to its capacity to limit osteoclast formation, OCIL was also able to inhibit bone resorption by mature, giant-cell tumor-derived osteoclasts. Thus, a human homolog of OCIL exists that is highly conserved with mOCIL in its primary amino acid sequence (C-lectin domain), genomic structure, and activity to inhibit osteoclastogenesis.

increasing research has demonstrated that expression of brain and muscle arnT-like 1 (BMal1) and other circadian clock genes can be regulated by drugs and toxicants. We previously demonstrated that icariin, extracted from Herba epimedii, sromotes osteogenic differentiation. However, the mechanism underlying the association between icariin and BMal1 in osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMScs) remains unclear. The present study was designed with an aim to clarify the association between icariin and BMal1 in osteogenic differentiation of BMScs. The cell counting Kit-8 assay was used to evaluate cell proliferation. The expression of bone morphogenetic protein 2 (BMP2), runX family transcription factor 2 (runX2), alkaline phosphatase (alP), osteocalcin (oc) and BMal1 in BMScs was evaluated by reverse transcription-quantitative Pcr and western blotting. alP and alizarin red S (arS) staining were also performed. icariin promoted BMSc proliferation, and upregulated expression of osteogenic genes and BMal1. in addition, expression of the osteogenic genes BMP2, runX2, alP and oc were upregulated by BMal1 overexpression. Furthermore, we confirmed that BMal1 deficiency suppressed osteogenic differentiation in BMScs. Finally, arS staining of BMal1 -/-BMScs revealed that BMal1 was an essential intermediary in matrix mineralization during osteogenic differentiation. in conclusion, these results demonstrated that icariin promoted osteogenic differentiation through BMal1-BMP2 signaling in BMScs. The present study thus described a novel target of icariin that has potential applications in the treatment of osteogenic disorders.