CD109 Plays a Role in Osteoclastogenesis

Abstract

Osteoclasts are large multinucleated cells that arise from the fusion of cells from the monocyte/macrophage lineage. Osteoclastogenesis is mediated by macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-kB ligand (RANKL) and involves a complex multistep process that requires numerous other elements, many of which remain undefined. The primary aim of this project was to identify novel factors which regulate osteoclastogenesis. To carry out this investigation, microarray analysis was performed comparing two pre-osteoclast cell lines generated from RAW264.7 macrophages: one that has the capacity to fuse forming large multinucleated cells and one that does not fuse. It was found that CD109 was up-regulated by>17-fold in the osteoclast forming cell line when compared to the cell line that does not fuse, at day 2 of the differentiation process. Results obtained with microarray were confirmed by RT-qPCR and Western blot analyses in the two cell lines, in the parental RAW264.7 cell line, as well as primary murine monocytes from bone marrow. A significant increase of CD109 mRNA and protein expression during osteoclastogenesis occurred in all tested cell types. In order to characterize the role of CD109 in osteoclastogenesis, CD109 stable knockdown cell lines were established and fusion of osteoclast precursors into osteoclasts was assessed. It was found that CD109 knockdown cell lines were less capable of forming large multinucleated osteoclasts. It has been shown here that CD109 is expressed in monocytes undergoing RANKL-induced osteoclastogenesis. Moreover, when CD109 expression is suppressed in vitro, osteoclast formation decreases. This suggests that CD109 might be an important regulator of osteoclastogenesis. Further research is needed in order to characterize the role played by CD109 in regulation of osteoclast differentiation.

CD109 deficiency induces osteopenia with an osteoporosis‐like phenotype in vivo

“…Additionally, dynamic histomorphometric analysis showed enhanced bone formation in CD109 −/− mice. Additionally, we unexpectedly found that osteoclasts in CD109 −/− bones were large, multinucleated cells that seemingly matured in vivo; this is in contrast to a previous report that osteoclast formation decreases in RAW264.7 cells in vitro when CD109 is suppressed (Wang et al, 2013). This difference in p-values between ES/BS and OV/BV might suggest that bone erosion exceeds osteoid formation in CD109 −/− mice.…”

“…vitro decreased following CD109 suppression (Wang et al, 2013). We also carried out an osteoclast formation assay, as described in the Supporting Information Appendix S1, and observed reduced osteoclast formation in vitro in primary monocytes from bone marrow of CD109 −/− mice compared with those from CD109 +/+ bone marrow (Figure 3c).…”

Identification, molecular characterization, and gene expression analysis of a CD109 molecule in the Hawaiian bobtail squid Euprymna scolopes

“…It is thought that direct and indirect disturbances in TGF-b signaling may be implicated in the pathologies that associate CD109 with diseased growths [82]. In addition, CD109 has been implicated in the signaling pathway involved in differentiation of osteoclasts from progenitor cell lines [83].…”

CD109 is a potential target for triple-negative breast cancer

“…Thus, CD109 regulates TGF-β receptor endocytosis and degradation to inhibit TGF-β signaling. Some studies have shown that human cells overexpressing CD109 exhibit enhanced proliferation compared with control cells, so this molecule is known to be involved in tumorigenesis [15,16].…”