Epidermal growth factor receptor promotes osteoclast differentiation probably through regulating ABCC1 and CDC37

Objective To observe the expression profile of epidermal growth factor receptor (EGFR) during the differentiation of osteoclasts, and to explore EGFR-related signaling pathways and key genes during the process. Methods Bone marrow derived macrophages were extracted from 24 healthy SPF-grade male C57BL/6 mice (6-8 weeks old, weighing 19~21 g), and then treated with M-CSF and RANKL co-stimulation to establish a model of mouse osteoclast differentiation. TRAP staining and RT-qPCR were used to detect the differentiation status of osteoclasts and the expression level of EGFR. Bioinformatics were employed to systematically identify EGFR-related genes during osteoclast differentiation, and then RT-qPCR and EGFR activation and inhibition models were applied to validate the genes. Results In vitro osteoclast differentiation model showed the EGFR expression level was in a continuous increase during the differentiation of mouse osteoclasts (P < 0.01). RNA-seq data indicated that EGFR expression was significantly associated with multiple signaling pathways, including MAPK pathway (P < 0.05). Weighted correlation network analysis (WGCNA) and protein-protein interaction (PPI) analysis identified co-expression and correlations of EGFR with ATP binding cassette subfamily C member 1 (ABCC1) and cell division cycle 37 (CDC37) (P < 0.01). The osteoclast differentiation model showed significant increases in the expression levels of ABCC1 (P < 0.05) and CDC37 (P < 0.01) during differentiation, and activation of EGFR further enhanced the levels (P < 0.01) while EGFR inhibition decreased them (P < 0.05). Conclusion Activation of EGFR signal induces osteoclast differentiation and up-regulates the expression levels of ABCC1 and CDC37.