An Investigation of the Potential Mechanism of Curcumin to Regulate Osteogenic Differentiation of Bone Marrow-Derived Mesenchymal Stem Cells through Wnt/-Catenin Signaling Pathway Based on Network Pharmacology and Experimental Validation

Background: Osteoporosis (OP) is a common disease in the elderly, which can easily lead to fractures. Curcumin can promote osteogenic differentiation to treat OP by regulating certain genes. The expression of related genes in the Wnt/beta-catenin pathway is of great significance for osteogenic differentiation. However, the mechanism by which Curcumin regulates genes related to Wnt/beta-catenin pathway has not been clarified.Methodology: The target genes of Curcumin that regulate osteogenic differentiation were determined using network pharmacol-ogy, Protein-Protein Interaction (PPI), Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and molecular docking. The toxicity of Curcumin was studied by Methyl Thiazolyl Tetrazolium (MTT) assay and cell cloning. The macroscopic regulation of Curcumin on osteogenic differentiation was further investigated by alkaline phosphatase (ALP) staining and ac-tivity assay, alizarin red staining and quantification. The microscopic expression differences of Wnt/beta-catenin pathway-related mRNA and protein were detected by RT-qPCR and Western Blot. Results: A total of 92 target genes were screened for Curcumin-regulated osteogenic differentiation. Among them, three target genes act on the Wnt/beta-catenin signaling pathway. In addition, low concentrations of Curcumin (5 mu M, 10 mu M) were not toxic to the proliferation of rat bone marrow mesenchymal stem cells (rBMSCs) and enhanced ALP activity (p < 0.001), increased calcium salt deposition (p < 0.01), upregulated mRNA expression of catenin beta 1 (beta-catenin), CREB-binding protein (Cbp), Protein kinase A (Pka), Lymphoid Enhancer-binding Factor 1 (Lef-1), Runt-related transcription factor 2 (Runx2), Myc proto-oncogene protein (C-myc) and Cyclin D1 (p < 0.05), downregulated the expression of glycogen synthase kinase-3 beta (Gsk-3 beta) (p < 0.05), upregulated the protein expressions of CBP, PKA, LEF-1, Runx2, c-myc, Cyclin D1 and beta-catenin in the nucleus (p < 0.05), and downregulated the expression of GSK-3 beta (p < 0.05), thus boosting osteogenesis. By contrast, 15 mu M Curcumin inhibited ALP activity (p < 0.05), downregulated the mRNA expression of beta-catenin and Cbp (p < 0.05), upregulated mRNA expression of Gsk-3 beta (p < 0.05) and downregulated the protein expression of c-myc and Runx2 (p < 0.05), thereby inhibiting the osteogenic differentiation of rBMSCs. Conclusions: Curcumin at 5 mu M and 10 mu M can promote the osteogenic differentiation of rBMSCs by activating the Wnt/beta- catenin signaling pathway. Curcumin at 15 mu M can inhibit the Wnt/beta-catenin signaling pathway, thereby inhibiting the osteogenic differentiation of rBMSCs.