Gene expression profiles and bioinformatics analysis of insulin‐like growth factor‐1 promotion of osteogenic differentiation

Abstract

BackgroundInsulin‐like growth factor‐1 (IGF‐1) promotes osteoblast differentiation and mineralization. The objective of this study was to investigate the effects of IGF‐1 on proliferation, mineralization, alkaline phosphatase (ALP) synthesis, and gene expression of osteoblast differentiation in MC3T3‐E1 osteoblasts cells, and to explore gene expression profiling differential genes.MethodsMC3T3‐E1 osteoblasts cells were cultured in medium with or without IGF‐1. The ALP assay was employed to determine the osteoblast mineralization, and Alizarin red S to stain for calcium deposits, which were the indicators of mature osteocytes. The living cell number was assessed by the Cell Counting Kit‐8 method. RNA‐seq analysis was applied to identify genes that were differentially expressed in with or without IGF‐1 as well as genes that varied between these two groups. The expression of osteogenic marker genes was determined by quantitative real‐time polymerase chain reaction (qRT‐PCR) and western blot analysis.ResultThe cell number of osteoblasts exposed to IGF‐1 at 200 μg/L significantly increased compared with the control group. The ALP activity in IGF‐1‐treated cells was higher than that in the control group. IGF‐1 can increase ALP synthesis in osteoblasts in vitro. RNA‐seq analysis showed that 677 triggered differentially expressed genes by IGF, of which 383 genes were downregulated and 294 genes were upregulated. Gene ontology (GO) analysis showed that IGF‐1 caused a significant change in gene expression patterns.ConclusionsThis result suggested that IGF‐1 could probably promote the synthesis of organic matrix and mineralize action of bone. Osteogenic‐related genes (DMP1, PHEX, SOST, BMP2, RUNX2, OPN, and OCN) were significantly upregulated both in GO analysis and in pathway analysis to perform qRT‐PCR. Western blot analysis demonstrated that the Notch pathway was highly upregulated in MC3T3‐E1 cells.