Mechano-Growth Factor E Peptide Inhibits The Differentiation And Mineralization Of Osteoblasts

Objective: To investigate the effects of mechano-growth factor E (MGF-E) peptide derived from an IGF-1 isoform on the differentiation and mineralization of osteoblasts.Methods: mGF-E peptide corresponding to the carboxy terminal 24 amino acid peptide of human MGF was synthesized. MGF-E (1 nM) peptide was then used to treat the pre-osteoblast line MC3T3-E1. At predetermined times, alkaline phosphatase (ALP) activity was quantified using an enzyme activity assay kit. The expression levels of collagen I (Col I) and osteopontin (OPN), and core binding factor 1 (Cbf alpha-1) were detected by reverse transcription polymerase chain reaction and Western blot analysis. The effect of MGF-E on mineralization was determined by Alizarin Red staining and calcium concentration analysis. The kinase inhibitor PD98059 was used to investigate Erk pathway involvement in the MGF-E role.Results: In the MGF-E-treated osteoblasts, ALP activity decreased with increased Erk activation. The transcription and translation of Col I were inhibited, but those of OPN were enhanced. PD98059 abolished the inhibitory effect and increased the expression of Coil, but decreased that of OPN. Treatment with MGF-E alone up-regulated the mRNA and total protein levels of Cbf alpha-1, but decreased the fraction of activated Cbf alpha-1 in the nucleus. Mineralization was delayed by MGF-E, as shown by the bone nodule staining and calcium concentration analysis. These delayed actions were weakened after treatment with PD98059.Conclusions: MGF-E could inhibit osteoblast differentiation and mineralization. The possible mechanisms are increased Erk activity and decreased Cbf alpha-1 nuclear translocation. (C) 2011 Elsevier Ltd. All rights reserved.