Mechano-growth factor E peptide inhibits the differentiation and mineralization of osteoblasts

Objective estigate the effects of mechano-growth factor E (MGF-E) peptide derived from an IGF-1 isoform on the differentiation and mineralization of osteoblasts. s 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 (Cbfα-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. s 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 Col I, but decreased that of OPN. Treatment with MGF-E alone up-regulated the mRNA and total protein levels of Cbfα-1, but decreased the fraction of activated Cbfα-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. sions could inhibit osteoblast differentiation and mineralization. The possible mechanisms are increased Erk activity and decreased Cbfα-1 nuclear translocation.