The Role of Insulin-Like Growth Factor-2 on the Cellular Viability and Differentiation to the Osteogenic Lineage and Mineralization of Stem Cells Cultured on Deproteinized Bovine Bone Mineral

Abstract

Insulin-like growth factors (IGFs) plays various roles, including differentiation and mitogenesis, and IGFs are reported to regulate the bone growth and maintenance. This study was performed to analyze the enhancing effects of IGF-2 on osteogenic differentiation and the mineralization of stem cells cultured on deproteinized bovine bone mineral. Stem cell loaded bone graft material was cultured in the presence of the IGF-2 at final concentrations of 10 and 100 ng/mL and the morphology of the cells was observed on Days 1, 3, and 7. The commercially available, two-color assay based on plasma membrane integrity and esterase activity was also used for qualitative analyses on Days 1, 3, and 7. The level of alkaline phosphatase activity and anthraquinone dye assay were used to evaluate osteogenic differentiation on Days 7 and 14. Real-time polymerase chain reaction was applied in order to identify the mRNA expression of BGLAP, Runx2, and β-catenin. The stem cells were well-attached with fibroblast morphology and most of the stem cells produced a high intensity of green fluorescence, indicating that there were live cells on Day 1. The relative cellular viability assay values for IGF-2 groups at 0, 10, and 100 ng/mL on Day 1 were 0.419 ± 0.015, 0.427 ± 0.013, and 0.500 ± 0.030, respectively (p < 0.05). The absorbance values at 405 nm for alkaline phosphatase activity on Day 7 for IGF-2 at 0, 10, and 100 ng/mL were 2.112 ± 0.152, 1.897 ± 0.144, and 2.067 ± 0.128, respectively (p > 0.05). The mineralization assay results at Day 7 showed significantly higher values for IGF-2 groups at 10 and 100 ng/mL concentration when compared to the control (p < 0.05). The application of IGF-2 groups of 10 and 100 ng/mL produced a significant increase of BGLAP. Conclusively, this study indicates that the use of IGF-2 on stem cell loaded bone graft increased cellular viability, Alizarin red staining, and BGLAP expression of stem cells. This report suggests the combined approach of stem cells and IGF-2 with scaffold may have synergistic effects on osteogenesis.