The Effects of Bone Morphogenetic Protein-4 on Cellular Viability, Osteogenic Potential, and Global Gene Expression on Gingiva-Derived Stem Cell Spheroids

Abstract

Bone morphogenetic protein-4 (BMP-4) is engaged in the migration ability of mesenchymal stem cells and the transition of mesenchymal stem cells into osteogenic and adipocytic lines. The aim of this study was to evaluate the effects of BMP-4 on the cellular viability, osteogenic differentiation, and genome-wide mRNA levels using three-dimensional cell spheroids composed of stem cells. Stem cell spheroids were formed using concave microwells in the presence of BMP-4 with final concentrations of 0, 2, 6, and 10 ng/mL. Cellular viability was measured qualitatively using a microscope and quantitatively using an assay kit based on water-soluble tetrazolium salt. Osteogenic differentiation was assessed by measuring the level of alkaline phosphatase activity. Global gene expression was assessed using next-generation mRNA sequencing and performing gene ontology and pathway analyses. Spheroids were well-maintained with the addition of BMP-4 up to Day 7. No significant differences were observed in cell viability between each group. There were significantly higher alkaline phosphatase values in the 2 ng/mL BMP-4 groups when compared with the control (p < 0.05). A total of 25,737 mRNAs were differentially expressed. Expression of β-catenin (CTNNB1) was increased with higher dosages of BMP-4. The expression of runt-related transcription factor 2 (RUNX2) was increased up to 6 ng/mL. The phosphoinositide-3-kinase–protein kinase B/Akt signaling pathway was associated with the target genes. This study demonstrates that the application of BMP-4 enhanced alkaline phosphatase activity and the expression of CTNNB1 and RUNX2 without affecting cellular viability.