Comparison of gene expression in osteoblasts from Polynesian and Caucasian patients

Abstract

Current evidence suggests that Polynesian population have an increased bone density and bone strength world-wide however, not much is known about the Polynesian populations living in New Zealand. The bone forming osteoblasts contribute to the functioning of normal bone development and growth, and targeting the osteoblast phenotype has been the main focus of this study. The aim of the study was to compare gene expression in osteoblasts cultured form bone samples taken from New Zealand patients of Polynesian and Caucasian ancestry, in order to identify genes and pathways that contribute to the greater density and strength of Polynesian bones. The first part of the study measured the rate of osteoblast proliferation (S phase) and osteoblast growth (G2 phase) between the two ethnicities, using flow cytometry. Flow cytometry revealed no significant difference in the percentage of cells in S and G2 phase of the cell cycle between the two groups. No significant correlation was observed with increased BMI and age on osteoblast growth characteristics. The second part of the study investigated the gene expression profile of osteoblast phenotype markers using quantitative real-time PCR. Real-time results confirmed the data from previous studies that: ALP, WISP2, FOSB, EFHD1, EFNB2, COL1A1, DKK1, MMP13, IBSP, BGLAP and NOV genes are present in osteoblast phenotype. Unpaired Student’s t-test revealed that the levels of ALP, WISP2, FOSB, EFHD1, and EFNB2 were significantly (p < 0.05) different in the osteoblasts of Polynesians compared to Caucasian population. The differential gene expression levels may, in part, be responsible for the increase in osteoblastic response to bone mineral density and bone strength in Polynesian groups. BMI- and age-related decline has also been associated with decreased bone mineral density between the two groups. Hence, the gene expression profile in the study suggests a possible change of the biological pathways that may result in such differences. However, further studies are still needed to better understand the mechanisms of osteoblast functioning towards normal bone growth and development and to evaluate their potential for osteoporotic therapy.