Differing responses of osteogenic cell lines to β-glycerophosphate

Ascorbic acid (Asc), dexamethasone (Dex) and beta-glycerophosphate (beta-Gly) are commonly used to promote osteogenic behaviour by osteoblasts in vitro. According to the literature, several osteosarcoma cells lines appear to respond differently to the latter with regards to proliferation kinetics and osteogenic gene transcription. Unsurprisingly, these differences lead to contrasting data between publications that necessitate preliminary studies to confirm the phenotype of the chosen osteosarcoma cell line in the presence of Asc, Dex and beta-Gly. The present study exposed Saos-2 cells to different combinations of Asc, Dex and beta-Gly for 14 days and compared the response with immortalised human mesenchymal stromal/stem cells (MSCs). Cell numbers, cytotoxicity, mineralised matrix deposition and cell proliferation were analysed to assess osteoblast-like behaviour in the presence of Asc, Dex and beta-Gly. Additionally, gene expression of runt-related transcription factor 2 (RUNX2); osteocalcin (OCN); alkaline phosphatase (ALP); phosphate regulating endopeptidase homolog X-linked (PHEX); marker of proliferation MKI67 and proliferating cell nuclear antigen (PCNA) was performed every two days during the 14-day cultures. It was found that proliferation of Saos-2 cells was significantly decreased by the presence of beta-Gly which contrasted with hMSCs where no change was observed. Furthermore, unlike hMSCs, Saos-2 cells demonstrated an upregulated expression of late osteoblastic markers, OCN and PHEX that suggested beta-Gly could affect later stages of osteogenic differentiation. In summary, it is important to consider that beta-Gly significantly affects key cell processes of Saos-2 when using it as an osteoblast-like cell model.

Automated summary

The present study investigated the response of Saos-2 cells and mesenchymal stromal/stem cells to ascorbic acid, dexamethasone, and beta-glycerophosphate. The results showed that beta-glycerophosphate significantly decreased Saos-2 cell proliferation and upregulated the expression of late osteoblastic markers, suggesting its impact on later stages of osteogenic differentiation.