Junior Researcher/PhD Student Insitute of Cytology RAS, Saint Petersburg, Russia
Abstract: Runx2 is a transcription factor and a key regulator of osteogenic differentiation, playing an essential role in skeletal development. It not only controls the expression of genes involved in bone formation but also interacts with several signaling pathways, such as Wnt, Bmp, and Notch. Despite significant progress in understanding the role of Runx2 in bone formation, the relationship between Runx2 and the Notch signaling pathway, and the specific role of Runx2 in this process, remains poorly understood. The aim of this study was to investigate the dynamics of Runx2 activation at the RNA and protein levels during the early stages of osteogenic differentiation and to analyse the relationship between Runx2 and the Notch signaling pathway. Primary human osteoblasts derived from femoral trabecular bone served as the experimental model. Findings revealed that Runx2 expression begins to rise 12 hours after osteogenic induction, highlighting finely tuned regulation through transcriptional control and protein degradation. A critical threshold of Runx2 protein appears necessary to trigger differentiation. During the early stages of Runx2 activation in osteoblasts, we observed a rise in the expression of SPP1 and BGLAP. This suggests that the accumulation of RUNX2 transcripts during the induction of osteogenic differentiation affects the expression of various osteogenic markers. Proteasomal inhibition studies further confirmed that transient reductions in Runx2 are pivotal for initiating differentiation, while prolonged stabilization inhibits the process. Furthermore, we observed an increase in the expression of the NOTCH1 at 6 hours after the initiation of osteogenic differentiation. The accumulation pattern of transcripts, the Runx2 protein, and the components of the Notch signaling pathway suggest that all these elements are involved in the induction and progression of osteogenic differentiation.
Funding Source: The work was carried out with the financial support of the Russian Science Foundation (project no. 23-15-00320).
