Rorb Inhibits the Mineralization of Cementoblasts

Objectives: New avenues for the treatment of periodontitis can be explored by promoting the formation of new cementum, which is a highly mineralized tissue covering the root surface. RAR-related orphan receptor beta (Rorb), an osteogenic inhibitor expressed in bone tissue, may play a role in the mineralization of cementoblasts. Objectives: (1) explore the possible roles of Rorb in the mineralization of cementoblasts, and (2) reveal the mechanisms behind the action to provide the basis for a new periodontitis therapeutic target.
Methods: To determine the role of Rorb in the mineralization of cementoblasts, the immunohistochemistry and immunofluorescence were used to investigate Rorb expression and distribution. OCCM-30 cells were transfected with plasmid to increase the Rorb protein expression level. Stable overexpression cell lines were identified using qRT-PCR and western blotting. The alkaline phosphatase staining and alizarin red staining were used to detect the mineralization ability of the immortalized murine cementoblast cell line OCCM-30, which overexpresses Rorb. The RNA sequencing was used to measure the transcriptome differences in Rorb-overexpressing cementoblasts.
Results: Rorb was expressed in the cementum, periodontal ligament, alveolar bone, and pulp tissues and located in both the nucleus and cytoplasm of OCCM-30. Overexpression of Rorb significantly reduced the mineralization ability of cementoblasts. RNA-Seq analysis revealed that there were significant differences in the expression of 821 genes between the Rorb-overexpressing group and the control group (log₂(fold change) > 1.0 or < −1.0, P < 0.05), with 567 upregulated genes and 254 downregulated genes, which were mainly involved in the modulation of ATP metabolic processes, cellular response to chemical stimulus, and blood vessel morphogenesis.
Conclusions: We speculate Rorb may be a critical transcription factor of cementoblasts mineralization.