Osteoprotection Through the Deletion of the Transcription Factor Rorβ in Mice

Abstract

There is a clinical need to identify new molecular targets for the treatment of osteoporosis, particularly those that simultaneously inhibit bone resorption while stimulating bone formation. We have previously shown in overexpression studies that retinoic acid receptor-related orphan receptor β (Rorβ) suppresses in vitro osteoblast differentiation. In addition, the expression of Rorβ is markedly increased in bone marrow-derived mesenchymal stromal cells with aging in both mice and humans. Here we establish a critical role for Rorβ in regulating bone metabolism using a combination of in vitro and in vivo studies. We used Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 gene editing to demonstrate that loss of Rorβ in osteoblasts enhances Wnt signaling, specifically through increased recruitment of β-catenin to T-cell factor/lymphoid enhancer factor (Tcf/Lef) DNA binding sites in the promoters of the Wnt target genes Tcf7 and Opg. This resulted in increased osteogenic gene expression and suppressed osteoclast formation through increased osteoprotegerin (OPG) secretion in Rorβ-deficient cells. Consistent with our in vitro data, genetic deletion of Rorβ in both female and male mice resulted in preserved bone mass and microarchitecture with advancing age due to increased bone formation with a concomitant decrease in resorption. The improved skeletal phenotype in the Rorβ mice was also associated with increased bone protein levels of TCF7 and OPG. These data demonstrate that loss of Rorβ has beneficial skeletal effects by increasing bone formation and decreasing bone resorption, at least in part through β-catenin-dependent activation of the Wnt pathway. Thus, inhibition of Rorβ represents a novel approach to potentially prevent or reverse osteoporosis. © 2017 American Society for Bone and Mineral Research.

Insights into the Role of Circadian Rhythms in Bone Metabolism: A Promising Intervention Target?

“…Knockout of the ROR β gene in osteoblasts promotes expression of osteogenic genes and osteoprotegerin (OPG). Consistent with in vitro results, ROR β -/- mice exhibited increased bone volume [ 108 ].…”

Advances in Orthodontic Tooth Movement: Gene Therapy and Molecular Biology Aspect

“…With this mechanism, the plasmid containing gRNA, Cas9 sequences, TracrRNA (transactivating CRISP RNA) and DNA repair template sequence can be introduced into cells or embryo of the animals by viral or nonviral delivery system [135]. Until now, there is no CRISPR/Cas9 experiment involving orthodontic tooth movement, however, this technology has been implemented in recent mineralized tissue research [136][137][138][139]. Future directions of gene therapy include the enhancement of the lentiviral vector-based approaches, fine tuning of the conditioning regimen, and the design of safer vectors or nonviral vector delivery system.…”

miR-219a-5p Regulates Rorβ During Osteoblast Differentiation and in Age-related Bone Loss

“…Rorβ inhibits osteoblast differentiation and Rorβ expression increases with age in both mice and human bone‐lineage cells, establishing a reciprocal relation between Rorβ expression and osteogenic potential. At the molecular level, Rorβ represses both Runx2‐ and β‐catenin‐dependent transcriptional activation . Furthermore, global deletion of Rorβ in mice results in improved bone mass, microarchitecture, and strength associated with increased bone formation, decreased resorption, and increased activation of the Wnt pathway .…”

“…The orphan nuclear receptor, Rorβ is a transcription factor that has recently been shown to be a negative regulator of bone. Rorβ inhibits osteoblast differentiation and Rorβ expression increases with age in both mice and human bone-lineage cells, (7–9) establishing a reciprocal relation between Rorβ expression and osteogenic potential. At the molecular level, Rorβ represses both Runx2- and β-catenin-dependent transcriptional activation.…”

“…At the molecular level, Rorβ represses both Runx2- and β-catenin-dependent transcriptional activation. (7,9) Furthermore, global deletion of Rorβ in mice results in improved bone mass, microarchitecture, and strength associated with increased bone formation, decreased resorption, and increased activation of the Wnt pathway. (9) Therefore, the identification and development of novel therapeutic approaches to downregulate Rorβ may be a new approach in osteoporosis treatment.…”