Risk comparison of osteonecrosis of the jaw in osteoporotic patients treated with bisphosphonates vs. denosumab: a multi-institutional retrospective cohort study in Taiwan

Oroxylin A suppresses breast cancer-induced osteoclastogenesis and osteolysis as a natural RON inhibitor

BACKGROUND

Malignant breast cancer cells trigger the over-activation of osteoclast precursor cells, leading to bone loss and severe pain. Targeted inhibition of osteoclast differentiation has emerged as an important strategy for treating bone syndromes induced by breast cancer.

PURPOSE

The objective is to discover natural osteoclast inhibitor to treat osteoclastogenesis and bone destruction induced by breast cancer, and clarify the specific mechanisms.

METHODS

Recepteur d'origine Nantais (RON) protein was employed to search the natural osteoclast inhibitor for breast cancer-induced osteoclastogenesis by molecular docking, molecular dynamics simulation and cellular thermal shift assay (CETSA). In the in vitro experiment, breast cancer MDA-MB-231 cell-conditioned medium (MDA-MB-231 CM) was used to induce osteoclastogenesis in murine bone marrow-derived macrophages (BMMs), aiming to elucidate the effects and mechanisms of the natural osteoclast inhibitor. In the in vivo model, MDA-MB-231 cells was injected into the mouse tibia to evaluate the therapeutic effect of drug on breast cancer-induced bone destruction.

RESULTS

We discovered a significant increase in the expression of RON during MDA-MB-231 CM-induced osteoclast differentiation in vitro. Molecular docking analysis found that oroxylin A (OA), a flavonoid derived from the Chinese medicine Scutellaria baicalensis Georgi, showed binding ability with RON, while its impact and mechanism on breast cancer-induced osteoclastogenesis and osteolysis remains unclear. Molecular dynamics simulation and CETSA further revealed that OA bound directly to the RON protein, and it also decreased RON expression in breast cancer CM-induced osteoclastogenesis. Correspondingly, OA suppressed the MDA-MB-231 CM-induced osteoclastogenesis and bone resorption in vitro. The downstream signals of RON including Src and NFATc1, as well as the osteoclast-specific genes, were downregulated by OA. Of interesting, the suppressive effect of OA on osteoclastogenesis induced by MDA-MB-231 CM was abolished after RON was knocked down by the specific RON-siRNA, this further confirmed that OA showed inhibitory effects on osteoclasts through targeting RON. In addition, we found that OA attenuated MDA-MB-231 cell-induced osteolysis and reduced the number of osteoclasts in vivo.

CONCLUSION

Our results indicate that OA acts as a natural RON inhibitor to suppress breast cancer-induced osteoclastogenesis and osteolysis. This provides new strategy for treating breast cancer-induced bone destruction and related syndromes.

Curcumin-loaded scaffolds in bone regeneration

In recent years, there has been a notable surge in the development of engineered bone scaffolds intended for the repair of bone defects. While autografts and allografts have traditionally served as the primary methods in bone tissue engineering, their inherent limitations have spurred the exploration of novel avenues in biomedical implant development. The emergence of bone scaffolds not only facilitates bone reconstruction but also offers a platform for the targeted delivery of therapeutic agents. There exists a pervasive interest in leveraging various drugs, proteins, growth factors, and biomolecules with osteogenic properties to augment bone formation, as the enduring side effects associated with current clinical modalities necessitate the pursuit of safer alternatives. Curcumin, the principal bioactive compound found in turmeric, has demonstrated notable efficacy in regulating the proliferation and differentiation of bone cells while promoting bone formation. Nevertheless, its utility is hindered by restricted water solubility and poor bioavailability. Strategies aimed at enhancing the solubility, stability, and bioavailability of curcumin, including formulation techniques such as liposomes and nanoparticles or its complexation with metals, have been explored. This investigation is dedicated to exploring the impact of curcumin on the proliferation, differentiation, and migration of osteocytes, osteoblasts, and osteoclasts.

Inhibition of PPP1R15A alleviates osteoporosis via suppressing RANKL-induced osteoclastogenesis

Osteoporosis results from overactivation of osteoclasts. There are currently few drug options for treatment of this disease. Since the successful development of allosteric inhibitors, phosphatases have become attractive therapeutic targets. Protein phosphatase 1, regulatory subunit 15 A (PPP1R15A), is a stress-responsive protein, which promotes the UPR (unfolded protein response) and restores protein homeostasis. In this study we investigated the role of PPP1R15A in osteoporosis and osteoclastogenesis. Ovariectomy (OVX)-induced osteoporosis mouse model was established, osteoporosis was evaluated in the left femurs using micro-CT. RANKL-stimulated osteoclastogenesis was used as in vitro models. We showed that PPP1R15A expression was markedly increased in BMMs derived from OVX mice and during RANKL-induced osteoclastogenesis in vitro. Knockdown of PPP1R15A or application of Sephin1 (a PPP1R15A allosteric inhibitor in a phase II clinical trial) significantly inhibited osteoclastogenesis in vitro. Sephin1 (0.78, 3.125 and 12.5 μM) dose-dependently mitigated the changes in NF-κB, MAPK, and c-FOS and the subsequent nuclear factor of activated T cells 1 (NFATc1) translocation in RANKL-stimulated BMMs. Both Sephin1 and PPP1R15A knockdown increased the phosphorylated form of eukaryotic initiation factor 2α (eIF2α); knockdown of eIF2α reduced the inhibitory effects of Sephin1 on NFATc1-luc transcription and osteoclast formation. Furthermore, Sephin1 or PPP1R15A knockdown suppressed osteoclastogenesis in CD14+ monocytes from osteoporosis patients. In OVX mice, injection of Sephin1 (4, 8 mg/kg, i.p.) every two days for 6 weeks significantly inhibited bone loss, and restored bone destruction and decreased TRAP-positive cells. This study has identified PPP1R15A as a novel target for osteoclast differentiation, and genetic inhibition or allosteric inhibitors of PPP1R15A, such as Sephin1, can be used to treat osteoporosis. This study revealed that PPP1R15A expression was increased in osteoporosis in both human and mice. Inhibition of PPP1R15A by specific knockdown or an allosteric inhibitor Sephin1 mitigated murine osteoclast formation in vitro and attenuated ovariectomy-induced osteoporosis in vivo. PPP1R15A inhibition also suppressed pathogenic osteoclastogenesis in CD14+ monocytes from osteoporosis patients. These results identify PPP1R15A as a novel regulator of osteoclastogenesis and a valuable therapeutic target for osteoporosis.

Bisphosphonates and osteonecrosis of the jaws: Clinical and forensic aspects

OBJECTIVE

This manuscript aims to provide a comprehensive review of the current knowledge in the pathophysiology, diagnosis, prevention, and other relevant clinical and forensic aspects of a potentially severe complication known as medication-related osteonecrosis of the jaw (MRONJ) while synthesizing state-of-the-art information on bisphosphonates and introducing a possible differential diagnosis.

DESIGN

An extensive search was conducted in PubMed (U.S. National Library of Medicine) without a time or language constraint, focusing on the epidemiology, pathophysiology, risk factors, site specificity, signs and symptoms, differential diagnosis, prevention, and forensic aspects of MRONJ. All types of original articles, reviews, case reports, short communications, opinion articles, guidelines, and letters to editors were considered to produce a complete review on this subject.

RESULTS

MRONJ prevention relies on a multidisciplinary approach and is critical since truly effective treatments are lacking. This therapeutic challenge is partly due to uncertainty regarding this condition's pathophysiology. Differential diagnosis of osteonecrosis of the jaws associated with krokodil abuse, one of the most dangerous and homemade psychoactive illicit substances, should be considered.

CONCLUSIONS

Further research into the etiology and site specificity of MRONJ is encouraged, aiming to develop novel treatment prospects. Indeed, comprehending this would allow for increased efficacy and therapeutic options while emphasizing the importance of prevention. In addition, we advocate for greater consensus among the various societies regarding MRONJ's treatment and management.