Bone marrow osteoprogenitors are depleted whereas osteoblasts are expanded independent of the osteogenic vasculature in response to zoledronic acid

Improvement of osteogenesis and antibacterial properties of a bioactive glass/gelatin-based scaffold using zoledronic acid and CM11 peptide

This study aimed to investigate the effects of zoledronic acid (ZA) and antibacterial CM11 peptide on the osteoinduction and antibacterial properties of bioactive glass (BG). The bioactive glass/gelatin (BG/Gel) composite was synthesized using the sol-gel method. The 2-x minimum inhibitory concentration of the peptide and 4.00 mg mL-1 of ZA were added to the BG/Gel during fabrication. The BG/Gel composite morphological and structural characteristics and anti-bacterial activities were analyzed using Fourier transform infra-red spectroscopy, scanning electron microscopy and disk diffusion test, respectively. The release of the peptide and ZA from BG/Gel was measured using ultra-violet spectroscopy. After 14 days, the effects of the peptide/ ZA-containing BG/Gel (PZ-BG/Gel) on the growth and differentiation of mesenchymal stem cells were evaluated using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide, calcium and alkaline phosphatase assays, immunocytochemical staining for osteocalcin (OCN) and real-time polymerase chain reaction for OCN, type I collagen, bone morphogenetic protein 2 and Runt-related transcription factor-2 genes. The disk diffusion test showed the anti-microbial activity of the scaffold against multi-drug-resistant isolates of Pseudomonas aeruginosa and Staphylococcus aureus. Analyses showed a significantly higher level of stem cells differentiation into the osteo-genic cells in PZ-BG/Gel scaffold compared to BG/Gel scaffold alone. Accordingly, osteoblast markers were significantly increased in comparison with the control. In conclusion, the osteo-induction and antibacterial properties of BG-based scaffold can be improved using ZA and CM11.

Macrophage miR-149-5p induction is a key driver and therapeutic target for BRONJ

Bisphosphonate-related (BP-related) osteonecrosis of the jaw (BRONJ) is one of the severe side effects of administration of BPs, such as zoledronic acid (ZA), which can disrupt the patient’s quality of life. Although the direct target of skeletal vasculature and bone resorption activity by BPs has been phenomenally observed, the underlying mechanism in BRONJ remains largely elusive. Thus, it is urgently necessary to discover effective therapeutic targets based on the multifaceted underlying mechanisms in the development of BRONJ. Here, we determined the inhibitory role of ZA-treated macrophages on osteoclast differentiation and type H vessel formation during tooth extraction socket (TES) healing. Mechanistically, ZA activated the NF-κB signaling pathway and then induced p65 nuclear translocation in macrophages to promote miR-149-5p transcription, resulting in impaired osteoclast differentiation via directly binding to the Traf6 3′-UTR region. Moreover, we identified that miR-149-5p–loaded extracellular vesicles derived from ZA-treated bone marrow–derived macrophages could regulate biological functions of endothelial cells via the Rap1a/Rap1b/VEGFR2 pathway. Furthermore, local administration of chemically modified antagomiR-149-5p was proven to be therapeutically effective in BRONJ mice. In conclusion, our findings illuminate the dual effects of miR-149-5p on skeletal angiogenesis and bone remolding, suggesting it as a promising preventive and therapeutic target for BRONJ.

An injectable self-adaptive polymer as a drug carrier for the treatment of nontraumatic early-stage osteonecrosis of the femoral head

Core decompression (CD) with the elimination of osteonecrotic bone is the most common strategy for treating early-stage nontraumatic osteonecrosis of the femoral head (ONFH). Adjuvant treatments are widely used in combination with CD as suitable methods of therapy. Existing augmentations have to be fabricated in advance. Here, we report a novel injectable glycerin-modified polycaprolactone (GPCL) that can adapt to the shape of the CD cavity. GPCL shows great flowability at 52.6 °C. After solidification, its compressive modulus was 120 kPa at body temperature (37 °C). This excellent characteristic enables the polymer to provide mechanical support in vivo. In addition, GPCL acts as a carrier of the therapeutic agent zoledronic acid (ZA), demonstrating sustained release into the CD region. ZA-loaded GPCL was injected into ONFH lesions to treat early-stage nontraumatic cases. Compared to that in the CD group, CD+ZA-loaded GPCL injection preserved bone density and increased the collagen level in the femoral head. At the interface between the GPCL and CD tunnel wall, osteogenesis was significantly promoted. In addition, morphological evaluations revealed that the femoral heads in the CD+ZA-GPCL group exhibited improved pressure resistance. These results suggest a strategy effective to preserve the bone density of the femoral head, thus decreasing the possibility of femoral head collapse. This novel injectable polymer has, therefore, considerable potential in clinical applications.

Osteoblast-Derived Paracrine and Juxtacrine Signals Protect Disseminated Breast Cancer Cells from Stress

Metastatic breast cancer in bone is incurable and there is an urgent need to develop new therapeutic approaches to improve survival. Key to this is understanding the mechanisms governing cancer cell survival and growth in bone, which involves interplay between malignant and accessory cell types. Here, we performed a cellular and molecular comparison of the bone microenvironment in mouse models representing either metastatic indolence or growth, to identify mechanisms regulating cancer cell survival and fate. In vivo, we show that regardless of their fate, breast cancer cells in bone occupy niches rich in osteoblastic cells. As the number of osteoblasts in bone declines, so does the ability to sustain large numbers of breast cancer cells and support metastatic outgrowth. In vitro, osteoblasts protected breast cancer cells from death induced by cell stress and signaling via gap junctions was found to provide important juxtacrine protective mechanisms between osteoblasts and both MDA-MB-231 (TNBC) and MCF7 (ER+) breast cancer cells. Combined with mathematical modelling, these findings indicate that the fate of DTCs is not controlled through the association with specific vessel subtypes. Instead, numbers of osteoblasts dictate availability of protective niches which breast cancer cells can colonize prior to stimulation of metastatic outgrowth.

Oestrogen and zoledronic acid driven changes to the bone and immune environments: Potential mechanisms underlying the differential anti-tumour effects of zoledronic acid in pre- and post-menopausal conditions

Late stage breast cancer commonly metastasises to bone and patient survival averages 2-3 years following diagnosis of bone involvement. One of the most successful treatments for bone metastases is the bisphosphonate, zoledronic acid (ZOL). ZOL has been used in the advanced setting for many years where it has been shown to reduce skeletal complications associated with bone metastasis. More recently, several large adjuvant clinical trials have demonstrated that administration of ZOL can prevent recurrence and improve survival when given in early breast cancer. However, these promising effects were only observed in post-menopausal women with confirmed low concentrations of circulating ovarian hormones. In this review we focus on potential interactions between the ovarian hormone, oestrogen, and ZOL to establish credible hypotheses that could explain why anti-tumour effects are specific to post-menopausal women. Specifically, we discuss the molecular and immune cell driven mechanisms by which ZOL and oestrogen affect the tumour microenvironment to inhibit/induce tumour growth and how oestrogen can interact with zoledronic acid to inhibit its anti-tumour actions.