Novel RANK antagonists for the treatment of bone-resorptive disease: theoretical predictions and experimental validation

Binding-induced fibrillogenesis peptide inhibits RANKL-mediated osteoclast activation against osteoporosis

Osteoporosis is primarily driven by an imbalance between bone resorption and formation, stemming from enhanced osteoclast activity during bone remodeling. At the crux of this mechanism lies the pivotal RANK-RANKL-OPG axis. In our study, we designed two binding-induced fibrillogenesis (BIF) peptides, namely BIFP and BIFY, targeting RANK and RANKL, respectively. These BIF peptides, with distinct hydrophilic and hydrophobic characteristics, assemble into nanoparticles (NPs) in aqueous solution. Through specific ligand-receptor interactions, these NPs efficiently target and bind to specific proteins, resulting in the formation of fibrous networks that effectively inhibit the RANK-RANKL associations. Experiments have confirmed the potent inhibitory effects of peptides on both osteoclast differentiation and function. Compared with the +RANKL controls, BIFP and BIFY demonstrated a more remarkable reduction in tartrate resistant acid phosphatase (TRAP)-positive cells, achieving an impressive decline of 82.8% and 70.7%, respectively. Remarkably, the administration of BIFP led to a substantial reduction in bone resorption pit area by 17.4%, compared to a significant increase of 92.4% in the +RANKL groups. In vivo experiments on an ovariectomized mouse model demonstrated that the BIFP treated group exhibited an impressive 2.6-fold elevation in bone mineral density and an astounding 4.0-fold enhancement in bone volume/total volume as against those of the PBS-treated group. Overall, BIF peptides demonstrate remarkable abilities to impede osteoclast differentiation, presenting promising prospects for the treatment of osteoporosis.

Propionibacterium freudenreichii Inhibits RANKL-Induced Osteoclast Differentiation and Ameliorates Rheumatoid Arthritis in Collagen-Induced Arthritis Mice

Osteoclast differentiation is crucial for bone absorption, and osteoclasts are involved in bone destruction in rheumatoid arthritis (RA). Dairy Propionibacterium freudenreichii is used as a cheese starter and possesses prebiotic and postbiotic properties. It is known to stimulate the growth of bifidobacteria and produces valuable metabolites, such as vitamin B12 and propionic acid. However, limited information is available on the beneficial effects of P. freudenreichii on human disease. Herein, we aimed to investigate the inhibitory effect of P. freudenreichii MJ2 (MJ2) isolated from raw milk on osteoclast differentiation and evaluate the improvement in RA. The murine macrophage cell line, RAW 264.7, and a collagen-induced arthritis (CIA) mouse model were used to perform in vitro and in vivo studies, respectively. Heat-killed P. freudenreichii MJ2 (hkMJ2)-treated cells significantly inhibited RANKL-induced osteoclast differentiation and TRAP activity. HkMJ2-treated cells exhibited significantly decreased expression of genes and proteins related to RANKL-induced osteoclast differentiation. MJ2 administration decreased the arthritic score in the CIA mouse model. Live and dead MJ2 inhibited bone loss and afforded protection against bone erosion and joint damage in CIA mice. MJ2 decreased the levels of collagen-specific antibodies and inflammatory cytokines and the expression of osteoclast differentiation-related genes and proteins in CIA mice. Interestingly, live and dead MJ2 showed similar RA improvement effects in CIA mice. In conclusion, P. freudenreichii MJ2 inhibited osteoclast differentiation by inhibiting the NF-κB signaling pathway and ameliorated CIA.

The RANK/RANKL/OPG system in tumorigenesis and metastasis of cancer stem cell: potential targets for anticancer therapy

The molecular triad involving receptor activator of nuclear factor kβ (RANK)/RANK ligand (RANKL)/osteoprotegerin cytokine system has been well implicated in several physiological and pathological processes including bone metabolism, mammary gland development, regulation of the immune function, tumorigenesis and metastasis of cancer stem cell, thermoregulation, and vascular calcification. However, this review aimed to summarize several original and up-to-date articles focusing on the role of this signaling system in cancer cell development and metastasis as well as potential therapeutic agents targeting any of the three tumor necrotic factor super family proteins and/or their downstream signaling pathways. The RANK/RANKL axis has direct effects on tumor cell development. The system is well involved in the development of several primary and secondary tumors including breast cancer, prostate cancer, bone tumors, and leukemia. The signaling of this triad system has also been linked to tumor invasiveness in the advanced stage. Bone is by far the most common site of cancer metastasis. Several therapeutic agents targeting this system have been developed. Among them, a monoclonal antibody, denosumab, was clinically approved for the treatment of osteoporosis and cancer-related diseases.

RANK-RANKL signalling in cancer

Oncogenic events combined with a favourable environment are the two main factors in the oncological process. The tumour microenvironment is composed of a complex, interconnected network of protagonists, including soluble factors such as cytokines, extracellular matrix components, interacting with fibroblasts, endothelial cells, immune cells and various specific cell types depending on the location of the cancer cells (e.g. pulmonary epithelium, osteoblasts). This diversity defines specific "niches" (e.g. vascular, immune, bone niches) involved in tumour growth and the metastatic process. These actors communicate together by direct intercellular communications and/or in an autocrine/paracrine/endocrine manner involving cytokines and growth factors. Among these glycoproteins, RANKL (receptor activator nuclear factor-κB ligand) and its receptor RANK (receptor activator nuclear factor), members of the TNF and TNFR superfamilies, have stimulated the interest of the scientific community. RANK is frequently expressed by cancer cells in contrast with RANKL which is frequently detected in the tumour microenvironment and together they participate in every step in cancer development. Their activities are markedly regulated by osteoprotegerin (OPG, a soluble decoy receptor) and its ligands, and by LGR4, a membrane receptor able to bind RANKL. The aim of the present review is to provide an overview of the functional implication of the RANK/RANKL system in cancer development, and to underline the most recent clinical studies.

Pro-osteoclastic in vitro effect of Polyethylene-like nanoparticles: Involvement in the pathogenesis of implant aseptic loosening

Polyethylene micro-sized wear particles released from orthopedic implants promote inflammation and osteolysis; however, less is known about the bioactivity of polyethylene nanosized wear particles released from the last generation of polymer-bearing surfaces. We aim to assess the internalization of fluorescent polyethylene-like nanoparticles by both human macrophages and osteoclasts and also, to determine their effects in osteoclastogenesis in vitro. Human macrophages and osteoclasts were incubated with several ratios of fluorescent polyethylene-like nanoparticles between 1 and 72 h, and 4 h, 2, 4, 6, and 9 days, respectively. The internalization of nanoparticles was quantified by flow cytometry and followed by both confocal and video time-lapse microscopy. Osteoclast differentiation and activity was semiquantified by tartrate-resistant acid phosphatase (TRAP) staining, TRAP mRNA relative expression, and pit resorption assay, respectively. Macrophages, osteoclast precursors and mature osteoclasts internalized nanoparticles in a dose- and time-dependent manner and maintained their resorptive activity. In addition, nanoparticles significantly increased the osteoclastogenesis as shown by upregulation of the TRAP expressing cell number. We conclude that polyethylene-like nanosized wear particles promote osteoclast differentiation without alteration of bone resorptive activity of mature osteoclasts and they could be considered as important actors in periprosthetic osteolysis of the last new generation of polymer-bearing surfaces. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2649-2657, 2016.

Bone health nutraceuticals alter microarray mRNA gene expression: A randomized, parallel, open-label clinical study

BACKGROUND AND OBJECTIVE

Dietary intake of fruits and vegetables has been suggested to have a role in promoting bone health. More specifically, the polyphenols they contain have been linked to physiological effects related to bone mineral density and bone metabolism. In this research, we use standard microarray analyses of peripheral whole blood from post-menopausal women treated with two fixed combinations of plant extracts standardized to polyphenol content to identify differentially expressed genes relevant to bone health.

METHODS

In this 28-day open-label study, healthy post-menopausal women were randomized into three groups, each receiving one of three investigational fixed combinations of plant extracts: an anti-resorptive (AR) combination of pomegranate fruit (Punica granatum L.) and grape seed (Vitis vinifera L.) extracts; a bone formation (BF) combination of quercetin (Dimorphandra mollis Benth) and licorice (Glycyrrhiza glabra L.) extracts; and a fixed combination of all four plant extracts (AR plus BF). Standard microarray analysis was performed on peripheral whole blood samples taken before and after each treatment. Annotated genes were analyzed for their association to bone health by comparison to a gene library.

RESULTS

The AR combination down-regulated a number of genes involved in reduction of bone resorption including cathepsin G (CTSG) and tachykinin receptor 1 (TACR1). The AR combination also up-regulated genes associated with formation of extracellular matrix including heparan sulfate proteoglycan 2 (HSPG2) and hyaluronoglucosaminidase 1 (HYAL1). In contrast, treatment with the BF combination resulted in up-regulation of bone morphogenetic protein 2 (BMP-2) and COL1A1 (collagen type I α1) genes which are linked to bone and collagen formation while down-regulating genes linked to osteoclastogenesis. Treatment with a combination of all four plant extracts had a distinctly different effect on gene expression than the results of the AR and BF combinations individually. These results could be due to multiple feedback systems balancing activities of osteoblasts and osteoclasts.

CONCLUSION

In summary, this ex-vivo microarray study indicated that the pomegranate, grape seed, quercetin and licorice combinations of plant extracts modulated gene expression for both osteoclastic and osteogenic processes.

Explaining RANKL inhibition by OPG through quantum biochemistry computations and insights into peptide-design for the treatment of osteoporosis

Quantum biochemistry computations are applied to precisely describe important protein–protein interactions, providing a basis for the design of inhibitory peptides against osteoporosis.

Changes of serum levels of MMP-3, sRANKL, and OPG in juvenile-onset ankylosing spondylitis patients carrying different HLA-B27 subtypes

Ankylosing spondylitis (AS) patients whose symptom onset occurs before 16 years of age are termed juvenile-onset ankylosing spondylitis (JAS). Investigations suggested that JAS had worse functional outcome, and abnormality of bone metabolism can appear in early stage of AS. The objectives of this study are to compare changes of serum inflammatory and bone metabolic markers and to explore the relationship between these biomarkers and disease activity in JAS with different HLA-B27 subtypes. Serum matrix metallopeptidase-3 (MMP-3), soluble receptor activator of nuclear factor-κB ligand (sRANKL), and osteoprotegerin (OPG) were detected by ELISA in 56, 62, and 68 JAS patients, respectively, and 32 healthy individuals were as controls. Serum MMP-3 and sRANKL were significantly higher and OPG in JAS was slightly higher than those in controls. There was no significant difference in the level of MMP-3, sRANKL, and OPG among JAS patients with B27 negativity, B*2704, B*2705, and B*2715, respectively. Serum levels of MMP-3 showed positive correlation with BASDAI and BASFI (Bath Ankylosing Spondylitis Disease Activity Index and Functional Index). Serum level of sRANKL showed positive correlation with MMP-3 and negative correlation with disease duration. The significantly higher sRANKL expression suggested the enhanced osteoclast function and imbalance of RANKL/OPG system in the inflammatory process of JAS patients carrying different B27 subtypes. It should be paid attention to the abnormality of bone metabolism during the treatment of JAS.

Juvenile Paget's disease with heterozygous duplication within TNFRSF11A encoding RANK

Mendelian disorders of RANKL/OPG/RANK signaling feature the extremes of aberrant osteoclastogenesis and cause either osteopetrosis or rapid turnover skeletal disease. The patients with autosomal dominant accelerated bone remodeling have familial expansile osteolysis, early-onset Paget's disease of bone, expansile skeletal hyperphosphatasia, or panostotic expansile bone disease due to heterozygous 18-, 27-, 15-, and 12-bp insertional duplications, respectively, within exon 1 of TNFRSF11A that encodes the signal peptide of RANK. Juvenile Paget's disease (JPD), an autosomal recessive disorder, manifests extremely fast skeletal remodeling, and is usually caused by loss-of-function mutations within TNFRSF11B that encodes OPG. These disorders are ultra-rare. A 13-year-old Bolivian girl was referred at age 3years. One femur was congenitally short and curved. Then, both bowed. Deafness at age 2years involved missing ossicles and eroded cochleas. Teeth often had absorbed roots, broke, and were lost. Radiographs had revealed acquired tubular bone widening, cortical thickening, and coarse trabeculation. Biochemical markers indicated rapid skeletal turnover. Histopathology showed accelerated remodeling with abundant osteoclasts. JPD was diagnosed. Immobilization from a femur fracture caused severe hypercalcemia that responded rapidly to pamidronate treatment followed by bone turnover marker and radiographic improvement. No TNFRSF11B mutation was found. Instead, a unique heterozygous 15-bp insertional tandem duplication (87dup15) within exon 1 of TNFRSF11A predicted the same pentapeptide extension of RANK that causes expansile skeletal hyperphosphatasia (84dup15). Single nucleotide polymorphisms in TNFRSF11A and TNFRSF11B possibly impacted her phenotype. Our findings: i) reveal that JPD can be associated with an activating mutation within TNFRSF11A, ii) expand the range and overlap of phenotypes among the Mendelian disorders of RANK activation, and iii) call for mutation analysis to improve diagnosis, prognostication, recurrence risk assessment, and perhaps treatment selection among the monogenic disorders of RANKL/OPG/RANK activation.