Inhibition of osteoporosis by the αvβ3 integrin antagonist of rhodostomin variants

Advances in nanodelivery systems based on apoptosis strategies for enhanced rheumatoid arthritis therapy

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disorder primarily characterized by persistent synovial inflammation and progressive bone erosion. The pathogenesis of RA involves a complex cascade of cellular and molecular events, including sustained hyperactivation of macrophages, excessive recruitment and activation of neutrophils, pathological proliferation and invasion of fibroblast-like synoviocytes (FLS), and dysregulated differentiation and function of osteoclasts (OCs). The inflammatory factors secreted by these dysregulated cells significantly disrupt the joint microenvironment through multiple pathological mechanisms, primarily by promoting synovial inflammation, cartilage matrix degradation, osteoclast-mediated bone erosion, and pathological angiogenesis. Therapeutic strategies targeting the induction of apoptosis in these malignant cells have demonstrated considerable potential in preclinical studies, offering a promising approach to enhance treatment outcomes by simultaneously reducing inflammatory cytokine production and inhibiting pathogenic cell proliferation. However, conventional therapeutic drugs are limited in clinical applications because of their high toxicity and side effects. Inflammation induces morphological and functional changes in cells within the rheumatoid arthritis microenvironment (RAM), particularly the overexpression of specific receptors on cell membranes. This phenomenon has driven the development of ligand-modified targeted nanodelivery systems (NDSs), which can specifically target and induce apoptosis in specific cell types, thereby enhancing therapeutic efficacy. This paper comprehensively reviews the research progress of targeted NDSs based on apoptosis strategies for RA therapy, with a detailed discussion of their advantages in inducing apoptosis in various disease-associated cells. Furthermore, the potential of combining apoptosis of multiple cell types for RA treatment is explored. This review is expected to improve insights into the apoptosis of malignant cells to enhance RA therapy. STATEMENT OF SIGNIFICANCE: This review highlights recent advances in nanodelivery systems (NDSs) based on apoptotic strategies for enhanced rheumatoid arthritis (RA) therapy. Unlike conventional NDSs, these optimized systems specifically induce apoptosis in malignant cells within the RA microenvironment by integrating multiple therapeutic strategies. By summarizing the latest research, our work demonstrates the potential of these NDSs to suppress inflammatory responses and prevent bone destruction through targeted elimination of malignant cells, offering a novel direction for RA treatment. This review is significant as it provides a comprehensive overview for researchers and clinicians, facilitating the development of more effective therapeutic approaches for RA and other chronic inflammatory diseases.

A microprotein encoded by LINC00263 promotes breast cancer osteolytic bone metastasis by inducing osteoclastogenesis and inhibiting osteoclast ferroptosis

Currently, there are no effective prevention or therapeutic methods for breast cancer bone metastasis (BC-BM), which leading to severe skeletal complications and increased mortality. Understanding the mechanisms underlying BC-BM could provide potential strategies for its prevention and treatment. In this study, we identified a new microprotein encoded by lncRNA LINC00263, which we named LINC00263-encoded protein (LINC00263-P), was significantly upregulated in bone metastatic breast cancer tissues and correlated with BC-BM. Overexpression of LINC00263 significantly promoted BC-BM, while treatment with the neutralizing anti-LINC00263-P antibody effectively inhibited BC-BM. Mechanically, the LINC00263-P binds to integrin αvβ3 for activating Src/Syk/Vav-3 axis and yes-associated protein 1 (YAP1) pathway, which enhanced osteoclastogenesis and diminishes ferroptosis in osteoclasts, thereby creating an osteolytic bone metastasis niche that fosters BC-BM. Importantly, treatment with angoroside C, an active component from the traditional Chinese medicine Scrophulariae Radix extract, effectively blocked the binding of LINC00263-P to αvβ3, thereby inhibiting abnormal osteoclastogenesis and preventing BC-BM. These findings highlight the crucial role of microprotein LINC00263-P in disrupting bone homeostasis and propose a potential molecular mechanism of BC-BM.

Bone Disease in Primary Hyperparathyroidism-Changes Occurring in Bone Metabolism and New Potential Treatment Strategies

Primary hyperparathyroidism (PHPT) is a common endocrinopathy, predominantly caused by a single parathyroid adenoma that is responsible for the excessive secretion of parathyroid hormone (PTH)-the hallmark of disease. Excess of this hormone causes remarkable changes in bone metabolism, including an increased level of bone remodeling with a predominance of bone resorption. Those changes lead to deterioration of bone structure and density, especially in cortical bone. The main treatment for PHPT is surgical removal of the adenoma, which normalizes PTH levels and terminates the progression of bone disease and leads to its regeneration. However, because not all the patients are suitable candidates for surgery, alternative therapies are needed. Current non-surgical treatments targeting bone disease secondary to PHPT include bisphosphonates and denosumab. Those antiresorptives prevent further bone loss, but they lack the ability to regenerate already degraded bone. There is ongoing research to find targeted drugs capable of halting resorption alongside stimulating bone formation. This review presents the advancements in understanding the molecular mechanisms responsible for bone disease in PHPT and assesses the efficacy of new potential therapeutic approaches (e.g., allosteric inhibitors of the PTH receptor, V-ATPase, or cathepsin inhibitors) aimed at mitigating bone loss and enhancing bone regeneration in affected patients.

Jiangu formula: A novel osteoclast-osteoblast coupling agent for effective osteoporosis treatment

BACKGROUND

The discovering of an osteoclast (OC) coupling active agent, capable of suppressing OC-mediated bone resorption while concurrently stimulating osteoblast (OB)-mediated bone formation, presents a promising strategy to overcome limitations associated with existing antiresorptive agents. However, there is a lack of research on active OC coupling agents.

PURPOSE

This study aims to investigate the potential of Jiangu Formula (JGF) in inhibiting OCs while maintaining the OCOB coupling function.

METHODS

The anti-osteoporosis efficacy of JGF was evaluated in osteoporosis models induced by ovariectomy in C57BL/6 mouse and SD rats. The effect of JGF on OCs was evaluated by detecting its capacity to inhibit OC differentiation and bone resorption in an in vitro osteoclastogenesis model induced by RANKL. The OCOB coupling activity of JGF was evaluated by measuring the secretion levels of OC-derived coupling factors, OB differentiation activity of MC3T3-E1 interfered with conditioned medium, and the effect of JGF on OC inhibition and OB differentiation in a C3H10T1/2-RAW264.7 co-culture system. The mechanism of JGF was studied by network pharmacology and validated using western blot, immunofluorescence (IF), and ELISA. Following that, the active ingredients of JGF were explored through a chemotype-assembly approach, activity evaluation, and LC-MS/MS analysis.

RESULTS

JGF inhibited bone resorption in murine osteoporosis without compromising the OCOB coupling effect on bone formation. In vitro assays showed that JGF preserved the coupling effect of OC on OB differentiation by maintaining the secretion of OC-derived coupling factors. Network analysis predicted STAT3 as a key regulation point for JGF to exert anti-osteoporosis effect. Further validation assays confirmed that JGF upregulated p-STAT3(Ser727) and its regulatory factors IL-2 in RANKL-induced RAW264.7 cells. Moreover, 23 components in JGF with anti-OC activity identified by chemotype-assembly approach and verification experiments. Notably, six compounds, including ophiopogonin D, ginsenoside Re, ginsenoside Rf, ginsenoside Rg3, ginsenoside Ro, and ononin were identified as OC-coupling compounds.

CONCLUSION

This study first reported JGF as an agent that suppresses bone loss without affecting bone formation. The potential coupling mechanism of JGF involves the upregulation of STAT3 by its regulators IL-2. Additionally, the chemotype-assembly approach elucidated the activity compounds present in JGF, offering a novel strategy for developing an anti-resorption agent that preserves bone formation.

Functional Imaging in Musculoskeletal Disorders in Menopause

Menopause-related musculoskeletal (MSK) disorders include osteoporosis, osteoarthritis (OA), sarcopenia and sarco-obesity. This review focuses on the applications of nuclear medicine for the functional imaging of the aforementioned clinical conditions. Bone Scan (BS) with 99mTc-labeled phosphonates, alone or in combination with MRI, can identify "fresh" vertebral collapse due to age-associated osteoporosis and provides quantitative parameters characterized by a good correlation with radiological indices in patients with OA. 18F-NaF PET, particularly when performed by dynamic scan, has given encouraging results for measuring bone turnover in osteoporosis and allows the evaluation of subchondral bone metabolic activity in OA. FDG PET can help discriminate between pathological and nonpathological vertebral fractures, especially by applying appropriate SUV-based thresholds. In OA, it can effectively image inflamed joints and support appropriate clinical management. Preliminary evidences suggest a possible application of FDG in sarco-obesity for the detection and quantification of visceral adipose tissue (VAT). Further studies are needed to better define the role of nuclear medicine in menopause-related MSK disease, especially as regards the possible impact of new radiopharmaceuticals (ie, FAPI and RGD peptides) and recent technological advances (eg, total-body PET/CT scanners).

The role of integrin family in bone metabolism and tumor bone metastasis

Integrins have been the research focus of cell-extracellular matrix adhesion (ECM) and cytokine receptor signal transduction. They are involved in the regulation of bone metabolism of bone precursor cells, mesenchymal stem cells (MSCs), osteoblasts (OBs), osteoclasts (OCs), and osteocytes. Recent studies expanded and updated the role of integrin in bone metabolism, and a large number of novel cytokines were found to activate bone metabolism pathways through interaction with integrin receptors. Integrins act as transducers that mediate the regulation of bone-related cells by mechanical stress, fluid shear stress (FSS), microgravity, hypergravity, extracellular pressure, and a variety of physical factors. Integrins mediate bone metastasis of breast, prostate, and lung cancer by promoting cancer cell adhesion, migration, and survival. Integrin-mediated targeted therapy showed promising prospects in bone metabolic diseases. This review emphasizes the latest research results of integrins in bone metabolism and bone metastasis and provides a vision for treatment strategies.

Targeting integrin pathways: mechanisms and advances in therapy

Integrins are considered the main cell-adhesion transmembrane receptors that play multifaceted roles as extracellular matrix (ECM)-cytoskeletal linkers and transducers in biochemical and mechanical signals between cells and their environment in a wide range of states in health and diseases. Integrin functions are dependable on a delicate balance between active and inactive status via multiple mechanisms, including protein-protein interactions, conformational changes, and trafficking. Due to their exposure on the cell surface and sensitivity to the molecular blockade, integrins have been investigated as pharmacological targets for nearly 40 years, but given the complexity of integrins and sometimes opposite characteristics, targeting integrin therapeutics has been a challenge. To date, only seven drugs targeting integrins have been successfully marketed, including abciximab, eptifibatide, tirofiban, natalizumab, vedolizumab, lifitegrast, and carotegrast. Currently, there are approximately 90 kinds of integrin-based therapeutic drugs or imaging agents in clinical studies, including small molecules, antibodies, synthetic mimic peptides, antibody-drug conjugates (ADCs), chimeric antigen receptor (CAR) T-cell therapy, imaging agents, etc. A serious lesson from past integrin drug discovery and research efforts is that successes rely on both a deep understanding of integrin-regulatory mechanisms and unmet clinical needs. Herein, we provide a systematic and complete review of all integrin family members and integrin-mediated downstream signal transduction to highlight ongoing efforts to develop new therapies/diagnoses from bench to clinic. In addition, we further discuss the trend of drug development, how to improve the success rate of clinical trials targeting integrin therapies, and the key points for clinical research, basic research, and translational research.

Role of Dietary Supplements and Probiotics in Modulating Microbiota and Bone Health: The Gut-Bone Axis

Osteoporosis is characterized by an alteration of bone microstructure with a decreased bone mineral density, leading to the incidence of fragility fractures. Around 200 million people are affected by osteoporosis, representing a major health burden worldwide. Several factors are involved in the pathogenesis of osteoporosis. Today, altered intestinal homeostasis is being investigated as a potential additional risk factor for reduced bone health and, therefore, as a novel potential therapeutic target. The intestinal microflora influences osteoclasts’ activity by regulating the serum levels of IGF-1, while also acting on the intestinal absorption of calcium. It is therefore not surprising that gut dysbiosis impacts bone health. Microbiota alterations affect the OPG/RANKL pathway in osteoclasts, and are correlated with reduced bone strength and quality. In this context, it has been hypothesized that dietary supplements, prebiotics, and probiotics contribute to the intestinal microecological balance that is important for bone health. The aim of the present comprehensive review is to describe the state of the art on the role of dietary supplements and probiotics as therapeutic agents for bone health regulation and osteoporosis, through gut microbiota modulation.

Purification and Characterization of a Novel Calcium-Binding Heptapeptide from the Hydrolysate of Tilapia Bone with Its Osteogenic Activity

In this study, a calcium-binding peptide was obtained by hydrolyzing tilapia bone and its osteogenic activity was evaluated. Animal protease was selected from nine enzymes, and its hydrolysate was purified through preparative and semi-preparative reverse phase high-performance liquid chromatography. The purified peptide was identified as DGPSGPK (656.32 Da) and its calcium-binding capacity reached 111.98 µg/mg. The peptide calcium chelate (DGPSGPK-Ca) was obtained, and its structure was characterized through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and mass spectrometry (MS). The results of XRD and SEM showed that DGPSGPK-Ca was formed as a new compound. The carboxyl and amino groups of Lys and Asp residues may be the chelating sites of DGPSGPK according to the FTIR and MS results. The molecular simulation showed the carbonyl groups of Asp, Pro, Ser, and Lys residues involved in the binding of calcium. The interaction of DGPSGPK and different integrins was evaluated by molecular docking simulation, and the main forces involved were electrostatic interaction forces, hydrogen bonding and hydrophobic interactions. Furthermore, DGPSGPK could inhibit the differentiation of osteoclast and promote the proliferation, differentiation and mineralization of osteoblasts.

Recent Progresses in the Treatment of Osteoporosis

Osteoporosis (OP) is a chronic bone disease characterized by aberrant microstructure and macrostructure of bone, leading to reduced bone mass and increased risk of fragile fractures. Anti-resorptive drugs, especially, bisphosphonates, are currently the treatment of choice in most developing countries. However, they do have limitations and adverse effects, which, to some extent, helped the development of anabolic drugs such as teriparatide and romosozumab. In patients with high or very high risk for fracture, sequential or combined therapies may be considered with the initial drugs being anabolic agents. Great endeavors have been made to find next generation drugs with maximal efficacy and minimal toxicity, and improved understanding of the role of different signaling pathways and their crosstalk in the pathogenesis of OP may help achieve this goal. Our review focused on recent progress with regards to the drug development by modification of Wnt pathway, while other pathways/molecules were also discussed briefly. In addition, new observations made in recent years in bone biology were summarized and discussed for the treatment of OP.

Targeted apoptosis of macrophages and osteoclasts in arthritic joints is effective against advanced inflammatory arthritis

Insufficient apoptosis of inflammatory macrophages and osteoclasts (OCs) in rheumatoid arthritis (RA) joints contributes toward the persistent progression of joint inflammation and destruction. Here, we deliver celastrol (CEL) to selectively induce apoptosis of OCs and macrophages in arthritic joints, with enzyme-responsive nanoparticles (termed PRNPs) composed of RGD modified nanoparticles (termed RNPs) covered with cleavable PEG chains. CEL-loaded PRNPs (CEL-PRNPs) dually target OCs and inflammatory macrophages derived from patients with RA via an RGD-αvβ3 integrin interaction after PEG cleavage by matrix metalloprotease 9, leading to increased apoptosis of these cells. In an adjuvant-induced arthritis rat model, PRNPs have an arthritic joint-specific distribution and CEL-PRNPs efficiently reduce the number of OCs and inflammatory macrophages within these joints. Additionally, rats with advanced arthritis go into inflammatory remission with bone erosion repair and negligible side effects after CEL-PRNPs treatment. These findings indicate potential for targeting chemotherapy-induced apoptosis in the treatment of advanced inflammatory arthritis.

Molecular Signaling Pathways and Essential Metabolic Elements in Bone Remodeling: An Implication of Therapeutic Targets for Bone Diseases

Bone is one of the dynamic tissues in the human body that undergoes continuous remodelling through subsequent actions of bone cells, osteoclasts, and osteoblasts. Several signal transduction pathways are involved in the transition of mesenchymal stem cells into osteoblasts. These primarily include Runx2, ATF4, Wnt signaling and sympathetic signalling. The differentiation of osteoclasts is controlled by M-CSF, RANKL, and costimulatory signalling. It is well known that bone remodelling is regulated through receptor activator of nuclear factor-kappa B ligand followed by binding to RANK, which eventually induces the differentiation of osteoclasts. The resorbing osteoclasts secrete TRAP, cathepsin K, MMP-9 and gelatinase to digest the proteinaceous matrix of type I collagen and form a saucer-shaped lacuna along with resorption tunnels in the trabecular bone. Osteoblasts secrete a soluble decoy receptor, osteoprotegerin that prevents the binding of RANK/RANKL and thus moderating osteoclastogenesis. Moreover, bone homeostasis is also regulated by several growth factors like, cytokines, calciotropic hormones, parathyroid hormone and sex steroids. The current review presents a correlation of the probable molecular targets underlying the regulation of bone mass and the role of essential metabolic elements in bone remodelling. Targeting these signaling pathways may help to design newer therapies for treating bone diseases.

Non-oncological applications of RGD-based single-photon emission tomography and positron emission tomography agents

INTRODUCTION

Non-invasive imaging techniques (especially single-photon emission tomography and positron emission tomography) apply several RGD-based imaging ligands developed during a vast number of preclinical and clinical investigations. The RGD (Arg-Gly-Asp) sequence is a binding moiety for a large selection of adhesive extracellular matrix and cell surface proteins. Since the first identification of this sequence as the shortest sequence required for recognition in fibronectin during the 1980s, fundamental research regarding the molecular mechanisms of integrin action have paved the way for development of several pharmaceuticals and radiopharmaceuticals with clinical applications. Ligands recognizing RGD may be developed for use in the monitoring of these interactions (benign or pathological). Although RGD-based molecular imaging has been actively investigated for oncological purposes, their utilization towards non-oncology applications remains relatively under-exploited.

METHODS AND SCOPE

This review highlights the new non-oncologic applications of RGD-based tracers (with the focus on single-photon emission tomography and positron emission tomography). The focus is on the last 10 years of scientific literature (2009-2020). It is proposed that these imaging agents will be used for off-label indications that may provide options for disease monitoring where there are no approved tracers available, for instance Crohn's disease or osteoporosis. Fundamental science investigations have made progress in elucidating the involvement of integrin in various diseases not pertaining to oncology. Furthermore, RGD-based radiopharmaceuticals have been evaluated extensively for safety during clinical evaluations of various natures.

CONCLUSION

Clinical translation of non-oncological applications for RGD-based radiopharmaceuticals and other imaging tracers without going through time-consuming extensive development is therefore highly plausible. Graphical abstract.

The osteoclast cytoskeleton - current understanding and therapeutic perspectives for osteoporosis

Osteoclasts are giant multinucleated myeloid cells specialized for bone resorption, which is essential for the preservation of bone health throughout life. The activity of osteoclasts relies on the typical organization of osteoclast cytoskeleton components into a highly complex structure comprising actin, microtubules and other cytoskeletal proteins that constitutes the backbone of the bone resorption apparatus. The development of methods to differentiate osteoclasts in culture and manipulate them genetically, as well as improvements in cell imaging technologies, has shed light onto the molecular mechanisms that control the structure and dynamics of the osteoclast cytoskeleton, and thus the mechanism of bone resorption. Although essential for normal bone physiology, abnormal osteoclast activity can cause bone defects, in particular their hyper-activation is commonly associated with many pathologies, hormonal imbalance and medical treatments. Increased bone degradation by osteoclasts provokes progressive bone loss, leading to osteoporosis, with the resulting bone frailty leading to fractures, loss of autonomy and premature death. In this context, the osteoclast cytoskeleton has recently proven to be a relevant therapeutic target for controlling pathological bone resorption levels. Here, we review the present knowledge on the regulatory mechanisms of the osteoclast cytoskeleton that control their bone resorption activity in normal and pathological conditions.

ESR1 Gene Variants Are Predictive of Osteoporosis in Female Patients with Crohn's Disease

Decreased bone mass in patients with inflammatory bowel diseases (IBD) is a clinical problem with extremely severe consequences of osteoporotic fractures. Despite its increasing prevalence and the need for mandatory intervention and monitoring, it is often ignored in IBD patients’ care. Determining the biomarkers of susceptibility to bone mineral density disorder in IBD patients appears to be indispensable. We aim to investigate the impact of estrogen receptor gene (ESR1) gene polymorphisms on bone mineral density (BMD) in patients with ulcerative colitis (UC) and Crohn’s disease (CD), as they may contribute both, to osteoporosis and inflammatory processes. We characterised 197 patients with IBD (97 with UC, 100 with CD), and 41 controls carrying out vitamin D, calcium and phosphorus serum levels, and bone mineral density assessment at the lumbar spine and the femoral neck by dual-energy X-ray absorptiometry (DXA), ESR1 genotyping and haplotype analysis. We observed that women with CD showed the lowest bone density parameters, which corresponded to the ESR1 c.454-397T and c.454-351A allele dose. The ESR1 gene PvuII and XbaI TA (px) haplotype correlated with decreased femoral neck T-score (OR = 2.75, CI = [1.21–6.27], P-value = 0.016) and may be predictive of osteoporosis in female patients with CD.

Bone formation activity of an osteogenic dodecapeptide from blue mussels (Mytilus edulis)

A novel osteogenic dodecapeptide peptide (PIE), IEELEEELEAER, was purified from the protein hydrolysate of blue mussels (Mytilus edulis). PIE was identified using a capillary electrophoresis electrospray ionization-quadrupole-time of flight mass spectrometer. PIE showed a good reduction in the bone loss in ovariectomized mice, and it also increased the bone mineral density of the ovariectomized mice. PIE has a high affinity with integrins (PDB: , ). There are 8 and 12 amino acid residues from PIE that interact with integrins and , respectively. PIE accelerates the transformation of G0/G1 phase cells into G2 M phase cells, which promotes the growth of osteoblasts. PIE (100 μg mL^-1) can enhance alkaline phosphatase (ALP) activity by 26.48% compared with the control, and it also inhibits the growth of osteoclasts and tartrate resistant acid phosphatase (TRAP) activity. Therefore, PIE may contribute to preventing osteoporosis both in vitro and in vivo.

Modulating calcium-mediated NFATc1 and mitogen-activated protein kinase deactivation underlies the inhibitory effects of kavain on osteoclastogenesis and bone resorption

Osteoclasts are responsible for bone resorption during the process of bone remodeling. Increased osteoclast numbers and bone resorption activity are the main factors contributing to bone loss-related diseases such as osteoporosis. Therefore, modulating the formation and function of osteoclasts is critical for the effective treatment of osteolysis and osteoporosis. Kavain is the active ingredient extracted from the root of the kava plant, which possesses known anti-inflammatory properties. However, the effects of kavain on osteoclastogenesis and bone resorption remain unclear. In this study, we found that kavain inhibits receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation and fusion using tartrate-resistant acid phosphatase staining and immunofluorescence. Furthermore, kavain inhibited bone resorption performed by osteoclasts. Using reverse transcription-polymerase chain reaction and western blot analysis, we found that kavain downregulates the expression of osteoclast marker genes, such as nuclear factor of activated T cells, cytoplasmic 1 (Nfatc1), v-atpase d2 (Atp6v0d2), dendrocyte expressed seven transmembrane protein (Dcstamp), matrix metallopeptidase 9 (Mmp9), cathepsin K (Ctsk), and Acp5. Additionally, kavain repressed RANKL-induced calcium oscillations, nuclear factor of activated T cells activation, and mitogen-activated protein kinase phosphorylation, while leaving NF-κB unaffected. We found no effects of kavain on either osteoblast proliferation or differentiation. Besides, kavain inhibited bone loss in ovariectomized mice by suppressing osteoclastogenesis. Collectively, these data suggest a potential use for kavain as a candidate drug for the treatment of osteolytic diseases.

Identification and mechanism evaluation of a novel osteogenesis promoting peptide from Tubulin Alpha-1C chain in Crassostrea gigas

Marine shellfish provides a series of biofunctionality account of its high-protein level. In this study, the osteogenic effect of a novel peptide, YRGDVVPK, from Crassostrea gigas protein hydrolysates on preosteoblast MC3T3-E1 proliferation was examined. Synthetic peptide with 100 nM significantly promoted the proliferation of MC3T3-E1 cells for a treatment of 72 h assayed by MTT method, and which was confirmed by the increase of alkaline phosphatase (ALP) activity. The peptide, YRGDVVPK, was docked with integrin α5β1 (PDB ID: 3VI4), which is a surface receptor of MC3T3-E1. The interaction of the peptide with integrin α5β1 (PDB ID: 3VI4) was analyzed by the molecular modeling algorithm of CDOCKER, which showed a more stable combination than the original ligand. The results suggested the novel peptide could promote the preosteoblast MC3T3-E1 proliferation probably by activating the signaling pathway of MAPK, which is induced through binding with peptide YRGDVVPK.

Bone Loss in Rheumatoid Arthritis: Basic Mechanisms and Clinical Implications

Patients with rheumatoid arthritis (RA) have historically developed progressive damage of articular bone and cartilage, which correlates with disability over time. In addition, these patients are prone to periarticular and systemic bone loss, carrying additional morbidity. In contrast to what is seen in many other rheumatic diseases, the impact of inflammation on bone in RA is uniquely destructive. Loss of articular bone (erosions) and periarticular bone (demineralization) is a result of excessive bone resorption and markedly limited bone formation. There has been tremendous progress in preventing net bone loss in RA with the advent of disease-modifying agents, including biologic agents and small molecules, that both limit inflammation and may have a direct impact on the prevention of cytokine- and antibody-driven osteoclastogenesis. However, repair of existing bone erosions, although feasible, is observed infrequently. Lack of repair is a consequence of suppression of osteoblast function and bone formation by some of the same mechanisms that promote osteoclastogenesis and bone resorption. As new agents are introduced to control inflammation in RA, and novel mechanisms to target synovitis are identified, it may be possible in the future to fully repair damaged bone.