Bone Cell Activity Research Articles

The Impact of Hempseed Consumption on Bone Parameters and Body Composition in Growing Mice

ObjectivesThis study investigated the effect of a diet containing hempseeds (HS), which are rich in polyunsaturated fatty acids and polyphenols, on body composition, bone mineral measurements and epiphyseal plate osteoblast density. MethodsGroups (n = 8 each) of female C57BL/6 mice were fed one of three AIN-93G-based diets (15% HS by weight; 5% HS; 0% HS) from age 5 to 30 weeks. Diets contained ∼16, 18, and 60% total kcals from fat, protein and carbohydrate, respectively. In-vivo whole-body composition and bone mineral density and content were measured every 4 weeks using dual-energy x-ray absorptiometry. Ex-vivo humeri osteoblast density was determined by sectioning bone longitudinally, mounting the sections on slides and staining using alkaline phosphatase. Stain intensity at the epiphyseal plate was ranked independently by 5 evaluators. ANOVA was used to compare outcomes across groups. Linear regression was used to examine the relationship of end-point bone mineral measurements and osteoblast density. ResultsNo differences were seen in bone mineral measurements, lean mass or fat mass across diet groups. Body weight gain did not differ across groups yet mice fed the 15% HS diet consumed significantly more food than those fed the 0% and 5% HS diets (p = 0.0002). Humeri from both HS groups displayed significantly lower osteoblast densities compared to the control group (P < 0.0001). No relationship was seen between osteoblast density and body composition measurements. ConclusionsDiets enriched with 5% and 15% HS supported growth as well as the control diet without significant impacts on whole-body composition, including bone mineral density and content. At the cellular level, however, HS consumption resulted in reduced density of osteoblasts at the epiphyseal plate. These data invite closer examination of bone cell activity and microarchitecture to determine the effect of habitual HS consumption on bone integrity. Funding SourcesInstitute of Cannabis Research at Colorado State University, Pueblo; Idaho State University.

The Impact of Hempseed Consumption on Bone Parameters and Body Composition in Growing Female C57BL/6 Mice.

Optimizing peak bone mass is critical to healthy aging. Beyond the established roles of dietary minerals and protein on bone integrity, fatty acids and polyphenols modify bone structure. This study investigated the effect of a diet containing hempseeds (HS), which are rich in polyunsaturated fatty acids and polyphenols, on bone mineral density, bone cell populations and body composition. Groups (n = 8 each) of female C57BL/6 mice were fed one of three diets (15% HS by weight; 5% HS; 0% HS (control)) from age 5 to 30 weeks. In vivo whole-body composition and bone mineral density and content were measured every 4 weeks using dual-energy X-ray absorptiometry. Ex vivo humeri cell populations in the epiphyseal plate region were determined by sectioning the bone longitudinally, mounting the sections on slides and staining with tartrate-resistant acid phosphatase and alkaline phosphatase stain to identify osteoclasts and osteoblasts, respectively. Mixed models with repeated measures across experimental weeks showed that neither body weight nor body weight gain across weeks differed among groups yet mice fed the 15% HS diet consumed significantly more food and more kilocalories per g body weight gained than those fed the 5% HS and control diets (p < 0.0001). Across weeks, fat mass was significantly higher in the 5% HS versus the control group (p = 0.02). At the end point, whole-body bone mineral content was significantly higher in the control compared to the 5% HS group (p = 0.02). Humeri from both HS groups displayed significantly lower osteoblast densities compared to the control group (p < 0.0001). No relationship was seen between osteoblast density and body composition measurements. These data invite closer examination of bone cell activity and microarchitecture to determine the effect of habitual HS consumption on bone integrity.

Impact of High-Altitude Hypoxia on Bone Defect Repair: A Review of Molecular Mechanisms and Therapeutic Implications.

Reaching areas at altitudes over 2,500–3,000 m above sea level has become increasingly common due to commerce, military deployment, tourism, and entertainment. The high-altitude environment exerts systemic effects on humans that represent a series of compensatory reactions and affects the activity of bone cells. Cellular structures closely related to oxygen-sensing produce corresponding functional changes, resulting in decreased tissue vascularization, declined repair ability of bone defects, and longer healing time. This review focuses on the impact of high-altitude hypoxia on bone defect repair and discusses the possible mechanisms related to ion channels, reactive oxygen species production, mitochondrial function, autophagy, and epigenetics. Based on the key pathogenic mechanisms, potential therapeutic strategies have also been suggested. This review contributes novel insights into the mechanisms of abnormal bone defect repair in hypoxic environments, along with therapeutic applications. We aim to provide a foundation for future targeted, personalized, and precise bone regeneration therapies according to the adaptation of patients to high altitudes.

Investigating the effects of the marine drug Manzamine‐A related to craniofacial development in vitro

Manzamine‐A is a marine‐derived alkaloid which has anti‐viral and anti‐proliferative properties and is currently being investigated for its efficacy in the treatment of certain viruses (malaria, herpes, HIV‐1) and cancers (breast, cervical, colorectal). Manzamine‐A has been found to exert effects via modulation of SIX1 gene expression, a gene critical to craniofacial development via the WNT, NOTCH, and PI3K/AKTpathways. To date little work has focused on Manzamine‐A and how its use may effect craniofacial development. We hypothesize that Manzamine‐A, through SIX1, alters bone cell activity important to craniofacial skeletal development. As Manzamine‐A is a drug that has great potential in a variety of therapeutics, it is critical that we asses potential side effects that this drug could have on both patients and any developmental effects that may occur during use by expectant mothers. We aimed to assess the effects of Manzamine‐A on four cell types, pre‐osteoblasts, osteoblasts, pre‐osteoclasts, and osteoclasts. PCR, qrtPCR, MTS cell viability assays and Caspase 3/7 apoptosis assay were used to test the effects of Manzamine‐A on these cells. We also performed alkaline phosphatase (ALP) and Tartrate Resistant Acid Phosphatase (TRAP) assays to test the function of osteoblasts and osteoclasts respectively. To date we have found that Six‐1 is highly expressed in osteoblasts and their progenitors. In contrast Six‐1 has low expression levels in osteoclasts and their progenitors. Further, osteoblast progenitor cells exhibit great sensitivity to Manzamine‐A treatment exhibited by a significant decrease in cell viability, increase in cellular apoptosis, and decrease in ALP activity. Studies are ongoing for osteoclast lineage cells. Overall our preliminary data suggests Manzamine‐A may have great effects on bone health overall and may disrupt skeletal development if exposed during pregnancy or postnatal development.

Chirality-Induced Bionic Scaffolds in Bone Defects Repair-A Review.

Due to lack of amino sugar with aging, people will suffer from various epidemic bone diseases called "undead cancer" by the World Health Organization. The key problem in bone tissue engineering that is not completely resolved is the repair of critical large-scale bone and cartilage defects. The chirality of the extracellular matrix plays a decisive role in the physiological activity of bone cells and the occurrence of bone tissue, but the mechanism of chirality in regulating cell adhesion and growth is still in the early stage of exploration. The application progress of chirality-induced bionic scaffolds is reviewed here in bone defects repair based on "soft" and "hard" scaffolds. The aim is to summarize the effects of different chiral structures (l-shaped and d-shaped) in the process of inducing bionic scaffolds in bone defects repair. In addition, many technologies and methods as well as issues worthy of special consideration for preparing chirality-induced bionic scaffolds are also introduced. It is expected that this work can provide inspiring ideas for designing new chirality-induced bionic scaffolds and promote the development of chirality in bone tissue engineering.

Development of bone cell microarrays in microfluidic chips for studying osteocyte–osteoblast communication under fluid flow mechanical loading

Bone tissue remodels throughout life in response to mechanical loads. Impaired activities of bone cells (osteocytes, osteoblasts and osteoclasts) result in a disruption of the bone remodelling cycle, which eventually leads to bone disorders such as osteoporosis. To develop efficient therapeutic strategies against bone disorders, new tools are needed to unravel the bone remodelling cycle at the molecular level. Here, we developed a microfluidic platform, which should allow understanding the bone remodelling cycle in much more detail and ultimately be used to discover new therapeutic compounds. We focused specifically on studying cell–cell communication between osteocytes and osteoblasts cells via connexin 43-gap junctions. Therefore, a new cell printing method was developed to create living cellular bone cell arrays in a microfluidic channel. Several cell printing designs where osteocytes and osteoblasts heterotypically interacted at localized interfaces were evaluated. Physical contacts between the bone cells were characterized at high resolution by correlative atomic force microscopy (AFM)—fluorescence microscopy. We demonstrated that the platform is compatible with single-cell mechanostimulation by AFM nanoindentation and subsequent fluorescent analysis of the mechanoresponse. As a proof of concept, we showed the functionality of the platform by analysing the induced in vivo-like Ca++ wave in the printed osteocyte–osteoblast network upon mechanical stimulation by fluid flow shear stress.

Micro-RNA: A Future Approach to Personalized Diagnosis of Bone Diseases.

Osteoporosis is a highly prevalent bone disease worldwide and the most studied bone-associated pathological condition. Although its diagnosis makes use of advanced and clinically relevant imaging and biochemical tools, the information suffers from several limitations and has little or no prognostic value. In this context, circulating micro-RNAs represent a potentially attractive alternative or a useful addition to the diagnostic arsenal and offer a greater prognostic potential than the conventional approaches. These short non-coding RNA molecules act as inhibitors of gene expression by targeting messenger RNAs with different degrees of complementarity, establishing a complex multilevel network, the basis for the fine modulation of gene expression that finally regulates every single activity of a cell. Micro-RNAs may passively and/or actively be released in the circulation by source cells, and being measurable in biological fluids, their concentrations may be associated to specific pathophysiological conditions. Mounting, despite debatable, evidence supports the use of micro-RNAs as markers of bone cell metabolic activity and bone diseases. Indeed, several micro-RNAs have been associated with bone mineral density, fractures and osteoporosis. However, concerns such as absence of comparability between studies and, the lack of standardization and harmonization of the methods, limit their application. In this review, we describe the pathophysiological bases of the association between micro-RNAs and the deregulation of bone cells activity and the processes that led to the identification of potential micro-RNA-based markers associated with metabolic bone diseases.

Bone structural, biomechanical, and histomorphometric characteristics of the hindlimb skeleton in the marsh rice rat (Oryzomys palustris).

The rice rat (Oryzomys palustris) is a nonconventional laboratory rodent species used to model some human bone disorders. However, no studies have been conducted to characterize the postcranial skeleton. Therefore, we aimed to investigate age- and gender-related features of the hindlimb skeleton of this species. We used femurs and tibiae from 94 rats of both genders aged 4-28 weeks. Bone mineral content (BMC), volumetric bone mineral density (vBMD), and biomechanical properties were determined in femurs. In addition, bone histomorphometry of tibiae was conducted to assess bone cell activities and bone turnover over time. Bone length, total metaphysis BMC and vBMD, mid-diaphyseal BMC and vBMD, cortical thickness, and cortical area progressively augmented with age. Whereas the increase in these parameters plateaued at age 16-22 weeks in female rats, they continued to rise to age 28 weeks in male rats. Furthermore, bone strength parameters increased with age, with few differences between genders. We also observed a rapid decrease in longitudinal growth between age 4 and 16 weeks. Whereas young rats had a greater bone formation rate and bone turnover, older rice rats had greater bone volume and trabecular thickness, with no differences between genders. (a) Sexual dimorphism in the rice rat becomes grossly evident at age 16 weeks; (b) the age-related increases in bone mass, structural cortical parameters, and in some biomechanical property parameters plateau at an older age in male than in female rats; and (c) bone growth and remodeling significantly decreased with age irrespective of the gender.

The effect of P2X7R- mediated Ca2+ and MAPK signaling in OPG-induced duck embryo osteoclasts differentiation and adhesive structure damage

Various factors cause animal bone malnutrition disease during intensive culture. Osteoclasts play an important role in regulating bone metabolism disease. Osteoprotegerin (OPG) modulates osteoclast function; however, the mechanism underlying this effect is unknown. Therefore, the present study aimed to explore whether OPG affects duck embryo osteoclast function via purinergic receptor P2X7. OPG significantly inhibited duck embryo osteoclast differentiation and bone resorption, and suppressed F-actin formation. In addition, OPG remarkably impaired duck embryo osteoclasts' adhesive structure. After OPG treatment, the expression of P2X7R significantly reduced, the ATP level and Ca2+-ATPase activity decreased rapidly, and concomitantly suppressed calcium and MAPK signaling. A438079 (a selective P2X7R inhibitor) significantly inhibited duck embryo osteoclast differentiation and bone resorption, and the phosphorylation of Ca2+ regulated proteins (CAM, CAMKII, CAMKIV) and MAPKs (ERK, JNK, and P38) were markedly suppressed. Pretreatment of duck embryo osteoclasts with BzATP, a P2X7R agonist, activated Ca2+ and MAPK signaling. BzATP alleviated OPG-induced duck embryo osteoclast differentiation and adhesive structure damage, and recovered the distribution of adhesion-related proteins in mature duck embryo osteoclasts. Thus, P2RX7-mediated Ca2+ and MAPK signaling has a key function in OPG-induced duck embryo osteoclast differentiation and adhesive structure damage. P2X7R might be an ideal target to treat bone diseases through regulating bone cell activation.

Mutual Modulation Between Extracellular Vesicles and Mechanoenvironment in Bone Tumors.

The bone microenvironment homeostasis is guaranteed by the balanced and fine regulated bone matrix remodeling process. This equilibrium can be disrupted by cancer cells developed in the bone (primary bone cancers) or deriving from other tissues (bone metastatic lesions), through a mechanism by which they interfere with bone cells activities and alter the microenvironment both biochemically and mechanically. Among the factors secreted by cancer cells and by cancer-conditioned bone cells, extracellular vesicles (EVs) are described to exert pivotal roles in the establishment and the progression of bone cancers, by conveying tumorigenic signals targeting and transforming normal cells. Doing this, EVs are also responsible in modulating the production of proteins involved in regulating matrix stiffness and/or mechanotransduction process, thereby altering the bone mechanoenvironment. In turn, bone and cancer cells respond to deregulated matrix stiffness by modifying EV production and content, fueling the vicious cycle established in tumors. Here, we summarized the relationship between EVs and the mechanoenvironment during tumoral progression, with the final aim to provide some innovative perspectives in counteracting bone cancers.

Changes in alkaline phosphate and calcium levels during early mild cognitive impairment, indicating a role for bone in the progression of Alzheimer’s disease

AbstractBackgroundOver 50 million people worldwide have dementia, one of its most common form being Alzheimer’s disease. It’s one of the top ten leading causes of death attributing to the extraneuronal effects in the bone, skeletal muscle, liver, kidney, and heart. Falls and fractures are one of the predominant causes of mortality in AD patients, indicating the cross talk between the bone and brain during AD. Women with lower femoral BMD were two times more risk‐prone to develop AD than women with higher BMD and this was found to be independent of other risk factors of AD. In this study, we are investigating the changes in the bone markers during early stages of the AD.MethodThe Alzheimer’s Disease Neuroimaging Initiative(ADNI) is a multisite, longitudinal study of normal cognitive aging, early Mild cognitive impairment(EMCI), late MCI and AD individuals, wherein specific recruitment methods are used to recruit participants. We analyzed data from the ADNI‐1, ADNIGO and ADNI‐1 focusing on the relationships between the severity of dementia (mini‐mental state scores), the clinical musculoskeletal findings, and the laboratory data from these participants, which included fluid biomarkers. A total of 1765 patients were included, 57% male and 43% female.ResultWe observed in females that there was robust decrease in the alkaline phosphate levels in EMCI group compared to normal cognitive group, whereas a significant increase in alkaline phosphate levels between EMCI and AD groups. The higher alkaline phosphate levels at EMCI indicates the activity of bone cells and thus bone remodeling. In males, there was a significant reduction in the alkaline phosphate levels during EMCI when compared to cognitive normal groups; however, alkaline phosphate levels were significantly increased both in LMCI and AD groups when compared to EMCI group. Also, in males, there was significant decrease in the calcium levels from cognitive normal group to EMCI group, which was further significantly reduced in the AD groups. However, there was no change in calcium across the groups in the females.ConclusionDetecting changes in the bone biomarkers early on, will help in better management of AD, thereby improving the quality of life in these patients.

In Sickness and in Health: The Oxygen Reactive Species and the Bone

Oxidative stress plays a central role in physiological and pathological bone conditions. Its role in signalment and control of bone cell population differentiation, activity, and fate is increasingly recognized. The possibilities of its use and manipulation with therapeutic goals are virtually unending. However, how redox balance interplays with the response to mechanical stimuli is yet to be fully understood. The present work summarizes current knowledge on these aspects, in an integrative and broad introductory perspective.

Femoral µCT Analysis, Mechanical Testing and Immunolocalization of Bone Proteins in β-Hydroxy β-Methylbutyrate (HMB) Supplemented Spiny Mouse in a Model of Pregnancy and Lactation-Associated Osteoporosis.

A metabolite of leucine, ß-hydroxy-ß-methylbutyrate (HMB), used as a dietary supplement effects muscle tissue gain and bone tissue quality. Since there are no studies on the effects of HMB during pregnancy yet, the aim of the current study was to determine the effects of HMB supplementation during pregnancy on osteoporotic bone quality postpartum and post-lactation using spiny mice (Acomys cahirinus) as the animal models. The six-month-old dams were divided into four groups: pregnant and lactating controls, and pregnant and lactating HMB-treated (during the second trimester of pregnancy) females. The intensity of the immunoreaction of osteocalcin (OC), osteoprotegerin (OPG), bone morphogenetic protein 2 (BMP-2), tissue inhibitor of metalloproteinases 2 (TIMP-2), matrix metalloproteinase 8 and 13 (MMP-8 and MMP-13) and proteins involved in bone turnover, was measured in femoral trabecular and compact bone, as well as in the hyaline and epiphyseal cartilage of the femora. The analysis of the trabecular bone microarchitecture showed that the administration of HMB to pregnant females, by influencing the proteins responsible for bone cell activity and collagen remodeling, can provide protection from bone loss. Based on the results of the current study it can be assumed that HMB administration to pregnant females has a more positive impact on trabecular than compact bone.

Estimation of Bone Trace Elements Following Prolonged Every-other Day Feeding in C57BL/6 Male and Female Mice

The purpose of this study was to examine the effect of prolonged every-other day (EOD) feeding on bone trace elements. Four-week old C57BL/6 female (n = 12) and male (n = 12) mice were employed in this experiment. Animals were assigned to four groups: ad libitum—AL (males and females), EOD fed (males, females). After 9 months, the mice were sacrificed. Long bones (humerus and radius) were isolated and prepared for analysis using inductively coupled plasma optical emission spectrometry to determine the Fe, Zn, Mo, Co, Cu, Mn, Cr contents. Estimation of cathepsin K expression on bone slides was performed to determine the activity of osteoclasts in bones of EOD- and AL-fed animals. Higher content of Fe in EOD-fed females compared to AL-fed females was found. In EOD-fed males, a significantly higher amount of Mo (p < 0.005) and Co (p < 0.05) in comparison to AL-fed males was noted. Gender differences in amounts of trace elements in control AL-fed males vs. females were observed. EOD feeding influences the amount of some trace elements in long bones of female and male C57BL/6 mice. However, this is not influenced by the activity of bone cells.

Antitumor Effect of Cabozantinib in Bone Metastatic Models of Renal Cell Carcinoma.

Simple SummaryBone metastasis is a common and devastating feature of advanced renal cancer. Skeletal metastases are very destructive in patients with renal cell carcinoma (RCC), compromising the bone integrity and leading to fractures, pain, nerve compressions and hypercalcemia, with a negative impact on patient survival. Cabozantinib is a receptor tyrosine kinase inhibitor approved for the treatment of advanced RCC patients. Recently, preclinical studies demonstrated that cabozantinib is able to also modulate bone cell activity. To understand whether and how the antitumor activity of cabozantinib could be influenced by the bone microenvironment, in vitro co-culture models of renal cancer cells and osteoblasts (OBs) were developed to reproduce the bidirectional interplay between tumor cells and bone. The data showed that cabozantinib preserves its efficacy in these coculture models and exerts an additional indirect antitumor activity mediated by OBs. Indeed, cabozantinib is able to inhibit specific OB proliferative signals that, in turn, could affect RCC cell growth. To elucidate how OBs stimulate RCC cell growth could be useful in designing novel and more effective anticancer strategies to improve the efficacy of the existing treatments.Background: The presence of bone metastases in renal cell carcinoma (RCC) negatively affects patients’ survival. Data from clinical trials has highlighted a significant benefit of cabozantinib in bone metastatic RCC patients. Here, we evaluated the antitumor effect of cabozantinib in coculture models of renal cell carcinoma (RCC) and osteoblasts (OBs) to investigate whether and how its antiproliferative activity is influenced by OBs. Methods: Bone/RCC models were generated, coculturing green fluorescent protein (GFP)-tagged Caki-1 and 786-O cells with human primary OBs in a “cell–cell contact” system. RCC proliferation and the OB molecular profile were evaluated after the cabozantinib treatment. Results: The Caki-1 cell proliferation increased in the presence of OBs (p < 0.0001), while the 786-O cell growth did not change in the coculture with the OBs. The cabozantinib treatment reduced the proliferation of both the Caki-1 (p < 0.0001) and 786-O (p = 0.03) cells cocultured with OBs. Intriguingly, the inhibitory potency of cabozantinib was higher when Caki-1 cells grew in presence of OBs compared to a monoculture (p < 0.001), and this was similar in 786-O cells alone or cocultured with OBs. Moreover, the OB pretreatment with cabozantinib “indirectly” inhibited Caki-1 cell proliferation (p = 0.040) without affecting 786-O cell growth. Finally, we found that cabozantinib was able to modulate the OB gene and molecular profile inhibiting specific proliferative signals that, in turn, could affect RCC cell growth. Conclusions: Overall, the “direct” effect of cabozantinib on OBs “indirectly” increased its antitumor activity in metastatic RCC Caki-1 cells but not in the primary 786-O model.

Preparation of Mg/PCL electrospun membranes and preliminary study

Magnesium (Mg) metal and its alloy degradation product magnesium ion (Mg2+) can stimulate the metabolic activity of bone cells, which is beneficial to bone growth and healing. With biodegradable polycaprolactone (PCL) and magnesium particles as raw materials, electrospinning technology is used to prepare electrospun membrane materials doped with magnesium particles. Meanwhile, the scanning electron microscope, X-ray diffraction analysis technology and microcomputer-controlled electronic universal testing machine are adopted to analyze the physical and chemical properties of the material. The biocompatibility of electrospun membranes and their potential to induce osteogenic differentiation of human dental pulp stem cells (hDPSCs) were evaluated by in vitro cell experiments. The results showed that magnesium/PCL electrospun membranes doped with magnesium particles were successfully prepared with electrospinning technology, and the material has a good porous structure. Magnesium/PCL electrospun membranes have good biocompatibility and have the potential to induce osteogenic differentiation of hDPSCs. Among them, the effects of 10% magnesium/PCL electrospun membranes were the most obvious. Clinically, these materials provide new ideas for the restoration of alveolar bone defects and provide an experimental basis for the realization of alveolar bone regeneration.

Smoking-Induced Oxidative Stress in Bone: The Effects on Bone Turnover

Despite of clinical evidence of increased incidence of bone diseases amongst smokers as well as worsening recovery in orthopedic surgeries, it is still unclear which pathological mechanisms are induced by smoking and how these events impair bone turnover. Animal models and in vitro studies have been used to better elucidate these questions and smoking-induced oxidative stress have been pointed as playing crucial role in the worsening of bone cells activities leading bone damage. Oxidative stress is a physiological mechanism characterized by an imbalance between oxidants and antioxidants components. This imbalance leads cell damage and consequent release of inflammatory mediators, resulting in structural changes that impair the functionality of compromised organ. In this review, we summarize findings from clinical, animal models and in vitro studies that have elucidated the importance of the oxidative stress induced by smoking in different bone cells activities, leading bone mineral and organic matrix structural changes.

Shaping the bone through iron and iron-related proteins

Well-controlled iron levels are indispensable for health. Iron deficiency is the most common cause of anemia, whereas iron overload, either hereditary or secondary due to disorders of ineffective erythropoiesis, causes widespread organ failure. Bone is particularly sensitive to fluctuations in systemic iron levels as both iron deficiency and overload are associated with low bone mineral density and fragility. Recent studies have shown that not only iron itself, but also iron-regulatory proteins that are mutated in hereditary hemochromatosis can control bone mass. This review will summarize the current knowledge on the effects of iron on bone homeostasis and bone cell activities, and on the role of proteins that regulate iron homeostasis, i.e. hemochromatosis proteins and proteins of the bone morphogenetic protein pathway, on bone remodeling. As disorders of iron homeostasis are closely linked to bone fragility, deeper insights into common regulatory mechanisms may provide new opportunities to concurrently treat disorders affecting iron homeostasis and bone.

Maternal Embryonic Leucine Zipper Kinase Inhibitor OTSSP167 Inhibits Osteoclast Activity and Restores Osteoblast Activity in a Murine Model of Multiple Myeloma Bone Disease

Multiple myeloma bone disease (MMBD) is characterized by an increased osteoclast activity and a decreased osteoblast differentiation in the multiple myeloma (MM) microenvironment, resulting in the development of lytic bone lesions. A large majority of MM patients suffer from MMBD, which not only causes morbidity but also negatively impacts patient survival. The development of novel therapies, ideally with a combined anti-resorptive and bone-anabolic effect, is of great interest because lytic lesions persist with the current standard of care, even in patients in complete remission. We have previously shown that maternal embryonic leucine zipper kinase (MELK) drives a high-risk gene network in MM and that MELK inhibition with OTSSP167 reduces tumor development in the 5TGM.1 model. In the current study, we assessed the effect of OTSSP167 treatment on bone cell activity and the development of MMBD.OTSSP167 inhibited osteoclast activity in vitro by decreasing monocytic progenitor cell viability as well as via a direct anti-resorptive effect on mature osteoclasts in both human (derived from PBMCs) and murine (RAW264.7) cell cultures. In addition, OTSSP167 stimulated matrix deposition and mineralization by human BMSC-TERT osteoblasts in vitro, which coincided with an increased expression of osterix . This combined anti-resorptive and osteoblast-stimulating effect of OTSSP167 resulted in the complete prevention of lytic lesions and bone loss in MM-bearing 5TGM.1 mice, as assessed by micro-computed tomography. OTSSP167 reduced the number of cortical perforations in MM-bearing mice, without affecting cortical thickness. The loss of trabecular bone volume that occurs in MM-bearing mice compared to healthy controls, was completely prevented, due to an increase in the number of trabeculae and a decrease in trabecular separation. Immunohistomorphometric analyses on the femurs of these mice showed that the increase in osteoclast surface observed in MM-bearing mice was completely prevented with OTSSP167 treatment. In addition, OTSSP167 treatment resulted in a recovery of osteoblast and osteoid surface levels.In conclusion, we show that OTSSP167 has a direct anti-MMBD effect in addition to its anti-MM activity, which warrants further clinical development of MELK inhibition in MM. [Display omitted] DisclosuresLudwig:Celgene: Speakers Bureau; Bristol-Meyers: Speakers Bureau; Takeda: Consultancy, Research Funding, Speakers Bureau; AMGEN: Consultancy, Research Funding, Speakers Bureau; Janssen-Cilag: Consultancy, Speakers Bureau; Takeda: Research Funding, Speakers Bureau.

Regulation of Bone Cell Differentiation and Activation by Microbe-Associated Molecular Patterns.

Gut microbiota has emerged as an important regulator of bone homeostasis. In particular, the modulation of innate immunity and bone homeostasis is mediated through the interaction between microbe-associated molecular patterns (MAMPs) and the host pattern recognition receptors including Toll-like receptors and nucleotide-binding oligomerization domains. Pathogenic bacteria such as Porphyromonas gingivalis and Staphylococcus aureus tend to induce bone destruction and cause various inflammatory bone diseases including periodontal diseases, osteomyelitis, and septic arthritis. On the other hand, probiotic bacteria such as Lactobacillus and Bifidobacterium species can prevent bone loss. In addition, bacterial metabolites and various secretory molecules such as short chain fatty acids and cyclic nucleotides can also affect bone homeostasis. This review focuses on the regulation of osteoclast and osteoblast by MAMPs including cell wall components and secretory microbial molecules under in vitro and in vivo conditions. MAMPs could be used as potential molecular targets for treating bone-related diseases such as osteoporosis and periodontal diseases.