Molecular-Based Treatment Strategies for Osteoporosis: A Literature Review

Resistance Training Modulates the Matrix Metalloproteinase-2 Activity in Different Trabecular Bones in Aged Rats

Background

Aging decreases osteogenic ability, inducing harmful effects on the bone extracellular matrix (ECM), while exercise training has been indicated as a tool to counteract bone disorders related to advancing age. The modulation of bone ECM is regulated by several types of matrix metalloproteinase (MMP); however, MMP-2 activity in different trabecular bones in response to resistance training (RT) has been neglected. Remodeling differs in different bones under the application of the same mechanical loading. Thus, we investigated the effects of 12 weeks of RT on MMP-2 activity in the lumbar vertebra (L6), tibia, and femur of young (3 months) and older rats (21 months).

Methods

Twenty Wistar rats were divided into four groups (five animals per group): young sedentary or trained and older sedentary or trained. The 12-week RT consisted of climbing a 1.1-m vertical ladder three times per week with progressive weights secured to the animals’ tails. The animals were killed 48 h after the end of the experimental period. The MMP-2 activity was assessed by the zymography method.

Results

The aging process induced lower MMP-2 activity in the lumbar vertebrae and tibia (p=0.01). RT upregulated pro, intermediate, and active MMP-2 activity in the tibia of young rats (p=0.001). RT also upregulated pro and active MMP-2 activity in the lumbar vertebrae and tibia with advancing age (p=0.01). There was no significant difference (p>0.05) between groups for MMP-2 of the femur, regardless of age and RT.

Conclusion

The aging process impairs MMP-2 activity, but RT is a potential therapeutic approach to minimize the deleterious effects of ECM degeneration in different aged bones. Distinct MMP-2 responses to exercise training may result in specific remodeling processes.

Brachial-ankle pulse wave velocity is associated with the risk of osteoporosis: a cross-sectional evidence from a Chinese community-based cohort

Background

Association of arterial stiffness and osteoporosis has been well documented in elderly population. However, it is not clear whether they co-progress from the early stages through common mechanisms. The object of this study was to evaluate possible associations between arterial stiffness and osteoporosis by measuring brachial-ankle pulse wave velocity (baPWV) and the Osteoporosis Self-Assessment Tool for Asia (OSTA) index among a healthy population of Chinese aged 40 years and older. Whether baPWV can be used as a predictor of osteoporosis on OSTA was further assessed.

Methods

This study was cross-sectional in design. Of 3984 adults aged 40 years and older in the Yunyan district of Guiyang (Guizhou, China) who underwent both OSTA and baPWV measurements within 1 month, 1407 were deemed eligible for inclusion (women, 1088; men, 319).

Results

The mean baPWV was 1475 ± 302 cm/s (range,766–3459 cm/s). baPWV in 110 individuals with high risk of osteoporosis (OSTA index < − 4) was higher than that of individuals with non-high risk (1733 ± 461 cm/s vs. 1447 ± 304 cm/s, P < 0.001). OSTA index was negatively correlated with baPWV(ρ = − 0.296, P < 0.001) after adjusting for age, sex, body mass index, waist circumference, diastolic blood pressure, and creatinine clearance rate. baPWV was an independent predictor for the presence of high risk of osteoporosis (β = − 0.001, P < 0.001) and was consistent across age and sex subgroups, and the optimal baPWV cutoff value for predicting the presence of high risk of osteoporosis and fracture was 1693 cm/s. The AUC was 0.722 (95% confidence interval [CI], 0.667–0.777; P < 0.001, sensitivity of 52.8% and specificity of 83.6%).

Conclusions

We conclude that arterial stiffness measured by baPWV is well correlated with the severity of osteoporosis evaluated by OSTA. baPWV index may be a valuable tool for identifying individuals with risk of developing osteoporosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-020-02125-3.

PMSA prevents osteoclastogenesis and estrogen-dependent bone loss in mice

Excessive bone resorption mediated by mature osteoclasts can cause osteoporosis, leading to fragility fractures. Therefore, an effective therapeutic strategy for anti-osteoporosis drugs is the reduction of osteoclast activity. In this study, the osteoclast inhibitory activity of a novel compound, N-phenyl-methylsulfonamido-acetamide (PMSA), was examined. PMSA treatment inhibited receptor activator of nuclear factor kappa B ligand (RNAKL)-induced osteoclast differentiation in bone marrow-derived macrophage cells (BMMs). We investigated two PMSAs, N-2-(3-acetylphenyl)-N-2-(methylsulfonyl)-N-1-[2-(phenylthio)phenyl] glycinamide (PMSA-3-Ac), and N-2-(5-chloro-2-methoxyphenyl)-N-2-(methylsulfonyl)-N-1-[2-(phenylthio)phenyl]glycinamide (PMSA-5-Cl), to determine their effects on osteoclast differentiation. PMSAs inhibited the signaling pathways at the early stage. PMSA-3-Ac inhibited tumor necrosis factor receptor-associated factor 6 (TRAF6) expression, whereas PMSA-5-Cl suppressed the mitogen-activated protein kinase (MAPK) signaling pathways. However, both PMSAs inhibited the master transcription factor, nuclear factor of activated T cell cytoplasmic-1 (NFATc1), by blocking nuclear localization. An in vivo study of PMSAs was performed in an ovariectomized (OVX) mouse model, and PMSA-5-Cl prevented bone loss in OVX mice. Therefore, our results suggested that PMSAs, specifically PMSA-5-Cl, may serve as a potential therapeutic agent for postmenopausal osteoporosis.

Integration of Network Pharmacology and Experimental Validation to Explore the Pharmacological Mechanisms of Zhuanggu Busui Formula Against Osteoporosis

Osteoporosis (OP) is a common skeletal disease, characterized by decreased bone formation and increased bone resorption. As a novel Chinese medicine formula, Zhuanggu Busui formula (ZGBSF) has been proved to be an effective prescription for treating OP in clinic, however, the pharmacological mechanisms underlying the beneficial effects remain obscure. In this study, we explored the pharmacological mechanisms of ZGBSF against OP via network pharmacology analysis coupled with in vivo experimental validation. The results of the network pharmacology analysis showed that a total of 86 active ingredients and 164 targets of ZGBSF associated with OP were retrieved from the corresponding databases, forming an ingredient-target-disease network. The protein-protein interaction (PPI) network manifested that 22 core targets, including Caspase-3, BCL2L1, TP53, Akt1, etc, were hub targets. Moreover, functional enrichment analyses revealed that PI3K-Akt and apoptosis signalings were significantly enriched by multiple targets and served as the targets for in vivo experimental study validation. The results of animal experiments revealed that ZGBSF not only reversed the high expression of Caspase-3, Bax, Prap, and low expression of Bcl-2 in osteoblasts of the OP mouse model but also contributed to the phosphorylation of Akt1 and expression of PI3K, thereby promoting osteogenesis and ameliorating the progression of OP. In conclusion, this study systematically and intuitively illustrated that the possible pharmacological mechanisms of ZGBSF against OP through multiple ingredients, targets, and signalings, and especially the inhibition of the apoptosis and the activation of PI3K-Akt signaling.

Zanthoxylum piperitum alleviates the bone loss in osteoporosis via inhibition of RANKL-induced c-fos/NFATc1/NF-κB pathway

BACKGROUND

The fruit of Zanthoxylum piperitum (ZP) is an herbal medicine as well as a spice agent in Asia to treat carminative, stomachic, anthelmintic and degenerative diseases. Z. piperitum was reported to have anti-oxidant, anti-inflammatory, anti-osteoarthritic and osteosarcoma proliferation-control effects.

PURPOSE AND STUDY DESIGN

This study was conducted to determine the anti-osteoporotic effects and mechanisms of action of ZP.

METHODS

Female ICR mice underwent ovariectomies (OVX) and were orally administered ZP at 1, 10 and 100 mg/kg for 6 weeks. The femoral and tibial bones were assessed by dual-energy X-ray absorptiometry and histology to analyze the bone mineral density (BMD) and the number of osteoclasts. Raw 264.7 cells were stimulated by 100 ng/ml receptor activator of nuclear factor-κB ligand (RANKL) for 7 days in the presence of ZP. RANKL-induced signaling molecules were analyzed in osteoclasts.

RESULTS

The levels of femoral and tibial BMD were significantly increased by ZP administration. Serum biomarkers such as osteocalcin, calcium, alkaline phosphatase and bone-specific alkaline phosphatase concentrations were markedly recovered to normal levels in ZP-treated osteoporotic mice. In addition, the number of osteoclasts in the head, trochanter and body of the femur was obviously decreased in the ZP treatment groups. Moreover, ZP treated-cells showed a reduction in the number of TRAP-positive multinuclear cells in RANKL-stimulated Raw 264.7 cells. ZP decreased the RANKL-activated NFATc1 and c-fos, transcription factors of osteoclast formation. The nuclear translocation of NF-κB and phosphorylation of ERK42/44 were inhibited by the ZP treatment in RANKL-induced osteoclasts.

CONCLUSION

Collectively, ZP exerts its inhibitory effect against bone resorption by regulating RANKL-mediated c-fos/NFATc1/NF-κB in osteoclast. ZP may prove to be a therapeutic agent for osteoporosis.

Exercise as an Adjuvant to Cartilage Regeneration Therapy

This article provides a brief review of the pathophysiology of osteoarthritis and the ontogeny of chondrocytes and details how physical exercise improves the health of osteoarthritic joints and enhances the potential of autologous chondrocyte implants, matrix-induced autologous chondrocyte implants, and mesenchymal stem cell implants for the successful treatment of damaged articular cartilage and subchondral bone. In response to exercise, articular chondrocytes increase their production of glycosaminoglycans, bone morphogenic proteins, and anti-inflammatory cytokines and decrease their production of proinflammatory cytokines and matrix-degrading metalloproteinases. These changes are associated with improvements in cartilage organization and reductions in cartilage degeneration. Studies in humans indicate that exercise enhances joint recruitment of bone marrow-derived mesenchymal stem cells and upregulates their expression of osteogenic and chondrogenic genes, osteogenic microRNAs, and osteogenic growth factors. Rodent experiments demonstrate that exercise enhances the osteogenic potential of bone marrow-derived mesenchymal stem cells while diminishing their adipogenic potential, and that exercise done after stem cell implantation may benefit stem cell transplant viability. Physical exercise also exerts a beneficial effect on the skeletal system by decreasing immune cell production of osteoclastogenic cytokines interleukin-1β, tumor necrosis factor-α, and interferon-γ, while increasing their production of antiosteoclastogenic cytokines interleukin-10 and transforming growth factor-β. In conclusion, physical exercise done both by bone marrow-derived mesenchymal stem cell donors and recipients and by autologous chondrocyte donor recipients may improve the outcome of osteochondral regeneration therapy and improve skeletal health by downregulating osteoclastogenic cytokine production and upregulating antiosteoclastogenic cytokine production by circulating immune cells.

Genetic-Code-Expansion Strategies for Vaccine Development

By providing long-term protection against infectious diseases, vaccinations have significantly reduced death and morbidity worldwide. In the 21st century, (bio)technological advances have paved the way for developing prophylactic vaccines that are safer and more effective as well as enabling the use of vaccines as therapeutics to treat human diseases. Here, we provide a focused review of the utility of genetic code expansion as an emerging tool for the development of vaccines. Specifically, we discuss how the incorporation of immunogenic noncanonical amino acids can aid in eliciting immune responses against adverse self-proteins and highlight the potential of an expanded genetic code for the construction of replication-incompetent viruses. We close the review by discussing the future prospects and remaining challenges for the application of these approaches in the development of both prophylactic and therapeutic vaccines in the near future.

Molecular Mechanisms and Emerging Therapeutics for Osteoporosis

Osteoporosis is the most common chronic metabolic bone disease. It has been estimated that more than 10 million people in the United States and 200 million men and women worldwide have osteoporosis. Given that the aging population is rapidly increasing in many countries, osteoporosis could become a global challenge with an impact on the quality of life of the affected individuals. Osteoporosis can be defined as a condition characterized by low bone density and increased risk of fractures due to the deterioration of the bone architecture. Thus, the major goal of treatment is to reduce the risk for fractures. There are several treatment options, mostly medications that can control disease progression in risk groups, such as postmenopausal women and elderly men. Recent studies on the basic molecular mechanisms and clinical implications of osteoporosis have identified novel therapeutic targets. Emerging therapies targeting novel disease mechanisms could provide powerful approaches for osteoporosis management in the future. Here, we review the etiology of osteoporosis and the molecular mechanism of bone remodeling, present current pharmacological options, and discuss emerging therapies targeting novel mechanisms, investigational treatments, and new promising therapeutic approaches.

Chronic Electrical Stimulation of the Superior Laryngeal Nerve in the Rat: A Potential Therapeutic Approach for Postmenopausal Osteoporosis

Electrical stimulation of myelinated afferent fibers of the superior laryngeal nerve (SLN) facilitates calcitonin secretion from the thyroid gland in anesthetized rats. In this study, we aimed to quantify the electrical SLN stimulation-induced systemic calcitonin release in conscious rats and to then clarify effects of chronic SLN stimulation on bone mineral density (BMD) in a rat ovariectomized disease model of osteoporosis. Cuff electrodes were implanted bilaterally on SLNs and after two weeks recovery were stimulated (0.5 ms, 90 microampere) repetitively at 40 Hz for 8 min. Immunoreactive calcitonin release was initially measured and quantified in systemic venous blood plasma samples from conscious healthy rats. For chronic SLN stimulation, stimuli were applied intermittently for 3-4 weeks, starting at five weeks after ovariectomy (OVX). After the end of the stimulation period, BMD of the femur and tibia was measured. SLN stimulation increased plasma immunoreactive calcitonin concentration by 13.3 ± 17.3 pg/mL (mean ± SD). BMD in proximal metaphysis of tibia (p = 0.0324) and in distal metaphysis of femur (p = 0.0510) in chronically SLN-stimulated rats was 4-5% higher than that in sham rats. Our findings demonstrate chronic electrical stimulation of the SLNs produced enhanced calcitonin release from the thyroid gland and partially improved bone loss in OVX rats.

Osteoclast Multinucleation: Review of Current Literature

Multinucleation is a hallmark of osteoclast maturation. The unique and dynamic multinucleation process not only increases cell size but causes functional alterations through reconstruction of the cytoskeleton, creating the actin ring and ruffled border that enable bone resorption. Our understanding of the molecular mechanisms underlying osteoclast multinucleation has advanced considerably in this century, especially since the identification of DC-STAMP and OC-STAMP as “master fusogens”. Regarding the molecules and pathways surrounding these STAMPs, however, only limited progress has been made due to the absence of their ligands. Various molecules and mechanisms other than the STAMPs are involved in osteoclast multinucleation. In addition, several preclinical studies have explored chemicals that may be able to target osteoclast multinucleation, which could enable us to control pathogenic bone metabolism more precisely. In this review, we will focus on recent discoveries regarding the STAMPs and other molecules involved in osteoclast multinucleation.

Circular RNA hsa_circ_0076690 acts as a prognostic biomarker in osteoporosis and regulates osteogenic differentiation of hBMSCs via sponging miR-152

OBJECTIVE

Osteoporosis is the most common skeletal disease world-wide. The aim of this study is to identify potential circRNA biomarkers for osteoporosis diagnosis and treatment, as well as their roles in regulating osteogenic differentiation.

RESULTS

Hsa_circ_0076690 expression was significantly decreased in osteoporosis patients compared to control and showed an acceptable diagnostic value in clinical samples. Subsequently, hsa_circ_0076690 was identified to act as a sponge of miR-152. The expression of hsa_circ_0076690 was gradually increased during osteogenic differentiation while miR-152 showed a decreased expression trend. Moreover, osteogenic differentiation was promoted by hsa_circ_0076690 over-expression and remain unchanged by miR-152/hsa_circ_0076690 co-overexpression.

CONCLUSIONS

In conclusion, our study revealed that hsa_circ_0076690 may act as a potential diagnostic biomarker for osteoporosis patients and hsa_circ_0076690 could regulate osteogenic differentiation of hBMSCs via sponging miR-152.

MATERIALS AND METHODS

A total of 114 participants were enrolled in this study with ethics approvals. CircRNAs were identified by means of RNA-sequencing and qRT-PCR experiment. The clinical significance was measured by ROC curve analysis. Target relationship was validated by luciferase reporter assay. The osteogenic-associated biomarkers and ALP activity were detected by western blots.

Pea protein-derived tripeptide LRW shows osteoblastic activity on MC3T3-E1 cells via the activation of the Akt/Runx2 pathway

Osteoporosis is a bone disease affecting more than 2 million people comprising 1 in 3 women and 1 in 5 men in Canada. One possible approach to prevent this disease is to stimulate the activity of osteoblasts (bone-forming cells) using food protein-derived bioactive peptides. In our previous study, an ACE inhibitory tripeptide LRW (Leu-Arg-Trp) was identified from pea protein. This work aims to investigate the effect of tripeptide LRW on promoting osteoblastic activity. The tripeptide LRW treatment (50 μM) in MC3T3-E1 cells increased cell proliferation (4-fold increase) as indicated by BrdU incorporation assay. Moreover, we found that tripeptide LRW stimulated osteoblastic differentiation by increasing the levels of type 1 collagen (COL1A2; 3-fold increase), alkaline phosphatase (ALP; 4-fold increase), and runt-related transcription factor 2 (Runx2; 2-fold increase) and the activation of the protein kinase B (Akt) signaling pathway. Furthermore, tripeptide LRW increased matrix mineralization as evidenced by Alizarin-S red staining and nodule formation, osteoprotegerin levels (OPG; 2-fold increase), and wound healing based on cell migration assay. Overall, pea protein-derived bioactive peptide LRW can positively modulate the activity of osteoblasts probably via the Akt/Runx2 pathway, indicating its potential use for the prevention of osteoporosis.

New progress in the pharmacology of protocatechuic acid: A compound ingested in daily foods and herbs frequently and heavily

Protocatechuic acid is a natural phenolic acid, which widely exists in our daily diet and herbs. It is also one of the main metabolites of complex polyphenols, such as anthocyanins and proanthocyanins. In recent years, a large number of studies on the pharmacological activities of protocatechuic acid have emerged. Protocatechuic acid has a wide range of pharmacological activities including antioxidant, anti-inflammatory, neuroprotective, antibacterial, antiviral, anticancer, antiosteoporotic, analgesia, antiaging activties; protection from metabolic syndrome; and preservation of liver, kidneys, and reproductive functions. Pharmacokinetic studies showed that the absorption and elimination rate of protocatechuic acid are faster, with glucuronidation and sulfation being the major metabolic pathways. However, protocatechuic acid displays a dual-directional regulatory effect on some pharmacological activities. When the concentration is very high, it can inhibit cell proliferation and reduce survival rate. This review aims to comprehensively summarize the pharmacology, pharmacokinetics, and toxicity of protocatechuic acid with emphasis on its pharmacological activities discovered in recent 5 years, so as to provide more up-to-date and thorough information for the preclinical and clinical research of protocatechuic acid in the future. Moreover, it is hoped that the clinical application of protocatechuic acid can be broadened, giving full play to its characteristics of rich sources, low toxicity and wide pharmacological activites.

Osteoporosis: Pathophysiology and therapeutic options

Osteoporosis is a metabolic bone disease that, on a cellular level, results from osteoclastic bone resorption not compensated by osteoblastic bone formation. This causes bones to become weak and fragile, thus increasing the risk of fractures. Traditional pathophysiological concepts of osteoporosis focused on endocrine mechanisms such as estrogen or vitamin D deficiency as well as secondary hyperparathyroidism. However, research over the last decades provided exiting new insights into mechanisms contributing to the onset of osteoporosis, which go far beyond this. Selected mechanisms such as interactions between bone and the immune system, the gut microbiome, and cellular senescence are reviewed in this article. Furthermore, an overview on currently available osteoporosis medications including antiresorptive and bone forming drugs is provided and an outlook on potential future treatment options is given.

Thermosensitive Polysaccharide Hydrogel As a Versatile Platform for Prolonged Salmon Calcitonin Release and Calcium Regulation

The common pathological characteristic of osteoporosis and hypercalcemia is the disorder of calcium homeostasis. Currently, salmon calcitonin (sCT), a clinical regenerative medicine, is an attractive chioice to regulate calcium metabolism for alleviation of osteoporosis and hypercalcemia. Unfortunately, serum sCT is quickly cleared in vivo, leading to its short half-life. Here, we designed a versatile hydrogel, based on salmon calcitonin-oxidized calcium alginate (sCT-OCA) conjugate and hydroxypropyl chitin (HPCH). The release profile showed that sCT could be released from HPCH hydrogels loaded with sCT-OCA conjugate (sCT-OCA-HPCH) for at least 28 days with conformation stability. The cellular test demonstrated that the biocompatible sCT-OCA-HPCH, compared with sCT formulation, had capacity in up-regulating alkaline phosphatase activity (∼63% increase) and promoting calcium to deposit into extracellular matrix (∼42% increase). These results indicated that thermosensitive sCT-OCA-HPCH hydrogel herein is a versatile platform for many applications such as calcium metabolism regulation, osteoporosis treatment, and hypercalcemia therapy.

Characterization of Dysregulated lncRNA-Associated ceRNA Network Reveals Novel lncRNAs With ceRNA Activity as Epigenetic Diagnostic Biomarkers for Osteoporosis Risk

The altered expression of long non-coding RNAs (lncRNAs) has been implicated in the development and human diseases. However, functional roles and regulatory mechanisms of lncRNA as competing endogenous RNAs (ceRNAs) in osteoporosis and their potential clinical implication for osteoporosis risk are largely unexplored. In this study, we performed integrated analysis for paired expression profiles and regulatory relationships of dysregulated lncRNAs, mRNAs, and miRNAs based on “ceRNA hypothesis,” and constructed an osteoporosis-related dysregulated miRNA-mediated lncRNA–mRNA ceRNA network (DysCeNet) composed of 105 nodes (including eight miRNAs, 24 mRNAs, and 73 lncRNAs) and 515 edges. Functional analysis suggested that the DysCeNet was involved in known osteoporosis or bone metabolism-related biological processes and pathways. Then, we performed random forest-based feature selection for 73 lncRNAs with ceRNA activity and identified 25 of 73 lncRNAs as potential diagnostic biomarkers. A random forest-based classifier composed of 25 lncRNA biomarkers (RF-25lncRNA) was developed for predicting osteoporosis risk. Performance evaluation with the leave-one-out cross-validation (LOOCV) procedure showed that the RF-25lncRNA achieved a good performance in distinguishing high- and low-bone mineral density (BMD) subjects in different osteoporosis datasets. Our study for the first time revealed a global view of lncRNA-associated ceRNA regulation in osteoporosis and provided novel lncRNAs with ceRNA activity as candidate epigenetic diagnostic biomarkers for early detection of osteoporosis risk.

Lycopene and bone: an in vitro investigation and a pilot prospective clinical study

Background

There are several effective therapies for osteoporosis but these agents might cause serious adverse events. Lycopene intake could prevent bone loss, however studies on its effects on bone are scarce. Our aim was to investigate the effects of lycopene on osteoblast cells as well as bone mineral density and bone turnover markers in postmenopausal women.

Methods

We investigated the effect of lycopene on the Wnt/β-catenin and ERK 1/2 pathways, RUNX2, alkaline phosphatase, RANKL and COL1A of Saos-2. We also carried out a pilot controlled clinical study to verify the feasibility of an approach for bone loss prevention through the intake of a lycopene-rich tomato sauce in 39 postmenopausal women.

Results

Lycopene 10 µM resulted in higher β-catenin and phERK1/2 protein Vs the vehicle (p = 0.04 and p = 0.006). RUNX2 and COL1A mRNA was induced by both 5 and 10 µM doses (p = 0.03; p = 0.03 and p = 0.03; p = 0.05) while RANKL mRNA was reduced (p < 0.05). A significant bone density loss was not detected in women taking the tomato sauce while the control group had bone loss (p = 0.002). Tomato sauce intake resulted in a greater bone alkaline phosphatase reduction than the control (18% vs 8.5%, p = 0.03).

Conclusions

Lycopene activates the WNT/β-catenin and ERK1/2 pathways, upregulates RUNX2, alkaline phosphatase, COL1A and downregulates RANKL Saos-2. These processes contributed to prevent bone loss in postmenopausal women.

Osteoporosis: From Molecular Mechanisms to Therapies

Osteoporosis is a common skeletal disorder, occurring as a result of an imbalance between bone resorption and bone formation, with bone breakdown exceeding bone building. Bone resorption inhibitors, e.g., bisphosphonates, have been designed to treat osteoporosis, while anabolic agents such as teriparatide stimulate bone formation and correct the characteristic changes in the trabecular microarchitecture. However, all of these drugs are associated with significant side effects. It is therefore crucial that we continue to research the pathogenesis of osteoporosis and seek novel modes of therapy. This editorial summarizes and discusses the themes of the fifteen articles published in the Special Issue, Osteoporosis: From Molecular Mechanisms to Therapies 2019, as part of the global picture of the current understanding of osteoporosis.

"Bridging the Gap" Everything that Could Have Been Avoided If We Had Applied Gender Medicine, Pharmacogenetics and Personalized Medicine in the Gender-Omics and Sex-Omics Era

Gender medicine is the first step of personalized medicine and patient-centred care, an essential development to achieve the standard goal of a holistic approach to patients and diseases. By addressing the interrelation and integration of biological markers (i.e., sex) with indicators of psychological/cultural behaviour (i.e., gender), gender medicine represents the crucial assumption for achieving the personalized health-care required in the third millennium. However, ‘sex’ and ‘gender’ are often misused as synonyms, leading to frequent misunderstandings in those who are not deeply involved in the field. Overall, we have to face the evidence that biological, genetic, epigenetic, psycho-social, cultural, and environmental factors mutually interact in defining sex/gender differences, and at the same time in establishing potential unwanted sex/gender disparities. Prioritizing the role of sex/gender in physiological and pathological processes is crucial in terms of efficient prevention, clinical signs’ identification, prognosis definition, and therapy optimization. In this regard, the omics-approach has become a powerful tool to identify sex/gender-specific disease markers, with potential benefits also in terms of socio-psychological wellbeing for each individual, and cost-effectiveness for National Healthcare systems. “Being a male or being a female” is indeed important from a health point of view and it is no longer possible to avoid “sex and gender lens” when approaching patients. Accordingly, personalized healthcare must be based on evidence from targeted research studies aimed at understanding how sex and gender influence health across the entire life span. The rapid development of genetic tools in the molecular medicine approaches and their impact in healthcare is an example of highly specialized applications that have moved from specialists to primary care providers (e.g., pharmacogenetic and pharmacogenomic applications in routine medical practice). Gender medicine needs to follow the same path and become an established medical approach. To face the genetic, molecular and pharmacological bases of the existing sex/gender gap by means of omics approaches will pave the way to the discovery and identification of novel drug-targets/therapeutic protocols, personalized laboratory tests and diagnostic procedures (sex/gender-omics). In this scenario, the aim of the present review is not to simply resume the state-of-the-art in the field, rather an opportunity to gain insights into gender medicine, spanning from molecular up to social and psychological stances. The description and critical discussion of some key selected multidisciplinary topics considered as paradigmatic of sex/gender differences and sex/gender inequalities will allow to draft and design strategies useful to fill the existing gap and move forward.

Inhibitory Effects of N-[2-(4-acetyl-1-piperazinyl) phenyl]-2-(2-chlorophenoxy) acetamide on Osteoclast Differentiation In Vitro via the Downregulation of TRAF6

Osteoclasts are poly-nuclear cells that resorb mineral components from old or damaged bone tissue. Primary mononuclear cells are activated by receptor activator of nuclear factor kappa-Β ligand (RANKL) and differentiate into large multinucleated cells. Dysregulation of osteoclast differentiation can lead to pathological bone loss and destruction. Many studies have focused on the development of new molecules to regulate RANKL-mediated signaling. In this study, N-[2-(4-acetyl-1-piperazinyl)phenyl]-2-(2-chlorophenoxy) acetamide (PPOA-N-Ac-2-Cl) led to a significant decrease in the formation of multinucleated tartrate-resistant acid phosphatase (TRAP)-positive cells in a dose-dependent manner, without inducing significant cytotoxicity. PPOA-N-Ac-2-Cl affected the expression of osteoclast-specific marker genes, such as TRAF6, c-fos, DC-STAMP, NFATc1, MMP9, CtsK, and TRAP (Acp5), during RANKL-mediated osteoclastogenesis. Moreover, PPOA-N-Ac-2-Cl significantly attenuated the protein levels of CtsK, a critical protease involved in bone resorption. Accordingly, bone resorption activity and F-actin ring formation decreased in the presence of PPOA-N-Ac-2-Cl. In conclusion, this study shows that PPOA-N-Ac-2-Cl acts as an inhibitor of osteoclast differentiation and may serve as a potential candidate agent for the treatment of osteoclast-related bone diseases by virtue of attenuating bone resorption.

PSTP-3,5-Me Inhibits Osteoclast Differentiation and Bone Resorption

Osteogenesis is an orchestrated process regulated by osteoclastogenesis and osteoblastogenesis. Excessive osteoclastogenesis causes bone diseases, such as osteoporosis. Although a few drugs are effective in osteoporosis treatment, these drugs lead to side effects, including cellulitis, flatulence, and hypocalcemia. In this study, we reported a 2-(N-Phenylmethylsulfonamido)-N-(2-(phenylthio)phenyl)propanamide (PSTP) compound, PSTP-3,5-Me, as a potential therapeutic agent for osteoporosis. Mouse bone marrow-derived macrophages (BMMs) were differentiated into osteoclasts by receptor activator of nuclear factor kappa B ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) in the presence of PSTP-3,5-Me. PSTP-3,5-Me inhibited osteoclast differentiation by reduced tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts, and suppressed the expression of osteoclast marker genes, such as cathepsin K (Ctsk) and TRAP (Acp5). We investigated signaling pathways mediated by RANKL and its receptor, RANK, and found that PSTP-3,5-Me inhibits nucleus translocation of nuclear factor of activated T cell cytoplasmic-1 (NFATc1). Moreover, PSTP-3,5-Me inhibited F-actin ring formation and mineral resorption. Overall, our data suggests that PSTP-3,5-Me attenuates osteoclast differentiation by blocking the activation of NFATc1.