Molecular-Based Treatment Strategies for Osteoporosis: A Literature Review

Osteoporosis management-current and future perspectives - A systemic review

Introduction

Osteoporosis is a geriatric metabolic ailment distinguished by low bone mineral density (BMD) and strength with enhanced micro-architectural retrogression of the extracellular matrix, further increasing bone fragility risk. Osteoporotic fractures and associated complications become common in women and men after 55 and 65 years, respectively. The loss in BMD markedly enhances the risk of fracture, non-skeletal injury, and subsequent pain, adversely affecting the quality of life.

Methods

Data summarised in this review were sourced and summarised, including contributions from 2008 to 2023, online from scientific search engines, based on scientific inclusion and exclusion criteria.

Results

Biochemical serum markers such as BALP, collagen, osteocalcin, and cathepsin-K levels can reveal the osteoporotic status. DEXA scan techniques evaluate the whole body's BMD and bone mineral content (BMC), crucial in osteoporosis management. Anabolic and anti-osteoporotic agents are commonly used to enhance bone formation, minimize bone resorption, and regulate remodelling. The challenges and side effects of drug therapy can be overcome by combining the various drug moieties.

Conclusion

The current review discusses the management protocol for osteoporosis, ranging from lifestyle modification, including physical exercise, pharmaceutical approaches, drug delivery applications, and advanced therapeutic possibilities of AI and machine learning techniques to reduce osteoporosis complications and fracture risk.

17β-Estradiol (E2) Activates Matrix Mineralization through Genomic/Nongenomic Pathways in MC3T3-E1 Cells

Estrogen plays an important role in osteoporosis prevention. We herein report the possible novel signaling pathway of 17β-estradiol (E2) in the matrix mineralization of MC3T3-E1, an osteoblast-like cell line. In the culture media-containing stripped serum, in which small lipophilic molecules such as steroid hormones including E2 were depleted, matrix mineralization was significantly reduced. However, the E2 treatment induced this. The E2 effects were suppressed by ICI182,780, the estrogen receptor (ER)α, and the ERβ antagonist, as well as their mRNA knockdown, whereas Raloxifene, an inhibitor of estrogen-induced transcription, and G15, a G-protein-coupled estrogen receptor (GPER) 1 inhibitor, had little or no effect. Furthermore, the E2-activated matrix mineralization was disrupted by PMA, a PKC activator, and SB202190, a p38 MAPK inhibitor, but not by wortmannin, a PI3K inhibitor. Matrix mineralization was also induced by the culture media from the E2-stimulated cell culture. This effect was hindered by PMA or heat treatment, but not by SB202190. These results indicate that E2 activates the p38 MAPK pathway via ERs independently from actions in the nucleus. Such activation may cause the secretion of certain signaling molecule(s), which inhibit the PKC pathway. Our study provides a novel pathway of E2 action that could be a therapeutic target to activate matrix mineralization under various diseases, including osteoporosis.

A 70% Ethanol Neorhodomela munita Extract Attenuates RANKL-Induced Osteoclast Activation and H2O2-Induced Osteoblast Apoptosis In Vitro

The rapid aging of the population worldwide presents a significant social and economic challenge, particularly due to osteoporotic fractures, primarily resulting from an imbalance between osteoclast-mediated bone resorption and osteoblast-mediated bone formation. While conventional therapies offer benefits, they also present limitations and a range of adverse effects. This study explores the protective impact of Neorhodomela munita ethanol extract (EN) on osteoporosis by modulating critical pathways in osteoclastogenesis and apoptosis. Raw264.7 cells and Saos-2 cells were used for in vitro osteoclast and osteoblast models, respectively. By utilizing various in vitro methods to detect osteoclast differentiation/activation and osteoblast death, it was demonstrated that the EN's potential to inhibit RANKL induced osteoclast formation and activation by targeting the MAPKs-NFATc1/c-Fos pathway and reducing H2O2-induced cell death through the downregulation of apoptotic signals. This study highlights the potential benefits of EN for osteoporosis and suggests that EN is a promising natural alternative to traditional treatments.

Inhibition of PPP1R15A alleviates osteoporosis via suppressing RANKL-induced osteoclastogenesis

Osteoporosis results from overactivation of osteoclasts. There are currently few drug options for treatment of this disease. Since the successful development of allosteric inhibitors, phosphatases have become attractive therapeutic targets. Protein phosphatase 1, regulatory subunit 15 A (PPP1R15A), is a stress-responsive protein, which promotes the UPR (unfolded protein response) and restores protein homeostasis. In this study we investigated the role of PPP1R15A in osteoporosis and osteoclastogenesis. Ovariectomy (OVX)-induced osteoporosis mouse model was established, osteoporosis was evaluated in the left femurs using micro-CT. RANKL-stimulated osteoclastogenesis was used as in vitro models. We showed that PPP1R15A expression was markedly increased in BMMs derived from OVX mice and during RANKL-induced osteoclastogenesis in vitro. Knockdown of PPP1R15A or application of Sephin1 (a PPP1R15A allosteric inhibitor in a phase II clinical trial) significantly inhibited osteoclastogenesis in vitro. Sephin1 (0.78, 3.125 and 12.5 μM) dose-dependently mitigated the changes in NF-κB, MAPK, and c-FOS and the subsequent nuclear factor of activated T cells 1 (NFATc1) translocation in RANKL-stimulated BMMs. Both Sephin1 and PPP1R15A knockdown increased the phosphorylated form of eukaryotic initiation factor 2α (eIF2α); knockdown of eIF2α reduced the inhibitory effects of Sephin1 on NFATc1-luc transcription and osteoclast formation. Furthermore, Sephin1 or PPP1R15A knockdown suppressed osteoclastogenesis in CD14+ monocytes from osteoporosis patients. In OVX mice, injection of Sephin1 (4, 8 mg/kg, i.p.) every two days for 6 weeks significantly inhibited bone loss, and restored bone destruction and decreased TRAP-positive cells. This study has identified PPP1R15A as a novel target for osteoclast differentiation, and genetic inhibition or allosteric inhibitors of PPP1R15A, such as Sephin1, can be used to treat osteoporosis. This study revealed that PPP1R15A expression was increased in osteoporosis in both human and mice. Inhibition of PPP1R15A by specific knockdown or an allosteric inhibitor Sephin1 mitigated murine osteoclast formation in vitro and attenuated ovariectomy-induced osteoporosis in vivo. PPP1R15A inhibition also suppressed pathogenic osteoclastogenesis in CD14+ monocytes from osteoporosis patients. These results identify PPP1R15A as a novel regulator of osteoclastogenesis and a valuable therapeutic target for osteoporosis.

The Potential Therapeutic Effects of Platelet-Derived Biomaterials on Osteoporosis: A Comprehensive Review of Current Evidence

Osteoporosis is a chronic multifactorial condition that affects the skeletal system, leading to the deterioration of bone microstructure and an increased risk of bone fracture. Platelet-derived biomaterials (PDBs), so-called platelet concentrates, such as platelet-rich plasma (PRP) and platelet-rich fibrin (PRF), have shown potential for improving bone healing by addressing microstructural impairment. While the administration of platelet concentrates has yielded positive results in bone regeneration, the optimal method for its administration in the clinical setting is still debatable. This comprehensive review aims to explore the systemic and local use of PRP/PRF for treating various bone defects and acute fractures in patients with osteoporosis. Furthermore, combining PRP/PRF with stem cells or osteoinductive and osteoconductive biomaterials has shown promise in restoring bone microstructural properties, treating bony defects, and improving implant osseointegration in osteoporotic animal models. Here, reviewing the results of in vitro and in vivo studies, this comprehensive evaluation provides a detailed mechanism for how platelet concentrates may support the healing process of osteoporotic bone fractures.

Periostin-targeted SDSSD peptide decorated calcium phosphate nanocomposites incorporation with simvastatin for osteoporosis treatment

The limited options of anabolic drugs restrict their application potential in osteoporosis treatment, despite their theoretical superiority in therapeutic efficacy over antiresorptive drugs. As a prevailing strategy, nano-delivery systems could offer a wider choice of anabolic drugs. In this study, calcium phosphate nanocomposites incorporated with simvastatin (Sim) with periostin-targeting ability were designed and prepared for osteoporosis treatment. Carboxymethyl dextran (CMD) as an anionic and hydrophilic dextran derivative was used to stabilize CaP. In addition, periosteum-targeted peptide (SDSSD) was further grafted on CMD to achieve the bone targeting function. In a one-step coordination assembly strategy, hydrophobic anabolic agent Sim and SDSSD-CMD graft (SDSSD-CMD) were incorporated into the CaP nanoparticles forming SDSSD@CaP/Sim nanocomposites. The resulting SDSSD@CaP/Sim possesses uniform size, great short-term stability and excellent biocompatibility. Moreover, SDSSD@CaP/Sim exhibited a reduced release rate of Sim and showed slow-release behaviour. As anticipated, the nanocomposites exhibited bone bonding capacity in both cellular and animal studies. Besides, SDSSD@CaP/Sim achieved obviously enhanced osteoporosis treatment effect compared to direct injection of Simin vivo. Therefore, our findings highlight the potential of SDSSD-incorporated and CaP-based nanocomposites as a viable strategy to enhance the therapeutic efficacy of anabolic drugs for osteoporosis treatment.

Inhibition of Caspase-1-mediated pyroptosis promotes osteogenic differentiation, offering a therapeutic target for osteoporosis

BACKGROUND

Pyroptosis, an emerging inflammatory form of cell death, has been previously demonstrated to stimulate a massive inflammatory response, thus hindering the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Nevertheless, the impact of pyroptosis in thwarting osteogenic differentiation and exacerbating the advancement of osteoporosis (OP) remains enigmatic.

METHODS

We evaluated the expression levels of pyroptosis-associated indicators, including NOD-like receptor family pyrin domain-containing protein 3 (NLRP3), CASPASE-1, IL-1β, and IL-18, in specimens obtained from femoral heads of OP patients, as well as in an ovariectomy-induced mouse model of OP. Subsequently, the precise roles of pyroptosis in osteogenic differentiation were investigated using bioinformatics analysis, alongside morphological and biochemical assessments.

RESULTS

The pivotal pyroptotic proteins, including NLRP3, Caspase-1, IL-1β, and IL-18, exhibited significant upregulation within the bone tissue samples of clinical OP cases, as well as in the femoral tissues of ovariectomy (OVX)-induced mouse OP model, displaying a negatively associated with compromised osteogenic capacity, as represented by lessened bone mass, suppressed expression of osteogenic proteins such as Runt-related transcription factor 2 (RUNX2), Alkaline phosphatase (ALP), Osterix (OSX), and Osteopontin (OPN), and increased lipid droplets. Moreover, bioinformatics analysis substantiated shared gene expression patterns between pyroptosis and OP pathology, encompassing NLRP3, Caspase-1, IL-1β, IL-18, etc. Furthermore, our in vitro investigation using ST2 cells revealed that dexamethasone treatment prominently induced pyroptosis while impeding osteogenic differentiation. Notably, gene silencing of Caspase-1 effectively counteracted the inhibitory effects of dexamethasone on osteogenic differentiation, as manifested by increased ALP activity and enhanced expression of RUNX2, ALP, OSX, and OPN.

CONCLUSION

Our findings unequivocally underscore that inhibition of Caspase-1-mediated pyroptosis promotes osteogenic differentiation, providing a promising therapeutic target for managing OP.

Isobavachalcone inhibits RANKL-induced osteoclastogenesis via miR-193-3p/NF-κB/NFATc1 signaling pathway in BMMs cells

Inhibition of extensive osteoclastogenesis and bone resorption is considered a potential therapeutic target for the treatment of osteoporosis. Isobavachalcone (IBC) is derived from the traditional Chinese herb Psoralea corylifolia Linn. We showed that IBC dose-dependently suppressed receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclastogenesis in bone marrow monocyte/macrophage (BMMs) and osteoclastic bone-resorption function without cytotoxicity at a dose of no more than 8 µmin vitro. Mechanistically, the results of western blot and quantitative real-time polymerase chain reaction (qRT-PCR) indicated that IBC inhibited the RANKL-induced degradation of IκBα and phosphorylation of nuclear factor kappa B (NF-κB) in BMMs, and subsequently downregulated the expression of osteoclastic-specific genes and osteoclastogenesis-related proteins. TRAP staining and qRT-PCR showed that IBC can inhibit osteoclast differentiation by down-regulating the expression of miR-193-3p on osteoclast differentiation. Overall, our findings suggest that IBC may serve as a promising compound for the treatment of osteoporosis and other metabolic bone diseases.

Bioactivity, Molecular Mechanism, and Targeted Delivery of Flavonoids for Bone Loss

Skeletal disabilities are a prominent burden on the present population with an increasing life span. Advances in osteopathy have provided various medical support for bone-related diseases, including pharmacological and prosthesis interventions. However, therapeutics and post-surgery complications are often reported due to side effects associated with modern-day therapies. Thus, therapies utilizing natural means with fewer toxic or other side effects are the key to acceptable interventions. Flavonoids constitute a class of bioactive compounds found in dietary supplements, and their pharmacological attributes have been well appreciated. Recently, flavonoids' role is gaining renowned interest for its effect on bone remodeling. A wide range of flavonoids has been found to play a pivotal role in the major bone signaling pathways, such as wingless-related integration site (Wnt)/β-catenin, bone morphogenetic protein (BMP)/transforming growth factor (TGF)-β, mitogen-activated protein kinase (MAPK), etc. However, the reduced bioavailability and the absorption of flavonoids are the major limitations inhibiting their use against bone-related complications. Recent utilization of nanotechnological approaches and other delivery methods (biomaterial scaffolds, micelles) to target and control release can enhance the absorption and bioavailability of flavonoids. Thus, we have tried to recapitulate the understanding of the role of flavonoids in regulating signaling mechanisms affecting bone remodeling and various delivery methods utilized to enhance their therapeutical potential in treating bone loss.

Composite Separable Microneedles for Transdermal Delivery and Controlled Release of Salmon Calcitonin for Osteoporosis Therapy

A composite separable microneedles (MNs) system consisting of silk fibroin (SF) needle tips and hyaluronic acid (HA) base is developed for transdermal delivery of salmon calcitonin (sCT) for therapy of osteoporosis. Poly(ethylene glycol) (PEG) is used to modulate the conformation structure of SF to achieve controllable sustained release of sCT. The prepared MNs can effectively penetrate the skin stratum corneum. After application to the skin, the HA base is dissolved within 2 min, allowing these SF drug depots to be implanted into the skin for controllable sustained release of sCT. The release kinetics of sCT can be controlled by regulating the conformation of SF with PEG and the interaction between sCT peptide and SF proteins. Compared with traditional needle injection, delivery of sCT using optimized HA-PEG/SF MNs shows better trabecular bone repair for ovariectomized-induced osteoporosis in mice. The proposed MNs system provides a new noninjection strategy for therapy of osteoporosis.

Vitamin D Receptor Gene Polymorphisms Affect Osteoporosis-Related Traits and Response to Antiresorptive Therapy

The present study analyzed the effect of vitamin D receptor (VDR) gene polymorphisms (ApaI, TaqI, BsmI, FokI, and Cdx2) on bone mineral density (BMD), biochemical parameters and bone turnover markers, fracture prevalence, and response to three types of antiresorptive therapy (estrogen-progesterone, raloxifene, and ibandronate) in 356 postmenopausal women from Slovakia. Association analysis revealed a significant effect of BsmI polymorphism on lumbar spine BMD, serum osteocalcin (OC), and β-CrossLaps levels. While ApaI and Cdx2 polymorphisms were associated with OC and alkaline phosphatase, TaqI polymorphism affected all turnover markers. ApaI, TaqI, and BsmI genotypes increased the risk of spinal, radial, or total fractures with odds ratios ranging from 2.03 to 3.17. Each of therapy types evaluated had a beneficial effect on all osteoporosis-related traits; however, the VDR gene affected only ibandronate and raloxifene treatment. ApaI/aa, TaqI/TT, and BsmI/bb genotypes showed a weaker or no response to ibandronate therapy in femoral and spinal BMD. The impact of aforementioned polymorphisms on turnover markers was also genotype dependent. On the contrary, only TaqI and BsmI polymorphisms influenced raloxifene therapy, even only in lumbar spine BMD. These results point to the potential of using the VDR gene in personalized pharmacotherapy of osteoporosis.

Effects of a Functional Ice Cream Enriched with Milk Proteins on Bone Metabolism: A Feasibility Clinical Study and In Vitro Investigation

Background: Milk proteins (MPs) and their derivative whey proteins (WPs) are important components of human diet that might prevent bone loss. We aimed to investigate the effects of MP on the bones of postmenopausal women, along with the effects of WP on osteoblast cells. Methods: We conducted a feasibility controlled clinical study with 62 postmenopausal women who were asked to consume an MP-enriched ice cream. We also investigated the effect of WP on the ERK1/2 and AKT pathways, RUNX2, alkaline phosphatase, RANKL/OPG ratio, and COL1A of Saos-2. Results: After 12 weeks, we found a greater bone mineral density and bone alkaline phosphatase reduction in women who consumed the MP-enriched ice cream compared to the control group (p = 0.03 and p = 0.02, respectively). In Saos-2 cells, WP upregulated ERK1/2 and AKT pathways (p = 0.002 and p = 0.016), cell proliferation (p = 0.03), and osteoblast differentiation markers, along with downregulating RANKL/OPG (p < 0.001). Moreover, the inhibition of ERK1/2 by PD184253 reverted the effects on both the RUNX2 and ALP mRNA expression and cells proliferation (p = 0.028, p = 0.004, and p = 0.003, respectively) when treated with WP. Conclusions: WP upregulates cell proliferation, RUNX2, and alkaline phosphatase through the activation of the ERK1/2 pathways on Saos-2. These mechanisms probably contribute to preventing bone loss in postmenopausal women.

Effects of vitamin D deficiency on blood lipids and bone metabolism: a large cross-sectional study

To investigate the relationship between serum high-density lipoprotein (HDL-C) and spinal bone mineral density (BMD) under different serum 25-hydroxyvitamin D (25 (OH) D) levels in adults over 40 years old and to explore its mechanism. We include participants over the age of 40 with data on HDL-C, 25 (OH) D, spinal BMD, and other variables in the National Health and Nutrition Examination Survey 2007-2010 in the analysis. A weighted multiple linear regression model was used to evaluate the association between serum HDL-C and spinal BMD in different gender, ages, and serum 25 (OH) D levels. A total of 3599 subjects aged ≥ 40 years old were included in this study. Univariate analysis of the complete correction model showed a negative correlation between serum HDL-C and spinal BMD. In the two subgroups of serum 25 (OH) D, we found that the higher the serum HDL-C in the female with serum 25 (OH) D < 75 nmol/L aged 40-59 years old, the lower the total spinal BMD, and a similar relationship was found in the lumbar spine. However, no similar relationship was found in all populations with serum 25 (OH) D ≥ 75 nmol/L and males with serum 25 (OH) D < 75 nmol/L. These results suggest that among Americans over the age of 40, the increase in serum HDL-C is related to decreased BMD of spine only in women aged 40-59 years with vitamin D insufficiency or deficiency.

Gut microbiota and calcium balance

Microorganisms living on the surface and inside the human body play an important role in the physiological activities of the human body. The largest microecosystem in the human body is the gut microbiome. Calcium disorders are found in many diseases. For example, patients with chronic renal insufficiency present with secondary hyperparathyroidism, which is caused by a calcium imbalance in the body. In addition, calcium dysregulation may affect lipid metabolism in the liver through the calmodulator pathway, leading to cirrhosis, etc. Currently, a considerable number of probiotics have been proven to enhance the body's absorption of calcium. This paper reviews the effects of intestinal flora and related factors such as short-chain fatty acids, estrogen, immune factors and vitamin D on calcium balance.

High-Fat Diet Increases Bone Loss by Inducing Ferroptosis in Osteoblasts

Current research suggests that chronic high-fat dietary intake can lead to bone loss in adults; however, the mechanism by which high-fat diets affect the development of osteoporosis in individuals is unclear. As high-fat diets are strongly associated with ferroptosis, whether ferroptosis mediates high-fat diet-induced bone loss was the focus of our current study. By dividing the mice into a high-fat diet group, a high-fat diet + ferroptosis inhibitor group and a normal chow group, mice in the high-fat group were given a high-fat diet for 12 weeks. The mice in the high-fat diet + ferroptosis inhibitor group were given 1 mg/kg Fer-1 per day intraperitoneally at the start of the high-fat diet. Microscopic CT scans, histological tests, and biochemical indicators of ferroptosis were performed on bone tissue from all three groups at the end of the modelling period. Mc3t3-E1 cells were also used in vitro and divided into three groups: high-fat medium group, high-fat medium+ferroptosis inhibitor group, and control group. After 24 hours of incubation in high-fat medium, Mc3t3-E1 cells were assayed for ferroptosis marker proteins and biochemical parameters, and osteogenesis induction was performed simultaneously. Cellular alkaline phosphatase content and expression of osteogenesis-related proteins were measured at day 7 of osteogenesis induction. The results showed that a high-fat diet led to the development of femoral bone loss in mice and that this process could be inhibited by ferroptosis inhibitors. The high-fat diet mainly affected the number of osteoblasts produced in the bone marrow cavity. The high-fat environment in vitro inhibited osteoblast proliferation and osteogenic differentiation, and significant changes in ferroptosis-related biochemical parameters were observed. These findings have implications for the future clinical treatment of bone loss caused by high-fat diets.

Novel QuEChERS-ultra-performance liquid chromatography-atmospheric-pressure chemical ionization tandem mass spectrometry method for the simultaneous determination of vitamin D and vitamin K in vitamin-fortified nanoemulsions

Nanoemulsion is a new vehicle for food fortification. In this study, a simple and reliable method for the simultaneous analysis of vitamins D₂, D₃, K₁, and K₂ in vitamin-fortified nanoemulsions was developed using QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction and ultra-high performance liquid chromatography-atmospheric-pressure chemical ionization tandem mass spectrometry techniques. Response surface methodology was employed to optimize the extraction parameters. The method was validated for the vitamins in terms of LOD (0.03-0.25 μg/L), LOQ (0.10-0.77 μg/L), intra-day (≤4.50%), inter-day precisions (≤6.43%), and accuracy (98.5%-108.0%). The recoveries of the vitamin-fortified nanoemulsion and yogurt were in the ranges of 104.0%-109.2% and 73.3%-85.2%, respectively. The solvent consumption and analysis time were reduced by 5.6 and 3.3 folds, respectively, rendering it superior to the traditional extraction methods established by the Association of Official Analytical Chemists and the Ministry of Food and Drug Safety.

Oat Seedlings Extract Inhibits RANKL-Induced c-Fos/NFATc1 Transcription Factors in the Early Stage of Osteoclast Differentiation

Osteoporosis is a common disease that increases the risk of fractures due to decreased bone density and weakens the bone microstructure. Preventing and diagnosing osteoporosis using the available drugs can be a costly affair with possible side effects. Therefore, natural product-derived therapeutics are promising alternatives. Our study demonstrated that the oat seedlings' extract (OSE) inhibited the receptor activator of the nuclear factor κB ligand (RANKL)-induced osteoclastogenesis from the bone marrow-derived macrophages (BMMs). The OSE treatment significantly attenuated the RANKL-mediated induction of the tartrate-resistant acid phosphatase (TRAP) activity as well as the number of TRAP-positive (TRAP+) multinucleated cells (MNCs) counted through the TRAP staining in a dose-dependent manner. It was also confirmed that the OSE suppressed the formation of the TRAP + MNCs in the early stage of differentiation and not in the middle and late stages. The results of the real-time quantitative polymerase chain reaction (qPCR) and the western blotting showed that the OSE dramatically inhibited the mRNA and protein expressions of the osteoclastogenesis-mediated transcription factors such as the c-Fos and the nuclear factor-activated T cells c1 (NFATc1). In addition, the OSE strongly attenuated the mRNA induction of the c-Fos/NFATc1-dependent molecules such as the TRAP, the osteoclast-associatedimmunoglobulin-like receptor (OSCAR), the dendritic cell-specific transmembrane protein (DC-STAMP), and the cathepsin K. These results suggest that the naturally derived OSE may be useful for preventing bone diseases.

Histone deacetylase 5 is a phosphorylation substrate of protein kinase D in osteoclasts

Protein kinase D (PRKD) family kinases are required for formation and function of osteoclasts. However, the substrates of PRKD in osteoclasts are unknown. To identify PRKD-dependent protein phosphorylation in osteoclasts, we performed a quantitative LC-MS/MS phosphoproteomics screen for proteins showing differential phosphorylation in osteoclasts after treatment with the PRKD inhibitor CRT0066101. We identified 757 phosphopeptides showing significant changes following PRKD inhibition. Among the changes, we found a group of 13 proteins showing decreased phosphorylation at PRKD consensus phosphorylation motifs. This group includes histone deacetylase 5 (HDAC5), which is a previously validated PRKD target. Considering this known interaction, work suggesting HDACs may be important regulators of osteoclasts, and studies suggesting potential functional redundancy between HDACs, we further investigated the relationship between PRKD and class IIa HDACs in osteoclasts. We confirmed that CRT0066101 inhibits phosphorylation of endogenous HDAC5 and to a lesser extent HDAC4, whereas HDAC7 phosphorylation was not affected. Osteoclast cultures from Hdac5 global knockout mice displayed impaired differentiation and reduced ability to resorb bone, while conditional knockout of Hdac4 in osteoclasts showed no phenotype in vitro or in vivo. The inhibitory effect of CRT0066101 was reduced in Hdac5 KO osteoclasts. Together these data indicate that the PRKD/HDAC5 axis contributes to osteoclast formation in vitro and suggest that this pathway may contribute to regulation of skeletal dynamics in vivo.

The impact of sex steroids on osteonecrosis of the jaw

Sex steroid hormones play a major role in bone homeostasis. Therefore, the use of sex hormones or drugs may increase the risk of osteonecrosis of the jaw (ONJ), a complication caused by damaged bone homeostasis. However, few are known the impact of medications changing sex hormone levels on ONJ.

The pathophysiology of ONJ is not clearly understood and many hypotheses exist: cessation of bone remodeling caused by its anti-resorptive effect on osteoclasts; compromised microcirculation due to medication affecting angiogenesis, including bisphosphonate; and impairment of defense mechanism toward local infection.

The use of high-dose intravenous bisphosphonate in cancer patients is associated with a high prevalence of ONJ. Exogenous estrogen or androgen replacement was reported to be associated with ONJ. Polycystic ovarian syndrome (PCOS) patients demonstrate an androgen excess status, and androgen overproduction serves as a protective factor in the bone mineral density of young women. To date, there are no reports of ONJ occurrence due to androgen overproduction. In contrast, few reports on the occurrence of ONJ due to estrogen deficiency induced by drugs, such as selective estrogen receptor modulator (SERM), aromatase inhibitors, and gonadotropin-releasing hormone (GnRH) agonists, are available.

Thus, the role of sex steroids in the development of ONJ is not known. Further studies are required to demonstrate the exact role of sex steroids in bone homeostasis and ONJ progression. In this review, we will discuss the relationship between medication associated with sex steroids and ONJ.

Targeting of Mevalonate-Isoprenoid Pathway in Acute Myeloid Leukemia Cells by Bisphosphonate Drugs

Metabolic reprogramming represents a hallmark of tumorigenesis to sustain survival in harsh conditions, rapid growth and metastasis in order to resist to cancer therapies. These metabolic alterations involve glucose metabolism, known as the Warburg effect, increased glutaminolysis and enhanced amino acid and lipid metabolism, especially the cholesterol biosynthesis pathway known as the mevalonate pathway and these are upregulated in several cancer types, including acute myeloid leukemia (AML). In particular, it was demonstrated that the mevalonate pathway has a pivotal role in cellular transformation. Therefore, targeting this biochemical process with drugs such as statins represents a promising therapeutic strategy to be combined with other anticancer treatments. In the last decade, several studies have revealed that amino-bisphosphonates (BP), primarily used for bone fragility disorders, also exhibit potential anti-cancer activity in leukemic cells, as well as in patients with symptomatic multiple myeloma. Indeed, these compounds inhibit the farnesyl pyrophosphate synthase, a key enzyme in the mevalonate pathway, reducing isoprenoid formation of farnesyl pyrophosphate and geranylgeranyl pyrophosphate. This, in turn, inhibits the prenylation of small Guanosine Triphosphate-binding proteins, such as Ras, Rho, Rac, Rab, which are essential for regulating cell survival membrane ruffling and trafficking, interfering with cancer key signaling events involved in clonal expansion and maturation block of progenitor cells in myeloid hematological malignancies. Thus, in this review, we discuss the recent advancements about bisphosphonates’ effects, especially zoledronate, analyzing the biochemical mechanisms and anti-tumor effects on AML model systems. Future studies will be oriented to investigate the clinical relevance and significance of BP treatment in AML, representing an attractive therapeutic strategy that could be integrated into chemotherapy.

Lycopene prevents bone loss in ovariectomized rats and increases the number of osteocytes and osteoblasts

Osteoporosis is a prevalent disease with a high incidence in women at the onset of menopause mainly because of hormonal changes, genetics, and lifestyle, leading to decreased bone mass and risk of fractures. Maintaining bone mass is a challenge for postmenopausal women, with calcium-rich food intake being essential for bone health. Nevertheless, other nutrients such as carotenoids may influence bone metabolism because of their high antioxidant properties. This study aimed to evaluate the effect of the carotenoid lycopene on bone cells and in the microarchitecture of ovariectomized rats employing in vitro and in vivo assays. After 8 weeks of ovariectomy, femurs were removed to isolate bone marrow mesenchymal cells to be cultured in osteogenic medium (sham and ovariectomized/OVX) or with 1 μmol/L lycopene (OVX/Lyc). There were performed assays for alkaline phosphatase activity and its in situ detection, mineralization nodules, and quantitative expression of genes associated with osteogenesis. Daily ingestion of 10 mg/kg of lycopene by oral gavage for 8 weeks after ovariectomy was conducted for stereological evaluation of the number and volume of osteoblasts, osteoclasts, and osteocytes of femur distal epiphysis and for microtomographic evaluation of the bone microarchitecture of the femoral proximal epiphysis. Data were normalized and analyzed by comparison among the groups using one-way ANOVA followed by post hoc tests with the significance level set out at 5%. Results showed that lycopene promoted an increase in ALP in situ detection as well as a significant increase in mineralized nodules deposition and expression of genes Runx2 and Bglap when compared with the OVX group. The administration by oral gavage of lycopene increased the total number of osteoblasts and osteocytes when compared to sham and ovariectomized groups. Additionally, it decreased the volume and number of osteoclasts and also reduced the volume of osteocytes compared to the sham group. These results suggest that lycopene improves bone cell metabolism and bone remodeling with the onset of osteoporosis. Future studies with different concentrations and periods of administration should be carried out to shed further light on it.

Transcription Factor KLF7 Promotes Osteoclast Differentiation by Suppressing HO-1

Background: Osteoporosis is a common orthopedic disease with high prevalence in patients older than 50 years. Osteoporosis is often detected only after the fracture and is hard to treat. Therefore, it is of great significance to explore the molecular mechanism of the occurrence of osteoporosis.

Methods: The expression of Heme oxygenase-1 (HO-1) in people with different bone mineral density (BMD) was analyzed based on public databases. GenHacncer and JASPAR databases were adopted to search and verify the upstream transcription factor of HO-1. qRT-PCR, western blot and tartrate-resistant acid phosphatase assays were performed to explore the impact of HO-1 and Kruppel-like factor 7 (KLF7) on osteoclast differentiation. Chromatin immunoprecipitation (ChIP) assay confirmed the binding relationship between KLF7 and HO-1. Finally, Hemin, the agonist of HO-1, was applied in rescue assays, thereby verifying the mechanism of KLF7 modulating osteoclast differentiation by HO-1.

Results: Bioinformatics analysis revealed that HO-1 was highly-expressed while KLF7 lowly-expressed in people with high BMD. Besides, a potential binding site of KLF7 was found on the promoter region of HO-1. ChIP assay further manifested the targeting relationship between HO-1 and KLF7. Western blot and TRAP staining unveiled that osteoclast differentiation was suppressed by HO-1, while facilitated by KLF7. Rescue experiments indicated that over-expressed HO-1 could reverse of the promoting effect of KLF7 on osteoclast differentiation.

Conclusion: The study confirmed that osteoclast differentiation was promoted by KLF7 constraining HO-1, thereby facilitating osteoporosis. The cognation of the pathogenesis of osteoporosis was further enriched. New treatment could be developed on this basis.

Metformin Promotes Differentiation and Attenuates H2O2-Induced Oxidative Damage of Osteoblasts via the PI3K/AKT/Nrf2/HO-1 Pathway

At present, the drug treatment of osteoporosis is mostly focused on inhibiting osteoclastogenesis, which has relatively poor effects. Metformin is a drug that can potentially promote osteogenic differentiation and improve bone mass in postmenopausal women. We aimed to detect the molecular mechanism underlying the osteogenic effect of metformin. Our study indicated that metformin obviously increased the Alkaline phosphatase activity and expression of osteogenic marker genes at the mRNA and protein levels. The PI3K/AKT signaling pathway was revealed to play an essential role in the metformin-induced osteogenic process, as shown by RNA sequencing. We added LY294002 to inhibit the PI3K/AKT pathway, and the results indicated that the osteogenic effect of metformin was also blocked. Additionally, the sequencing data also indicated oxidation-reduction reaction was involved in the osteogenic process of osteoblasts. We used H₂O₂ to mimic the oxidative damage of osteoblasts, but metformin could attenuate it. Antioxidative Nrf2/HO-1 pathway, regarded as the downstream of PI3K/AKT pathway, was modulated by metformin in the protective process. We also revealed that metformin could improve bone mass and oxidative level of OVX mice. In conclusion, our study revealed that metformin promoted osteogenic differentiation and H₂O₂-induced oxidative damage of osteoblasts via the PI3K/AKT/Nrf2/HO-1 pathway.

Estrogen-Responsive Gene MAST4 Regulates Myeloma Bone Disease

Our previous data showed that young female multiple myeloma (MM) patients had a low frequency of osteolytic lesions. Based on this clinical observation, we found that estrogen cell signaling played a regulatory role in MM bone disease (MMBD), and the estrogen-responsive gene microtubule-associated serine/threonine kinase family member 4 (MAST4) was a critical factor. The presence of estrogen in cell cultures promoted MAST4 expression in MM cells, while knocking down estrogen receptor 1 (ESR1) inhibited MAST4 expression. Chromatin immunoprecipitation assay suggested a binding site of ESR1 on the MAST4 promoter. Bisphosphonates, such as zoledronic acid (ZOL), which was widely used in MMBD control, could stimulate MAST4 expression in MM cells by promoting ESR1 expression. MAST4 interacted with phosphatase and tensin homolog (PTEN), therefore regulating the PI3K-Akt-mTOR pathway and the expression of downstream cytokines, such as CCL2/3/4. MAST4 knockdown (MAST4-KD) or ESR1 knockdown (ESR1-KD) MM cells had repressed PTEN activity, elevated PI3K-Akt-mTOR activity, and increased CCL2/3/4 expressions. Coculture of MAST4-KD or ESR1-KD MM cells with pre-osteoclasts (pre-OCs) stimulated OC formation in vitro, whereas neutralizing antibodies of CCL2/3/4 attenuated such stimulation. In mouse models, mice inoculated with MAST4-KD or ESR1-KD MM cells had severer MMBD than control knockdown (CTR-KD). The correlations between MAST4 and ESR1 expressions in MMBD, as well as related cell signaling pathways, were confirmed in analyses using gene expression profiles (GEPs) of patients' MM cells. The negative correlation of MAST4 expression and occurrence of MMBD was further validated by patients' immunohistochemical tissue array. Overall, our data suggested that estrogen cell signaling negatively regulated MMBD through MAST4. © 2022 American Society for Bone and Mineral Research (ASBMR).

Pain Intensity and Degree of Disability after Fragility Fractures of the Pelvis

Background and objectives: Fragility fractures of the pelvis (FFP) are of increasing interest lately, being associated with a loss of mobility and affecting the quality of life. The aim of our study was to investigate the effect of FFP on disability and pain in patients, after one year since injury. Materials and Methods: In the study, we included 76 patients diagnosed with FFP, who were admitted to our trauma department between January 2016 and January 2019, and were above 65 years of age. The Von Korff pain intensity and disability scores were calculated in the hospital at 6 months and after 1 year. Results: Fifty-four patients were female (71%), with an average age of 75.9 ± 7.19 years. Twenty-two patients were male (29%) and had a mean age of 77.22 ± 7.33 years. We did not record significant differences regarding age between the men and women (p > 0.05). Significant improvements appeared between the baseline and the 6 month follow-up; the average pain intensity score at 6 months was 44.94 (SD 21.20) (p < 0.001), and the disability score was 54.30 (SD 21.62). The following average pain intensity and disability scores after 12 months were similar to the values at6 months: 44.48 (SD 21.74) for pain intensity and 52.36 (SD 24.53) for disability. The Von Korff pain score at 6 months and after 1 year depends on gender and on the initial Von Korff pain score (p = 0.02). The Von Korff disability score at 6 months depends on gender, the baseline pain score and the baseline disability score (p = 0.001). Conclusions: our patients reported long-lasting pain that had a severe effect on their daily routines, and they could not return to their normal status prior to injury.

Prostaglandin EP4 Selective Agonist AKDS001 Enhances New Bone Formation by Minimodeling in a Rat Heterotopic Xenograft Model of Human Bone

To enhance bone regeneration, the use of bone morphogenetic protein (BMP)-2 is an attractive option. Unfortunately, the dose-dependent side effects prevent its widespread use. Therefore, a novel osteogenic agent using a different mechanism of action than BMP-2 is highly desirable. Previous reports demonstrated that prostaglandin E2 receptor 4 (EP4) agonists have potent osteogenic effects on non-human cells and are one of the potential alternatives for BMP-2. Here, we investigated the effects of an EP4 agonist (AKDS001) on human cells with a rat heterotopic xenograft model of human bone. Bone formation in the xenograft model was significantly enhanced by AKDS001 treatment. Histomorphometric analysis showed that the mode of bone formation by AKDS001 was minimodeling rather than remodeling. In cultured human mesenchymal stem cells, AKDS001 enhanced osteogenic differentiation and mineralization via the cAMP/PKA pathway. In cultured human preosteoclasts, AKDS001 suppressed bone resorption by inhibiting differentiation into mature osteoclasts. Thus, we conclude that AKDS001 can enhance bone formation in grafted autogenous bone by minimodeling while maintaining the volume of grafted bone. The combined use of an EP4 agonist and autogenous bone grafting may be a novel treatment option to enhance bone regeneration. However, we should be careful in interpreting the results because male xenografts were implanted in male rats in the present study. It remains to be seen whether females can benefit from the positive effects of AKDS001 MS by using female xenografts implanted in female rats in clinically relevant animal models.

Three Classes of Antioxidant Defense Systems and the Development of Postmenopausal Osteoporosis

Osteoporosis is a common bone imbalance disease that threatens the health of postmenopausal women. Estrogen deficiency accelerates the aging of women. Oxidative stress damage is regarded as the main pathogenesis of postmenopausal osteoporosis. The accumulation of reactive oxygen species in the bone microenvironment plays a role in osteoblast and osteoclast apoptosis. Improving the oxidative state is essential for the prevention and treatment of postmenopausal osteoporosis. There are three classes of antioxidant defense systems in the body to eliminate free radicals and peroxides including antioxidant substances, antioxidant enzymes, and repair enzymes. In our review, we demonstrated the mechanism of antioxidants and their effect on bone metabolism in detail. We concluded that glutathione/oxidized glutathione (GSH/GSSG) conversion involved the PI3K/Akt-Nrf2/HO-1 signaling pathway and that the antioxidant enzyme-mediated mitochondrial apoptosis pathway of osteoblasts was necessary for the development of postmenopausal osteoporosis. Since the current therapeutic effects of targeting bone cells are not significant, improving the systemic peroxidation state and then regulating bone homeostasis will be a new method for the treatment of postmenopausal osteoporosis.

Gegen Qinlian Decoction ameliorates type 2 diabetes osteoporosis via IGFBP3/MAPK/NFATc1 signaling pathway based on cytokine antibody array

BACKGROUND

Osteoporosis affects more than half the patients with type 2 diabetes mellitus (T2DM). Up to data, there is no effective clinical practice in managing type 2 diabetes osteoporosis (T2DOP) because of its complex pathogenesis. Gegen Qinlian Decoction (GQD) has been used for the long-term management of T2DM. However, the underlying mechanism of GQD in the treatment of T2DOP remains unknown.

PURPOSE

To reveal the role of GQD in T2DOP and its potential therapeutic targets in the management of T2DOP.

STUDY DESIGN

The effect of GQD on T2DOP was observed in db/db mice in four groups: model group, GQD low-dose group (GQD-L), GQD high-dose group (GQD-H), and metformin (positive control) group. C57BL/6J mice were used as the negative control group.

METHODS

Quantitative phytochemical analysis of GQD was performed using high-performance liquid chromatography (HPLC). Micro-CT and hematoxylin-eosin (H&E) staining were used to evaluate bone histomorphometry. To screen for candidate targets of GQD, a cytokine antibody array was used, followed by bioinformatics analysis. Quantitative real-time PCR (qRT-PCR) and western blotting (WB) were used to determine expression levels.

RESULTS

The major active components of GQD were confirmed by HPLC. Micro-CT and H&E staining showed that bone mass was significantly increased in the GQD-H group compared with the model group. Antibody arrays revealed that the expression of insulin-like growth factor binding protein 3 (IGFBP3) was elevated in the GQD-H group. The MAPK pathway was identified using bioinformatics analysis. Additionally, the levels of osteoclastogenesis-related genes, including cathepsin K (Ctsk), acid phosphatase 5 (Acp5), matrix metallopeptidase 9 (Mmp9), and ATPase H+ transporting V0 subunit D2 (Atp6v0d2) were significantly decreased in the GQD-H group. Compared with the model group, high-dosage GQD inhibited phosphorylation of extracellular signal-regulated kinases (ERKs) and P38 mitogen-activated protein kinase (MAPK) and the expression of c-Fos and nuclear factor of activated T cells 1 (NFATc1).

CONCLUSION

GQD plays a protective role in T2DOP by upregulating IGFBP3 expression and downregulating the IGFBP3/MAPK/NFATc1 signaling pathway. IGFBP3 in serum may also be a novel biomarker in the treatment of T2DOP. Our current findings not only expand the application of GQD, but also provide a theoretical basis and guidance for T2DOP.

Effects and mechanisms of natural plant active compounds for the treatment of osteoclast-mediated bone destructive diseases

Bone-destructive diseases, caused by overdifferentiation of osteoclasts, reduce bone mass and quality, and disrupt bone microstructure, thereby causes osteoporosis, Paget's disease, osteolytic bone metastases, and rheumatoid arthritis. Osteoclasts, the only multinucleated cells with bone resorption function, are derived from haematopoietic progenitors of the monocyte/macrophage lineage. The regulation of osteoclast differentiation is considered an effective target for the treatment of bone-destructive diseases. Natural plant-derived products have received increasing attention in recent years due to their good safety profile, the preference of natural compounds over synthetic drugs, and their potential therapeutic and preventive activity against osteoclast-mediated bone-destructive diseases. In this study, we reviewed the research progress of the potential antiosteoclast active compounds extracted from medicinal plants and their molecular mechanisms. Active compounds from natural plants that inhibit osteoclast differentiation and functions include flavonoids, terpenoids, quinones, glucosides, polyphenols, alkaloids, coumarins, lignans, and limonoids. They inhibit bone destruction by downregulating the expression of osteoclast-specific marker genes (CTSK, MMP-9, TRAP, OSCAR, DC-STAMP, V-ATPase d2, and integrin av3) and transcription factors (c-Fos, NFATc1, and c-Src), prevent the effects of local factors (ROS, LPS, and NO), and suppress the activation of various signalling pathways (MAPK, NF-κB, Akt, and Ca²⁺). Therefore, osteoclast-targeting natural products are of great value in the prevention and treatment of bone destructive diseases.

Anti-Osteoporotic Effects of n-trans-Hibiscusamide and Its Derivative Alleviate Ovariectomy-Induced Bone Loss in Mice by Regulating RANKL-Induced Signaling

Osteoporosis is characterized by the deterioration of bone structures and decreased bone mass, leading to an increased risk of fracture. Estrogen deficiency in postmenopausal women and aging are major factors of osteoporosis and are some of the reasons for reduced quality of life. In this study, we investigated the effects of n-trans-hibiscusamide (NHA) and its derivative 4-O-(E)-feruloyl-N-(E)-hibiscusamide (HAD) on receptor activator of nuclear factor kappa-Β (NF-κB) ligand (RANKL)-induced osteoclast differentiation and an ovariectomized osteoporosis mouse model. NHA and HAD significantly inhibited the differentiation of osteoclasts from bone marrow-derived macrophages (BMMs) and the expression of osteoclast differentiation-related genes. At the molecular level, NHA and HAD significantly downregulated the phosphorylation of mitogen-activated protein kinase (MAPK) signaling molecules. However, Akt and NF-κB phosphorylation was inhibited only after NHA or HAD treatment. In the ovariectomy (OVX)-induced osteoporosis model, both NHA and HAD effectively improved trabecular bone structure. C-terminal telopeptide (CTX), a bone resorption marker, and RANKL, an osteoclast stimulation factor, were significantly reduced by NHA and HAD. The tartrate-resistant acid phosphatase (TRAP)-stained area, which indicates the osteoclast area, was also decreased by these compounds. These results show the potential of NHA and HAD as therapeutic agents for osteoporosis.

Osteoporosis therapies and their mechanisms of action (Review)

Osteoporosis is a common disease that affects millions of patients worldwide and is most common in menopausal women. The main characteristics of osteoporosis are low bone density and increased risk of fractures due to deterioration of the bone architecture. Osteoporosis is a chronic disease that is difficult to treat; thus, investigations into novel effective therapeutic methods are required. A number of studies have focused on determining the most effective treatment options for this disease. There are several treatment options for osteoporosis that differ depending on the characteristics of the disease, and these include both well-established and newly developed drugs. The present review focuses on the various drugs available for osteoporosis, the associated mechanisms of action and the methods of administration.

Synthesized Nanorods Hydroxyapatite by Microwave-Assisted Technology for In Vitro Osteoporotic Bone Regeneration through Wnt/β-Catenin Pathway

This research presents an optimal and inexpensive, without any additives, method for the synthesis and sintering of hydroxyapatite (HA) by microwave-assisted technology (MAT) furnace. The target sintering temperature of the furnace (1100 ℃) was held for one and two hours for conventional sintering. With regard to the microwave hybrid sintering, it was held at 100%MW for 20 and 30 min. FTIR, XRD, TGA, SEM/EDS, and TEM were assessed to determine HA phase composition, and structural as well as thermal decomposition behavior. The in vitro effects of sintered HA discs on cultured aged mice-isolated osteoblast cells and hydrocortisone-induced osteoclast cells were assessed by measuring ALP, osteocalcin, TRAP, calcium, and Alizarin red S staining. Moreover, their effects on cell differentiation (CD90 and CD 105 and PARR- ɣ) and death markers (GSK3b, MAPK, and β-catenin) were evaluated. The results demonstrate the production of ≈35 nm crystal-sized pure hydroxyapatite nanorod-like particles with a high degree of crystallinity and no impurities as required for biomedical application. HA increased osteogenesis (ALP, osteocalcin, and calcium) markers and decreased cell resorption markers. In addition, HA nanorods reversed the effect of cortisone on cell differentiation and death markers. In conclusion, microwave hybrid sintered HA is a potential nanomaterial for osteoporotic bone regeneration as HA reversed the cortisone adverse effect on osteoblast cell death through canonical and non-canonical pathways.

Raloxifene Ameliorates Glucosamine-Induced Insulin Resistance in Ovariectomized Rats

Osteoarthritis (OA) and osteoporosis (OP) are common among older women, especially postmenopausal women. Glucosamine (GlcN) is a common medication for OA, but it may induce insulin resistance and β-cell dysfunction, especially if ovarian hormones are lacking. Raloxifene (RLX) is a selective estrogen receptor modulator and also an OP drug. Previously, we found that estrogen could improve GlcN-induced insulin resistance in ovariectomized (OVX) rats. Here, we further hypothesized that RLX, similarly to estrogen, can ameliorate GlcN-induced insulin resistance in OVX rats. We used GlcN to induce insulin resistance in OVX rats as a model for evaluating the protective effects of RLX in vivo. We used a pancreatic β-cell line, MIN-6, to study the mechanisms underlying the effect of RLX in GlcN-induced β-cell dysfunction in vitro. Increases in fasting plasma glucose, insulin, and homeostasis model assessments of insulin resistance in OVX Sprague Dawley rats treated with GlcN were reversed by RLX treatment (n = 8 in each group). Skeletal muscle GLUT-4 increased, liver PEPCK decreased, pancreatic islet hypertrophy, and β-cell apoptosis in OVX rats treated with GlcN was ameliorated by RLX. The negative effects of GlcN on insulin secretion and cell viability in MIN-6 cells were related to the upregulation of reticulum (ER) stress-associated proteins (C/EBP homologous protein, phospho-extracellular signal-regulated kinase, phospho-c-JunN-terminal kinase), the expression of which was reduced by RLX. Pretreatment with estrogen receptor antagonists reversed the protective effects of RLX. GlcN can induce insulin resistance, β-cell dysfunction, and apoptosis in OVX rats and increase ER stress-related proteins in β-cells, whereas RLX can reverse these adverse effects. The effects of RLX act mainly through estrogen receptor α; therefore, RLX may be a candidate drug for postmenopausal women with OA and OP.

Influencing Factors and Molecular Pathogenesis of Sarcopenia and Osteosarcopenia in Chronic Liver Disease

The liver plays a pivotal role in nutrient/energy metabolism and storage, anabolic hormone regulation, ammonia detoxification, and cytokine production. Impaired liver function can cause malnutrition, hyperammonemia, and chronic inflammation, leading to an imbalance between muscle protein synthesis and proteolysis. Patients with chronic liver disease (CLD) have a high prevalence of sarcopenia, characterized by progressive loss of muscle mass and function, affecting health-related quality of life and prognosis. Recent reports have revealed that osteosarcopenia, defined as the concomitant occurrence of sarcopenia and osteoporosis, is also highly prevalent in patients with CLD. Since the differentiation and growth of muscles and bones are closely interrelated through mechanical and biochemical communication, sarcopenia and osteoporosis often progress concurrently and affect each other. Osteosarcopenia further exacerbates unfavorable health outcomes, such as vertebral fracture and frailty. Therefore, a comprehensive assessment of sarcopenia, osteoporosis, and osteosarcopenia, and an understanding of the pathogenic mechanisms involving the liver, bones, and muscles, are important for prevention and treatment. This review summarizes the molecular mechanisms of sarcopenia and osteosarcopenia elucidated to data in hopes of promoting advances in treating these musculoskeletal disorders in patients with CLD.

The Development of Molecular Biology of Osteoporosis

Osteoporosis is one of the major bone disorders that affects both women and men, and causes bone deterioration and bone strength. Bone remodeling maintains bone mass and mineral homeostasis through the balanced action of osteoblasts and osteoclasts, which are responsible for bone formation and bone resorption, respectively. The imbalance in bone remodeling is known to be the main cause of osteoporosis. The imbalance can be the result of the action of various molecules produced by one bone cell that acts on other bone cells and influence cell activity. The understanding of the effect of these molecules on bone can help identify new targets and therapeutics to prevent and treat bone disorders. In this article, we have focused on molecules that are produced by osteoblasts, osteocytes, and osteoclasts and their mechanism of action on these cells. We have also summarized the different pharmacological osteoporosis treatments that target different molecular aspects of these bone cells to minimize osteoporosis.

Bisphosphonate use in children with cerebral palsy

BACKGROUND

Cerebral palsy (CP) is a heterogeneous group of non-progressive disorders of posture or movement, caused by a lesion of the developing brain. Osteoporosis is common in children with cerebral palsy, particularly in children with reduced gross motor function, and leads to an increased risk of fractures. Gross motor function in children with CP can be categorised using a tool called the Gross Motor Function Classification System (GMFCS). Bisphosphonate increases bone mineral density (BMD) and reduces fracture rates. Bisphosphonate is used widely in the treatment of adult osteoporosis. However, the use of bisphosphonate in children with CP remains controversial, due to a paucity of evidence and a lack of recent trials examining the efficacy and safety of bisphosphonate use in this population.

OBJECTIVES

To examine the efficacy and safety of bisphosphonate therapy in the treatment of low BMD or secondary osteoporosis (or both) in children with cerebral palsy (GMFCS Levels III to V) who are under 18 years of age.

SEARCH METHODS

In September 2020, we searched CENTRAL, MEDLINE, Embase, six other databases, and two trial registers for relevant studies. We also searched the reference lists of relevant systematic reviews, trials, and case studies identified by the search, and contacted the authors of relevant studies in an attempt to identify unpublished literature.

SELECTION CRITERIA

All relevant randomised controlled trials (RCTs), and quasi-RCTs, comparing at least one bisphosphonate (given at any dose, orally or intravenously) with placebo or no drug, for the treatment of low BMD or osteoporosis in children up to 18 years old, with cerebral palsy (GMFCS Levels III to V).

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. We were unable to conduct any meta-analyses due to insufficient data, and therefore provide a narrative assessment of the results.

MAIN RESULTS

We found two relevant RCTs (34 participants). Both studies included participants with non-ambulatory CP or CP and osteoporosis. Participants in both studies were similar in severity of CP, age distribution, and sex distribution. The two trials used different bisphosphonate medications and different intervention durations, but further comparison of the interventions was not possible due to a lack of published data from one trial. One trial received funding and support from research, academic, and hospital foundations, with pharmaceutical companies providing components of the calcium and vitamin supplement; the other trial did not report sources of funding. We judged one study at an overall high risk of bias; the other as overall unclear risk of bias.

PRIMARY OUTCOME

Compared to placebo or no treatment, both studies provided very low certainty evidence of improved BMD at least four months post-intervention in children treated with bisphosphonate. Only one study (12 participants) provided sufficient detail to assess a measure of the effect, and reported an improvement at six months post-intervention in lumbar spine z-score (mean difference (MD) 18%, 95% confidence interval (CI) 6.57 to 29.43; very low certainty evidence).

SECONDARY OUTCOMES

Very low certainty evidence from one study found that bisphosphonate reduced serum N-telopeptides (NTX) more than placebo; the other study reported that both bisphosphonate plus alfacalcidol and alfacalcidol alone reduced NTX, but did not compare groups. One study reported inconclusive results between groups for serum bone-specific alkaline phosphatase (BAP). The other study reported that both bisphosphonate plus alfacalcidol and alfacalcidol alone reduced BAP, but did not compare groups. Neither study reported data for the effect of bisphosphonate treatment on changes in volumetric BMD in the distal radius or tibia, changes in fracture frequency, bone pain, or quality of life. One study reported that two participants had febrile events noted during their first dosing schedule, but no further adverse events were reported in either relevant study.

AUTHORS' CONCLUSIONS

Based on the available evidence, there is very low certainty evidence that bisphosphonate treatment may improve bone health in children with cerebral palsy. We could only include one study with 14 participants in the assessment of the effect size; therefore, the precision of the effect estimate is low. We could only evaluate one planned primary outcome, as there was insufficient detail reported in the relevant studies. Further research from RCTs on the effect and safety of bisphosphonate to improve bone health in children with cerebral palsy is required. These studies should clarify the optimal standard treatment regarding weight-bearing exercises, vitamin D and calcium supplementation, and should include fracture frequency as a primary outcome.

Nanohydroxyapatite (nHAp) Doped with Iron Oxide Nanoparticles (IO), miR-21 and miR-124 Under Magnetic Field Conditions Modulates Osteoblast Viability, Reduces Inflammation and Inhibits the Growth of Osteoclast - A Novel Concept for Osteoporosis Treatment: Part 1

Purpose

Osteoporosis results in a severe decrease in the life quality of many people worldwide. The latest data shows that the number of osteoporotic fractures is becoming an increasing international health service problem. Therefore, a new kind of controllable treatment methods for osteoporotic fractures is extensively desired. For that reason, we have manufactured and evaluated nanohydroxyapatite (nHAp)-based composite co-doped with iron oxide (IO) nanoparticles. The biomaterial was used as a matrix for the controlled delivery of miR-21-5p and miR-124-3p, which have a proven impact on bone cell metabolism.

Methods

The nanocomposite Ca₅(PO₄)₃OH/Fe₃O₄ (later called nHAp/IO) was obtained by the wet chemistry method and functionalised with microRNAs (nHAp/IO@miR-21/124). Its physicochemical characterization was performed using XRPD, FT-IR, SEM-EDS and HRTEM and SAED methods. The modulatory effect of the composite was tested in vitro using murine pre-osteoblasts MC3T3-E1 and pre-osteoclasts 4B12. Moreover, the anti-inflammatory effects of biomaterial were analysed using a model of LPS-treated murine macrophages RAW 264.7. We have analysed the cells’ viability, mitochondria membrane potential and oxidative stress under magnetic field (MF+) and without (MF-). Moreover, the results were supplemented with RT-qPCR and Western blot assays to evaluate the expression profile for master regulators of bone metabolism.

Results

The results indicated pro-osteogenic effects of nHAp/IO@miR-21/124 composite enhanced by exposure to MF. The enhanced osteogenesis guided by nHAp/IO@miR-21/124 presence was associated with increased metabolism of progenitor cells and activation of osteogenic markers (Runx-2, Opn, Coll-1). Simultaneously, nanocomposite decreased metabolism and differentiation of pre-osteoclastic 4B12 cells accompanied by reduced expression of CaII and Ctsk. Obtained composite regulated viability of bone progenitor cells and showed immunomodulatory properties inhibiting the expression of inflammatory markers, ie, TNF-α, iNOs or IL-1β, in LPS-stimulated RAW 264.7 cells.

Conclusion

We have described for the first time a new concept of osteoporosis treatment based on nHAp/IO@miR-21/124 application. Obtained results indicated that fabricated nanocomposite might impact proper regeneration of osteoporotic bone, restoring the balance between osteoblasts and osteoclast.

Tissue Engineering Through 3D Bioprinting to Recreate and Study Bone Disease

The applications of 3D bioprinting are becoming more commonplace. Since the advent of tissue engineering, bone has received much attention for the ability to engineer normal bone for tissue engraftment or replacement. While there are still debates on what materials comprise the most durable and natural replacement of normal tissue, little attention is given to recreating diseased states within the bone. With a better understanding of the cellular pathophysiology associated with the more common bone diseases, these diseases can be scaled down to a more throughput way to test therapies that can reverse the cellular pathophysiology. In this review, we will discuss the potential of 3D bioprinting of bone tissue in the following disease states: osteoporosis, Paget's disease, heterotopic ossification, osteosarcoma, osteogenesis imperfecta, and rickets disease. The development of these 3D bioprinted models will allow for the advancement of novel therapy testing resulting in possible relief to these chronic diseases.

Identification of Potential Therapeutic Targets and Molecular Regulatory Mechanisms for Osteoporosis by Bioinformatics Methods

BACKGROUND

Osteoporosis is characterized by low bone mass, deterioration of bone tissue structure, and susceptibility to fracture. New and more suitable therapeutic targets need to be discovered.

METHODS

We collected osteoporosis-related datasets (GSE56815, GSE99624, and GSE63446). The methylation markers were obtained by differential analysis. Degree, DMNC, MCC, and MNC plug-ins were used to screen the important methylation markers in PPI network, then enrichment analysis was performed. ROC curve was used to evaluate the diagnostic effect of osteoporosis. In addition, we evaluated the difference in immune cell infiltration between osteoporotic patients and control by ssGSEA. Finally, differential miRNAs in osteoporosis were used to predict the regulators of key methylation markers.

RESULTS

A total of 2351 differentially expressed genes and 5246 differentially methylated positions were obtained between osteoporotic patients and controls. We identified 19 methylation markers by PPI network. They were mainly involved in biological functions and signaling pathways such as apoptosis and immune inflammation. HIST1H3G, MAP3K5, NOP2, OXA1L, and ZFPM2 with higher AUC values were considered key methylation markers. There were significant differences in immune cell infiltration between osteoporotic patients and controls, especially dendritic cells and natural killer cells. The correlation between MAP3K5 and immune cells was high, and its differential expression was also validated by other two datasets. In addition, NOP2 was predicted to be regulated by differentially expressed hsa-miR-3130-5p.

CONCLUSION

Our efforts aim to provide new methylation markers as therapeutic targets for osteoporosis to better treat osteoporosis in the future.

An Overview of the Molecular Mechanisms Contributing to Musculoskeletal Disorders in Chronic Liver Disease: Osteoporosis, Sarcopenia, and Osteoporotic Sarcopenia

The prevalence of osteoporosis and sarcopenia is significantly higher in patients with liver disease than in those without liver disease and osteoporosis and sarcopenia negatively influence morbidity and mortality in liver disease, yet these musculoskeletal disorders are frequently overlooked in clinical practice for patients with chronic liver disease. The objective of this review is to provide a comprehensive understanding of the molecular mechanisms of musculoskeletal disorders accompanying the pathogenesis of liver disease. The increased bone resorption through the receptor activator of nuclear factor kappa (RANK)-RANK ligand (RANKL)-osteoprotegerin (OPG) system and upregulation of inflammatory cytokines and decreased bone formation through increased bilirubin and sclerostin and lower insulin-like growth factor-1 are important mechanisms for osteoporosis in patients with liver disease. Sarcopenia is associated with insulin resistance and obesity in non-alcoholic fatty liver disease, whereas hyperammonemia, low amount of branched chain amino acids, and hypogonadism contributes to sarcopenia in liver cirrhosis. The bidirectional crosstalk between muscle and bone through myostatin, irisin, β-aminoisobutyric acid (BAIBA), osteocalcin, as well as the activation of the RANK and the Wnt/β-catenin pathways are associated with osteosarcopenia. The increased understandings for these musculoskeletal disorders would be contributes to the development of effective therapies targeting the pathophysiological mechanism involved.

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.