Osteoblast as a target of anti-osteoporotic treatment

Discovery of Novel Neo-Clerodane Derivatives as Potent Dual-Functional Antiosteoporosis Agents through Targeting Peroxisome Proliferator-Activated Receptor-γ

A library of 31 natural neo-clerodanes isolated from Ajuga decumbens was assayed for antiosteoporosis. This results in 18 neo-clerodane osteoclastogenesis inhibitors, and compound 3 prevents bone loss in vivo. Further mechanistic studies demonstrated that these compounds inhibit osteoporosis by antagonizing peroxisome proliferator-activated receptor-γ (PPARγ). We designed and synthesized 17 compounds by chemically modifying the natural neo-clerodane 19 (highly potent and the major composition of A. decumbens extract) by means of structure-based drug design techniques. Among these neo-clerodane derivatives, compound 34 is the most potent osteoporosis inhibitor with a 46-fold improvement in inhibiting osteoclastogenesis (IC50 = 0.042 vs 1.92 μM), 11-fold increased activity in PPARγ antagonism (EC50 = 0.75 vs 8.35 μM), 66-fold enhancement in receptor affinity (KD = 0.27 vs 17.7 μM), and enhanced osteogenic promotion compared to 19. This underscores the potential of neo-clerodane diterpenoids as promising leads for osteoporosis treatment by targeting PPARγ.

Insights and implications of sexual dimorphism in osteoporosis

Osteoporosis, a metabolic bone disease characterized by low bone mineral density and deterioration of bone microarchitecture, has led to a high risk of fatal osteoporotic fractures worldwide. Accumulating evidence has revealed that sexual dimorphism is a notable feature of osteoporosis, with sex-specific differences in epidemiology and pathogenesis. Specifically, females are more susceptible than males to osteoporosis, while males are more prone to disability or death from the disease. To date, sex chromosome abnormalities and steroid hormones have been proven to contribute greatly to sexual dimorphism in osteoporosis by regulating the functions of bone cells. Understanding the sex-specific differences in osteoporosis and its related complications is essential for improving treatment strategies tailored to women and men. This literature review focuses on the mechanisms underlying sexual dimorphism in osteoporosis, mainly in a population of aging patients, chronic glucocorticoid administration, and diabetes. Moreover, we highlight the implications of sexual dimorphism for developing therapeutics and preventive strategies and screening approaches tailored to women and men. Additionally, the challenges in translating bench research to bedside treatments and future directions to overcome these obstacles will be discussed.

2,4'-Dihydroxybenzophenone Exerts Bone Formation and Antiosteoporotic Activity by Stimulating the β-Catenin Signaling Pathway

2,4'-Dihydroxybenzophenone (DHP) is an organic compound derived from Garcinia xanthochymus, but there have been no reports on its biochemical functions and bioavailability. In this study, we evaluated whether DHP affects osteoblast differentiation and activation in MC3T3-E1 preosteoblast cells, as well as antiosteoporotic activity in zebrafish larvae. Nontoxic concentrations of DHP-treated MC3T3-E1 preosteoblast cells increased alkaline phosphatase (ALP) activation and mineralization in a concentration-dependent manner, accompanied by higher expression of osteoblast-specific markers, including Runt-related transcription factor 2 (RUNX2), osterix, and ALP. Consistent with the data in MC3T3-E1 preosteoblast cells, DHP upregulated osteoblast-specific marker genes in zebrafish larvae and simultaneously enhanced vertebral formation. We also revealed that DHP increased the phosphorylation of glycogen synthase kinase-3β (GSK-3β) at Ser9 and the total expression of β-catenin in the cytosol and markedly increased the localization of β-catenin into the nucleus. Furthermore, DHP restored the prednisolone (PDS)-induced marked decrease in ALP activity and mineralization, as well as osteoblast-specific marker expression. In PDS-treated zebrafish, DHP also alleviated PDS-induced osteoporosis by restoring vertebral formation and osteoblast-related gene expression. Taken together, these results suggest that DHP is a potential osteoanabolic candidate for treating osteoporosis by stimulating osteoblast differentiation.

Expanding the therapeutic potential of Salvia miltiorrhiza: a review of its pharmacological applications in musculoskeletal diseases

Salvia miltiorrhiz, commonly known as "Danshen" in Chinese medicine, has longstanding history of application in cardiovascular and cerebrovascular diseases. Renowned for its diverse therapeutic properties, including promoting blood circulation, removing blood stasis, calming the mind, tonifying the blood, and benefiting the "Qi", recent studies have revealed its significant positive effects on bone metabolism. This potential has garnered attention for its promising role in treating musculoskeletal disorders. Consequently, there is a high anticipation for a comprehensive review of the potential of Salvia miltiorrhiza in the treatment of various musculoskeletal diseases, effectively introducing an established traditional Chinese medicine into a burgeoning field.

AIM OF THE REVIEW

Musculoskeletal diseases (MSDs) present significant challenges to healthcare systems worldwide. Previous studies have demonstrated the high efficacy and prospects of Salvia miltiorrhiza and its active ingredients for treatment of MSDs. This review aims to illuminate the newfound applications of Salvia miltiorrhiza and its active ingredients in the treatment of various MSDs, effectively bridging the gap between an established medicine and an emerging field.

METHODS

In this review, previous studies related to Salvia miltiorrhiza and its active ingredients on the treatment of MSD were collected, the specific active ingredients of Salvia miltiorrhiza were summarized, the effects of Salvia miltiorrhiza and its active ingredients for the treatment of MSDs, as well as their potential molecular mechanisms were reviewed and discussed.

RESULTS

Based on previous publications, Salvianolic acid A, salvianolic acid B, tanshinone IIA are the representative active ingredients of Salvia miltiorrhiza. Their application has shown significant beneficial outcomes in osteoporosis, fractures, and arthritis. Salvia miltiorrhiza and its active ingredients protect against MSDs by regulating different signaling pathways, including ROS, Wnt, MAPK, and NF-κB signaling.

CONCLUSION

Salvia miltiorrhiza and its active ingredients demonstrate promising potential for bone diseases and have been explored across a wide variety of MSDs. Further exploration of Salvia miltiorrhiza's pharmacological applications in MSDs holds great promise for advancing therapeutic interventions and improving the lives of patients suffering from these diseases.

An Integrative Study on the Inhibition of Bone Loss via Osteo-F Based on Network Pharmacology, Experimental Verification, and Clinical Trials in Postmenopausal Women

The inhibition of bone loss remains a challenge for postmenopausal women, considering the fact that only three anabolic treatments for osteoporosis have been approved by the FDA. This study aimed to investigate the osteogenic capacities of Osteo-F, a newly developed herbal formula, upon integrating network analysis and pre-clinical studies into clinical trials. The network pharmacology analysis showed that a potential mechanism of Osteo-F is closely related to osteoblast differentiation. Consistent with the predicted mechanism, Osteo-F treatment significantly enhanced bone matrix formation and mineralization with collagen expression in osteoblasts. Simultaneously, secreted bone-forming molecules were upregulated by Osteo-F. After the administration of Osteo-F to osteoporotic mice, the femoral BMD and osteocalcin in the serum and bone tissues were significantly improved. Subsequently, a randomized, double-blinded, placebo-controlled clinical trial showed that 253 mg of Osteo-F supplementation for 24 weeks resulted in significant improvements in the Z-score and serum osteocalcin levels of postmenopausal women compared to the placebo, thus indicating bone anabolic efficacy. In the current study, the bone anabolic effect of Osteo-F was determined by activating the differentiation and mineralization of osteoblasts through integrating experiments based on network analysis into clinical trials, with synchronized, reliable evidence, demonstrating that Osteo-F is a novel bone anabolic treatment in postmenopausal women.

Myosin heavy chain-derived peptide of Gadus morhua promotes proliferation and differentiation in osteoblasts and bone formation and maintains bone homeostasis in ovariectomized mice

Gadus morhua is an important commercial fish rich in nutrients required for daily metabolism. However, the regulation of G. morhua peptides (GMP) on osteoblast growth remains unclear. In order to clarify the regulatory effects of GMP on osteoblasts, the effects of GMP on the growth of MC3T3-E1 cells were investigated, and the osteogenic peptides were identified and screened. The results showed that GMP promoted the proliferation and differentiation of osteoblasts by regulating the BMP/WNT signaling pathway at concentrations of 1-100 μg mL^-1. Molecular docking studies showed that a decapeptide, MNKKREAEFQ (P-GM-1), had a high affinity for integrins 3VI4 and 1L5G (-CDOCKER interaction energy: 161.30, 212.27 kcal mol^-1). Additionally, the proliferation rate of MC3T3-E1 cells was increased by 27%, and ALP activity was significantly increased under P-GM-1 treatment (100 μg mL^-1). Moreover, P-GM-1 promotes bone formation, maintains bone homeostasis, and prevents osteoporosis in ovariectomized mice by regulating the BMP/Smad signaling pathway. This study confirmed the potential of GMP in the regulation of bone mineral density and provided a certain theoretical basis for the development of anti-osteoporosis active factors from GMP.

CX3CL1 deficiency ameliorates inflammation, apoptosis and accelerates osteogenic differentiation, mineralization in LPS-treated MC3T3-E1 cells via its receptor CX3CR1

BACKGROUND

Osteoporosis is a devastating skeletal disease responsible for bone fragility and fracture. CX3C chemokine ligand 1 (CX3CL1) is an inflammatory chemokine which has been identified to possess increased expression in the serum of postmenopausal osteoporotic patients. This paper was to illuminate the impacts of CX3CL1 on inflammation, apoptosis and osteogenic differentiation, mineralization in LPS-treated osteoblasts and investigate the regulatory mechanism.

METHODS

The viability of MC3T3-E1 cells exposed to elevating doses of LPS was detected by CCK-8 assay. CX3CL1 and C-X3-C motif chemokine receptor 1 (CX3CR1) expression were detected by RT-qPCR and western blot. CX3CR1 expression was examined again following CX3CL1 depletion. The binding of CX3CL1 with CX3CR1 was testified through Co-IP assay. In MC3T3-E1 cells co-transduced with CX3CL1 interference and CX3CR1 overexpression plasmids following LPS exposure, cell activity and inflammation were separately estimated via CCK-8 assay and RT-qPCR. Apoptosis was measured by TUNEL assay and western blot. Osteoblast differentiation was evaluated by ALP activity assay, RT-qPCR and western blot. Osteoblast mineralization was assessed by ARS staining, RT-qPCR and western blot. Results The experimental data presented that LPS attenuated the viability and enhanced CX3CL1 and CX3CR1 expression in MC3T3-E1 cells in a dose-dependent manner. CX3CR1 interacted with CX3CL1 and was positively modulated by CX3CL1. The suppressive role of CX3CL1 absence in LPS-evoked viability decrease, inflammation and apoptosis in MC3T3-E1 cells was reversed by CX3CR1 elevation. Besides, CX3CR1 reversed the promoted osteoblast differentiation and mineralization imposed by CX3CL1 interference.

CONCLUSIONS

CX3CL1 knockdown eased inflammation, apoptosis and promoted osteogenic differentiation, mineralization in MC3T3-E1 cells upon LPS exposure through down-regulating CX3CR1.

FOXO1 differentially regulates bone formation in young and aged mice

It is a great challenge to develop a safe and effective treatment strategy for age-related osteoporosis and fracture healing. As one of the four FOXO transcription factors, FOXO1 is essential for cell proliferation, survival, senescence, energy metabolism, and oxidative stress in various cells. Our previous study demonstrated that specific Foxo1 gene deletion in osteoblasts in young mice results in bone loss while that in aged mice shows the opposite effect. However, the mechanism underlying the differential regulation of bone metabolism by FOXO1 remains to be elucidated. In this study, we generated osteoblast-specific Foxo1 knockout mice by using Foxo1^fl/fl and Bglap-Cre mice. In young mice, Foxo1 gene deletion inhibits osteoblast differentiation, leading to a decreased osteoblast number and decreased bone formation rate because of the weakened ability to resist oxidative stress, eventually resulting in bone loss and delayed healing of bone defects. In aged mice, high levels of reactive oxygen species (ROS) promote the diversion of CTNNB1 (β-catenin) from T cell factor 4 (TCF4)- to FOXO1-mediated transcription, thereby inhibiting Wnt/β-catenin signaling and leading to decreased osteogenic activity. Conversely, FOXO1 deficiency indirectly promotes the binding of β-catenin and TCF4 and activates Wnt/β-catenin signaling, thereby alleviating age-related bone loss and improving bone defect healing. Our study proves that FOXO1 has differential effects on bone metabolism in young and aged mice and elucidates its underlying mechanism. Further, this study provides a new perspective on the treatment of age-related osteoporosis.

Aminobisphosphonates: Reconsideration 25 years after their approval for the treatment of osteoporosis

Aminobisphosphonates are widely used in the treatment of osteoporosis. They have a high affinity for hydroxyapatite, binding primarily to resorbing surfaces, but also to forming surfaces and to some extent to resting surfaces. They inhibit osteoclasts, thereby decreasing remodelling units. Consequently, they increase bone mass and reduce stress risers. This decreases the risk of fractures. If this decrease is sufficient, they can be temporarily withdrawn (drug holidays), which prevents serious complications (atypical femoral fracture). They probably reduce mortality. Virtually all patients with osteoporosis can benefit from them at some point in the course of their disease (at the beginning of treatment or after the administration of anabolics, selective estrogen receptor modulators or denosumab). If well tolerated orally, alendronate and risedronate are preferable. Otherwise, zoledronate is preferred. Their efficacy vs. cost-safety-convenience ratio makes aminobisphosphonates reference drugs in the field of osteoporosis.

Bone Involvement in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by a wide variability of clinical manifestations due to the potential involvement of several tissues and internal organs, with a relapsing and remitting course. Dysregulation of innate and adaptive immune systems, due to genetic, hormonal and environmental factors, may be responsible for a broad spectrum of clinical manifestations, affecting quality of life, morbidity and mortality. Bone involvement represents one of the most common cause of morbidity and disability in SLE. Particularly, an increased incidence of osteoporosis, avascular necrosis of bone and osteomyelitis has been observed in SLE patients compared to the general population. Moreover, due to the improvement in diagnosis and therapy, the survival of SLE patient has improved, increasing long-term morbidities, including osteoporosis and related fractures. This review aims to highlight bone manifestations in SLE patients, deepening underlying etiopathogenetic mechanisms, diagnostic tools and available treatment.

Epigenetic therapy targeting bone marrow mesenchymal stem cells for age-related bone diseases

As global aging accelerates, the prevention and treatment of age-related bone diseases are becoming a critical issue. In the process of senescence, bone marrow mesenchymal stem cells (BMSCs) gradually lose the capability of self-renewal and functional differentiation, resulting in impairment of bone tissue regeneration and disorder of bone tissue homeostasis. Alteration in epigenetic modification is an essential factor of BMSC dysfunction during aging. Its transferability and reversibility provide the possibility to combat BMSC aging by reversing age-related modifications. Emerging evidence demonstrates that epigenetic therapy based on aberrant epigenetic modifications could alleviate the senescence and dysfunction of stem cells. This review summarizes potential therapeutic targets for BMSC aging, introduces some potential approaches to alleviating BMSC aging, and analyzes its prospect in the clinical application of age-related bone diseases.

Identification of a Novel Osteogenetic Oligodeoxynucleotide (osteoDN) That Promotes Osteoblast Differentiation in a TLR9-Independent Manner

Dysfunction of bone-forming cells, osteoblasts, is one of the causes of osteoporosis. Accumulating evidence has indicated that oligodeoxynucleotides (ODNs) designed from genome sequences have the potential to regulate osteogenic cell fate. Such osteogenetic ODNs (osteoDNs) targeting and activating osteoblasts can be the candidates of nucleic acid drugs for osteoporosis. In this study, the ODN library derived from the Lacticaseibacillus rhamnosus GG genome was screened to determine its osteogenetic effect on murine osteoblast cell line MC3T3-E1. An 18-base ODN, iSN40, was identified to enhance alkaline phosphatase activity of osteoblasts within 48 h. iSN40 also induced the expression of osteogenic genes such as Msx2, osterix, collagen type 1α, osteopontin, and osteocalcin. Eventually, iSN40 facilitated calcium deposition on osteoblasts at the late stage of differentiation. Intriguingly, the CpG motif within iSN40 was not required for its osteogenetic activity, indicating that iSN40 functions in a TLR9-independent manner. These data demonstrate that iSN40 serves as a novel osteogenetic ODN (osteoDN) that promotes osteoblast differentiation. iSN40 provides a potential seed of the nucleic acid drug that activating osteoblasts for osteoporosis therapy.

Phytochemical Analysis, Antioxidant and Bone Anabolic Effects of Blainvillea acmella (L.) Philipson

Blainvillea acmella (L.) Philipson [Asteraceae] (B. acmella) is an important medicinal plant native to Brazil, and it is widely known as a toothache plant. A plethora of studies have demonstrated the antioxidant activities of B. acmella and few studies on the stimulatory effects on alkaline phosphatase (ALP) secretion from bone cells; however, there is no study on its antioxidant and anabolic activity on bone cells. The study aimed to evaluate the phytochemical contents of aqueous and ethanol extracts of B. acmella using gas chromatography mass spectrometry (GCMS) and liquid chromatography time of flight mass spectrometry (LCTOFMS) along with the total phenolic (TPC) and flavonoid (TFC) contents using Folin-Ciocalteu and aluminum colorimetric methods. The extracts of B. acmella leaves were used to scavenge synthetic-free radicals such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) assays. The bone anabolic effects of B. acmella extracts on MC3T3-E1 cells were measured with 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazoium bromide (MTT) at 1, 3, 5, and 7 days, Sirius-red and ALP at 7 and 14 days, and Alizarin Red S at 14 and 21 days. Comparatively, ethanol extract of B. acmella (BaE) contributed higher antioxidant activities (IC₅₀ of 476.71 µg/ml and 56.01 ± 6.46 mg L-ascorbic acid/g against DPPH and FRAP, respectively). Anabolic activities in bone proliferation, differentiation, and mineralization were also higher in B. acmella of ethanol (BaE) than aqueous (BaA) extracts. Positive correlations were observed between phenolic content (TPC and TFC) to antioxidant (ABTS and FRAP) and anabolic activities. Conversely, negative correlations were present between phenolic content to antioxidant (DPPH) activity. These potential antioxidant and bone anabolic activities in BaE might be due to the phytochemicals confirmed through GCMS and LCTOFMS, revealed that terpenoids of α-cubebene, cryophyllene, cryophyllene oxide, phytol and flavonoids of pinostrobin and apigenin were the compounds contributing to both antioxidant and anabolic effects in BaE. Thus, B. acmella may be a valuable antioxidant and anti-osteoporosis agent. Further study is needed to isolate, characterize and elucidate the underlying mechanisms responsible for the antioxidant and bone anabolic effects.

Osteoblast Dysfunction in Non-Hereditary Sclerosing Bone Diseases

A review of the available literature was performed in order to summarize the existing evidence between osteoblast dysfunction and clinical features in non-hereditary sclerosing bone diseases. It has been known that proliferation and migration of osteoblasts are concerted by soluble factors such as fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), transforming growth factor (TGF), bone morphogenetic protein (BMP) but also by signal transduction cascades such as Wnt signaling pathway. Protein kinases play also a leading role in triggering the activation of osteoblasts in this group of diseases. Post-zygotic changes in mitogen-activated protein kinase (MAPK) have been shown to be associated with sporadic cases of Melorheostosis. Serum levels of FGF and PDGF have been shown to be increased in myelofibrosis, although studies focusing on Sphingosine-1-phosphate receptor was shown to be strongly expressed in Paget disease of the bone, which may partially explain the osteoblastic hyperactivity during this condition. Pathophysiological mechanisms of osteoblasts in osteoblastic metastases have been studied much more thoroughly than in rare sclerosing syndromes: striking cellular mechanisms such as osteomimicry or complex intercellular signaling alterations have been described. Further research is needed to describe pathological mechanisms by which rare sclerosing non hereditary diseases lead to osteoblast dysfunction.

The potential role of lncRNAs in osteoporosis

Osteoporosis is a common bone disease characterized by low bone mass and deterioration of bone microstructure, which predisposes to higher risks of bone fragility and bone fracture. Long non-coding RNAs (lncRNAs) are a class of RNAs with a length of > 200 nucleotides without protein-coding function, which control the expression of genes and affect multiple biological processes. Accumulating evidence suggests that lncRNAs are widely involved in the molecular mechanisms of osteoporosis. This review aims to summarize the function and underlying mechanism of lncRNAs involved in the development of osteoporosis, and how it contributes to osteoblast and osteoclast function. This knowledge will shed new light on the modulation and potential treatment of osteoporosis.

Bisphosphonates in inflammatory rheumatic diseases

The main well recognized action of bisphosphonates (BPs) is their antiresorptive capacity, making them first-line drugs in the treatment of osteoporosis and other metabolic bone diseases. In this review we have compiled other possible actions of BPs, particularly in the areas of immunomodulation, anti-inflammatory capacity and in the prevention of structural joint damage in inflammatory rheumatic diseases. The immunomodulatory capacity of BPs has been focused on the mechanisms involved in the acute-phase response associated with the administration of nitrogen containing BPs (N-BPs), with the stimulus of pro-inflammatory cytokines, through the mevalonate pathway, activation of T-cells and the decrease in the cytotoxic T-lymphocyte antigen-4 (CTLA-4). In relation to their anti-inflammatory capacity, special attention has been given to their effect on preventing structural damage in inflammatory joint diseases and on the differential immune response in bone lesions of the most common and representative inflammatory rheumatic diseases, i.e. rheumatoid arthritis and spondyloarthropathies. The present data indicate that more studies are needed to improve the knowledge on the effect of BPs on inflammatory-mediated diseases and particularly on the prevention and/or treatment of the structural damage in these disorders, since these agents could be a potential useful concomitant therapy.

Osteoblast-n-Osteoclast: Making Headway to Osteoporosis Treatment

Background:

Bone is a dynamic tissue that continuously undergoes the modeling and remodeling process to maintain its strength and firmness. Bone remodeling is determined by the functioning of osteoblast and osteoclast cells. The imbalance between the functioning of osteoclast and osteoblast cells leads to osteoporosis. Osteoporosis is divided into primary and secondary osteoporosis. Generally, osteoporosis is diagnosed by measuring bone mineral density (BMD) and various osteoblast and osteoclast cell markers.

Methods:

Relevant literature reports have been studied and data has been collected using various search engines like google scholar, scihub, sciencedirect, pubmed, etc. A thorough understanding of the mechanism of bone targeting strategies has been discussed and related literature has been studied and compiled.

Results:

Bone remodeling process has been described in detail including various approaches for targeting bone. Several bone targeting moieties have been stated in detail along with their mechanisms. Targeting of osteoclasts and osteoblasts using various nanocarriers has been discussed in separate sections. The toxicity issues or Biosafety related to the use of nanomaterials have been covered.

Conclusion:

The treatment of osteoporosis targets the inhibition of bone resorption and the use of agents that promote bone mineralization to slow disease progression. Current osteoporosis therapy involves the use of targeting moieties such as bisphosphonates and tetracyclines for targeting various drugs. Nanotechnology has been used for targeting various drug molecules such as RANKLinhibitors, parathyroid hormone analogues, estrogen agonists and antagonists, Wnt signaling enhancer and calcitonin specifically to bone tissue (osteoclast and osteoblasts). So, a multicomponent treatment strategy targeting both the bone cells will be more effective rather than targeting only osteoclasts and it will be a potential area of research in bone targeting used to treat osteoporosis. The first section of the review article covers various aspects of bone targeting. Another section comprises details of various targeting moieties such as bisphosphonates, tetracyclines; and various nanocarriers developed to target osteoclast and osteoblast cells and summarized data on in vivo models has been used for assessment of bone targeting, drawbacks of current strategies and future perspectives.

Fibronectin 1 activates WNT/β-catenin signaling to induce osteogenic differentiation via integrin β1 interaction

Osteoporosis (OP) is a systemic skeletal disease leading to fragility fractures and is a major health issue globally. WNT/β-catenin signaling regulates bone-remodeling processes and plays vital roles in OP development. However, the underlying regulatory mechanisms behind WNT/β-catenin signaling in OP requires clarification, as further studies are required to identify novel alternate therapeutic agents to improve OP. Here we report that fibronectin 1 (FN-1) promoted differentiation and mineralization of osteoblasts by activating WNT/β-catenin pathway, in cultured pre-osteoblasts. With isobaric tags for relative and absolute quantitation labeling proteomics analysis, we investigated protein changes in bone samples from OP patients and normal controls. FN-1 accumulated in osteoblasts in bone samples from OP patients and age-related OP mice compared to control group. In addition, we observed that integrin β1 (ITGB1) acts as an indispensable signaling molecule for the interplay between FN-1 and β-catenin, and that FN-1 expression increased, but ITGB1 expression decreased in osteoblasts during OP progression. Therefore, our study reveals a novel explanation for WNT/β-catenin pathway inactivation in OP pathology. Supplying of FN-1 and ITGB1 may provide a potential therapeutic strategy in improving bone formation during OP.

MiR-17-3p inhibits osteoblast differentiation by downregulating Sox6 expression

Osteoporosis and osteoarthritis are orthopedic disorders that affect millions of elderly people worldwide; stimulation of bone formation is a potential therapeutic strategy for the treatment of these conditions. As the only bone‐forming cells, osteoblasts play a key role in bone reconstruction. The microRNA miR‐17‐3p is downregulated during osteogenic differentiation of human bone marrow mesenchymal stem cells, but its precise role in this process is unknown. Here, we investigated the role of miR‐17‐3p in osteoblast differentiation. An in vitro model of osteogenesis was established by treating MC3T3‐E1 murine preosteoblast cells with bone morphogenetic protein 2 (BMP2). The expression of miR‐17‐3p in BMP2‐induced MC3T3‐E1 cells was detected by reverse transcription‐quantitative PCR, and its effects on cells transfected with miR‐17‐3p mimic or inhibitor were evaluated by Alizarin Red staining, alkaline phosphatase (ALP) activity assay, and by detection of osteoblast markers including the ALP, collagen type I α1 chain, and osteopontin genes. Bioinformatics analysis was carried out to identify putative target genes of miR‐17‐3p, and the luciferase reporter assay was used for functional validation. Rescue experiments were performed to determine whether SRY‐box transcription factor 6 (Sox6) plays a role in the regulation of osteoblast differentiation by miR‐17‐3p. We report that miR‐17‐3p was downregulated upon BMP2‐induced osteoblast differentiation in MC3T3‐E1 cells, and this was accompanied by decreased differentiation and mineralization, ALP activity, and expression of osteogenesis‐related genes. Sox6 was confirmed to be a target gene of miR‐17‐3p in osteoblasts, and the inhibitory effect of miR‐17‐3p on osteoblast differentiation was observed to occur via Sox6. These results suggest the existence of a novel mechanism underlying miRNA‐mediated regulation of osteogenesis, which has potential implications for the treatment of orthopedic disorders.

JAK/STAT pathway and molecular mechanism in bone remodeling

JAK/STAT signaling pathway is involved in many diseases, including autoimmune diseases, which are characterized by a close interconnection between immune and bone system. JAK/STAT pathway is involved in bone homeostasis and plays an important role in proliferation and differentiation of some cell types, including osteoblasts and osteoclasts. Different molecules, such as cytokines, hormones, and growth factors are responsible for the activation of the JAK/STAT pathway, which leads, at the nuclear level, to start DNA transcription of target genes. Bone cells and remodeling process are often influenced by many cytokines, which act as strong stimulators of bone formation and resorption. Our aim, through careful research in literature, has been to provide an overview of the role of the JAK/STAT pathway in bone remodeling and on bone cells, with a focus on cytokines involved in bone turnover through this signal cascade. The JAK/STAT pathway, through the signal cascade activation mediated by the interaction with many cytokines, acts on bone cells and appears to be involved in bone remodeling process. However, many other studies are needed to completely understand the molecular mechanism underlying these bone process.

Crosstalk of Brain and Bone-Clinical Observations and Their Molecular Bases

As brain and bone disorders represent major health issues worldwide, substantial clinical investigations demonstrated a bidirectional crosstalk on several levels, mechanistically linking both apparently unrelated organs. While multiple stress, mood and neurodegenerative brain disorders are associated with osteoporosis, rare genetic skeletal diseases display impaired brain development and function. Along with brain and bone pathologies, particularly trauma events highlight the strong interaction of both organs. This review summarizes clinical and experimental observations reported for the crosstalk of brain and bone, followed by a detailed overview of their molecular bases. While brain-derived molecules affecting bone include central regulators, transmitters of the sympathetic, parasympathetic and sensory nervous system, bone-derived mediators altering brain function are released from bone cells and the bone marrow. Although the main pathways of the brain-bone crosstalk remain ‘efferent’, signaling from brain to bone, this review emphasizes the emergence of bone as a crucial ‘afferent’ regulator of cerebral development, function and pathophysiology. Therefore, unraveling the physiological and pathological bases of brain-bone interactions revealed promising pharmacologic targets and novel treatment strategies promoting concurrent brain and bone recovery.

Advancements in Hydrogel-Based Drug Sustained Release Systems for Bone Tissue Engineering

Bone defects caused by injury, disease, or congenital deformity remain a major health concern, and efficiently regenerating bone is a prominent clinical demand worldwide. However, bone regeneration is an intricate process that requires concerted participation of both cells and bioactive factors. Mimicking physiological bone healing procedures, the sustained release of bioactive molecules plays a vital role in creating an optimal osteogenic microenvironment and achieving promising bone repair outcomes. The utilization of biomaterial scaffolds can positively affect the osteogenesis process by integrating cells with bioactive factors in a proper way. A high water content, tunable physio-mechanical properties, and diverse synthetic strategies make hydrogels ideal cell carriers and controlled drug release reservoirs. Herein, we reviewed the current advancements in hydrogel-based drug sustained release systems that have delivered osteogenesis-inducing peptides, nucleic acids, and other bioactive molecules in bone tissue engineering (BTE).

Circaea mollis Siebold & Zucc. Alleviates postmenopausal osteoporosis in a mouse model via the BMP-2/4/Runx2 pathway

Background

Circaea mollis Sieb. & Zucc. has been used as a traditional herbal medicine in Hani Ethnopharmacy and possesses anti-arthritic activities. This study aimed to investigate the effect of Circaea mollis Siebold & Zucc on postmenopausal osteoporosis.

Methods

For in vitro study, MCF7 breast cancer cells and MC3T3-E1 pre-osteoblast cells were utilized to estimate estrogenic and osteogenic activity. Osteoblastic markers were measured by western blot and real-time PCR. For in vivo study, female mature C57BL/6 mice were ovariectomized and oral administrated with 10 mg/kg and 40 mg/kg of EECM respectively.

Results

EtOH extract of Circaea mollis Siebold & Zucc. (EECM) increased alkaline phosphatase activity and osteoblast marker levels at day 7 during differentiation of mouse preosteoblasts. EECM reduced osteoclast differentiation and bone resorption in an osteoblast-osteoclast primary co-culture system. In ovariectomized mice, EECM prevented the decrease in bone mineral density and recovered OSX and Runx2 via BMP2/4, Smad1/5/9 and p38.

Conclusions

The results suggest that EECM may be effective in preventing bone loss, offering a promising alternative for the nutritional management of postmenopausal osteoporosis.

Activation of cannabinoid receptor type 2-induced osteogenic differentiation involves autophagy induction and p62-mediated Nrf2 deactivation

Background

Dysfunction in survival and differentiation of osteoblasts commonly occurs in patients with osteoporosis. Cannabinoid receptor type 2 (CNR2) is a major receptor of endocannabinoid system that is crucial for bone mass homeostasis. Our group prior demonstrated that activation of CNR2 signaling promoted osteogenic differentiation of bone marrow derived mesenchymal stem cells in vitro. Autophagy is reported to participate in osteoblastic differentiation. Whether autophagy is regulated by CNR2-mediated cannabinoid signaling is unknown, and how the autophagy-CNR2 interaction affects osteoblastic differentiation requires further elucidation.

Methods

hFOB 1.19 osteoblasts were treated with CNR2 agonists HU308 (5, 10, 25, 50 or 100 nM) and JWH133 (1, 2, 5, 10 or 20 μM) in presence or absence of autophagy inhibitor 3-Methyladenine (3-MA). The differentiation of hFOB 1.19 cells was determined via evaluating their alkaline phosphatase (ALP) activity and mineralization ability (Alizarin red staining). Alterations in autophagy-related molecules and osteogenic markers were analyzed via real-time PCR and/or immunoblotting assays.

Results

hFOB 1.19 cells spontaneously differentiated towards mature osteoblasts under 39 °C, during which CNR2 expression increased, and autophagy was activated. The strongest autophagy flux was observed at 192 h post differentiation─LC3I to LC3II conversion was enhanced and Beclin 1 expression was upregulated considerably, while p62 expression was downregulated. Treatment of HU308 and JWH133 promoted autophagy in a dose-dependent manner, and suppressed mTOR signaling pathway in hFOB 1.19 cells. In CNR2-silenced cells, HU308’s and JWH133’s effects on autophagy were weakened. HU308 and JWH133 enhanced the ALP activity and mineralization, and upregulated the expression of osteogenic markers, osteopontin and osteocalcin, in hFOB 1.19 cells. Intriguingly, such pro-osteogenic effects induced by CNR2 activation were markedly mitigated by 3-MA. In addition to provoking autophagy, CNR2 agonists also reduced nuclear Nrf2 accumulation and increased Keap1 expression. Further, re-expression of p62 inhibited CNR2 agonists-induced Nrf2 degradation.

Conclusions

Osteogenic differentiation induced by CNR2 signaling activation involves autophagy induction and p62-mediated Nrf2 deactivation.

Yap induces osteoblast differentiation by modulating Bmp signalling during zebrafish caudal fin regeneration

Osteoblast differentiation is a key process for bone homeostasis and repair. Multiple signalling pathways have been associated with osteoblast differentiation, yet much remains unknown on how this process is regulated in vivo Previous studies have proposed that the Hippo pathway transcriptional co-activators YAP and TAZ (also known as YAP1 and WWTR1, respectively) maintain progenitor stemness and inhibit terminal differentiation of osteoblasts, whereas others suggest they potentiate osteoblast differentiation and bone formation. Here, we use zebrafish caudal fin regeneration as a model to clarify how the Hippo pathway regulates de novo bone formation and osteoblast differentiation. We demonstrate that Yap inhibition leads to accumulation of osteoprogenitors and prevents osteoblast differentiation in a cell non-autonomous manner. This effect correlates with a severe impairment of Bmp signalling in osteoblasts, likely by suppressing the expression of the ligand bmp2a in the surrounding mesenchymal cells. Overall, our findings provide a new mechanism of bone formation through the Hippo-Yap pathway, integrating Yap in the signalling cascade that governs osteoprogenitor maintenance and subsequent differentiation during zebrafish caudal fin regeneration.

lncRNA H19 promotes matrix mineralization through up-regulating IGF1 by sponging miR-185-5p in osteoblasts

Background

Matrix mineralization is a key stage in bone formation involving in many bone-specific genes and signaling pathways. Emerging evidence indicate that long non-coding RNA (lncRNA) and microRNAs (miRNAs) play crucial roles in regulating the mineralization process of osteoblasts. This study aims to characterize the function and mechanism of lncRNA H19/miR-185-5p/IGF1 axis in modulating matrix mineralization of osteoblasts.

Results

H19 and IGF1 were highly expressed while miR-185-5p was lowly expressed in mineralized cells. Knocking down H19 inhibited matrix mineralization of osteoblasts, yet miR-185-5p had opposite effects. Moreover, H19 directly targeted miR-185-5p, whereas miR-185-5p repressed IGF1 expression. Meanwhile, miR-185-5p inhibition compensated the suppression of the matrix mineralization in osteoblasts by H19 knockdown.

Conclusions

The findings of this study showed that lncRNA H19 was upregulated in mineralized osteoblasts and promoted matrix mineralization through miR-185-5p/IGF1 axis in osteoblasts for the first time. This study may provide a new perspective for the diagnosis and treatment of diseases related to bone metabolism.

Salt-inducible kinase 1 regulates bone anabolism via the CRTC1-CREB-Id1 axis

New bone anabolic agents for the effective treatment of bone metabolic diseases like osteoporosis are of high clinical demand. In the present study, we reveal the function of salt-inducible kinase 1 (SIK1) in regulating osteoblast differentiation. Gene knockdown of SIK1 but not of SIK2 or SIK3 expression in primary preosteoblasts increased osteoblast differentiation and bone matrix mineralization. SIK1 also regulated the proliferation of osteoblastic precursor cells in osteogenesis. This negative control of osteoblasts required the catalytic activity of SIK1. SIK1 phosphorylated CREB regulated transcription coactivator 1 (CRTC1), preventing CRTC1 from enhancing CREB transcriptional activity for the expression of osteogenic genes like Id1. Furthermore, SIK1 knockout (KO) mice had higher bone mass, osteoblast number, and bone formation rate versus littermate wild-type (WT) mice. Preosteoblasts from SIK1 KO mice showed more osteoblastogenic potential than did WT cells, whereas osteoclast generation among KO and WT precursors was indifferent. In addition, bone morphogenic protein 2 (BMP2) suppressed both SIK1 expression as well as SIK1 activity by protein kinase A (PKA)–dependent mechanisms to stimulate osteogenesis. Taken together, our results indicate that SIK1 is a key negative regulator of preosteoblast proliferation and osteoblast differentiation and that the repression of SIK1 is crucial for BMP2 signaling for osteogenesis. Therefore, we propose SIK1 to be a useful therapeutic target for the development of bone anabolic strategies.

Orexins Facilitates Osteogenic Differentiation of MC3T3-E1 Cells

Dysfunction of osteoblastic bone formation and matrix mineralization plays a key role in the pathological development of osteoporosis. The orexin peptide orexin-A, a highly excitatory neuropeptide hormone, possesses various biological functions by activating its specific G protein-coupled receptors, orexin-1 receptor (OX1R) and orexin-2 receptor (OX2R). Here, we report that OX1R but not OX2R was expressed in MC3T3-E1 cells. Importantly, we found that orexin-A accelerated osteoblast differentiation and matrix mineralization in MC3T3-E1 cells, as manifested by elevation of physiological markers of osteoblastic differentiation [alkaline phosphatase (ALP) and osteogenic genes] and Alizarin Red staining, respectively. Importantly, our findings indicated that orexin-A significantly increased the expression of runt-related transcription factor 2 (Runx-2), which is the central transcriptional factor. Orexin-A treatment phosphorylated the kinase p38 mitogen-activated protein kinase (MAPK) in a dose- and time-dependent manner. Also, orexin-induced increase in gene expression (Runx-2, ALP, osteocalcin, and osterix) and matrix mineralization were prevented by the p38 MAPK specific inhibitor SB203580. Additionally, we also revealed that protein kinase D (PKD) is involved in the effects of Orexin-A on p38 MAPK activation and Runx-2 expression. Finally, we found that Orexin-A-induced osteoblastic formation and matrix mineralization and the activation of the PKD/p38 MAPK pathway are mediated by OX1R. Based on these findings, we concluded that activation of OX1R by orexin-A might possess a therapeutic strategy for bone disease. © 2018 IUBMB Life, 70(7):633-641, 2018.

Osteoporosis in Older Persons: Old and New Players

Osteoporosis is the most common bone disease in humans. Older persons are at higher risk of osteoporotic fractures that also result in poor quality of life, disability, loss of independence, institutionalization, and higher mortality. Osteoporosis shares a distinct pathophysiologic relationship with sarcopenia, an age-related disease comprising declines in muscle mass, strength, or function. The combination of these two diseases is known as osteosarcopenia. Understanding the pathophysiology of osteosarcopenia, in addition to its diagnostic and therapeutic approaches, is key in providing older adults with the best falls and fractures prevention strategies. This review provides updated information on new discoveries on the combined pathophysiology of osteoporosis and sarcopenia that have led to the development of novel therapeutic approaches. New recommendations for the use of risk calculators and densitometry are also presented in this review as well as evidence on current and upcoming pharmacologic treatments to prevent falls and fractures in older persons. J Am Geriatr Soc 67:831-840, 2019.

Epigallocatechin-3-Gallate Ameliorates Glucocorticoid-Induced Osteoporosis of Rats in Vivo and in Vitro

Background: Prolonged administration of overdoses of glucocorticoids results in increased bone remodeling, leading to glucocorticoid-induced osteoporosis (GIO), which is primarily due to the dysfunction and apoptosis of osteoblasts. The present study investigated the therapeutic effect and molecular mechanism of action of epigallocatechin-3-gallate (EGCG), a bioactive catechin in green tea, in high-dose dexamethasone-induced osteoblast differentiation in vivo and in vitro. Methods: The anti-dexamethasone (DEX) effects of EGCG on primary osteoblasts were determined on the basis of cell viability and alkaline phosphatase (ALP) and total cellular superoxide dismutase (SOD) activities. Flow cytometry and Western blot analysis were also used to evaluate the expression of related biomarkers in vitro, and bone microarchitecture was also extensively examined in a rat model in vivo. Results: The results showed that EGCG pretreatment significantly increased osteoblast viability and ALP and SOD activities when cells were exposed to DEX. Alizarin red staining indicated that there was more mineralization with EGCG pretreatment, countering DEX effects. EGCG reduced DEX-induced reactive oxygen species at both the mitochondrial and cellular levels in osteoblasts by activating the nuclear factor erythroid-derived 2-like-2 (Nrf2) pathway. In addition, EGCG protected osteoblasts from apoptosis. EGCG also regulated the formation of active glucocorticoid by 11β-hydroxysteroid dehydrogenase activity. Furthermore, femoral micro-computed tomography scans revealed that EGCG improved bone microstructure and mitigated DEX-induced deterioration of bone quality. Conclusion: These findings suggested that EGCG reversed GIO in rats by protecting osteoblasts by activating the Nrf2 signaling pathway.