Anabolic Therapies in Osteoporosis and Bone Regeneration

Medications Affecting Treatment Outcomes in Dentistry: Part 2

Today, it is common for medically complex patients who are receiving multiple medications, to seek routine and emergent dental care. It is essential for the practitioner to recognize and comprehend the impact of such medications on the patient's ability to tolerate the planned dental treatment and on dental treatment outcomes. An active appraisal of current literature is essential to stay abreast of emerging findings and understand their treatment implications. This article outlines the process of such active critical appraisal, illustrating key paradigms of the models that describe the impact of medications on treatment outcomes.

Mind Gaps and Bone Snaps: Exploring the Connection Between Alzheimer's Disease and Osteoporosis

PURPOSE OF REVIEW

This comprehensive review discusses the complex relationship between Alzheimer's disease (AD) and osteoporosis, two conditions that are prevalent in the aging population and result in adverse complications on quality of life. The purpose of this review is to succinctly elucidate the many commonalities between the two conditions, including shared pathways, inflammatory and oxidative mechanisms, and hormonal deficiencies.

RECENT FINDINGS

AD and osteoporosis share many aspects of their respective disease-defining pathophysiology. These commonalities include amyloid beta deposition, the Wnt/β-catenin signaling pathway, and estrogen deficiency. The shared mechanisms and risk factors associated with AD and osteoporosis result in a large percentage of patients that develop both diseases. Previous literature has established that the progression of AD increases the risk of sustaining a fracture. Recent findings demonstrate that the reverse may also be true, suggesting that a fracture early in the life course can predispose one to developing AD due to the activation of these shared mechanisms. The discovery of these commonalities further guides the development of novel therapeutics in which both conditions are targeted. This detailed review delves into the commonalities between AD and osteoporosis to uncover the shared players that bring these two seemingly unrelated conditions together. The discussion throughout this review ultimately posits that the occurrence of fractures and the mechanism behind fracture healing can predispose one to developing AD later on in life, similar to how AD patients are at an increased risk of developing fractures. By focusing on the shared mechanisms between AD and osteoporosis, one can better understand the conditions individually and as a unit, thus informing therapeutic approaches and further research. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

Foxk1 promotes bone formation through inducing aerobic glycolysis

Transcription factor Foxk1 can regulate cell proliferation, differentiation, metabolism, and promote skeletal muscle regeneration and cardiogenesis. However, the roles of Foxk1 in bone formation is unknown. Here, we found that Foxk1 expression decreased in the bone tissue of aged mice and osteoporosis patients. Knockdown of Foxk1 in primary murine calvarial osteoblasts suppressed osteoblast differentiation and proliferation. Conditional knockout of Foxk1 in preosteoblasts and mature osteoblasts in mice exhibited decreased bone mass and mechanical strength due to reduced bone formation. Mechanistically, we identified Foxk1 targeted the promoter region of many genes of glycolytic enzyme by CUT&Tag analysis. Lacking of Foxk1 in primary murine calvarial osteoblasts resulted in reducing aerobic glycolysis. Inhibition of glycolysis by 2DG hindered osteoblast differentiation and proliferation induced by Foxk1 overexpression. Finally, specific overexpression of Foxk1 in preosteoblasts, driven by a preosteoblast specific osterix promoter, increased bone mass and bone mechanical strength of aged mice, which could be suppressed by inhibiting glycolysis. In summary, these findings reveal that Foxk1 plays a vital role in the osteoblast metabolism regulation and bone formation stimulation, offering a promising approach for preventing age-related bone loss.

Enhanced vascularization and osseointegration under osteoporotic conditions through functional peptide coating on implant surfaces

Patients with osteoporosis face challenges such as decreased bone density, a sparse trabecular structure, weakened osteogenic ability, and impaired angiogenesis, leading to poor osseointegration and implant failure. Surface modification of implants with biologically active molecules possessing various functions is an effective strategy to improve osseointegration. In this study, we constructed a simple multifunctional coating interface that significantly improves osseointegration. In brief, a multifunctional coating interface was constructed by coupling the Rgd adhesive peptide, Ogp osteogenic peptide, and Ang angiogenic peptide to Lys6 (k6), which self-assembled layer by layer with TA to form the (TA-Rgd@ogp@ang)n composite membrane. This study characterized the surface morphology and biomechanical properties of the coating under both gas and liquid phases and monitored the deposition process and reaction rate of the two peptides with TA using a quartz crystal microbalance. Moreover, (TA-Rgd@ogp@ang)n exhibited a triple synergistic effect on cell migration and adhesion, osteogenic differentiation, and angiogenesis. It also ameliorated the high ROS environment characteristic of osteoporosis pathology, promoted angiogenic bone defect regeneration in osteoporosis, thereby avoiding poor osseointegration. This work provides a new approach for the prevention of implant failure in pathological environments by constructing multifunctional coatings on implants, with tremendous potential applications in the fields of orthopedics and dentistry.

Does the Outcome of Graft Materials at Dental Implant Sites Differ Between Patients With Normal and Compromised Bone Health?

The objective of this paper was to assess the outcome of bone graft material at alveolar bone augmentation sites combined with dental implants in postmenopausal women with compromised bone health by evaluating cone beam computerized tomography (CBCT) scans at multiple time points.CBCT scans were analyzed on 55 postmenopausal women with compromised bone health status to determine the fate of alveolar bone augmentation. CBCT scans were taken immediately after surgery and 9 and 24 months postoperatively. The patient's medication regimens and durations were recorded, and the pixel intensity value (PIV) was measured and standardized using scoring criteria and visual assessment. Statistical analyses included 2-sample t tests for continuous variables and Fisher's exact tests for categorical variables.Among the normal patients, 73% received a grade 2 visual score, and 27% received a grade 1 visual score. After 24 months, 45% of patients received a grade 2 score, and 27% received a grade 3 score. In the osteoporotic group receiving medication, 77% of participants received a grade 1 visual score at the 9-month postoperative evaluation, while 23% received a grade 2 score. At the 24-month assessment, 55% of patients received a grade 1 score, 41% received a grade 2 score, and only 5% received a grade 3 score. Notably, although the graft material did not remodel into native bone, it was a scaffold for implants in controlled osteoporotic patients. The study's results show that the pixel intensity values of particulate graft materials are similar across the three different time points, suggesting that the graft material's pixel intensity value remains constant in postmenopausal women with osteoporosis. The study's limitations include a small sample size and a restricted 24-month follow-up period. This limited time frame may need to capture long-term changes or variations in graft materials adequately. Future research should include a larger sample size and have a longer follow-up duration to provide a more comprehensive understanding of the change in graft materials between patients with normal and compromised bone health.

A comprehensive review and advanced biomolecule-based therapies for osteoporosis

BACKGROUND

The prevalence of osteoporosis (OP) on a global scale is significantly elevated that causes life threatening issues. The potential of groundbreaking biomolecular therapeutics in the field of OP is highly encouraging. The administration of biomolecular agents has the potential to mitigate the process of bone demineralization while concurrently augmenting the regenerative capacity of bone tissue, thereby facilitating a personalized therapeutic approach. Biomolecules-based therapies showed promising results in term of bone mass protection and restoration in OP.

AIM OF REVIEW

We summarized the recent biomolecular therapies with notable progress in clinical, demonstrating the potential to transform illness management. These treatments frequently utilize different biomolecule based strategies. Biomolecular therapeutics has a targeted character, which results in heightened specificity and less off-target effects, ultimately leading to increased patient outcomes. These aspects have the capacity to greatly enhance the management of OP, thus resulting in a major enhancement in the quality of life encountered by individuals affected by this condition.

Musculoskeletal crosstalk in chronic obstructive pulmonary disease and comorbidities: Emerging roles and therapeutic potentials

Chronic Obstructive Pulmonary Disease (COPD) is a multifaceted respiratory disorder characterized by progressive airflow limitation and systemic implications. It has become increasingly apparent that COPD exerts its influence far beyond the respiratory system, extending its impact to various organ systems. Among these, the musculoskeletal system emerges as a central player in both the pathogenesis and management of COPD and its associated comorbidities. Muscle dysfunction and osteoporosis are prevalent musculoskeletal disorders in COPD patients, leading to a substantial decline in exercise capacity and overall health. These manifestations are influenced by systemic inflammation, oxidative stress, and hormonal imbalances, all hallmarks of COPD. Recent research has uncovered an intricate interplay between COPD and musculoskeletal comorbidities, suggesting that muscle and bone tissues may cross-communicate through the release of signalling molecules, known as "myokines" and "osteokines". We explored this dynamic relationship, with a particular focus on the role of the immune system in mediating the cross-communication between muscle and bone in COPD. Moreover, we delved into existing and emerging therapeutic strategies for managing musculoskeletal disorders in COPD. It underscores the development of personalized treatment approaches that target both the respiratory and musculoskeletal aspects of COPD, offering the promise of improved well-being and quality of life for individuals grappling with this complex condition. This comprehensive review underscores the significance of recognizing the profound impact of COPD on the musculoskeletal system and its comorbidities. By unravelling the intricate connections between these systems and exploring innovative treatment avenues, we can aspire to enhance the overall care and outcomes for COPD patients, ultimately offering hope for improved health and well-being.

Increased β2-adrenergic signaling promotes fracture healing through callus neovascularization in mice

Traumatic brain injury (TBI) leads to skeletal changes, including bone loss in the unfractured skeleton, and paradoxically accelerates healing of bone fractures; however, the mechanisms remain unclear. TBI is associated with a hyperadrenergic state characterized by increased norepinephrine release. Here, we identified the β2-adrenergic receptor (ADRB2) as a mediator of skeletal changes in response to increased norepinephrine. In a murine model of femoral osteotomy combined with cortical impact brain injury, TBI was associated with ADRB2-dependent enhanced fracture healing compared with osteotomy alone. In the unfractured 12-week-old mouse skeleton, ADRB2 was required for TBI-induced decrease in bone formation and increased bone resorption. Adult 30-week-old mice had higher bone concentrations of norepinephrine, and ADRB2 expression was associated with decreased bone volume in the unfractured skeleton and better fracture healing in the injured skeleton. Norepinephrine stimulated expression of vascular endothelial growth factor A and calcitonin gene-related peptide-α (αCGRP) in periosteal cells through ADRB2, promoting formation of osteogenic type-H vessels in the fracture callus. Both ADRB2 and αCGRP were required for the beneficial effect of TBI on bone repair. Adult mice deficient in ADRB2 without TBI developed fracture nonunion despite high bone formation in uninjured bone. Blocking ADRB2 with propranolol impaired fracture healing in mice, whereas the ADRB2 agonist formoterol promoted fracture healing by regulating callus neovascularization. A retrospective cohort analysis of 72 patients with long bone fractures indicated improved callus formation in 36 patients treated with intravenous norepinephrine. These findings suggest that ADRB2 is a potential therapeutic target for promoting bone healing.

Restoring implant fixation strength in osteoporotic bone with a hydrogel locally delivering zoledronic acid and bone morphogenetic protein 2. A longitudinal in vivo microCT study in rats

Osteoporosis poses a major public health challenge, and it is characterized by low bone mass, deterioration of the microarchitecture of bone tissue, causing a consequent increase in bone fragility and susceptibility to fractures and complicating bone fixation, particularly screw implantation. In the present study, our aim was to improve implant stability in osteoporotic bone using a thermoresponsive hyaluronan hydrogel (HA-pNIPAM) to locally deliver the bisphosphonate zoledronic acid (ZOL) to prevent bone resorption and bone morphogenetic protein 2 (BMP2) to induce bone formation. Adult female Wistar rats (n = 36) were divided into 2 treatment groups: one group of SHAM-operated animals and another group that received an ovariectomy (OVX) to induce an osteoporotic state. All animals received a polyetheretherketone (PEEK) screw in the proximal tibia. In addition, subgroups of SHAM or OVX animals received either the HA-pNIPAM hydrogel without or with ZOL/BMP2, placed into the defect site prior to screw implantation. Periprosthetic bone and implant fixation were monitored using longitudinal in vivo microCT scanning post-operatively and at 3, 6, 9, 14, 20 and 28 days. Histological assessment was performed post-mortem. Our data showed that pure hydrogel has no impact of implant fixation The ZOL/BMP2-hydrogel significantly increased bone-implant contact and peri-implant bone fraction, primarily through reduced resorption. STATEMENT OF CLINICAL SIGNIFICANCE: Local delivery of ZOL and BMP2 using a biocompatible hydrogel improved implant stability in osteoporotic bone. This approach could constitute a potent alternative to systemic drug administration and may be useful in avoiding implant loosening in clinical settings.

From the Mind to the Spine: The Intersecting World of Alzheimer's and Osteoporosis

PURPOSE OF REVIEW

This comprehensive review delves into the intricate interplay between Alzheimer's disease (AD) and osteoporosis, two prevalent conditions with significant implications for individuals' quality of life. The purpose is to explore their bidirectional association, underpinned by common pathological processes such as aging, genetic factors, inflammation, and estrogen deficiency.

RECENT FINDINGS

Recent advances have shown promise in treating both Alzheimer's disease (AD) and osteoporosis by targeting disease-specific proteins and bone metabolism regulators. Monoclonal antibodies against beta-amyloid and tau for AD, as well as RANKL and sclerostin for osteoporosis, have displayed therapeutic potential. Additionally, ongoing research has identified neuroinflammatory genes shared between AD and osteoporosis, offering insight into the interconnected inflammatory mechanisms. This knowledge opens avenues for innovative dual-purpose therapies that could address both conditions, potentially revolutionizing treatment approaches for AD and osteoporosis simultaneously. This review underscores the potential for groundbreaking advancements in early diagnosis and treatment by unraveling the intricate connection between AD and bone health. It advocates for a holistic, patient-centered approach to medical care that considers both cognitive and bone health, ultimately aiming to enhance the overall well-being of individuals affected by these conditions. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

The Role of TAM Receptors in Bone

The TAM (TYRO3, MERTK, and AXL) family of receptor tyrosine kinases are pleiotropic regulators of adult tissue homeostasis maintaining organ integrity and self-renewal. Disruption of their homeostatic balance fosters pathological conditions like autoinflammatory or degenerative diseases including rheumatoid arthritis, lupus erythematodes, or liver fibrosis. Moreover, TAM receptors exhibit prominent cell-transforming properties, promoting tumor progression, metastasis, and therapy resistance in various cancer entities. Emerging evidence shows that TAM receptors are involved in bone homeostasis by regulating osteoblastic bone formation and osteoclastic bone resorption. Therefore, TAM receptors emerge as new key players of the regulatory cytokine network of osteoblasts and osteoclasts and represent accessible targets for pharmacologic therapy for a broad set of different bone diseases, including primary and metastatic bone tumors, rheumatoid arthritis, or osteoporosis.

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.

G-protein coupled receptor 5C (GPRC5C) is required for osteoblast differentiation and responds to EZH2 inhibition and multiple osteogenic signals

Osteoblast differentiation is epigenetically suppressed by the H3K27 methyltransferase EZH2, and induced by the morphogen BMP2 and transcription factor RUNX2. These factors also regulate distinct G protein coupled receptors (GPRCs; e.g., PTH1R, GPR30/GPER1). Because GPRCs transduce many physiological stimuli, we examined whether BMP2 or EZH2 inhibition (i.e., GSK126) regulates other GPRC genes in osteoblasts. RNA-seq screening of >400 mouse GPRC-related genes showed that many GPRCs are downregulated during osteogenic differentiation. The orphan receptor GPRC5C, along with a small subset of other GPRCs, is induced by BMP2 or GSK126 during Vitamin C dependent osteoblast differentiation, but not by all-trans retinoic acid. ChIP-seq analysis revealed that GSK126 reduces H3K27me3 levels at the GPRC5C gene locus in differentiating MC3T3-E1 osteoblasts, consistent with enhanced GPRC5C mRNA expression. Loss of function analyses revealed that shRNA-mediated depletion of GPRC5C decreases expression of bone markers (e.g., BGLAP and IBSP) and mineral deposition in response to BMP2 or GSK126. GPRC5C mRNA was found to be reduced in the osteopenic bones of KLF10 null mice which have compromised BMP2 signaling. GPRC5C mRNA is induced by the bone-anabolic activity of 17β-estradiol in trabecular but not cortical bone following ovariectomy. Collectively, these findings suggest that GPRC5C protein is a key node in a pro-osteogenic axis that is normally suppressed by EZH2-mediated H3K27me3 marks and induced during osteoblast differentiation by GSK126, BMP2, and/or 17β-estradiol. Because GPRC5C protein is an understudied orphan receptor required for osteoblast differentiation, identification of ligands that induce GPRC5C signaling may support therapeutic strategies to mitigate bone-related disorders.

Investigation of Giant Cell Tumor of Bone and Tissue Engineering Approaches for the Treatment of Giant Cell Tumor of Bone

Primary bone tumors such as Ewing sarcoma, osteosarcoma, and chondrosarcoma, secondary bone tumors developed from progressive malignancies, and metastasized bone tumors are more prevalent and studied descriptively through biology and medical research. Less than 0.2% of cancer diagnoses are caused by rare bone-originating tumors, which despite being rare are particularly difficult due to their high death rates and substantial disease burden. A giant cell tumor of bone (GCTB) is an intramurally invasive but rare and benign type of bone tumor, which seldom metastasizes. The most often prescribed medication for GCTB is Denosumab, a RANKL (receptor activator of nuclear factor κB ligand) inhibitor. Because pharmaceutical drug companies rely on two-dimensional and animal models, current approaches for investigating the diverse nature of tumors are insufficient. Cell line based medication effectiveness and toxicity studies cannot predict tumor response to antitumor medicines. It has already been investigated in detail why molecular pathways do not reproduce in vitro, a phenomenon known as flat biology. Due to physiological differences between human beings and animals, animal models do not succeed in identifying side effects of the treatment, emulating metastatic growth, and establishing the link between cancer and the immune system. This review summarizes and discusses GCTB, the disease, its cellular composition, various bone tumor models, and their properties and utilization in research. As a result, this study delves deep into in vitro testing, which is vital for scientists and physicians in various fields, including pharmacology, preclinical investigations, tissue engineering, and regenerative medicine.

Increased beta2-adrenergic signaling is a targetable stimulus essential for bone healing by promoting callus neovascularization

Traumatic brain injury (TBI) is associated with a hyperadrenergic state and paradoxically causes systemic bone loss while accelerating fracture healing. Here, we identify the beta2-adrenergic receptor (Adrb2) as a central mediator of these skeletal manifestations. While the negative effects of TBI on the unfractured skeleton can be explained by the established impact of Adrb2 signaling on bone formation, Adrb2 promotes neovascularization of the fracture callus under conditions of high sympathetic tone, including TBI and advanced age. Mechanistically, norepinephrine stimulates the expression of Vegfa and Cgrp primarily in periosteal cells via Adrb2, both of which synergistically promote the formation of osteogenic type-H vessels in the fracture callus. Accordingly, the beneficial effect of TBI on bone repair is abolished in mice lacking Adrb2 or Cgrp, and aged Adrb2-deficient mice without TBI develop fracture nonunions despite high bone formation in uninjured bone. Pharmacologically, the Adrb2 antagonist propranolol impairs, and the agonist formoterol promotes fracture healing in aged mice by regulating callus neovascularization. Clinically, intravenous beta-adrenergic sympathomimetics are associated with improved callus formation in trauma patients with long bone fractures. Thus, Adrb2 is a novel target for promoting bone healing, and widely used beta-blockers may cause fracture nonunion under conditions of increased sympathetic tone.

Abstract Figure

Influence of bisphosphonate treatment on bone substitute performance in osteoporotic conditions

OBJECTIVE

Considering the elevated number of osteoporotic patients in need of bone graft procedures, we here evaluated the effect of alendronate (ALN) treatment on the regeneration of bone defects in osteoporotic rats. Bone formation was histologically and histomorphometrically assessed in rat femoral condyle bone defects filled with bone graft (Bio-Oss®) or left empty.

METHODS

Male Wistar rats were induced osteoporotic through orchidectomy (ORX) and SHAM-operated. The animals were divided into three groups: osteoporotic (ORX), osteoporotic treated with ALN (ORX + ALN) and healthy (SHAM). Six weeks after ORX or SHAM surgeries, bone defects were created bilaterally in femoral condyles; one defect was filled with Bio-Oss® and the other one left empty. Bone regeneration within the defects was analyzed by histology and histomorphometry after 4 and 12 weeks.

RESULTS

Histological samples showed new bone surrounding Bio-Oss® particles from week 4 onward in all three groups. At week 12, the data further showed that ALN treatment of osteoporotic animals enhanced bone formation to a 10-fold increase compared to non-treated osteoporotic control. Bio-Oss® filling of the defects promoted bone formation at both implantation periods compared to empty controls.

CONCLUSION

Our histological and histomorphometric results demonstrate that the enteral administration of alendronate under osteoporotic bone conditions leverages bone defect regeneration to a level comparable to that in healthy bone. Additionally, Bio-Oss® is an effective bone substitute, increasing bone formation, and acting as an osteoconductive scaffold guiding bone growth in both healthy and osteoporotic bone conditions.

SIGNIFICANCE

Based on the results of this study, enteral use of ALN mitigates adverse effects of an osteoporotic condition on bone defect regeneration.

ERK-estrogen receptor α signaling plays a role in the process of bone marrow mesenchymal stem cell-derived exosomes protecting against ovariectomy-induced bone loss

BACKGROUND

Exosomes derived from bone marrow mesenchymal stem cells (BMSC-Exos) are considered as candidates for osteoporosis (OP) therapy. Estrogen is critical in the maintenance of bone homeostasis. However, the role of estrogen and/or its receptor in BMSC-Exos treatment of OP, as well as its methods of regulation during this process remain unclear.

METHODS

BMSCs were cultured and characterized. Ultracentrifugation was performed to collect BMSC-Exos. Transmission electron microscopy, nanoparticle tracking analysis, and western blotting were used to identify BMSC-Exos. We examined the effects of BMSC-Exos on the proliferation, osteogenic differentiation, mineralization, and cell cycle distribution of MG-63 cells. The protein expression of estrogen receptor α (ERα) and the phosphorylation of ERK were investigated through western blotting. We determined the effects of BMSC-Exos on the prevention of bone loss in female rats. The female Sprague-Dawley rats were divided into three groups: the sham group, ovariectomized (OVX) group, and the OVX + BMSC-Exos group. Bilateral ovariectomy was performed in the OVX and OVX + BMSC-Exos groups, while a similar volume of adipose tissue around the ovary was removed in the sham group. The rats in OVX group and OVX + BMSC-Exos group were given PBS or BMSC-Exos after 2 weeks of surgery. Micro-CT scanning and histological staining were used to evaluate the in vivo effects of BMSC-Exos.

RESULTS

BMSC-Exos significantly enhanced the proliferation, alkaline phosphatase activity, and the Alizarin red S staining in MG-63 cells. The results of cell cycle distribution demonstrated that BMSC-Exos increased the proportion of cells in the G2 + S phase and decreased the proportion of cells in the G1 phase. Moreover, PD98059, an inhibitor of ERK, inhibited both the activation of ERK and the expression of ERα, which were promoted by administration of BMSC-Exos. Micro-CT scan showed that in the OVX + BMSC-Exos group, bone mineral density, bone volume/tissue volume fraction, trabecular number were significantly upregulated. Additionally, the microstructure of the trabecular bone was preserved in the OVX + BMSC-Exos group compared to that in the OVX group.

CONCLUSION

BMSC-Exos showed an osteogenic-promoting effect both in vitro and in vivo, in which ERK-ERα signaling might play an important role.

Long Non-Coding RNA Malat1 Increases the Rescuing Effect of Quercetin on TNFα-Impaired Bone Marrow Stem Cell Osteogenesis and Ovariectomy-Induced Osteoporosis

Osteoporosis, a common systematic bone homeostasis disorder related disease, still urgently needs innovative treatment methods. Several natural small molecules were found to be effective therapeutics in osteoporosis. In the present study, quercetin was screened out from a library of natural small molecular compounds by a dual luciferase reporter system. Quercetin was found to upregulate Wnt/β-catenin while inhibiting NF-κB signaling activities, and thereby rescuing osteoporosis-induced tumor necrosis factor alpha (TNFα) impaired BMSCs osteogenesis. Furthermore, a putative functional lncRNA, Malat1, was shown to be a key mediator in quercetin regulated signaling activities and TNFα-impaired BMSCs osteogenesis, as mentioned above. In an ovariectomy (OVX)-induced osteoporosis mouse model, quercetin administration could significantly rescue OVX-induced bone loss and structure deterioration. Serum levels of Malat1 were also obviously rescued in the OVX model after quercetin treatment. In conclusion, our study demonstrated that quercetin could rescue TNFα-impaired BMSCs osteogenesis in vitro and osteoporosis-induced bone loss in vivo, in a Malat1-dependent manner, suggesting that quercetin may serve as a therapeutic candidate for osteoporosis treatment.

Efficacy, Mechanism, and Structure-Activity Relationship of 6-Methoxy Benzofuran Derivatives as a Useful Tool for Senile Osteoporosis

Most patients with senile osteoporosis (SOP) are severely deficient in bone mass, and treatments using bone resorption inhibitors, such as bisphosphonates, have shown limited efficacy. Small-molecule osteogenesis-promoting drugs are required to improve the treatment for this disease. Previously, we demonstrated that a compound with a benzofuran-like structure promoted bone formation by upregulating BMP-2, and it exhibited a therapeutic effect in SAMP-6 mice, glucocorticoid-induced osteoporosis rats, and ovariectomized rats. In this study, aged C57 and SAMP-6 mice models were used to investigate the therapeutic and preventive effects of compound 125 on SOP. scRNA-seq analysis showed that BMP-2 upregulation is the mechanism through which 125 accelerates bone turnover and increases the proportion of osteoblasts. We evaluated the structure-activity relationship of the candidate drugs and found that the derivative I-9 showed significantly higher efficacy than 125 and teriparatide in the zebrafish osteoporosis model. This study provides a foundation for the development of SOP drugs.

The Local Release of Teriparatide Incorporated in 45S5 Bioglass Promotes a Beneficial Effect on Osteogenic Cells and Bone Repair in Calvarial Defects in Ovariectomized Rats

With the increase in the population's life expectancy, there has also been an increase in the rate of osteoporosis, which has expanded the search for strategies to regenerate bone tissue. The ultrasonic sonochemical technique was chosen for the functionalization of the 45S5 bioglass. The samples after the sonochemical process were divided into (a) functionalized bioglass (BG) and (b) functionalized bioglass with 10% teriparatide (BGT). Isolated mesenchymal cells (hMSC) from femurs of ovariectomized rats were differentiated into osteoblasts and submitted to in vitro tests. Bilateral ovariectomy (OVX) and sham ovariectomy (Sham) surgeries were performed in fifty-five female Wistar rats. After a period of 60 days, critical bone defects of 5.0 mm were created in the calvaria of these animals. For biomechanical evaluation, critical bone defects of 3.0 mm were performed in the tibias of some of these rats. The groups were divided into the clot (control) group, the BG group, and the BGT group. After the sonochemical process, the samples showed modified chemical topographic and morphological characteristics, indicating that the surface was chemically altered by the functionalization of the particles. The cell environment was conducive to cell adhesion and differentiation, and the BG and BGT groups did not show cytotoxicity. In addition, the experimental groups exhibited characteristics of new bone formation with the presence of bone tissue in both periods, with the BGT group and the OVX group statistically differing from the other groups (p < 0.05) in both periods. Local treatment with the drug teriparatide in ovariectomized animals promoted positive effects on bone tissue, and longitudinal studies should be carried out to provide additional information on the biological performance of the mutual action between the bioglass and the release of the drug teriparatide.

WNT-modulating gene silencers as a gene therapy for osteoporosis, bone fracture, and critical-sized bone defects

Treating osteoporosis and associated bone fractures remains challenging for drug development in part due to potential off-target side effects and the requirement for long-term treatment. Here, we identify recombinant adeno-associated virus (rAAV)-mediated gene therapy as a complementary approach to existing osteoporosis therapies, offering long-lasting targeting of multiple targets and/or previously undruggable intracellular non-enzymatic targets. Treatment with a bone-targeted rAAV carrying artificial microRNAs (miRNAs) silenced the expression of WNT antagonists, schnurri-3 (SHN3), and sclerostin (SOST), and enhanced WNT/β-catenin signaling, osteoblast function, and bone formation. A single systemic administration of rAAVs effectively reversed bone loss in both postmenopausal and senile osteoporosis. Moreover, the healing of bone fracture and critical-sized bone defects was also markedly improved by systemic injection or transplantation of AAV-bound allograft bone to the osteotomy sites. Collectively, our data demonstrate the clinical potential of bone-specific gene silencers to treat skeletal disorders of low bone mass and impaired fracture repair.

Global cannabinoid receptor 1 deficiency affects disuse-induced bone loss in a site-specific and sex-dependent manner

Bone loss during mechanical unloading increases fracture risk and is a major concern for the general population and astronauts during spaceflight. The endocannabinoid system (ECS) plays an important role in bone metabolism. One of the main ECS receptors, cannabinoid receptor 1 (CB1), has been studied in regards to basic bone metabolism; however, little is known as to how CB1 and the ECS affect bone in different mechanical environments. In this study, we analyzed the influence of global CB1 deficiency and sex on mice during disuse caused by single limb immobilization. Female mice were more sensitive to disuse-induced BV/TV loss than males in both the femoral metaphysis and tibial epiphysis. Genotype also affected bone loss in a sex-dependent manner, with male mice deficient in CB1 receptors (CB1KO) and female wildtype (WT) mice experiencing increased bone loss in both the tibial metaphysis and femoral epiphysis. Genotype affected the response to disuse as CB1KO mice displayed greater changes in femoral ultimate force, along with lower tibial ultimate stress, compared to WT mice. Female mice had a significantly higher femoral, and lower tibial ultimate force compared to male mice. These results reveal that disuse-induced bone loss due to CB1 deficiency is sex-dependent. CB1 deficiency in male mice exacerbated bone loss, while in females CB1 deficiency appeared to protect against disuse-induced bone loss. Regardless of genotype, female mice were more sensitive than males to disuse. These results suggest that CB1 receptors may represent a potential therapeutic target for mitigation of disuse-induced bone loss.

Suffruticosol A elevates osteoblast differentiation targeting BMP2-Smad/1/5/8-RUNX2 in pre-osteoblasts

The Paeonia suffruticosa ANDR. (P. suffruticosa) is commonly used in traditional medicine for various purposes. Suffruticosol A (Suf-A), isolated from P. suffruticosa, is a beneficial compound with antibiofilm, antivirulence, and anti-inflammatory properties. The aim of the present study was to investigate the biological effects of Suf-A on osteogenic processes in pre-osteoblasts. It was determined here in that Suf-A (>98.02%), isolated from P. suffruticosa, showed no cytotoxicity at 0.1-30 μM; however, it induced cytotoxicity at 50-100 μM in pre-osteoblasts. Suf-A increased osteogenic alkaline phosphatase activity and expression levels of noncollagenous proteins. Adhesion and trans-migration on the extracellular matrix were potentiated by Suf-A, but not by wound-healing migration. Suf-A did not affect autophagy or necroptosis during osteoblast differentiation. We found that Suf-A increased runt-related transcription factor 2 (RUNX2) levels and mineralized matrix formation. RUNX2 expression was mediated by Suf-A-induced BMP2-Smad1/5/8 and mitogen-activated protein kinase signaling, as demonstrated by Noggin, a BMP2 inhibitor. These results suggest that Suf-A is a potential natural osteogenic compound.

Strontium-Incorporated Carbon Nitride Nanosheets Modulate Intracellular Tension for Reinforced Bone Regeneration

Strontium-containing agents have been demonstrated to elicit both bone anabolic and antiosteoporotic effects, showing great potential for the treatment of bone loss. However, an increased incidence of strontium-induced side effects restricts their clinical applications. Herein, oxidized carbon nitride nanosheets (CN) are delicately used to incorporate Sr²⁺ for the first time to achieve high osteogenic efficacy. The lamellar structure and enriched nitrogen species of CN provide them with a high surface area-to-volume ratio and abundant anchoring sites for Sr²⁺ incorporation. Importantly, Sr²⁺-incorporated CN (CNS) could synergistically promote osteoblast differentiation and bone regeneration at a single, very low Sr²⁺ dose. Mechanically, CNS could activate the FAK/RhoA signaling pathway to modulate the intracellular tension that stimulates osteoblasts differentiation. The present study will provide a new paradigm to enhance the efficacy of osteogenic metal ions by using lamellar nanocarriers.

Strontium-doping promotes bone bonding of titanium implants in osteoporotic microenvironment

Osteoporosis is a major challenge to oral implants, and this study focused on improving the osseointegration ability of titanium (Ti) implants in osteoporosis environment via surface modification, including doping of strontium ion and preparation of nanoscale surface feature. Our previous studies have shown that strontium (Sr) ions can enhance osteogenic activity. Therefore, we aimed to comprehensively evaluate the effect of hydrothermal treatment of Sr-doped titanium implant coating on bone-binding properties in the microenvironment of osteoporosis in this study. We fabricated Sr-doped nanocoating (AHT-Sr) onto the surface of titanium implants via hydrothermal reaction. The rough Sr-doping had good biological functions and could apparently promote osteogenic differentiation of osteoporotic bone marrow mesenchymal stem cells (OVX-BMSCs). Most importantly, AHT-Sr significantly promoted bone integration in the osteoporosis environment. This study provides an effective approach to implant surface modification for better osseointegration in an osteoporotic environment.

pH-Sensitive nanocarrier assisted delivery of adenosine to treat osteoporotic bone loss

Bone tissue undergoes continuous remodeling via osteoclast-mediated bone resorption and osteoblast-mediated bone formation. An imbalance in this process with enhanced osteoclastic activity can lead to excessive bone resorption, resulting in bone thinning. Once activated, osteoclasts bind to the bone surface and acidify the local niche. This acidic environment could serve as a potential trigger for the delivery of therapeutic agents into the osteoporotic bone tissue. To this end, we developed a pH-responsive nanocarrier-based drug delivery system that binds to the bone tissue and delivers an osteoanabolic molecule, adenosine. Adenosine is incorporated into a hyaluronic acid (HA)-based nanocarrier through a pH-sensitive ketal group. The HA-nanocarrier is further functionalized with alendronate moieties to improve binding to the bone tissues. Systemic administration of the nanocarrier containing adenosine attenuated bone loss in ovariectomized mice and showed comparable bone qualities to that of healthy mice. Delivery of osteoanabolic small molecules that can contribute to bone formation and inhibit excessive osteoclast activity by leveraging the tissue-specific milieu could serve as viable therapeutics for osteoporosis.

Treatment of Diabetes and Osteoporosis—A Reciprocal Risk?

Diabetes mellitus is a metabolic and systematic disorder that requires individualized therapy. The disease leads to various consequences, resulting in the destruction of tissues and organs. The aforementioned outcomes also include bone mineral disorders, caused by medications as well as diet therapy and physical activity. Some drugs may have a beneficial effect on both bone mineral density and the risk of fractures. Nevertheless, the impact of other medications remains unknown. Focusing on pharmacotherapy in diabetes may prevent bone mineral disorders and influence both the treatment and quality of life in patients suffering from diabetes mellitus. On the other hand, anti-osteoporosis drugs, such as antiresorptive or anabolic drugs, as well as drugs with a mixed mechanism of action, may affect carbohydrate metabolism, particularly in patients with diabetes. Therefore, the treatment of diabetes as well as osteoporosis prevention are vital for this group of patients.

Dual Targeting Anti-Osteoporotic Therapy through Potential Nanotherapeutic Approaches

Osteoporosis is characterised by a major public health burden, particularly taking into account the ageing global population. Therapeutic modalities for osteoporosis are categorised on the basis of their effect on bone remodeling: antiresorptive agents and anabolic agents. Anabolic drugs are favoured as they promote the formation of new bone, whereas antiresorptive drugs terminate the further deterioration of bone. Non-specific delivery of anabolic agents results in prolonged kidney exposure causing malignant hypercalcemia, whereas antiresorptive agents and bisphosphonates may produce osteonecrosis of the jaw. Several clinical trials have been reported for combinational therapy of anabolic agents and antiresorptive agents for osteoporosis. However, none of them have proven their cumulative effectiveness in the treatment of disease. The present work emphasizes on dual-targeting drug delivery approach comprising of bone anabolic and antiresorptive agents that would deliver the therapeutic agents to both the zones of bone simultaneously. The anticipated pioneering delivery approach will intensify the explicit interaction between the therapeutic agent and bone surfaces separately without developing severe adverse effects and improve the osteoporotic therapy effectively compared to non-targeted drug delivery.

BMP2 as a promising anticancer approach: functions and molecular mechanisms

Bone morphogenetic protein 2 (BMP2), a pluripotent factor, is a member of the transforming growth factor-beta (TGF-β) superfamily and is implicated in embryonic development and postnatal homeostasis in tissues and organs. Experimental research in the contexts of physiology and pathology has indicated that BMP2 can induce macrophages to differentiate into osteoclasts and accelerate the osteolytic mechanism, aggravating cancer cell bone metastasis. Emerging studies have stressed the potent regulatory effect of BMP2 in cancer cell differentiation, proliferation, survival, and apoptosis. Complicated signaling networks involving multiple regulatory proteins imply the significant biological functions of BMP2 in cancer. In this review, we comprehensively summarized and discussed the current evidence related to the modulation of BMP2 in tumorigenesis and development, including evidence related to the roles and molecular mechanisms of BMP2 in regulating cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), cancer angiogenesis and the tumor microenvironment (TME). All these findings suggest that BMP2 may be an effective therapeutic target for cancer and a new marker for assessing treatment efficacy.

GPR109A gene deletion ameliorates gonadectomy-induced bone loss in mice

Sex steroid deficiency plays critical roles in the pathophysiology of bone as the result of uncertain bone remodeling, i.e., increased bone resorption with equivocal bone formation. We have previously shown that GPR109A, a G protein coupled receptor, controls osteoclastogenesis and bone resorption, where global GPR109A deletion decreased osteoclast bone resorption and increased bone mass. Here, we used global GPR109A gene deletion, ovariectomized (OVX) and orchidectomized (ORX) mouse models to probe the role of GPR109A in gonadectomy-induced bone loss in female and male mice. Six months old GPR109A^-/- mice and their wild type littermates were allocated to Sham or gonadectomized groups for six weeks. Using densitometric micro-CT confirmed by peripheral quantitative CT (pQCT) scans on tibia and spine, and three-point bending test on femur ex vivo, we found the bone volume, trabecular number, as well as bone mineral density and content in both trabecular and cortical sites were significantly decreased in wild type OVX and ORX compared with respective Sham groups. While bone mass in both male and female GPR109A^-/- Sham groups were significantly higher compared with their respective wild type Sham groups, global GPR109A gene deletion ameliorated gonadectomy-induced bone loss. In GPR109A^-/- females, most of bone mass and strength parameters measured by micro-CT, pQCT and three-point bending test were not different between Sham and OVX groups. In wild type but not in GPR109^-/- mice, bone remodeling marker measurements indicated that both bone resorption (Cathepsin K) and bone formation (osteocalcin) markers were increased in gonadectomized mice compared to sham, with the exception of bone specific ALP, which was decreased in gonadectomized mice. Expression of bone resorption markers (Cathepsin K) were significantly lower, but β-catenin expression was higher in GPR109A^-/- mice compared with their wild type littermates. Collectively, these data indicate that global GPR109A deletion ameliorates gonadectomy-induced bone loss through suppression of bone resorption.

Oral Administration of Isovitexin, a Naturally Occurring Apigenin Derivative Showed Osteoanabolic Effect in Ovariectomized Mice: A Comparative Study with Teriparatide

Isovitexin (apigenin-6C-glucopyranose) is found in several food items and medicinal plants. Recently, we showed that isovitexin stimulated osteoblast differentiation through mitochondrial biogenesis and respiration that required adiponectin receptors (AdipoRs). Here, we studied whether oral isovitexin has a bone anabolic effect in vivo. At first, using a femur osteotomy model in adult mice, we compared the bone regenerative effect of isovitexin and apigenin. Whereas isovitexin-stimulated bone formation at the osteotomy site at 2.5 mg/kg and 5 mg/kg dose, apigenin had no effect. Subsequently, we tested the effect of isovitexin (5 mg/kg) in ovariectomized (OVX) osteopenic mice and observed that it restored bone mass and architecture of trabecular bones (femur metaphysis and fifth lumbar vertebra/L5) and cortical bones (femur diaphysis). Isovitexin completely restored bone strength at L5 (compressive strength) and femur (bending strength) in OVX mice. The bone anabolic effect of isovitexin was demonstrated by the increased surface referent bone formation parameters, increased expression of osteogenic genes (Runx2, bone morphogenetic protein-2 and type 1 collagen) in bones, and increased serum procollagen type 1N-terminal propeptide in OVX mice and these were on a par with teriparatide. Isovitexin inhibited bone and serum sclerostin as well as the serum type I collagen cross-linked C-telopeptide in OVX mice. Isovitexin has an oral bioavailability of 14.58%. Taken together, our data show that isovitexin had a significant oral bioavailability that translated to osteoanabolic effect equivalent to teriparatide and inhibited bone resorption, which implied a durable effect over teriparatide.

Effects of Scoparone on differentiation, adhesion, migration, autophagy and mineralization through the osteogenic signalling pathways

Scoparone (SCOP), an active and efficient coumarin compound derived from Artemisia capillaris Thunb, has been used as a traditional Chinese herbal medicine. Herein, we investigated the effects of SCOP on the osteogenic processes using MC3T3‐E1 pre‐osteoblasts in in vitro cell systems. SCOP (C₁₁H₁₀O₄, > 99.17%) was purified and identified from A. capillaries. SCOP (0.1 to 100 μM concentrations) did not have cytotoxic effects in pre‐osteoblasts; however, it promoted alkaline phosphatase (ALP) staining and activity, and mineralized nodule formation under early and late osteogenic induction. SCOP elevated osteogenic signals through the bone morphogenetic protein 2 (BMP2)‐Smad1/5/8 pathway, leading to the increased expression of runt‐related transcription factor 2 (RUNX2) with its target protein, matrix metallopeptidase 13 (MMP13). SCOP also induced the non‐canonical BMP2‐MAPKs pathway, but not the Wnt3a‐β‐catenin pathway. Moreover, SCOP promoted autophagy, migration and adhesion under the osteogenic induction. Overall, the findings of this study demonstrated that SCOP has osteogenic effects associated with cell differentiation, adhesion, migration, autophagy and mineralization.

Structural characterization of a mannoglucan polysaccharide from Dendrobium huoshanense and evaluation of its osteogenesis promotion activities

Dendrobium huoshanense, a valuable traditional Chinese herb, is widely used to prolong life in China. Our study aims to characterize the structure and osteogenesis-promotion effects of a heteropolysaccharide component isolated from Dendrobium huoshanense (DHPW1). The structure of DHPW1 was characterized using gas chromatography-mass spectrometry and nuclear magnetic resonance, while its osteogenic activity was evaluated using MG-63 cells and zebrafish skulls. The results showed that the molecular weight of DHPW1 was 230 kDa and it was mainly composed of mannose and glucose. In addition, the DHPW1 backbone consisted of (1 → 4)-linked-β-D-Mannopyranosyl and (1 → 4)-linked-β-d-Glucopyranosyl. Furthermore, DHPW1 significantly increased ALP activity and mineralized nodule formation in MG-63 cells. DHPW1 in zebrafish skull models significantly enhanced the relative fluorescence intensity of bone mass and increased the degree of bone mineralization. These results suggested that the DHPW1 component in D. huoshanense has potential to promote osteogenesis.

Clinical Parameters in Osteoporosis Patients Supplemented With PMA-Zeolite at the End of 5-Year Double-Blinded Clinical Trial

Osteoporosis is among the most common pathologies. Associated complications in osteoporotic patients, in particular hip fractures and vertebral fractures, cause disabilities and significant quality of life deterioration. Standard treatment of osteoporosis, based on pharmacotherapy does still not yield adequate results, and the problem of osteoporosis remains incompletely solved. Additionally, adverse drug events and fractures after long-termed pharmacotherapy pose additional challenges within designing a proper therapy regimen. Improved clinical approach and new synergistic treatment modalities are consequently still needed. The rationale of the presented study was accordingly, to expand our preclinical animal study on human patients with osteoporosis, based on positive effects on bones observed in animals with osteopenia treated with PMA-zeolite. We specifically monitored effects of PMA-zeolite on the bone quality parameters, fracture risk and quality of life in a cohort of initially recruited 100 osteoporosis patients during a follow-up period of 5 years within a randomized, placebo-controlled and double blinded clinical study (TOP study). Obtained results provide evidence on the PMA-zeolite positive effects on the bone strength of osteoporotic patients as the risk of fractures was significantly decreased in PMA-zeolite-treated patients with respect to time before entering the study (p = 0.002). Statistical evidence point also to positive bone changes in the 5-years TOP study course as evidenced through osteocalcin and beta-cross laps values showing a prevalence of the bone-formation process (p &lt; 0.05). BMD values were not significantly affected after the 5-years follow-up in PMA-zeolite-treated patients in comparison with the Placebo group. Results support the initial expectations based on our previously published preclinical studies on clinoptilolite product PMA-zeolite in animals that could be a new therapeutic option in osteoporosis patients.

Role of Traditional Chinese Medicine in Bone Regeneration and Osteoporosis

According to World Health Organization (WHO), osteoporosis is a systematic bone disability marked by reduced bone mass and microarchitectural degeneration of osseous cells, which leads to increased bones feebleness and fractures vulnerability. It is a polygenetic, physiological bone deformity that frequently leads to osteoporotic fractures and raises the risk of fractures in minimal trauma. Additionally, the molecular changes that cause osteoporosis are linked to decreased fracture repair and delayed bone regeneration. Bones have the ability to regenerate as part of the healing mechanism after an accident or trauma, including musculoskeletal growth and ongoing remodeling throughout adulthood. The principal treatment approaches for bone loss illnesses, such as osteoporosis, are hormone replacement therapy (HRT) and bisphosphonates. In this review, we searched literature regarding the Traditional Chinese medicines (TCM) in osteoporosis and bone regeneration. The literature results are summarized in this review for osteoporosis and bone regeneration. Traditional Chinese medicines (TCM) have grown in popularity as a result of its success in curing ailments while causing minimal adverse effects. Natural Chinese medicine has already been utilized to cure various types of orthopedic illnesses, notably osteoporosis, bone fractures and rheumatism with great success. TCM is a discipline of conventional remedy that encompasses herbal medication, massage (tui na), acupuncture, food, and exercise (qigong) therapy. It is based on more than 2,500 years of Chinese healthcare profession. This article serves as a comprehensive review summarizing the osteoporosis, bone regeneration and the traditional Chinese medicines used since ancient times for the management of osteoporosis and bone regeneration.

Engineering Multifunctional Hydrogel With Osteogenic Capacity for Critical-Size Segmental Bone Defect Repair

Treating critical-size segmental bone defects is an arduous challenge in clinical work. Preparation of bone graft substitutes with notable osteoinductive properties is a feasible strategy for critical-size bone defects. Herein, a biocompatible hydrogel was designed by dynamic supramolecular assembly of polyvinyl alcohol (PVA), sodium tetraborate (Na2B4O7), and tetraethyl orthosilicate (TEOS). The characteristics of the supramolecular hydrogel were evaluated by rheological analysis, swelling ratio, degradation experiments, and scanning electron microscopy (SEM). In in vitro experiments, this TEOS-hydrogel had self-healing property, low swelling rate, degradability, good biocompatibility, and induced osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) by upregulating the expression of Runx-2, Col-1, OCN, and osteopontin (OPN). In segmental bone defect rabbit models, the TEOS-containing hydrogel accelerated bone regeneration, thus restoring the continuity of bone and recanalization of the medullary cavity. The abovementioned results demonstrated that this TEOS-hydrogel has the potential to realize bone healing in critical-size segmental bone defects.

Inhibition of Cdk5 increases osteoblast differentiation and bone mass and improves fracture healing

Identification of regulators of osteoblastogenesis that can be pharmacologically targeted is a major goal in combating osteoporosis, a common disease of the elderly population. Here, unbiased kinome RNAi screening in primary murine osteoblasts identified cyclin-dependent kinase 5 (Cdk5) as a suppressor of osteoblast differentiation in both murine and human preosteoblastic cells. Cdk5 knockdown by siRNA, genetic deletion using the Cre-loxP system, or inhibition with the small molecule roscovitine enhanced osteoblastogenesis in vitro. Roscovitine treatment significantly enhanced bone mass by increasing osteoblastogenesis and improved fracture healing in mice. Mechanistically, downregulation of Cdk5 expression increased Erk phosphorylation, resulting in enhanced osteoblast-specific gene expression. Notably, simultaneous Cdk5 and Erk depletion abrogated the osteoblastogenesis conferred by Cdk5 depletion alone, suggesting that Cdk5 regulates osteoblast differentiation through MAPK pathway modulation. We conclude that Cdk5 is a potential therapeutic target to treat osteoporosis and improve fracture healing.

A new Cu(II)-containing coordination polymer: protective effect and mechanism exploration on elderly osteoporotic hip fractures via regulating the wnt signaling pathway

Elderly osteoporosis hip fracture has drawn the attention of the researcher. The coordination polymer was now widely used in clinic because their multiple structures and biological activities. In this present research, the new coordination polymer was designed and synthesized and their application values on elderly osteoporosis hip were evaluated. The reaction between Cu(II) salt and 4,4'-(1H-1,2,4-triazol-1-yl)methylene-bis(benzoic acid) (H2tzmb), an aromatase inhibitor letrozole derivative with the aid of the organic linker 4,4-bipyridine (4,4'-bpy) affords a new coordination polymer based on Cu(II) ions as nodes of {[Cu2(tzmb)2(4,4'-bpy) (μ2-H2O)2(DMA) (H2O)2]·10DMA}n (1). The complex 1 gained is totally investigated with the powder X-ray diffraction study, thermogravimetric analyses, the diffraction of single-crystal X-ray, elemental analysis as well as the Fourier transform infrared spectrometer spectra. The osteogenic differentiation of mesenchymal stem cell was measured with the western blotting assay through determining the Runx2 expression. The wnt signaling pathway relative expression in mesenchymal stem cell was detected through the determination of real-time RT-PCR. The cytotoxicity of the compound on the mesenchymal stem cell was determined with CCK-8 assay. The result of single-crystal X-ray diffraction reflects that the complex 1 has crystallized in space group R-3c of trigonal system and exhibits a three-dimensional skeleton architecture on the bases of the SBUs {Cu(tzmb)(μ2-H2O)}n. The western blotting assay results revealed that this compound could significantly promote the osteogenic differentiation of mesenchymal stem cell. Besides, the activation of wnt signaling pathway in mesenchymal stem cell was also increased by the compound exposure. Finally, it can be summed up that this compound has excellent application values on the elderly osteoporotic hip fractures treatment by increasing the activation of wnt signaling pathway in mesenchymal stem cell. The results of the CCK-8 assay indicated that the compound has no cytotoxicity on the mesenchymal stem cell. The molecular docking simulation results have identified that only the carboxyl group on the Cu complex exhibits the activity for the hydrogen bond formation, however, the pyridine ring does not have such activity, instead, the pyridine ring only acts as the ligand that binds to the Cu ion. This Cu(II) coordination polymer has excellent application values on the elderly osteoporotic hip fractures treatment by increasing the activation of wnt signaling pathway in mesenchymal stem cell.

Effect of osteoporosis-related reduction in the mechanical properties of bone on the acetabular fracture during a sideways fall: A parametric finite element approach

Purpose

The incidence of acetabular fractures due to low-energy falls is increasing among the geriatric population. Studies have shown that several biomechanical factors such as body configuration, impact velocity, and trochanteric soft-tissue thickness contribute to the severity and type of acetabular fracture. The effect of reduction in apparent density and elastic modulus of bone as well as other bone mechanical properties due to osteoporosis on low-energy acetabular fractures has not been investigated.

Methods

The current comprehensive finite element study aimed to study the effect of reduction in bone mechanical properties (trabecular, cortical, and trabecular + cortical) on the risk and type of acetabular fracture. Also, the effect of reduction in the mechanical properties of bone on the load-transferring mechanism within the pelvic girdle was examined.

Results

We observed that while the reduction in the mechanical properties of trabecular bone considerably affects the severity and area of trabecular bone failure, reduction in mechanical properties of cortical bone moderately influences both cortical and trabecular bone failure. The results also indicated that by reducing bone mechanical properties, the type of acetabular fracture turns from elementary to associated, which requires a more extensive intervention and rehabilitation period. Finally, we observed that the cortical bone plays a substantial role in load transfer, and by increasing reduction in the mechanical properties of cortical bone, a greater share of load is transmitted toward the pubic symphysis.

Conclusion

This study increases our understanding of the effect of osteoporosis progression on the incidence of low-energy acetabular fractures. The osteoporosis-related reduction in the mechanical properties of cortical bone appears to affect both the cortical and trabecular bones. Also, during the extreme reduction in the mechanical properties of bone, the acetabular fracture type will be more complicated. Finally, during the final stages of osteoporosis (high reduction in mechanical properties of bone) a smaller share of impact load is transferred by impact-side hemipelvis to the sacrum, therefore, an osteoporotic pelvis might mitigate the risk of sacral fracture.

Procalcitonin is expressed in osteoblasts and limits bone resorption through inhibition of macrophage migration during intermittent PTH treatment

Intermittent injections of parathyroid hormone (iPTH) are applied clinically to stimulate bone formation by osteoblasts, although continuous elevation of parathyroid hormone (PTH) primarily results in increased bone resorption. Here, we identified Calca, encoding the sepsis biomarker procalcitonin (ProCT), as a novel target gene of PTH in murine osteoblasts that inhibits osteoclast formation. During iPTH treatment, mice lacking ProCT develop increased bone resorption with excessive osteoclast formation in both the long bones and axial skeleton. Mechanistically, ProCT inhibits the expression of key mediators involved in the recruitment of macrophages, representing osteoclast precursors. Accordingly, ProCT arrests macrophage migration and causes inhibition of early but not late osteoclastogenesis. In conclusion, our results reveal a potential role of osteoblast-derived ProCT in the bone microenvironment that is required to limit bone resorption during iPTH.

Therapeutic Treatments for Osteoporosis-Which Combination of Pills Is the Best among the Bad?

Osteoporosis is a chronical, systemic skeletal disorder characterized by an increase in bone resorption, which leads to reduced bone density. The reduction in bone mineral density and therefore low bone mass results in an increased risk of fractures. Osteoporosis is caused by an imbalance in the normally strictly regulated bone homeostasis. This imbalance is caused by overactive bone-resorbing osteoclasts, while bone-synthesizing osteoblasts do not compensate for this. In this review, the mechanism is presented, underlined by in vitro and animal models to investigate this imbalance as well as the current status of clinical trials. Furthermore, new therapeutic strategies for osteoporosis are presented, such as anabolic treatments and catabolic treatments and treatments using biomaterials and biomolecules. Another focus is on new combination therapies with multiple drugs which are currently considered more beneficial for the treatment of osteoporosis than monotherapies. Taken together, this review starts with an overview and ends with the newest approaches for osteoporosis therapies and a future perspective not presented so far.

Bioactive coatings with anti-osteoclast therapeutic agents for bone implants: Enhanced compliance and prolonged implant life

The use of therapeutic agents that inhibit bone resorption is crucial to prolong implant life, delay revision surgery, and reduce the burden on the healthcare system. These therapeutic agents include bisphosphonates, various nucleic acids, statins, proteins, and protein complexes. Their use in systemic treatment has several drawbacks, such as side effects and insufficient efficacy in terms of concentration, which can be eliminated by local treatment. This review focuses on the incorporation of osteoclast inhibitors (antiresorptive agents) into bioactive coatings for bone implants. The ability of bioactive coatings as systems for local delivery of antiresorptive agents to achieve optimal loading of the bioactive coating and its release is described in detail. Various parameters such as the suitable concentrations, release times, and the effects of the antiresorptive agents on nearby cells or bone tissue are discussed. However, further research is needed to support the optimization of the implant, as this will enable subsequent personalized design of the coating in terms of the design and selection of the coating material, the choice of an antiresorptive agent and its amount in the coating. In addition, therapeutic agents that have not yet been incorporated into bioactive coatings but appear promising are also mentioned. From this work, it can be concluded that therapeutic agents contribute to the biocompatibility of the bioactive coating by enhancing its beneficial properties.

Dmp1 Lineage Cells Contribute Significantly to Periosteal Lamellar Bone Formation Induced by Mechanical Loading But Are Depleted from the Bone Surface During Rapid Bone Formation

Previous work has shown that osteoprogenitor cells (Prx1+) and pre‐osteoblasts (Osx+) contribute to mechanical loading‐induced bone formation. However, the role of mature Dmp1‐expressing osteoblasts has not been reported. In this study we assessed the contribution of osteoblast lineage cells to bone formation at an early time point following mechanical loading (day 8 from onset of loading). We labeled Osx‐expressing and Dmp1‐expressing cells in inducible Osx and Dmp1 reporter mice (iOsx‐Ai9, iDmp1‐Ai9), respectively, 3 weeks before loading. Mice were then loaded daily for 5 days (days 1–5) and were dosed with 5‐ethynyl‐2′‐deoxyuridine (EdU) in their drinking water until euthanasia on day 8. Mice were loaded to lamellar and woven bone inducing stimulation (−7 N/1400 με, −10 N/2000 με) to assess differences in these processes. We found varied responses in males and females to the loading stimuli, inducing modest lamellar (females, −7 N), moderate lamellar (males, −10 N), and robust woven (females, −10 N) bone. Overall, we found that preexisting (ie, lineage positive) Osx‐expressing and Dmp1‐expressing cells contribute largely to the bone formation response, especially during modest bone formation, while our results stuggest that other (non‐lineage–positive) cells support the sustained bone formation response during rapid bone formation. With moderate or robust levels of bone formation, a decrease in preexisting Osx‐expressing and Dmp1‐expressing cells at the bone surface occurred, with a near depletion of Dmp1‐expressing cells from the surface in female mice loaded to −10 N (from 52% to 11%). These cells appeared to be replaced by lineage‐negative cells from the periosteum. We also found a dose response in proliferation, with 17% to 18% of bone surface cells arising via proliferation in modest lamellar, 38% to 53% in moderate lamellar, and 59% to 81% in robust woven bone formation. In summary, our results show predominant contributions by preexisting Osx and Dmp1 lineage cells to loading‐induced lamellar bone formation, whereas recruitment of earlier osteoprogenitors and increased cell proliferation support robust woven bone formation. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Mechanisms, Diagnosis and Treatment of Bone Metastases

Bone and bone marrow are among the most frequent metastatic sites of cancer. The occurrence of bone metastasis is frequently associated with a dismal disease outcome. The prevention and therapy of bone metastases is a priority in the treatment of cancer patients. However, current therapeutic options for patients with bone metastatic disease are limited in efficacy and associated with increased morbidity. Therefore, most current therapies are mainly palliative in nature. A better understanding of the underlying molecular pathways of the bone metastatic process is warranted to develop novel, well-tolerated and more successful treatments for a significant improvement of patients' quality of life and disease outcome. In this review, we provide comparative mechanistic insights into the bone metastatic process of various solid tumors, including pediatric cancers. We also highlight current and innovative approaches to biologically targeted therapy and immunotherapy. In particular, we discuss the role of the bone marrow microenvironment in the attraction, homing, dormancy and outgrowth of metastatic tumor cells and the ensuing therapeutic implications. Multiple signaling pathways have been described to contribute to metastatic spread to the bone of specific cancer entities, with most knowledge derived from the study of breast and prostate cancer. However, it is likely that similar mechanisms are involved in different types of cancer, including multiple myeloma, primary bone sarcomas and neuroblastoma. The metastatic rate-limiting interaction of tumor cells with the various cellular and noncellular components of the bone-marrow niche provides attractive therapeutic targets, which are already partially exploited by novel promising immunotherapies.

Calycosin-7-O-β-Glucoside Isolated from Astragalus membranaceus Promotes Osteogenesis and Mineralization in Human Mesenchymal Stem Cells

Stem cells have received attention in various diseases, such as inflammatory, cancer, and bone diseases. Mesenchymal stem cells (MSCs) are multipotent stem cells that are critical for forming and repairing bone tissues. Herein, we isolated calycosin-7-O-β-glucoside (Caly) from the roots of Astragalus membranaceus, which is one of the most famous medicinal herbs, and investigated the osteogenic activities of Caly in MSCs. Caly did not affect cytotoxicity against MSCs, whereas Caly enhanced cell migration during the osteogenesis of MSCs. Caly increased the expression and enzymatic activities of ALP and the formation of mineralized nodules during the osteogenesis of MSCs. The osteogenesis and bone-forming activities of Caly are mediated by bone morphogenetic protein 2 (BMP2), phospho-Smad1/5/8, Wnt3a, phospho-GSK3β, and phospho-AKT, inducing the expression of runt-related transcription factor 2 (RUNX2). In addition, Caly-mediated osteogenesis and RUNX2 expression were attenuated by noggin and wortmannin. Moreover, the effects were validated in pre-osteoblasts committed to the osteoblast lineages from MSCs. Overall, our results provide novel evidence that Caly stimulates osteoblast lineage commitment of MSCs by triggering RUNX2 expression, suggesting Caly as a potential anabolic drug to prevent bone diseases.

Mice Lacking the Calcitonin Receptor Do Not Display Improved Bone Healing

Despite significant advances in surgical techniques, treatment options for impaired bone healing are still limited. Inadequate bone regeneration is not only associated with pain, prolonged immobilization and often multiple revision surgeries, but also with high socioeconomic costs, underlining the importance of a detailed understanding of the bone healing process. In this regard, we previously showed that mice lacking the calcitonin receptor (CTR) display increased bone formation mediated through the increased osteoclastic secretion of sphingosine-1-phosphate (S1P), an osteoanabolic molecule promoting osteoblast function. Although strong evidence is now available for the crucial role of osteoclast-to-osteoblast coupling in normal bone hemostasis, the relevance of this paracrine crosstalk during bone regeneration is unknown. Therefore, our study was designed to test whether increased osteoclast-to-osteoblast coupling, as observed in CTR-deficient mice, may positively affect bone repair. In a standardized femoral osteotomy model, global CTR-deficient mice displayed no alteration in radiologic callus parameters. Likewise, static histomorphometry demonstrated moderate impairment of callus microstructure and normal osseous bridging of osteotomy ends. In conclusion, bone regeneration is not accelerated in CTR-deficient mice, and contrary to its osteoanabolic action in normal bone turnover, osteoclast-to-osteoblast coupling specifically involving the CTR-S1P axis, may only be of minor relevance during bone healing.

Risks vs. benefits of switching therapy in patients with postmenopausal osteoporosis

Introduction: Osteoporosis is characterized by the fragility of bones, leading to fractures and, consequently, the deterioration of functional capacity and quality of life. Postmenopausal women, in particular, are prone to osteoporosis and often require anti-osteoporosis treatment. In the last few decades, various anti-osteoporosis drugs have been approved for clinical use. In an aging society, osteoporosis cannot be treated using a single agent; therefore, switching therapy is an important treatment strategy.Areas covered: This review covers switching therapy in patients with postmenopausal osteoporosis. It's extremely important to understand the characteristics of each drug including; limitations on the duration of use, side effects due to long-term use (such as atypical femur fracture and osteonecrosis of the jaw) or discontinuation (such as rebound phenomenon), compliance, and ability to prevent fractures. We review and summarize the risks and benefits of switching therapy.Expert opinion: When switching therapy, the order of drug administration is important. Routine monitoring should be continued after switching treatments. We recommend first using osteoanabolic agents in postmenopausal women with severe osteoporosis. In addition, identifying predictors of the efficacy and side effects of treatment may help prevent the inappropriate use of drugs for the treatment of osteoporosis.

Extracorporeal Shock Wave Combined with Teriparatide-Loaded Hydrogel Injection Promotes Segmental Bone Defects Healing in Osteoporosis

BACKGROUND

Osteoporosis is a systemic bone disease characterized by decreased bone density and deterioration of bone microstructure, leading to an increased probability of fragility fractures. Once segmental bone defect occurs, it is easy to cause delayed union and nonunion.

METHODS

The aim of this study is to investigate the efficacy of extracorporeal shock wave (ESW) and teriparatide-loaded hydrogel (T-Gel) combined strategy on the cell activity and differentiation of osteoporosis derived bone marrow mesenchymal stem cells (OP-BMSCs) in vitro and bone regeneration in osteoporotic segmental bone defects in vivo.

RESULTS

In vitro, the strategy of combining ESW and T-Gel significantly enhanced OP-BMSCs proliferation, survival, migration, and osteogenic differentiation by up-regulating the alkaline phosphatase activity, mineralization, and expression of runt-related transcription factor-2, type I collagen, osteocalcin, and osteopontin. In the segmental bone defect models of osteoporotic rabbits, Micro-CT evaluation and histological observation demonstrated this ESW-combined with T-Gel injection significantly induced bone healing by enhancing the osteogenic activity of the local microenvironment in osteoporotic defects.

CONCLUSION

In conclusion, ESW-combined with T-Gel injection could regulate the poor osteogenic microenvironment in osteoporotic defects and show potential for enhancing fragility fractures healing.

Comparison of demineralized bone matrix and hydroxyapatite as carriers of Escherichia coli recombinant human BMP-2

Background

Autograft has been widely used in various orthopedic and dental surgery for its superior osteogenicity, osteoinductivity and osteoconductivity. But the available volume of the autograft is limited and the efficacy of it is highly affected by the condition of the patients. Therefore, growth factors such as Escherichia coli bone morphogenetic protein-2 (ErhBMP-2) has been widely used in some countries and regions with various carriers that could affect the effects of the growth factors. Demineralized bone matrix (DBM) has been widely used as a bone graft substitute and growth factor carrier, but its effect as a carrier of ErhBMP-2 was less investigated.

Materials and methods

Rat calvaria defect model was used in this study. We implanted ErhBMP-2 with DBM or hydroxyapatite (HA) as a carrier in 8 mm calvaria defect and compared their bone regeneration effect in 4th week and 8th week after implantation with micro-CT and histology. The data was analyzed with one-way ANOVA method with Bonferroni post-hoc analysis.

Result

The group with DBM as the carrier showed significantly higher bone volume and bone thickness than the groups with HA as the carrier in both weeks. And the histology sections showed less adipose tissue formed in the groups with DBM as the carrier.

Conclusion

DBM could be a better carrier for ErhBMP-2 than HA.