Skeletal remodeling in health and disease

In vivo dynamics of hard tissue-forming cell origins: Insights from Cre/loxP-based cell lineage tracing studies

Bone tissue provides structural support for our bodies, with the inner bone marrow (BM) acting as a hematopoietic organ. Within the BM tissue, two types of stem cells play crucial roles: mesenchymal stem cells (MSCs) (or skeletal stem cells) and hematopoietic stem cells (HSCs). These stem cells are intricately connected, where BM-MSCs give rise to bone-forming osteoblasts and serve as essential components in the BM microenvironment for sustaining HSCs. Despite the mid-20th century proposal of BM-MSCs, their in vivo identification remained elusive owing to a lack of tools for analyzing stemness, specifically self-renewal and multipotency. To address this challenge, Cre/loxP-based cell lineage tracing analyses are being employed. This technology facilitated the in vivo labeling of specific cells, enabling the tracking of their lineage, determining their stemness, and providing a deeper understanding of the in vivo dynamics governing stem cell populations responsible for maintaining hard tissues. This review delves into cell lineage tracing studies conducted using commonly employed genetically modified mice expressing Cre under the influence of LepR, Gli1, and Axin2 genes. These studies focus on research fields spanning long bones and oral/maxillofacial hard tissues, offering insights into the in vivo dynamics of stem cell populations crucial for hard tissue homeostasis.

Engineering biomimetic scaffolds for bone regeneration: Chitosan/alginate/polyvinyl alcohol-based double-network hydrogels with carbon nanomaterials

In this study, new types of hybrid double-network (DN) hydrogels composed of polyvinyl alcohol (PVA), chitosan (CH), and sodium alginate (SA) are introduced, with the hypothesis that this combination and incorporating multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) will enhance osteogenetic differentiation and the structural and mechanical properties of scaffolds for bone tissue engineering applications. Initially, the impact of varying mass ratios of the PVA/CH/SA mixture on mechanical properties, swelling ratio, and degradability was examined. Based on this investigation, a mass ratio of 4:6:6 was determined to be optimal. At this ratio, the hydrogel demonstrated a Young's modulus of 47.5 ± 5 kPa, a swelling ratio of 680 ± 6 % after 3 h, and a degradation rate of 46.5 ± 5 % after 40 days. In the next phase, following the determination of the optimal mass ratio, CNTs and GNPs were incorporated into the 4:6:6 composite resulting in a significant enhancement in the electrical conductivity and stiffness of the scaffolds. The introduction of CNTs led to a notable increase of 36 % in the viability of MG63 osteoblast cells. Additionally, the inhibition zone test revealed that GNPs and CNTs increased the diameter of the inhibition zone by 49.6 % and 52.6 %, respectively.

Associations of sleep behaviors and genetic risk with risk of incident osteoporosis: A prospective cohort study of 293,164 participants

BACKGROUND

Unhealthy sleep behaviors are associated with higher risks of osteoporosis (OP), while prospective evidence is limited. This study aimed to prospectively investigate this association, quantify the attributable burden of OP incidence reduction due to unhealthy sleep behaviors, and explore potential modifications by genetic risk factors.

METHODS

This longitudinal cohort study was conducted utilizing data from the UK Biobank, comprising 293,164 participants initially free of OP and with requisite sleep behaviors data at baseline. We followed the participants after recruitment until November 30, 2022, to ascertain incident OP. We assessed the associations of five sleep behaviors including sleep duration, chronotype, insomnia, daytime napping, and morning wake-up difficulties, as well as sleep behavior patterns identified based on the above sleep behaviors, with the risk of OP, using Cox models adjusted for multiple confounders. The analyses were then performed separately among individuals with different OP susceptibility, indexed by standard polygenetic risk scores(PRS) for OP. Our secondary outcome was OP with pathologic fracture. Subgroup and sensitivity analyses were performed. Additionally, attributable risk percent in the exposed population (AR%) and population attributable fraction (PAF) of sleep behaviors were calculated.

RESULTS

Over a median follow-up of 13.7 years, 8253 new-onset OP cases were documented. Unhealthy sleep behaviors, such as long or short sleep duration, insomnia, daytime napping, morning wake-up difficulties, and unhealthy sleep patterns, were associated with elevated risks of OP (HRs ranging from 1.14 to 1.46, all P-value <0.001) compared to healthy sleep behaviors. Similar associations were observed for OP with pathologic fractures. Insomnia exhibited the largest AR% of 39.98 % (95%CI: 36.46, 43.31) and PAF of 33.25 % (95%CI: 30.00, 36.34) among healthy sleep patterns and components. A statistically significant multiplicative interaction was noted between sleep behaviors and OP PRS on OP risk (all P-interaction <0.001).

CONCLUSIONS

Four unhealthy sleep behaviors and sleep behavior patterns were associated to increased OP risk, with insomnia contributing the most to OP incidence, while genetic risk for OP modified this association. These findings underscore the crucial role of adhering to healthy sleep behaviors for effective OP prevention.

An adaptive biodegradable zinc alloy with bidirectional regulation of bone homeostasis for treating fractures and aged bone defects

Healing of fractures or bone defects is significantly hindered by overactivated osteoclasts and inhibited osteogenesis in patients with abnormal bone metabolism. Current clinical approaches using titanium alloys or stainless steel provide mechanical support but have no biological effects on bone regeneration. Therefore, designing and fabricating degradable metal materials with sufficient mechanical strength and bidirectional regulation of both osteoblasts and osteoclasts is a substantial challenge. Here, this study first reported an adaptive biodegradable Zn-0.8 Mg alloy with bidirectional regulation of bone homeostasis, which promotes osteogenic differentiation by activating the Pi3k/Akt pathway and inhibits osteoclast differentiation by inhibiting the GRB2/ERK pathway. The anti-osteolytic ability of the Zn-0.8 Mg alloy was verified in a mouse calvarial osteolysis model and its suitability for internal fracture fixation with high-strength screws was confirmed in the rabbit femoral condyle fracture model. Furthermore, in an aged postmenopausal rat femoral condyle defect model, 3D printed Zn-0.8 Mg scaffolds promoted excellent bone regeneration through adaptive structures with good mechanical properties and bidirectionally regulated bone metabolism, enabling personalized bone defect repair. These findings demonstrate the substantial potential of the Zn-0.8 Mg alloy for treating fractures or bone defects in patients with aberrant bone metabolism.

Caspase-8 promotes scramblase-mediated phosphatidylserine exposure and fusion of osteoclast precursors

Efficient cellular fusion of mononuclear precursors is the prerequisite for the generation of fully functional multinucleated bone-resorbing osteoclasts. However, the exact molecular factors and mechanisms controlling osteoclast fusion remain incompletely understood. Here we identify RANKL-mediated activation of caspase-8 as early key event during osteoclast fusion. Single cell RNA sequencing-based analyses suggested that activation of parts of the apoptotic machinery accompanied the differentiation of osteoclast precursors into mature multinucleated osteoclasts. A subsequent characterization of osteoclast precursors confirmed that RANKL-mediated activation of caspase-8 promoted the non-apoptotic cleavage and activation of downstream effector caspases that translocated to the plasma membrane where they triggered activation of the phospholipid scramblase Xkr8. Xkr8-mediated exposure of phosphatidylserine, in turn, aided cellular fusion of osteoclast precursors and thereby allowed generation of functional multinucleated osteoclast syncytia and initiation of bone resorption. Pharmacological blockage or genetic deletion of caspase-8 accordingly interfered with fusion of osteoclasts and bone resorption resulting in increased bone mass in mice carrying a conditional deletion of caspase-8 in mononuclear osteoclast precursors. These data identify a novel pathway controlling osteoclast biology and bone turnover with the potential to serve as target for therapeutic intervention during diseases characterized by pathologic osteoclast-mediated bone loss. Proposed model of osteoclast fusion regulated by caspase-8 activation and PS exposure. RANK/RANK-L interaction. Activation of procaspase-8 into caspase-8. Caspase-8 activates caspase-3. Active capase-3 cleaves Xkr8. Local PS exposure is induced. Exposed PS is recognized by the fusion partner. FUSION. PS is re-internalized.

A comprehensive review on glucocorticoids induced osteoporosis: A medication caused disease

Glucocorticoids (GCs) are steroid hormones that are extensively used in the treatment of autoimmune diseases, inflammation, and cancer. The major ill effect of administering GCs is that it has a deleterious effect on bone, which leads to GC-induced osteoporosis. GC therapy induces bone loss and is associated with the risk of nonvertebral and vertebral fractures, as it works in combination by increasing bone reabsorption and suppressing bone formation during the initial phase of therapy. It is seen and established that GC in excess or in low dose for 3 months or more can be a risk factor for fracture, and the risk increases with an increase in dose and duration of usage. The most common cause of secondary osteoporosis is the administration of GC inside the body to treat various diseases. The degree of bone loss is directly proportional to the GC dose and the exposure duration. The first step is to evaluate the patients' risk factors for the development of glucocorticoids that induce osteoporosis, which include the dose, duration of use, patient age, sex, previous fractures, and other medical conditions.

Contribution of Osteoblast and Osteoclast Supernatants to Bone Formation: Determination Using a Novel Microfluidic Chip

We fabricated a microfluidic chip (osteoblast [OB]-osteoclast [OC] chip) that could regulate the mixture amounts of OB and OC supernatants to investigate the effect of different supernatant distributions on osteogenesis or osteoclastogenesis. Computer-aided design was used to produce an OB-OC chip from polydimethylsiloxane. A pressure controller was assembled and different blends of OB and OC supernatants were correctly determined. OB and OC supernatants were placed on the upper panels of the OB-OC chip after differentiation for an in vitro evaluation. We then tested the changes in osteogenesis using MC3T3-E1 cells in the middle chambers. We observed that a 75:25 distribution of OB and OC supernatants was the most potent in osteogenesis. We then primed the osteogenic differentiation of MC3T3-E1 cells using an OB-OC mixed supernatant or an OB supernatant alone (supernatant ratios of 75:25 or 100:0, respectively). These cells were placed on the calvarial defect sites of rats. Microcomputed tomography and histological analyses determined a significantly higher bone formation in the group exposed to the OB-OC supernatant at a ratio of 75:25. In this study, we demonstrate the applicability of an OB-OC chip to evaluate the effect of different supernatant distributions of OB and OC. We observed that the highest bone-forming potential was in MC3T3-E1 cells treated with conditioned media, specifically the OB-OC supernatant at a ratio of 75:25.

Pyroptosis: A spoiler of peaceful coexistence between cells in degenerative bone and joint diseases

BACKGROUND

As people age, degenerative bone and joint diseases (DBJDs) become more prevalent. When middle-aged and elderly people are diagnosed with one or more disorders such as osteoporosis (OP), osteoarthritis (OA), and intervertebral disc degeneration (IVDD), it often signals the onset of prolonged pain and reduced functionality. Chronic inflammation has been identified as the underlying cause of various degenerative diseases, including DBJDs. Recently, excessive activation of pyroptosis, a form of programed cell death (PCD) mediated by inflammasomes, has emerged as a primary driver of harmful chronic inflammation. Consequently, pyroptosis has become a potential target for preventing and treating DBJDs.

AIM OF REVIEW

This review explored the physiological and pathological roles of the pyroptosis pathway in bone and joint development and its relation to DBJDs. Meanwhile, it elaborated the molecular mechanisms of pyroptosis within individual cell types in the bone marrow and joints, as well as the interplay among different cell types in the context of DBJDs. Furthermore, this review presented the latest compelling evidence supporting the idea of regulating the pyroptosis pathway for DBJDs treatment, and discussed the potential, limitations, and challenges of various therapeutic strategies involving pyroptosis regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In summary, an interesting identity for the unregulated pyroptosis pathway in the context of DBJDs was proposed in this review, which was undertaken as a spoiler of peaceful coexistence between cells in a degenerative environment. Over the extended course of DBJDs, pyroptosis pathway perpetuated its activity through crosstalk among pyroptosis cascades in different cell types, thus exacerbating the inflammatory environment throughout the entire bone marrow and joint degeneration environment. Correspondingly, pyroptosis regulation therapy emerged as a promising option for clinical treatment of DBJDs.

Bone-organ axes: bidirectional crosstalk

In addition to its recognized role in providing structural support, bone plays a crucial role in maintaining the functionality and balance of various organs by secreting specific cytokines (also known as osteokines). This reciprocal influence extends to these organs modulating bone homeostasis and development, although this aspect has yet to be systematically reviewed. This review aims to elucidate this bidirectional crosstalk, with a particular focus on the role of osteokines. Additionally, it presents a unique compilation of evidence highlighting the critical function of extracellular vesicles (EVs) within bone-organ axes for the first time. Moreover, it explores the implications of this crosstalk for designing and implementing bone-on-chips and assembloids, underscoring the importance of comprehending these interactions for advancing physiologically relevant in vitro models. Consequently, this review establishes a robust theoretical foundation for preventing, diagnosing, and treating diseases related to the bone-organ axis from the perspective of cytokines, EVs, hormones, and metabolites.

Genistein supplementation has no effects on vitamin D levels in healthy Spanish postmenopausal women

Background: In vitro studies have shown that genistein inhibits the CYP240 enzyme, which is involved in the degradation of 1,25-dihydroxycholecalciferol and its precursor 25-hydroxycholecalciferol, and increases their plasma levels. However, no clinical studies have primarily assessed the synergistic effect of isoflavones on vitamin D levels. The aim of this study was to evaluate the possible additive effect of genistein supplementation on vitamin D levels, calcium metabolism and bone remodeling markers in healthy postmenopausal women during the spring-summer months. Patients and methods: We made a prospective, double-blind study with 150 healthy postmenopausal women that were randomized to three groups. One received placebo, another received calcium (1000 mg/day) and vitamin D (cholecalciferol, 800 U/day) and the third received calcium (1000 mg/day), vitamin D (cholecalciferol, 800 U/day) and genistein (90 mg/day). The study period was from May to September (spring-summer). Vitamin D, PTH, CTX and P1NP were determined by electrochemiluminescence at baseline and after 12 weeks. Results: Vitamin D levels increased in all groups: placebo (23±9 ng/ml vs. 29±10 ng/ml, p<0.05), calcium+vitamin D (26±10 ng/ml vs. 33±8 ng/ml, p<0.05) and calcium+vitamin D+genistein (24±9 ng/ml vs. 31±8 ng/l, p<0.05) without between-group differences. At study end, the percentage of women with vitamin D <20 ng/ml (11%) and <30 ng/ml (39%) had fallen without between-group differences. The effects on calcium metabolism and bone remodeling markers were similar between groups: rises in vitamin D were significantly linked to reductions in PTH, CTX and P1NP. Conclusion: Adding genistein to supplementation with calcium and vitamin D provided not additional changes in vitamin D levels, calcium metabolism or bone remodeling markers in healthy Spanish postmenopausal women during the spring-summer months.

Isobavachin attenuates osteoclastogenesis and periodontitis-induced bone loss by inhibiting cellular iron accumulation and mitochondrial biogenesis

As bone-resorbing cells rich in mitochondria, osteoclasts require high iron uptake to promote mitochondrial biogenesis and maintain a high-energy metabolic state for active bone resorption. Given that abnormal osteoclast formation and activation leads to imbalanced bone remodeling and osteolytic bone loss, osteoclasts may be crucial targets for treating osteolytic diseases such as periodontitis. Isobavachin (IBA), a natural flavonoid compound, has been confirmed to be an inhibitor of receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast differentiation from bone marrow-derived macrophages (BMMs). However, its effects on periodontitis-induced bone loss and the potential mechanism of its anti-osteoclastogenesis effect remain unclear. Our study demonstrated that IBA suppressed RANKL-induced osteoclastogenesis in BMMs and RAW264.7 cells and inhibited osteoclast-mediated bone resorption in vitro. Transcriptomic analysis indicated that iron homeostasis and reactive oxygen species (ROS) metabolic process were enriched among the differentially expressed genes following IBA treatment. IBA exerted its anti-osteoclastogenesis effect by inhibiting iron accumulation in osteoclasts. Mechanistically, IBA attenuated iron accumulation in RANKL-induced osteoclasts by inhibiting the mitogen-activated protein kinase (MAPK) pathway to upregulate ferroportin1 (Fpn1) expression and promote Fpn1-mediated intracellular iron efflux. We also found that IBA inhibited mitochondrial biogenesis and function, and reduced RANKL-induced ROS generation in osteoclasts. Furthermore, IBA attenuated periodontitis-induced bone loss by reducing osteoclastogenesis in vivo. Overall, these results suggest that IBA may serve as a promising therapeutic strategy for bone diseases characterized by osteoclastic bone resorption.

Nanoparticulate bioceramic putty suppresses osteoclastogenesis and inflammatory bone loss in mice via inhibition of TRAF6-mediated signalling pathways: A laboratory investigation

AIM

This study aimed to determine the effects of iRoot BP Plus on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis in vitro and inflammation-mediated bone resorption in vivo and investigated the underlying molecular mechanisms.

METHODOLOGY

CCK-8 was performed to test cell viability in RANKL-induced RAW 264.7 cells and BMDMs in response to iRoot BP Plus. The effect of iRoot BP Plus on osteoclastogenesis was determined using TRAP staining and phalloidin staining, respectively. Pit formation assay was conducted to measure osteoclast resorptive capacity. Western blot and qPCR were performed to examine osteoclast-related proteins and gene expression, respectively. Western blot was also used to investigate the signalling pathways involved. For in vivo experiments, an LPS-induced mouse calvarial bone resorption model was established to analyse the effect of iRoot BP Plus on bone resorption (n = 6 per group). At 7 days, mouse calvaria were collected and prepared for histological analysis.

RESULTS

We identified that iRoot BP Plus extracts significantly attenuated RANKL-induced osteoclastogenesis, reduced sealing zone formation, restrained osteolytic capacity and decreased osteoclast-specific gene expression (p < .01). Mechanistically, iRoot BP Plus extracts reduced TRAF6 via proteasomal degradation, then suppressed the phosphorylation of mitogen-activated protein kinases (MAPKs), blocked the nuclear translocation of c-Fos and diminished nuclear factor-κB (NF-κB) p65 and NFATc1 accumulation. Consistent with the in vitro results, iRoot BP Plus extracts attenuated osteoclast activity thus protecting against inflammatory bone resorption in vivo (p < .05), which was accompanied by a suppression of TRAF6, c-Fos, NFATc1 and cathepsin K expression.

CONCLUSION

These findings provide valuable insights into the signalling mechanisms underlying nanoparticulate bioceramic putty-mediated bone homeostasis.

RUFY4 deletion prevents pathological bone loss by blocking endo-lysosomal trafficking of osteoclasts

Mature osteoclasts degrade bone matrix by exocytosis of active proteases from secretory lysosomes through a ruffled border. However, the molecular mechanisms underlying lysosomal trafficking and secretion in osteoclasts remain largely unknown. Here, we show with GeneChip analysis that RUN and FYVE domain-containing protein 4 (RUFY4) is strongly upregulated during osteoclastogenesis. Mice lacking Rufy4 exhibited a high trabecular bone mass phenotype with abnormalities in osteoclast function in vivo. Furthermore, deleting Rufy4 did not affect osteoclast differentiation, but inhibited bone-resorbing activity due to disruption in the acidic maturation of secondary lysosomes, their trafficking to the membrane, and their secretion of cathepsin K into the extracellular space. Mechanistically, RUFY4 promotes late endosome-lysosome fusion by acting as an adaptor protein between Rab7 on late endosomes and LAMP2 on primary lysosomes. Consequently, Rufy4-deficient mice were highly protected from lipopolysaccharide- and ovariectomy-induced bone loss. Thus, RUFY4 plays as a new regulator in osteoclast activity by mediating endo-lysosomal trafficking and have a potential to be specific target for therapies against bone-loss diseases such as osteoporosis.

An integrated multi-omics analysis reveals osteokines involved in global regulation

Bone secretory proteins, termed osteokines, regulate bone metabolism and whole-body homeostasis. However, fundamental questions as to what the bona fide osteokines and their cellular sources are and how they are regulated remain unclear. In this study, we analyzed bone and extraskeletal tissues, osteoblast (OB) conditioned media, bone marrow supernatant (BMS), and serum, for basal osteokines and those responsive to aging and mechanical loading/unloading. We identified 375 candidate osteokines and their changes in response to aging and mechanical dynamics by integrating data from RNA-seq, scRNA-seq, and proteomic approaches. Furthermore, we analyzed their cellular sources in the bone and inter-organ communication facilitated by them (bone-brain, liver, and aorta). Notably, we discovered that senescent OBs secrete fatty-acid-binding protein 3 to propagate senescence toward vascular smooth muscle cells (VSMCs). Taken together, we identified previously unknown candidate osteokines and established a dynamic regulatory network among them, thus providing valuable resources to further investigate their systemic roles.

Understanding osteokine biology

Bone is an endocrine organ that participates in whole-body homeostasis. The biology of bone-derived osteokines, however, remains unclear. Liang et al. integrate experimental and computational methods to discover new osteokines, establish their cell of origin and target site, and study their role in aging and during mechanical stress.

A homozygous SP7/OSX mutation causes osteogenesis and dentinogenesis imperfecta with craniofacial anomalies

Osteogenesis imperfecta (OI) is a heterogeneous spectrum of hereditary genetic disorders that cause bone fragility, through various quantitative and qualitative defects of type 1 collagen, a triple helix composed of two α1 and one α2 chains encoded by COL1A1 and COL1A2, respectively. The main extra-skeletal manifestations of OI include blue sclerae, opalescent teeth, and hearing impairment. Moreover, multiple genes involved in osteoblast maturation and type 1 collagen biosynthesis are now known to cause recessive forms of OI. In this study a multiplex consanguineous family of two affected males with OI was recruited for genetic screening. To determine the causative, pathogenic variant(s), genomic DNA from two affected family members were analyzed using whole exome sequencing, autozygosity mapping, and then validated with Sanger sequencing. The analysis led to the mapping of a homozygous variant previously reported in SP7/OSX, a gene encoding for Osterix, a transcription factor that activates a repertoire of genes involved in osteoblast and osteocyte differentiation and function. The identified variant (c.946C > T; p.Arg316Cys) in exon 2 of SP7/OSX results in a pathogenic amino acid change in two affected male siblings and develops OI, dentinogenesis imperfecta, and craniofacial anomaly. On the basis of the findings of the present study, SP7/OSX:c. 946C > T is a rare homozygous variant causing OI with extra-skeletal features in inbred Arab populations.

Subnormal Serum Liver Enzyme Levels: A Review of Pathophysiology and Clinical Significance

Subnormal levels of liver enzymes, below the lower limit of normal on local laboratory reports, can be useful diagnostically. For instance, subnormal levels of aminotransferases can be observed in vitamin B6 deficiency and chronic kidney disease. Subnormal alkaline phosphatase levels may indicate the presence of hypophosphatasia, Wilson's disease, deficiencies of divalent ions, or malnutrition. Subnormal levels of gamma glutamyl transferase may be seen in cases of acute intrahepatic cholestasis, the use of certain medications, and in bone disease. Finally, subnormal levels of 5'-nucleotidase have been reported in lead poisoning and nonspherocytic hemolytic anemia. The aim of this review is to bring attention to the fact that subnormal levels of these enzymes should not be ignored as they may indicate pathological conditions and provide a means of early diagnosis.

Long-term second-generation antipsychotics decreases bone formation and resorption in male patients with schizophrenia

RATIONALE

Patients with schizophrenia with second-generation antipsychotics (SGAs) treatment have shown an increased risk of bone fragility and susceptibility to fracture; however, it is still unclear whether this risk is derived from the effect of antipsychotics on balance of bone metabolism.

OBJECTIVES

We investigated the changes of two bone turnover biomarkers (BTMs) concentrations in people with schizophrenia receiving SGAs: procollagen type I aminoterminal propeptide (PINP) and C-terminal telopeptide of type I collagen (CTX-1) as BTMs of osteogenesis and bone resorption, respectively, to explore how antipsychotics contribute to bone fragility.

METHODS

We recruited 59 Chinese male patients with schizophrenia (32 drug-naïve first-episode (DNFE) patients and 27 chronic patients) to undergo 8 weeks SGAs treatment. Fasting peripheral blood samples of pre- and posttreatment were collected, plasma levels of PINP and CTX-1 were measured.

RESULTS

The interaction effects of group and time on PINP and CTX-1 concentrations were found (P = .016 and P = .008). There was a significant decrease for both BTMs concentrations of the posttreatment compared to the pretreatment (P<.001 and P = .003). Chronic patients had significantly higher changes of BTMs concentrations compared to DNFE patients (P = .048 and P = .024). There was a positive correlation of the two BTMs of pretreatment with disease course in DNFE group (r = .37, P = .039;r = .38, P = .035) and a negative correlation of PINP of pretreatment with age in the chronic group (r=-.40, P = .039).

CONCLUSION

Long-term SGAs medication inhibited osteogenesis in a dose- and time-dependent manner and damaged the balance of bone formation and bone resorption.

Reduced osseointegration in disuse and denervation rat models results from impaired cellular responses to multiscale microstructured titanium surfaces

Immobilization-induced skeletal unloading results in muscle atrophy and rapid bone loss, thereby increasing the risk of falling and the need for implant therapy in patients with extended bed rest or neuromuscular injuries. Skeletal unloading causes bone loss by altering bone growth and resorption, suggesting that implant performance might be affected. To test this, we focused on early events in implant osseointegration. We used the rat sciatic neurectomy-induced disuse model under two different settings. In Study 1, 16 Sprague Dawley rats (SD) were separated into control, sham operated+cast immobilization, and sciatic neurectomy+casting groups; titanium implants with multiscale microtextured topography and hydrophilic chemistry (modSLA) were inserted in the distal femoral metaphysis. Neurectomy surgeries and casting were performed at the same surgical setting as implant placement; rats were euthanized 4 weeks post-implantation. In Study 2, we established the unloaded condition before implantation. A total of 12 SD rats were divided into control and sciatic+femoral neurectomy groups. A total of 24 days after sciatic and femoral neurectomy surgery, rats received implants. Study 2 rats were euthanized at 4 weeks post-implantation. MicroCT and histomorphometry showed that trabecular bone and osseointegration were reduced when disuse was established before implantation. Osteoblasts isolated from Study 1 sciatic neurectomy tibial bones exhibited impaired differentiation on modSLA culture disks, revealing a possible mechanism responsible for the decreased osseointegration observed in the Study 2 rats. This study addressed the importance of considering the mechanical unloading and muscle function history before implant insertion and suggests that implant performance was reduced due to poor cellular ability to regenerate.

Bidirectional mediation of bone mineral density and brain atrophy on their associations with gait variability

This mediation analysis aimed to investigate the associations among areal bone mineral density, mobility-related brain atrophy, and specific gait patterns. A total of 595 participants from the Taizhou Imaging Study, who underwent both gait and bone mineral density measurements, were included in this cross-sectional analysis. We used a wearable gait tracking device to collect quantitative gait parameters and then summarized them into independent gait domains with factor analysis. Bone mineral density was measured in the lumbar spine, femoral neck, and total hip using dual-energy X-ray absorptiometry. Magnetic resonance images were obtained on a 3.0-Tesla scanner, and the volumes of brain regions related to mobility were computed using FreeSurfer. Lower bone mineral density was found to be associated with higher gait variability, especially at the site of the lumbar spine (β = 0.174, FDR = 0.001). Besides, higher gait variability was correlated with mobility-related brain atrophy, like the primary motor cortex (β = 0.147, FDR = 0.006), sensorimotor cortex (β = 0.153, FDR = 0.006), and entorhinal cortex (β = 0.106, FDR = 0.043). Bidirectional mediation analysis revealed that regional brain atrophy contributed to higher gait variability through the low lumbar spine bone mineral density (for the primary motor cortex, P = 0.018; for the sensorimotor cortex, P = 0.010) and the low lumbar spine bone mineral density contributed to higher gait variability through the primary motor and sensorimotor cortices (P = 0.026 and 0.010, respectively).

Altered Osteoblast Metabolism with Aging Results in Lipid Accumulation and Oxidative Stress Mediated Bone Loss

Cellular aging is associated with dysfunction of numerous tissues affecting multiple organ systems. A striking example of this is related to age-related bone loss, or osteoporosis, increasing fracture incidence. Interestingly, the two compartments of bone, cortical and cancellous or trabecular, rely on different mechanisms for development and maintenance during 'normal' aging. At a cellular level, the aging process disturbs a multitude of intracellular pathways. In particular, alterations in cellular metabolic functions thereby impacting cellular bioenergetics have been implicated in multiple tissues. Therefore, this study aimed to characterize how metabolic processes were altered in bone forming osteoblasts in aged mice compared to young mice. Metabolic flux analyses demonstrated both stromal cells and mature, matrix secreting osteoblasts from aged mice exhibited mitochondrial dysfunction. This was also accompanied by a lack of adaptability or metabolic flexibility to utilize exogenous substrates compared to osteoblasts cultured from young mice. Additionally, lipid droplets accumulated in both early stromal cells and mature osteoblasts from aged mice, which was further depicted as increased lipid content within the bone cortex of aged mice. Global transcriptomic analysis of the bone further supported these metabolic data as enhanced oxidative stress genes were up-regulated in aged mice, while osteoblast-related genes were down-regulated when compared to the young mice. Collectively, these data suggest that aging results in altered osteoblast metabolic handling of both exogenous and endogenous substrates which could contribute to age-related osteoporosis.

DDIT3/CHOP promotes LPS/ATP-induced pyroptosis in osteoblasts via mitophagy inhibition

Inflammatory environments can trigger endoplasmic reticulum (ER) stress and lead to pyroptosis in various tissues and cells, including liver, brain, and immune cells. As a key factor of ER stress, DNA damage-inducible transcript 3 (DDIT3)/CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) is upregulated in osteoblasts during inflammatory stimulation. DDIT3/CHOP may therefore regulate osteoblast pyroptosis in inflammatory conditions. During this investigation, we found that lipopolysaccharides (LPS)/adenosine 5'-triphosphate (ATP) stimulation in vitro induced osteoblasts to undergo pyroptosis, and the expression of DDIT3/CHOP was increased during this process. The overexpression of DDIT3/CHOP further promoted osteoblast pyroptosis as evidenced by the increased expression of the inflammasome NLR family pyrin domain containing 3 (NLRP3) and ratios of caspase-1 p20/caspase-1 and cleaved gasdermin D (GSDMD)/GSDMD. To explore the specific mechanism of this effect, we found through fluorescence imaging and Western blot analysis that LPS/ATP stimulation promoted PTEN-induced kinase 1 (PINK1)/E3 ubiquitin-protein ligase parkin (Parkin)-mediated mitophagy in osteoblasts, and this alteration was suppressed by the DDIT3/CHOP overexpression, resulting in increased ratio of pyroptosis compared with the control groups. The impact of DDIT3/CHOP on pyroptosis in osteoblasts was reversed by the application of carbonyl cyanide 3-chlorophenylhydrazone (CCCP), a specific mitophagy agonist. Therefore, our data demonstrated that DDIT3/CHOP promotes osteoblast pyroptosis by inhibiting PINK1/Parkin-mediated mitophagy in an inflammatory environment.

Protective Effects of the Postbiotic Lactobacillus plantarum MD35 on Bone Loss in an Ovariectomized Mice Model

Postmenopausal osteoporosis is caused by estrogen deficiency, which impairs bone homeostasis, resulting in increased osteoclastic resorption without a corresponding increase in osteoblastic activity. Postbiotics have several therapeutic properties, including anti-obesity, anti-diabetic, anti-inflammatory, and anti-osteoporotic effects. However, the beneficial effects of the postbiotic MD35 of Lactobacillus plantarum on bone have not been studied. In this study, we demonstrated that the postbiotic L. plantarum MD35, isolated from young radish water kimchi, influences osteoclast differentiation in mouse bone marrow-derived macrophage (BMM) culture. In addition, it was effective protecting against estrogen deficiency-induced bone loss in ovariectomized (OVX) mice, an animal model of postmenopausal osteoporosis. In BMM cells, postbiotic MD35 inhibited the receptor activator of nuclear factor-kappa B of NF-κB ligand (RANKL)-induced osteoclast differentiation by attenuating the phosphorylation of extracellular signal-related kinase, significantly suppressing the resorption activity and down-regulating the expression of RANKL-mediated osteoclast-related genes. In the animal model, the oral administration of postbiotic MD35 remarkably improved OVX-induced trabecular bone loss and alleviated the destruction of femoral plate growth. Therefore, postbiotic MD35 could be a potential therapeutic candidate for postmenopausal osteoporosis by suppressing osteoclastogenesis through the regulation of osteoclast-related molecular mechanisms.

Association between cognitive function and body composition in older adults: data from NHANES (1999-2002)

Aim

To investigate the association between cognitive function and body composition in older adults.

Methods

We collected data on 2080 older adults (>60 years of age) from the National Health and Nutrition Examination Survey (NHANES) for the years 1999-2000 and 2001-2002. Candidate variables included: demographic data (sex, age, race, education level, marital status, poverty-to-income ratio), alcohol consumption, cardiovascular disease, diabetes, osteoporosis, total bone mineral density, and total fat mass. A logistic regression model was established to analyze the association between cognitive function and body composition in older adults. In addition, stratified logics regression analysis was performed by sex and age.

Results

Bone mineral density significantly affects cognitive function in older adults (p<0.01). When examining the data according to sex, this correlation is present for women (p < 0.01). For men, though, it is not significant (p = 0.081). Stratified by age, total bone mineral density was significantly correlated with cognitive function in 60-70 and 70-80 years old people, but not in older adults older than 80 years(for 60-70 years old, p = 0.019; for 70-80 years old, p = 0.022). There was no significant correlation between total bone mineral density and cognitive function (p = 0.575).

Conclusion

The decrease of total bone mineral density was significantly correlated with cognitive decline in the older adults, especially among women and older people in the 60 to 80 age group. There was no connection between total fat mass, total percent fat, total lean mass, appendicular lean mass, appendicular lean mass /BMI and cognitive function in the older adults.

Bridging the Gap in Understanding Bone Metastasis: A Multifaceted Perspective

The treatment of patients with advanced cancer poses clinical problems due to the complications that arise as the disease progresses. Bone metastases are a common problem that cancer patients may face, and currently, there are no effective drugs to treat these individuals. Prostate, breast, and lung cancers often spread to the bone, causing significant and disabling health conditions. The bone is a highly active and dynamic tissue and is considered a favorable environment for the growth of cancer. The role of osteoblasts and osteoclasts in the process of bone remodeling and the way in which their interactions change during the progression of metastasis is critical to understanding the pathophysiology of this disease. These interactions create a self-perpetuating loop that stimulates the growth of metastatic cells in the bone. The metabolic reprogramming of both cancer cells and cells in the bone microenvironment has serious implications for the development and progression of metastasis. Insight into the process of bone remodeling and the systemic elements that regulate this process, as well as the cellular changes that occur during the progression of bone metastases, is critical to the discovery of a cure for this disease. It is crucial to explore different therapeutic options that focus specifically on malignancy in the bone microenvironment in order to effectively treat this disease. This review will focus on the bone remodeling process and the effects of metabolic disorders as well as systemic factors like hormones and cytokines on the development of bone metastases. We will also examine the various therapeutic alternatives available today and the upcoming advances in novel treatments.

Piezo1 expression in chondrocytes controls endochondral ossification and osteoarthritis development

Piezo proteins are mechanically activated ion channels, which are required for mechanosensing functions in a variety of cell types. While we and others have previously demonstrated that the expression of Piezo1 in osteoblast lineage cells is essential for bone-anabolic processes, there was only suggestive evidence indicating a role of Piezo1 and/or Piezo2 in cartilage. Here we addressed the question if and how chondrocyte expression of the mechanosensitive proteins Piezo1 or Piezo2 controls physiological endochondral ossification and pathological osteoarthritis (OA) development. Mice with chondrocyte-specific inactivation of Piezo1 (Piezo1Col2a1Cre), but not of Piezo2, developed a near absence of trabecular bone below the chondrogenic growth plate postnatally. Moreover, all Piezo1Col2a1Cre animals displayed multiple fractures of rib bones at 7 days of age, which were located close to the growth plates. While skeletal growth was only mildly affected in these mice, OA pathologies were markedly less pronounced compared to littermate controls at 60 weeks of age. Likewise, when OA was induced by anterior cruciate ligament transection, only the chondrocyte inactivation of Piezo1, not of Piezo2, resulted in attenuated articular cartilage degeneration. Importantly, osteophyte formation and maturation were also reduced in Piezo1Col2a1Cre mice. We further observed increased Piezo1 protein abundance in cartilaginous zones of human osteophytes. Finally, we identified Ptgs2 and Ccn2 as potentially relevant Piezo1 downstream genes in chondrocytes. Collectively, our data do not only demonstrate that Piezo1 is a critical regulator of physiological and pathological endochondral ossification processes, but also suggest that Piezo1 antagonists may be established as a novel approach to limit osteophyte formation in OA.

Role of the osteocyte in bone metastasis - The importance of networking

Metastatic bone disease is a complex condition resulting from the migration and colonization of cancer cells from their primary site to the bone microenvironment, where they typically develop a metastatic niche. Osteocytes, the most abundant cells in bone tissue and the master regulators of bone remodelling, are increasingly thought to play a crucial role in this process through intricate interactions with cancer cells. This review covers the recent progress made in exploring the multifaceted interactions between osteocytes and cancer cells in the metastatic microenvironment, highlighting the importance of signalling networks in bone metastases. Though these interactions are particularly complex, the renewed focus of researchers on osteocytes within the last 5 years has uncovered multiple new potential molecular mechanisms underlying osteocyte-mediated regulation of cancer cell survival, proliferation, and invasion. A number of key papers will be discussed in detail, emphasizing the significance of signalling pathways and molecular crosstalk, and exploring potential therapeutic strategies targeting osteocyte-cancer cell interactions to improve patient treatment and outcomes.

Mechanism of synergistic inhibitory effect of benzyl isothiocyanate and zoledronic acid combination on breast cancer induction of osteoclast differentiation

Bone is the most favored site for metastasis for each major subtype of breast cancer. Therapeutic modalities for alleviation of clinical symptoms associated with bone metastasis include surgical resection, radiation, and bone-targeted therapies, including bisphosphonates (e.g., zoledronic acid; ZA) and a humanized antibody against receptor activator of nuclear factor-κB ligand (denosumab). However, the bone-targeted therapies are expensive, and have poor pharmacokinetic attributes and/or serious adverse effects. Therefore, novel strategies are needed for treatment of bone metastasis or to increase effectiveness of existing bone-targeted therapies. We have shown previously that benzyl isothiocyanate (BITC) is a novel inhibitor of osteoclast differentiation in vitro and bone metastasis in vivo. The present study shows that BITC + ZA combination synergistically inhibits osteoclast differentiation induced by addition of conditioned media from breast cancer cells. These effects were associated with a significant increase in levels of several antiosteoclastogenic cytokines, including interferons, interleukin (IL)-3, IL-4, and IL-27. Kyoto Encyclopedia of Genes and Genomes pathway analysis of RNA-seq data from BITC and/or ZA-treated cells revealed downregulation of genes of many pathways (e.g., actin cytoskeleton, Hippo signaling, etc.) by treatment with BITC + ZA combination, but not by BITC alone or ZA alone. Confocal microscopy confirmed severe disruption of actin cytoskeleton upon treatment of MCF-7 and MDA-MB-231 cells with the BITC + ZA combination. This combination also decreased the nuclear level of yes-associated protein, a core component of Hippo signaling. In conclusion, the present study offers a novel combination for prevention or treatment of bone metastasis of breast cancer.

Biosynthesized Silver Nanoparticles Inhibit Osteoclastogenesis by Suppressing NF-κB Signaling Pathways

Osteoclasts overactivity plays a critical role in the progress of inflammatory bone loss. In addition, ROS can facilitate the formation and function of osteoclasts. Silver nanoparticles (Ag NPs) with ROS scavenging activity are potential candidates for inflammatory bone loss. In this regard, the biosynthetic Ag NPs with low toxicity and high stability by using Flos Sophorae Immaturus extract as the reducing and capping agents are reported. The inflammatory bone loss model is established by injecting LPS. Quantitative reverse transcription-polymerase chain reaction and Western Blot are utilized to determine the expression level of target biomarkers related to osteoclast formation. Ag NPs can significantly reduce the number of TRAP-positive (TRAP+ ) cells. In addition, Ag NPs down-regulate the expression of biomarkers relevant to osteoclast formation. Interestingly, Ag NPs can effectively suppress osteoclast formation via down-regulating ROS-mediated phosphorylation of NF-κB pathways. The in vivo study shows that Ag NPs can ameliorate bone density and decrease osteoclast number. Due to these benefits, the constructed Ag NPs can delay the progression of inflammatory bone loss. These findings suggest that Ag NPs are a potential therapeutic agent in the treatment of inflammatory bone loss.

A Missense Variant in TP53 Could Be a Genetic Biomarker Associated with Bone Tissue Alterations

Metabolic bone diseases cover a broad spectrum of disorders that share alterations in bone metabolism that lead to a defective skeleton, which is associated with increasing morbidity, disability, and mortality. There is a close connection between the etiology of metabolic bone diseases and genetic factors, with TP53 being one of the genes associated therewith. The single nucleotide polymorphism (SNP) Arg72Pro of TP53 is a genetic factor associated with several pathologies, including cancer, stroke, and osteoporosis. Here, we aim to analyze the influence of the TP53 Arg72Pro SNP on bone mass in humanized Tp53 Arg72Pro knock-in mice. This work reports on the influence of the TP53 Arg72Pro polymorphism in bone microarchitecture, OPG expression, and apoptosis bone status. The results show that the proline variant of the TP53 Arg72Pro polymorphism (Pro72-p53) is associated with deteriorated bone tissue, lower OPG/RANK ratio, and lower apoptosis in bone tissue. In conclusion, the TP53 Arg72Pro polymorphism modulates bone microarchitecture and may be a genetic biomarker that can be used to identify individuals with an increased risk of suffering metabolic bone alterations.

Bone-targeting engineered small extracellular vesicles carrying anti-miR-6359-CGGGAGC prevent valproic acid-induced bone loss

The clinical role and underlying mechanisms of valproic acid (VPA) on bone homeostasis remain controversial. Herein, we confirmed that VPA treatment was associated with decreased bone mass and bone mineral density (BMD) in both patients and mice. This effect was attributed to VPA-induced elevation in osteoclast formation and activity. Through RNA-sequencing, we observed a significant rise in precursor miR-6359 expression in VPA-treated osteoclast precursors in vitro, and further, a marked upregulation of mature miR-6359 (miR-6359) in vivo was demonstrated using quantitative real-time PCR (qRT-PCR) and miR-6359 fluorescent in situ hybridization (miR-6359-FISH). Specifically, the miR-6359 was predominantly increased in osteoclast precursors and macrophages but not in neutrophils, T lymphocytes, monocytes and bone marrow-derived mesenchymal stem cells (BMSCs) following VPA stimulation, which influenced osteoclast differentiation and bone-resorptive activity. Additionally, VPA-induced miR-6359 enrichment in osteoclast precursors enhanced reactive oxygen species (ROS) production by silencing the SIRT3 protein expression, followed by activation of the MAPK signaling pathway, which enhanced osteoclast formation and activity, thereby accelerating bone loss. Currently, there are no medications that can effectively treat VPA-induced bone loss. Therefore, we constructed engineered small extracellular vesicles (E-sEVs) targeting osteoclast precursors in bone and naturally carrying anti-miR-6359 by introducing of EXOmotif (CGGGAGC) in the 3'-end of the anti-miR-6359 sequence. We confirmed that the E-sEVs exhibited decent bone/osteoclast precursor targeting and exerted protective therapeutic effects on VPA-induced bone loss, but not on ovariectomy (OVX) and glucocorticoid-induced osteoporotic models, deepening our understanding of the underlying mechanism and treatment strategies for VPA-induced bone loss.

Identification of the transcriptome signatures and immune-inflammatory responses in postmenopausal osteoporosis

Postmenopausal osteoporosis is the most common type of osteoporosis in women. To date, little is known about their transcriptome signatures, although biomarkers from peripheral blood mononuclear cells are attractive for postmenopausal osteoporosis diagnoses. Here, we performed bulk RNA sequencing of 206 samples (124 postmenopausal osteoporosis and 82 normal samples) and described the clinical phenotypic characteristics of postmenopausal women. We then highlighted the gene set enrichment analyses between the extreme T-score group and the heathy control group, revealing that some immune-inflammatory responses were enhanced in postmenopausal osteoporosis, with representative pathways including the mitogen-activated protein kinase (NES = 1.6, FDR <0.11) pathway and B_CELL_RECEPTOR (NES = 1.69, FDR <0.15) pathway. Finally, we developed a combined risk prediction model based on lasso-logistic regression to predict postmenopausal osteoporosis, which combined eleven genes (PTGS2, CXCL16, NECAP1, RPS23, SSR3, CD74, IL4R, BTBD2, PIGS, LILRA2, MAP3K11) and three pieces of clinical information (age, procollagen I N-terminal propeptide, β isomer of C-terminal telopeptide of type I) and provided the best prediction ability (AUC = 0.97). Taken together, this study filled a gap in the large-scale transcriptome signature profiles and revealed the close relationship between immune-inflammatory responses and postmenopausal osteoporosis, providing a unique perspective for understanding the occurrence and development of postmenopausal osteoporosis.

Crosstalk Between the Neuroendocrine System and Bone Homeostasis

The homeostasis of bone microenvironment is the foundation of bone health and comprises 2 concerted events: bone formation by osteoblasts and bone resorption by osteoclasts. In the early 21st century, leptin, an adipocytes-derived hormone, was found to affect bone homeostasis through hypothalamic relay and the sympathetic nervous system, involving neurotransmitters like serotonin and norepinephrine. This discovery has provided a new perspective regarding the synergistic effects of endocrine and nervous systems on skeletal homeostasis. Since then, more studies have been conducted, gradually uncovering the complex neuroendocrine regulation underlying bone homeostasis. Intriguingly, bone is also considered as an endocrine organ that can produce regulatory factors that in turn exert effects on neuroendocrine activities. After decades of exploration into bone regulation mechanisms, separate bioactive factors have been extensively investigated, whereas few studies have systematically shown a global view of bone homeostasis regulation. Therefore, we summarized the previously studied regulatory patterns from the nervous system and endocrine system to bone. This review will provide readers with a panoramic view of the intimate relationship between the neuroendocrine system and bone, compensating for the current understanding of the regulation patterns of bone homeostasis, and probably developing new therapeutic strategies for its related disorders.

Cooperation between T and B cells reinforce the establishment of bone metastases in a mouse model of breast cancer

Immune cells educated by the primary breast tumor and their secreted factors support the formation of bone pre-metastatic niche. Indeed, we showed that RANKL+ CD3+ T cells, specific for the 4T1 mammary carcinoma cell line, arrive at the bone marrow before metastatic cells and set the pre-metastatic niche. In the absence of RANKL expressed by T cells, there is no pre-metastatic osteolytic disease and bone metastases are completely blocked. Adding to the role of T cells, we have recently demonstrated that dendritic cells assist RANKL+ T cell activities at bone pre-metastatic niche, by differentiating into potent bone resorbing osteoclast-like cells, keeping their antigen-presenting cell properties, providing a positive feedback loop to the osteolytic profile. Here we are showing that bone marrow-derived CD19+ B cells, from 4T1 tumor-bearing mice, also express the pro-osteoclastogenic cytokine receptor activator of NFκB ligand (RANKL). Analysis of trabecular bone mineral density by conventional histomorphometry and X-ray microtomography (micro-CT) demonstrated that B cells expressing RANKL cooperate with 4T1-primed CD3+ T cells to induce bone loss. Moreover, RANKL expression by B cells depends on T cells activity, since experiments performed with B cells derived from 4T1 tumor-bearing nude BALB/c mice resulted in the maintenance of trabecular bone mass instead of bone loss. Altogether, we believe that 4T1-primed RANKL+ B cells alone are not central mediators of bone loss in vivo but when associated with T cells induce a strong decrease in bone mass, accelerating both breast cancer progression and bone metastases establishment. Although several studies performed in different pathological settings, showed that B cells, positively and negatively impact on osteoclastogenesis, due to their capacity to secret pro or anti-osteoclastogenic cytokines, as far as we know, this is the first report showing the role of RANKL expression by B cells on breast cancer-derived bone metastases scenario.

Cinchonine: A Versatile Pharmacological Agent Derived from Natural Cinchona Alkaloids

BACKGROUND

Cinchonine is one of the Cinchona alkaloids that is commercially extracted from the Peruvian bark of Cinchona officinalis L. (Family: Rubiaceae). It is also obtained in much lower quantities from other species of Cinchona, such as Cinchona calisaya, Cinchona succirubra, and Cinchona pubescens, and in some other plants, such as Remijia peruviana. Cinchonine has been historically used as an anti-malarial agent. It also has a wide range of other biological properties, including anti-cancer, anti-obesity, anti-inflammatory, anti-parasitic, antimicrobial, anti-platelet aggregation, and anti-osteoclast differentiation.

AIM AND OBJECTIVE

This review discusses the pharmacological activity of cinchonine under different experimental conditions, including in silico, in vitro, and in vivo. It also covers the compound's physicochemical properties, toxicological aspects, and pharmacokinetics.

METHODOLOGY

A comprehensive literature search was conducted on multiple online databases, such as PubMed, Scopus, and Google Scholar. The aim was to retrieve a wide range of review/research papers and bibliographic sources. The process involved applying exclusion and inclusion criteria to ensure the selection of relevant and high-quality papers.

RESULTS

Cinchonine has numerous pharmacological properties, making it a promising compound for various therapeutic applications. It induces anti-cancer activity by activating caspase-3 and PARP-1, and triggers the endoplasmic reticulum stress response. It up-regulates GRP78 and promotes the phosphorylation of PERK and ETIF-2α. Cinchonine also inhibits osteoclastogenesis, inhibiting TAK1 activation and suppressing NFATc1 expression by regulating AP-1 and NF-κB. Its potential anti-inflammatory effects reduce the impact of high-fat diets, making it suitable for targeting obesity-related diseases. However, research on cinchonine is limited, and further studies are needed to fully understand its therapeutic potential. Further investigation is needed to ensure its safety and efficacy in clinical applications.

CONCLUSION

Overall, this review article explains the pharmacological activity of cinchonine, its synthesis, and physicochemical properties, toxicological aspects, and pharmacokinetics.

The role of SphK/S1P/S1PR signaling pathway in bone metabolism

There are a large number of people worldwide who suffer from osteoporosis, which imposes a huge economic burden, so it is necessary to explore the underlying mechanisms to achieve better supportive and curative care outcomes. Sphingosine kinase (SphK) is an enzyme that plays a crucial role in the synthesis of sphingosine-1-phosphate (S1P). S1P with paracrine and autocrine activities that act through its cell surface S1P receptors (S1PRs) and intracellular signals. In osteoporosis, S1P is indispensable for both normal and disease conditions. S1P has complicated roles in regulating osteoblast and osteoclast, respectively, and there have been exciting developments in understanding how SphK/S1P/S1PR signaling regulates these processes in response to osteoporosis therapy. Here, we review the proliferation, differentiation, apoptosis, and functions of S1P, specifically detailing the roles of S1P and S1PRs in osteoblasts and osteoclasts. Finally, we focus on the S1P-based therapeutic approaches in bone metabolism, which may provide valuable insights into potential therapeutic strategies for osteoporosis.

Role of SIRT3 in bone homeostasis and its application in preventing and treating bone diseases

Bone homeostasis refers to the balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption and the maintenance of stable bone mass. SIRT3 is a class of mitochondrial protein deacetylase that influences various mitochondrial functions and is involved in the mechanisms underlying resistance to aging; regulation of bone marrow mesenchymal stem cells, osteoblasts, and osteoclasts; and development of osteoporosis, osteoarthritis, and other bone diseases. Moreover, exercise affects bones through SIRT3. Thus, studies on SIRT3 may provide insights for the treatment of bone diseases. Although SIRT3 can exert multiple effects on bone, the specific mechanism by which it regulates bone homeostasis remains unclear. By evaluating the relevant literature, this review discusses the structure and function of SIRT3, reveals the role and associated mechanisms of SIRT3 in regulating bone homeostasis and mediating bone health during exercise, and highlights the potential pharmacological value of SIRT3 in treating bone diseases.

Effect of different types of Tai Chi exercise programs on the rate of change in bone mineral density in middle-aged adults at risk of osteoporosis: a randomized controlled trial

OBJECTIVE

To evaluate three Tai Chi (TC) exercise programs as intervention measures to compare their effects on improving rate of change in bone mineral density (BMD) in elderly individuals with osteoporosis (OP) and to propose the optimal exercise duration.

METHODS

A randomized controlled trial (RCT) was conducted to identify study participants based on inclusion and exclusion criteria. Due to subject attrition, the number of participants analyzed decreased from 60 to 49. These participants were divided into four groups: 24-style TC Chuan group (24TCCG) (n = 13, 7 males/6 females), TC Kung Fu Fan group (TCKFFG) (n = 12, 5 males/7 females), TC Softball group (TCSBG) (n = 11, 6 males/5 females), and a control group (CG) (n = 13, 6 males/7 females). Except for the control group, each group received different TC exercise programs four times a week for 60 min per session, lasting for 16 weeks. BMD was measured using dual-energy X-ray absorptiometry (DXA) at the L2-L4 lumbar vertebrae, Ward's triangle, femoral neck, and greater trochanter. The rate of change of BMD was calculated using the formula.

RESULTS

Compared with CG, all three TC groups showed significant improvements in BMD changes (P < 0.05), but their effects on the improvement of femoral neck and greater tuberosity BMD change rates were similar (P > 0.05). In addition, compared to the other exercise regimens, 24TCCG demonstrated more significant improvements in BMD at the L2-L4 lumbar vertebrae region and exhibited a more pronounced improvement in Ward's triangle BMD after only 8 weeks (P < 0.05). Short-term (≤ 4 weeks) TCKFFG was more effective than TCSBG in enhancing femoral neck BMD (P < 0.05). However, statistical significance was not found (P > 0.05) in all other cases.

CONCLUSION

These three TC exercise programs have similar positive effects on the BMD of the femoral neck and greater trochanter. However, compared with other exercise schemes, 24TCC showed a more significant improvement in BMD of the L2-L4 lumbar vertebrae region after just 8 weeks, as well as a more pronounced improvement in BMD of Ward's triangle. In terms of improving femoral neck BMD, TCKFF was found to be more effective than TCSB in less than 4 weeks. This study provides evidence for the effectiveness of TC exercise in improving BMD and preventing OP in the middle-aged and elderly high-risk population.

Regulatory mechanisms of autophagy-related ncRNAs in bone metabolic diseases

Bone metabolic diseases have been tormented and are plaguing people worldwide due to the lack of effective and thorough medical interventions and the poor understanding of their pathogenesis. Non-coding RNAs (ncRNAs) are heterogeneous transcripts that cannot encode the proteins but can affect the expressions of other genes. Autophagy is a fundamental mechanism for keeping cell viability, recycling cellular contents through the lysosomal pathway, and maintaining the homeostasis of the intracellular environment. There is growing evidence that ncRNAs, autophagy, and crosstalk between ncRNAs and autophagy play complex roles in progression of metabolic bone disease. This review investigated the complex mechanisms by which ncRNAs, mainly micro RNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), regulate autophagic pathway to assist in treating bone metabolism disorders. It aimed at identifying the autophagy role in bone metabolism disorders and understanding the role, potential, and challenges of crosstalk between ncRNAs and autophagy for bone metabolism disorders treatment.

Unloading-Induced Skeletal Interoception Alters Hypothalamic Signaling to Promote Bone Loss and Fat Metabolism

Microgravity is the primary factor that affects human physiology in spaceflight, particularly bone loss and disturbances of the central nervous system. However, little is known about the cellular and molecular mechanisms of these effects. Here, it is reported that in mice hindlimb unloading stimulates expression of neuropeptide Y (NPY) and tyrosine hydroxylase (TH) in the hypothalamus, resulting in bone loss and altered fat metabolism. Enhanced expression of TH and NPY in the hypothalamus occurs downstream of a reduced prostaglandin E2 (PGE2)-mediated ascending interoceptive signaling of the skeletal interoception. Sympathetic antagonist propranolol or deletion of Adrb2 in osteocytes rescue bone loss in the unloading model. Moreover, depletion of TH+ sympathetic nerves or inhibition of norepinephrine release ameliorated bone resorption. Stereotactic inhibition of NPY expression in the hypothalamic neurons reduces the food intake with altered energy expenditure with a limited effect on bone, indicating hypothalamic neuroendocrine factor NPY in the facilitation of bone formation by sympathetic TH activity. These findings suggest that reduced PGE2-mediated interoceptive signaling in response to microgravity or unloading has impacts on the skeletal and central nervous systems that are reciprocally regulated.

Dihydro-β-agarofuran-type sesquiterpenoids from the seeds of Tripterygium wilfordii (Thunder God Vine) and evaluation of their anti-osteoclastogenesis and immunosuppressive activities

Extensive phytochemical investigation of the seeds of Tripterygium wilfordii led to the identification of 54 polyesterified dihydro-β-agarofuran-type sesquiterpenoids, including 27 previously undescribed ones, named Tripwilin I-XXVII (1-27). Comprehensive spectroscopic and single-crystal X-ray diffraction analyses, along with electronic circular dichroism (ECD) calculations were used for the structural elucidation of the new compounds. Biological assay revealed that 37 compounds among the isolates exhibited significant inhibition against osteoclastogenesis induced by receptor activator of nuclear factor-κB ligand (RANKL) at 10 µM. Further investigation indicated that Triptogelin C-3 (54), with the most potent osteoclastogenesis inhibitory activity, regulated the osteoclast marker genes (MMP-9, c-Fos, CTSK, and TRAP) and proteins in a dose-dependent manner in vitro. Besides, celaforin D-1 (28), 1α,6β,15-triacetoxy-8α,9α-dibenzoyloxy-2α-hydroxydihydro-β-agarofuran (34), triptogelin A-2 (37), and chiapen D (49) showed moderate suppressive effects on the proliferation of T and B lymphocytes with IC50 values ranging between 8.1 ± 0.8 and 19.0 ± 0.9 μM.

Metallothionein 3 promotes osteoclast differentiation and survival by regulating the intracellular Zn2+ concentration and NRF2 pathway

In osteoclastogenesis, the metabolism of metal ions plays an essential role in controlling reactive oxygen species (ROS) production, mitochondrial biogenesis, and survival, and differentiation. However, the mechanism regulating metal ions during osteoclast differentiation remains unclear. The metal-binding protein metallothionein (MT) detoxifies heavy metals, maintains metal ion homeostasis, especially zinc, and manages cellular redox levels. We carried out tests using murine osteoclast precursors to examine the function of MT in osteoclastogenesis and evaluated their potential as targets for future osteoporosis treatments. MT genes were significantly upregulated upon differentiation from osteoclast precursors to mature osteoclasts in response to receptor activators of nuclear factor-κB (NF-κB) ligand (RANKL) stimulation, and MT3 expression was particularly pronounced in mature osteoclasts among MT genes. The knockdown of MT3 in osteoclast precursors demonstrated a remarkable inhibition of differentiation into mature osteoclasts. In preosteoclasts, MT3 knockdown suppressed the activity of mitogen-activated protein kinase (MAPK) and NF-κB signaling pathways upon RANKL stimulation, leading to affect cell survival through elevated cleaved Caspase 3 and poly (ADP-ribose) polymerase (PARP) levels. Additionally, ROS levels were decreased, and nuclear factor erythroid 2-related factor 2 (NRF2) (a suppressor of ROS) and the downstream antioxidant proteins, such as catalase (CAT) and heme oxygenase 1 (HO-1), were more highly expressed in the MT3 preosteoclast knockdowns. mitochondrial ROS, which is involved in mitochondrial biogenesis and the production of reactive oxygen species, were similarly decreased because cAMP response element-binding (CREB) and peroxisome proliferator-activated receptor γ coactivator 1β (PGC-1β) were less activated due to MT3 depletion. Thus, by modulating ROS through the NRF2 pathway, MT3 plays a crucial role in regulating osteoclast differentiation and survival, acting as a metabolic modulator of intracellular zinc ions.

Kisspeptin (Kp-10) inhibits in vitro osteogenic differentiation of multipotent mesenchymal stromal cells extracted from the bone marrow of adult rats

Kisspeptin (Kp-10) is a neuropeptide that binds to GPR54 receptors, exerting several functions mainly in the nervous and reproductive systems of the body. However, its effects and mechanisms of action on the skeletal system remain poorly understood. This study evaluated the effects of different concentrations of Kp-10 on in vitro osteogenic differentiation of multipotent mesenchymal stromal cells (MSCs) extracted from the bone marrow (BM) of adult Wistar rats. Two-month-old female rats were euthanized to extract BM from long bones to obtain MSCs. Four experimental groups were established in vitro: a control and Kp-10 at concentrations of 0.01, 0.05 and, 0.1 µg/mL. After induction of osteogenic differentiation, cell viability was evaluated using the 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyl tetrazolium bromide (MTT) assay, alkaline phosphatase activity, collagen synthesis, percentage of area covered by MSCs/field and mineralized nodules/field, and immunocytochemistry of the GPR54 receptor tests. Furthermore, evaluation of gene transcripts for type I collagen, Runx-2, Bmp-2, bone sialoprotein, osteocalcin and osteopontin was performed using real-time RT-qPCR. It was observed that MSCs expressed GPR54 receptor to which Kp-10 binds during osteogenic differentiation, promoting a negative effect on osteogenic differentiation. This effect was observed at all the Kp-10 concentrations in a concentration-dependent manner, characterized by a decrease in the activity of alkaline phosphatase, collagen synthesis, mineralized nodules, and decreased expression of gene transcripts for type I collagen, osteocalcin, osteopontin, and Runx-2. Thus, Kp-10 inhibits in vitro osteogenic differentiation of MSCs extracted from the BM of adult Wistar rats.

Lipolysis supports bone formation by providing osteoblasts with endogenous fatty acid substrates to maintain bioenergetic status

Bone formation is a highly energy-demanding process that can be impacted by metabolic disorders. Glucose has been considered the principal substrate for osteoblasts, although fatty acids are also important for osteoblast function. Here, we report that osteoblasts can derive energy from endogenous fatty acids stored in lipid droplets via lipolysis and that this process is critical for bone formation. As such, we demonstrate that osteoblasts accumulate lipid droplets that are highly dynamic and provide the molecular mechanism by which they serve as a fuel source for energy generation during osteoblast maturation. Inhibiting cytoplasmic lipolysis leads to both an increase in lipid droplet size in osteoblasts and an impairment in osteoblast function. The fatty acids released by lipolysis from these lipid droplets become critical for cellular energy production as cellular energetics shifts towards oxidative phosphorylation during nutrient-depleted conditions. In vivo, conditional deletion of the ATGL-encoding gene Pnpla2 in osteoblast progenitor cells reduces cortical and trabecular bone parameters and alters skeletal lipid metabolism. Collectively, our data demonstrate that osteoblasts store fatty acids in the form of lipid droplets, which are released via lipolysis to support cellular bioenergetic status when nutrients are limited. Perturbations in this process result in impairment of bone formation, specifically reducing ATP production and overall osteoblast function.

Synthesis and evaluation of 2-NMPA derivatives as potential agents for prevention of osteoporosis in vitro and in vivo

Abnormal osteoclast differentiation causes various bone disorders such as osteoporosis. Targeting the formation and activation of osteoclasts has been recognized as an effective approach for preventing osteoporosis. Herein, we synthesized eleven 2-NMPA derivatives which are (2-(2-chlorophenoxy)-N-(4-alkoxy-2-morpholinophenyl) acetamides, and evaluated their suppression effects on osteoclastogenesis in vitro by using TRAP-staining assay. Among the synthesized eleven novel 2-NMPAs, 4-(2-(2-chlorophenoxy)acetamido)-3-morpholinophenyl trifluoromethanesulfonate (11b), 4-(2-(2-chlorophenoxy) acetamido)-3-morpholinophenyl-3-(N-(2-oxo-2-((2-(phenylthio) phenyl) amino) ethyl)methylsulfonamido)benzoate (11d), and 4-(2-(2-chlorophenoxy) acetamido)-3-morpholinophenyl 4-acetamidobenzenesulfonate (11h) displayed highly inhibitory bioactivity on the differentiation of primary osteoclasts. 11h was selected for further investigation of the inhibitory effects and potential mechanism involved in the suppression of osteoclastogenesis. In vitro analysis suggested that 11h inhibited osteoclastogenesis with an IC50 of 358.29 nM, decreased the formation of F-action belts and bone resorption, without interfering cell viability and osteoblast differentiation. Furthermore, the mRNA expressions of osteoclast-specific genes such as Acp5, Nfatc1, Dc-stamp, Atp6v0d2, Mmp9, and Ctsk significantly decreased following 11h treatment. RANKL-induced osteoclast-specific proteins analysis demonstrated that 11h suppressed osteoclast differentiation by downregulating of RANKL-mediated TRAF6 expression, followed by inactivation of PI3K/AKT and IκBα/NF-κB signaling pathways. Finally, 11h inhibited ovariectomy-induced bone loss in vivo. Therefore, the current work highlighted the therapeutic potential of 11h as an anti-osteoporosis lead compound.

m6A demethylase FTO and osteoporosis: potential therapeutic interventions

Osteoporosis is a common bone disease, characterized by a descent in bone mass due to the dysregulation of bone homeostasis. Although different studies have identified an association between osteoporosis and epigenetic alterations in osteogenic genes, the mechanisms of osteoporosis remain unclear. N6-methyladenosine (m6A) modification is a methylated adenosine nucleotide, which regulates the translocation, exporting, translation, and decay of RNA. FTO is the first identified m6A demethylase, which eliminates m6A modifications from RNAs. Variation in FTO disturbs m6A methylation in RNAs to regulate cell proliferation, differentiation, and apoptosis. Besides, FTO as an obesity-associated gene, also affects osteogenesis by regulating adipogenesis. Pharmacological inhibition of FTO markedly altered bone mass, bone mineral density and the distribution of adipose tissue. Small molecules which modulate FTO function are potentially novel remedies to the treatment of osteoporosis by adjusting the m6A levels. This article reviews the roles of m6A demethylase FTO in regulating bone metabolism and osteoporosis.

Ageing and Inflammation: What Happens in Periodontium?

Periodontitis is a chronic inflammatory disease with a high incidence and severity in the elderly population, making it a significant public health concern. Ageing is a primary risk factor for the development of periodontitis, exacerbating alveolar bone loss and leading to tooth loss in the geriatric population. Despite extensive research, the precise molecular mechanisms underlying the relationship between ageing and periodontitis remain elusive. Understanding the intricate mechanisms that connect ageing and inflammation may help reveal new therapeutic targets and provide valuable options to tackle the challenges encountered by the rapidly expanding global ageing population. In this review, we highlight the latest scientific breakthroughs in the pathways by which inflammaging mediates the decline in periodontal function and triggers the onset of periodontitis. We also provide a comprehensive overview of the latest findings and discuss potential avenues for future research in this critical area of investigation.

Association between triglyceride-glucose index and bone mineral density in US adults: a cross sectional study

OBJECTIVE

Disorders in glucose and lipid metabolism have been shown to exert an influence on bone metabolism. The TyG index, which combines measures of glucose and triglycerides, provides insights into the overall metabolic status. However, the investigation of concurrent disturbances in glucose and lipid metabolism and their specific implications for bone metabolism remains limited in the existing research literature. This study aimed to explore the correlation between the TyG index and bone mineral density (BMD) in US adults.

METHODS

In the National Health and Nutrition Examination Survey (NHANES), subjects were classified based on the TyG index into four groups (< 7.97, 7.97-8.39, 8.39-8.85, > 8.86). Linear regression analysis was conducted to determine the β value and 95% confidence interval (CI). Four multivariable models were constructed. Restricted cubic spline analyses and piecewise linear regression were employed to identify the association between the BMD and TyG index. An analysis of subgroups was also conducted in this study.

RESULTS

Significant variations in related characteristics were found among the US adult population, who were distributed into four groups based on the quartiles of the TyG index. A negative correlation between the TyG index and lumbar spine BMD was observed. In the multi-adjusted models, compared to Q1 of the TyG index, the β for Q4 of the TyG index for lumbar spine BMD was [β = - 0.008, 95% CI (- 0.017, 0)] in US adults. The association between the TyG index and lumbar spine BMD was found to be nonlinear (all nonlinear p < 0.001), with a threshold value based on restricted cubic spline analyses. Above the threshold point, the β for lumbar spine BMD was - 0.042 (95% CI, - 0.059, - 0.024). Below the threshold points, no significant difference was observed (p > 0.05). No significant interactions were observed among subgroups based on age, gender, presence of diabetes, BMI, and use of antidiabetic and antihyperlipidemic agents. Similar patterns of association were observed in total and subtotal bone density.

CONCLUSIONS

This study identified a nonlinear association between the TyG index and BMD in the US population. Furthermore, an increased level of the TyG index may indicate a higher risk of osteoporosis among US adults. These findings highlight the importance of considering glucose and lipid metabolism disturbances in understanding bone health and the potential for developing preventive strategies for osteoporosis.

Increased local bone turnover in patients with chronic periprosthetic joint infection

Aims

The management of periprosthetic joint infection (PJI) remains a major challenge in orthopaedic surgery. In this study, we aimed to characterize the local bone microstructure and metabolism in a clinical cohort of patients with chronic PJI.

Methods

Periprosthetic femoral trabecular bone specimens were obtained from patients suffering from chronic PJI of the hip and knee (n = 20). Microbiological analysis was performed on preoperative joint aspirates and tissue specimens obtained during revision surgery. Microstructural and cellular bone parameters were analyzed in bone specimens by histomorphometry on undecalcified sections complemented by tartrate-resistant acid phosphatase immunohistochemistry. Data were compared with control specimens obtained during primary arthroplasty (n = 20) and aseptic revision (n = 20).

Results

PJI specimens exhibited a higher bone volume, thickened trabeculae, and increased osteoid parameters compared to both control groups, suggesting an accelerated bone turnover with sclerotic microstructure. On the cellular level, osteoblast and osteoclast parameters were markedly increased in the PJI cohort. Furthermore, a positive association between serum (CRP) but not synovial (white blood cell (WBC) count) inflammatory markers and osteoclast indices could be detected. Comparison between different pathogens revealed increased osteoclastic bone resorption parameters without a concomitant increase in osteoblasts in bone specimens from patients with Staphylococcus aureus infection, compared to those with detection of Staphylococcus epidermidis and Cutibacterium spp.

Conclusion

This study provides insights into the local bone metabolism in chronic PJI, demonstrating osteosclerosis with high bone turnover. The fact that Staphylococcus aureus was associated with distinctly increased osteoclast indices strongly suggests early surgical treatment to prevent periprosthetic bone alterations.

Bone Trans-omics: Integrating Omics to Unveil Mechanistic Molecular Networks Regulating Bone Biology and Disease

PURPOSE OF REVIEW

Recent advancements in "omics" technologies and bioinformatics have afforded researchers new tools to study bone biology in an unbiased and holistic way. The purpose of this review is to highlight recent studies integrating multi-omics data gathered from multiple molecular layers (i.e.; trans-omics) to reveal new molecular mechanisms that regulate bone biology and underpin skeletal diseases.

RECENT FINDINGS

Bone biologists have traditionally relied on single-omics technologies (genomics, transcriptomics, proteomics, and metabolomics) to profile measureable differences (both qualitative and quantitative) of individual molecular layers for biological discovery and to investigate mechanisms of disease. Recently, literature has grown on the implementation of integrative multi-omics to study bone biology, which combines computational and informatics support to connect multiple layers of data derived from individual "omic" platforms. This emerging discipline termed "trans-omics" has enabled bone biologists to identify and construct detailed molecular networks, unveiling new pathways and unexpected interactions that have advanced our mechanistic understanding of bone biology and disease. While the era of trans-omics is poised to revolutionize our capacity to answer more complex and diverse questions pertinent to bone pathobiology, it also brings new challenges that are inherent when trying to connect "Big Data" sets. A concerted effort between bone biologists and interdisciplinary scientists will undoubtedly be needed to extract physiologically and clinically meaningful data from bone trans-omics in order to advance its implementation in the field.