Bone Volume Research Articles

Bone-targeted ultrasound-responsive nanobubbles for siRNA delivery to treat osteoporosis in mice

This project aimed to study the efficacy of a bone-targeted ultrasound-responsive nanobubble (NB) platform to deliver gene-silencing cathepsin K (CTSK) siRNA into the bone for osteoporosis treatment using in vitro and in vivo studies. To this end, characterization of CTSK siRNA loaded NB functionalized with alendronate (NB-CTSK siRNA-AL) was performed using transmission electron microscopy (TEM) imaging, and a release profile was obtained through fluorescent spectroscopy. In vitro studies were conducted by culturing NB-CTSK siRNA-AL with osteoclasts to evaluate siRNA uptake, CTSK expression, and the expression of tartrate-resistant acid phosphatase (TRAP). A control group and an NB-CTSK siRNA-AL treated group of ovariectomized (OVX) mice (n = 4) were tested. The OVX group that received treatment underwent weekly sessions for 4 weeks, during which they were exposed to low-intensity pulsed ultrasound (LIPUS) stimulation following administration of NB-CTSK siRNA-AL, prior to being sacrificed. Both groups underwent a series of tests to evaluate the bone targeting, safety, and efficacy of the nanoplatform. These tests included biodistribution studies conducted at 4 h and 24 h post-injection, a 3-point bending test of the femurs, nano-computed tomography analysis, as well as Hematoxylin & Eosin histological staining, Masson's Trichrome staining, and CTSK staining. The biodistribution showed the accumulation of NB-CTSK siRNA-AL in the bone and liver. Results showed that the OVX mice treated with NB-CTSK siRNA-AL had increased distal cortical bone thickness (174.4 ± 5.28 μm vs. 144.3 ± 10.66 μm, p > 0.05)) and bone volume fraction (16.5 ± 3.96 % vs. 6.55 ± 0.13 % (p > 0.05)). A reduced collagen degradation and downregulated CTSK expression were evident in the staining procedures. No adverse effects were recorded within histological assessments on the liver, kidney, and heart post-treatment. Morphology was shown to be normal and healthy within muscle cells post-LIPUS stimulation of NB-CTSK siRNA-AL. From these results, it can be concluded that an ultrasound-mediated NB-CTSK siRNA-AL can serve as a reliable, safe CTSK siRNA carrier to bone-specific targets for in vivo osteoporosis treatment.

Enhancing Bone Formation Through bFGF-Loaded Mesenchymal Stromal Cell Spheroids During Fracture Healing in Mice.

This study aimed to evaluate the osteogenic potential of mesenchymal stromal cell (MSC) spheroids combined with the basic fibroblast growth factor (bFGF) in a mouse femur fracture model. To begin, MSC spheroids were generated, and the expression of key trophic factors (bFGF Bmp2, and Vegfa) was assessed using quantitative PCR (qPCR). A binding assay confirmed the interaction between the bFGF and the spheroids' extracellular matrix. The spheroid cultures significantly upregulated bFGF, Bmp2, and Vegfa expression compared to the monolayers (p < 0.001), and the binding assay demonstrated effective bFGF binding to the MSC spheroids. Following these in vitro assessments, the mice were divided into five groups for the in vivo study: (1) no treatment (control), (2) spheroids alone, (3) bFGF alone, (4) bFGF-loaded spheroids (bFGF-spheroids), and (5) non-viable (frozen) bFGF-loaded spheroids (bFGF-dSpheroids). Bone formation was analyzed by a micro-CT, measuring the bone volume (BV) and bone mineral content (BMC) of the mice four weeks post-fracture. A high dose of the bFGF (10 µg) significantly promoted bone formation regardless of the presence of spheroids, as evidenced by the increases in BV (bFGF, p = 0.010; bFGF-spheroids, p = 0.006; bFGF-dSpheroids, p = 0.032) and BMC (bFGF, p = 0.023; bFGF-spheroids, p = 0.004; bFGF-dSpheroids, p = 0.014), compared to the controls. In contrast, a low dose of the bFGF (1 µg) combined with the MSC spheroids significantly increased BV and BMC compared to the control (BV, p = 0.012; BMC, p = 0.015), bFGF alone (BV, p = 0.012; BMC, p = 0.008), and spheroid (BV, p < 0.001; BMC, p < 0.001) groups. A low dose of the bFGF alone did not significantly promote bone formation (p > 0.05). The non-viable (frozen) spheroids loaded with a low dose of the bFGF resulted in a higher BV and BMC compared to the spheroids alone (BV, p = 0.003; BMC, p = 0.017), though the effect was less pronounced than in the viable spheroids. These findings demonstrate the synergistic effect of the bFGF and MSC spheroids on bone regeneration. The increased expression of the BMP-2 and VEGF observed in the initial experiments, coupled with the enhanced bone formation in vivo, highlight the therapeutic potential of this combination. Future studies will aim to elucidate the underlying molecular mechanisms and assess the long-term outcomes for bone repair strategies.

Comparative Study of Photobiomodulation Effects on Alveolar Socket Hard Tissue Healing in Rats: Application of 980 nm Versus 810 nm Lasers.

Background: This study aimed to explore the differential effects of photobiomodulation (PBM) via 980 nm and 810 nm lasers on the hard tissue healing of rat alveolar sockets, with a focus on a comparative analysis of hard tissue regeneration and osteogenic gene expression. Objective: This study aimed to explore the effects of PBM using 980 nm and 810 nm lasers on hard tissue healing of rat alveolar sockets, focusing on hard tissue regeneration and osteogenic gene expression. Materials and Methods: Thirty-six male Wistar rats (5 weeks old) had both right and left maxillary first molars extracted. Post extraction, the right alveolar sockets received PBM treatment with either 980 nm (0.3 W, 18 J/cm2) or 810 nm (0.1 W, 6 J/cm2) lasers for seven days, whereas the left sockets served as controls. Rats were euthanized on days 3, 7, 14, and 28 for histopathological, immunohistochemical, micro computed tomography (micro-CT), and quantitative polymerase chain reactionanalyses. Results: On day 3, early granulation tissue, neovascularization, and inflammatory cell aggregates were observed in all groups. By day 7, active osteoclasts and osteoblasts were noted, with a significant increase in CD31-positive cells in the 980 nm group (p < 0.05). Day 14 showed new bone formation, and by day 28, increased cancellous bone and collagen content were present in all groups, with no significant differences between them (p > 0.05). Gene expression analysis revealed higher BMP-2 and Runx-2 levels in laser-treated groups on day 14 (p < 0.05), with the 980 nm group having higher BMP-2 levels than the 810 nm group (p < 0.05). Bone sialoprotein expression was higher in laser-treated groups on days 14 and 28 (p < 0.05), and osteocalcin expression was highest in the 980 nm group on both days (p < 0.05). Micro-CT analysis showed no significant differences among groups in bone mineral density, bone surface (BS)/bone volume (BV), or bone volume (BV)/TV (total volume) indices. Conclusion: PBM with 980 nm and 810 nm lasers promotes early-stage hard tissue healing in extraction sockets, with the 980 nm laser more effectively enhancing osteogenic gene expression, suggesting its potential as an adjunctive therapy in dental and oral surgery.

Comparative analysis of alveolar bone volume reconstruction outcomes using the guided bone regeneration technique

Relevance. The success of dental implant treatment in cases of reduced alveolar bone volume hinges on restoring bone to the required dimensions in each case. The guided bone regeneration (GBR) technique, which encompasses various techniques, holds a central role in oral reconstructive surgery and dental implantology due to its capacity for continuous improvement. The authors' experience with a modified GBR technique incorporating a situational Vicryl framework (SVF) has demonstrated enhanced effectiveness, with the potential to restore vertical bone volume by 5 mm or more. This study aimed to evaluate the advantages of the modified GBR technique using SVF compared to the conventional GBR technique.Materials and methods. This study is based on a comprehensive comparative analysis of two datasets: a retrospective evaluation of dental implant treatment outcomes in 210 patients who required alveolar bone volume restoration using the classical GBR technique, and clinical data from 40 patients treated with both the classical GBR technique and the proposed modified SVF technique The oral status of 40 patients included in the clinical analysis was characterized by partial edentulism, accompanied by mild to moderate alveolar bone deformities resulting from either inflammatory resorption or natural atrophy. The retrospective group 1 (comparisons) consisted of archival data of 210 patients. Retrospective data from 210 patients and clinical data from 40 patients were subjected to statistical analysis using parametric and non-parametric methods with IBM SPSS Statistics software.Results. A comprehensive comparative analysis of retrospective and clinical data revealed the following results. The value of the integrated "restored bone volume" parameter after vertical reconstruction in group 1 was 2-3 mm. The mean value of the integrated "restored bone volume" parameter after vertical reconstruction in group 2 was 3.20±0.96 mm, while in group 3, it was 4.60±1.63 mm for patients of both sexes. Comparison of the integrated "baseline deformation" parameter by technique showed a median deformation of 2.95 mm in group 2, treated with the classical GBR technique, and 4.95 mm in group 3, treated with the modified SVF technique. Similarly, the integrated "restored bone volume" parameter showed a median value of 2.95 mm in group 2 and 4.85 mm in group 3. The average value of the integrated "restored bone volume" parameter in group 2 was comparable to retrospective data from 210 patients in group 1.Conclusion. The comprehensive analysis of alveolar bone volume reconstruction using two GBR techniques, based on "baseline deformation" and "restored bone volume" parameters, demonstrated a significant advantage of the modified GBR technique compared to the classical technique.

Puerarin alleviates osteoporosis in rats by targeting the JAK2/STAT3 signaling pathway.

Osteoporosis (OP) is a common chronic progressive bone disease that increases fracture risk in postmenopausal women. Research suggests that puerarin (Pue) may be an effective treatment for OP. This study examined the effects and underlying mechanisms of Pue in treating postmenopausal osteoporosis (PMOP) in rats. Sprague-Dawley (SD) rats underwent bilateral ovariectomy to simulate PMOP and were then treated with subcutaneous injections of Pue. Bone mineral density (BMD) was measured using a bone densitometer. Micro-CT scans assessed femur bone structure and various parameters were calculated: bone volume fraction (BV/TV), bone surface density (BS/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp), and bone surface area-to-bone volume ratio (BS/BV). Hematoxylin-eosin (HE) staining was employed to observe femoral tissue pathology. Serum levels of bone formation metabolism-related markers-osteocalcin (OC), bone alkaline phosphatase (BALP), and procollagen type I N-terminal propeptide (PINP)-were measured via enzyme-linked immunosorbent assay (ELISA). The protein expression levels of the Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway in bone tissue were evaluated using Western blotting assay. The results showed improved bone density and reduced bone loss in rats treated with Pue. There were also significant increases in serum levels of OC and BALP, indicating enhanced osteogenesis. Furthermore, there was a decrease in activation of the JAK2/STAT3 pathway in femoral tissue, suggesting a pathway inhibition. These findings indicate that Pue may combat osteoporosis by promoting osteogenesis and inhibiting activation of the JAK2/STAT3 pathway activation.

Research trends and mapping knowledge for maxillary sinus augmentation in oral and maxillofacial surgery

BackgroundThe method most frequently employed to alleviate the deficiency of vertical bone volume in the maxillary posterior region is maxillary sinus augmentation. Given its importance in the field of dental implants and its possible impact on implant survival, it is crucial to assess the caliber and bibliometric characteristics of research related to maxillary sinus augmentation. This study aimed to understand the development and trends of studies and guide future studies by performing a bibliometric analysis of research related to maxillary sinus augmentation. MethodsThe Web of Science database was searched on 29.05.2024 with the developed search strategy. Articles were listed in descending order according to the number of citations and analyzed using the Bibliometrix program prepared in R base. The articles were analyzed in four sections: performance analysis, word analysis, collaboration analysis, and thematic analysis. ResultsWang HL is the most frequently listed author on this topic with 24 h-indexes and 1686 total citations. The highest number of articles were published in 2017, with 102 articles with an average of 2.7 citations. The most popular keyword was "dental implants." with 426 usages. Italy and the USA are the countries that have published the most collaborative papers. Clinical Oral Implants Research comes at the top when evaluating the journals that publish on maxillary sinus augmentation based on the h-index. Basic research and technical-oriented studies between 1999 and 2005 have given way to more clinical and patient-oriented research. ConclusionThis bibliometric study will serve as a guide for future research by illustrating the existing state of knowledge and limitations regarding the development of sinus lifting methods, given the constantly growing demand for implant therapy.

Circulating Baseline CXCR3+Th2 and Th17 Cell Proportions Correlate With Trabecular Bone Loss After 48 Weeks of Biological Treatment in Early Rheumatoid Arthritis.

The high prevalence of osteoporosis in rheumatoid arthritis (RA) is due to inflammation that stimulates differentiation of osteoclasts, a process involving circulating monocytes and T cell-derived factors. The aim of this study was to evaluate relations between circulating monocytes, T cell subsets, and changes in bone characteristics before and after treatment with biological disease-modifying antirheumatic drugs (bDMARDs) in RA. Thirty patients with untreated early RA who met the American College of Rheumatology/EULAR 2010 criteria were included. Data were collected before and 48 weeks after treatment with methotrexate (MTX) together with one of three bDMARDs (abatacept, tocilizumab, or certolizumab pegol). Disease activity was measured using the Clinical Disease Activity Index, swollen or tender joint counts, C-reactive protein levels, and erythrocyte sedimentation rates. Proportions of monocyte and CD4+ T cell subsets in blood samples were analyzed by flow cytometry. Bone densitometry was performed using high-resolution peripheral quantitative computed tomography (HR-pQCT). HR-pQCT revealed an overall decrease in cortical (P = 0.009) and trabecular (P = 0.034) bone mineral density, although a subset of patients showed no bone loss after 48 weeks of treatment. The overall bone loss was not associated with age, body mass index, sex, intraarticular glucocorticoid injections, or baseline disease activity. Loss of trabecular bone volume fraction correlated with high proportions of circulating CXCR3+Th2 cells (r = -0.38, P = 0.04) and CXCR3+Th17 cells (r = -0.36, P = 0.05) at baseline. Similarly, no loss of trabecular bone volume fraction correlated with high proportions of regulatory T cells (r = 0.4, P = 0.03) at baseline. However, the associations were not significant when corrected for confounders and multiple testing. MTX together with bDMARDs efficiently reduce disease activity but only prevent bone loss in a subset of patients with RA after 48 weeks of treatment. The correlations of circulating baseline T helper cell and regulatory T cell populations with trabecular bone changes suggest a potential novel role for these cells in systemic bone homeostasis during early RA.

Body composition as a biomarker for assessing future lung cancer risk.

To investigate if body composition is a biomarker for assessing the risk of developing lung cancer. Low-dose computed tomography (LDCT) scans from the Pittsburgh Lung Screening Study (PLuSS) (n=3,635, 22 follow-up years) and NLST-ACRIN (n=16,435, 8 follow-up years) cohorts were used in the study. Artificial intelligence (AI) algorithms were developed to automatically segment and quantify subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), intramuscular adipose tissue (IMAT), skeletal muscle (SM), and bone. Cause-specific Cox proportional hazards models were used to evaluate the hazard ratios (HRs). Standard time-dependent receiver operating characteristic (ROC) analysis was used to evaluate the prognostic ability of different models over time. The final composite models were formed by seven variables: age (HR=1.20), current smoking status (HR=1.59), bone volume (HR=1.79), SM density (HR=0.29), IMAT ratio (HR=0.33), IMAT density (HR=0.56), and SAT volume (HR=0.56). The models trained on the PLuSS cohort achieved a mean AUC of 0.76 (95% CI: 0.74-0.79) over 21 follow-up years and 0.70 (95% CI: 0.66-0.74) over the first 7 follow-up years for predicting lung cancer development within the PLuSS cohort. In contrast, models trained on the PLuSS cohort alone, as well as in combination with the NLST cohorts, achieved an AUC ranging from 0.61 to 0.68 in the NLST cohort over a 7-year follow-up period. Body composition assessed on LDCT is a significant predictor of lung cancer risk and could improve the effectiveness of LDCT lung cancer screening by optimizing the screening eligibility and frequency. Body composition assessed on LDCT is a significant predictor of lung cancer risk and could improve the effectiveness of LDCT lung cancer screening by optimizing the screening eligibility and frequency. This study unveils the significant associations between body tissues and lung cancer risk.The prediction models based on body composition alone, as well as the combination of demographics and body composition features can effectively identify patients at higher risk of developing lung cancer.

A novel genetic mouse model of osteoporosis with double heterozygosity of Irx3 and Irx5 characterizes sex-dependent phenotypes in bone homeostasis

Iroquois homeobox gene 3 (Irx3) and Irx5 encode transcription factors that play crucial roles in limb development and bone formation. Previous studies using knockout mice have revealed a role of Irx3 and Irx5 in osteogenesis in young adult mice. However, whether these genes are also essential for bone homeostasis in adulthood and contribute to bone diseases remain poorly understood. Osteoporosis is a disease characterized by lower bone mineral density and disrupted bone microarchitecture, typically occurs in postmenopausal women. Here, we demonstrate that Irx3/5dHet mice with a half-reduction of Irx3 and Irx5 dosage serve as a novel model of osteoporosis. By micro-computed tomography, we found that Irx3/5dHet mice exhibited sex-dependent bone loss patterns. While male Irx3/5dHet mice progressively lost trabecular microstructures with aging, female mutants exhibited lower bone mineral density (BMD) and bone volume fraction (BV/TV) at early adulthood (9–15 weeks old) but without further loss later at 1 year of age. Bone marrow adipocytes are known to be elevated at the expenses of lower osteogenesis in osteoporotic bone marrow. Surprisingly, we found sex-dependent changes in adipogenesis at the age of skeletal maturity that bone marrow adipocytes were reduced in female Irx3/5dHet mice along with deteriorated osteogenesis, while male mice exhibited elevated adipogenesis. In summary, we reported a novel genetic model for osteoporosis-like phenotypes, highlighting sex-dependent bone mineral density and bone marrow adipocyte characteristics.

Adiposity and Mineral Balance in Chronic Kidney Disease.

Bone homeostasis is balanced between formation and resorption activities and remain in relative equilibrium. Under disease states this process is disrupted, favoring more resorption over formation, leading to significant bone loss and fracture incidence. This aspect is a hallmark for patients with chronic kidney disease mineral and bone disorder (CKD-MBD) affecting a significant portion of the population, both in the United States and worldwide. Further study into the underlying effects of the uremic microenvironment within bone during CKD-MBD are critical as fracture incidence in this patient population not only leads to increased morbidity, but also increased mortality. Lack of bone homeostasis also leads to mineral imbalance contributing to cardiovascular calcifications. One area understudied is the possible involvement of bone marrow adipose tissue (BMAT) during the progression of CKD-MBD. BMAT accumulation is found during aging and in several disease states, some of which overlap as CKD etiologies. Importantly, research has found presence of BMAT inversely correlates with bone density and volume. Understanding the underlying molecular mechanisms for BMAT formation and accumulation during CKD-MBD may offer a potential therapeutic avenue to improve bone homeostasis and ultimately mineral metabolism.

A Pilot Study Showing Application of Palatal Bone Harvesting Under Dynamic Navigation Guidance in Oral Implantology.

In cases of insufficient bone volume in the implant area, bone augmentation surgery is often required to ensure an adequate amount of bone around the implant. In autologous bone grafting procedures, some patients face insufficient bone volume at conventional intraoral bone harvesting sites. Due to the high difficulty associated with completing palatal osteotomies freehand, fewer palatal lateral osteotomies have been reported, and palatal bone blocks are not routinely used in bone augmentation procedures. With the development of digitally guided implant technology, palatal bone harvesting has become feasible. In this paper, we will present a method of obtaining a circumferential bone block of the palate for implant surgical application through dynamic navigation guidance. A total of three patients had undergone this procedure to obtain circumferential palatal bone blocks and completed bone augmentation surgery. The bone augmentation results in the implanted area have been favorable, and there has been some bone recovery at the harvesting site. This is a safe and effective way to obtain intraoral bone blocks.

Additively manufactured porous Ti6Al4V Alloy with excellent mechanical properties, corrosion resistance, in vitro and in vivo biocompatibility

In view of the insufficient bearing capacity of porous Ti6Al4V (TC4) alloy, four kinds of porous TC4 alloys with a wall thickness of 200 μm and a side length ranging from 400 to 700 μm were designed and subsequently prepared by Additive Manufacturing (Selective Laser Melting, SLM). The results indicated that the porous TC4 alloy was primarily comprised of α' phase and a small amount of β phase. As the side length increased, the size and volume of the acicular α' phase increased while the β phase decreased. Besides, the dislocation density also increased with the increase of side length. The porous TC4 alloy with a side length of 700 μm exhibited the maximum dislocation density of 6.07×1014 m2. The yield strength and elastic modulus initially decreased and then increased with the increase of side length. Moreover, the increase in side length induced the decrease of Icorr from 1.807 × 10−6 to 4.777 × 10−7 A/cm2, especially that sample 7–2 presented the best corrosion resistance with the smallest Icorr value (4.777 × 10−7 A/cm2). It was observed by in vitro assessment that the optical density (OD) of the porous TC4 alloys surpassed 75 % on days 1, 4, and 7. It was noteworthy that the OD value of the porous TC4 alloys with a side length of 700 μm surpassed 100 % on day 7. Furthermore, the number of adherent cells displayed an increasing trend with the increase in side length. After implanting into the alveolar bone of rabbits at 12th week, the porous TC4 alloy with a side length of 700 μm induced bone growth due to a higher percentage of bone volume compared to the dental implant. After 12 weeks of in vivo experiments, the results showed that the porous TC4 alloy could reduce the inflammatory response, promote the growth of bone tissue, and have excellent osteogenic properties.

Nootkatone mitigates periodontal inflammation and reduces alveolar bone loss via Nrf2/HO-1 and NF-κB pathways in rat model of periodontitis.

Periodontitis (PD) is a chronic inflammatory disease leading to alveolar bone loss. This study investigated the effect of nootkatone and regulatory mechanism in reducing periodontal inflammation and alveolar bone loss in a rat model. Twenty male Sprague-Dawley rats were divided into control, periodontitis, and nootkatone-treated groups (45 or 90 mg/kg). Ligature induction method was adopted to establish the PD model. After 21 days, rats received daily gavage of either saline or nootkatone for 10 days. Alveolar bone loss was assessed using micro-CT. Histological analyses included hematoxylin and eosin (H&E), tartrate-resistant acid phosphatase (TRAP), and Masson's trichrome stainings. Immunohistochemistry for heme oxygenase 1 (HO-1) and nuclear factor erythroid-2 related factor 2 (Nrf2) were performed in periodontal tissues. Content of inflammatory cytokines IL-1β, IL-6, and TNF-α in gingival tissues around ligature were assessed using ELISA kits. Malondialdehyde (MDA) level and superoxide dismutase (SOD) activity were analyzed and Western blot for NF-κB expression in gingival tissues were performed. Nootkatone significantly reduced the distance from cementoenamel junction to alveolar bone crest (CEJ-ABC), enhanced bone mineral density (BMD), bone volume (BV), and BV/total volume (TV) ratio in ligature-induced rats. Higher dose of nootkatone (90 mg/kg) did not show more significant therapeutic effect than lower dose (45 mg/kg). Histological staining showed decreased osteoclasts' number and improved bone architecture in the nootkatone group. Content of IL-1β, IL-6, and TNF-α and inflammatory cell infiltration level in gingival tissues around the ligature were decreased in the nootkatone-treatment rats. Nootkatone increased Nrf2 and HO-1 protein expression and decreased NF-κB protein level, suppressing MDA levels and enhancing SOD activity. In a rat model, nootkatone effectively mitigates periodontal inflammation and alveolar bone loss through the Nrf2/HO-1 and NF-κB pathways. These findings suggest nootkatone as a promising therapeutic agent for the treatment of periodontitis.

Therapeutic effect of bloodletting on bone deterioration induced by hypobaric hypoxia in young rats

ObjectivesHigh-altitude regions, comprising hypoxic conditions, are associated with different altitude-induced pathologies, including a reduction in bone density. Elucidating the mechanisms underlying bone degradation in such environments and developing targeted interventions and therapeutics is important. Bloodletting therapy has promising clinical applications, but its effects on the skeletal system and bone homeostasis are not well understood. The aim of this study was to investigate the effects of a hypobaric hypoxia environment on specific femoral morphological and structural properties, including bone volume, cortical thickness, and trabecular microarchitecture, in juvenile Sprague–Dawley (SD) rats, and to explore the potential modulating effects of a bloodletting intervention on these parameters. MethodsMale SD rats, 6 weeks of age, were subjected to a simulated hypobaric hypoxia environment, replicating a 5000-m altitude, for 12 weeks. For the bloodletting intervention group, rats were subjected to a weekly 500 μL tail vein blood withdrawal. Micro-CT technology, hematoxylin and eosin staining, and tartrate-resistant acid phosphatase staining were employed to comprehensively assess the femoral microstructure, tissue architecture, and cellular morphology. Additionally, immunofluorescence analysis was conducted to quantify the expression of key proteins, and transcriptome analysis was performed to identify differentially expressed genes. ResultsExposure of rats to hypobaric hypoxia led to a significant reduction in bone mineral content, trabecular bone number, and cortical bone thickness, suggesting a deterioration of bone microstructure. Additionally, the hypoxic environment upregulated the expression of RANKL and HIF-1α, while downregulating RUNX2. Notably, although bloodletting intervention did not significantly reverse these bone structural changes, transcriptome analysis revealed its regulatory influence on the expression of key genes, particularly Mmp2, Fosl2, and URS0000B2A65A, which are implicated in pathways governing the hypoxic response, osteoclast differentiation, and PI3K–Akt signaling. ConclusionThis study highlights the detrimental effect of hypobaric hypoxia on the bone microstructure of juvenile rats and underscores the therapeutic potential of bloodletting to ameliorate this condition. Additionally, our study on the regulatory mechanisms mediating bloodletting's effects on gene expression offers fresh perspectives on bone alterations. It suggests promising avenues for the development of novel preventative measures and targeted therapies to address the challenges posed by related bone disorders.

Comparative Histological Analysis of Dentine-Derived Tooth Grafts in Maxillary vs Mandibular Socket Preservation: A Retrospective Study of 178 Cases.

(1) Background: In recent years, there has been a growing interest in tooth-derived materials as valuable alternatives to synthetic biomaterials for preventing alveolar ridge dimensional changes. This study aimed to evaluate the histological and clinical differences between alveolar ridge preservation procedures in the maxilla and mandible using demineralized dentin treated with Tooth Transformer®. (2) Methods: A total of 178 patients in good general health were enrolled, with 187 post-extractive sockets lacking buccal and/or palatal bone walls. Alveolar socket preservation procedures and histological evaluations were performed. The sites were divided into two groups: Group A (99 mandibular samples) and Group B (108 maxillary samples). After 5 months (±1 month), single bone biopsies were performed for histologic and histomorphometric analysis. (3) Results: Clinical outcomes demonstrated a good healing of hard and soft tissues with an effective maintenance of bone architecture in both groups. Histomorphometric analysis revealed a total bone volume of 50.33% (±14.86) in Group A compared to 43.53% (±12.73) in Group B. The vital new bone volume was 40.59% (±19.90) in Group A versus 29.70% (±17.68) in Group B, with residual graft dentin material volume at 7.95% (±9.85) in Group A compared to 6.75% (±9.62) in Group B. (4) Conclusions: These results indicate that tooth-derived material supports hard tissue reconstruction by following the structure of the surrounding bone tissue. A 6.8% difference observed between the maxilla and mandible reflects the inherent disparities in natural bone structures in these regions. This suggests that the bone regeneration process after tooth extraction adheres to an anatomical functional pattern that reflects the specific bone characteristics of each area, thus contributing to the preservation of the morphology and functionality of the surrounding bone tissue.

Methods to Enhance Mechanical Strength of 3D Printed Chitosan Scaffolds for Jawbone Regeneration

Current jaw reconstruction methods using autografts and allografts have limitations such as donor site morbidity, limited bone volume, and immunological rejection. As opposed to surgical methods synthetic biomaterials are used however they often fall short in providing the optimal combination of biocompatibility, mechanical strength, and customizable design required for effective jawbone reconstruction. 3D-printed chitosan scaffolds offer a promising alternative due to their biocompatibility, ease of customization, and potential for improved mechanical strength. This review explores strategies to optimize 3D-printed chitosan scaffolds for jaw reconstruction. We examine ways to increase their mechanical strength without compromising biocompatibility, with a particular emphasis on chemical modifications such as hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) cross-linking and chitosan polyelectrolyte complex formation. We also discuss the critical roles that 3D printing processes (FDM and SLA) and intrinsic chitosan qualities (degree of deacetylation) play in making an ink printable. Optimizing 3D printing methods for chitosan-ceramic composites and exploring biocompatible additives to enhance printability are identified as key areas for further research. By addressing these challenges, 3D-printed chitosan scaffolds have the potential to become next-generation biomaterials for jaw reconstruction, revolutionizing the field through precise anatomical adaptation, enhanced osteoconductivity, controlled biodegradation, and the capacity for incorporating bioactive molecules, ultimately leading to accelerated bone regeneration and improved functional and aesthetic outcomes.

The senolytic agent ABT263 ameliorates osteoporosis caused by active vitamin D insufficiency through selective clearance of senescent skeletal cells

Background/ObjectiveActive vitamin D insufficiency accelerates the development of osteoporosis, with senescent bone cells and the senescence-associated secretory phenotype (SASP) playing crucial roles. This study aimed to investigate whether the senolytic agent ABT263 could correct osteoporosis caused by active vitamin D insufficiency by selectively clearing senescent cells. MethodsBone marrow mesenchymal stem cells (BM-MSCs) from young and aged mice were treated with ABT263 in vitro, and 1,25(OH)2D-insufficient (Cyp27b1+/−) mice were administered ABT263 in vivo. Cellular, molecular, imaging, and histopathological analyses were performed to compare treated cells and mice with control groups. ResultsABT263 induced apoptosis in senescent BM-MSCs by downregulating Bcl2 and upregulating Bax expression. It also induced apoptosis in senescent BM-MSCs from 1,25(OH)2D-insufficient mice. ABT263 administration corrected bone loss caused by 1,25(OH)2D insufficiency by increasing bone density, bone volume, trabecular number, trabecular thickness, and collagen synthesis. It also enhanced osteoblastic bone formation and reduced osteoclastic bone resorption in vivo. ABT263 treatment corrected the impaired osteogenic action of BM-MSCs by promoting their proliferation and osteogenic differentiation. Furthermore, it corrected oxidative stress and DNA damage caused by 1,25(OH)2D insufficiency by increasing SOD-2 and decreasing γ-H2A.X expression. Finally, ABT263 corrected bone cell senescence and SASP caused by 1,25(OH)2D insufficiency by reducing the expression of senescence and SASP-related genes and proteins. ConclusionABT263 can correct osteoporosis caused by active vitamin D insufficiency by selectively clearing senescent skeletal cells, reducing oxidative stress, DNA damage, and SASP, and promoting bone formation while inhibiting bone resorption. These findings provide new insights into the potential therapeutic application of senolytic agents in the treatment of osteoporosis associated with active vitamin D insufficiency. The translational potential of this articleThis study highlights the therapeutic potential of ABT263, a senolytic compound, in treating osteoporosis caused by active vitamin D insufficiency. By selectively eliminating senescent bone cells and their associated SASP, ABT263 intervention demonstrates the ability to restore bone homeostasis, prevent further bone loss, and promote bone formation. These findings contribute to the growing body of research supporting the use of senolytic therapies for the prevention and treatment of age-related bone disorders. The translational potential of this study lies in the development of novel therapeutic strategies targeting cellular senescence to combat osteoporosis, particularly in cases where vitamin D insufficiency is a contributing factor. Further clinical studies are warranted to validate the efficacy and safety of ABT263 and other senolytic agents in the treatment of osteoporosis in humans.

Aerobic exercise training-induced bone and vascular adaptations in mice lacking adiponectin

Adiponectin regulates lipid and glucose metabolism, and insulin sensitivity in various target organs; however, the effects of adiponectin on bone health remain controversial. Exercise training can enhance bone density, bone microarchitecture, and blood flow. This study aimed to elucidate the role of adiponectin in adaptations of bone microarchitecture and bone vasculature in response to aerobic exercise training.Adult male C57BL/6 wild-type (WT) and homozygous adiponectin knockout (AdipoKO) mice were either treadmill exercise trained or remained sedentary for 8–10 weeks. The trabecular structures of the distal femoral metaphysis, a weight-bearing bone, and the mandible, a non-weight-bearing bone, were examined using microcomputed tomography. The femoral principal nutrient arteries were isolated to assess vasoreactivity (vasodilation and vasoconstriction) and structural remodeling.At the femoral metaphysis, impaired trabecular bone structures, including reduced connectivity density and increased trabecular spacing, were observed in AdipoKO mice compared to WT mice. In addition, nitric oxide-mediated, endothelium-dependent vasodilation was substantially reduced, and wall-to-lumen ratio was significantly increased in the femoral principal nutrient artery of AdipoKO mice. Interestingly, although exercise training-induced enhancements in trabecular connectivity density were observed at the femoral metaphysis of both WT and AdipoKO, increased vasoconstrictor responses were only observed in the femoral principal nutrient artery of WT mice, not in the AdipoKO mice. In mandibular trabecular bone, exercise training increased trabecular bone volume fraction (BV/TV, %) and intersection surface in the mandible of both WT and AdipoKO mice.These findings indicate that adiponectin is crucial for maintaining normal bone microarchitecture and vasculature. Although the absence of adiponectin compromises bone vascular adaptation to exercise training in mice, some exercise training-induced alterations in bone microarchitecture occurred in the absence of adiponectin, suggesting contribution of compensatory mechanisms during exercise training.

7943 In Obese C57Bl6 Male Mice, Weight Loss due to Caloric Restriction Reduced Bone Morphology but Improved Components of Systemic Metabolism

Abstract Disclosure: C. Chlebek: None. C. McAndrews: None. S.N. Costa: None. C.J. Rosen: None. Obesity and calorie restriction individually alter systemic cellular metabolism and affect musculoskeletal tissue health. Obesity reduces trabecular and cortical bone quality. Clinically, obese patients are advised to lose weight, despite the negative effects of calorie restriction on bone in nonobese preclinical models. Little is known about bone quality following weight loss in obese preclinical models. We hypothesized that in obese models, caloric restriction would further worsen bone quality. To induce obesity, male C57Bl6 mice (8 weeks old) received 60% high fat diet for 12 weeks (high fat feeding phase). Following obesity induction, the HFD-CR group was acclimated to control low fat diet for 2 wks and then underwent 30% caloric restriction for 8 wks (caloric restriction feeding phase). The HFD group received 60% kcal high fat diet from ages 8 to 30 wks. LFD mice received control low fat 10% kcal diet for the study duration. Mice were euthanized at 30 wks of age. Body weight, body composition, and bone mineral density were recorded at baseline and at the end of each diet. Glucose and insulin tolerance were recorded at the end of the high fat and caloric restriction feeding phases. At euthanasia, cortical and trabecular bone morphology (µCT) were assessed.Adverse metabolic parameters worsened with high fat feeding but improved by caloric restriction. Compared to LFD animals, HFD and HFD-CR mice gained body weight, fat mass, and lean mass during the high fat feeding phase. After the caloric restriction feeding phase, body weight, fat mass, and lean mass were reduced in HFD-CR compared to both HFD and LFD controls (p &amp;lt; 0.0001). After 12 weeks of high fat feeding, glucose and insulin tolerance were reduced in HFD and HFD-CR mice compared to LFD (p &amp;lt; 0.0001). Caloric restriction improved both glucose and insulin tolerance in HFD-CR mice compared to both HFD and LFD animals (p &amp;lt; 0.0001). Caloric restriction improved areal bone mineral density, but at euthanasia, HFD-CR mice had worse bone morphology compared to LFD or HFD animals. Although areal bone mineral density (aBMD) was reduced by the high fat feeding phase, HFD-CR and LFD aBMD was not different at the end of the study (p &amp;lt; 0.0001). At euthanasia, HFD-CR mice had reduced cortical area and cortical thickness (p &amp;lt; 0.05). Marrow area and moment of inertia were not different between diets. Compared to LFD, both HFD and HFD-CR mice had reduced tibial bone volume fraction (p &amp;lt; 0.05). HFD-CR animals had smaller trabecular thickness (p &amp;lt; 0.05) and greater trabecular number (p &amp;lt; 0.01) compared to HFD mice. Despite improvements in components of systemic metabolism, caloric restriction in obese preclinical models reduced bone morphology in both trabecular and cortical compartments. This work will improve our understanding of the musculoskeletal system following caloric restriction in obese models and will aid in nutritional counseling for obese patients. Presentation: 6/1/2024

7500 Effect Of Orchiectomy On Bone Microarchitecture In Male Mice With Kidney Disease

Abstract Disclosure: D. Wu: None. A. Patwardhan: None. O. Marks: None. Y. Komaru: None. E. Kefalogianni: None. R. Aurora: None. S. Dhindsa: None. A. Herrlich: None. Background: Chronic kidney disease (CKD) leads to decreased bone density and increased fracture risk. In males, an additional factor contributes to the low bone density. Around half of the men with CKD have low serum testosterone concentrations. We hypothesized that CKD and low testosterone would have an additive and detrimental effect on bone. Methods: Forty male C57BL/6 mice were divided into 4 groups: 1) renal injury, induced by ischemia-induced reperfusion (IRI) and sham orchidectomy (IRI-sham, N=8) at 2 months of age; 2) orchidectomy (ORX), performed 4 weeks after IRI (IRI + ORX, N=11); 3) sham-ORX, N=9; and 4) sham-sham surgery, N=12. 12 weeks after IRI, the mice developed renal fibrosis and decreased glomerular filtration rate, indicative of CKD. The mice were sacrificed when they were 7 months old. Femur and tibia were harvested for both histology and μCT analysis. Results: Bone volume to total volume fraction (BV/TV) was lower in the IRI-ORX (0.06±0.02) and sham-ORX (0.08±0.02), as compared to IRI-sham (0.10±0.03, p&amp;lt;0.05) and sham-sham group (0.14±0.03, p&amp;lt;0.05) respectively. Similarly, the volumetric bone mineral density (vBMD) in IRI-ORX (93±27 mgHA/cm3) and sham-ORX (112±39 mgHA/cm3) groups were lower than IRI-sham (150±43 mgHA/cm3, p&amp;lt;0.05) and sham-sham (187±30 mgHA/cm3, p&amp;lt;0.05) mice. Trabecular number (Tb.N) was decreased in the IRI-ORX group (2.7±0.7 #/mm) compared to IRI-sham group (4.1±1.1 #/mm, p&amp;lt;0.05). Tb.N was also lower in sham-ORX (3.2±1.1 #/mm) mice than sham-sham (4.5±0.2 #/mm), but not IRI-sham mice. In contrast, trabecular thickness (Tb.Th) was lower in IRI-ORX (0.035±0.002 mm) and IRI-sham (0.038±0.002 mm) compared to sham-ORX (0.045±0.005 mm) and sham-sham (0.047±0.005 mm, p&amp;lt;0.05). Trabecular spacing (Tb.Sp) was increased by 47% in IRI-ORX group compared to IRI-sham group (0.26±0.09 mm). Decreased trabecular numbers and increased spacing results in reduced connectivity density (Conn.Den), which was decreased by 60% in the IRI-ORX sham-ORX groups as compared to sham-sham group (423±58 #/mm3, p&amp;lt;0.05). 2 way ANOVA analysis showed that ORX significantly contributed to the variance in BV/TV (p&amp;lt;0.001), vBMD (p&amp;lt;0.001), Tb.N (p&amp;lt;0.01), Tb.Sp (p&amp;lt;0.01) and Conn.Den (p&amp;lt;0.001), while IRI contributed to Tb.Th (p&amp;lt;0.0001). There was no significant interaction between IRI and ORX in all endpoints. Conclusions: Taken together, these data indicate that even in the presence of established CKD, ORX has a greater effect on bone mass. ORX decreased trabecular number (Tb.N) and increased trabecular spacing (Tb.Sp) to a greater extent than IRI. IRI decreased trabecular thickness (Tb.Th) while ORX had no effect on that parameter. Trabecular bone loss starts by trabecular thinning. Eventually, the trabeculae will be completely resorbed, resulting in decreased trabecular numbers and increased spacing. Our data indicate that IRI and ORX affect bone at different time points. Presentation: 6/1/2024