Osteoblast Activity Research Articles

Evaluation and Comparison of the Effect of Three Dental Luting Cements on Mineralized Bone Derived from Dental Pulp Stem Cells: An In Vitro Study.

Background and Objectives: This study aimed to investigate the effect of zinc phosphate (ZnP) cement, glass ionomer cement (GIC), and nano-integrated bio-ceramic (NIB) cement on mineralization when placed in contact with bone tissue-forming cells. Materials and Methods: ZnP cement, GIC, and NIB cement were divided into direct and indirect groups. A total of 72 cement pellets (24 pellets of each test sample) of 3 × 1 mm (width × height) were prepared using polytetrafluoroethylene molds. A total of 3 sample groups were demarcated using 96- cell well culture plates. In the control group, 24 wells were filled with mineralized osteoblasts and 1 µL of gingival crevicular fluid (GCF). In test group 1, to show a direct effect, 36 samples were plated with mineralized osteoblasts and 1 µL GCF for 24 h; the cells were directly exposed to cement pellets. A total of 36 samples were immersed in GCF for 24 h; later the supernatant was transferred to the mineralized osteoblasts to demonstrate an indirect effect in test group 2. To assess the mineralization, osteoblasts were stained with alizarin red and later observed under an inverted phase-contrast microscope. Data were analyzed using the statistical package for social sciences. An independent t-test compared the direct and indirect effects of the ZnP cement, GIC, NIB cement, and control groups on the mineralization of osteoblasts derived from hDPCs. Results: A statistically significant difference was observed between the ZnP cement, GIC, and NIB cement groups (p < 0.05). ZnP cement exhibited a moderate, NIB cement the least harmful effect, and GIC showed the most harmful effect on the mineralization of osteoblast cells. Conclusions: The biocompatibility of dental luting cements is an important aspect that clinicians should consider during their selection. Nano-integrated bio-ceramic cement showed the least negative effect on the mineralization of osteoblast cells which is beneficial for the cementation of cement-retained implant prostheses. However, further studies are needed to evaluate osteoblast and osteoclast activity in vivo.

Soybean Isoflavones Alleviate Osteoarthritis Through Modulation of the TSC1/mTORC1 Signaling Pathway to Reduce Intrachondral Angiogenesis

ABSTRACT Background The incidence of osteoarthritis (OA) is increasing, yet its pathogenesis remains largely unknown. Recent studies suggest that abnormal subchondral bone remodeling plays a crucial role in OA development, highlighting a gap in clinical treatments targeting this aspect. Soybean Isoflavone (SI) has shown potential in treating OA, although its mechanisms are not fully understood. Methods This research investigated the effects of SI on subchondral bone remodeling in an OA rat model, assessing joint damage, OARSI scores, and type H vessel formation (CD31hiEmcnhi expression). Additionally, the expression of ALP, OCN, BMP, and TSC1 was evaluated to determine involvement of the mTORC1 pathway. In vitro studies on IL-1β-induced osteoblasts further examined the impact of SI on TSC1/mTORC1 signaling and related markers. Results SI treatment reduced joint damage and OARSI scores in the rat OA model, significantly decreasing CD31hiEmcnhi expression, indicating a reduction in type H vessel formation. SI also downregulated ALP, OCN, and BMP expression while upregulating TSC1, suggesting inhibition of the mTORC1 signaling pathway and VEGF release. In vitro, SI increased TSC1 expression and decreased mTORC1 signaling, VEGF, ALP, OCN, and BMP levels in IL-1β-induced osteoblasts. Conclusion SI targets the TSC1/mTORC1 signaling pathway to suppress osteoblast activation and VEGF release, inhibiting type H vessel formation and slowing abnormal subchondral bone remodeling. These findings provide a novel therapeutic approach for OA by focusing on subchondral bone remodeling mechanisms.

Strontium-containing mineralized phospholipid coatings improve osseointegration in osteoporotic rats.

Surface treatments play an important role in enhancing the osseointegration of Titanium (Ti) and its alloys. This study introduces a method employing biomimetic hydroxyapatite (Hap) deposition guided by molecularly organized phospholipids, affixed to the metal implant surface. Using the Langmuir-Blodgett technique, phospholipids were deposited onto Ti-screws by using CaCl2 or CaCl2/SrCl2 aqueous solution in the subphase of a Langmuir trough in the target proportion (i.e. 10 and 90 mol% of Sr2+ in relation of Ca2+) followed by immersion in phosphate buffer and in supersaturated simulated body fluid. Coating composition and morphology were evaluated using infrared spectroscopy and scanning electron microscopy, respectively, while contact angle measurements assessed coating wettability and surface energy. Randomized screws were then implanted into the tibias of healthy and osteoporotic female rats (G1: Control-Machined, G2: Hap, G3: HapSr10, G4: HapSr90). Osseointegration, assessed 60 days post-implantation, included reverse torque, fluorochrome area, bone tissue-screw contact area, and linear extent of bone-screw contact. Results, grouped by surface treatment (Machined, Hap, HapSr10, HapSr90), revealed that the deposition of Hap, HapSr10, and HapSr90 resulted in thin and rough coatings composed of hydroxyapatite (Hap) on the screw surface with nanoscale pores. The coatings resulted in increased wettability and surface energy of Ti surfaces. The minerals are chemically similar to natural bone apatite as revealed by FTIR analysis. In vivo analyses indicated higher torque values for strontium-containing surfaces in the osteoporotic group (p = 0.02) and, in the control group superior torque for screw removal on the Hap surface (p = 0.023). Hydroxyapatite-treated surfaces enhance morphology, composition, and reactivity, promoting screw osseointegration in healthy and osteoporotic female rats. The incorporation of strontium into the mineral phase has been proposed to not only stimulate osteoblast activity but also reduce osteoclastic resorption, which may explain the improved outcomes observed here in experimental osteoporotic conditions.

Adsorption and Release Pattern of Recombinant Human Bone Morphogenic Proatin 2 onto Different Bone Grafts and its Consequent Osteoblasts` Activation and Neutrophils` Priming

ObjectivesControlled long-term delivery of recombinant human bone morphogenic proatin 2 (rhBMP2) eluted in a collagen scaffolds suffer from only a high initial burst release. The purpose of the current study was to investigate the long-term delivery of rhBMP2 when mixed with different bone grafts and its impact on osteoblastic activity and neutrophil priming. MethodsrhBMP2 was separately mixed with xenograft, allograft, or alloplast and incubated for 30 days. Levels of BMP2 adsorption and their release were measured using immunofluorescence and ELISA respectively. The supernatants from the grafts were then incubated with either osteoblast (Saos-2 cells) or neutrophils (differentiated from HL60) for alkaline phosphatase and oxidative stress measurements respectively. Gene expression of osteoblast functionality and neutrophil priming were measured with qRT-PCR. ResultsrhBMP2 was adsorbed onto all tested grafts, with a superior effect of alloplast. The release of the rhBMP2 from all grafts was similar and sustained for 30 days with the lowest levels in the alloplast group. Activation of osteoblast was robust in the allograft and xenograft groups, concomitant with elevated osteocalcin expression. Neutrophil priming was greatest in the xenograft group, together with elevated expression of interleukin 1β. ConclusionrhBMP2 with bone graft material constitutes its sustained release over time. This, in turn, robust osteoblast and neutrophil activity.

MicroRNA-324 mediates bone homeostasis and the regulation of osteoblast and osteoclast differentiation and activity

MicroRNAs (miRNAs) modulate the expression of other RNA molecules. One miRNA can target many transcripts, allowing each miRNA to play key roles in many biological pathways. Defects in bone homeostasis result in common age-related diseases including osteoporosis. Serum levels of miR-324-3p positively correlate with several features of bone maintenance. In contrast here, using in vivo micro-computed tomography and histology, global miR-324-null mice demonstrated increased bone mineral density and both trabecular and cortical thickness, with effect magnitudes increasing with age. The bone marrow of miR-324-null mice had reduced lipid content while TRAP staining revealed a decrease in osteoclasts, with histomorphometry demonstrating an increased rate of bone formation. Ex vivo assays showed that the high bone mass phenotype of miR-324-null mice resulted from both increased osteoblast activity and decreased osteoclastogenesis. RNA-seq analysis of osteoblasts, osteoclasts and bone marrow macrophages and target validation assays identified that the osteoclast fusion regulator Pin1 and the master osteogenic regulator Runx2 were targets of miR-324-5p in osteoclast lineage cells and osteoblasts, respectively. Indeed, in vitro Runx2 overexpression recapitulated the increased osteogenesis and decreased adipogenesis phenotype observed in vivo by the loss of miR-324. Overall, these data demonstrate the importance of miR-324 in bone homeostasis by regulating aspects of both bone formation and remodelling. Elucidation of pathways regulated by miR-324 offer promise for the treatment of bone diseases such as osteoporosis.

Elucidating the Mechanism of Large-Diameter Titanium Dioxide Nanotubes in Protecting Osteoblasts Under Oxidative Stress Environment: The Role of Fibronectin and Albumin Adsorption.

Large-diameter titanium dioxide nanotubes (TNTs) have shown promise in preserving osteoblast function under oxidative stress (OS) in vitro. However, their ability to enhance osteogenesis in vivo under OS conditions and the underlying mechanisms remain unclear. This study aimed to evaluate the osteogenic potential of 110 nm TNTs (TNT110) compared to 30 nm TNTs (TNT30) in an aging rat model exhibiting OS, and to investigate the mechanisms involved. Surface properties of TNTs were characterized, and in vitro and in vivo experiments were conducted to assess their osteoinductive effects under OS. Transcriptomic, proteomic analyses, and Western blotting were performed to investigate the protective mechanisms of TNT110 on osteoblasts. Protein adsorption studies focused on the roles of fibronectin (FN) and albumin (BSA) in modulating osteoblast behavior on TNT110. In both in vitro and in vivo experiments, TNT110 significantly improved new bone formation and supported osteoblast survival under OS conditions. Subsequent ribonucleic acid sequencing results indicated that TNT110 tended to attenuate inflammatory responses and reactive oxygen species (ROS) expression while promoting endoplasmic reticulum (ER) stress and extracellular matrix receptor interactions, all of which are crucial for osteoblast survival and functionality. Further confirmation indicated that the cellular behavior changes of osteoblasts in the TNT110 group could only occur in the presence of serum. Moreover, proteomic analysis under OS conditions revealed the pivotal roles of FN and BSA in augmenting TNT110's resistance to OS. Surface pretreatment of TNT110 with FN/BSA alone could beneficially influence the early adhesion, spreading, ER activity, and ROS expression of osteoblasts, a trend not observed with TNT30. TNT110 effectively protects osteoblast function in the OS microenvironment by modulating protein adsorption, with FN and BSA synergistically enhancing osteogenesis. These findings suggest TNT110's potential for use in implants for elderly patients.

On the influence of structural and chemical properties on the elastic modulus of woven bone under healing.

Woven bone, a heterogeneous and temporary tissue in bone regeneration, is remodeled by osteoblastic and osteoclastic activity and shaped by mechanical stress to restore healthy tissue properties. Characterizing this tissue at different length scales is crucial for developing micromechanical models that optimize mechanical parameters, thereby controlling regeneration and preventing non-unions. This study examines the temporal evolution of the mechanical properties of bone distraction callus using nanoindentation, ash analysis, micro-CT for trabecular microarchitecture, and Raman spectroscopy for mineral quality. It also establishes single- and two-parameter power laws based on experimental data to predict tissue-level and bulk mechanical properties. At the macro-scale, the tissue exhibited a considerable increase in bone fraction, controlled by the widening of trabeculae. The Raman mineral-to-matrix ratios increased to cortical levels during regeneration, but the local elastic modulus remained lower. During healing, the tissue underwent changes in ash fraction and in the percentages of Calcium and Phosphorus. Six statistically significant power laws were identified based on the ash fraction, bone fraction, and chemical and Raman parameters. The microarchitecture of woven bone plays a more significant role than its chemical composition in determining the apparent elastic modulus of the tissue. Raman parameters were demonstrated to provide more significant power laws correlations with the micro-scale elastic modulus than mineral content from ash analysis.

Cellular senescence by loss of Men1 in osteoblasts is critical for age-related osteoporosis.

Recent evidence suggests an association between age-related osteoporosis and cellular senescence in the bone; however, the specific bone cells that play a critical role in age-related osteoporosis and the mechanism remain unknown. Results revealed that age-related osteoporosis is characterized by the loss of osteoblast Men1. Osteoblast-specific inducible knockout of Men1 caused structural changes in the mice bones, matching the phenotypes in patients with age-related osteoporosis. Histomorphometrically, Men1-knockout mice femurs decreased osteoblastic activity and increased osteoclastic activity, hallmarks of age-related osteoporosis. Loss of Men1 induces cellular senescence via mTORC1 activation and AMPK suppression, rescued by metformin treatment. In bone morphogenetic protein-indued bone model, loss of Men1 leads to accumulation of senescent cells and osteoporotic bone formation, which are ameliorated by metformin. Our results indicate that cellular senescence in osteoblasts plays a critical role in age-related osteoporosis and that osteoblast-specific inducible Men1-knockout mice offer a promising model for developing therapeutics for age-related osteoporosis.

Inactivation of spermine synthase in mice causes osteopenia due to reduced osteoblast activity.

Spermine synthase, encoded by the SMS gene, is involved in polyamine metabolism, as it is required for the synthesis of spermine from its precursor molecule spermidine. Pathogenic variants of SMS are known to cause Snyder-Robinson syndrome (SRS), an X-linked recessive disorder causing various symptoms, including intellectual disability, muscular hypotonia, infertility, but also skeletal abnormalities, such as facial dysmorphisms and osteoporosis. Since the impact of a murine SMS deficiency has so far only been analysed in Gy mice, where a large genomic deletion also includes the neighbouring Phex gene, there is only limited knowledge about the potential role of SMS in bone cell regulation. In the present manuscript we describe two patients carrying distinct SMS variants, both diagnosed with osteoporosis. Whereas the first patient displayed all characteristic hallmarks of SRS, the second patient was initially diagnosed, based on laboratory findings, as a case of adult-onset hypophosphatasia. In order to study the impact of SMS inactivation on bone remodelling we took advantage of a newly developed mouse model carrying a pathogenic SMS variant (p.G56S). Compared to their wildtype littermates 12-week-old male SmsG56S/0 mice displayed reduced trabecular bone mass and cortical thickness, as assessed by μCT analysis of the femur. This phenotype was histologically confirmed by the analysis of spine and tibia sections, where we also observed a moderate enrichment of non-mineralized osteoid in SmsG56S/0 mice. Cellular and dynamic histomorphometry further identified a reduced bone formation rate as a main cause of the low bone mass phenotype. Likewise, primary bone marrow cells from SmsG56S/0 mice displayed reduced capacity to form a mineralized matrix ex vivo, thereby suggesting a cell-autonomous mechanism. Taken together, our data identify SMS as an enzyme with physiological relevance for osteoblast activity, thereby demonstrating an important role of polyamine metabolism in the control of bone remodeling.

Increased bone mass but delayed mineralization: in vivo and in vitro study for zoledronate in bone regeneration

BackgroundBisphosphonates (BPs) are widely used to inhibit excessive osteoclast activity. However, the potential to compromise bone defect healing has limited their broader application. To better understand the influence of BPs on bone regeneration, we established a bone grafting model with Zoledronate administration, aiming to deepen the understanding of bone remodeling and mineralization processes.MethodsA bone grafting model was established in the distal femurs of male Sprague–Dawley rats. The experimental group received systemic administration of Zoledronate (ZOL, 0.2 mg/kg, administered twice). Histological analysis and immunohistochemistry (IHC) were employed to assess osteoblastic and macrophage activity, tartrate-resistant acid phosphatase (TRAP) staining was used to evaluate osteoclastogenesis. Mineralization was assessed through Micro-CT analysis, Raman spectroscopy, and back-scatter scanning electron microscopy (BSE-SEM). Additionally, the in vitro effects of ZOL on osteoblast and osteoclast activity were investigated to further elucidate its impact on bone regeneration.ResultsIn vivo, the ZOL group showed increased bone mass, as observed in histological and radiological assessments. However, Micro-CT, Raman spectroscopy, and BSE-SEM detection revealed lower mineralization levels in ZOL group's regenerated bone. Acid-etched SEM analysis showed abnormal osteocyte characteristics in ZOL-group’s regenerated bone. Simultaneously, elevated osteopontin (OPN), F4/80 expression along with reduced TRAP expressing was found in the grafting region of ZOL group. In vitro, ZOL did not negatively impact osteogenetic activity (ALP, BMP4, OCN expression) at the tested concentrations (0.02–0.5 g/ml) but significantly impaired mineralization and inhibited osteoclast formation, even at the lowest concentration.ConclusionsThis study highlights a less recognized negative effect of ZOL on bone mineralization during bone regeneration. More research is needed to elucidate the underlying mechanism.

Polarization of Lanthanum-Doped HA and Barium Calcium Titanate (BCT) Composites Exhibit Enhanced Osteoblast Activities and Antibacterial Properties

Polarization of Lanthanum-Doped HA and Barium Calcium Titanate (BCT) Composites Exhibit Enhanced Osteoblast Activities and Antibacterial Properties

The Effect of Corticotomy-Assisted Orthodontic Therapy (CAOT) or Periodontally Accelerated Osteogenic Orthodontics (PAOO) on Bone Remodeling and the Health of Periodontium: A Systematic Review of Systematic Reviews.

Background: Orthodontic treatment involves moving teeth within the alveolar ridge. Bone remodeling is associated with the activity of osteoblasts and osteoclasts. Procedures such as corticotomy-assisted orthodontic therapy (CAOT) or periodontally accelerated osteogenic orthodontics (PAOO) are intended to reduce bone density and negative stress on the grip side and therefore limit bone resorption during orthodontic movement or add bone substitute material so that the tooth does not cross the vestibular plate. Methods: The study was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The study design was defined in the PICO format-Population (P): patients with full permanent dentition, both adolescents and adults; Intervention (I): orthodontic treatment with fixed appliances using additional supportive treatments such as CAOT or PAOO; Comparison (C): assessment of the impact of additional treatments during orthodontic treatment on the remodeling of the alveolar bone and the condition of the periodontium; Result (O): statistically significant/non-significant differences in the condition of the alveolar bone before and after orthodontic treatment. Search filters include the time of publication of the article, systematic reviews from the last five years, and publications that appeared in English. The information provided in the abstracts of systematic reviews that describe the effects of additional procedures during orthodontic treatment such as CAOT or PAOO on the health of periodontium was analyzed. Articles unrelated to the subject of the planned study and those in which tooth movement acceleration was analyzed were excluded. Results: Eight articles were selected in which a total number of 835 subjects took part. The changes in bone density and effects on periodontium were different after CAOT and PAOO. Conclusions: The validity of CAOT and PAOO procedures remains controversial. Better results are obtained when combined with tissue augmentation or thickening of the gingival phenotype rather than as stand-alone procedures, as their uses to protect periodontal tissues are limited.

Wnt7b overexpression in osteoblasts stimulates bone formation and reduces obesity in mice on a high-fat diet.

Previous studies have shown that Wnt7b potently stimulates bone formation by promoting osteoblast differentiation and activity. As high-fat feeding leads to obesity and systemic metabolic dysregulation, here we investigate the potential benefit of Wnt7b overexpression in osteoblasts on both bone and whole-body metabolism in mice fed with a high-fat diet (HFD). Wnt7b overexpression elicited massive overgrowth of trabecular and cortical bone but seemed to ameliorate body fat accumulation in mice with prolonged HFD feeding. In addition, Wnt7b overexpression modestly improved glucose tolerance in male mice on HFD. Collectively, the results indicate that targeted overexpression of Wnt7b in osteoblasts not only stimulates bone formation but also improves certain aspects of global metabolism in overnourished mice.

Reversal of Bone Mineral Density Loss Through Lifestyle Changes: A Case Report.

Approximately 10 million individuals in the United States have osteoporosis and 44 million have low bone mineral density which puts them at risk for bone breaks. This presents a large burden on our health care system since about one-quarter of hip fracture patients never regain full function, need nursing care, and, for those over age 50, 24% die within one year. Oral bisphosphonates are often used as first-line therapy for the treatment of osteoporosis; however, patients frequently experience significant side effects. In addition, bisphosphonates inhibit bone loss by initiating apoptosis in osteoclasts that remove old bone, thus allowing old bone to accumulate and slowing the activity of osteoblasts that create new bone, thereby affecting bone quality. As an alternative, a bone-friendly lifestyle, including calcium and vitamin D consumption, exercise, smoking cessation, and a decrease in alcohol intake, may reduce bone loss. This case report describes lifestyle changes that included diet and exercise that increased bone mineral density in two years in a post-menopausal woman with no negative side effects.

Serum Vitamin D and Osteocalcin for Assessment of Bone Mineral Metabolism: A Comparison of Children with Steroid-Sensitive and Resistant Nephrotic Syndrome

Background Long-term corticosteroid use decreases osteoblastic activity and bone matrix formation. Osteocalcin (OC), a marker of bone turnover, is more sensitive than alkaline phosphatase in indicating bone matrix synthesis. Materials and Methods The cross-sectional study was done from January to September 2021; a total of 62 (40 males, 22 females) children (2–18 years) with nephrotic syndrome in disease remission were enrolled. Thirty-two had steroid-sensitive nephrotic syndrome (SSNS), and 30 had steroid-resistant nephrotic syndrome (SRNS). Children who had received daily steroids or high doses of vitamin D within the previous three months were excluded. The primary objective of this study was to assess bone mineral metabolism by measuring vitamin D, parathyroid hormone (PTH), and osteocalcin levels. Results In children with SSNS, 46.8% had vitamin D insufficiency, 21.9% vitamin D deficiency, and median vitamin D levels were 28.4 ng/mL; in the SRNS group, 40% had insufficiency, 33.4% deficiency, and vitamin D levels were 26.6 ng/mL. The median steroid dose used in the previous 6 months was significantly higher in the SRNS patients, 0.63 (0.35, 0.77) mg/kg on alternate days compared to SSNS, 0.50 (0.32, 0.60) mg/kg (p = 0.02). Median serum OC levels were lower in SRNS 20.4 (10.8, 33.5) ng/mL compared to SSNS, 35.6 (22.5, 42.7) ng/mL (p = 0.004). Conclusion Bone metabolism is negatively affected in children with nephrotic syndrome, especially in those with SRNS and must continue to be vitamin D insufficient despite routine supplementation; serum OC appears to be a promising marker for this evaluation.

Role of ginsenosides in bone remodelling: A narrative review on molecular mechanism

Osteoporosis (OP) is a metabolic bone disease that impacts a large number of humanity. Degeneration of the bone microstructure, loss of mass, and heightened fragility are symptoms. The primary reason is because the rates of bone formation and resorption are different. Extensive research on the effects of ginsenoside, a component of ginseng used in traditional Indian medicine, on osteoporosis has shown promising results. There were forty-four articles written about ginsenosides, osteoblasts, osteoclasts, osteoporosis, and bone mesenchymal cells. The effects of ginsenosides on osteoblast, osteoclast, and mesenchymal stem cell activity in bone remodelling and their potential role in preventing osteoporosis were the focus of these studies. This in-depth study sheds light on the several ginsenosides used to treat osteoporosis from different perspectives, paving the way for potential therapeutic applications in the future.

CD11B + CD36 + cells are bone anabolic macrophages that limit age-associated bone loss.

Disruptions in the bone remodeling cycle that occur with increasing age lead to degeneration of the skeleton and increased risk of fragility fractures. Our understanding of how the bone remodeling process within cortical bone is controlled and altered with age in males and females is limited. Here, we generated bone marrow chimeric mice to understand the impacts of age and sex on the bone remodeling process. We demonstrate that transplantation of aged male or female bone marrow into young lethally irradiated male hosts unexpectedly enhances cortical bone mass without an impacting cancellous bone. Our single cell RNA-sequencing data show that mice reconstituted with aged bone marrow exhibited subsets of cells marked by CD11B/CD36 expression that demonstrate enhanced production of anabolic cytokines as compared to young counterparts, and that these myeloid subsets exist under conditions of normal physiology in aged mice. Importantly, CD11B + CD36 + cells do not differentiate into osteoclasts in vitro, and CD36 does not mark TRAP+ cells in vivo. Instead, CD36 + cells localize to resorption sites, including within cortical bone defects, suggesting their involvement in cortical bone remodeling and healing. CD11B + CD36 + cells also express elevated levels of bone anabolic WNT ligands, especially Wnt6. In functional assays, we demonstrate that soluble factors produced by CD11B + CD36 + cells enhance osteoblast progenitor commitment, mineralization, and activation of WNT signaling in vitro. Moreover, CD11B/CD36 exquisitely mark a subset of anabolic myeloid cells within human bone marrow. In conclusion, our studies identified a novel population of aged macrophages that limit cortical bone loss.

PET/CT for the Opportunistic Screening of Osteoporosis and Fractures in Cancer Patients.

In this review, we outline the different etiologies of osteoporosis in the oncologic setting and describe the basis for using PET/CT as screening tool for osteoporosis with a focus on the radiotracers [18F]FDG and [18F]NaF. Osteoporosis is a condition commonly affecting cancer patients due to their age, cancer-specific treatment agents, and effects of cancer. In terms of the unifying mechanism, decreased ratio of osteoblast-bone formation to osteoclast-bone resorption is responsible for causing osteoporosis. PET/CT, a crucial metabolic imaging modality in the oncologic imaging, could be a useful tool for the opportunistic screening of osteoporosis. There are two approaches with which osteoporosis could be identified with PET/CT-using either the (1) CT- based or (2) PET- based approaches. While the CT-based approach has been used with [18F]FDG PET/CT, both CT- and PET-based approaches can be employed with [18F]NaF-PET/CT as [18F]NaF is a radiotracer specific for osteoblast activity.

Peptides as modulators of FPPS enzyme: A multifaceted evaluation from the design to the mechanism of action

Bone diseases are medical conditions caused by the loss of bone homeostasis consecutive to increased osteoclast activity and diminished osteoblast activity. The mevalonate pathway (MVA) is crucial for maintaining this balance since it drives the post-translational prenylation of small guanosine triphosphatases (GTPases) proteins. Farnesyl pyrophosphate synthase (FPPS) plays a crucial role in the MVA pathway. Consequently, in the treatment of bone-related diseases, FPPS is the target of FDA-approved nitrogen-containing bisphosphonates (N-BPs), which have tropism mainly for bone tissue due to their poor penetration in soft tissues. The development of inhibitors targeting the FPPS enzyme has garnered significant interest in recent decades due to FPPS's role in the biosynthesis of cholesterol and other isoprenoids, which are implicated in cancer, bone diseases, and other conditions. In this study, we describe a multidisciplinary approach to designing novel FPPS inhibitors, combining computational modeling, biochemical assays, and biophysical techniques. A series of peptides and phosphopeptides were designed, synthesized, and evaluated for their ability to inhibit FPPS activity. Molecular docking was employed to predict the binding modes of these compounds to FPPS, while Surface Plasmon Resonance (SPR) and Nuclear Magnetic Resonance (NMR) spectroscopy experiments – based on Saturation Transfer Difference (STD) and an enzymatic NMR assay – were used to measure their binding affinities and kinetics. The biological activity of the most promising compounds was further assessed in cellular assays using murine colorectal cancer (CRC) cells. Additionally, genomics and metabolomics profiling allowed to unravel the possible mechanisms underlying the activity of the peptides, confirming their involvement in the modulation of the MVA pathway. Our findings demonstrate that the designed peptides and phosphopeptides exhibit significant inhibitory activity against FPPS and possess antiproliferative effects on CRC cells, suggesting their potential as therapeutic agents for cancer.

REVITALIZATION OF CRITICAL-SIZED CALVARIAL DEFECTS IN RATS USING HEPARIN-CONJUGATED FIBRIN HYDROGEL WITH BMP-2 AND ADIPOSE-DERIVED PERICYTES

Massive bone defects present challenges in orthopedic surgery, requiring innovative solutions. Hydrogels offer promise due to their resemblance to the extracellular matrix. Adipose tissue-derived pericytes (ADPs) and osteoinductive proteins like BMP-2 show potential for bone tissue engineering. Combining them via heparin-conjugated fibrin hydrogel aims to enhance healing in critical-sized calvarial defects. The study investigated the use of a heparin-conjugated fibrin (HCF) hydrogel containing BMP-2 and adipose-derived pericytes for repairing critical-sized calvarial defects in rats. ADPs were cultured from rat adipose tissue, and the HCF hydrogel was prepared accordingly. In vitro experiments assessed BMP-2 release kinetics and bioactivity, while mineralization assays were conducted on cultured ADPs. In vivo experiments involved surgically creating calvarial defects in rats and implanting HCF gel alone or with BMP-2, pericytes, or both. Micro-CT imaging and histological analysis were performed post-implantation to evaluate bone formation. In our study, we prepared the HCF hydrogel by combining heparin-conjugated fibrinogen, human fibrinogen, human thrombin, aprotinin, and calcium chloride. Gelation occurred within 3 minutes at room temperature. SEM analysis revealed an open interconnected pore morphology and macroporous structure, facilitating cell attachment and proliferation. ELISA showed sustained release of BMP-2 from the HCF hydrogel over 28 days. Bioactivity assays demonstrated the ability of released BMP-2 to enhance ALP activity in rat neonatal calvarial osteoblasts. Additionally, BMP-2 induced osteogenic differentiation of rat ADPs, as evidenced by increased ALP activity, osteocalcin expression, and calcium deposition. Implantation of HCF hydrogels containing BMP-2 and/or ADPs into rat calvarial defects significantly promoted bone tissue regeneration compared to controls, with the greatest effect observed in the group receiving both BMP-2 and ADPs. Micro-CT and histological analysis confirmed substantial bone formation and defect closure after three months. In conclusion, our in vitro findings demonstrated that the HCF hydrogel provided sustained release of BMP-2, retaining its bioactivity and promoting osteogenesis in rat calvarial osteoblasts and ADPs. In vivo results showed that combining allogeneic ADPs with BMP-2 enhanced bone regeneration in critical-sized calvarial defects, indicating the potential of this approach for large bone defect restoration.