Zinc Promotes Osteoblast Differentiation in Human Mesenchymal Stem Cells Via Activation of the cAMP-PKA-CREB Signaling Pathway

Enhanced functionalities of biomaterials through metal ion surface modification

The development of new artificial biomaterials for bone defect repair is an ongoing area of clinical research. Metal ions such as zinc, copper, magnesium, calcium, strontium, silver, and cerium play various roles in bone tissue regeneration in the human body and possess a range of biochemical functions. Studies have demonstrated that appropriate concentrations of these metal ions can promote osteogenesis and angiogenesis, inhibit osteoclast activity, and deter bacterial infections. Researchers have incorporated metal ions into biomaterials using various methods to create artificial bone materials with enhanced osteogenic and antibacterial capabilities. In addition to the osteogenic properties of all the aforementioned metal ions, Zn, Sr, and Ce can indirectly promote osteogenesis by inhibiting osteoclast activity. Cu, Mg, and Sr significantly enhance angiogenesis, while the antibacterial properties of Zn, Cu, Ag, and Ce can reduce the likelihood of infection and inflammation caused by implanted materials. This paper reviews the mechanisms through which metal ions promote bone tissue growth and improve the antibacterial activity of biomaterials. It also summarizes common loading methods on the surface of biomaterials with different metals and highlights the potential clinical applications of these new artificial bone materials.

Impact of Strontium, Magnesium, and Zinc Ions on the In Vitro Osteogenesis of Maxillary Sinus Membrane Stem Cells

Human Maxillary Sinus Membrane Stem Cells (hMSMSCs) contribute significantly to bone formation following maxillary sinus floor augmentation (MSFA). The biological behavior of mesenchymal stem cells is notably influenced by varying concentrations of magnesium (Mg2+), strontium (Sr2+), and zinc (Zn2+) ions; however, their specific effects on hMSMSCs have not been comprehensively studied. We isolated hMSMSCs and identified their mesenchymal stem cell characteristics by flow cytometry and multilineage differentiation experiments. Subsequently, the hMSMSCs were cultured in media containing different concentrations of these metal ions. The proliferation and viability of hMSMSCs were assessed using CCK-8 and Calcein AM/PI staining. After osteogenic induction, cells were evaluated for alkaline phosphatase (ALP) activity, ALP staining, and Alizarin Red staining. Additionally, qRT-PCR was used to detect differences in osteogenic gene expression, and immunofluorescence staining was used to observe variations in OCN protein levels. The results indicated that 1 mM Mg2+, 0.01 mM Sr2+, and 0.001 mM Zn2+ significantly improved the proliferation and activity of hMSMSCs. These concentrations also notably enhanced ALP secretion, increased bone-related gene expression, and augmented osteocalcin expression and formation of extracellular calcium nodules, thereby improving osteogenic differentiation. However, higher concentrations of Mg2+, Sr2+, and Zn2+ decreased cell viability and osteogenic differentiation. Mg2+, Sr2+, and Zn2+ promote osteogenic differentiation and proliferation of hMSMSCs in a concentration-dependent manner, indicating that the type and concentration of ions in the extracellular environment can significantly alter hMSMSCs behavior, which is a crucial consideration for material design in maxillary sinus elevation applications.

The Skin-to-Mucosa Ratio Defines the Osteogenic Potential of Lip Fibroblasts

Fibroblasts isolated from discarded lip tissue obtained during cheiloplasty in patients with cleft lip/palate (CLP) show promising osteogenic potential and may be an appealing cell source for autologous bone regeneration. As the lip is a mucocutaneous junction, explant cultures from unseparated lip biopsies produce mesenchymal outgrowths composed of skin- and mucosa-derived fibroblasts. The proportions of the 2 fibroblast populations, however, differ among CLP patients and depend on the morphology of the excised sample, which is unique for each donor. Understanding the osteogenic activities of CLP fibroblast populations with varying skin-to-mucosa ratios is critical for their therapeutic application. We isolated CLP fibroblasts from 10 unseparated lip biopsies and comprehensively evaluated them for their bone differentiation capacities in vitro, demonstrating heterogeneous osteogenic potentials. Because there are no markers that can distinguish skin from mucosa fibroblasts, we used the respective and matching CLP keratinocytes to ascertain the skin-to-mucosa ratio of the 10 specimens. Thus, we found that CLP fibroblasts isolated from biopsies with high skin-to-mucosa ratios had a much higher osteogenic capacity than those derived from biopsies with low skin-to-mucosa ratios. To validate and solidify these findings, we carefully separated skin and mucosa tissues during corrective lip surgery to isolate pure skin and mucosa CLP lip fibroblasts. Indeed, skin had a higher osteogenic potential than their mucosal counterparts did. Furthermore, we discovered that the high osteogenic activity in skin was limited to specific subpopulations of yet unknown identities. Our findings indicate that skin fibroblasts perform better than their mucosal counterparts do, even though both types of fibroblasts can differentiate into bone-forming cells.

Advances in the application and research of biomaterials in promoting bone repair and regeneration through immune modulation

With the ongoing development of osteoimmunology, increasing evidence indicates that the local immune microenvironment plays a critical role in various stages of bone formation. Consequently, modulating the immune inflammatory response triggered by biomaterials to foster a more favorable immune microenvironment for bone regeneration has emerged as a novel strategy in bone tissue engineering. This review first examines the roles of various immune cells in bone tissue injury and repair. Then, the contributions of different biomaterials, including metals, bioceramics, and polymers, in promoting osteogenesis through immune regulation, as well as their future development directions, are discussed. Finally, various design strategies, such as modifying the physicochemical properties of biomaterials and integrating bioactive substances, to optimize material design and create an immune environment conducive to bone formation, are explored. In summary, this review comprehensively covers strategies and approaches for promoting bone tissue regeneration through immune modulation. It offers a thorough understanding of current research trends in biomaterial-based immune regulation, serving as a theoretical reference for the further development and clinical application of biomaterials in bone tissue engineering.

Potential of Liposomal FTY720 for Bone Regeneration: Proliferative, Osteoinductive, Chemoattractive, and Angiogenic Properties Compared to Free Bioactive Lipid

Introduction

FTY720 bioactive lipid has proliferative, osteoinductive, chemo attractive, and angiogenic properties, being thus a potential exogenous administered agent for promotion of bone regeneration. Herein we developed FTY720-loaded liposomes as a potential delivery system that could retain and prolong the bioactivity of the bioactive lipid and at the same time reduce its cytotoxicity (at high doses).

Methods

FTY720 liposomes were prepared by thin-lipid hydration and microfluidic flow focusing, and evaluated for their ability to induce proliferation, osteoinduction, and chemoattraction in three cell types: MC3T3-E1 pre-osteoblast cells, L929 fibroblast cells, and ATDC5 chondrogenic cells. The angiogenic activity of free and liposomal FTY720 was investigated using a chick chorioallantoic membrane assay. NBD-FTY720 cellular uptake was quantitated using flow cytometry and morphologically assessed by confocal microscopy. Implicated cellular signaling mechanisms were investigated by quantifying phosphorylated MAPK and CREB proteins.

Results

FTY720 liposomes (~80-110 nm) with low polydispersity and ~100% loading were prepared using both methods. FTY720 demonstrated the ability to increase cell proliferation at 10-300nM doses but was cytotoxic at doses>400nM while the corresponding liposomal-FTY720 doses were non-cytotoxic, proving its reduced toxicity. In several cases (cells and doses), FTY720 liposomes demonstrated increased osteogenic differentiation of cells, proliferation, and migration compared to free FTY720, whereas both FTY720 forms demonstrated substantial angiogenic activity. Liposomal FTY720 cellular uptake was substantially higher than that of free FTY720 in some cases, a fact that may be connected to its higher bioactivity. Increased phosphorylated MAPK and CREB protein concentrations provided information about the potential cellular signaling mechanisms involved in FTY720-induced osteogenesis.

Discussion

The current results confirm the high potential of FTY720 bioactive lipid, especially in its liposomal form, that demonstrated substantial reduction of cytotoxicity and prolonged preservation of the lipids bioactivity (compared to the free lipid), for accelerated treatment of bone defects. Interestingly, the current studies prove the potential of FTY720, especially in its liposomal form, to promote reprogramming of L929 fibroblasts into osteoblasts, a novel finding deserving future exploitation.

Additively Manufactured Biodegradable Zn-Based Porous Scaffolds to Suppress Osteosarcoma and Promote Osteogenesis

Postoperative therapies for osteosarcoma present substantial challenges due to tumor recurrence and extensive bone defects. To tackle these challenges, laser powder bed fusion is utilized to fabricate biodegradable Zn-Li porous scaffolds that supress tumors and promote osteogenesis. After the structure design and composition selection, the Zn-0.8Li porous scaffold with Gyroid unit optimally balances the co-release of Zn2+ and Li+ during degradation, resulting in favorable antitumor and osteogenic effects. In vitro, the Zn-0.8Li scaffold significantly inhibits osteosarcoma progression by suppressing tumor cell proliferation, promoting apoptosis, alleviating migration, and simultaneously promotes osteogenic differentiation through the enhanced expression of osteogenic markers. In vivo, the Zn-0.8Li scaffold inhibits the malignant osteosarcoma behavior and facilitates bone regeneration in areas with bone defects. Transcriptomic analysis further reveals that the simultaneous release of Zn2+ and Li+ from the biodegradable Zn-0.8Li scaffold contributes to anti-osteosarcoma activity by downregulating PI3K/Akt signaling pathways. Taken together, the Zn-0.8Li porous scaffold fabricated using laser powder bed fusion with enhanced antitumor and osteogenic properties is a promising alternative for the postoperative management of osteosarcoma.

Metabolically activated energetic materials mediate cellular anabolism for bone regeneration

The understanding of cellular energy metabolism activation by engineered scaffolds remains limited, posing challenges for therapeutic applications in tissue regeneration. This study presents biosynthesized poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] and its major degradation product, 3-hydroxybutyrate (3HB), as endogenous bioenergetic fuels that augment cellular anabolism, thereby facilitating the progression of human bone marrow-derived mesenchymal stem cells (hBMSCs) towards osteoblastogenesis. Our research demonstrated that 3HB markedly boosts in vitro ATP production, elevating mitochondrial membrane potential and capillary-like tube formation. Additionally, it raises citrate levels in the tricarboxylic acid (TCA) cycle, facilitating the synthesis of citrate-containing apatite during hBMSCs osteogenesis. Furthermore, 3HB administration significantly increased bone mass in rats with osteoporosis induced by ovariectomy. The findings also showed that P(3HB-co-4HB) scaffold substantially enhances long-term vascularized bone regeneration in rat cranial defect models. These findings reveal a previously unknown role of 3HB in promoting osteogenesis of hBMSCs and highlight the metabolic activation of P(3HB-co-4HB) scaffold for bone regeneration.

Zinc Ameliorates High Pi and Ca-Mediated Osteogenic Differentiation of Mesenchymal Stem Cells

Zinc is the second most abundant trace element in the human body, stored mainly in the bones. Zinc is required for bone growth and homeostasis and is also a crucial cofactor for numerous proteins that play key roles in maintaining microstructural integrity and bone remodeling. Bone marrow-derived mesenchymal stem cells (BMSCs) are multipotent progenitors found in the bone marrow stroma and can differentiate along multiple lineage pathways. In this study, we investigated the effect of zinc on the osteogenic differentiation of BMSCs. We stimulated the osteogenic differentiation of BMSCs with high phosphate and Ca-containing osteogenic medium (PiCa) in the presence or absence of zinc. We followed calcification by measuring ECM mineralization, the Ca content of the ECM, mRNA, and the protein expression of the osteo-chondrogenic transcription factor RUNX2 and SOX9 and its targets OCN and ALP. Zinc dose-dependently abolished PiCa-induced ECM mineralization and decreased the expression of RUNX2, SOX9, OCN, and ALP. Serum albumin did not alter the inhibitory effect of zinc on BMSC mineralization. Our further analysis with the zinc-chelator TPEN and ZnCl2 confirmed the specific inhibitory effect of free zinc ions on BMSC mineralization. Zinc inhibited phosphate uptake and PiCa-induced upregulation of the sodium-dependent phosphate cotransporters (PiT-1 and PiT-2). Zinc attenuated the PiCa-induced increase in ROS production. Taken together, these data suggest that zinc inhibits PiCa-induced BMSC calcification by regulating phosphate uptake and ROS production.

Multifunctional Bionic Periosteum with Ion Sustained-Release for Bone Regeneration

In this study, a novel bionic periosteum (BP)-bioactive glass fiber membrane (BGFM) is designed. The introduction of magnesium ion (Mg2+) and zinc ion (Zn2+) change the phase separation during the electrospinning (ES) jet stretching process. The fiber's pore structure transitions from connected to closed pores, resulting in a decrease in the rapid release of metal ions while also improving degradation via reducing filling quality. Additionally, the introduction of magnesium (Mg) and zinc (Zn) lead to the formation of negative charged tetrahedral units (MgO4 2- and ZnO4 2-) in the glass network. These units effectively trap positive charged metal ions, further inhibiting ion release. In vitro experiments reveal that the deigned bionic periosteum regulates the polarization of macrophages toward M2 type, thereby establishing a conducive immune environment for osteogenic differentiation. Bioinformatics analysis indicate that BP enhanced bone repair via the JAK-STAT signaling pathway. The slow release of metal ions from the bionic periosteum can directly enhance osteogenic differentiation and vascularization, thereby accelerating bone regeneration. Finally, the bionic periosteum exhibits remarkable capabilities in angiogenesis and osteogenesis, demonstrating its potential for bone repair in a rat calvarial defect model.

Nanoparticle-Enabled Zn-0.1Mg Alloy with Long-Term Stability, Refined Degradation, and Favorable Biocompatibility for Biodegradable Implant Devices

Zinc-based alloys, specifically Zn-Mg, have garnered considerable attention as promising materials for biodegradable implants due to their favorable mechanical strength, appropriate corrosion rate, and biocompatibility. Nevertheless, the alloy's lack of mechanical stability and integrity, resulting from ductility loss induced by age hardening at room temperature, hampers its practical bioapplication. In this study, ceramic nanoparticles have been successfully incorporated into the Zn-Mg alloy system, leading to a significant improvement in long-term stability as well as mechanical strength and ductility. In addition, this study represents the first investigation of Zn-based nanocomposites both in vitro and in vivo to comprehend the influence of nanoparticles on the degradation behavior and biocompatibility of the Zn system. The findings indicate that the incorporation of WC nanoparticles effectively refines and stabilizes the degradation behavior of Zn-Mg without negatively impacting the cytocompatibility of the alloy. The subcutaneous implantation and femoral implantation further prove the benefits of nanoparticle incorporation and found no negative effects. Collectively, Zn-Mg-WC nanocomposites yield great potential for implant usage.

Impact of Metal Ions on Cellular Functions: A Focus on Mesenchymal Stem/Stromal Cell Differentiation

Metals play a crucial role in the human body, especially as ions in metalloproteins. Essential metals, such as calcium, iron, and zinc are crucial for various physiological functions, but their interactions within biological networks are complex and not fully understood. Mesenchymal stem/stromal cells (MSCs) are essential for tissue regeneration due to their ability to differentiate into various cell types. This review article addresses the effects of physiological and unphysiological, but not directly toxic, metal ion concentrations, particularly concerning MSCs. Overloading or unbalancing of metal ion concentrations can significantly impair the function and differentiation capacity of MSCs. In addition, excessive or unbalanced metal ion concentrations can lead to oxidative stress, which can affect viability or inflammation. Data on the effects of metal ions on MSC differentiation are limited and often contradictory. Future research should, therefore, aim to clarify the mechanisms by which metal ions affect MSC differentiation, focusing on aspects such as metal ion interactions, ion concentrations, exposure duration, and other environmental conditions. Understanding these interactions could ultimately improve the design of biomaterials and implants to promote MSC-mediated tissue regeneration. It could also lead to the development of innovative therapeutic strategies in regenerative medicine.

Si and Zn dual ions upregulate the osteogenic differentiation of mBMSCs: mRNA transcriptomic sequencing analysis

Both silicon (Si) and zinc (Zn) ions are essential elements to bone health and their mechanisms for promoting osteogenesis have aroused the extensive attention of researchers. Thereinto, the mechanism by which dual ions promote osteogenic differentiation remains to be elucidated. Herein, the effects of Si and Zn ions on the cytological behaviors of mBMSCs were firstly studied. Then, the molecular mechanism of Si-Zn dual ions regulating the osteogenic differentiation of mBMSCs was investigated via transcriptome sequencing technology. In the single-ion system, Si ion at the concentration of 1.5 mM (Si-1.5) had better comprehensive effects of cell proliferation, ALP activity and osteogenesis-related gene expression levels (ALP, Runx2, OCN, Col-I and BSP); Zn ion at the concentration of 50 μM (Zn-50) demonstrated better combining effects of cell proliferation, ALP activity and same osteogenic genes expression levels. In the dual-ion system, the Si (1.5 mM)-Zn (50 μM) group (Si1.5-Zn50) synthetically enhanced ALP activity and osteogenesis genes compared with single-ion groups. Analysis of the transcriptome sequencing results showed that Si ion had a certain effect on promoting the osteogenic differentiation of mBMSCs; Zn ion had a stronger effect of contributing to a better osteogenic differentiation of mBMSCs than that of Si ion; the Si-Zn dual ions had a synergistic enhancement on conducting to the osteogenic differentiation of mBMSCs compared to single ion (Si or Zn). This study offers a blueprint for exploring the regulation mechanism of osteogenic differentiation by dual ions.

Surface Functionalization of 3D-Printed Scaffolds with Seed-Assisted Hydrothermally Grown ZnO Nanoarrays for Bone Tissue Engineering

Bioactive metal-based nanostructures, particularly zinc oxide (ZnO), are promising materials for bone tissue engineering. However, integrating them into 3D-printed polymers using traditional blending methods reduces the cell performance. Alternative surface deposition techniques often require extreme conditions that are unsuitable for polymers. To address these issues, we propose a metal-assisted hydrothermal synthesis method to modify 3D printed polycaprolactone (PCL) scaffolds with ZnO nanoparticles (NPs), facilitating the growth of ZnO nanoarrays (NAs) at a low-temperature (55 °C). Physicochemical characterizations revealed that the ZnO NPs form both physical and chemical bonds with the PCL surface; chemical bonding occurs between the carboxylate groups of PCL and Zn(OH)2 during seed deposition and hydrothermal synthesis. The ZnO NPs and NAs grown for a longer time (18 h) on the surface of PCL scaffolds exhibit significant proliferation and early differentiation of osteoblast-like cells. The proposed method is suitable for the surface modification of thermally degradable polymers, opening up new possibilities for the deposition of diverse metals.

Independent and combined associations of dietary antioxidant intake with bone mineral density and risk of osteoporosis among elderly population in United States

BACKGROUND

The influence of dietary antioxidant intake on the occurrence and progression of osteoporosis may be significant. However, to date, evidence on the link between combined effect of dietary antioxidants on bone mineral density (BMD) level and risk of osteoporosis is limited. We aimed to assess the independent and combined association of dietary antioxidant intake with BMD level and risk of osteoporosis among elderly population in United States through analysis of data in the National Health and Nutrition Examination Survey.

METHODS

The dietary antioxidant intake was assessed based on six antioxidants, including vitamin A, vitamin C, vitamin E, zinc, selenium, and total carotenoid. A composite dietary antioxidant index (CDAI) was used to evaluate the combined exposure of dietary antioxidant intake.

RESULTS

A total of 5618 participants were included. Higher dietary vitamin A, vitamin C, vitamin E, zinc, selenium, and total carotenoid, were positively associated with BMD level. Compared with participants in the first quartile, those in the higher quartile of vitamin E (Q4: OR 0.652; 95% CI 0.463-0.918), zinc (Q4: OR 0.581; 95% CI 0.408-0.826), and selenium (Q3: OR 0.673; 95% CI 0.503-0.899) were associated with decreased risk of overall osteoporosis. Furthermore, compared to those in the first quartile, participants in the highest quartile of CDAI were associated with increased total femur (β 0.019; 95% CI 0.007-0.032), femur neck (β 0.020; 95% CI 0.009-0.032), trochanter (β 0.012; 95% CI 0.001-0.023), and intertrochanter BMD level (β 0.022; 95% CI 0.007-0.037); participants in the highest quartile of CDAI were associated with decreased risk of overall osteoporosis (OR 0.536; 95% CI 0.376-0.763). Furthermore, the associations of CDAI with the BMD level and osteoporosis risk were more significant among female participants.

CONCLUSION

Our study provides evidence that a combination of dietary antioxidants intake was associated increased BMD level and decreased osteoporosis risk.

Efficacy of sintered Zinc-doped fluorapatite scaffold as an antimicrobial regenerative bone filler for dental applications

OBJECTIVES

The objective of this study was to assess whether zinc-doped fluorapatite (ZnFA) could serve as an effective antimicrobial dental bone filler for bone regeneration compared to autografts.

METHODS

FA and 2 % zinc-doped FA (2ZnFA) were synthesized and characterized in-house. Compressed and sintered FA and 2ZnFA disks were incubated with bacteria to assess antimicrobial properties. Adipose-derived stem cells were cultured on these discs to evaluate the surfaces' ability to support cell growth and promote osteogenic differentiation. Surfaces exhibiting the highest expressions of the bone markers osteopontin and osteocalcin were selected for an in vivo study in a rat mandibular defect model. Twenty rats were divided into 5 groups, equally, and a 5 mm surgical defect of the jaw was left untreated or filled with 2ZnFA, FA, autograft, or demineralized bone matrix (DBM). At 12 weeks, the defects and surrounding tissues were harvested and subjected to microCT and histological evaluations.

RESULTS

Standard techniques such as FTIR, ICP-MS, fluoride probe, and XRD revealed the sintered FA and ZnFA's chemical compositions and structures. Bacterial studies revealed no significant differences in surface bacterial adhesion properties between FA and 2ZnFA, but significantly fewer bacterial loads than control titanium discs (p < 0.05). Cell culture data confirmed that both surfaces could support cell growth and promote the osteogenic differentiation of stem cells. MicroCT analysis confirmed statistical similarities in bone regeneration within FA, 2ZnFA, and autograft groups.

CONCLUSION

The data suggests that both FA and 2ZnFA could serve as alternatives to autograft materials, which are the current gold standard. Moreover, these bone fillers outperformed DBM, an allograft material commonly used as a dental bone void filler.

CLINICAL SIGNIFICANCE

The use of FA or 2ZnFA for treating mandibular defects led to bone regeneration statistically similar to autograft repair and significantly outperformed the widely used dental bone filler, DBM. Additional translational research may confirm FA-based materials as superior substitutes for existing synthetic bone fillers, ultimately enhancing patient outcomes.

A Zinc Oxide Nanowire-Modified Mineralized Collagen Scaffold Promotes Infectious Bone Regeneration

Bone infection poses a major clinical challenge that can hinder patient recovery and exacerbate postoperative complications. This study has developed a bioactive composite scaffold through the co-assembly and intrafibrillar mineralization of collagen fibrils and zinc oxide (ZnO) nanowires (IMC/ZnO). The IMC/ZnO exhibits bone-like hierarchical structures and enhances capabilities for osteogenesis, antibacterial activity, and bacteria-infected bone healing. During co-cultivation with human bone marrow mesenchymal stem cells (BMMSCs), the IMC/ZnO improves BMMSC adhesion, proliferation, and osteogenic differentiation even under inflammatory conditions. Moreover, it suppresses the activity of Gram-negative Porphyromonas gingivalis and Gram-positive Streptococcus mutans by releasing zinc ions within the acidic infectious microenvironment. In vivo, the IMC/ZnO enables near-complete healing of infected bone defects within the intricate oral bacterial milieu, which is attributed to IMC/ZnO orchestrating M2 macrophage polarization, and fostering an osteogenic and anti-inflammatory microenvironment. Overall, these findings demonstrate the promise of the bioactive scaffold IMC/ZnO for treating bacteria-infected bone defects.

Complex intrinsic abnormalities in osteoblast lineage cells of X-linked hypophosphatemia: Analysis of human iPS cell models generated by CRISPR/Cas9-mediated gene ablation

X-linked hypophosphatemia (XLH) is caused by inactivating variants of the phosphate regulating endopeptidase homolog X-linked (PHEX) gene. Although the overproduction of fibroblast growth factor 23 (FGF23) is responsible for hypophosphatemia and impaired vitamin D metabolism, the pathogenesis of XLH remains unclear. We herein generated PHEX-knockout (KO) human induced pluripotent stem (iPS) cells by applying CRISPR/Cas9-mediated gene ablation to an iPS clone derived from a healthy male, and analyzed PHEX-KO iPS cells with deletions extending from exons 1 to 3 and frameshifts by inducing them to differentiate into the osteoblast lineage. We confirmed the increased production of FGF23 in osteoblast lineage cells differentiated from PHEX-KO iPS cells. In vitro mineralization was enhanced in osteoblast lineage cells from PHEX-KO iPS cells than in those from isogenic control iPS cells, which reminded us of high bone mineral density and enthesopathy in patients with XLH. The extracellular level of pyrophosphate (PPi), an inhibitor of mineralization, was elevated, and this increase appeared to be partly due to the reduced activity of tissue non-specific alkaline phosphatase (TNSALP). Osteoblast lineage cells derived from PHEX-KO iPS cells also showed the increased expression of multiple molecules such as dentine matrix protein 1, osteopontin, RUNX2, FGF receptor 1 and early growth response 1. This gene dysregulation was similar to that in the osteoblasts/osteocytes of Phex-deficient Hyp mice, suggesting that common pathogenic mechanisms are shared between human XLH and Hyp mice. Moreover, we found that the phosphorylation of CREB was markedly enhanced in osteoblast lineage cells derived from PHEX-KO iPS cells, which appeared to be associated with the up-regulation of the parathyroid hormone related protein gene. PHEX deficiency also affected the response of the ALPL gene encoding TNSALP to extracellular Pi. Collectively, these results indicate that complex intrinsic abnormalities in osteoblasts/osteocytes underlie the pathogenesis of human XLH.

Zinc based biodegradable metals for bone repair and regeneration: Bioactivity and molecular mechanisms

Bone fractures and critical-size bone defects are significant public health issues, and clinical treatment outcomes are closely related to the intrinsic properties of the utilized implant materials. Zinc (Zn)-based biodegradable metals (BMs) have emerged as promising bioactive materials because of their exceptional biocompatibility, appropriate mechanical properties, and controllable biodegradation. This review summarizes the state of the art in terms of Zn-based metals for bone repair and regeneration, focusing on bridging the gap between biological mechanism and required bioactivity. The molecular mechanism underlying the release of Zn ions from Zn-based BMs in the improvement of bone repair and regeneration is elucidated. By integrating clinical considerations and the specific bioactivity required for implant materials, this review summarizes the current research status of Zn-based internal fixation materials for promoting fracture healing, Zn-based scaffolds for regenerating critical-size bone defects, and Zn-based barrier membranes for reconstituting alveolar bone defects. Considering the significant progress made in the research on Zn-based BMs for potential clinical applications, the challenges and promising research directions are proposed and discussed.

Brain-Derived Neurotrophic Factor (BDNF) Enhances Osteogenesis and May Improve Bone Microarchitecture in an Ovariectomized Rat Model

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has gained attention as a therapeutic agent due to its potential biological activities, including osteogenesis. However, the molecular mechanisms involved in the osteogenic activity of BDNF have not been fully understood. This study aimed to investigate the action of BDNF on the osteoblast differentiation in bone marrow stromal cells, and its influence on signaling pathways. In addition, to evaluate the clinical efficacy, an in vivo animal study was performed.

METHODS

Preosteoblast cells (MC3T3-E1), bone marrow-derived stromal cells (ST2), and a direct 2D co-culture system were treated with BDNF. The effect of BDNF on cell proliferation was determined using the CCK-8 assay. Osteoblast differentiation was assessed based on alkaline phosphatase (ALP) activity and staining and the protein expression of multiple osteoblast markers. Calcium accumulation was examined by Alizarin red S staining. For the animal study, we used ovariectomized Sprague-Dawley rats and divided them into BDNF and normal saline injection groups. MicroCT, hematoxylin and eosin (H&E), and tartrate-resistant acid phosphatase (TRAP) stain were performed for analysis.

RESULTS

BDNF significantly increased ALP activity, calcium deposition, and the expression of osteoblast differentiation-related proteins, such as ALP, osteopontin, etc., in both ST-2 and the MC3T3-E1 and ST-2 co-culture systems. Moreover, the effect of BDNF on osteogenic differentiation was diminished by blocking tropomyosin receptor kinase B, as well as inhibiting c-Jun N-terminal kinase and p38 MAPK signals. Although the animal study results including bone density and histology showed increased osteoblastic and decreased osteoclastic activity, only a portion of parameters reached statistical significance.

CONCLUSIONS

Our study results showed that BDNF affects osteoblast differentiation through TrkB receptor, and JNK and p38 MAPK signal pathways. Although not statistically significant, the trend of such effects was observed in the animal experiment.

Tunable Zeolitic Imidazolate Framework-8 Nanoparticles for Biomedical Applications

Zeolite imidazole framework-8 (ZIF-8) is the most prestigious one among zeolitic imidazolate framework (ZIF) with tunable dimensions and unique morphological features. Utilizing its synthetic adjustability and structural regularity, ZIF-8 exhibits enhanced flexibility, allowing for a wide range of functionalities, such as loading of nanoparticle components while preserving biomolecules activity. Extensive efforts are made from investigating synthesis techniques to develop novel applications over decades. In this review, the development and recent progress of various synthesis approaches are briefly summarized. In addition, its interesting properties such as adjustable porosity, excellent thermal, and chemical stabilities are introduced. Further, five representative biomedical applications are highlighted based on above physicochemical properties. Finally, the remaining challenges and offered insights into the future outlook are also discussed. This review aims to understand the co-relationships between structures and biomedical functionalities, offering the opportunity to construct attractive materials with promising characteristics.

A Dose-Dependent Spatiotemporal Response of Angiogenesis Elicited by Zn Biodegradation during the Initial Stage of Bone Regeneration

Zinc (Zn) plays a crucial role in bone metabolism and imbues biodegradable Zn-based materials with the ability to promote bone regeneration in bone trauma. However, the impact of Zn biodegradation on bone repair, particularly its influence on angiogenesis, remains unexplored. This study reveals that Zn biodegradation induces a consistent dose-dependent spatiotemporal response in angiogenesis,both in vivo and in vitro. In a critical bone defect model, an increase in Zn release intensity from day 3 to 10 post-surgery is observed. By day 10, the CD31-positive area around the Zn implant significantly surpasses that of the Ti implant, indicating enhanced angiogenesis. Furthermore,angiogenesis exhibits a distance-dependent pattern closely mirroring the distribution of Zn signals from the implant. In vitro experiments demonstrate that Zn extraction fosters the proliferation and migration of human umbilical vein endothelial cells and upregulates the key genes associated with tube formation, such as HIF-1α and VEGF-A, peaking at a concentration of 22.5 µM. Additionally, Zn concentrations within the range of 11.25-45 µM promote the polarization of M0-type macrophages toward the M2-type, while inhibiting polarization toward the M1-type. These findings provide essential insights into the biological effects of Zn on bone repair, shedding light on its potential applications.

Zeolite imidazolate framework-8 in bone regeneration: A systematic review

Zeolite imidazolate framework-8 (ZIF-8) is a biomaterial that has been increasingly studied in recent years. It has several applications such as bone regeneration, promotion of angiogenesis, drug loading, and antibacterial activity, and exerts multiple effects to deal with various problems in the process of bone regeneration. This systematic review aims to provide an overview of the applications and effectiveness of ZIF-8 in bone regeneration. A search of papers published in the PubMed, Web of Science, Embase, and Cochrane Library databases revealed 532 relevant studies. Title, abstract, and full-text screening resulted in 39 papers being included in the review, including 39 in vitro and 22 animal studies. Appropriate concentrations of nano ZIF-8 can promote cell proliferation and osteogenic differentiation by releasing Zn2+ and entering the cell, whereas high doses of ZIF-8 are cytotoxic and inhibit osteogenic differentiation. In addition, five studies confirmed that ZIF-8 exhibits good vasogenic activity. In all in vivo experiments, nano ZIF-8 promoted bone formation. These results indicate that, at appropriate concentrations, materials containing ZIF-8 promote bone regeneration more than materials without ZIF-8, and with characteristics such as promoting angiogenesis, drug loading, and antibacterial activity, it is expected to show promising applications in the field of bone regeneration. STATEMENT OF SIGNIFICANCE: This manuscript reviewed the use of ZIF-8 in bone regeneration, clarified the biocompatibility and effectiveness in promoting bone regeneration of ZIF-8 materials, and discussed the possible mechanisms and factors affecting its promotion of bone regeneration. Overall, this study provides a better understanding of the latest advances in the field of bone regeneration of ZIF-8, serves as a design guide, and contributes to the design of future experimental studies.

LncRNA USP2-AS1 facilitates the osteogenic differentiation of bone marrow mesenchymal stem cells by targeting KDM3A/ETS1/USP2 to activate the Wnt/β-catenin signaling pathway

Human bone marrow mesenchymal stem cells (HBMSCs) can promote new bone formation. Previous studies have proven the ability of long non-coding RNAs (lncRNAs) to modulate the osteogenic differentiation of mesenchymal stem cells. However, the molecular mechanism modulated by lncRNAs in affecting the osteogenic differentiation of HBMSCs remains largely unknown. Thus, this study aims to reveal the role of lncRNA ubiquitin-specific peptidase 2 antisense RNA 1 (USP2-AS1) in regulating the osteogenic differentiation of HBMSCs and investigate its regulatory mechanism. Through bioinformatics analysis and RT-qPCR, we confirmed that USP2-AS1 expression was increased in HBMSCs after culturing in osteogenic differentiation medium (OM-HBMSCs). Moreover, we uncovered that knockdown of USP2-AS1 inhibited the osteogenic differentiation of HBMSCs. Further exploration indicated that USP2-AS1 positively regulated the expression of its nearby gene USP2. Mechanistically, USP2-AS1 recruited lysine demethylase 3A (KDM3A) to stabilize ETS proto-oncogene 1 (ETS1), transcription factor that transcriptionally activated USP2. Additionally, USP2-induced Wnt/β-catenin signalling pathway activation via deubiquitination of β-catenin protein. In summary, our study proved that lncRNA USP2-AS1 facilitates the osteogenic differentiation of HBMSCs by targeting KDM3A/ETS1/USP2 axis to activate the Wnt/β-catenin signalling pathway.

Zinc-based biomaterials for bone repair and regeneration: mechanism and applications

Zinc (Zn) is one of the most important trace elements in the human body and plays a key role in various physiological processes, especially in bone metabolism. Zn-containing materials have been reported to enhance bone repair through promoting cell proliferation, osteogenic activity, angiogenesis, and inhibiting osteoclast differentiation. Therefore, Zn-based biomaterials are potential substitutes for traditional bone grafts. In this review, the specific mechanisms of bone formation promotion by Zn-based biomaterials were discussed, and recent developments in their application in bone tissue engineering were summarized. Moreover, the challenges and perspectives of Zn-based biomaterials were concluded, revealing their attractive potential and development directions in the future.

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.

Metal Ion-Doped Hydroxyapatite-Based Materials for Bone Defect Restoration

Hydroxyapatite (HA)-based materials are widely used in the bone defect restoration field due to their stable physical properties, good biocompatibility, and bone induction potential. To further improve their performance with extra functions such as antibacterial activity, various kinds of metal ion-doped HA-based materials have been proposed and synthesized. This paper offered a comprehensive review of metal ion-doped HA-based materials for bone defect restoration based on the introduction of the physicochemical characteristics of HA followed by the synthesis methods, properties, and applications of different kinds of metal ion (Ag+, Zn2+, Mg2+, Sr2+, Sm3+, and Ce3+)-doped HA-based materials. In addition, the underlying challenges for bone defect restoration using these materials and potential solutions were discussed.

Carnosine, Zinc and Copper: A Menage a Trois in Bone and Cartilage Protection

Dysregulated metal homeostasis is associated with many pathological conditions, including arthritic diseases. Osteoarthritis and rheumatoid arthritis are the two most prevalent disorders that damage the joints and lead to cartilage and bone destruction. Recent studies show that the levels of zinc (Zn) and copper (Cu) are generally altered in the serum of arthritis patients. Therefore, metal dyshomeostasis may reflect the contribution of these trace elements to the disease's pathogenesis and manifestations, suggesting their potential for prognosis and treatment. Carnosine (Car) also emerged as a biomarker in arthritis and exerts protective and osteogenic effects in arthritic joints. Notably, its zinc(II) complex, polaprezinc, has been recently proposed as a drug-repurposing candidate for bone fracture healing. On these bases, this review article aims to provide an overview of the beneficial roles of Cu and Zn in bone and cartilage health and their potential application in tissue engineering. The effects of Car and polaprezinc in promoting cartilage and bone regeneration are also discussed. We hypothesize that polaprezinc could exchange Zn for Cu, present in the culture media, due to its higher sequestering ability towards Cu. However, future studies should unveil the potential contribution of Cu in the beneficial effects of polaprezinc.

Metal ions: the unfading stars of bone regeneration-from bone metabolism regulation to biomaterial applications

In recent years, bone regeneration has emerged as a remarkable field that offers promising guidance for treating bone-related diseases, such as bone defects, bone infections, and osteosarcoma. Among various bone regeneration approaches, the metal ion-based strategy has surfaced as a prospective candidate approach owing to the extensive regulatory role of metal ions in bone metabolism and the diversity of corresponding delivery strategies. Various metal ions can promote bone regeneration through three primary strategies: balancing the effects of osteoblasts and osteoclasts, regulating the immune microenvironment, and promoting bone angiogenesis. In the meantime, the complex molecular mechanisms behind these strategies are being consistently explored. Moreover, the accelerated development of biomaterials broadens the prospect of metal ions applied to bone regeneration. This review highlights the potential of metal ions for bone regeneration and their underlying mechanisms. We propose that future investigations focus on refining the clinical utilization of metal ions using both mechanistic inquiry and materials engineering to bolster the clinical effectiveness of metal ion-based approaches for bone regeneration.

The changes and potential effects of zinc homeostasis in periodontitis microenvironment

Zinc is a very important and ubiquitous element, which is present in oral environment, daily diet, oral health products, dental restorative materials, and so on. However, there is a lack of attention to the role of both extracellular or intracellular zinc in the progression of periodontitis and periodontal regeneration. This review summarizes the characteristics of immunological microenvironment and host cells function in several key stages of periodontitis progression, and explores the regulatory effect of zinc during this process. We find multiple evidence indicate that zinc may be involved and play a key role in the stages of immune defense, inflammatory response and bone remodeling. Zinc supplementation in an appropriate dose range or regulation of zinc transport proteins can promote periodontal regeneration by either enhancing immune defense or up-regulating local cells proliferation and differentiation functions. Therefore, zinc homeostasis is essential in periodontal remodeling and regeneration. More attention is suggested to be focused on zinc homeostasis regulation and consider it as a potential strategy in the studies on periodontitis treatment, periodontal-guided tissue regeneration, implant material transformation, and so on.

Stunting and wasting in neurological Wilson disease: Role of copper, zinc, and insulin-like growth factor-I

OBJECTIVES

Copper (Cu) and zinc (Zn) are important trace elements for the growth and development of children. In Wilson disease (WD), impaired Cu metabolism may affect growth. This study was conducted to evaluate the height and weight of children with neurological WD and correlate these with serum Cu, Zn, and insulin-like growth factor-I (IGF-I).

METHODS

This prospective cohort study was conducted in a tertiary care teaching institute. Children with neurologic WD were included. The height, weight, and body-mass index of each child were measured and categorized according to the revised national growth chart. Serum Cu, Zn, calcium, alkaline phosphatase, albumin, thyroid-stimulating hormone, and urinary-Cu were measured. Serum IGF-1 was measured by enzyme-linked immunosorbent assay. The relationship between height and weight with trace elements and IGF was analyzed using parametric or non-parametric tests.

RESULTS

There were 52 children (5-18 years) with neurologic WD. Thirty-six (69.2%) children had normal height, 12 (23.1%) were tall, and 4 (7.7%) were stunted. Forty-six (88.5%) children had normal weight and six (11.5%) children were underweight. IGF-1 correlated with height, weight, duration of treatment, and serum Zn level. About 15.4% of children had stunting and/or wasting, which was associated with low levels of serum IGF-I, Zn, and calcium.

CONCLUSIONS

Stunting and/or wasting occurs in 15.4% of children with neurologic WD and is associated with reduced serum IGF-I, Zn, and calcium concentration. Adjunctive Zn and calcium treatment may help in achieving normal growth.

Fabrication and Characterization of Zn Particle Incorporated Fibrous Scaffolds for Potential Application in Tissue Healing and Regeneration

Zinc (Zn) metal and its alloys have received a lot of interest in biomedical applications due to their biodegradability, biocompatibility, antimicrobial activity, and ability to stimulate tissue regeneration. Bulk Zn has been successfully utilized in a variety of implant applications, most notably as bioabsorbable cardiac stents and orthopedic fixation devices, where it provides adequate mechanical properties while also releasing helpful Zn ions (Zn2+) during degradation. Such beneficial ions are dose-dependent and, when released in excess, can induce cellular toxicity. In this study, we hypothesize that embedding Zn metal particles into a polymer nanofibrous scaffold will enable control of the degradation and time release of the Zn2+. We designed and fabricated two polymer scaffolds, polycaprolactone (PCL) and polycaprolactone-chitosan (PCL-CH). Each scaffold had an increasing amount of Zn. Several physicochemical properties such as fiber morphology, crystallinity, mechanical strength, hydrophilicity, degradation and release of Zn2+, thermal properties, chemical compositions, and so forth were characterized and compared with the PCL fibrous scaffold. The biological properties of the scaffolds were evaluated in vitro utilizing direct and indirect cytotoxicity assays and cell viability. All the data show that the addition of Zn changed various physical properties of the PCL and PCL-CH scaffolds except their chemical structure. Further investigation reveals that the PCL-CH scaffolds degrade the Zn particles relatively faster than the PCL because the presence of the hydrophilic CH influences the faster release of Zn2+ in cell culture conditions as compared to the PCL fibrous scaffold. The combined advantages of CH and Zn in the PCL scaffold enriched 3T3 fibroblast cells' survival and proliferation except the ones with the higher concentration of Zn particles. These new composite scaffolds are promising and can be further considered for tissue healing and regeneration applications.

Effects of Zinc and Strontium Doping on In Vitro Osteogenesis and Angiogenesis of Calcium Silicate/Calcium Phosphate Cement

Based on multiple biological functions (mainly osteogenesis and angiogenesis) of bioactive ions, Zn/Sr-doped calcium silicate/calcium phosphate cements (Zn/Sr-CS/CPCs, including 10Zn-CS/CPC, 20Sr-CS/CPC, and 10Zn/20Sr-CS/CPC) were prepared by the addition of Zn and Sr dual active ions into CS/CPC to further accelerate its bone regeneration in this study. The physicochemical and biological properties of the Zn/Sr-CS/CPCs were systematically investigated. The results showed that the setting time was slightly prolonged, the compressive strength and porosity did not change much, and all groups maintained good injectability after the doping of Zn and Sr. Besides, the doping of Zn and Sr had little effect on the phase and microstructure of hydrated products of CS/CPC. The degradation rate of Zn/Sr-CS/CPCs decreased after doping with Zn and Sr. In mouse bone marrow mesenchymal stem cells (mBMSC) experiments, all Zn/Sr-CS/CPCs stimulated the viability, adhesion, proliferation, and alkaline phosphatase (ALP) activity together with osteogenesis-related genes (ALP, Runx2, Col-I, OCN, and OPN). The further addition of Zn and Sr played better and synergistic roles in in vitro osteogenesis. Thereinto, 10Zn/20Sr-CS/CPC manifested the optimum in vitro osteogenic performance. As for human umbilical vein endothelial cell (HUVEC) experiments, the incorporation of CS doped with Zn and Sr into CPC possessed good vascularization properties of proliferation, NO secretion, tube formation, and the expression of angiogenesis-related genes (VEGF, bFGF, and eNOS). In conclusion, the doping of Zn and Sr into CS/CPC could exhibit excellent osteogenesis and good angiogenesis potentials and 10Zn/20Sr-CS/CPC could be considered as a promising candidate in bone repair.

Engineered Nano-Bio Interfaces for Stem Cell Therapy

Engineered nanomaterials (ENMs) with different topographies provide effective nano-bio interfaces for controlling the differentiation of stem cells. The interaction of stem cells with nanoscale topographies and chemical cues in their microenvironment at the nano-bio interface can guide their fate. The use of nanotopographical cues, in particular nanorods, nanopillars, nanogrooves, nanofibers, and nanopits, as well as biochemical forces mediated factors, including growth factors, cytokines, and extracellular matrix proteins, can significantly impact stem cell differentiation. These factors were seen as very effective in determining the proliferation and spreading of stem cells. The specific outgrowth of stem cells can be decided with size variation of topographic nanomaterial along with variation in matrix stiffness and surface structure like a special arrangement. The precision chemistry enabled controlled design, synthesis, and chemical composition of ENMs can regulate stem cell behaviors. The parameters of size such as aspect ratio, diameter, and pore size of nanotopographic structures are the main factors for specific termination of stem cells. Protein corona nanoparticles (NPs) have shown a powerful facet in stem cell therapy, where combining specific proteins could facilitate a certain stem cell differentiation and cellular proliferation. Nano-bio reactions implicate the interaction between biological entities and nanoparticles, which can be used to tailor the stem cells' culmination. The ion release can also be a parameter to enhance cellular proliferation and to commit the early differentiation of stem cells. Further research is needed to fully understand the mechanisms underlying the interactions between engineered nano-bio interfaces and stem cells and to develop optimized regenerative medicine and tissue engineering designs.

The Role of Trace Elements and Minerals in Osteoporosis: A Review of Epidemiological and Laboratory Findings

The objective of the present study was to review recent epidemiological and clinical data on the association between selected minerals and trace elements and osteoporosis, as well as to discuss the molecular mechanisms underlying these associations. We have performed a search in the PubMed-Medline and Google Scholar databases using the MeSH terms "osteoporosis", "osteogenesis", "osteoblast", "osteoclast", and "osteocyte" in association with the names of particular trace elements and minerals through 21 March 2023. The data demonstrate that physiological and nutritional levels of trace elements and minerals promote osteogenic differentiation through the up-regulation of BMP-2 and Wnt/β-catenin signaling, as well as other pathways. miRNA and epigenetic effects were also involved in the regulation of the osteogenic effects of trace minerals. The antiresorptive effect of trace elements and minerals was associated with the inhibition of osteoclastogenesis. At the same time, the effect of trace elements and minerals on bone health appeared to be dose-dependent with low doses promoting an osteogenic effect, whereas high doses exerted opposite effects which promoted bone resorption and impaired bone formation. Concomitant with the results of the laboratory studies, several clinical trials and epidemiological studies demonstrated that supplementation with Zn, Mg, F, and Sr may improve bone quality, thus inducing antiosteoporotic effects.

Allosteric Activation of Transglutaminase 2 via Inducing an "Open" Conformation for Osteoblast Differentiation

Osteoblasts play an important role in the regulation of bone homeostasis throughout life. Thus, the damage of osteoblasts can lead to serious skeletal diseases, highlighting the urgent need for novel pharmacological targets. This study introduces chemical genetics strategy by using small molecule forskolin (FSK) as a probe to explore the druggable targets for osteoporosis. Here, this work reveals that transglutaminase 2 (TGM2) served as a major cellular target of FSK to obviously induce osteoblast differentiation. Then, this work identifies a previously undisclosed allosteric site in the catalytic core of TGM2. In particular, FSK formed multiple hydrogen bonds in a saddle-like domain to induce an "open" conformation of the β-sandwich domain in TGM2, thereby promoting the substrate protein crosslinks by incorporating polyamine. Furthermore, this work finds that TGM2 interacted with several mitochondrial homeostasis-associated proteins to improve mitochondrial dynamics and ATP production for osteoblast differentiation. Finally, this work observes that FSK effectively ameliorated osteoporosis in the ovariectomy mice model. Taken together, these findings show a previously undescribed pharmacological allosteric site on TGM2 for osteoporosis treatment, and also provide an available chemical tool for interrogating TGM2 biology and developing bone anabolic agent.

Nano sized gallium oxide surface features for enhanced antimicrobial and osteo-integrative responses

Gallium oxide has known beneficial osteo-integrative properties. This may have importance for improving the osteointegration of orthopedic implants. At high concentrations gallium is cytotoxic. Therefore, integration of gallium into implant devices must be carefully controlled to limit its concentration and release. A strategy based on surface doping of gallium although challenging seems an appropriate approach to limit dose amounts to minimize cytotoxicity and maximize osteointegration benefits. In this work we develop a novel form of patterned surface doping via a block copolymer-based surface chemistry that enables very low gallium content but enhanced osteointegration as proven by comprehensive bioassays. Polystyrene-b-poly 4vinyl pyridine (PS-b-P4VP) BCP (block copolymer) films were produced on surfaces. Selective infiltration of the BCP pattern with a gallium salt precursor solution and subsequent UV-ozone treatment produced a surface pattern of gallium oxide nanodots as evidenced by atomic force and scanning electron microscopy. A comprehensive study of the bioactivity was carried out, including antimicrobial and sterility testing, gallium ion release kinetics and the interaction with human marrow mesenchymal stomal cells and mononuclear cells. Comparing the data from osteogenesis media assay tests with osteoclastogenesis tests demonstrated the potential for the gallium oxide nanodot doping to improve osteointegration properties of a surface.

Comparisons of gene expression between peripheral blood mononuclear cells and bone tissue in osteoporosis

Osteoporosis (OP) is one of the major public health problems in the world. However, the biomarkers between the peripheral blood mononuclear cells (PBMs) and bone tissue for prognosis of OP have not been well characterized. This study aimed to explore the similarities and differences of the gene expression profiles between the PBMs and bone tissue and identify potential genes, transcription factors (TFs) and hub proteins involved in OP. The patients were enrolled as an experimental group, and healthy subjects served as normal controls. Human whole-genome expression chips were used to analyze gene expression profiles from PBMs and bone tissue. And the differentially expressed genes (DEGs) were subsequently studied using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis. The above DEGs were constructed into protein-protein interaction network. Finally, TF-DEGs regulation networks were constructed. Microarray analysis revealed that 226 DEGs were identified between OP and normal controls in the PBMs, while 2295 DEGs were identified in the bone tissue. And 13 common DEGs were obtained by comparing the 2 tissues. The Gene Ontology analysis indicated that DEGs in the PBMs were more involved in immune response, while DEGs in bone were more involved in renal response and urea transmembrane transport. And the Kyoto Encyclopedia of Genes and Genomes analysis indicated almost all of the pathways in the PBMs were overlapped with those in the bone tissue. Furthermore, protein-protein interaction network presented 6 hub proteins: PI3K1, APP, GNB5, FPR2, GNG13, and PLCG1. APP has been found to be associated with OP. Finally, 5 key TFs were identified by TF-DEGs regulation networks analysis (CREB1, RUNX1, STAT3, CREBBP, and GLI1) and were supposed to be associated with OP. This study enhanced our understanding of the pathogenesis of OP. PI3K1, GNB5, FPR2, GNG13, and PLCG1 might be the potential targets of OP.

Bioactive ZnO-assisted 1393 glass scaffold promotes osteogenic differentiation: Some studies

We developed ZnO-assisted 1393 bioactive glass-based scaffold with suitable mechanical properties through foam replica technique and observed to be suitable for bone tissue engineering application. However, the developed scaffolds' ability to facilitate cellular infiltration and integration was further assessed through in vivo studies in suitable animal model. Herein, the pure 1393 bioactive glass (BG) and ZnO-assisted 1393 bioactive glass- (ZnBGs; 1, 2, 4 mol% ZnO substitution for SiO₂ in pure BG is named as Z1BG, Z2BG, Z3BG, respectively) based scaffolds were prepared through sol-gel route, followed by foam replica techniques and characterized by a series of in vitro and some in vivo tests. Different cell lines like normal mouse embryonic cells (NIH/3T3), mouse bone marrow stromal cells (mBMSc), peripheral blood mononuclear cells, that is, lymphocytes and monocytes (PBMC) and U2OS (carcinogenic human osteosarcoma cells) were used in determination and comparative analysis of the biological compatibility of the BG and ZnBGs. Also, the alkaline phosphatase (ALP) activity, and osteogenic gene expression by primer-specific osteopontin (OPN), osteocalcin (OCN), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes were performed to study osteogenic differentiability of the stromal cells in different BGs. Moreover, radiological and histopathological tests were performed in bone defect model of Wister rats to evaluate the in vivo bone regeneration and healing. Interestingly, these studies demonstrate augmented biological compatibility, and superior osteogenic differentiation in ZnBGs, in particular Z3BG than the pure BG in most cases.

Effect of Nano- and Microzinc Supplementation on the Mineral Composition of Bones of Rats with Induced Mammary Gland Cancer

BACKGROUND

The aim of this study was to determine changes in the mineral composition of the bones of rats with chemically induced mammary gland cancer and to attempt to establish whether a specific diet modification involving the inclusion of zinc ions in two forms-nano and micro-will affect the mineral composition of the bones.

METHODS

Female Sprague-Dawley rats were used for the research. The animals were randomly assigned to three experimental groups. All animals were fed a standard diet (Labofeed H), and selected groups additionally received zinc nanoparticles or microparticles in the amount of 4.6 mg/mL. To induce mammary cancer, the animals were given 7,12-dimethyl-1,2-benz[a]anthracene. The content of Ag, As, B, Ba, Cd, Cr, Cu, Mn, Ni, Pb, Rb, Se, Sr, Tl, U, and V was determined using ICP-MS, while that of Ca, Fe, K, Mg, Na, and Zn was determined using FAAS.

RESULTS

The use of a diet enriched with zinc nano- or microparticles significantly influenced the content of the elements tested. In the bones of rats fed a diet with zinc nanoparticles, changes were found in the content of Ca, Mg, Zn, Cd, U, V, and Tl, while in the case of the diet supplemented with zinc microparticles, there were differences in six elements-Ca, Mg, B, Cd, Ag, and Pb-compared to animals receiving an unsupplemented diet.

CONCLUSIONS

The content of elements in the bone tissue of rats in the experimental model indicates disturbances of mineral metabolism in the tissue at an early stage of mammary cancer.

ZnO nanoparticles-modified polycaprolactone-gelatin membranes for guided/bone tissue regeneration, antibacterial and osteogenic differentiation properties

Periodontitis is a highly prevalent infectious disease that causes the progressive destruction of the periodontal supporting tissues. If left untreated, it can lead to tooth loss impairing oral function, aesthetics, and the patient's overall quality of life. Guided and Bone Tissue Regeneration (GTR/BTR) are surgical therapies based on the placement of a membrane that prevents epithelial growth into the defect, allowing the periodontal/bone cells (including stem cells) to regenerate or restore the affected tissues. The success of these therapies is commonly affected by the local bacterial colonization of the membrane area and its fast biodegradation, causing postoperative infections and a premature rupture of the membrane limiting the regeneration process. This study presents the antibacterial and osteogenic differentiation properties of polycaprolactone-gelatin (PCL-G) electrospun membranes modified with ZnO nanoparticles (ZnO-NPs). The membranes´ chemical composition, surface roughness, biodegradation, water wettability, and mechanical properties under simulated physiological conditions, were analyzed by the close relationship with their biological properties. The PCL-G membranes modified with 1, 3, and 6% w/w of ZnO-NPs showed a significant reduction in the planktonic and biofilm formation of four clinically relevant bacteria;A. actinomycetemcomitansserotype b, P. gingivalis,E. coli, andS. epidermidis. Additionally, the membranes presented appropriate mechanical properties and biodegradation rates to be potentially used in clinical treatments. Notably, the membranes modified with the lowest concentration of ZnO-NPs (1% w/w) stimulated the production of osteoblast markers and calcium deposits in human bone marrow-derived mesenchymal stem cells (BM-MSC) and were biocompatible to human osteoblasts cells (hFOB). These results suggest that the PCL-G membranes with 1% w/w of ZnO-NPs are high-potential candidates for GTR/BTR treatments, as they were the most effective in terms of better antibacterial effectiveness at a lower NPs-concentration while creating a favorable cellular microenvironment for bone growth.

Iron, Zinc, Copper, Cadmium, Mercury, and Bone Tissue

The paper presents the current understanding on the effects of five metals on bone tissue, namely iron, zinc, copper, cadmium, and mercury. Iron, zinc, and copper contribute significantly to human and animal metabolism when present in sufficient amounts, but their excess or shortage increases the risk of developing bone disorders. In contrast, cadmium and mercury serve no physiological purpose and their long-term accumulation damages the osteoarticular system. We discuss the methods of action and interactions between the discussed elements as well as the concentrations of each element in distinct bone structures.

ZDHHC16 restrains osteogenic differentiation of bone marrow mesenchymal stem cells by inhibiting phosphorylation of CREB

Aims

The osteogenesis of human bone marrow mesenchymal stem cells (hBMSCs) plays a critical role in fracture healing. Osteogenic differentiation is regulated by a variety of post-translational modifications, but the function of protein palmitoylation in osteogenesis remains largely unknown.

Methods

Osteogenic differentiation induction of hBMSCs was used in this study. RT‒qPCR and immunoblotting assays (WB) were used to test marker genes of osteogenic induction. Alkaline phosphatase (ALP) activity, ALP staining and Alizarin red staining were performed to evaluate osteogenesis of hBMSCs. Signal finder pathway reporter array, co-immunoprecipitation and WB were applied to elucidate the molecular mechanism. A mouse fracture model was used to verify the in vivo function of the ZDHHC inhibitor.

Key findings

We revealed that palmitic acid inhibited Runx2 mRNA expression in hBMSCs and identified ZDHHC16 as a potential target palmitoyl acyltransferase. In addition, ZDHHC16 decreased during osteogenic induction. Next, we confirmed the inhibitory function of ZDHHC16 by its knockdown or overexpression during osteogenesis of hBMSCs. Moreover, we illustrated that ZDHHC16 inhibited the phosphorylation of CREB, thus inhibiting osteogenesis of hBMSCs by enhancing the palmitoylation of CREB. With a mouse femur fracture model, we found that 2-BP, a general inhibitor of ZDHHCs, promoted fracture healing in vivo. Thus, we clarified the inhibitory function of ZDHHC16 during osteogenic differentiation.

Significance

Collectively, these findings highlight the inhibitory function of ZDHHC16 in osteogenesis as a potential therapy method for fracture healing.

Zinc in Regulating Protein Kinases and Phosphatases in Neurodegenerative Diseases

Zinc is essential for human growth and development. As a trace nutrient, zinc plays important roles in numerous signal transduction pathways involved in distinct physiologic or pathologic processes. Protein phosphorylation is a posttranslational modification which regulates protein activity, degradation, and interaction with other molecules. Protein kinases (PKs) and phosphatases (PPs), with their effects of adding phosphate to or removing phosphate from certain substrates, are master regulators in controlling the phosphorylation of proteins. In this review, we summarize the disturbance of zinc homeostasis and role of zinc disturbance in regulating protein kinases and protein phosphatases in neurodegenerative diseases, with the focus of that in Alzheimer’s disease, providing a new perspective for understanding the mechanisms of these neurologic diseases.

Protein kinase A is activated during bone morphogenetic protein 2-induced osteogenic differentiation of dental follicle stem cells via endogenous parathyroid hormone-related protein

OBJECTIVE

The aim of this study was to investigate the mechanisms of how protein kinase A (PKA) is activated during bone morphogenetic protein 2 (BMP2)-induced osteogenic differentiation in dental follicle stem cells.

DESIGN

Human dental follicle stem cells were cultured and treated with a BMP2-containing osteogenic differentiation medium or differentiation medium without BMP2. Specific siRNAs and substances/proteins were used to modulate pathways. PKA activity and activity of alkaline phosphatase were determined. Expression of targets was measured by Western Blots and reverse transcription-quantitative polymerase chain reaction, while protein interactions were investigated by immunoprecipitation. Immunofluorescence staining was used for subcellular target localization.

RESULTS

PKA activity is stimulated after osteogenic induction by BMP2. Differentiation medium without BMP2 strongly induces BMP2 gene expression, which correlates with downstream target expression. Elevation of cAMP levels does not affect alkaline phosphatase activity and PKA does not directly interact with Smad 4. However, PKA activation requires expression of parathyroid hormone-related protein (PTHrP), which is stimulated after BMP2-induced differentiation. Furthermore, neither supplementation with PTHrP nor with the receptor antagonist parathyroid hormone (7-34) affects PKA activity. Thus, endogenous PTHrP expression is required for PKA activation and immunofluorescence staining shows that PTHrP is mainly located in the nucleus of dental follicle stem cells. Beyond, knockdown of PKA stimulates the BMP2 signaling pathway and down-stream expression of PTHrP.

CONCLUSIONS

BMP2-induced osteogenic differentiation activates PKA in dental follicle stem cells via endogenous expression of PTHrP. Additionally, PKA inhibits BMP2 signaling and expression of PTHrP in a negative feedback loop.

Drug repositioning of polaprezinc for bone fracture healing

Fractures and related complications are a common challenge in the field of skeletal tissue engineering. Vitamin D and calcium are the only broadly available medications for fracture healing, while zinc has been recognized as a nutritional supplement for healthy bones. Here, we aimed to use polaprezinc, an anti-ulcer drug and a chelate form of zinc and L-carnosine, as a supplement for fracture healing. Polaprezinc induced upregulation of osteogenesis-related genes and enhanced the osteogenic potential of human bone marrow-derived mesenchymal stem cells and osteoclast differentiation potential of mouse bone marrow-derived monocytes. In mouse experimental models with bone fractures, oral administration of polaprezinc accelerated fracture healing and maintained a high number of both osteoblasts and osteoclasts in the fracture areas. Collectively, polaprezinc promotes the fracture healing process efficiently by enhancing the activity of both osteoblasts and osteoclasts. Therefore, we suggest that drug repositioning of polaprezinc would be helpful for patients with fractures.

Polaprezinc promoted both osteoblast and osteoclast differentiation and altered YAP protein expression in vitro, and animals treated with polaprezinc showed greater bone formation in their fracture calluses after 21 days.

Biomimetic Metal-Organic Frameworks as Targeted Vehicles to Enhance Osteogenesis

Although engineered nanoparticles loaded with specific growth factors are used to regulate differentiation of stem cells, the low loading efficiency and biocompatibility are still great challenges in tissue repair. A nature-inspired biomimetic delivery system with targeted functions is attractive for enhancing cell activity and controlling cell fate. Herein, a stem cell membrane (SCM)-wrapped dexamethasone (DEX)-loaded zeolitic imidazolate framework-8 (ZIF-8) is constructed, which integrates the synthetic nanomaterials with native plasma membrane, to achieve efficient DEX delivery and DEX-mediated bone repair. The DEX@ZIF-8-SCM enables high DEX loading capacity, modulates the sustained release, and facilitates the specific uptake of mesenchymal stem cells (MSCs), owing to the porous property of ZIF-8 and the innate targeting capability of SCM. The endocytosed DEX@ZIF-8-SCM shows high cytocompatibility and greatly enhances the osteogenic differentiation of MSCs. Furthermore, RNA-sequencing data reveal that the phosphoinositide 3-kinase (PI3K)-Akt signaling pathways are activated and dominantly involved in the accelerated osteogenesis. In the bone defect model, the administrated DEX@ZIF-8-SCM exerts excellent biocompatibility and effectively promotes bone regeneration. Overall, the SCM-derived biomimetic nanoplatform achieves targeted delivery, excellent biosafety, and enhanced osteogenic differentiation and bone repair, which provides a new and valid strategy for treating various tissue injuries.

The Role of Zinc in Bone Mesenchymal Stem Cell Differentiation

Zinc is an essential trace element for bone growth and bone homeostasis in the human body. Bone mesenchymal stem cells (BMSCs) are multipotent progenitors existing in the bone marrow stroma with the capability of differentiating along multiple lineage pathways. Zinc plays a paramount role in BMSCs, which can be spurred differentiating into osteoblasts, chondrocytes, or adipocytes, and modulates the formation and activity of osteoclasts. The expression of related genes also changed during the differentiation of various cell phenotypes. Based on the important role of zinc in BMSC differentiation, using zinc as a therapeutic approach for bone remodeling will be a promising method. This review explores the role of zinc ion in the differentiation of BMSCs into various cell phenotypes and outlines the existing research on their molecular mechanism.

Osteogenic differentiation of human mesenchymal stem cells on substituted calcium phosphate/chitosan composite scaffold

Ionic substitutions are a promising strategy to enhance the biological performance of calcium phosphates (CaP) and composite materials for bone tissue engineering applications. However, systematic studies have not been performed on multi-substituted organic/inorganic scaffolds. In this work, highly porous composite scaffolds based on CaPs substituted with Sr²⁺, Mg²⁺, Zn²⁺ and SeO₃^2- ions, and chitosan have been prepared by freeze-gelation technique. The scaffolds have shown highly porous structure, with very well interconnected pores and homogeneously dispersed CaPs, and high stability during 28 days in the degradation medium. Osteogenic potential of human mesenchymal stem cells seeded on scaffolds has been determined by histological, immunohistochemical and RT-qPCR analysis of cultured cells in static and dynamic conditions. Results indicated that ionic substitutions have a beneficial effect on cells and tissues. The scaffolds with multi-substituted CaPs have shown increased expression of osteogenesis related markers and increased phosphate deposits, compared to the scaffolds with non-substituted CaPs.

BMS-470539 Attenuates Oxidative Stress and Neuronal Apoptosis via MC1R/cAMP/PKA/Nurr1 Signaling Pathway in a Neonatal Hypoxic-Ischemic Rat Model

Neuronal apoptosis induced by oxidative stress plays an important role in the pathogenesis and progression of hypoxic-ischemic encephalopathy (HIE). Previous studies reported that activation of melanocortin-1 receptor (MC1R) exerts antioxidative stress, antiapoptotic, and neuroprotective effects in various neurological diseases. However, whether MC1R activation can attenuate oxidative stress and neuronal apoptosis after hypoxic-ischemic- (HI-) induced brain injury remains unknown. Herein, we have investigated the role of MC1R activation with BMS-470539 in attenuating oxidative stress and neuronal apoptosis induced by HI and the underlying mechanisms. 159 ten-day-old unsexed Sprague-Dawley rat pups were used. HI was induced by right common carotid artery ligation followed by 2.5 h of hypoxia. The novel-selective MC1R agonist BMS-470539 was administered intranasally at 1 h after HI induction. MC1R CRISPR KO plasmid and Nurr1 CRISPR KO plasmid were administered intracerebroventricularly at 48 h before HI induction. Percent brain infarct area, short-term neurobehavioral tests, Western blot, immunofluorescence staining, Fluoro-Jade C staining, and MitoSox Staining were performed. We found that the expression of MC1R and Nurr1 increased, peaking at 48 h post-HI. MC1R and Nurr1 were expressed on neurons at 48 h post-HI. BMS-470539 administration significantly attenuated short-term neurological deficits and infarct area, accompanied by a reduction in cleaved caspase-3-positive neurons at 48 h post-HI. Moreover, BMS-470539 administration significantly upregulated the expression of MC1R, cAMP, p-PKA, Nurr1, HO-1, and Bcl-2. However, it downregulated the expression of 4-HNE and Bax, as well as reduced FJC-positive cells, MitoSox-positive cells, and 8-OHdG-positive cells at 48 h post-HI. MC1R CRISPR and Nurr1 CRISPR abolished the antioxidative stress, antiapoptotic, and neuroprotective effects of BMS-470539. In conclusion, our findings demonstrated that BMS-470539 administration attenuated oxidative stress and neuronal apoptosis and improved neurological deficits in a neonatal HI rat model, partially via the MC1R/cAMP/PKA/Nurr1 signaling pathway. Early administration of BMS-470539 may be a novel therapeutic strategy for infants with HIE.