Tissue-nonspecific alkaline phosphatase promotes the osteogenic differentiation of osteoprogenitor cells

Osteogenic differentiation of periodontal ligament fibroblasts inhibits osteoclast formation

One of the deficits of knowledge on bone remodelling, is to what extent cells that are driven towards osteogenic differentiation can contribute to osteoclast formation. The periodontal ligament fibroblast (PdLFs) is an ideal model to study this, since they play a role in osteogenesis, and can also orchestrate osteoclastogenesis.when co-cultured with a source of osteoclast-precursor such as peripheral blood mononuclear cells (PBMCs). Here, the osteogenic differentiation of PdLFs and the effects of this process on the formation of osteoclasts were investigated. PdLFs were obtained from extracted teeth and exposed to osteogenic medium for 0, 7, 14, or 21 out of 21 days. After this 21-day culturing period, the cells were co-cultured with peripheral blood mononuclear cells (PBMCs) for an additional 21 days to study osteoclast formation. Alkaline phosphatase (ALP) activity, calcium concentration, and gene expression of osteogenic markers were assessed at day 21 to evaluate the different stages of osteogenic differentiation. Alizarin red staining and scanning electron microscopy were used to visualise mineralisation. Tartrate-resistant acid phosphatase (TRAcP) activity, TRAcP staining, multinuclearity, the expression of osteoclastogenesis-related genes, and TNF-α and IL-1β protein levels were assessed to evaluate osteoclastogenesis. The osteogenesis assays revealed that PdLFs became more differentiated as they were exposed to osteogenic medium for a longer period of time. Mineralisation by these osteogenic cells increased with the progression of differentiation. Culturing PdLFs in osteogenic medium before co-culturing them with PMBCs led to a significant decrease in osteoclast formation. qPCR revealed significantly lower DCSTAMP expression in cultures that had been supplemented with osteogenic medium. Protein levels of osteoclastogenesis stimulator TNF-α were also lower in these cultures. The present study shows that the osteogenic differentiation of PdLFs reduces the osteoclastogenic potential of these cells. Immature cells of the osteoblastic lineage may facilitate osteoclastogenesis, whereas mature mineralising cells may suppress the formation of osteoclasts. Therefore, mature and immature osteogenic cells may have different roles in maintaining bone homeostasis.

The role of fibroblast growth factor-2 in modulating the differentiation of periodontal ligament and alveolar bone-derived stem cells

OBJECTIVE

This study examined how range concentrations of Fibroblast Growth Factor-2 (FGF-2) influence the differentiation and activity of human-derived periodontal ligament (hPDLSCs) and alveolar bone-derived stem cells (haBMSCs).

DESIGN

hPDLSCs and haBMSCs were cultured with varying concentrations of FGF-2 (0, 1, 2.5, 5, 10, 20 ng/mL) and monitored for osteogenic differentiation through alkaline phosphatase (ALP) activity and quantification of gene expression (qRT-PCR) for osteogenesis markers. Additionally, alizarin red staining and a hydroxyproline colorimetric assay evaluated and quantified osteogenic matrix mineralization and collagen deposition. Statistical analyses were performed using one-way ANOVA or two-way ANOVA for multiple comparisons between groups.

RESULTS

At low FGF-2 concentrations, hPDLSCs differentiated toward an osteogenic lineage, whereas higher concentrations of FGF-2 inhibited osteogenesis and promoted fibroblastic differentiation. The effect of FGF-2 at the lowest concentration tested (1 ng/mL) led to significantly higher ALP activity than osteogenically induced positive controls at early time points and equivalent RUNX2 expression at early and later time points. FGF-2 supplementation of haBMSC cultures was sufficient, at all concentrations, to increase ALP activity at an earlier time point. Mineralization of haBMSC cultures increased significantly within 5-20 ng/mL FGF-2 concentrations under basal growth media conditions (α-minimal essential medium supplemented with 15 % fetal bovine serum and 1 % penicillin/streptomycin).

CONCLUSIONS

FGF-2 has a dual capacity in promoting osteogenic and fibroblastic differentiation within hPDLSCs contingent upon the dosage and timing of administration, alongside supporting osteogenic differentiation in haBMSCs. These findings underscore the need for precision growth factors dosing when considering the design of biomaterials for periodontal regeneration.

Nanofibrous Microspheres: A Biomimetic Platform for Bone Tissue Regeneration

Bone, a fundamental constituent of the human body, is a vital scaffold for support, protection, and locomotion, underscoring its pivotal role in maintaining skeletal integrity and overall functionality. However, factors such as trauma, disease, or aging can compromise bone structure, necessitating effective strategies for regeneration. Traditional approaches often lack biomimetic environments conducive to efficient tissue repair. Nanofibrous microspheres (NFMS) present a promising biomimetic platform for bone regeneration by mimicking the native extracellular matrix architecture. Through optimized fabrication techniques and the incorporation of active biomolecular components, NFMS can precisely replicate the nanostructure and biochemical cues essential for osteogenesis promotion. Furthermore, NFMS exhibit versatile properties, including tunable morphology, mechanical strength, and controlled release kinetics, augmenting their suitability for tailored bone tissue engineering applications. NFMS enhance cell recruitment, attachment, and proliferation, while promoting osteogenic differentiation and mineralization, thereby accelerating bone healing. This review highlights the pivotal role of NFMS in bone tissue engineering, elucidating their design principles and key attributes. By examining recent preclinical applications, we assess their current clinical status and discuss critical considerations for potential clinical translation. This review offers crucial insights for researchers at the intersection of biomaterials and tissue engineering, highlighting developments in this expanding field.

Peptoid-Cross-Linked Hydrogel Stiffness Modulates Human Mesenchymal Stromal Cell Immunoregulatory Potential in the Presence of Interferon-Gamma

Human mesenchymal stromal cell (hMSC) manufacturing requires the production of large numbers of therapeutically potent cells. Licensing with soluble cytokines improves hMSC therapeutic potency by enhancing secretion of immunoactive factors but typically decreases proliferative ability. Soft hydrogels, however, have shown promise for boosting immunomodulatory potential, which may compensate for decreased proliferation. Here, hydrogels are cross-linked with peptoids of different secondary structures to generate substrates of various bulk stiffnesses but fixed network connectivity. Secretions of interleukin 6, monocyte chemoattractive protein-1, macrophage colony-stimulating factor, and vascular endothelial growth factor are shown to depend on hydrogel stiffness in the presence of interferon gamma (IFN-γ) supplementation, with soft substrates further improving secretion. The immunological function of these secreted cytokines is then investigated via coculture of hMSCs seeded on hydrogels with primary peripheral blood mononuclear cells (PBMCs) in the presence and absence of IFN-γ. Cocultures with hMSCs seeded on softer hydrogels show decreased PBMC proliferation with IFN-γ. To probe possible signaling pathways, immunofluorescent studies probe the nuclear factor kappa B pathway and demonstrate that IFN-γ supplementation and softer hydrogel mechanics lead to higher activation of this pathway. Overall, these studies may allow for production of more efficacious therapeutic hMSCs in the presence of IFN-γ.

Dehydrocostus lactone (DHC) promotes osteoblastic differentiation and mineralization through p38/RUNX-2 signaling

Dysregulation of osteoblastic differentiation is an important risk factor of osteoporosis, the therapy of which is challenging. Dehydrocostus lactone (DHC), a sesquiterpene isolated from medicinal plants, has displayed anti-inflammatory and antitumor properties. In this study, we investigated the effects of DHC on osteoblastic differentiation and mineralization of MC3T3-E1 cells. Interestingly, we found that DHC increased the expression of marker genes of osteoblastic differentiation, such as alkaline phosphatase (ALP), osteocalcin (OCN), and osteopontin (OPN). Additionally, DHC increased the expressions of collagen type I alpha 1 (Col1a1) and collagen type I alpha 2 (Col1a2). We also demonstrate that DHC increased ALP activity. Importantly, the Alizarin Red S staining assay revealed that DHC enhanced osteoblastic differentiation of MC3T3-E1 cells. Mechanistically, it is shown that DHC increased the expression of Runx-2, a central regulator of osteoblastic differentiation. Treatment with DHC also increased the levels of phosphorylated p38, and its blockage using its specific inhibitor SB203580 abolished the effects of DHC on runt-related transcription factor 2 (Runx-2) expression and osteoblastic differentiation, suggesting the involvement of p38. Based on these findings, we concluded that DHC might possess a capacity for the treatment of osteoporosis by promoting osteoblastic differentiation.

The structural pathology for hypophosphatasia caused by malfunctional tissue non-specific alkaline phosphatase

Hypophosphatasia (HPP) is a metabolic bone disease that manifests as developmental abnormalities in bone and dental tissues. HPP patients exhibit hypo-mineralization and osteopenia due to the deficiency or malfunction of tissue non-specific alkaline phosphatase (TNAP), which catalyzes the hydrolysis of phosphate-containing molecules outside the cells, promoting the deposition of hydroxyapatite in the extracellular matrix. Despite the identification of hundreds of pathogenic TNAP mutations, the detailed molecular pathology of HPP remains unclear. Here, to address this issue, we determine the crystal structures of human TNAP at near-atomic resolution and map the major pathogenic mutations onto the structure. Our study reveals an unexpected octameric architecture for TNAP, which is generated by the tetramerization of dimeric TNAPs, potentially stabilizing the TNAPs in the extracellular environments. Moreover, we use cryo-electron microscopy to demonstrate that the TNAP agonist antibody (JTALP001) forms a stable complex with TNAP by binding to the octameric interface. The administration of JTALP001 enhances osteoblast mineralization and promoted recombinant TNAP-rescued mineralization in TNAP knockout osteoblasts. Our findings elucidate the structural pathology of HPP and highlight the therapeutic potential of the TNAP agonist antibody for osteoblast-associated bone disorders.

Generation of bicistronic Dmp1-Cre knock-in mice using a self-cleaving 2A peptide

INTRODUCTION

The conditional manipulation of genes using the Cre recombinase-locus of crossover in P1 (Cre/loxP) system is an important tool for revealing gene functions and cell lineages in vivo. The outcome of this method is dependent on the performance of Cre-driver mouse strains. In most cases, Cre knock-in mice show better specificity than randomly inserted Cre transgenic mice. However, following knock-in, the expression of the original gene replaced by Cre is lost.

MATERIALS AND METHODS

We generated a new differentiated osteoblast- and osteocyte-specific Cre knock-in mouse line that carries the viral T2A sequence encoding a 2A self-cleaving peptide at the end of the coding region of the dentin matrix protein 1 (Dmp1) gene accompanied by the Cre gene.

RESULTS

We confirmed that Dmp1-T2A-Cre mice showed high Cre expression in osteoblasts, osteocytes, odontoblasts, and periodontal ligament cells and that the 2A self-cleaving peptide efficiently produced both Dmp1 and Cre proteins. Furthermore, unlike the Dmp1 knockout mice, homozygous Dmp1-T2A-Cre mice showed no skeletal abnormalities. Analysis using the Cre reporter strain confirmed differentiated osteoblast- and osteocyte-specific Cre-mediated recombination in the skeleton. Furthermore, recombination was also detected in some nuclei of skeletal muscle cells, spermatocytes, and intestinal cells.

CONCLUSION

2A-Cre functions effectively in vivo, and Dmp1-T2A-Cre knock-in mice are a useful tool for studying the functioning of various genes in hard tissues.

Collagen/κ-Carrageenan-Based Scaffolds as Biomimetic Constructs for In Vitro Bone Mineralization Studies

Tissue engineering offers attractive strategies to develop three-dimensional scaffolds mimicking the complex hierarchical structure of the native bone. The bone is formed by cells incorporated in a molecularly organized extracellular matrix made of an inorganic phase, called biological apatite, and an organic phase mainly made of collagen and noncollagenous macromolecules. Although many strategies have been developed to replicate the complexity of bone at the nanoscale in vitro, a critical challenge has been to control the orchestrated process of mineralization promoted by bone cells in vivo and replicate the anatomical and biological properties of native bone. In this study, we used type I collagen to fabricate mineralized scaffolds mimicking the microenvironment of the native bone. The sulfated polysaccharide κ-carrageenan was added to the scaffolds to fulfill the role of noncollagenous macromolecules in the organization and mineralization of the bone matrix and cell adhesion. Scanning electron microscopy images of the surface of the collagen/κ-carrageenan scaffolds showed the presence of a dense and uniform network of intertwined fibrils, while images of the scaffolds' lateral sides showed the presence of collagen fibrils with a parallel alignment, which is characteristic of dense connective tissues. MC3T3-E1 osteoblasts were cultured in the collagen scaffolds and were viable after up to 7 days of culture, both in the absence and in the presence of κ-carrageenan. The presence of κ-carrageenan in the collagen scaffolds stimulated the maturation of the cells to a mineralizing phenotype, as suggested by the increased expression of key genes related to bone mineralization, including alkaline phosphatase (Alp), bone sialoprotein (Bsp), osteocalcin (Oc), and osteopontin (Opn), as well as the ability to mineralize the extracellular matrix after 14 and 21 days of culture. Taken together, the results described in this study shed light on the potential use of collagen/κ-carrageenan scaffolds to study the role of the structural organization of bone-mimetic synthetic matrices in cell function.

A novel peptide isolated from Catla skin collagen acts as a self-assembling scaffold promoting nucleation of calcium-deficient hydroxyapatite nanocrystals

Catla collagen hydrolysate (CH) was fractionated by chromatography and each fraction was subjected to HA nucleation, with the resultant HA-fraction composites being scored based on the structural and functional group of the HA formed. The process was repeated till a single peptide with augmented HA nucleation capacity was obtained. The peptide (4.6 kDa), exhibited high solubility, existed in polyproline-II conformation and displayed a dynamic yet stable hierarchical self-assembling property. The 3D modelling of the peptide revealed multiple calcium and phosphate binding sites and a high propensity to self-assemble. Structural analysis of the peptide-HA crystals revealed characteristic diffraction planes of HA with mineralization following the (002) plane, retention of the self-assembled hierarchy of the peptide and intense ionic interactions between carboxyl groups and calcium. The peptide-HA composite crystals were mostly of 25-40 nm dimensions and displayed 79% mineralization, 92% crystallinity, 39.25% porosity, 12GPa Young's modulus and enhanced stability in physiological pH. Cells grown on peptide-HA depicted faster proliferation rates and higher levels of osteogenic markers. It was concluded that the prerequisite for HA nucleation by a peptide included: a conserved sequence with a unique charge topology allowing calcium chelation and its ability to form a dynamic self-assembled hierarchy for crystal propagation.

RUNX2 and ALP expression in osteoblast cells exposed by PMMA-HAp combination: An in vitro study

Objective

To observe the expression of Runt-Related Transcription Factors 2 (RUNX2) and Alkaline Phosphatase (ALP) markers in osteoblast cell cultures exposed to Polymethylmethacrylate (PMMA) combined with hydroxyapatite (HAp) material to improve osteointegration of bone implants.

Methods

Sample of PMMA and HAp materials with a mixture of PMMA with HAp made from limestone as natural source which processed through Balai Besar Keramik (HApBBK) in the first group and a mixture of PMMA with HAp made from bovine bone which processed through Good Manufacturing Practice (HApGMP) in the second group. Twenty-four fetal rat calvarie osteoblast cell cultures were randomly divided into 6 groups: 7- and 14-day control group, 7 and 14 days PMMA-HApGMP group, 7 and 14 days PMMA-HApBBK group. The expression of RUNX2 and ALP was seen by immunocytochemical examination.

Result

The one-way ANOVA with a significance value of 0.000 (p < 0.05). There was an increase in RUNX2 and ALP expressions on both PMMA-HApBBK and PMMA-HApGMP groups on days 7 and 14 in osteoblast cell cultures.

Conclusion

The PMMA-HApBBK and PMMA-HApGMP showed an increase in the RUNX2 and ALP expression in osteoblast cell cultures which indicates a potential increase of osseointegration of bone implants.

Biocompatibility and osseointegration properties of a novel high strength and low modulus β- Ti10Mo6Zr4Sn3Nb alloy

Introduction: Ti6Al4V titanium alloy is widely used in producing orthopedic and maxillofacial implants, but drawbacks include high elastic modulus, poor osseointegration performance, and toxic elements. A new medical titanium alloy material with better comprehensive performance is urgently needed in the clinic. Methods: Ti10Mo6Zr4Sn3Nb titanium alloy (referred to as Ti-B12) is a unique medical ß titanium alloy material developed by us. The mechanical properties of Ti-B12 depict that it has advantages, such as high strength, low elastic modulus, and fatigue resistance. In our study, the biocompatibility and osseointegration properties of Ti-B12 titanium alloy are further studied to provide theoretical guidance for its clinical transformation. Results and Discussion: The titanium alloy Ti-B12 displays no significant effect on MC3T3-E1 cell morphology, proliferation, or apoptosis in vitro. Neither Ti-B12 titanium alloy nor Ti6Al4V titanium alloy depicts a significant difference (p > 0.05); Ti-B12 material extract injected into the abdominal cavity of mice does not cause acute systemic toxicity. The skin irritation test and intradermal irritation test reveal that Ti-B12 does not cause skin allergic reactions in rabbits. Compared to Ti6Al4V, Ti-B12 titanium alloy material has more advantages in promoting osteoblast adhesion and ALP secretion (p < 0.05). Although there is no significant difference in OCN and Runx2 gene expression between the three groups on the 7th and 14th days of differentiation induction (p > 0.05), the expression of Ti-B12 group is higher than that of Ti6Al4V group and blank control group. Furthermore, the rabbit in vivo test present that 3 months after the material is implanted in the lateral epicondyle of the rabbit femur, the Ti-B12 material fuses with the surrounding bone without connective tissue wrapping. This study confirms that the new β-titanium alloy Ti-B12 not only has low toxicity and does not cause rejection reaction but also has better osseointegration performance than the traditional titanium alloy Ti6Al4V. Therefore, Ti-B12 material is expected to be further promoted in clinical practice.

Biocompatibility and osteointegration capability of β-TCP manufactured by stereolithography 3D printing: In vitro study

Beta-tricalcium phosphate (β-TCP) bioceramics have an inorganic composition similar to the human bone. While conventional methods can only produce ceramic scaffolds with poor controllability, the advancement of 3D-printing, especially stereolithography, made it possible to manufacture controllable, highly precise, micropore ceramic scaffolds. In this study, the stereolithography was applied to produce β-TCP bioceramics, while ZrO₂, Al₂O₃, Ti6Al4V, and polyetheretherketone (PEEK) were used as controls. Phase analysis, water contact angle tests, and Micro-CT were applied to evaluate the surface properties and scaffold. Hemolytic toxicity, cell proliferation, and morphological assessment were performed to evaluate the biocompatibility. Alkaline phosphatase (ALP) level, mineralization, and qRT-PCR were measured to evaluate the osteointegration. During the manufacturing of β-TCP, no evident impurity substance and hemolytic toxicity was found. Cells on β-TCP had good morphologies, and their proliferation capability was similar to Ti6Al4V, which was higher than the other materials. Cells on β-TCP had higher ALP levels than PEEK. The degree of mineralization was significantly higher on β-TCP. The expression of osteogenesis-related genes on β-TCP was similar to Ti6Al4V and higher than the other materials. In this study, the β-TCP produced by stereolithography had no toxicity, high accuracy, and excellent osteointegration capability, thus resulting as a good choice for bone implants.

Isolation, Identification, and Characterization of Bioactive Peptides in Human Bone Cells from Tortoiseshell and Deer Antler Gelatin

Tortoiseshell and deer antler gelatin has been used to treat bone diseases in Chinese society. A pepsin-digested gelatin peptide with osteoblast-proliferation-stimulating properties was identified via LC-MS/MS. The resulting pentapeptide, TSKYR, was presumably subjected to further degradation into TSKY, TSK, and YR fragments in the small intestine. The above four peptides were chemically synthesized. Treatment of tripeptide TSK can lead to a significant 30- and 50-fold increase in the mineralized nodule area and density in osteoblast cells and a 47.5% increase in the number of chondrocyte cells. The calcium content in tortoiseshell was relatively higher than in human soft tissue. The synergistic effects of calcium ions and the peptides were observed for changes in osteoblast proliferation and differentiation. Moreover, these peptides can enhance the expression of RUNX2, OCN, FGFR2, and FRFR3 genes in osteoblasts, and aggrecan and collagen type II in chondrocyte (patent pending).

Amorphous silica fiber matrix biomaterials: An analysis of material synthesis and characterization for tissue engineering

Silica biomaterials including Bioglass offer great biocompatibility and bioactivity but fail to provide pore and degradation features needed for tissue engineering. Herein we report on the synthesis and characterization of novel amorphous silica fiber matrices to overcome these limitations. Amorphous silica fibers were fused by sintering to produce porous matrices. The effects of sacrificial polymer additives such as polyvinyl alcohol (PVA) and cellulose fibers (CF) on the sintering process were also studied. The resulting matrices formed between sintering temperatures of 1,350–1,550 °C retained their fiber structures. The matrices presented pores in the range of 50–200 μm while higher sintering temperatures resulted in increased pore diameter. PVA addition to silica significantly reduced the pore diameter and porosity compared with silica matrices with or without the addition of CF. The PVA additive morphologically appeared to fuse the silica fibers to a greater extent and resulted in significantly higher compressive modulus and strength than the rest of the matrices synthesized. These matrices lost roughly 30% of their original mass in an in vitro degradation study over 40 weeks. All matrices absorbed 500 wt% of water and did not change in their overall morphology, size, or shape with hydration. These fiber matrices supported human mesenchymal stem cell adhesion, proliferation, and mineralized matrix production. Amorphous silica fiber biomaterials/matrices reported here are biodegradable and porous and closely resemble the native extracellular matrix structure and water absorption capacity. Extending the methodology reported here to alter matrix properties may lead to a variety of tissue engineering, implant, and drug delivery applications.

Thermal treatment of magnesium particles in polylactic acid polymer films elicits the expression of osteogenic differentiation markers and lipidome profile remodeling in human adipose stem cells

The efficacy of polylactic acid (PLA)/Magnesium (Mg)-based materials for driving stem cells toward bone tissue engineering applications requires specific Mg surface properties to modulate the interface of stem cells with the film. Here, we have developed novel PLA/Mg-based composites and explored their osteogenic differentiation potential on human adipose stem cells (hASCs). Mg-particles/polymer interface was improved by two treatments: heating in oxidative atmosphere (TT) and surface modification with a compatibilizer (PEI). Different contents of Mg particles were dispersed in PLA and composite surface and bulk properties, protein adsorption, stem cell-PLA/Mg interactions, osteogenic markers expressions, and lipids composition profile were evaluated. Mg particles were uniformly distributed on the surface and in the bulk PLA polymer. Improved and modulated particle-polymer adhesion was observed in Mg particle-treated composites. After 21 days in canonical growth culture conditions, hASCs on PLA/MgTT displayed the highest expression of the general osteogenic markers, RUNX2, SSP1, and BGLAP genes, Alkaline Phosphatase, type I Collagen, Osteopontin, and Calcium deposits. Moreover, by LC/MS QTOF mass-spectrophotometry lipidomic analysis, we found in PLA/MgTT-cells, for the first time, a remodeling of the lipid classes composition associated with the osteogenic differentiation. We ascribed these results to MgTT characteristics, which improve Mg availability and composite osteoinductive performance.

3D bioprinting of in situ vascularized tissue engineered bone for repairing large segmental bone defects

Large bone defects remain an unsolved clinical challenge because of the lack of effective vascularization in newly formed bone tissue. 3D bioprinting is a fabrication technology with the potential to create vascularized bone grafts with biological activity for repairing bone defects. In this study, vascular endothelial cells laden with thermosensitive bio-ink were bioprinted in situ on the inner surfaces of interconnected tubular channels of bone mesenchymal stem cell-laden 3D-bioprinted scaffolds. Endothelial cells exhibited a more uniform distribution and greater seeding efficiency throughout the channels. In vitro, the in situ bioprinted endothelial cells can form a vascular network through proliferation and migration. The in situ vascularized tissue-engineered bone also resulted in a coupling effect between angiogenesis and osteogenesis. Moreover, RNA sequencing analysis revealed that the expression of genes related to osteogenesis and angiogenesis is upregulated in biological processes. The in vivo 3D-bioprinted in situ vascularized scaffolds exhibited excellent performance in promoting new bone formation in rat calvarial critical-sized defect models. Consequently, in situ vascularized tissue-engineered bones constructed using 3D bioprinting technology have a potential of being used as bone grafts for repairing large bone defects, with a possible clinical application in the future.

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3D bioprinting was used to fabricate in situ vascularized tissue engineered bone.

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In situ bioprinted endothelial cells exhibited uniform distribution and greater seeding efficiency.

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3D-bioprinted scaffold produced coupling between angiogenesis and osteogenesis.

Transcriptome Analysis Reveals Modulation of Human Stem Cells from the Apical Papilla by Species Associated with Dental Root Canal Infection

Interaction of oral bacteria with stem cells from the apical papilla (SCAP) can negatively affect the success of regenerative endodontic treatment (RET). Through RNA-seq transcriptomic analysis, we studied the effect of the oral bacteria Fusobacterium nucleatum and Enterococcus faecalis, as well as their supernatants enriched by bacterial metabolites, on the osteo- and dentinogenic potential of SCAPs in vitro. We performed bulk RNA-seq, on the basis of which differential expression analysis (DEG) and gene ontology enrichment analysis (GO) were performed. DEG analysis showed that E. faecalis supernatant had the greatest effect on SCAPs, whereas F. nucleatum supernatant had the least effect (Tanimoto coefficient = 0.05). GO term enrichment analysis indicated that F. nucleatum upregulates the immune and inflammatory response of SCAPs, and E. faecalis suppresses cell proliferation and cell division processes. SCAP transcriptome profiles showed that under the influence of E. faecalis the upregulation of VEGFA, Runx2, and TBX3 genes occurred, which may negatively affect the SCAP's osteo- and odontogenic differentiation. F. nucleatum downregulates the expression of WDR5 and TBX2 and upregulates the expression of TBX3 and NFIL3 in SCAPs, the upregulation of which may be detrimental for SCAPs' differentiation potential. In conclusion, the present study shows that in vitro, F. nucleatum, E. faecalis, and their metabolites are capable of up- or downregulating the expression of genes that are necessary for dentinogenic and osteogenic processes to varying degrees, which eventually may result in unsuccessful RET outcomes. Transposition to the clinical context merits some reservations, which should be approached with caution.

Delivering Multifunctional Peptide-Conjugated Gene Carrier/miRNA-218 Complexes from Monodisperse Microspheres for Bone Regeneration

MicroRNAs (miRNAs) play a pivotal role in regulating gene expression and are considered new molecular targets in bone tissue engineering. However, effective delivery of miRNAs to the defect areas and transfection of the miRNAs into osteogenic progenitor cells has been an obstacle in the application. In this work, miRNA-218 (miR-218) was used as an osteogenic miRNA regulator, and a multifunctional peptide-conjugated gene carrier poly(lactide-co-glycolide)-g-polyethylenimine-b-polyethylene glycol-R9-G4-IKVAVW (PPP-RGI) was developed to condense with miR-218 to form PPP-RGI/miR-218 complexes that were further encapsulated into monodisperse injectable microspheres for enhanced bone regeneration. The PPP-RGI was synthesized via conjugating R9-G4-IKVAVW (RGI), a multifunctional peptide, onto poly(lactide-co-glycolide)-g-polyethylenimine-b-polyethylene glycol (PPP). A microfluidic and synchronous photo-cross-linking process was further developed to encapsulate the PPP-RGI/miR-218 complexes into monodisperse gelatin methacryloyl microspheres. The monodisperse microspheres controlled the delivery of PPP-RGI/miR-218 to the designated defect site, and PPP-RGI facilitated the transfection of miR-218 into osteogenic progenitor cells. An in vivo calvarial defect model showed that the PPP-RGI/miR-218-loaded microspheres significantly enhanced bone tissue regeneration. This work provides a novel approach to effectively deliver miRNA and transfect targeting cells in vivo for advanced regenerative therapies.

Epimedin C Alleviates Glucocorticoid-Induced Suppression of Osteogenic Differentiation by Modulating PI3K/AKT/RUNX2 Signaling Pathway

Secondary osteoporosis is triggered mostly by glucocorticoid (GC) therapy. Dexamethasone (DEX) was reported to inhibit osteogenic differentiation in zebrafish larvae and MC3T3-E1 cells in prior research. In this research, we primarily examined the protective impacts of epimedin C on the osteogenic inhibition impact of MC3T3-E1 cells and zebrafish larvae mediated by DEX. The findings illustrated no apparent toxicity for MC3T3-E1 cells after administering epimedin C at increasing dosages from 1 to 60 μM and no remarkable proliferation in MC3T3-E1 cells treated using DEX. In MC3T3-E1 cells that had been treated using DEX, we discovered that epimedin C enhanced alkaline phosphatase activities and mineralization. Epimedin C could substantially enhance the protein expression of osterix (OSX), Runt-related transcription factor 2 (RUNX2), and alkaline phosphatase (ALPL) in MC3T3-E1 cells subjected to DEX treatment. Additionally, epimedin C stimulated PI3K and AKT signaling pathways in MC3T3-E1 cells that had been treated using DEX. Furthermore, in a zebrafish larvae model, epimedin C was shown to enhance bone mineralization in DEX-mediated bone impairment. We also found that epimedin C enhanced ALPL activity and mineralization in MC3T3-E1 cells treated using DEX, which may be reversed by PI3K inhibitor (LY294002). LY294002 can also reverse the protective impact of epimedin C on DEX-mediated bone impairment in zebrafish larval. These findings suggested that epimedin C alleviated the suppressive impact of DEX on the osteogenesis of zebrafish larval and MC3T3-E1 cells via triggering the PI3K and AKT signaling pathways. Epimedin C has significant potential in the development of innovative drugs for the treatment of glucocorticoid-mediated osteoporosis.

Molybdenum disulfide nanosheet/polyimide composites with improved tribological performances, surface properties, antibacterial effects and osteogenesis for facilitating osseointegration

Polymeric biocomposites display some advantages over metal or ceramic biomaterials, and are regarded as a promising candidate for artificial joint application. Herein, molybdenum disulfide (MD) nanosheets were prepared and incorporated into polyimide (PI) to form MD/PI composites with a MD content of 20 wt% (PM20) and 40 wt% (PM40). The results revealed that incorporation of MD nanosheets obviously improved the tribological performances, surface properties (e.g., roughness, wettability and surface energy) and protein absorption of the composites, which enhanced with the increase of MD content. In addition, the composites containing MD nanosheets exhibited antibacterial effects, and the antibacterial effects of PM40 were higher than those of PM20 and PI. PM40 significantly stimulated the cellular responses of rat bone mesenchymal stem cells in vitro, which was better than PM20 and PI. Furthermore, PM40 remarkably accelerated osteogenesis and osseointegration in vivo, which was better than PM20 and PI. In summary, the MD content in composites played pivotal roles in improving not only tribological performances, surface properties, antibacterial effects and cellular response in vitro but also osteogenesis and osseointegration in vivo. As a result, PM40 with high MD content exhibited excellent osteogenic bioactivity and antibacterial effects, which would have great potential for artificial joint applications.

Curcumin-loaded carrageenan nanoparticles: Fabrication, characterization, and assessment of the effects on osteoblasts mineralization

The use of Curcumin (CR) as a bioactive molecule to prevent and treat inflammation- related diseases is widespread. However, the high hydrophobicity hinders the in vivo bioavailability of CR, reducing its therapeutic index. In the present study, we described the use of nanoparticles (NPs) made of kappa-carrageenan (κ-Carr), a sulphated polysaccharide, as cost-effective, biodegradable and biocompatible CR carriers. CR-loaded κ-Carr nanoparticles (CR@Carr NPs) were prepared by mixing a κ-Carr aqueous solution with a CR ethanolic solution. The final suspension was centrifuged and re-suspended in phosphate buffer solution. The NPs' size was tuned by changing the concentration of the polysaccharide. CR@CarrNPs displayed high CR incorporation efficiency (~80 wt%) and a double-exponential curve of CR release at physiological conditions (37 °C and pH 7.4) with a cumulative drug release of 32 wt% after 24 h for the smaller NP. Our results also showed that CR@CarrNPs were not cytotoxic to osteoblasts at concentrations up to 1 μM. Confocal microscopy images revealed the internalization of CR by the cells guided by the NPs. Cells treated with CR@CarrNPs exhibited higher activity of alkaline phosphatase and higher expression of the main osteogenic genes (Sp7, Col1 and Runx2), and mineralized the extracellular matrix in a higher extent compared to the cells cultivated in absence of the NPs. We posited that these effects were related to the NP-driven internalization of CR by osteoblasts. Our study sheds light on the possible use of CR@CarrNPs as efficient and safe therapeutic tools for the treatment of bone-related diseases.

bFGF-Loaded Mesoporous Silica Nanoparticles Promote Bone Regeneration Through the Wnt/β-Catenin Signalling Pathway

Background

Bone defects remain an unsolved clinical problem due to the lack of effective osteogenic induction protocols. Nanomaterials play an important role in bone defect repair by stimulating osteogenesis. However, constructing an effective bioactive nanomaterial remains a substantial challenge.

Methods

In this study, mesoporous silica nanoparticles (MSNs) were prepared and used as nanocarriers for basic fibroblast growth factor (bFGF). The characteristics and biological properties of the synthetic bFGF@MSNs were tested. The osteogenic effects of the particles on the behavior of MC3T3-E1 cells were investigated in vitro. In addition, the differentially expressed genes during induction of osteogenesis were analyzed by transcriptomic sequencing. Radiological and histological observations were carried out to determine bone regeneration capability in a distal femur defect model.

Results

Achieving bFGF sustained release, bFGF@MSNs had uniform spherical morphology and good biocompatibility. In vitro osteogenesis induction experiments showed that bFGF@MSNs exhibited excellent osteogenesis performance, with upregulation of osteogenesis-related genes (RUNX2, OCN, Osterix, ALP). Transcriptomic sequencing revealed that the Wnt/β-catenin signalling pathway could be activated in regulation of biological processes. In vivo, bone defect repair experiments showed enhanced bone regeneration, as indicated by radiological and histological analysis, after the application of bFGF@MSNs.

Conclusion

bFGF@MSNs can promote bone regeneration by activating the Wnt/β-catenin signalling pathway. These particles are expected to become a potential therapeutic bioactive material for clinical application in repairing bone defects in the future.

Cellular studies and sustained drug delivery via nanostructures fabricated on 3D printed porous Neovius lattices of Ti6Al4V ELI

Site-specific drug delivery has the potential to reduce drug dosage by 3 to 5-folds. Given the propensity of drugs used in the treatment of tuberculosis and cancers, the increased drug dosages via oral ingestion for several months to a few years of medication is often detrimental to the health of patients. In this study, the sustained delivery of drugs with multiscale structured novel Neovius lattices was achieved. 3D Neovius Open Cell Lattices (NOCL) with porosities of 40, 45, and 50 % were fabricated layer-by-layer on the laser bed fusion process. Micron-sized Ti6Al4V Eli powder was used for 3D printing. The Young's modulus achieved from the novel Neovius lattices were in the range of 1.2 to 1.6 GPa, which is comparable to human cortical bone and helps to improve implant failure due to the stress shielding effect. To provide sustained drug delivery, nanotubes (NTs) were fabricated on NOCLs via high-voltage anodisation. The osteogenic agent icariin was loaded onto the NOCL-NT samples and their release profiles were studied for 7 days. A significantly steady and slow release rate of 0.05% per hour of the drug was achieved using NOCL-NT. In addition, the initial burst release of NOCL-NT was 4 fold lower than that of the open-cell lattices without nanotubes. Cellular studies using MG63 human osteoblast-like cells were performed to determine their biocompatibility and osteogenesis which were analysed using Calcein AM staining and Alamar Blue after 1, 5, and 7 days. 3D printed NOCL samples with NTs and with Icariin loaded NTs demonstrated a significant increase in cell proliferation as compared to as printed NOCL samples.

LncRNA MIAT can regulate the proliferation, apoptosis, and osteogenic differentiation of bone marrow-derived mesenchymal stem cells by targeting miR-150-5p

Osteoporosis (OP) is a systemic bone metabolic disease with complicated pathogenesis and is difficult to cure clinically. The regulatory mechanisms of OP are needed to be further investigated. In the present study, we focused on the role of myocardial infarction-associated transcript (MIAT) in OP development and examined the underlying mechanism. The serum expression levels of MIAT in samples from patients with OP and healthy controls were compared using quantitative reverse transcription-PCR (qRT-PCR). The dual-luciferase reporter assay was used to confirm the relationship between MIAT and its potential target microRNA, i.e., miR-150-5p. Moreover, bone marrow-derived mesenchymal stem cells (BMSCs) were cultured and transfected with MIAT shRNA, with or without miR-150-5p inhibitor. EdU staining and colony formation analysis were performed to determine the proliferation ability of these cells. Furthermore, the TUNEL assay and flow cytometry were used to assess BMSC apoptosis. Finally, RT-PCR and Western blot assays were employed to assess the expression of osteogenic differentiation biomarkers. Compared with controls, the expression of MIAT was significantly increased, whereas that of miR-150-5p was markedly decreased in patients with OP. MIAT and miR-150-5p expression levels exhibited a strong negative correlation. Furthermore, osteogenic differentiation indicators were suppressed in serum of OP patients. MIAT was downregulated, and miR-150-5p was upregulated in induced to osteogenic differentiation BMSCs. Furthermore, downregulation of MIAT dramatically promoted osteogenic differentiation, increased proliferation, and inhibited apoptosis in BMSCs; miR-150-5p inhibitor abrogated the effects of MIAT. In conclusion, lncRNA MIAT can regulate the proliferation, apoptosis, and osteogenic differentiation of BMSCs.

Mineralizing Gelatin Microparticles as Cell Carrier and Drug Delivery System for siRNA for Bone Tissue Engineering

The local release of complexed siRNA from biomaterials opens precisely targeted therapeutic options. In this study, complexed siRNA was loaded to gelatin microparticles cross-linked (cGM) with an anhydride-containing oligomer (oPNMA). We aggregated these siRNA-loaded cGM with human mesenchymal stem cells (hMSC) to microtissues and stimulated them with osteogenic supplements. An efficient knockdown of chordin, a BMP-2 antagonist, caused a remarkably increased alkaline phosphatase (ALP) activity in the microtissues. cGM, as a component of microtissues, mineralized in a differentiation medium within 8–9 days, both in the presence and in the absence of cells. In order to investigate the effects of our pre-differentiated and chordin-silenced microtissues on bone homeostasis, we simulated in vivo conditions in an unstimulated co-culture system of hMSC and human peripheral blood mononuclear cells (hPBMC). We found enhanced ALP activity and osteoprotegerin (OPG) secretion in the model system compared to control microtissues. Our results suggest osteoanabolic effects of pre-differentiated and chordin-silenced microtissues.

Exosome-functionalized magnesium-organic framework-based scaffolds with osteogenic, angiogenic and anti-inflammatory properties for accelerated bone regeneration

Exosomes derived from human adipose-derived stem cells (hADSCs-Exos) have shown potential as an effective therapeutic tool for repairing bone defects. Although metal-organic framework (MOF) scaffolds are promising strategies for bone tissue regeneration, their potential use for exosome loading remains unexplored. In this study, motivated by the potential advantages of hADSCs-Exos and Mg-GA MOF, we designed and synthesized an exosome-functionalized cell-free PLGA/Mg-GA MOF (PLGA/Exo-Mg-GA MOF) scaffold, taking using of the benefits of hADSCs-Exos, Mg²⁺, and gallic acid (GA) to construct unique nanostructural interfaces to enhance osteogenic, angiogenic and anti-inflammatory capabilities simultaneously. Our in vitro work demonstrated the beneficial effects of PLGA/Exo-Mg-GA MOF composite scaffolds on the osteogenic effects in human bone marrow-derived mesenchymal stem cells (hBMSCs) and angiogenic effects in human umbilical endothelial cells (HUVECs). Slowly released hADSCs-Exos from composite scaffolds were phagocytosed by co-cultured cells, stabilized the bone graft environment, ensured blood supply, promoted osteogenic differentiation, and accelerated bone reconstruction. Furthermore, our in vivo experiments with rat calvarial defect model showed that PLGA/Exo-Mg-GA MOF scaffolds promoted new bone formation and satisfactory osseointegration. Overall, we provide valuable new insights for designing exosome-coated nanocomposite scaffolds with enhanced osteogenesis property.

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PLGA/Exo-Mg-GA MOF scaffolds with nanostructures were synthesized, on which exosomes were densely deposited on the above scaffolds.

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Composite scaffolds with exosomes can actualize the slow release of exosomes, Mg ions and gallic acid.

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PLGA/Exo-Mg-GA MOF scaffolds exhibit great biocompatibility and osteogenic differentiation of hBMSCs.

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PLGA/Exo-Mg-GA MOF scaffolds have excellent osteogenic, pro-angiogenic and anti-inflammatory activity.

Therapeutic Mechanism of Chinese Medicine on the Healing of Early and Middle Fractures in Rabbits Under the Expression Level of Bone Morphogenetic Protein-2 (BMP-2) in Bone Tissue

In order to explore the therapeutic mechanism of Chinese medicine on the healing of rabbits early and middle fractures, a rabbit fracture model was established in this study. The study was divided into several groups, i.e., treatment group (TG) (fed with Chinese medicine Capsule) and control group (CG) (fed with normal saline (NS)). The materials were collected at 1, 3, and 5 weeks after the start of the experiment for analysis. The experiment content included: callus Hematoxylin-Eosin staining (HE staining); Bone Morphogenetic protein-2 (BMP-2) protein level detection; Type I and type II bone collagen (BC) detection; and serum biochemical factors detection. The experimental results showed that the formation of callus in the TG was better than in the CG; the BMP-2 protein expression level in the TG was higher than in the CG, and there were statistically significant differences (SSDs); the type I and type II BC levels in the TG were higher than the CG, there were SSDs; the levels of serum calcium (SC), phosphorus ion (PI), and alkaline phosphatase (ALP) in the TG were also higher than in the CG, and there were SSDs.

Tissue-Nonspecific Alkaline Phosphatase, a Possible Mediator of Cell Maturation: Towards a New Paradigm

Alkaline phosphatase (ALP) is a ubiquitous membrane-bound glycoprotein capable of providing inorganic phosphate by catalyzing the hydrolysis of organic phosphate esters, or removing inorganic pyrophosphate that inhibits calcification. In humans, four forms of ALP cDNA have been cloned, among which tissue-nonspecific ALP (TNSALP) (TNSALP) is widely distributed in the liver, bone, and kidney, making it an important marker in clinical and basic research. Interestingly, TNSALP is highly expressed in juvenile cells, such as pluripotent stem cells (i.e., embryonic stem cells and induced pluripotent stem cells (iPSCs)) and somatic stem cells (i.e., neuronal stem cells and bone marrow mesenchymal stem cells). Hypophosphatasia is a genetic disorder causing defects in bone and tooth development as well as neurogenesis. Mutations in the gene coding for TNSALP are thought to be responsible for the abnormalities, suggesting the essential role of TNSALP in these events. Moreover, a reverse-genetics-based study using mice revealed that TNSALP is important in bone and tooth development as well as neurogenesis. However, little is known about the role of TNSALP in the maintenance and differentiation of juvenile cells. Recently, it was reported that cells enriched with TNSALP are more easily reprogrammed into iPSCs than those with less TNSALP. Furthermore, in bone marrow stem cells, ALP could function as a "signal regulator" deciding the fate of these cells. In this review, we summarize the properties of ALP and the background of ALP gene analysis and its manipulation, with a special focus on the potential role of TNSALP in the generation (and possibly maintenance) of juvenile cells.

The effects of Omarigliptin on promoting osteoblastic differentiation

Osteoporosis significantly impacts the normal life of the elderly and is reported to be closely related to dysfunction of osteoblastic differentiation. Runt-related transcription factor-2 (Runx2) is a critical transcriptional factor involved in the regulation of osteoblast differentiation. Omarigliptin is a novel dipeptidyl peptidase-4 (DDP-4) inhibitor and this study proposes to probe into its possible therapeutic function against Osteoporosis by investigating its impacts on osteoblastic differentiation. Osteogenic medium was used to induce osteoblastic differentiation in MC3T3‑E1 cells, and was verified by the increased alkaline phosphatase (ALP) activity, enhanced mineralization, and promoted expression level of osteoblastic differentiation-related factors, including bone morphogenetic protein-2 (BMP-2), ALP, osteocalcin (Ocn), collagen type I alpha 1 (Col1a1), Collagen Type I alpha 2 (Col1a2), Runx2, osterix (Sp7), fibroblast growth factor receptor 2 (Fgfr2), and fibroblast growth factor receptor 3 (Fgfr3), accompanied by the activation of the p38 and Akt pathways. After treatment with Omarigliptin, the ALP activity and mineralization were further promoted, accompanied by the further upregulation of osteoblastic differentiation-related factors, and activation of the p38 and Akt pathways. Lastly, Omarigliptin-induced osteoblastic differentiation, promoted ALP activity, and increased expression levels of Sp7, Fgfr2, Fgfr3, BMP-2, Ocn, ALP, Col1a1, and Col1a2, in the osteogenic medium- cultured MC3T3‑E1 cells were dramatically abolished by the knockdown of Runx2. Taken together, our data reveal that Omarigliptin promoted osteoblastic differentiation by regulating Runx2.

Although Anatomically Micrometers Apart: Human Periodontal Ligament Cells Are Slightly More Active in Bone Remodeling Than Alveolar Bone Derived Cells

The periodontal ligament (PDL) and the alveolar bone are part of the periodontium, a complex structure that supports the teeth. The alveolar bone is continuously remodeled and is greatly affected by several complex oral events, like tooth extraction, orthodontic movement, and periodontitis. Until now, the role of PDL cells in terms of osteogenesis and osteoclastogenesis has been widely studied, whereas surprisingly little is known about the bone remodeling capacity of alveolar bone. Therefore, the purpose of this study was to compare the biological character of human alveolar bone cells and PDL cells in terms of osteogenesis and osteoclastogenesis in vitro. Paired samples of PDL cells and alveolar bone cells from seven patients with compromised general and oral health were collected and cultured. Bone A (early outgrowth) and bone B (late outgrowth) were included. PDL, bone A, bone B cell cultures all had a fibroblast appearance with similar expression pattern of six mesenchymal markers. These cultures were subjected to osteogenesis and osteoclastogenesis assays. For osteoclastogenesis assays, the cells were co-cultured with peripheral blood mononuclear cells, a source for osteoclast precursor cells. The total duration of the experiments was 21 days. Osteogenesis was slightly favored for PDL compared to bone A and B as shown by stronger Alizarin red staining and higher expression of RUNX2 and Collagen I at day 7 and for ALP at day 21. PDL induced approximately two times more osteoclasts than alveolar bone cells. In line with these findings was the higher expression of cell fusion marker DC-STAMP in PDL-PBMC co-cultures compared to bone B at day 21. In conclusion, alveolar bone contains remodeling activity, but to a different extent compared to PDL cells. We showed that human alveolar bone cells can be used as an in vitro model to study bone remodeling.

An In Vitro and In Vivo Comparison of Osteogenic Differentiation of Human Mesenchymal Stromal/Stem Cells

The use of stem cells in regenerative medicine, including tissue engineering and transplantation, has generated a great deal of enthusiasm. Mesenchymal stromal/stem cells (MSCs) can be isolated from various tissues, most commonly, bone marrow but more recently adipose tissue, dental pulp, and Wharton's jelly, to name a few. MSCs display varying phenotypic profiles and osteogenic differentiating capacity depending and their site of origin. MSCs have been successfully differentiated into osteoblasts both in vitro an in vivo but discrepancies exist when the two are compared: what happens in vitro does not necessarily happen in vivo, and it is therefore important to understand why these differences occur. The osteogenic process is a complex network of transcription factors, stimulators, inhibitors, proteins, etc., and in vivo experiments are helpful in evaluating the various aspects of this osteogenic process without distractions and confounding variables. With that in mind, the results of in vitro experiments need to be carefully considered and interpreted with caution as they do not perfectly replicate the conditions found within living organisms. This is where in vivo experiments help us better understand interactions that might occur in the osteogenic process that cannot be replicated in vitro. Potentially, these differences could also be exploited to develop an optimal MSC cell therapeutic product that can be used for bone disorders. There are many bone disorders, most of which cause a great deal of discomfort. Clinically acceptable protocols could be developed in which MSCs are used to aid in bone regeneration providing relief for patients with chronic pain. The aim of this review is to examine the differences between studies conducted in vitro and in vivo with regard to the osteogenic process to better define the gaps in current osteogenic research. By better understanding osteogenic differentiation, we can better define treatment strategies for various bone disorders.

Tissue-Nonspecific Alkaline Phosphatase in Central Nervous System Health and Disease: A Focus on Brain Microvascular Endothelial Cells

Tissue-nonspecific alkaline phosphatase (TNAP) is an ectoenzyme bound to the plasma membranes of numerous cells via a glycosylphosphatidylinositol (GPI) moiety. TNAP's function is well-recognized from earlier studies establishing its important role in bone mineralization. TNAP is also highly expressed in cerebral microvessels; however, its function in brain cerebral microvessels is poorly understood. In recent years, few studies have begun to delineate a role for TNAP in brain microvascular endothelial cells (BMECs)-a key component of cerebral microvessels. This review summarizes important information on the role of BMEC TNAP, and its implication in health and disease. Furthermore, we discuss current models and tools that may assist researchers in elucidating the function of TNAP in BMECs.

An activity-based fluorescent probe and its application for differentiating alkaline phosphatase activity in different cell lines

Herein, a new fluorescent probe, AE-Phos, is reported for detecting the ALP activity with the combined advantages of aggregation-induced emission (AIE) and excited state intramolecular proton transfer (ESIPT). Further detailed fluorescence experiments demonstrated that AE-Phos exhibited excellent selectivity and sensitivity, a large Stokes shift, and a fast response towards ALP. Furthermore, AE-Phos was applied to imaging the ALP activity in different cell lines quantitatively.

Incorporation of heparin/BMP2 complex on GOCS-modified magnesium alloy to synergistically improve corrosion resistance, anticoagulation, and osteogenesis

The in vivo fast degradation and poor biocompatibility are two major challenges of the magnesium alloys in the field of artificial bone materials. In this study, graphene oxide (GO) was first functionalized by chitosan (GOCS) and then immobilized on the magnesium alloy surface, finally the complex of heparin and bone morphogenetic protein 2 was incorporated on the modified surface to synergistically improve the corrosion resistance, anticoagulation, and osteogenesis. Apart from an excellent hydrophilicity after the surface modification, a sustained heparin and BMP2 release over 14 days was achieved. The corrosion resistance of the modified magnesium alloy was significantly better than that of the control according to the results of electrochemical tests. Moreover, the corrosion rate was also significantly reduced in contrast to the control. The modified magnesium alloy not only had excellent anticoagulation, but also can significantly promote osteoblast adhesion and proliferation, upregulate the expression of alkaline phosphatase and osteocalcin, and enhance mineralization. Therefore, the method of the present study can be used to simultaneously improve the corrosion resistance and biocompatibility of the magnesium alloys targeted for the orthopedic applications.

Tissue-Nonspecific Alkaline Phosphatase-A Gatekeeper of Physiological Conditions in Health and a Modulator of Biological Environments in Disease

Tissue-nonspecific alkaline phosphatase (TNAP) is a ubiquitously expressed enzyme that is best known for its role during mineralization processes in bones and skeleton. The enzyme metabolizes phosphate compounds like inorganic pyrophosphate and pyridoxal-5′-phosphate to provide, among others, inorganic phosphate for the mineralization and transportable vitamin B6 molecules. Patients with inherited loss of function mutations in the ALPL gene and consequently altered TNAP activity are suffering from the rare metabolic disease hypophosphatasia (HPP). This systemic disease is mainly characterized by impaired bone and dental mineralization but may also be accompanied by neurological symptoms, like anxiety disorders, seizures, and depression. HPP characteristically affects all ages and shows a wide range of clinical symptoms and disease severity, which results in the classification into different clinical subtypes. This review describes the molecular function of TNAP during the mineralization of bones and teeth, further discusses the current knowledge on the enzyme’s role in the nervous system and in sensory perception. An additional focus is set on the molecular role of TNAP in health and on functional observations reported in common laboratory vertebrate disease models, like rodents and zebrafish.

Qualifying Osteogenic Potency Assay Metrics for Human Multipotent Stromal Cells: TGF-β2 a Telling Eligible Biomarker

Potency assays are critical for regenerative medicine, addressing the known challenge of functional heterogeneity among human multipotent stromal cells (hMSC). Necessary laboratory cell expansion allows analysis before implantation in the patient. Levels of induction of five signature gene biomarkers, ALPL, COL1A2, DCN, ELN and RUNX2, constituted a previously reported proof-of-principle osteogenic potency assay. We tested assay modification to enhance reproducibility using six consistent bone marrow derived hBM-MSC and explored applicability to three adipose tissue derived hAT-MSC. Using a potent proprietary osteogenic induction factor, the GUSB/YWAHZ reference gene pair provided real time PCR consistency. The novel assay conditions supported the concept that genes encoding extracellular matrix proteins one week after osteogenic induction were informative. Nonetheless, relatively low induction of COL1A2 and ELN encouraged search for additional biomarkers. TGFB2 mRNA induction, important for osteogenic commitment, was readily quantifiable in both hBM-MSC and hAT-MSC. Combined with DCN, TGFB2 mRNA induction data provided discriminatory power for resolving donor-specific heterogeneity. Histomorphometric decorin and TGF-β2 protein expression patterns in eight-week heterotopic bone implants also discriminated the two non-bone-forming hMSC. We highlight progress towards prompt osteogenic potency assays, needed by current clinical trials to accelerate improved intervention with enhanced stem cell therapy for serious bone fractures.

Investigation of alpl expression and Tnap-activity in zebrafish implies conserved functions during skeletal and neuronal development

Hypophosphatasia (HPP) is a rare genetic disease with diverse symptoms and a heterogeneous severity of onset with underlying mutations in the ALPL gene encoding the ectoenzyme Tissue-nonspecific alkaline phosphatase (TNAP). Considering the establishment of zebrafish (Danio rerio) as a new model organism for HPP, the aim of the study was the spatial and temporal analysis of alpl expression in embryos and adult brains. Additionally, we determined functional consequences of Tnap inhibition on neural and skeletal development in zebrafish. We show that expression of alpl is present during embryonic stages and in adult neuronal tissues. Analyses of enzyme function reveal zones of pronounced Tnap-activity within the telencephalon and the mesencephalon. Treatment of zebrafish embryos with chemical Tnap inhibitors followed by axonal and cartilage/mineralized tissue staining imply functional consequences of Tnap deficiency on neuronal and skeletal development. Based on the results from neuronal and skeletal tissue analyses, which demonstrate an evolutionary conserved role of this enzyme, we consider zebrafish as a promising species for modeling HPP in order to discover new potential therapy strategies in the long-term.

Supplementation of nanofiltrated deep ocean water ameliorate the progression of osteoporosis in ovariectomized rat via regulating osteoblast differentiation

Magnesium was reported to be necessary for bone formation. Previous study indicated nanofiltrated deep ocean water (DOW) rich in magnesium. This study investigated the potential mechanisms of DOW in ameliorating osteoporosis. Briefly, female Sprague-Dawley rat was ovariectomized and fed with 0.35, 0.7, or 1.4 ml/kg of DOW daily for 8 weeks. In the results, DOW increased bone density, decreased trabecular bone loss, and decreased bone adiposity. DOW improved bone mass by examining structure in micro-computed tomography. About 0.35 and 0.7 ml/kg of DOW can increase protein expression of runt-related transcription factor 2 (RUNX2), an essential transcription factor for regulating osteoblast differentiation, by 9.4% or 12.9%. In human osteoblast, DOW increased the levels of osteocalcin, RUNX2, and alkaline phosphatase; all the proteins can regulate osteoblast differentiation. Considering the results of in vivo and in vitro study, DOW can ameliorate ovareictomy-caused osteoporosis via regulating the osteoblast differentiation, thereby, maintenance of bone structure. PRACTICAL APPLICATIONS: In addition to calcium, magnesium is essential to promoting the deposition of calcium in bones and regulating its transport; it may also slow the progression of osteoporosis. Nanofiltrated DOW contains abundant magnesium along with several microelements and peptides. In this study, a product was developed for decelerating osteoporosis by using an estrogen depletion model. DOW regulates osteoblast differentiation and thus prevents osteoporosis. This finding provides an alternative healthy source of bone supplements. In addition to tablets or capsules, aqueous supplements can be produced to achieve osteoporosis prevention. This finding is beneficial to the health-care industry for developing sustainable supplements.