Elevated extracellular calcium ions promote proliferation and migration of mesenchymal stem cells via increasing osteopontin expression

Injectable Composite Hydrogel Stents for Bone Defect Management with Enhanced Osteogenesis and Angiogenesis

Background

The use of autologous bone grafting is considered the most successful method for managing bone defects, particularly when utilizing cancellous bone grafts for the best outcomes. Nonetheless, the scarcity of cancellous bone presents a notable obstacle in remedying these defects. Consequently, it is essential to create reliable alternatives to cancellous bone grafts to ensure effective management of bone defects.

Methods

In this research, we created an injectable composite hydrogel stents using gelatin methacrylate (GelMA) hydrogel to mimic the collagen properties of cancellous bone, along with the inclusion of nanohydroxyapatite (nHA) to signify the inorganic element. Furthermore, we incorporated vascular endothelial growth factor (VEGF) to improve regenerative vascular capabilities. Before being implanted into rat cranium defect models, these composite hydrogel stents were co-cultured with human umbilical vein endothelial cells (HUVEC) and bone marrow mesenchymal stem cells (BMSC).

Results

The composite hydrogel stents exhibited a network structure with porosity, robust mechanical properties, and beneficial degradation traits. In the degradation phase, it steadily releases Ca²⁺ and VEGF, which encourages the proliferation, migration, and osteogenic differentiation of BMSCs from rats. Moreover, this release improves the ability of HUVECs to form tubes. Collectively, these mechanisms support the regeneration of blood vessels and bone in the cranium defect region of rats.

Conclusion

The composite hydrogel stents demonstrated excellent cytocompatibility and biological characteristics, as evidenced by its ability to enhance both osteogenesis and angiogenesis in vivo and in vitro. Consequently, it has the potential to act as an effective alternative to natural cancellous bone.

miR-125b differentially impacts mineralization in dexamethasone and calcium-treated human mesenchymal stem cells

Bone metabolism is highly regulated, and microRNAs (miRs) can contribute to this process. Among them, miR-125b is well known to enhance osteoporosis and reduce osteogenic differentiation of human mesenchymal stem cells (hMSCs). In this work, we aim to evaluate and understand how miR-125b modulates mineralization of hMSCs in two different in vitro models. Cells were cultured in dexamethasone or calcium medium and transfected with miR-125b mimic. Exposure to dexamethasone or calcium medium increased the mineralization of hMSCs and was associated with decreased miR-125b expression. Transfection of miR-125b mimic in dexamethasone-treated cells increased mineralization, while it decreased it in calcium-treated cells. Levels of osteogenic markers presented the same difference. We identified STAT3, p53, and RUNX2 as direct targets of miR-125b in hMSCs. While these targets remained identical in both treatments, their modulation after transfection was different. We showed that miR-125b mimicking differentially modulated the expression of the miR-199a/214 cluster, probably via STAT3/miR-199a/214 and p53/miR-214 pathways. In conclusion, miR-125b affinity for targets implicated in bone remodeling changed depending on the in vitro models used to induce mineralization and led to opposite physiological effects. This work shows the complexity of drugs such as dexamethasone and opens the door for new in vitro models of mineralization.

Evaluation of resorption rate-controlled calcium carbonate ceramics as a substitute bone material

Artificial bone, primarily composed of calcium carbonate, demonstrates a higher resorption rate than calcium phosphate-based counterparts, suggesting potential for early bone replacement. Animal experiments using porous calcium carbonate ceramics have demonstrated bone formation superior to commercially available artificial bone after short-term implantation. Long-term implantation has yielded suboptimal results owing to resorption of both newly formed bone and implantation material. We prepared calcium carbonate ceramics added with silica (Si-CaCO3) to regulate the resorption rate. After 12 weeks of implantation, Si-CaCO3 ceramics exhibited bone formation comparable to that of β-tricalcium phosphate (β-TCP) but less variability in the distribution of bone formation within the tissue. An in vitro dissolution test, serving as an indicator of in vivo resorption rate, revealed that Si-CaCO3 ceramics exhibited an intermediate dissolution rate between high-purity calcium carbonate and β-TCP ceramics. Silica doping in CaCO3 ceramics presents an effective approach for aligning material resorption with bone formation and growth.

Tailoring and characterization of bioactive graft material for alveolar bone preservation and regeneration in fresh extraction sockets of dog model

The objective of this study was to tailor an osteoinductive scaffold for alveolar bone regeneration and around immediately placed implants in extraction sockets of dogs. Tailored amorphous multiporous bioactive glass (TAMP -BG) was prepared and characterized for bioactivity and response of human alveolar bone marrow mesenchymal stem cells (hABMSCs). Extraction sockets of twenty-two male mongrel dogs received TAMP-BG in the right side around implant in the distal socket of the mandibular fourth premolar (P4), while the adjacent empty mesial socket of the same tooth was filled with the same graft. Autologous bone chips were used in the left side. Animals were euthanized at 1, 2, 4, 8 &12 weeks for histological and SEM analyses. SEM/EDX, FTIR and XRD analyses displayed formation of a bioactive hydroxycarbonated apatite layer. TAMP-BG significantly increased proliferation and migration of hABMSCs. Histologically, at the 1st week, advanced bone healing was shown in TAMP-BG group. At four weeks bone density was significantly higher forTAMP-BG (92.71% ± 1.71) versus control (62.92% ± 2.02) (P = 0.0001).At eight weeks, significant increase in width of buccal plate and height of lingual bony plate was observedfor TAMP-BG grafted implant.The socket orifice width significantly decreased for autologous bone from 1 to 12 weeks (P < 0.001), while it significantly increased for TAMP-BG (P = 0.03). We conclude that TAMP-BG can provide a preservative dynamic microenvironment following extraction up to three months which can be attributed to its unique physico-chemical characteristics.

The potential link between the development of Alzheimer's disease and osteoporosis

Alzheimer's disease (AD) and osteoporosis (OP) pose distinct but interconnected health challenges, both significantly impacting the aging population. AD, a neurodegenerative disorder characterized by memory impairment and cognitive decline, is primarily associated with the accumulation of abnormally folded amyloid beta (Aβ) peptides and neurofibrillary tangles in the brain. OP, a skeletal disorder marked by low bone mineral density, involves dysregulation of bone remodeling and is associated with an increased risk of fractures. Recent studies have revealed an intriguing link between AD and OP, highlighting shared pathological features indicative of common regulatory pathophysiological pathways. In this article, we elucidate the signaling mechanisms that regulate the pathology of AD and OP and offer insights into the intricate network of factors contributing to these conditions. We also examine the role of bone-derived factors in the progression of AD, underscoring the plausibility of bidirectional communication between the brain and the skeletal system. The presence of amyloid plaques in the brain of individuals with AD is akin to the accumulation of brain Aβ in vascular dementia, pointing towards the need for further investigation of shared molecular mechanisms. Moreover, we discuss the role of bone-derived microRNAs that may regulate the pathological progression of AD, providing a novel perspective on the role of skeletal factors in neurodegenerative diseases. The insights presented here should help researchers engaged in exploring innovative therapeutic approaches targeting both neurodegenerative and skeletal disorders in aging populations.

Enhancing Bone Regeneration and Osteogenic Quality by n-HA Internalized Osteoblasts Synergized with ON Protein: Mechanistic Insights

Bone scaffolds offer hope for oral jawbone repair, yet improving their osteogenic performance remains a clinical challenge. This study investigates a novel approach to enhance early bone formation and osteogenic quality by coloading hydroxyapatite (HA)─internalized osteoblasts (OHA) and osteonectin (ON) onto various scaffolds. Our findings demonstrated that the OHA could effectively facilitate the early bone regeneration by providing rapid calcium and phosphorus ion release via lysosome-mediated HA degradation, while the ON protein helps in ion deposition, cell proliferation, and matrix mineralization. When the PHA (PCL+HA) scaffold was incorporated with both the OHA and ON, the scaffold exhibited superior pro-osteogenic performance, driven by synergistic effects of rapid ion release from the OHA, slow ion release from the PHA, and upregulation of osteogenesis-related genes. The analyses of mechanisms revealed that the OHA activated MAPK and PI3K-Akt pathways, while ON stimulated calcium and Wnt signaling, collectively promoting the osteogenic potential. The strategy presented in this study paves a promising way for the development of advanced bone scaffolds to improve the bone regeneration quality.

3D printing of strontium-enriched biphasic calcium phosphate scaffolds for bone regeneration

Calcium phosphate (CaP) scaffolds doping with therapeutic ions are one of the focuses of recent bone tissue engineering research. Among the therapeutic ions, strontium stands out for its role in bone remodeling. This work reports a simple method to produce Sr-doped 3D-printed CaP scaffolds, using Sr-doping to induce partial phase transformation from β-tricalcium phosphate (β-TCP) to hydroxyapatite (HA), resulting in a doped biphasic calcium phosphate (BCP) scaffold. Strontium carbonate (SrCO3) was incorporated in the formulation of the 3D-printing ink, studying β-TCP:SrO mass ratios of 100:0, 95:5, and 90:10 (named as β-TCP, β-TCP/5-Sr, and β-TCP/10-Sr, respectively). Adding SrCO3 in the 3D-printing ink led to a slight increase in viscosity but did not affect its printability, resulting in scaffolds with a high printing fidelity compared to the computational design. Interestingly, Sr was incorporated into the lattice structure of the scaffolds, forming hydroxyapatite (HA). No residual SrO or SrCO3 were observed in the XRD patterns of any composition, and HA was the majority phase of the β-TCP/10-Sr scaffolds. The addition of Sr increased the compression strength of the scaffolds, with both β-TCP/5-Sr and β-TCP/10-Sr performing better than the β-TCP. Overall, β-TCP/5-Sr presented higher mineralized nodules and mechanical strength, while β-TCP scaffolds presented superior cell viability. The incorporation of SrCO3 in the ink formulation is a viable method to obtain Sr-BCP scaffolds. Thus, this approach could be explored with other CaP scaffolds aiming to optimize their performance and the addition of alternative therapeutic ions.

Effect of Thermomechanical Processing Induced Retained Strain on In Vitro, In Vivo Biodegradation Response and Cytocompatibility of Mg Alloy

The implications of retained strain on in vitro and in vivo degradation behavior as well as cytocompatibility of the Mg-4Zn-0.5Ca-0.8Mn alloy is comprehensively studied. The retained strain is induced in homogenized specimens by hard-plate hot forging (HPHF) at a temperature (523 K) lower than the recrystallization temperature of the alloy. The retained strain generated during deformation process deteriorated the corrosion response of the deformed alloy as compared to its homogenized counterpart. The strained area of deformed specimen with high dislocation density promoted defect generation (oxygen vacancies) in the film and facilitated preferential migration of ions, consequently leading to formation of a nonuniform product film with low protectiveness. In addition to strain magnitude, the distribution of retained strain also influenced the product film properties in the deformed specimens. An even distribution of retained strain improved the uniformity of the product film to certain extent by providing greater film coverage, resulting in higher film resistance. After 24 h of immersion, the protectiveness of the film was further improved in this specimen due to annihilation of defects through homogeneous ionic migration, which led to the development of a uniform and stable film that restricted further ionic diffusion. The dissolution of Zn(OH)2 into Zn2+ ions was promoted at lower pH, resulting in enhanced antimicrobial activity in the specimen with the lowest degradation. Besides, the specimen with stable product film not only minimized the rate of further degradation but also served as an interface for new bone growth, as evident from in vivo studies.

Biocompatibility and pro-mineralization effects of premixed calcium silicate-based materials on human dental pulp stem cells: An in vitro and in vivo study

Premixed calcium silicate-based materials have recently been developed and are recommended for a wide range of endodontic procedures, including vital pulp therapy. This study investigated the in vitro biocompatibility and pro-mineralization effect and in vivo reparative dentin formation of EndoSequence Root Repair Material, EndoSequence BCRRM, Bio-C Repair, and Well-pulp PT. Both fresh and set extracts had no detrimental effect on the growth of human dental pulp stem cells. The fresh extracts had a higher calcium concentration than the set extracts and induced considerably greater mineralized nodule formation. EndoSequence Root Repair Material had the longest setting time, whereas Bio-C Repair had the shortest. When these materials were applied to exposed rat molar pulps, mineralized tissue deposition was found at the exposure sites after 2 weeks. These results indicate that the premixed calcium silicate-based materials tested could have positive benefits for direct pulp capping procedures.

Modulation of osteoblastogenesis by NRF2: NRF2 activation suppresses osteogenic differentiation and enhances mineralization in human bone marrow-derived mesenchymal stromal cells

Mesenchymal stromal stem cells (MSCs) or skeletal stem cells (SSCs) play a major role in tissue repair due to their robust ability to differentiate into osteoblasts, chondrocytes, and adipocytes. Complex cell signaling cascades tightly regulate this differentiation. In osteogenic differentiation, Runt-related transcription factor 2 (RUNX2) and ALP activity are essential. Furthermore, during the latter stages of osteogenic differentiation, mineral formation mediated by the osteoblast occurs with the secretion of a collagenous extracellular matrix and calcium deposition. Activation of nuclear factor erythroid 2-related factor 2 (NRF2), an important transcription factor against oxidative stress, inhibits osteogenic differentiation and mineralization via modulation of RUNX2 function; however, the exact role of NRF2 in osteoblastogenesis remains unclear. Here, we demonstrate that NRF2 activation in human bone marrow-derived stromal cells (HBMSCs) suppressed osteogenic differentiation. NRF2 activation increased the expression of STRO-1 and KITLG (stem cell markers), indicating NRF2 protects HBMSCs stemness against osteogenic differentiation. In contrast, NRF2 activation enhanced mineralization, which is typically linked to osteogenic differentiation. We determined that these divergent results were due in part to the modulation of cellular calcium flux genes by NRF2 activation. The current findings demonstrate a dual role for NRF2 as a HBMSC maintenance factor as well as a central factor in mineralization, with implications therein for elucidation of bone formation and cellular Ca2+ kinetics, dystrophic calcification and, potentially, application in the modulation of bone formation.

Fluorophore Label-Free Light-up Near Infrared Deoxyribonucleic Acid Nanosensor for Monitoring Extracellular Potassium Levels

Fluorescent DNA nanosensors have been widely used due to their unique advantages, among which the near-infrared (NIR) imaging mode can provide deeper penetration depth and lower biological background for the nanosensors. However, efficient NIR quenchers require ingenious design, complex synthesis, and modification, which severely limit the development of NIR DNA nanosensors. Label-free strategies based on G-quadruplex (G4) and NIR G4 dyes were first introduced into in situ extracellular imaging, and a novel NIR sensing strategy for the specific detection of extracellular targets is proposed. The strategy avoids complex synthesis and site-specific modification by controlling the change of the NIR signal through the formation of a G4 nanostructure. A light-up NIR DNA nanosensor based on potassium ion (K+)-sensitive G4 chain PS2.M was constructed to verify the strategy. PS2.M forms a stable G4 nanostructure in the presence of K+ and activates the NIR G4 dye CSTS, thus outputting NIR signals. The nanosensor can rapidly respond to K+ with a linear range of 5-50 mM and has good resistance to interference. The nanosensor with cholesterol can provide feedback on the changes in extracellular K+ concentration in many kinds of cells, serving as a potential tool for the study of diseases such as epilepsy and cancer, as well as the development of related drugs. The strategy can be potentially applied to the NIR detection of a variety of extracellular targets with the help of functional DNAs such as aptamer and DNAzyme.

The Effect of Mixed Polymethylmethacrylate and Hydroxyapatite on Viability of Stem Cell from Human Exfoliated Deciduous Teeth and Osteoblast

OBJECTIVES

 Stem cell from human exfoliated deciduous teeth (SHED) has great potential for bone tissue engineering and cell therapy for regenerative medicine. It has been combined with biomaterials such as mixed of polymethylmethacrylate (PMMA) and hydroxyapatite (HA) as candidates for synthetic bone graft biomaterial. The aim of this study was to analyze the toxicity test of mixed PMMA-HA scaffold seeded with SHED and osteoblast in vitro.

MATERIALS AND METHODS

 SHED was isolated from the pulp of noncarious deciduous teeth and osteoblast cells were cultured, and exposed to PMMA-HA scaffolds with three concentration groups: 20/80, 30/70, and 40/60 for 24 hours. Cytotoxicity test was performed by MTT assay to cell viability.

STATISTICAL ANALYSIS

 Data were analyzed using IBM SPSS Statistics 25, one-way analysis of variance followed by least significant difference test, considering the level of significance p-value less than 0.05 RESULTS:  The percentage of SHED's viability was best in the PMMA-HA group with concentrations of 20/80, followed by 30/70, and 40/60 with 87.03, 75.33, and 65.79%, respectively. The percentage of osteoblast cell's viability was best in the PMMA-HA group with concentrations of 20/80, followed by 30/70, and 40/60 with 123.6, 108.36, and 93.48%, respectively.

CONCLUSIONS

 Mixed PMMA-HA was not toxic for the SHED and osteoblast. This characteristic is the initial requirement to be proposed as an alternative material for healing alveolar bone defects. In vivo animal research is mandatory to confirm the use of PMMA-HA on the alveolar defect model.

The effect of Si species released from bioactive glasses on cell behaviour: A quantitative review

Despite over 50 years of silicate bioactive glass (SBG) research, commercial success, and 6000+ published articles, there remains a lack of understanding of how soluble silicate (Si) species released from SBGs influences cellular responses. Using a systematic approach, this article quantitatively compares the in vitro responses of cells to SBG dissolution products reported in the literature and determines if there is a Si concentration ([Si]) dependent effect on cell behaviour. Cell behavioural responses to SBGs [Si] in dissolution products included metabolic activity (reported in 52 % of articles), cell number (24 %), protein production (22 %), gene expression (22 %) and biomineralization (24 %). There was a difference in the [Si] reported to cause increased (desirable) cellular responses (median = 30.2 ppm) compared to the [Si] reported to cause decreased (undesirable) cellular responses (median = 52.0 ppm) (P ≤ 0.001). The frequency of undesirable outcomes increased with increasing [Si], with ∼3 times more negative outcomes reported above 52 ppm. We also investigated the effect of [Si] on specific cellular outcomes (e.g., metabolic activity, angiogenesis, osteogenesis), if cell type/species influenced these responses and the impact of other ions (Ca, P, Na) within the SBG dissolution media on cell behaviour. This review has, for the first time, quantitatively compared the cellular responses to SBGs from the literature, providing a quantitative overview of SBG in vitro practices and presents evidence of a range of [Si] where desirable cellular responses may be more likely (30-52 ppm). This review also demonstrates the need for greater standardisation of in vitro methodological approaches and recommends some minimum reporting standards. STATEMENT OF SIGNIFICANCE: This systematic review investigates the relationship between the concentration of Si released from Si-bioactive glasses (SBG) and in vitro cellular responses. Si releasing materials continue to be of considerable scientific, commercial, and medical interest (with 1500+ articles published in the last 3 years) but there is considerable variation in the reported biologically effective Si concentrations and on the importance of Si on cell behaviour. Despite the variation in methodological approaches, this article demonstrated statistical commonalities in the Si concentrations that cause desirable and undesirable cellular behaviours, suggesting a window where positive cellular outcomes are more likely. This review also provides a quantitative analysis of in vitro practices within the bioactive glass field and highlights the need for greater standardisation.

Is it possible to 3D bioprint load-bearing bone implants? A critical review

Rehabilitative capabilities of any tissue engineered scaffold rely primarily on the triad of (i) biomechanical properties such as mechanical properties and architecture, (ii) chemical behavior such as regulation of cytokine expression, and (iii) cellular response modulation (including their recruitment and differentiation). The closer the implant can mimic the native tissue, the better it can rehabilitate the damage therein. Among the available fabrication techniques, only 3D bioprinting (3DBP) can satisfactorily replicate the inherent heterogeneity of the host tissue. However, 3DBP scaffolds typically suffer from poor mechanical properties, thereby, driving the increased research interest in development of load-bearing 3DBP orthopedic scaffolds in recent years. Typically, these scaffolds involve multi-material 3D printing, comprising of at-least one bioink and a load-bearing ink; such that mechanical and biological requirements of the biomaterials are decoupled. Ensuring high cellular survivability and good mechanical properties are of key concerns in all these studies. 3DBP of such scaffolds is in early developmental stages, and research data from only a handful of preliminary animal studies are available, owing to limitations in print-capabilities and restrictive materials library. This article presents a topically focused review of the state-of-the-art, while highlighting aspects like available 3DBP techniques; biomaterials' printability; mechanical and degradation behavior; and their overall bone-tissue rehabilitative efficacy. This collection amalgamates and critically analyses the research aimed at 3DBP of load-bearing scaffolds for fulfilling demands of personalized-medicine. We highlight the recent-advances in 3DBP techniques employing thermoplastics and phosphate-cements for load-bearing applications. Finally, we provide an outlook for possible future perspectives of 3DBP for load-bearing orthopedic applications. Overall, the article creates ample foundation for future research, as it gathers the latest and ongoing research that scientists could utilize.

Assembling the Puzzle Pieces. Insights for in Vitro Bone Remodeling

As a highly dynamic organ, bone changes during throughout a person's life. This process is referred to as 'bone remodeling' and it involves two stages - a well-balanced osteoclastic bone resorption and an osteoblastic bone formation. Under normal physiological conditions bone remodeling is highly regulated that ensures tight coupling between bone formation and resorption, and its disruption results in a bone metabolic disorder, most commonly osteoporosis. Though osteoporosis is one of the most prevalent skeletal ailments that affect women and men aged over 40 of all races and ethnicities, currently there are few, if any safe and effective therapeutic interventions available. Developing state-of-the-art cellular systems for bone remodeling and osteoporosis can provide important insights into the cellular and molecular mechanisms involved in skeletal homeostasis and advise better therapies for patients. This review describes osteoblastogenesis and osteoclastogenesis as two vital processes for producing mature, active bone cells in the context of interactions between cells and the bone matrix. In addition, it considers current approaches in bone tissue engineering, pointing out cell sources, core factors and matrices used in scientific practice for modeling bone diseases and testing drugs. Finally, it focuses on the challenges that bone regenerative medicine is currently facing.

Progress and emerging techniques for biomaterial-based derivation of mesenchymal stem cells (MSCs) from pluripotent stem cells (PSCs)

The use of mesenchymal stem cells (MSCs) for clinical purposes has skyrocketed in the past decade. Their multilineage differentiation potentials and immunomodulatory properties have facilitated the discovery of therapies for various illnesses. MSCs can be isolated from infant and adult tissue sources, which means they are easily available. However, this raises concerns because of the heterogeneity among the various MSC sources, which limits their effective use. Variabilities arise from donor- and tissue-specific differences, such as age, sex, and tissue source. Moreover, adult-sourced MSCs have limited proliferation potentials, which hinders their long-term therapeutic efficacy. These limitations of adult MSCs have prompted researchers to develop a new method for generating MSCs. Pluripotent stem cells (PSCs), such as embryonic stem cells and induced PSCs (iPSCs), can differentiate into various types of cells. Herein, a thorough review of the characteristics, functions, and clinical importance of MSCs is presented. The existing sources of MSCs, including adult- and infant-based sources, are compared. The most recent techniques for deriving MSCs from iPSCs, with a focus on biomaterial-assisted methods in both two- and three-dimensional culture systems, are listed and elaborated. Finally, several opportunities to develop improved methods for efficiently producing MSCs with the aim of advancing their various clinical applications are described.

A 3D biomimetic optoelectronic scaffold repairs cranial defects

Bone fractures and defects pose serious health-related issues on patients. For clinical therapeutics, synthetic scaffolds have been actively explored to promote critical-sized bone regeneration, and electrical stimulations are recognized as an effective auxiliary to facilitate the process. Here, we develop a three-dimensional (3D) biomimetic scaffold integrated with thin-film silicon (Si)-based microstructures. This Si-based hybrid scaffold not only provides a 3D hierarchical structure for guiding cell growth but also regulates cell behaviors via photo-induced electrical signals. Remotely controlled by infrared illumination, these Si structures electrically modulate membrane potentials and intracellular calcium dynamics of stem cells and potentiate cell proliferation and differentiation. In a rodent model, the Si-integrated scaffold demonstrates improved osteogenesis under optical stimulations. Such a wirelessly powered optoelectronic scaffold eliminates tethered electrical implants and fully degrades in a biological environment. The Si-based 3D scaffold combines topographical and optoelectronic stimuli for effective biological modulations, offering broad potential for biomedicine.

Microfluidic 3D Platform to Evaluate Endothelial Progenitor Cell Recruitment by Bioactive Materials

Most of the conventional in vitro models to test biomaterial-driven vascularization are too simplistic to recapitulate the complex interactions taking place in the actual cell microenvironment, which results in a poor prediction of the in vivo performance of the material. However, during the last decade, cell culture models based on microfluidic technology have allowed attaining unprecedented levels of tissue biomimicry. In this work, we propose a microfluidic-based 3D model to evaluate the effect of bioactive biomaterials capable of releasing signalling cues (such as ions or proteins) in the recruitment of endogenous endothelial progenitor cells, a key step in the vascularization process. The usability of the platform is demonstrated using experimentally-validated finite element models and migration and proliferation studies with rat endothelial progenitor cells (rEPCs) and bone marrow-derived rat mesenchymal stromal cells (BM-rMSCs). As a proof of concept of biomaterial evaluation, the response of rEPCs to an electrospun composite made of polylactic acid with calcium phosphates nanoparticles (PLA+CaP) was compared in a co-culture microenvironment with BM-rMSC to a regular PLA control. Our results show a significantly higher rEPCs migration and the upregulation of several pro-inflammatory and proangiogenic proteins in the case of the PLA+CaP. The effects of osteopontin (OPN) on the rEPCs migratory response were also studied using this platform, suggesting its important role in mediating their recruitment to a calcium-rich microenvironment. This new tool could be applied to screen the capacity of a variety of bioactive scaffolds to induce vascularization and accelerate the preclinical testing of biomaterials. STATEMENT OF SIGNIFICANCE: : For many years researchers have used neovascularization models to evaluate bioactive biomaterials both in vitro, with low predictive results due to their poor biomimicry and minimal control over cell cues such as spatiotemporal biomolecule signaling, and in vivo models, presenting drawbacks such as being highly costly, time-consuming, poor human extrapolation, and ethically controversial. We describe a compact microphysiological platform designed for the evaluation of proangiogenesis in biomaterials through the quantification of the level of sprouting in a mimicked endothelium able to react to gradients of biomaterial-released signals in a fibrin-based extracellular matrix. This model is a useful tool to perform preclinical trustworthy studies in tissue regeneration and to better understand the different elements involved in the complex process of vascularization.

Comparison of periodontal wound healing/regeneration by recombinant human fibroblast growth factor-2 combined with β-tricalcium phosphate, carbonate apatite, or deproteinized bovine bone mineral in a canine one-wall intra-bony defect model

AIM

To evaluate periodontal wound healing/regeneration of one-wall intra-bony defects treated with recombinant human fibroblast growth factor-2 (rhFGF-2) and beta-tricalcium phosphate (β-TCP), carbonate apatite (CO₃ Ap), or deproteinized bovine bone mineral (DBBM) in dogs.

MATERIALS AND METHODS

The stability of rhFGF-2 adsorbed onto the bone substitutes was evaluated by Enzyme-Linked Immunosorbent Assay (ELISA). One-wall intra-bony defects (5 × 5 × 5 mm) created in five adult male beagle dogs were treated with rhFGF-2 alone (rhFGF-2), rhFGF-2 with β-TCP (rhFGF-2/β-TCP), rhFGF-2 with CO₃ Ap (rhFGF-2/CO₃ Ap), or rhFGF-2 with DBBM (rhFGF-2/DBBM). Histological outcomes (e.g., linear length of new cementum adjacent to the newly formed bone with inserting collagen fibres [NA] as the primary outcome) were evaluated at 10 weeks post surgery.

RESULTS

Significantly higher amount of rhFGF-2 was adsorbed onto CO₃ Ap compared with β-TCP. Among the treatment groups, the rhFGF-2/DBBM group showed the highest amount of periodontal tissue regeneration. The rhFGF-2/DBBM group showed significantly greater formation of NA (3.22 ± 0.40 mm) compared with rhFGF-2 (1.17 ± 1.00 mm, p < .01) group. Additionally, new bone area in the rhFGF-2/DBBM group (9.78 ± 2.30 mm² ) was significantly higher than that in the rhFGF-2 (5.08 ± 1.26 mm² , p < .01), rhFGF-2/β-TCP (5.91 ± 1.27 mm² , p < .05), and rhFGF-2/CO₃ Ap (6.51 ± 1.49 mm² , p < .05) groups. Slight ankylosis was found in the rhFGF-2/β-TCP (1/9 sites), rhFGF-2/CO₃ Ap (3/10 sites), and rhFGF-2/DBBM (1/9 sites) groups.

CONCLUSIONS

Within their limitations, the present data indicate that DBBM seems to be a suitable carrier for rhFGF-2 and that rhFGF-2/DBBM treatment promotes favourable periodontal regeneration compared with rhFGF-2, rhFGF-2/β-TCP, and rhFGF-2/CO₃ Ap treatments in one-wall intra-bony defects.

Characterization of Dental Pulp Stem Cells Response to Bone Substitutes Biomaterials in Dentistry

Bone substitute biomaterials (BSBs) represent a promising alternative to bone autografts, due to their biocompatibility, osteoconduction, slow resorption rates, and the ability to define and maintain volume for bone gain in dentistry. Many biomaterials are tailored to provide structural and biological support for bone regeneration, and allow the migration of bone-forming cells into the bone defect. Neural crest-derived stem cells isolated from human dental pulp (hDPSCs) represent a suitable stem cell source to study the biological effects of BSBs on osteoprogenitor cells involved in the physiological bone regenerative processes. This study aimed to evaluate how three different BSBs affect the stem cell properties, osteogenic differentiation, and inflammatory properties of hDPSCs. Our data highlight that BSBs do not alter cell proliferation and stemness markers expression, nor induce any inflammatory responses. Bone metabolism data show that hDPSCs exposed to the three BSBs distinctively secrete the factors supporting osteoblast activity and osteoclast activity. Our data indicate that (i) hDPSCs are a suitable stem cell source to study the effects of BSBs, and that (ii) the formulation of BSBs may condition the biological properties of stem cells, suggesting their versatile suitability to different dentistry applications.

Activation and Migration of Human Skeletal Muscle Stem Cells In Vitro Differently Rely on Calcium Signals

Muscle regeneration is essential for proper muscle homeostasis and relies primarily on muscle stem cells (MuSC). MuSC are maintained quiescent in their niche and can be activated following muscle injury. Using an in vitro model of primary human quiescent MuSC (called reserve cells, RC), we analyzed their Ca²⁺ response following their activation by fetal calf serum and assessed the role of Ca²⁺ in the processes of RC activation and migration. The results showed that RC displayed a high response heterogeneity in a cell-dependent manner following serum stimulation. Most of these responses relied on inositol 1,4,5-trisphosphate (IP₃)-dependent Ca²⁺ release associated with Ca²⁺ influx, partly due to store-operated calcium entry. Our study further found that blocking the IP₃ production, Ca²⁺ influx, or both did not prevent the activation of RC. Intra- or extracellular Ca²⁺ chelation did not impede RC activation. However, their migration potential depended on Ca²⁺ responses displayed upon stimulation, and Ca²⁺ blockers inhibited their movement. We conclude that the two major steps of muscle regeneration, namely the activation and migration of MuSC, differently rely on Ca²⁺ signals.

Ferutinin induces osteoblast differentiation of DPSCs via induction of KLF2 and autophagy/mitophagy

Osteoblast differentiation is critically reduced in various bone-related pathogenesis, including arthritis and osteoporosis. For future development of effective regenerative therapeutics, herein, we reveal the involved molecular mechanisms of a phytoestrogen, ferutinin-induced initiation of osteoblast differentiation from dental pulp-derived stem cell (DPSC). We demonstrate the significantly increased expression level of a transcription factor, Kruppel-like factor 2 (KLF2) along with autophagy-related molecules in DPSCs after induction with ferutinin. The loss-of-function and the gain-of-function approaches of KLF2 confirmed that the ferutinin-induced KLF2 modulated autophagic and OB differentiation-related molecules. Further, knockdown of the autophagic molecule (ATG7 or BECN1) from DPSC resulted not only in a decreased level of KLF2 but also in the reduced levels of OB differentiation-related molecules. Moreover, mitochondrial membrane potential-related molecules were increased and induction of mitophagy was observed in DPSCs after the addition of ferutinin. The reduction of mitochondrial as well as total ROS generations; and induction of intracellular Ca²⁺ production were also observed in ferutinin-treated DPSCs. To test the mitochondrial respiration in DPSCs, we found that the cells treated with ferutinin showed a reduced extracellular acidification rate (ECAR) than that of their vehicle-treated counterparts. Furthermore, mechanistically, chromatin immunoprecipitation (ChIP) analysis revealed that the addition of ferutinin in DPSCs not only induced the level of KLF2, but also induced the transcriptionally active epigenetic marks (H3K27Ac and H3K4me3) on the promoter region of the autophagic molecule ATG7. These results provide strong evidence that ferutinin stimulates OB differentiation via induction of KLF2-mediated autophagy/mitophagy.

Calcium released by osteoclastic resorption stimulates autocrine/paracrine activities in local osteogenic cells to promote coupled bone formation

A major cause of osteoporosis is impaired coupled bone formation. Mechanistically, both osteoclast-derived and bone-derived growth factors have been previously implicated. We hypothesize that the release of bone calcium during osteoclastic bone resorption is essential for coupled bone formation. Osteoclastic resorption increases interstitial fluid calcium locally from the normal 1.8 mM up to 5 mM. MC3T3-E1 osteoprogenitors, cultured in a 3.6 mM calcium medium, demonstrated that calcium signaling stimulated osteogenic cell proliferation, differentiation, and migration. Calcium channel knockdown studies implicated calcium channels, Cav1.2, store-operated calcium entry (SOCE), and calcium-sensing receptor (CaSR) in regulating bone cell anabolic activities. MC3T3-E1 cultured in a 3.6 mM calcium medium expressed increased gene expression of Wnt signaling and growth factors platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and bone morphogenic protein-2 (BMP 2). Our coupling model of bone formation, the Receptor activator of nuclear factor-kappa-Β ligand (RANKL) treated mouse calvaria, confirmed the role of calcium signaling in coupled bone formation by exhibiting increased gene expression for osterix and osteocalcin. Critically, dual immunocytochemistry showed that RANKL treatment increased osterix positive cells and increased fluorescence intensity of Cav1.2 and CaSR protein expression per osterix positive cell. The data established that calcium released by osteoclasts contributed to the regulation of coupled bone formation. CRISPR/Cas-9 knockout of Cav1.2 in osteoprogenitors cultured in basal calcium medium caused a >80% decrease in the expression of downstream osteogenic genes, emphasizing the large magnitude of the effect of calcium signaling. Thus, calcium signaling is a major regulator of coupled bone formation.

Hybridizing gellan/alginate and thixotropic magnesium phosphate-based hydrogel scaffolds for enhanced osteochondral repair

Osteochondral defects include the damage of cartilage and subchondral bone, which are still clinical challenges. The general replacements are difficult to simultaneously repair cartilage and subchondral bone due to their various requirements. Moreover, appropriate printable bioactive materials were needed for 3D bioprinting personalized scaffolds for osteochondral repairing. Herein, the novel hydrogel was developed by hybridizing the alginate sodium (SA) and gellan gum (GG) with the inorganic thixotropic magnesium phosphate-based gel (TMP-BG) in the pre-crosslinking of Mg²⁺ to enhance osteochondral repairing. SA-GG/TMP-BG hybrid hydrogels possessed controllable rheological, injectable, mechanical properties and porosities by tuning their ratio. The shear-thinning of SA-GG/TMP-BG was responsible for its excellent injectability. SA-GG/TMP-BG hybrid hydrogels displayed good cell compatibility, on which MG-63 and BMSCs cells attached and spread well with the high proliferation and up-regulated osteogenic genes. In addition, the inorganic TMP-BG gel hybridized with SA-GG hydrogel released Mg²⁺ was conducive to recruiting BMSCs and promoting the osteogenic and chondrogenic differentiation of BMSCs. Histological results confirmed that SA-GG/TMP6040 significantly promoted the osteogenesis of subchondral bone and then further facilitated the cartilage repairing after being implanted in osteochondral defects of rabbits for 6 and 12 weeks.

Our finding revealed that the inorganic TMP-BG endowed the excellent osteogenic activity of the hybrid hydrogels, which played a key role in successful osteochondral repairing. The newly SA-GG/TMP-BG hybrid hydrogels appeared to be promising materials for osteochondral repairing and the further 3D bioprinting.

Biomimetic biphasic curdlan-based scaffold for osteochondral tissue engineering applications - Characterization and preliminary evaluation of mesenchymal stem cell response in vitro

Osteochondral defects remain a huge problem in medicine today. Biomimetic bi- or multi-phasic scaffolds constitute a very promising alternative to osteochondral autografts and allografts. In this study, a new curdlan-based scaffold was designed for osteochondral tissue engineering applications. To achieve biomimetic properties, it was enriched with a protein component - whey protein isolate as well as a ceramic ingredient - hydroxyapatite granules. The scaffold was fabricated via a simple and cost-efficient method, which represents a significant advantage. Importantly, this technique allowed generation of a scaffold with two distinct, but integrated phases. Scanning electron microcopy and optical profilometry observations demonstrated that phases of biomaterial possessed different structural properties. The top layer of the biomaterial (mimicking the cartilage) was smoother than the bottom one (mimicking the subchondral bone), which is beneficial from a biological point of view because unlike bone, cartilage is a smooth tissue. Moreover, mechanical testing showed that the top layer of the biomaterial had mechanical properties close to those of natural cartilage. Although the mechanical properties of the bottom layer of scaffold were lower than those of the subchondral bone, it was still higher than in many analogous systems. Most importantly, cell culture experiments indicated that the biomaterial possessed high cytocompatibility towards adipose tissue-derived mesenchymal stem cells and bone marrow-derived mesenchymal stem cells in vitro. Both phases of the scaffold enhanced cell adhesion, proliferation, and chondrogenic differentiation of stem cells (revealing its chondroinductive properties in vitro) as well as osteogenic differentiation of these cells (revealing its osteoinductive properties in vitro). Given all features of the novel curdlan-based scaffold, it is worth noting that it may be considered as promising candidate for osteochondral tissue engineering applications.

Remodeling Effects of the Combination of GGT Scaffolds, Percutaneous Electrical Stimulation, and Acupuncture on Large Bone Defects in Rats

The regeneration defect of bone is a long-term physiological process after bone injuries. To accelerate the bone remodeling process, the combination of chemical and physical stimulations provides an efficient strategy to allow maturation and to functionalize osteoclasts and osteoblasts. This study aims to investigate the dual effects of a tricalcium phosphate (TCP)-based gelatin scaffold (GGT) in combination with electroacupuncture stimulation on the activation of osteoclasts and osteoblasts, as well as new bone regrowth in vitro and in vivo. We demonstrated that electrical stimulation changes the pH of a culture medium and activates osteoblasts and osteoclasts in an in vitro co-culture system. Furthermore, we showed that electroacupuncture stimulation can enhance osteogenesis and new bone regrowth in vivo and can upregulate the mechanism among parathyroid hormone intact (PTH-i), calcium, osteoclasts, and osteoblasts in the bone-defected rats. Those results showed the potential interest to combine the electroacupuncture technique with GGT scaffolds to improve bone remodeling after injury.

Chemical Compounds Released from Specific Osteoinductive Bioactive Materials Stimulate Human Bone Marrow Mesenchymal Stem Cell Migration

In this work, a poly(L-lactide-co-glycolide) (PLGA)-based composite was enriched with one of the following sol-gel bioactive glasses (SBG) at 50 wt.%: A1—40 mol% SiO2, 60 mol% CaO, CaO/SiO2 ratio of 1.50; S1—80 mol% SiO2, 20 mol% CaO, CaO/SiO2 ratio of 0.25; A2—40 mol% SiO2, 54 mol% CaO, 6 mol% P2O5, CaO/SiO2 ratio of 1.35; S2—80 mol% SiO2,16 mol% CaO, 4 mol% P2O5, CaO/SiO2 ratio of 0.20. The composites and PLGA control sheets were then soaked for 24 h in culture media, and the obtained condition media (CM) were used to treat human bone marrow stromal cells (hBMSCs) for 72 h. All CMs from the composites increased ERK 1/2 activity vs. the control PLGA CM. However, expressions of cell migration-related c-Fos, osteopontin, matrix metalloproteinase-2, C-X-C chemokine receptor type 4, vascular endothelial growth factor, and bone morphogenetic protein 2 were significantly increased only in cells treated with the CM from the A1/PLGA composite. This CM also significantly increased the rate of human BMSC migration but did not affect cell metabolic activity. These results indicate important biological markers that are upregulated by products released from the bioactive composites of a specific chemical composition, which may eventually prompt osteoprogenitor cells to colonize the bioactive material and accelerate the process of tissue regeneration.

Influence of Biomimetically Mineralized Collagen Scaffolds on Bone Cell Proliferation and Immune Activation

Collagen, as the main component of connective tissue, is frequently used in various tissue engineering applications. In this study, porous sponge-like collagen scaffolds were prepared by freeze-drying and were then mineralized in a simulated body fluid. The mechanical stability was similar in both types of scaffolds, but the mineralized scaffolds (MCS) contained significantly more calcium, magnesium and phosphorus than the unmineralized scaffolds (UCS). Although the MCS contained a lower percentage (~32.5%) of pores suitable for cell ingrowth (113–357 μm in diameter) than the UCS (~70%), the number of human-osteoblast-like MG-63 cells on days 1, 3 and 7 after seeding was higher on MCS than on UCS, and the cells penetrated deeper into the MCS. The cell growth in extracts prepared by eluting the scaffolds for 7 days in a cell culture medium was also markedly higher in the MCS extracts, as indicated by real-time monitoring in the sensory xCELLigence system for 7 days. From this point of view, MCS are more promising for bone tissue engineering than UCS. However, MCS evoked a more pronounced inflammatory response than UCS, as indicated by the production of tumor necrosis factor-alpha (TNF-α) in macrophage-like RAW 264.7 cells in cultures on these scaffolds.

Peptide Amphiphile Hydrogels Based on Homoternary Cucurbit[8]uril Host-Guest Complexes

Supramolecular hydrogels based on peptide amphiphiles (PAs) are promising materials for tissue engineering and model extracellular matrixes for biological studies. While PA hydrogels are conventionally formed via electrostatic screening, new hydrogelation mechanisms might help to improve the design and functionality of these materials. Here, we present a host-guest-mediated PA hydrogelation method that relies on the formation of a host-guest homoternary complex with cucurbit[8]uril (CB[8]) and aromatic amino-acid-bearing PA nanofibers. As a result of the host-guest cross-linking between PA nanofibers, hierarchical morphologies and increased stiffness were found when host-guest-mediated PA hydrogels were compared to their ion-based equivalents. Additionally, both families of hydrogels exhibited similar biocompatibilities. These results demonstrate that CB[8]-mediated hydrogelation can be used as an alternative cross-linking method to upgrade the design of PA materials and extend their biomedical applications.

Electromagnetic field exposure as a plausible approach to enhance the proliferation and differentiation of mesenchymal stem cells in clinically relevant scenarios

Mesenchymal stem/stromal cell (MSC)‍-based therapy has been regarded as one of the most revolutionary breakthroughs in the history of modern medicine owing to its myriad of immunoregulatory and regenerative properties. With the rapid progress in the fields of osteo- and musculoskeletal therapies, the demand for MSC-based treatment modalities is becoming increasingly prominent. In this endeavor, researchers around the world have devised new and innovative techniques to support the proliferation of MSCs while minimizing the loss of hallmark features of stem cells. One such example is electromagnetic field (EMF) exposure, which is an alternative approach with promising potential. In this review, we present a critical discourse on the efficiency, practicability, and limitations of some of the relevant methods, with insurmountable evidence backing the implementation of EMF as a feasible strategy for the clinically relevant expansion of MSCs.

CaCO3-based carriers with prolonged release property for antifungal drug delivery to hair follicles

Superficial fungal infections are of serious concern worldwide due to their morbidity and increasing distribution across the globe in this era of growing antimicrobial resistance. Delivery of antifungals to target...

Bioactive fluorescent hybrid microparticles as a stand-alone osteogenic differentiation inducer

Osteogenic differentiation of stem cells is one of the essential steps in bone regeneration. While supplementing exogenous factors using differentiation media is the established method to differentiate stem cells into osteoblasts on biomaterials, designing biomaterials that can act as a stand-alone differentiation inducer and promote bone regeneration is preferred for clinical translation. In this work, we report dexamethasone-loaded organic-inorganic hybrid microparticles synthesized from an intrinsically fluorescent poly (ester amide) and tertiary bioactive glass (PEA-BG) as a stand-alone osteogenic differentiation inducer. The mechanical properties data indicated that the compressive modulus of fluorescent hybrid microparticles could be modulated by its composition. The hybrid fluorescent microparticles supported the adhesion and proliferation of 10T1/2 ​cells in culture for up to seven days. Both pristine and dexamethasone-loaded PEA-BG microparticles were able to induce osteogenic differentiation of 10T1/2 ​cells in the absence of any media supplement, to a level even higher than standard osteogenic media, as evidenced by the expression of osteogenic markers on gene and protein levels and matrix mineralization. Taken together, the fluorescent PEA-BG hybrid microparticles have the potential to be used as a stand-alone biomaterial for osteogenic differentiation and bone regeneration.

Osteopontin, a bridge links osteoarthritis and osteoporosis

Osteoarthritis (OA) is the most prevalent joint disease characterized by degradation of articular cartilage, inflammation, and changes in periarticular and subchondral bone of joints. Osteoporosis (OP) is another systemic skeletal disease characterized by low bone mass and bone mineral density (BMD) accompanied by microarchitectural deterioration in bone tissue and increased bone fragility and fracture risk. Both OA and OP are mainly affected on the elderly people. Recent studies have shown that osteopontin (OPN) plays a vital role in bone metabolism and homeostasis. OPN involves these biological activities through participating in the proliferation, migration, differentiation, and adhesion of several bone-related cells, including chondrocytes, synoviocytes, osteoclasts, osteoblasts, and marrow mesenchymal stem cells (MSCs). OPN has been demonstrated to be closely related to the occurrence and development of many bone-related diseases, such as OA and OP. This review summarizes the role of OPN in regulating inflammation activity and bone metabolism in OA and OP. Furthermore, some drugs that targeted OPN to treat OA and OP are also summarized in the review. However, the complex mechanism of OPN in regulating OA and OP is not fully elucidated, which drives us to explore the depth effect of OPN on these two bone diseases.

Steering the multipotent mesenchymal cells towards an anti-inflammatory and osteogenic bias via photobiomodulation therapy: How to kill two birds with one stone

The bone marrow-derived multipotent mesenchymal cells (MSCs) have captured scientific interest due to their multi-purpose features and clinical applications. The operational dimension of MSCs is not limited to the bone marrow reservoir, which exerts bone-building and niche anabolic tasks; they also meet the needs of quenching inflammation and restoring inflamed tissues. Thus, the range of MSC activities extends to conditions such as neurodegenerative diseases, immune disorders and various forms of osteopenia. Steering these cells towards becoming an effective therapeutic tool has become mandatory. Many laboratories have employed distinct strategies to improve the plasticity and secretome of MSCs. We aimed to present how photobiomodulation therapy (PBM-t) can manipulate MSCs to render them an extraordinary anti-inflammatory and osteogenic instrument. Moreover, we discuss the outcomes of different PBM-t protocols on MSCs, concluding with some perplexities and complexities of PBM-t in vivo but encouraging and feasible in vitro solutions.

Periodontal tissue engineering using an apatite/collagen scaffold obtained by a plasma- and precursor-assisted biomimetic process

BACKGROUND AND OBJECTIVES

In the treatment of severe periodontal destruction, there is a strong demand for advanced scaffolds that can regenerate periodontal tissues with adequate quality and quantity. Recently, we developed a plasma- and precursor-assisted biomimetic process by which a porous collagen scaffold (CS) could be coated with low-crystalline apatite. The apatite-coated collagen scaffold (Ap-CS) promotes cellular ingrowth within the scaffold compared to CS in rat subcutaneous tissue. In the present study, the osteogenic activity of Ap-CS was characterized by cell culture and rat skull augmentation tests. In addition, the periodontal tissue reconstruction with Ap-CS in a beagle dog was compared to that with CS.

METHODS

The plasma- and precursor-assisted biomimetic process was applied to CS to obtain Ap-CS with a low-crystalline apatite coating. The effects of apatite coating on the scaffold characteristics (i.e., surface morphology, water absorption, Ca release, protein adsorption, and enzymatic degradation resistance) were assessed. Cyto-compatibility and the osteogenic properties of Ap-CS and CS were assessed in vitro using preosteoblastic MC3T3-E1 cells. In addition, we performed in vivo studies to evaluate bone augmentation and periodontal tissue reconstruction with Ap-CS and CS in a rat skull and canine furcation lesion, respectively.

RESULTS

As previously reported, the plasma- and precursor-assisted biomimetic process generated a low-crystalline apatite layer with a nanoporous structure that uniformly covered the Ap-CS surface. Ap-CS showed significantly higher water absorption, Ca release, lysozyme adsorption, and collagenase resistance than CS. Cell culture experiments revealed that Ap-CS was superior to CS in promoting the osteoblastic differentiation of MC3T3-E1 cells while suppressing their proliferation. Additionally, Ap-CS significantly promoted (compared to CS) the augmentation of the rat skull bone and showed the potential to regenerate alveolar bone in a dog furcation defect.

CONCLUSION

Ap-CS fabricated by the plasma- and precursor-assisted biomimetic process provided superior promotion of osteogenic differentiation and bone neoformation compared to CS.

Clinically relevant preservation conditions for mesenchymal stem/stromal cells derived from perinatal and adult tissue sources

The interplay between mesenchymal stem/stromal cells (MSCs) and preservation conditions is critical to maintain the viability and functionality of these cells before administration. We observed that Ringer lactate (RL) maintained high viability of bone marrow–derived MSCs for up to 72 h at room temperature (18°C–22°C), whereas adipose‐derived and umbilical cord‐derived MSCs showed the highest viability for 72 h at a cold temperature (4°C–8°C). These cells maintained their adherence ability with an improved recovery rate and metabolic profiles (glycolysis and mitochondrial respiration) similar to those of freshly harvested cells. Growth factor and cytokine analyses revealed that the preserved cells released substantial amounts of leukaemia inhibitory factors (LIFs), hepatocyte growth factor (HGF) and vascular endothelial growth factor‐A (VEGF‐A), as well as multiple cytokines (eg IL‐4, IL‐6, IL‐8, MPC‐1 and TNF‐α). Our data provide the simplest clinically relevant preservation conditions that maintain the viability, stemness and functionality of MSCs from perinatal and adult tissue sources.

Assessment of novel surgical procedures using decellularised muscle and bioactive ceramic: a histological analysis

Tissue regeneration and neovascularisation in cases of major bone loss is a challenge in maxillofacial surgery. The hypothesis of the present study is that the addition of resorbable bioactive ceramic Silica Calcium Phosphate Cement (SCPC) to Declluraized Muscle Scaffold (DSM) can expedite bone formation and maturation. Two surgical defect models were created in 18 nude transgenic mice. Group 1(n = 6), with a 2-mm decortication calvarial defect, was treated with a DSM/SCPC sheet over the corticated bone as an onlay then seeded with human Mesenchymal Stromal Cells hMSC in situ. In Group 2 (n = 6), a critical size (4 mm) calvarial defect was made and grafted with DSM/SCPC/in situ human bone marrow stromal cells (hMSCs). The control groups included Group 3 (n = 3) animals, with a 2-mm decortication defect treated with an onlay DSM sheet, and Group 4 (n = 3) animals, treated with critical size defect grafted with plain DSM. After 8 weeks, bone regeneration in various groups was evaluated using histology, immunohistochemistry and histomorphometry. New bone formation and maturation was superior in groups treated with DSM/SCPC/hMSC. The DMS/SCPC scaffold has the ability to augment and induce bone regeneration and neovascularisation in cases of major bone resorption and critical size defects.

Cytotoxicity and cell response of preosteoblast in calcium sulfate-augmented PMMA bone cement

Poly(methyl methacrylate) (PMMA) has been widely used in orthopedic applications, but bone ingrowth and toxic monomer release are drawback of this material. Particle reinforcement with osteoconductive substitute, such as calcium sulfate (CaSO₄), is one of the solutions used to modify PMMA bone cement. The current study investigated the mechanical, chemical and biological properties of CaSO₄-augmented bone cement. Mechanical strength was measured by a material testing machine. The concentration of methyl methacrylate (MMA) monomer from the various formulations of PMMA mixed with CaSO₄was measured by ultra-performance liquid chromatography (UPLC). CCK-8 assay and ALP assay were performed to evaluate cytotoxicity of released MMA monomer and cell differentiation. The attachment of cells to CaSO₄-augmented bone cement discs was observed by confocal and scanning electron microscopy, and surface topography was also evaluated by atomic force microscopy. The results revealed that increased CaSO₄weight ratios led to compromised mechanical strength and increased MMA monomer release. Cell density and cell differentiation on CaSO₄-augmented bone cement discs were decreased at CaSO₄weight ratios above 10%. In addition, the presence of micropores on the surface and surface roughness were both increased for PMMA composite discs containing higher levels of CaSO₄. These results demonstrated that fewer MC3T3-E1 cells on the surface of CaSO₄-PMMA composites was correlated to increased MMA monomer release, micropore number and surface roughness. In summary, the augmentation of a higher proportion of CaSO₄(>10 wt. %) to PMMA did not promote the biological properties of traditional PMMA bone cement.

Comparison of calcium and hydroxyl ion release ability and in vivo apatite-forming ability of three bioceramic-containing root canal sealers

OBJECTIVE

Bioceramic-containing root canal sealers promote periapical healing via Ca²⁺ and OH^- release and apatite formation on the surface. This study aimed to compare Ca²⁺ and OH^- release and in vivo apatite formation of three bioceramic-containing root canal sealers: EndoSequence BC sealer (Endo-BC), MTA Fillapex (MTA-F), and Nishika Canal Sealer BG (N-BG).

MATERIALS AND METHODS

Polytetrafluoroethylene tubes filled with sealers were immersed in distilled water for 6 and 12 h and for 1, 7, 14, and 28 days to measure Ca²⁺ and OH^- release. Additionally, tubes filled with sealers were implanted in the backs of rats for 28 days, and in vivo apatite formation was analyzed using an electron probe microanalyzer.

RESULTS

Endo-BC released significantly more Ca²⁺ than the other sealers at 6 and 12 h and 1 day. Ca²⁺ release was significantly lower from N-BG than from Endo-BC and MTA-F at 14 and 28 days. OH^- release was significantly higher from Endo-BC than from the other sealers throughout the experiment, except at 1 day. OH^- release was lower from N-BG than from MTA-F at 6 h and 7 days. Only Endo-BC implants exhibited apatite-like calcium-, phosphorus-, oxygen-, and carbon-rich spherulites and apatite layer-like calcium- and phosphorus-rich, but radiopaque element-free, surface regions.

CONCLUSIONS

Ca²⁺ and OH^- release is ranked as follows: Endo-BC > MTA-F > N-BG. Only Endo-BC demonstrated in vivo apatite formation.

CLINICAL RELEVANCE

Endo-BC could promote faster periapical healing than MTA-F and N-BG.

Review on material parameters to enhance bone cell function in vitro and in vivo

Bone plays critical roles in support, protection, movement, and metabolism. Although bone has an innate capacity for regeneration, this capacity is limited, and many bone injuries and diseases require intervention. Biomaterials are a critical component of many treatments to restore bone function and include non-resorbable implants to augment bone and resorbable materials to guide regeneration. Biomaterials can vary considerably in their biocompatibility and bioactivity, which are functions of specific material parameters. The success of biomaterials in bone augmentation and regeneration is based on their effects on the function of bone cells. Such functions include adhesion, migration, inflammation, proliferation, communication, differentiation, resorption, and vascularization. This review will focus on how different material parameters can enhance bone cell function both in vitro and in vivo.

Comparative Evaluation of Two Glass Polyalkenoate Cements: An In Vivo Pilot Study Using a Sheep Model

Poly(methyl methacrylate) (PMMA) is used to manage bone loss in revision total knee arthroplasty (rTKA). However, the application of PMMA has been associated with complications such as volumetric shrinkage, necrosis, wear debris, and loosening. Glass polyalkenoate cements (GPCs) have potential bone cementation applications. Unlike PMMA, GPC does not undergo volumetric shrinkage, adheres chemically to bone, and does not undergo an exothermic setting reaction. In this study, two different compositions of GPCs (GPCA and GPCB), based on the patented glass system SiO₂-CaO-SrO-P₂O₅-Ta₂O₅, were investigated. Working and setting times, pH, ion release, compressive strength, and cytotoxicity of each composition were assessed, and based on the results of these tests, three sets of samples from GPCA were implanted into the distal femur and proximal tibia of three sheep (alongside PMMA as control). Clinical CT scans and micro-CT images obtained at 0, 6, and 12 weeks revealed the varied radiological responses of sheep bone to GPCA. One GPCA sample (implanted in the sheep for 12 weeks) was characterized with no bone resorption. Furthermore, a continuous bone-cement interface was observed in the CT images of this sample. The other implanted GPCA showed a thin radiolucent border at six weeks, indicating some bone resorption occurred. The third sample showed extensive bone resorption at both six and 12 weeks. Possible speculative factors that might be involved in the varied response can be: excessive Zn²⁺ ion release, low pH, mixing variability, and difficulty in inserting the samples into different parts of the sheep bone.

The potential role of mesenchymal stem cells in modulating antiageing process

Ageing and age-related diseases share some basic origin that largely converges on inflammation. Precisely, it boils down to a common pathway characterised by the appearance of a fair amount of proinflammatory cytokines known as inflammageing. Among the proposed treatment for antiageing, MSCs gained attention in recent years. Since mesenchymal stem cells (MSCs) can differentiate itself into a myriad of terminal cells, previously it was believed that these cells migrate to the site of injury and perform their therapeutic effect. However, with the more recent discovery of huge amounts of paracrine factors secreted by MSCs, it is now widely accepted that these cells do not engraft upon transplantation but rather unveil their benefits through excretion of bioactive molecules namely those involved in inflammatory and immunomodulatory activities. Conversely, the true function of these paracrine changes has not been thoroughly investigated all these years. Hence, this review will describe in detail on ways MSCs may capitalize its paracrine properties in modulating antiageing process. Through a comprehensive literature search various elements in the antiageing process, we aim to provide a novel treatment perspective of MSCs in antiageing related clinical conditions.

In vitro biocompatibility and bioactivity of calcium silicate‑based bioceramics in endodontics (Review)

Calcium silicate-based bioceramics have been applied in endodontics as advantageous materials for years. In addition to excellent physical and chemical properties, the biocompatibility and bioactivity of calcium silicate-based bioceramics also serve an important role in endodontics according to previous research reports. Firstly, bioceramics affect cellular behavior of cells such as stem cells, osteoblasts, osteoclasts, fibroblasts and immune cells. On the other hand, cell reaction to bioceramics determines the effect of wound healing and tissue repair following bioceramics implantation. The aim of the present review was to provide an overview of calcium silicate-based bioceramics currently applied in endodontics, including mineral trioxide aggregate, Bioaggregate, Biodentine and iRoot, focusing on their in vitro biocompatibility and bioactivity. Understanding their underlying mechanism may help to ensure these materials are applied appropriately in endodontics.

Human dental pulp stem cell responses to different dental pulp capping materials

Background

Direct pulp capping is a vital pulp therapy for a pin-point dental pulp exposure. Applying a pulp capping material leads to the formation of a dentin bridge and protects pulp vitality. The aim of this study was to compare the effects of four dental materials, DyCal^®, ProRoot^® MTA, Biodentine™, and TheraCal™ LC in vitro.

Methods

Human dental pulp stem cells (hDPs) were isolated and characterized. Extraction medium was prepared from the different pulp capping materials. The hDP cytotoxicity, proliferation, and migration were examined. The odonto/osteogenic differentiation was determined by alkaline phosphatase, Von Kossa, and alizarin red s staining. Osteogenic marker gene expression was evaluated using real-time polymerase chain reaction.

Results

ProRoot^® MTA and Biodentine™ generated less cytotoxicity than DyCal^® and TheraCal™ LC, which were highly toxic. The hDPs proliferated when cultured with the ProRoot^® MTA and Biodentine™ extraction media. The ProRoot^® MTA and Biodentine™ extraction medium induced greater cell attachment and spreading. Moreover, the hDPs cultured in the ProRoot^® MTA or Biodentine™ extraction medium migrated in a similar manner to those in serum-free medium, while a marked reduction in cell migration was observed in the cells cultured in DyCal^® and TheraCal™ LC extraction media. Improved mineralization was detected in hDPs maintained in ProRoot^® MTA or Biodentine™ extraction medium compared with those in serum-free medium.

Conclusion

This study demonstrates the favorable in vitro biocompatibility and bioactive properties of ProRoot^® MTA and Biodentine™ on hDPs, suggesting their superior regenerative potential compared with DyCal^® and TheraCal™.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01544-w.

Calcium channels and their role in regenerative medicine

Stem cells hold indefinite self-renewable capability that can be differentiated into all desired cell types. Based on their plasticity potential, they are divided into totipotent (morula stage cells), pluripotent (embryonic stem cells), multipotent (hematopoietic stem cells, multipotent adult progenitor stem cells, and mesenchymal stem cells [MSCs]), and unipotent (progenitor cells that differentiate into a single lineage) cells. Though bone marrow is the primary source of multipotent stem cells in adults, other tissues such as adipose tissues, placenta, amniotic fluid, umbilical cord blood, periodontal ligament, and dental pulp also harbor stem cells that can be used for regenerative therapy. In addition, induced pluripotent stem cells also exhibit fundamental properties of self-renewal and differentiation into specialized cells, and thus could be another source for regenerative medicine. Several diseases including neurodegenerative diseases, cardiovascular diseases, autoimmune diseases, virus infection (also coronavirus disease 2019) have limited success with conventional medicine, and stem cell transplantation is assumed to be the best therapy to treat these disorders. Importantly, MSCs, are by far the best for regenerative medicine due to their limited immune modulation and adequate tissue repair. Moreover, MSCs have the potential to migrate towards the damaged area, which is regulated by various factors and signaling processes. Recent studies have shown that extracellular calcium (Ca²⁺) promotes the proliferation of MSCs, and thus can assist in transplantation therapy. Ca²⁺ signaling is a highly adaptable intracellular signal that contains several components such as cell-surface receptors, Ca²⁺ channels/pumps/exchangers, Ca²⁺ buffers, and Ca²⁺ sensors, which together are essential for the appropriate functioning of stem cells and thus modulate their proliferative and regenerative capacity, which will be discussed in this review.

New design to remove leukocytes from platelet-rich plasma (PRP) based on cell dimension rather than density

Platelet-rich plasma (PRP) can stimulate the proliferation of stem cells and have a positive effect on tissue repair. Although many commercialized PRP preparation kits are already on the market, first-line clinical workers are still not satisfied with most of the PRP kits. The work of commercial PRP kits is based on the density of blood elements. However, the blood elements are very close in density which makes the separation challenging. Therefore, the mentioned commercialized kits are generally contaminated by leucocytes and erythrocyte. In this study, a home-designed PRP device was developed to use a separation membrane with adequate cut-off pore size of 5 μm, 3 μm and 2 μm for the groups of H5M, H3M, and H2M, respectively, to be placed in the middle of the centrifuge tube. The home-designed H2M showed a very promising results regardless of the final volume (1.82 ± 0.09 ml), platelet yield (8.39 ± 0.44%), Red Blood Cells (0%), White Blood Cells (0%), and Relative Concentration of Platelet Increment value (225.09%). Further, it showed a good result in cell viability and cytotoxicity and confirmed a good multilineage potentials. The concentration in PRP prepared by group H2M was relatively stable and far above average. All the fibrin fibers were linked together as bridging strands or strings and turned into an inter-connected porous structure for nutrients transportation and regenerative cell migration. We believe that the home-designed group H2M should have a great potential to develop into the final product to meet the requirements of first-line clinical workers.

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The home-designed PRP device is a novel and effective method to remove leukocytes based on cell dimension.

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All the PRP products from the home-designed PRP devices have shown good the cell viability, and the multilineage potentials

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The H2M design could provide the stability of PRP compared to other groups and far above average.

Changes in the extracellular microenvironment and osteogenic responses of mesenchymal stem/stromal cells induced by in vitro direct electrical stimulation

Electrical stimulation (ES) has potential to be an effective tool for bone injury treatment in clinics. However, the therapeutic mechanism associated with ES is still being discussed. This study aims to investigate the initial mechanism of action by characterising the physical and chemical changes in the extracellular environment during ES and correlate them with the responses of mesenchymal stem/stromal cells (MSCs). Computational modelling was used to estimate the electrical potentials relative to the cathode and the current density across the cell monolayer. We showed expression of phosphorylated ERK1/2, c-FOS, c-JUN, and SPP1 mRNAs, as well as the increased metabolic activities of MSCs at different time points. Moreover, the average of 2.5 μM of H₂O₂ and 34 μg/L of dissolved Pt were measured from the electrically stimulated media (ES media), which also corresponded with the increases in SPP1 mRNA expression and cell metabolic activities. The addition of sodium pyruvate to the ES media as an antioxidant did not alter the SPP1 mRNA expression, but eliminated an increase in cell metabolic activities induced by ES media treatment. These findings suggest that H₂O₂ was influencing cell metabolic activity, whereas SPP1 mRNA expression was regulated by other faradic by-products. This study reveals how different electrical stimulation regime alters cellular regenerative responses and the roles of faradic by-products, that might be used as a physical tool to guide and control cell behaviour.

Enhancement and mechanisms of MC3T3-E1 osteoblast-like cell adhesion to albumin through calcium exposure

Serum albumin is the most prominent protein in blood, and it aids in bone fracture healing, though the manner through which enhanced healing occurs is not well understood. This study investigates the influence of calcium on the bioactivity of albumin due to the prevalence of calcium at bone injury sites. Bovine serum albumin (BSA) was exposed to varying concentrations of calcium, adsorbed to tissue culture polystyrene, and the subsequent BSA-coated surfaces were evaluated with calcium titration, and cell adhesion, viability, and binding inhibition studies. Calcium-modified BSA improved overall MC3T3-E1 osteoblast-like cell adhesion, although high calcium concentrations induced cell death. Inhibiting specific integrins revealed that without calcium exposure, cell binding to BSA was primarily mediated by integrins that typically bind to the GFOGER sequence of collagen. As calcium exposure increases, the primary binding interaction transitioned to integrins known to bind RGD. However, cell binding to calcium-modified BSA was not completely eliminated during the inhibition studies indicating additional unidentified binding interactions occur. Overall, these results suggest that the exposure to calcium induces conformational changes that affect the cell-binding bioactivity of BSA, which may explain the beneficial impact of albumin in bone tissue.

Zoledronic Acid-Loaded β-TCP Inhibits Tumor Proliferation and Osteoclast Activation: Development of a Functional Bone Substitute for an Efficient Osteosarcoma Treatment

Osteosarcoma has a poor survival rate due to relapse and metastasis. Zoledronic acid (ZOL), an anti-resorptive and anti-tumor agent, is used for treating osteosarcoma. Delivery of ZOL to the target region is difficult due to its high binding affinity to bone minerals. This study developed a novel treatment for osteosarcoma by delivering ZOL to the target region locally and sustainably. In this study, we fabricated a novel bone substitute by loading ZOL on β-tricalcium phosphate (β-TCP). The ZOL-loaded β-TCP (ZOL/β-TCP) would be expected to express the inhibitory effects via both bound-ZOL (bound to β-TCP) and free-ZOL (release from ZOL/β-TCP). To explore the ability to release ZOL from the ZOL/β-TCP, the amount of released ZOL was measured. The released profile indicates that a small amount of ZOL was released, and most of it remained on the β-TCP. Our data showed that ZOL/β-TCP could successfully express the effects of ZOL via both bound-ZOL and free-ZOL. In addition, we examined the biological effects of bound/free-ZOL using osteosarcoma and osteoclasts (target cells). The results showed that two states of ZOL (bound/free) inhibit target cell activities. As a result, ZOL/β-TCP is a promising candidate for application as a novel bone substitute.

iRoot SP Promotes Osteo/Odontogenesis of Bone Marrow Mesenchymal Stem Cells via Activation of NF-κB and MAPK Signaling Pathways

The regeneration of bone and tooth tissues, and related cellular therapies, has attracted widespread attention. Bone marrow mesenchymal stem cells (BMSCs) are potential candidates for such regeneration. iRoot SP is a premixed bioceramic root canal sealer widely used in clinical settings. However, the effect of iRoot SP on the biological features of BMSCs has not been elucidated. In the present study, we found that 0.2 mg/ml iRoot SP conditioned medium promoted osteo/odontogenic differentiation and enhanced mineralization of BMSCs without affecting the proliferative ability. Mechanistically, the NF-κB and MAPK signaling pathways were activated in SP-treated BMSCs, and differentiation was inhibited when cultured with the specific inhibitor. Taken together, these findings demonstrate that iRoot SP promotes osteo/odontogenic differentiation of BMSCs via the NF-κB and MAPK signaling pathways, which could provide a new theoretical basis for clinical applications of iRoot SP and a new therapeutic target for the regeneration of bone and tooth tissue in the future.