In vitro proliferation and osteogenic differentiation of human bone marrow-derived mesenchymal stem cells cultured with hardystonite (Ca2ZnSi 2O7) and {beta}-TCP ceramics

3D-plotted zinc silicate/β-tricalcium phosphate ceramic scaffolds enable fast osteogenesis by activating the p38 signaling pathway

Biomaterials in combination with multiple bioactive ions could create a favorable microenvironment for bone remolding. Herein, zinc silicate/β-tricalcium phosphate (ZS/β-TCP) composite ceramic scaffolds with different amounts of ZS (5, 10, and 15 wt%) were constructed using a three-dimensional fiber deposition (3DF) technique. The physicochemical, osteogenic and angiogenic properties of these interconnected macroporous scaffolds were investigated systematically. Simultaneously, GeneChip, alkaline phosphatase (ALP), western blot (WB) and polymerase chain reaction (PCR) were utilized to elucidate the underlying mechanism of the enhancement in osteogenic differentiation. The results showed that the incorporation of ZS significantly improved the mechanical performance by more than 5 fold in comparison with the β-TCP ceramic scaffold (4.79 ± 0.99 MPa). The ZS modified β-TCP scaffolds greatly supported the cytoactivity, adhesion, proliferation of mouse bone marrow mesenchymal stem cells (mBMSCs) and human umbilical vein endothelial cells (HUVECs). The expression levels of osteogenic genes and proteins as well as angiogenic genes were markedly upregulated by the sustained release of bioactive ions (mainly Si and Zn) from the composite scaffolds. The 10ZS/β-TCP demonstrated the best overall performance in vitro. Moreover, the 10ZS/β-TCP displayed a high bone volume fraction, bone maturity and angiogenesis after implantation in the rat skull defects for 6 weeks. It was further verified that ZS/β-TCP scaffolds stimulated the osteogenic differentiation of mBMSCs by activating the p38 signaling pathway directly. The 10ZS/β-TCP ceramic scaffold holds great potential for the fast repair of bone defects, and deep understanding of the mechanism will facilitate the formulation of new strategies for bone repair.

Trends of calcium silicate biomaterials in medical research and applications: A bibliometric analysis from 1990 to 2020

Background: Calcium silicate biomaterials (CSB) have witnessed rapid development in the past 30 years. This study aimed to accomplish a comprehensive bibliometric analysis of the published research literature on CSB for biomedical applications and explore the research hotspot and current status.

Methods: Articles related to CSB published in the last three decades (1990–2020) were retrieved from Web of Science Core Collection. The R bibliometrix package and VOSviewer were used to construct publication outputs and collaborative networking among authors, their institutes, countries, journals’ matrices and keywords plus.

Results: A total of 872 publications fulfilling the search criteria were included. CSB is mainly reported for bone tissues and dental applications. Among researchers, Chang J from Chinese Academy of Sciences and Gandolfi MG from the University of Bologna are the most productive author in these two fields, respectively. China was the leading contributor to the research on CSB in the medical field. A total of 130 keywords appeared more ten or more times were identified. The term “mineral trioxide aggregate” ranked first with 268 occurrences. The co-occurrence analysis identified three major clusters: CSB in dentistry, bone tissue and vitro bioactivity.

Conclusion: Calcium silicate biomaterials have a promising scope for various biomedical applications ranging from regeneration of hard tissues (bone and teeth) to skin, tumor, cardiac muscle and other soft tissues. This study may help researchers further understand the frontiers of the field.

Next-generation finely controlled graded porous antibacterial bioceramics for high-efficiency vascularization in orbital reconstruction

Eyeball loss due to severe ocular trauma, intraocular malignancy or infection often requires surgical treatment called orbital implant reconstruction to rehabilitate the orbital volume and restore the aesthetic appearance. However, it remains a challenge to minimize the postoperative exposure and infection complications due to the inert nature of conventional orbital implants. Herein, we developed a novel Ca–Zn-silicate bioceramic implant with multi-functions to achieve the expected outcomes. The porous hardystonite (Ca₂ZnSi₂O₇) scaffolds with triply periodic minimal surfaces (TPMS)-based pore architecture and graded pore size distribution from center to periphery (from 500 to 800 μm or vice versa) were fabricated through the digital light processing (DLP) technique, and the scaffolds with homogeneous pores (500 or 800 μm) were fabricated as control. The graded porous scaffolds exhibited a controlled bio-dissolving behavior and intermediate mechanical strength in comparison with the homogeneous counterparts, although all of porous implants presented significant antibacterial potential against S. aureus and E. coli. Meanwhile, the pore size-increasing scaffolds indicated more substantial cell adhesion, cell viability and angiogenesis-related gene expression in vitro. Furthermore, the gradually increasing pore feature exhibited a stronger blood vessel infiltrating potential in the dorsal muscle embedding model, and the spherical implants with such pore structure could achieve complete vascularization within 4 weeks in the eyeball enucleation rabbit models. Overall, our results suggested that the novel antibacterial hardystonite bioceramic with graded pore design has excellent potential as a next-generation orbital implant, and the pore topological features offer an opportunity for the improvement of biological performances in orbital reconstruction.

•

The graded porous bioceramics were fabricated through computer-assisted design and digital light processing technique.

•

The graded pore architecture could control the biodegradation and mechanical behavior of porous bioceramics.

•

The porous Ca-Zn-silicate bioceramics exhibited significant antibacterial potentials against S. aureus and E. coli.

•

The gradually increasing pore size feature of scaffolds contributes to cell activity and vascular infiltration.

•

The graded porous bioceramics implants achieved complete vascularization within 4 weeks in the enucleation animal model.

Synthetic electrospun nanofibers as a supportive matrix in osteogenic differentiation of induced pluripotent stem cells

Continuous remodeling is not able to repair large bone defects. Bone tissue engineering is aimed to repair these defects by creating bone grafts. To do this, several technologies and biomaterials have been employed to fabricate an in vivo-like supportive matrix. Electrospinning is a versatile technique to fabricate porous matrices with interconnected pores and high surface area, replicating in vivo microenvironment. Electrospun scaffolds have been used in a large number of studies to provide a matrix for bone regeneration and osteogenic differentiation of stem cells such as induced pluripotent stem cells (iPSCs). Electrospinning uses both natural and synthetic polymers, either alone or in combination, to fabricate scaffolds. Among them, synthetic polymers have had a great promise in bone regeneration and repair. They allow the fabrication of biocompatible and biodegradable scaffolds with high mechanical properties, suitable for bone engineering. Furthermore, several attempts have done to increase the osteogenic properties of these scaffolds. This paper reviewed the potential of synthetic electrospun scaffolds in osteogenic differentiation of iPSCs. In addition, the approaches to improve the osteogenic differentiation of these scaffolds are addressed.

In vitro comparison of nanofibrillar and macroporous-spongious composite tissue scaffolds for periodontal tissue engineering

PURPOSE/AIM OF THE STUDY

The ultimate goal of periodontal treatment is to regenerate the lost periodontal tissues. The interest in nanomaterials in dentistry is growing rapidly and has focused on improvements in various biomedical applications, such as periodontal regeneration and periodontal tissue engineering. To enhance periodontal tissue regeneration, hydroxyapatite (HA) was used in conjunction with other scaffold materials, such as Poly lactic-co-glycolic-acid (PLGA) and collagen (C). The main target of this study was to compare the effects of nano and macrostructures of the tissue scaffolds on cell behavior in vitro for periodontal tissue engineering.

MATERIALS AND METHODS

Nanofibrillar and macroporous-spongious composite tissue scaffolds were produced using PLGA/C/HA. Subgroups with BMP-2 signal molecule and without HA were also created. The scaffolds were characterized by FTIR, SEM/EDX techniques, and mechanical tests. The scaffolds were compared in the periodontal ligament (PDL) and MCT3-E1 cell cultures. The cell behaviors; adhesions by SEM, proliferation by WST-1, differentiation by ALP and mineralization with Alizarin Red Tests were determined.

RESULTS

Cell adhesion and mineralization were higher in the nanofibrillar scaffolds compared to the macroporous-spongious scaffolds. Macroporous-spongious scaffolds seemed better for the proliferation of PDL cells and differentiation of MC3T3-E1-preosteoblastic cells, while nanofibrillar scaffolds were more convenient for the differentiation of PDL cells and proliferation of MC3T3-E1-preosteoblastic cells.

CONCLUSIONS

In general, nanofibrillar scaffolds showed more favorable results in cell behaviors, compared to the macroporous-spongious scaffolds, and mostly, BMP-2 and HA promoted the activities of the cells.

Calcium silicate enhances immunosuppressive function of MSCs to indirectly modulate the polarization of macrophages

Bioactive silicate ceramics (BSCs) have been widely reported to be able to induce bone tissue regeneration, but the underlying mechanisms have not been fully elucidated. Previous studies have reported that ionic products of BSCs can promote bone regeneration by directly simulating osteogenic differentiation of mesenchymal stem cells (MSCs) and modulating the polarization of macrophages to create a favorable inflammation microenvironment for initiating bone regeneration cascades. However, the immunomodulatory ability of MSCs also plays a critical role in bone regeneration but the effects of BSCs on the immunomodulatory ability of MSCs have been rarely investigated. This study aims to investigate the effects of ionic products of BSCs on the immunoregulatory ability of MSCs to further understand the mechanism of BSCs enhancing bone regeneration. Results showed that ionic products of calcium silicate (CS), one of the representative BSCs, could enhance the immunosuppressive function of human bone marrow mesenchymal stem cells (HBMSCs) by up-regulating the expression of immunosuppressive factors in HBMSCs via NF-κB pathway. In addition, CS-activated HBMSCs showed stronger stimulatory effects on M2 polarization of macrophages than CS ionic products. Furthermore, the macrophages educated by CS-activated HBMSCs showed stronger stimulatory effects on the early osteogenic differentiation of HBMSCs than the ones regulated by CS ionic products. These results not only provide further understanding on the mechanism of BSCs enhancing bone regeneration but also suggest that it is critical to consider the effects of biomaterials on the immunomodulatory function of the tissue forming cells when the immunomodulatory function of biomaterials is investigated.

Regeneration enhanced in critical-sized bone defects using bone-specific extracellular matrix protein

Extracellular matrix (ECM) products have the potential to improve cellular attachment and promote tissue-specific development by mimicking the native cellular niche. In this study, the therapeutic efficacy of an ECM substratum produced by bone marrow stem cells (BM-MSCs) to promote bone regeneration in vitro and in vivo were evaluated. Fluorescence-activated cell sorting analysis and phenotypic expression were employed to characterize the in vitro BM-MSC response to bone marrow specific ECM (BM-ECM). BM-ECM encouraged cell proliferation and stemness maintenance. The efficacy of BM-ECM as an adjuvant in promoting bone regeneration was evaluated in an orthotopic, segmental critical-sized bone defect in the rat femur over 8 weeks. The groups evaluated were either untreated (negative control); packed with calcium phosphate granules or granules+BM-ECM free protein and stabilized by collagenous membrane. Bone regeneration in vivo was analyzed using microcomputed tomography and histology. in vivo results demonstrated improvements in mineralization, osteogenesis, and tissue infiltration (114 ± 15% increase) in the BM-ECM complex group from 4 to 8 weeks compared to mineral granules only (45 ± 21% increase). Histological observations suggested direct apposition of early bone after 4 weeks and mineral consolidation after 8 weeks implantation for the group supplemented with BM-ECM. Significant osteoid formation and greater functional bone formation (polar moment of inertia was 71 ± 0.2 mm4 with BM-ECM supplementation compared to 48 ± 0.2 mm4 in untreated defects) validated in vivo indicated support of osteoconductivity and increased defect site cellularity. In conclusion, these results suggest that BM-ECM free protein is potentially a therapeutic supplement for stemness maintenance and sustaining osteogenesis.

Highly Porous Polymer-Derived Bioceramics Based on a Complex Hardystonite Solid Solution

Highly porous bioceramics, based on a complex hardystonite solid solution, were developed from silicone resins and micro-sized oxide fillers fired in air at 950 °C. Besides CaO, SrO, MgO, and ZnO precursors, and the commercial embedded silicone resins, calcium borate was essential in providing the liquid phase upon firing and favouring the formation of an unprecedented hardystonite solid solution, corresponding to the formula (Ca0.70Sr0.30)2(Zn0.72Mg0.15Si0.13) (Si0.85B0.15)2O7. Silicone-filler mixtures could be used in the form of thick pastes for direct ink writing of reticulated scaffolds or for direct foaming. The latter shaping option benefited from the use of hydrated calcium borate, which underwent dehydration, with water vapour release, at a low temperature (420 °C). Both scaffolds and foams confirmed the already-obtained phase assemblage, after firing, and exhibited remarkable strength-to-density ratios. Finally, preliminary cell tests excluded any cytotoxicity that could be derived from the formation of a boro-silicate glassy phase.

Hardystonite-Coated Poly(l-lactide) Nanofibrous Scaffold and Efficient Osteogenic Differentiation of Adipose-Derived Mesenchymal Stem Cells

In this study, a ceramic-coated nanofibrous scaffold has been fabricated to biomimic the microstructure of natural extracellular matrix and the stiffening inorganic compartment of bone. Poly-l-lactic acid (PLLA) nanofibers were electrospun and exposed to oxygen plasma to induce hydrophilicity and promote ceramic adsorption. Hardystonite (HS), which possesses superior osteoinduction potential over hydroxyapatite, was coated on plasma-treated PLLA nanofibers by drenching the nanofibers in HS suspension. Pure and composite PLLA-based scaffolds were characterized in terms of physical and biological properties. In vitro cultivation of adipose-derived mesenchymal stem cells (AMSCs) on the scaffolds displayed that the composite scaffold is able to further support cell attachment and proliferation. In case of osteogenic differentiation of AMSCs, HS coating significantly increased the synthesis and activity of alkaline phosphate over 21 days period. In addition, the composite scaffold showed improved mineralization. The expression level of osteonectin and osteocalcin genes was significantly enhanced by HS coating of nanofibers. The biological improvement of PLLA nanofibrous matrix in the presence of HS nanoparticles could either be attributed to the release and stimulatory effect of constituent ions of HS or to the modification of chemico-physical properties of the resultant ceramic by silicon and zinc present in HS.

Doped Calcium Silicate Ceramics: A New Class of Candidates for Synthetic Bone Substitutes

Doped calcium silicate ceramics (DCSCs) have recently gained immense interest as a new class of candidates for the treatment of bone defects. Although calcium phosphates and bioactive glasses have remained the mainstream of ceramic bone substitutes, their clinical use is limited by suboptimal mechanical properties. DCSCs are a class of calcium silicate ceramics which are developed through the ionic substitution of calcium ions, the incorporation of metal oxides into the base binary xCaO-ySiO₂ system, or a combination of both. Due to their unique compositions and ability to release bioactive ions, DCSCs exhibit enhanced mechanical and biological properties. Such characteristics offer significant advantages over existing ceramic bone substitutes, and underline the future potential of adopting DCSCs for clinical use in bone reconstruction to produce improved outcomes. This review will discuss the effects of different dopant elements and oxides on the characteristics of DCSCs for applications in bone repair, including mechanical properties, degradation and ion release characteristics, radiopacity, and biological activity (in vitro and in vivo). Recent advances in the development of DCSCs for broader clinical applications will also be discussed, including DCSC composites, coated DCSC scaffolds and DCSC-coated metal implants.

Silicate-based bioceramics regulating osteoblast differentiation through a BMP2 signalling pathway

Si-containing bioactive ionic products released from silicate-based bioceramics activate Smad1/5-mediated BMP2 signaling pathways.

A space network structure constructed by tetraneedlelike ZnO whiskers supporting boron nitride nanosheets to enhance comprehensive properties of poly(L-lacti acid) scaffolds

In this study, the mechanical strength and modulus of poly(L-lacti acid) (PLLA) scaffolds were enhanced with the mechanical properties of boron nitride nanosheets (BNNSs) and tetraneedlelike ZnO whiskers (T-ZnOw). The adhesion and proliferation of cells were improved as well as osteogenic differentiation of stem cells was increased. Their dispersion statues in PLLA matrix were improved through a space network structure constructed by three-dimensional T-ZnOw supporting two-dimensional BNNSs. The results showed that the compressive strength, modulus and Vickers hardness of the scaffolds with incorporation of 1 wt% BNNSs and 7 wt% T-ZnOw together were about 96.15%, 32.86% and 357.19% higher than that of the PLLA scaffolds, respectively. This might be due to the effect of the pull out and bridging of BNNSs and T-ZnOw as well as the crack deflection, facilitating the formation of effective stress transfer between the reinforcement phases and the matrix. Furthermore, incorporation of BNNSs and T-ZnOw together into PLLA scaffolds was beneficial for attachment and viability of MG-63 cells. More importantly, the scaffolds significantly increased proliferation and promoted osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). The enhanced mechanical and biological properties provide the potentials of PLLA/BNNSs/T-ZnOw scaffolds for the application into bone tissue engineering.

Bioactive calcium silicate extracts regulate the morphology and stemness of human embryonic stem cells at the initial stage

We shed light on the impact of CS extracts on hESC's proliferation and differentiation, which is not clearly investigated.

Characterization of human periodontal ligament cells cultured on three-dimensional biphasic calcium phosphate scaffolds in the presence and absence of L-ascorbic acid, dexamethasone and β-glycerophosphate in vitro

The aim of this study was to evaluate the effect of porous biphasic calcium phosphate (BCP) scaffolds on the proliferation and osteoblastic differentiation of human periodontal ligament cells (hPDLCs) in the presence and absence of osteogenic inducer (L-ascorbic acid, dexamethasone and β-glycerophosphate). The cell growth within the scaffolds in the absence of osteogenic inducers was studied by cell counting kit-8 (CCK-8) assay and scanning electron microscopy (SEM). Alkaline phosphatase (ALP) activity and osteoblastic differentiation markers of hPDLCs in BCP scaffolds were examined in the presence and absence of osteogenic inducers. The cell number of hPDLCs in the BCP scaffolds was less than that of hPDLCs cultured in microplates (control). SEM images showed that cells successfully adhered to the BCP scaffolds and spread amongst the pores; they also produced abundant extracellular cell matrix. In the presence and absence of osteogenic inducers, the ALP activity of hPDLCs within BCP scaffolds was suppressed in varying degrees at all time-points. In the absence of osteogenic inducers, hPDLCs in BCP scaffolds express significant higher levels of osteopontin (OPN) mRNA than the control, and there were no significant differences for Runx2 and osteocalcin (OCN) mRNA levels compared with those cultured in microplates. In the presence of osteogenic inducers, Runx2 expression levels were significantly higher than those in control. OPN and OCN mRNA levels were downregulated slightly. Three-dimensional porous BCP scaffolds are able to stimulate the osteoblastic differentiation of hPDLCs in the presence and absence of osteogenic inducer and may be capable of supporting hPDLC-mediated bone formation.

Skeletal tissue engineering using mesenchymal or embryonic stem cells: clinical and experimental data

INTRODUCTION

Mesenchymal stem cells (MSCs) can be obtained from a wide variety of tissues for bone tissue engineering such as bone marrow, adipose, birth-associated, peripheral blood, periosteum, dental and muscle. MSCs from human fetal bone marrow and embryonic stem cells (ESCs) are also promising cell sources.

AREAS COVERED

In vitro, in vivo and clinical evidence was collected using MEDLINE® (1950 to January 2014), EMBASE (1980 to January 2014) and Google Scholar (1980 to January 2014) databases.

EXPERT OPINION

Enhanced results have been found when combining bone marrow-derived mesenchymal stem cells (BMMSCs) with recently developed scaffolds such as glass ceramics and starch-based polymeric scaffolds. Preclinical studies investigating adipose tissue-derived stem cells and umbilical cord tissue-derived stem cells suggest that they are likely to become promising alternatives. Stem cells derived from periosteum and dental tissues such as the periodontal ligament have an osteogenic potential similar to BMMSCs. Stem cells from human fetal bone marrow have demonstrated superior proliferation and osteogenic differentiation than perinatal and postnatal tissues. Despite ethical concerns and potential for teratoma formation, developments have also been made for the use of ESCs in terms of culture and ideal scaffold.

FGF-2 induces the proliferation of human periodontal ligament cells and modulates their osteoblastic phenotype by affecting Runx2 expression in the presence and absence of osteogenic inducers

The exact phenotype of human periodontal ligament cells (hPDLCs) remains a controversial area. Basic fibroblast growth factor (FGF-2) exhibits various functions and its effect on hPDLCs is also controversial. Therefore, the present study examined the effect of FGF-2 on the growth and osteoblastic phenotype of hPDLCs with or without osteogenic inducers (dexamethasone and β-glycerophosphate). FGF-2 was added to defined growth culture medium and osteogenic inductive culture medium. Cell proliferation, osteogenic differentiation and mineralization were measured. The selected differentiation markers, Runx2, collagen type I, α1 (Col1a1), osteocalcin (OCN) and epidermal growth factor receptor (EGFR), were investigated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Runx2 and OCN protein expression was measured by western blotting. FGF-2 significantly increased the proliferation of hPDLCs, but did not affect alkaline phosphatase activity. RT-qPCR analysis revealed enhanced mRNA expression of Runx2, OCN and EGFR, but suppressed Col1a1 gene expression in the absence of osteogenic inducers, whereas all these gene levels had no clear trend in their presence. The Runx2 protein expression was clearly increased, but the OCN protein level showed no evident trend. The mineralization assay demonstrated that FGF-2 inhibited mineralized matrix deposition with osteogenic inducers. These results suggested that FGF-2 induces the growth of immature hPDLCs, which is a competitive inhibitor of epithelial downgrowth, and suppresses their differentiation into mineralized tissue by affecting Runx2 expression. Therefore, this may lead to the acceleration of periodontal regeneration.

Silica nanoparticles increase human adipose tissue-derived stem cell proliferation through ERK1/2 activation

Background

Silicon dioxide composites have been found to enhance the mechanical properties of scaffolds and to support growth of human adipose tissue-derived stem cells (hADSCs) both in vitro and in vivo. Silica (silicon dioxide alone) exists as differently sized particles when suspended in culture medium, but it is not clear whether particle size influences the beneficial effect of silicon dioxide on hADSCs. In this study, we examined the effect of different sized particles on growth and mitogen-activated protein kinase signaling in hADSCs.

Methods

Silica gel was prepared by a chemical reaction using hydrochloric acid and sodium silicate, washed, sterilized, and suspended in serum-free culture medium for 48 hours, and then sequentially filtered through a 0.22 μm filter (filtrate containing nanoparticles smaller than 220 nm; silica NPs). hADSCs were incubated with silica NPs or 3 μm silica microparticles (MPs), examined by transmission electron microscopy, and assayed for cell proliferation, apoptosis, and mitogen-activated protein kinase signaling.

Results

Eighty-nine percent of the silica NPs were around 50–120 nm in size. When hADSCs were treated with the study particles, silica NPs were observed in endocytosed vacuoles in the cytosol of hADSCs, but silica MPs showed no cell entry. Silica NPs increased the proliferation of hADSCs, but silica MPs had no significant effect in this regard. Instead, silica MPs induced slight apoptosis. Silica NPs increased phosphorylation of extracellular signal-related kinase (ERK)1/2, while silica MPs increased phosphorylation of p38. Silica NPs had no effect on phosphorylation of Janus kinase or p38. Pretreatment with PD98059, a MEK inhibitor, prevented the ERK1/2 phosphorylation and proliferation induced by silica NPs.

Conclusion

Scaffolds containing silicon dioxide for tissue engineering may enhance cell growth through ERK1/2 activation only when NPs around 50–120 nm in size are included, and single component silica-derived NPs could be useful for bioscaffolds in stem cell therapy.

Investigating the effect of SiO2-TiO 2-CaO-Na 2O-ZnO bioactive glass doped hydroxyapatite: characterisation and structural evaluation

The effects of increasing bioactive glass additions, SiO2-TiO2-CaO-Na2O-ZnO up to 25 wt% in increments of 5 wt%, on the physical and mechanical properties of hydroxyapatite (HA) sintered at 900, 1000, 1100 and 1200 °C for 2 h was investigated. Increasing both the glass content and the temperature resulted in increased HA decomposition. This resulted in the formation of a number of bioactive phases. However the presence of the liquidus glass phase did not result in increased densification levels. At 1000 and 1100 °C the additions of 5 wt% glass resulted in a decrease in density which never recovered with increasing glass content. At 1200 °C a cyclic pattern resulted from increasing glass content. There was no direct relationship between strength and density with all samples experiencing no change or a decrease in strength with increasing glass content. Weibull statistics displayed no pattern with increasing glass content.

Effect of biomimetic zinc-containing tricalcium phosphate (Zn-TCP) on the growth and osteogenic differentiation of mesenchymal stem cells

Several studies have shown the effectiveness of zinc-tricalcium phosphate (Zn-TCP) for bone tissue engineering. In this study, marine calcareous foraminifera possessing uniform pore size distribution were hydrothermally converted to Zn-TCP. The ability of a scaffold to combine effectively with mesenchymal stem cells (MSCs) is a key tissue-engineering aim. In order to demonstrate the osteogenic ability of MSCs with Zn-TCP, the scaffolds were cultured in an osteogenic induction medium to elicit an osteoblastic response. The physicochemical properties of Zn-TCP were characterized by XRD, FT-IR and ICP-MS. MSCs were aspirated from rat femurs and cultured for 3 days before indirectly placing four samples into each respective well. After culture for 7, 10 and 14 days, osteoblastic differentiation was evaluated using alizarin red S stain, measurement of alkaline phosphatase (ALP) levels, cell numbers and cell viability. XRD and FT-IR patterns both showed the replacement of CO(3)(2-) with PO(4)(3-). Chemical analysis showed zinc incorporation of 5 mol%. Significant increases in cell numbers were observed at 10 and 14 days in the Zn-TCP group, while maintaining high levels of cell viability (> 90%). ALP activity in the Zn-TCP group was statistically higher at 10 days. Alizarin red S staining also showed significantly higher levels of calcium mineralization in Zn-TCP compared with the control groups. This study showed that MSCs in the presence of biomimetically derived Zn-TCP can accelerate their differentiation to osteoblasts and could potentially be useful as a scaffold for bone tissue engineering.

Probe spectrum measurements of Eu3+ions as a relevant tool for monitoring in vitro hydroxyapatite formation in a new borate biomaterial

CaB₂O₄powders and ceramics were prepared by the conventional solid-state reaction.

Stimulatory effects of the ionic products from Ca-Mg-Si bioceramics on both osteogenesis and angiogenesis in vitro

Ideal biomaterials for bone tissue engineering should have the capability to guide the osteogenic differentiation of mesenchymal stem cells and, at the same time, to stimulate angiogenesis of endothelia cells. In this study it was found that three Ca-Mg-Si-containing bioceramics (bredigite Ca7MgSi4O16, akermanite Ca2MgSi2O7 and diopside CaMgSi2O6) had osteogenic and angiogenic potential. The effects of three silicate ceramics on the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) and the angiogenesis of human aortic endothelial cells (HAECs) were explored in comparison with β-tricalcium phosphate (β-TCP) bioceramics. The proliferation, alkaline phosphatase (ALPase) activity and bone-related gene expression (COL1, ALPase, OP, BSP and OC) of hBMSCs were significantly enhanced upon stimulation with ionic extracts of these silicate bioceramics. In addition, the results showed that extracts from the three silicate bioceramics also stimulated HAEC proliferation and in vitro angiogenesis with improved NO synthesis and angiogenic gene expression (KDR, FGFR1, ACVRL1 and NOS3). Among the three silicate ceramics bredigite showed the highest osteogenic and angiogenic potential and with the highest extract Si (possibly Si(OH)3O(-)) concentration, while diopside had the lowest osteogenic and angiogenic potential with the lowest extract Si concentration. Furthermore, it was found that the concentration of Si ions in extracts of the three silicate bioceramics was obviously higher than that of β-TCP ceramics, indicating an important role of Si ions in stimulating cell proliferation, osteogenic differentiation and angiogenesis. The results suggest that the silicate-based akermanite and bredigite ceramics might be good scaffold biomaterials for bone tissue engineering applications due to their distinctive dual functions of osteogenesis/angiogenesis stimulation.

In vitro and in vivo evaluation of zinc-modified ca-si-based ceramic coating for bone implants

The host response to calcium silicate ceramic coatings is not always favorable because of their high dissolution rates, leading to high pH within the surrounding physiological environment. Recently, a zinc-incorporated calcium silicate-based ceramic Ca2ZnSi2O7 coating, developed on a Ti-6Al-4V substrate using plasma-spray technology, was found to exhibit improved chemical stability and biocompatibility. This study aimed to investigate and compare the in vitro response of osteoblastic MC3T3-E1 cells cultured on Ca2ZnSi2O7 coating, CaSiO3 coating, and uncoated Ti-6Al-4V titanium control at cellular and molecular level. Our results showed Ca2ZnSi2O7 coating enhanced MC3T3-E1 cell attachment, proliferation, and differentiation compared to CaSiO3 coating and control. In addition, Ca2ZnSi2O7 coating increased mRNA levels of osteoblast-related genes (alkaline phosphatase, procollagen α1(I), osteocalcin), insulin-like growth factor-I (IGF-I), and transforming growth factor-β1 (TGF-β1). The in vivo osteoconductive properties of Ca2ZnSi2O7 coating, compared to CaSiO3 coating and control, was investigated using a rabbit femur defect model. Histological and histomorphometrical analysis demonstrated new bone formation in direct contact with the Ca2ZnSi2O7 coating surface in absence of fibrous tissue and higher bone-implant contact rate (BIC) in the Ca2ZnSi2O7 coating group, indicating better biocompatibility and faster osseointegration than CaSiO3 coated and control implants. These results indicate Ca2ZnSi2O7 coated implants have applications in bone tissue regeneration, since they are biocompatible and able to osseointegrate with host bone.

Silicate bioceramics induce angiogenesis during bone regeneration

The capacity to induce rapid vascular ingrowth during new bone formation is an important feature of biomaterials that are to be used for bone regeneration. Akermanite, a Ca-, Mg- and Si-containing bioceramic, has been demonstrated to be osteoinductive and to promote bone repair. This study further demonstrates the ability of akermanite to promote angiogenesis and investigates the mechanism of this behavior. The akermanite ion extract predominantly caused Si-ion-stimulated proliferation of human aortic endothelial cells. The Si ion in the extract was the most important component for the effect and the most effective concentration was found to be 0.6-2 μg ml(-1). In this range of Si ion concentration, the stimulating effect of the ceramic ion extract was demonstrated by the morphology of cells at the primary, interim and late stages during in vitro angiogenesis using ECMatrix™. The akermanite ion extract up-regulated the expression of genes encoding the receptors of proangiogenic cytokines and also increased the expression level of genes encoding the proangiogenic downstream cytokines, such as nitric oxide synthase and nitric oxide synthesis. Akermanite implanted in rabbit femoral condyle model promoted neovascularization after 8 and 16 weeks of implantation, which further confirmed its stimulation effect on angiogenesis in vivo. These results indicate that akermanite ceramic, an appropriate Si ion concentration source, could induce angiogenesis through increasing gene expression of proangiogenic cytokine receptors and up-regulated downstream signaling. To our knowledge, akermanite ceramic is the first Si-containing ceramic demonstrated to be capable of inducing angiogenesis during bone regeneration.

Bioceramics: from bone regeneration to cancer nanomedicine

Research on biomaterials has been growing in the last few years due to the clinical needs in organs and tissues replacement and regeneration. In addition, cancer nanomedicine has recently appeared as an effective means to combine nanotechnology developments towards a clinical application. Ceramic materials are suitable candidates to be used in the manufacturing of bone-like scaffolds. Bioceramic materials may also be designed to deliver biologically active substances aimed at repairing, maintaining, restoring or improving the function of organs and tissues in the organism. Several materials such as calcium phosphates, glasses and glass ceramics able to load and subsequently release in a controlled fashion drugs, hormones, growth factors, peptides or nucleic acids have been developed. In particular, to prevent post surgical infections bioceramics may be surface modified and loaded with certain antibiotics, thus preventing the formation of bacterial biofilms. Remarkably, mesoporous bioactive glasses have shown excellent characteristics as drug carrying bone regeneration materials. These bioceramics are not only osteoconductive and osteoproductive, but also osteoinductive, and have therefore been proposed as ideal components for the fabrication of scaffolds for bone tissue engineering. A recent promising development of bioceramic materials is related to the design of magnetic mediators against tumors. Magnetic composites are suitable thermoseeds for cancer treatment by hyperthermia. Moreover, magnetic nanomaterials offer a wide range of possibilities for diagnosis and therapy. These nanoparticles may be conjugated with therapeutic agents and heat the surrounding tissue under the action of alternating magnetic fields, enabling hyperthermia of cancer as an effective adjunct to chemotherapy regimens.

The differentiation of human adipose-derived stem cells (hASCs) into osteoblasts is promoted by low amplitude, high frequency vibration treatment

Several studies have demonstrated that tissue culture conditions influence the differentiation of human adipose-derived stem cells (hASCs). Recently, studies performed on SAOS-2 and bone marrow stromal cells (BMSCs) have shown the effectiveness of high frequency vibration treatment on cell differentiation to osteoblasts. The aim of this study was to evaluate the effects of low amplitude, high frequency vibrations on the differentiation of hASCs toward bone tissue. In view of this goal, hASCs were cultured in proliferative or osteogenic media and stimulated daily at 30Hz for 45min for 28days. The state of calcification of the extracellular matrix was determined using the alizarin assay, while the expression of extracellular matrix and associated mRNA was determined by ELISA assays and quantitative RT-PCR (qRT-PCR). The results showed the osteogenic effect of high frequency vibration treatment in the early stages of hASC differentiation (after 14 and 21days). On the contrary, no additional significant differences were observed after 28days cell culture. Transmission Electron Microscopy (TEM) images performed on 21day samples showed evidence of structured collagen fibers in the treated samples. All together, these results demonstrate the effectiveness of high frequency vibration treatment on hASC differentiation toward osteoblasts.

Current trends in mesenchymal stem cell application in bone augmentation: a review of the literature

PURPOSE

The literature regarding mesenchymal stem cell (MSC)-based bone reconstruction techniques are sparse and no comprehensive review of current methods has been performed. The aim of this article was to provide a discussion of clinical and experimental reports of MSC application in the reconstruction of bony defects in live models.

MATERIALS AND METHODS

This search was executed using the PubMed database with various combinations of related keywords. Currently published English-language studies that had applied MSCs as a part of their treatment protocol for reconstruction of bony defects in rat, rabbit, dog, and human models were reviewed. The included studies had reported substantiation that the applied cells were of MSC origin as a part of the study design. Publications inclusive to February 1, 2010 were evaluated. Of review of 187 found abstracts and full texts, 25 articles met the inclusion criteria.

RESULT

Based on this review, tremendous differences exist among investigators for the application of MSCs in bone augmentation procedures. These differences include not only species uniqueness but also a plethora of other variances, such as stem cell source, defect sites and sizes, carriers and constructs, use of additional growth factors, measured parameters, and methods of data collection.

CONCLUSION

Because of the multitude of protocols, range of parameters, and data in the current English-language literature, this review did not reach any significant conclusion as to the "most predictable" model in stem cell reconstruction. However, it does "shed light" on the need for additional collaborated studies using similar homogenous designs and data analysis in advancing the science of bone reconstruction using MSCs.

A review of the biological response to ionic dissolution products from bioactive glasses and glass-ceramics

Several inorganic materials such as special compositions of silicate glasses, glass-ceramics and calcium phosphates have been shown to be bioactive and resorbable and to exhibit appropriate mechanical properties which make them suitable for bone tissue engineering applications. However, the exact mechanism of interaction between the ionic dissolution products of such inorganic materials and human cells are not fully understood, which has prompted considerable research work in the biomaterials community during the last decade. This review comprehensively covers literature reports which have investigated specifically the effect of dissolution products of silicate bioactive glasses and glass-ceramics in relation to osteogenesis and angiogenesis. Particularly, recent advances made in fabricating dense biomaterials and scaffolds doped with trace elements (e.g. Zn, Sr, Mg, and Cu) and investigations on the effect of these elements on the scaffold biological performance are summarized and discussed in detail. Clearly, the biological response to artificial materials depends on many parameters such as chemical composition, topography, porosity and grain size. This review, however, focuses only on the ion release kinetics of the materials and the specific effect of the released ionic dissolution products on human cell behaviour, providing also a scope for future investigations and identifying specific research needs to advance the field. The biological performance of pure and doped silicate glasses, phosphate based glasses with novel specific compositions as well as several other silicate based compounds are discussed in detail. Cells investigated in the reviewed articles include human osteoblastic and osteoclastic cells as well as endothelial cells and stem cells.

EF1alpha and RPL13a represent normalization genes suitable for RT-qPCR analysis of bone marrow derived mesenchymal stem cells

Background

RT-qPCR analysis is a widely used method for the analysis of mRNA expression throughout the field of mesenchymal stromal cell (MSC) research. Comparison between MSC studies, both in vitro and in vivo, are challenging due to the varied methods of RT-qPCR data normalization and analysis. Therefore, this study focuses on putative housekeeping genes for the normalization of RT-qPCR data between heterogeneous commercially available human MSC, compared with more homogeneous populations of MSC such as MIAMI and RS-1 cells.

Results

Eight genes including; ACTB, B2M, EF1α, GAPDH, RPL13a, YWHAZ, UBC and HPRT1 were tested as possible housekeeping genes based on their expression level and variability. EF1α and RPL13a were validated for RT-qPCR analysis of MIAMI cells during expansion in varied oxygen tensions, endothelial differentiation, neural precursor enrichment, and during the comparison with RS-1 cells and commercially available MSC. RPL13a and YWHAZ were validated as normalization genes for the cross-species analysis of MIAMI cells in an animal model of focal ischemia. GAPDH, which is one of the most common housekeeping genes used for the normalization of RT-qPCR data in the field of MSC research, was found to have the highest variability and deemed not suitable for normalization of RT-qPCR data.

Conclusions

In order to make comparisons between heterogeneous MSC populations, as well as adult stem cell like MSC which are used in different laboratories throughout the world, it is important to have a standardized, reproducible set of housekeeping genes for RT-qPCR analysis. In this study we demonstrate that EF1α, RPL13a and YWHAZ are suitable genes for the RT-qPCR analysis and comparison of several sources of human MSC during in vitro characterization and differentiation as well as in an ex vivo animal model of global cerebral ischemia. This will allow for the comparative RT-qPCR analysis of multiple MSC populations with the goal of future use in animal models of disease as well as tissue repair.