Effects of high calcium concentration on the functions and interactions of osteoblastic cells and monocytes and on the formation of osteoclast-like cells

Simulation of the bone remodelling microenvironment by calcium compound-loaded hydrogel fibrous membranes for in situ bone regeneration

The endowment of guided bone regeneration (GBR) membranes with the ability to activate the endogenous regenerative capability of bone to regenerate bone defects is of clinical significance. Herein we explored the preparation of the calcium compound (CC) (calcium sulfate (CaSL), calcium hydrophosphate (CaHP), or tricalcium phosphate (TCaP)) loaded ultrathin silk fibroin (SF)/gelatin (G) fibre membranes via electrospinning as the GBR membranes to regenerate the calvarial bone defects. The in vitro experiments demonstrated that the CaSL-loaded ultrathin fibrous membranes could simulate optimally the bone remodelling microenvironment in comparison with the CaHP- and TCaP-loaded fibrous membranes, displaying the highest activity to regulate the migration, proliferation, and differentiation of mesenchymal stem cells (MSCs). Also, the in vivo experiments demonstrated that the CaSL-loaded fibrous membranes presented the highest intrinsic osteoinduction to guide in situ regeneration of bone. Furthermore, the in vivo experiments demonstrated that the as-prepared composite fibrous membranes possessed good degradability. In summary, our results suggested that the CaSL-loaded fibrous membranes with high intrinsic osteoinduction and good degradability have potential to translate into clinical practice.

A comprehensive review on nanocomposite biomaterials based on gelatin for bone tissue engineering

The creation of a suitable scaffold is a crucial step in the process of bone tissue engineering (BTE). The scaffold, acting as an artificial extracellular matrix, plays a significant role in determining the fate of cells by affecting their proliferation and differentiation in BTE. Therefore, careful consideration should be given to the fabrication approach and materials used for scaffold preparation. Natural polypeptides such as gelatin and collagen have been widely used for this purpose. The unique properties of nanoparticles, which vary depending on their size, charge, and physicochemical properties, have demonstrated potential in solving various challenges encountered in BTE. Therefore, nanocomposite biomaterials consisting of polymers and nanoparticles have been extensively used for BTE. Gelatin has also been utilized in combination with other nanomaterials to apply for this purpose. Composites of gelatin with various types of nanoparticles are particularly promising for creating scaffolds with superior biological and physicochemical properties. This review explores the use of nanocomposite biomaterials based on gelatin and various types of nanoparticles together for applications in bone tissue engineering.

Preparation of a cattle bone collagen peptide-calcium chelate by the ultrasound method and its structural characterization, stability analysis, and bioactivity on MC3T3-E1 cells

This study was designed to prepare a cattle bone-derived collagen peptide-calcium chelate by the ultrasound method (CP-Ca-US), and its structure, stability, and bioactivity on MC3T3-E1 cells were characterized. Single-factor experiments optimized the preparation conditions: ultrasound power 90 W, ultrasound time 40 min, CaCl₂/peptides ratio 1/2, pH 7. Under these conditions, the calcium-chelating ability reached 39.48 μg mg^-1. The result of Fourier transform-infrared spectroscopy indicated that carboxyl oxygen and amino nitrogen atoms were chelation sites. Morphological analysis indicated that CP-Ca-US was characterized by a porous surface and large particles. Stability analysis demonstrated that CP-Ca-US was stable in the thermal environment and under intestinal digestion. CP-Ca-US showed more stability in gastric juice than the chelate prepared by the hydrothermal method. Cell experiments indicated that CP-Ca-US increased osteoblast proliferation (proliferation rate 153% at a concentration of 300 μg mL^-1) and altered the cell cycle. Significantly, CP-Ca-US enhanced calcium absorption by interacting with calcium-sensing receptors and promoted the mineralization of MC3T3-E1 cells. This study provides the scientific basis for applying the ultrasound method to prepare peptide-calcium chelates and clarifies the positive role of chelates in bone building.

In Situ Biomimetic Mineralization of Bone-Like Hydroxyapatite in Hydrogel for the Acceleration of Bone Regeneration

A critical-sized bone defect, which cannot be repaired through self-healing, is a major challenge in clinical therapeutics. The combination of biomimetic hydrogels and nano-hydroxyapatite (nano-HAP) is a promising way to solve this problem by constructing an osteogenic microenvironment. However, it is challenging to generate nano-HAP with a similar morphology and structure to that of natural bone, which limits the improvement of bone regeneration hydrogels. Inspired by our previous works on organic-inorganic cocross-linking, here, we built a strong organic-inorganic interaction by cross-linking periosteum-decellularized extracellular matrix and calcium phosphate oligomers, which ensured the in situ mineralization of bone-like nano-HAP in hydrogels. The resulting biomimetic osteogenic hydrogel (BOH) promotes bone mineralization, construction of immune microenvironment, and angiogenesis improvement in vitro. The BOH exhibited acceleration of osteogenesis in vivo, achieving large-sized bone defect regeneration and remodeling within 8 weeks, which is superior to many previously reported hydrogels. This study demonstrates the important role of bone-like nano-HAP in osteogenesis, which deepens the understanding of the design of biomaterials for hard tissue repair. The in situ mineralization of bone-like nano-HAP emphasizes the advantages of inorganic ionic oligomers in the construction of organic-inorganic interaction, which provides an alternative method for the preparation of advanced biomimetic materials.

Evaluation of culture conditions for osteoclastogenesis in RAW264.7 cells

Osteoclasts are the only multinucleated cells in vivo responsible for bone resorption and are vital for regulating bone remodeling and maintaining bone mass. The RAW264.7 cell line is widely used to study osteoclastic differentiation and biological molecular mechanism. However, protocols for inducing osteoclast formation in RAW264.7 cells vary considerably between laboratories, hindering the replication of results. Therefore, we tested the influence of culture conditions on osteoclast differentiation, including cell density and receptor activator of nuclear factor kappa-B ligand (RANKL) concentrations with or without macrophage colony-stimulating factors (M-CSF). Tartrate-resistant acid phosphatase (TRAP) staining was used to detect the morphology of osteoclasts. qPCR was used to detect gene expression of osteoclast-specific gene marker cathepsin K (CTSK), osteoclast transcription factors c-Fos and nuclear factor of activated T cells, cytoplasmic 1 (NFATc1). The bone resorption function was evaluated by a scanning electron microscope (SEM). RANKL treatment increased multinucleated osteoclasts formation and increased CTSK, c-Fos and NFATc1 gene expression. Compared with RANKL treatment, M-CSF significantly decreased multinucleated osteoclasts formation, reduced CTSK gene expression and had little effect on c-Fos and NFATc1 gene expression. Concerning bone resorption activity, RANKL treatment increased bone resorption pits on bovine bone slices. Significantly higher levels of osteoclastogenesis were observed with RAW264.7-cell density of 2×104 cells/well in 24-well plates. Our results suggest that the addition of 50 ng/ml M-CSF has no positive effect on osteoclastogenesis. RANKL treatment and cell density contribute to osteoclast formation, and the optimal conditions are beneficial when exploring osteoclast function and mechanism.

Sustained local ionic homeostatic imbalance caused by calcification modulates inflammation to trigger heterotopic ossification

Heterotopic ossification (HO) is a condition triggered by an injury leading to the formation of mature lamellar bone in extraskeletal soft tissues. Despite being a frequent complication of orthopedic and trauma surgery, brain and spinal injury, the etiology of HO is poorly understood. The aim of this study is to evaluate the hypothesis that a sustained local ionic homeostatic imbalance (SLIHI) created by mineral formation during tissue calcification modulates inflammation to trigger HO. This evaluation also considers the role SLIHI could play for the design of cell-free, drug-free osteoinductive bone graft substitutes. The evaluation contains five main sections. The first section defines relevant concepts in the context of HO and provides a summary of proposed causes of HO. The second section starts with a detailed analysis of the occurrence and involvement of calcification in HO. It is followed by an explanation of the causes of calcification and its consequences. This allows to speculate on the potential chemical modulators of inflammation and triggers of HO. The end of this second section is devoted to in vitro mineralization tests used to predict the ectopic potential of materials. The third section reviews the biological cascade of events occurring during pathological and material-induced HO, and attempts to propose a quantitative timeline of HO formation. The fourth section looks at potential ways to control HO formation, either acting on SLIHI or on inflammation. Chemical, physical, and drug-based approaches are considered. Finally, the evaluation finishes with a critical assessment of the definition of osteoinduction. STATEMENT OF SIGNIFICANCE: The ability to regenerate bone in a spatially controlled and reproducible manner is an essential prerequisite for the treatment of large bone defects. As such, understanding the mechanism leading to heterotopic ossification (HO), a condition triggered by an injury leading to the formation of mature lamellar bone in extraskeletal soft tissues, would be very useful. Unfortunately, the mechanism(s) behind HO is(are) poorly understood. The present study reviews the literature on HO and based on it, proposes that HO can be caused by a combination of inflammation and calcification. This mechanism helps to better understand current strategies to prevent and treat HO. It also shows new opportunities to improve the treatment of bone defects in orthopedic and dental procedures.

Effect of carbonate apatite as a bone substitute on oral mucosal healing in a rat extraction socket: in vitro and in vivo analyses using carbonate apatite

Background

Low bone quantity and quality are serious problems that affect the prognosis of implants in the cosmetic field. Therefore, artificial bone substitutes are frequently used. However, whether there is a difference in the effect of either bone substitute on soft tissue healing is unclear given their greatly different absorbability. In this study, we used hydroxyapatite (HAp) and carbonate apatite (CO₃Ap) as bone substitutes to analyze the epithelial and connective tissue healing after tooth extraction.

Methods

In vitro, oral mucosa-derived epithelial cells (OECs) collected from 4-day-old Wistar rats were seeded on HAp or CO₃Ap and evaluated for adhesion, proliferation, migration, apoptosis, and morphology. Fibroblasts (FBs) were also analyzed for their ability to express collagen. In vivo, the extraction of maxillary right first (M1) and second molars (M2) of 6-week-old male Wistar rats was performed, followed by insertion of HAp or CO₃Ap granules into the M1 and M2 sites. The oral mucosal healing process was then evaluated histochemically after 7 and 14 days.

Results

In vitro, high collagen expression by FBs in the CO₃Ap group was observed and the surface analysis showed spreading of the FBs on the CO₃Ap surface. However, the activity of OECs was suppressed on CO₃Ap. Two weeks after CO₃Ap implantation, soft tissue healing was observed, and recovery of the connective tissue was observed on the remaining CO₃Ap.

Conclusions

Our results suggest that the formation of soft tissues, including connective tissue, was promoted by CO₃Ap in the extraction socket within a short period.

Construction of a drug-containing microenvironment for in situ bone regeneration

Bioactive glass-coated hierarchical porous tricalcium phosphate ceramics were constructed as both bone scaffolds and drug delivery devices to treat S. aureus-infected bone defects.

A biopolymer hydrogel electrostatically reinforced by amino-functionalized bioactive glass for accelerated bone regeneration

Composite hydrogels incorporating natural polymers and bioactive glass (BG) are promising materials for bone regeneration. However, their applications are compromised by the poor interfacial compatibility between organic and inorganic phases. In this study, we developed an electrostatically reinforced hydrogel (CAG) with improved interfacial compatibility by introducing amino-functionalized 45S5 BG to the alginate/gellan gum (AG) matrix. BAG composed of AG and unmodified BG (10 to 100 μm in size) was prepared as a control. Compared with BAG, CAG had a more uniform porous structure with a pore size of 200 μm and optimal compressive strength of 66 kPa. Furthermore, CAG promoted the M2 phenotype transition of macrophages and up-regulated the osteogenic gene expression of stem cells. The new bone formation in vivo was also accelerated due to the enhanced biomineralization of CAG. Overall, this work suggests CAG with improved interfacial compatibility is an ideal material for bone regeneration application.

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.

An in vitro / in vivo release test of risedronate drug loaded nano-bioactive glass composite scaffolds

Three-dimensional (3D) matrices scaffolds play a noteworthy role in promoting cell generation and propagation. In this study, scaffolds prepared from chitosan/polyvinyl alcohol loaded with/without an osteoporotic drug (risedronate) and nano-bioactive glass (nBG) have been developed to promote healing of bone defects. The scaffolds were characterized by scanning electron microscopy (SEM), porosity test as well as mechanical strength. The pattern of drug release and ability to promote the proliferation of Saos-2osteosarcoma cells had also been reported. Osteogenic potential of the scaffolds was evaluated by testing their effect on healing critical-sized dog's mandibular bone defects. Increasing chitosan and nBG in the porous scaffolds induced decrease in drug release, increased the scaffold's strength and supported their cell proliferation, alkaline phosphatase (ALP) activities, as well as increased calcium deposition. Histological and histomorphometric results demonstrated newly formed bone trabeculae inside critical-sized mandibular defects when treated with scaffolds. Trabecular thickness, bone volume/tissue volume and the percentage of mature collagen fibers increased in groups treated with scaffolds loaded with 10% nBG and risedronate or loaded with 30% nBG with/without risedronate compared with those treated with non-loaded scaffolds and empty control groups. These findings confirmed the potential osteogenic activity of chitosan/polyvinyl alcohol-based scaffolds loaded with risedronate and nBG.

Bone tissue engineering gelatin-hydroxyapatite/graphene oxide scaffolds with the ability to release vitamin D: fabrication, characterization, and in vitro study

Developing smart scaffolds with drug release capability is one of the main approaches to bone tissue engineering. The current study involves the fabrication of novel gelatin (G)-hydroxyapatite (HA)-/vitamin D (VD)-loaded graphene oxide (GO) scaffolds with different concentrations through solvent-casting method. Characterizations confirmed the successful synthesis of HA and GO, and VD was loaded in GO with 36.87 ± 4.87% encapsulation efficiency. Physicochemical characterizations showed that the scaffold containing 1% VD-loaded GO had the best mechanical properties and its porosity percentage and density was in the range of natural spongy bone. All scaffolds were degraded after 1-month, subjecting to phosphate buffer saline. The release profile of VD did not match any mathematical kinetics model, porosities and the degradation rate of the scaffolds were dominant controlling factors of release behavior. Studies on the bioactivity of scaffolds immersed in simulated body fluid indicated that VD and HA could encourage the formation of secondary apatite crystals in vitro. Buccal fat pad-derived stem cells (BFPSCs) were seeded on the scaffolds, MTT assay, alkaline phosphatase activity as an indicator of osteoconductivity, and cell adhesion were conducted in order to evaluate in vitro biological responses. All scaffolds highly supported cell adhesion, MTT assay indicated better cell viability in 0.5% VD-loaded GO containing scaffold, and the scaffold enriched with 2% VD-loaded GO performed the most ALP activity. The results demonstrated the potential of these scaffolds to induce bone regeneration. Developing smart scaffolds with drug release capability is one of the main approaches to bone tissue engineering. The current study involves the fabrication of novel gelatin (G)-hydroxyapatite (HA)-/vitamin D (VD)-loaded graphene oxide (GO) scaffolds with different concentrations through solvent-casting method. Characterizations confirmed the successful synthesis of HA and GO, and VD was loaded in GO with 36.87 ± 4.87% encapsulation efficiency. Physicochemical characterizations showed that the scaffold containing 1% VD-loaded GO had the best mechanical properties and its porosity percentage and density was in the range of natural spongy bone. All scaffolds were degraded after 1-month, subjecting to phosphate buffer saline. The release profile of VD did not match any mathematical kinetics model, porosities and the degradation rate of the scaffolds were dominant controlling factors of release behavior. Studies on the bioactivity of scaffolds immersed in simulated body fluid indicated that VD and HA could encourage the formation of secondary apatite crystals in vitro. Buccal fat pad-derived stem cells (BFPSCs) were seeded on the scaffolds, MTT assay, alkaline phosphatase activity as an indicator of osteoconductivity, and cell adhesion were conducted in order to evaluate in vitro biological responses. All scaffolds highly supported cell adhesion, MTT assay indicated better cell viability in 0.5% VD-loaded GO containing scaffold, and the scaffold enriched with 2% VD-loaded GO performed the most ALP activity. The results demonstrated the potential of these scaffolds to induce bone regeneration.

Fabrication of chondroitin sulfate calcium complex and its chondrocyte proliferation in vitro

Chondroitin sulfate (CS)-calcium complex (CSCa) was fabricated, and the structural characteristics of CSCa and its proliferative bioactivity to the chondrocyte were investigated in vitro. Results suggested calcium ions could bind CS chains forming polysaccharide-metal complex, and the maximum calcium holding capacity of CSCa reached 4.23 %. Characterization of CSCa was performed by EDS, AFM, FTIR, UV, XRD and 1H-NMR. It was found that calcium ions were integrated with CS by binding the sulfate or carboxyl groups. The thermal properties analysis indicated CSCa had a good thermal stability by TGA and DSC. CSCa could interact the calcium-sensing receptor increasing the intracellular calcium ions and influence the cell cycle. The TGF-β1 secretion induced by CSCa could activate the TGF-β/Smads pathway and change the genes associated proliferation expression ultimately leading to the chondrocyte proliferation. This research probably has an important implication for understanding the effect of CSCa on bone care as food supplements.

Three-Dimensional Electrodeposition of Calcium Phosphates on Porous Nanofibrous Scaffolds and Their Controlled Release of Calcium for Bone Regeneration

To mimic the bone matrix of mineralized collagen and to impart microporous structure to facilitate cell migration and bone regeneration, we developed a nanofibrous (NF) polymer scaffold with highly interconnected pores and three-dimensional calcium phosphate coating utilizing an electrodeposition technique. The mineral content, morphology, crystal structure, and chemical composition could be tailored by adjusting the deposition temperature, voltage, and duration. A higher voltage and a higher temperature led to a greater rate of mineralization. Furthermore, nearly linear calcium releasing kinetics was achieved from the mineralized 3D scaffolds. The releasing rate was controlled by varying the initial electrodeposition conditions. A higher deposition voltage and temperature led to slower calcium release, which was associated with the highly crystalline and stoichiometric hydroxyapatite content. This premineralized NF scaffold enhanced bone regeneration over the control scaffold in a subcutaneous implantation model, which was associated with released calcium ions in facilitating osteogenic cell proliferation.

PHNQ from Evechinus chloroticus Sea Urchin Supplemented with Calcium Promotes Mineralization in Saos-2 Human Bone Cell Line

Polyhydroxylated naphthoquinones (PHNQs), known as spinochromes that can be extracted from sea urchins, are bioactive compounds reported to have medicinal properties and antioxidant activity. The MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability assay showed that pure echinochrome A exhibited a cytotoxic effect on Saos-2 cells in a dose-dependent manner within the test concentration range (15.625-65.5 µg/mL). The PHNQ extract from New Zealand sea urchin Evechinus chloroticus did not induce any cytotoxicity within the same concentration range after 21 days of incubation. Adding calcium chloride (CaCl2) with echinochrome A increased the number of viable cells, but when CaCl2 was added with the PHNQs, cell viability decreased. The effect of PHNQs extracted on mineralized nodule formation in Saos-2 cells was investigated using xylenol orange and von Kossa staining methods. Echinochrome A decreased the mineralized nodule formation significantly (p < 0.05), while nodule formation was not affected in the PHNQ treatment group. A significant (p < 0.05) increase in mineralization was observed in the presence of PHNQs (62.5 µg/mL) supplemented with 1.5 mM CaCl2. In conclusion, the results indicate that PHNQs have the potential to improve the formation of bone mineral phase in vitro, and future research in an animal model is warranted.

Progress in electrospun composite nanofibers: composition, performance and applications for tissue engineering

The discovery of novel methods to fabricate optimal scaffolds that mimic both mechanical and functional properties of the extracellular matrix (ECM) has always been the "holy grail" in tissue engineering. In recent years, electrospinning has emerged as an attractive material fabrication method and has been widely applied in tissue engineering due to its capability of producing non-woven and nanoscale fibers. However, from the perspective of biomimicry, it is difficult for single-component electrospun fiber membranes to achieve the biomimetic purposes of the multi-component extracellular matrix. Based on electrospinning, various functional components can be efficiently and expediently introduced into the membranes, and through the complementation and correlation of the properties of each component, composite materials with comprehensive and superior properties are obtained while maintaining the primitive merits of each component. In this review, we will provide an overview of the attempts made to fabricate electrospinning-based composite tissue engineering materials in the past few decades, which have been divided into organic additives, inorganic additives and organic-inorganic additives.

Microcalcifications, calcium-sensing receptor, and cancer

Calcium stones and calculi are observed in numerous human tissues. They are the result of deposition of calcium salts and are due to high local calcium concentrations. Prostatic calculi are usually classified as endogenous or extrinsic stones. Endogenous stones are commonly caused by obstruction of the prostatic ducts around an enlarged prostate resulting from benign prostatic hyperplasia or from chronic inflammation. The latter occurs mainly around the urethra and is generally caused by reflux of urine into the prostate. Calcium concentrations higher than in the plasma at sites of infection may induce the chemotactic response that eventually leads to recruitment of inflammatory cells. The calcium sensing receptor (CaSR) may be crucial for this recruitment as its expression and activity are increased by cytokines such as IL-6 and high extracellular calcium concentrations, respectively. The links between calcium calculi, inflammation, calcium supplementation, and CaSR functions in prostate cancer patients will be discussed in this review.

Overview of RAW264.7 for osteoclastogensis study: Phenotype and stimuli

Bone homeostasis is preserved by the balance of maintaining between the activity of osteogenesis and osteoclastogenesis. However, investigations for the osteoclastogenesis were hampered by considerable difficulties associated with isolating and culturing osteoclast in vivo. As the alternative, stimuli‐induced osteoclasts formation from RAW264.7 cells (RAW‐OCs) have gain its importance for extensively osteoclastogenic study of bone diseases, such as rheumatoid arthritis, osteoporosis, osteolysis and periodontitis. However, considering the RAW‐OCs have not yet been well‐characterized and RAW264.7 cells are polymorphic because of a diverse phenotype of the individual cells comprising this cell linage, and different fate associated with various stimuli contributions. Thus, in present study, we provide an overview for current knowledge of the phenotype of RAW264.7 cells, as well as the current understanding of the complicated interactions between various stimuli and RAW‐OCs in the light of the recent progress.

Strontium ranelate simultaneously improves the radiopacity and osteogenesis of calcium phosphate cement

In a minimally invasive surgery of osteoporotic fractures, high radiopacity is necessary to monitor the delivery and positioning of injectable cements and good osteogenesis is indispensable. In this work, strontium ranelate (SrR), an agent for treating osteoporosis, is firstly used as a radiopaque agent for calcium phosphate cement (CPC). The addition of SrR does not affect the hydration products of CPC, but prolonged the setting time and decreased the compressive strength. The injectability of the cement was higher than 85% when SrR content is more than 10 wt%. The radiopacity of CPC is significantly improved by SrR and higher than cortical bone when the content of SrR is more than 5 wt%. The concentration of Sr ions released from CPC is increased by the increasing content of SrR, which is among 17-1329 μM. Moreover, CPCs with SrR significantly promote the osteogenic differentiation of mouse bone marrow mesenchymal stem cells and inhibit the osteoclastogenic differentiation of RAW264.7 cells. Based on its good radiopacity and osteogenesis, suppressed osteoclastogenesis and appropriate physicochemical properties, the radiopaque CPC with more than 10 wt% SrR is prospective to be a promising biomaterial for osteoporotic fracture repairing in minimal invasive surgery.

Mineralization in micropores of calcium phosphate scaffolds

With the increasing demand for novel bone repair solutions that overcome the drawbacks of current grafting techniques, the design of artificial bone scaffolds is a central focus in bone regeneration research. Calcium phosphate scaffolds are interesting given their compositional similarity with bone mineral. The majority of studies focus on bone growth in the macropores (>100 µm) of implanted calcium phosphate scaffolds where bone structures such as osteons and trabeculae can form. However, a growing body of research shows that micropores (<50 µm) play an important role not only in improving bone growth in the macropores, but also in providing additional space for bone growth. Bone growth in the micropores of calcium phosphate scaffolds offers major mechanical advantages as it improves the mechanical properties of the otherwise brittle materials, further stabilizes the implant, improves load transfer, and generally enhances osteointegration. In this paper, we review evidence in the literature of bone growth into micropores, emphasizing on identification techniques and conditions under which bone components are observed in the micropores. We also review theories on mineralization and propose mechanisms, mediated by cells or not, by which mineralization may occur in the confined micropore space of calcium phosphate scaffolds. Understanding and validating these mechanisms will allow to better control and enhance mineralization in micropores to improve the design and efficiency of bone implants. STATEMENT OF SIGNIFICANCE: The design of synthetic bone scaffolds remains a major focus for engineering solutions to repair damaged and diseased bone. Most studies focus on the design of and growth in macropores (>100 µm), however research increasingly shows the importance of microporosity (<50 µm). Micropores provide an additional space for bone growth, which provides multiple mechanical advantages to the scaffold/bone composite. Here, we review evidence of bone growth into micropores in calcium phosphate scaffolds and conditions under which growth occurs in micropores, and we propose mechanisms that enable or facilitate growth in these pores. Understanding these mechanisms will allow researchers to exploit them and improve the design and efficiency of bone implants.

Selective Estrogen Receptor Modulator and prostimulatory effects of phytoestrogen β-ecdysone in Tinospora cordifolia on osteoblast cells

BACKGROUND

Indian ethnomedicine acclaims Tinosporacordifolia as a bone strengthening agent and prescribes it for the treatment of bone fractures, gout and other inflammatory diseases of the bone.

OBJECTIVE

(a) To understand the potential of T. cordifolia to act as a Selective Estrogen Receptor Modulator (SERM) on in vitro models. (b) To understand the toxic effects (if any) of T. cordifolia in vivo. (c) To understand the effects of β-ecdysone (proposed osteoprotective principle of T. cordifolia) on the growth of human osteoblast-like cells MG-63 and rat primary culture of osteoblasts. (d) To conduct phytochemical analysis on T. cordifolia extract to confirm the presence of β-ecdysone.

MATERIALS AND METHODS

The role of T. cordifolia as SERM was analyzed by investigating the effect of the extract on the growth of MCF-7 and HeLa cells. The effects of T. cordifolia in vivo was studied by biochemical (Liver function and renal function tests) and histopathological (Hematoxylin/Eosin staining) analysis. Phytochemical analysis of T.cordifolia was carried out by performing FT-IR and LC-ESI-MS analysis.

RESULTS

(a) T. cordifolia extract exerted non-estrogenic effects on MCF-7 and HeLa cells implicating its role as SERM. (b) High doses of T. cordifolia extract (750 and 1000 mg/kg body wt.) showed impairment of hepatic and renal function, induced pathological alterations in hepatic and renal architecture in albino rats. (c) β-ecdysone an ecdysteroid proposed as the osteoprotective principle of T. cordifolia exhibited significant prostimulatory effects on osteoblast cells and rat primary osteoblasts. (d) Phytochemical analysis confirmed the presence of β-ecdysone in alcoholic extract of T. cordifolia extract substantiating its role as the osteoprotective principle of T. cordifolia.

CONCLUSION

(a) T. cordifolia could function as SERM and can have applications in the therapy of osteoporosis. (b) β-ecdysone is the osteoprotective principle of T. cordifolia.

Compositional and histological comparison of carbonate apatite fabricated by dissolution-precipitation reaction and Bio-Oss®

Carbonate apatite (CO₃Ap) is an inorganic component of bone. This study aimed to compare the composition and tissue response to of CO₃Ap (CO₃Ap-DP) fabricated by the dissolution-precipitation reaction using calcite as a precursor and Bio-Oss®, which is widely used in orthopedic and dental fields as a synthetic bone substitute. X-ray diffraction and Fourier transform infrared results showed that CO₃Ap-DP and Bio-Oss® were both B-type carbonate apatite with low crystallinity. The average sizes of CO₃Ap-DP and Bio-Oss® granules were 450 ± 58 and 667 ± 168μ m, respectively, and their carbonate contents were 12.1 ± 0.6 and 5.6 ± 0.1 wt%, respectively. CO₃Ap-DP had a larger amount of CO₃ than Bio-Oss® but higher crystallinity than Bio-Oss®. When a bone defect made at the femur of rabbits was reconstructed with CO₃Ap-DP and Bio-Oss®, CO₃Ap-DP granules were partially replaced with bone, whereas Bio-Oss® remained at 8 weeks after implantation. CO₃Ap-DP granules elicited a significantly larger amount of new bone formation at the cortical bone portion than Bio-Oss® at 4 weeks after the implantation. The results obtained in the present study demonstrated that CO₃Ap-DP and Bio-Oss® showed different behavior even though they were both classified as CO₃Ap. The CO₃ content in CO₃Ap played a more important role than the crystallinity of CO₃Ap for replacement to bone and high osteoconductivity.

The effect of Mg-Ca-Sr alloy degradation products on human mesenchymal stem cells

Biodegradable Mg alloys have the potential to replace currently used metallic medical implant devices, likely eliminating toxicity concerns and the need for secondary surgeries, while also providing a potentially stimulating environment for tissue growth. A recently developed Mg-Ca-Sr alloy possesses advantageous characteristics over other Mg alloys, having a good combination of strength and degradation behavior, while also displaying potentially osteogenic properties. To better understand the effect of alloy degradation products on cellular mechanisms, in vitro studies using human bone marrow-derived mesenchymal stem cells were conducted. Ionic products of alloy dissolution were found to be nontoxic but changed the proliferation profile of stem cells. Furthermore, their presence changed the progress of osteogenic development, while concentrations of Mg in particular appeared to induce stem cell differentiation. The work presented herein provides a foundation for future alloy design where structures can be tailored to obtain specific implant performance. These potentially bioactive implants would reduce the risks for patients by shortening their healing time, minimizing discomfort and toxicity concerns, while reducing hospital costs. © 2017 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 697-704, 2018.

Dose effects of beta-tricalcium phosphate nanoparticles on biocompatibility and bone conductive ability of three-dimensional collagen scaffolds

Three-dimensional collagen scaffolds coated with beta-tricalcium phosphate (β-TCP) nanoparticles reportedly exhibit good bioactivity and biodegradability. Dose effects of β-TCP nanoparticles on biocompatibility and bone forming ability were then examined. Collagen scaffold was applied with 1, 5, 10, and 25 wt% β-TCP nanoparticle dispersion and designated TCP1, TCP5, TCP10, and TCP25, respectively. Compressive strength, calcium ion release and enzyme resistance of scaffolds with β-TCP nanoparticles applied increased with β-TCP dose. TCP5 showed excellent cell-ingrowth behavior in rat subcutaneous tissue. When TCP10 was applied, osteoblastic cell proliferation and rat cranial bone augmentation were greater than for any other scaffold. The bone area of TCP10 was 7.7-fold greater than that of non-treated scaffold. In contrast, TCP25 consistently exhibited adverse biological effects. These results suggest that the application dose of β-TCP nanoparticles affects the scaffold bioproperties; consequently, the bone conductive ability of TCP10 was remarkable.

Osteogenic differentiation capacity of human mesenchymal stromal cells in response to extracellular calcium with special regard to connexin 43

The effects of extracellular calcium on osteogenic differentiation capacity of human bone-derived mesenchymal stromal cells with special regard to connexin 43 (cx43) have been investigated by means of cell culture experiments. Mesenchymal stromal cells isolated from human cancellous bone were cultured on tissue culture plates at different calcium ion (Ca²⁺) concentrations (1.8mmoll^-1, 10mmoll^-1, 20mmoll^-1). Cell responses were evaluated by quantitative RT-PCR, immunofluorescence staining, and Lucifer Yellow fluorescence uptake experiments. It could be shown that increasing Ca²⁺ concentrations correlate with increasing cx43 and bone sialoprotein mRNA levels as well as with enhanced cx43 fluorescence signaling and matrix mineralization of the cultures as shown by von Kossa staining. Hemichannel gating - assessed by Lucifer Yellow uptake - increases with increasing extracellular Ca²⁺ concentrations suggesting that regulatory effects at the hemichannel level are calcium-dependent.

Involvement of 3D osteoblast migration and bone apatite during in vitro early osteocytogenesis

The transition from osteoblast to osteocyte is described to occur through passive entrapment mechanism (self-buried, or embedded by neighboring cells). Here, we provide evidence of a new pathway where osteoblasts are "more" active than generally assumed. We demonstrate that osteoblasts possess the ability to migrate and differentiate into early osteocytes inside dense collagen matrices. This step involves MMP-13 simultaneously with IBSP and DMP1 expression. We also show that osteoblast migration is enhanced by the presence of apatite bone mineral. To reach this conclusion, we used an in vitro hybrid model based on both the structural characteristics of the osteoid tissue (including its density, texture and three-dimensional order), and the use of bone-like apatite. This finding highlights the mutual dynamic influence of osteoblast cell and bone extra cellular matrix. Such interactivity extends the role of physicochemical effects in bone morphogenesis complementing the widely studied molecular signals. This result represents a conceptual advancement in the fundamental understanding of bone formation.

The Calcium-Sensing Receptor and Integrins in Cellular Differentiation and Migration

The calcium-sensing receptor (CaSR) is a widely expressed homodimeric G-protein coupled receptor structurally related to the metabotropic glutamate receptors and GPRC6A. In addition to its well characterized role in maintaining calcium homeostasis and regulating parathyroid hormone release, evidence has accumulated linking the CaSR with cellular differentiation and migration, brain development, stem cell engraftment, wound healing, and tumor growth and metastasis. Elevated expression of the CaSR in aggressive metastatic tumors has been suggested as a potential novel prognostic marker for predicting metastasis, especially to bone tissue where extracellular calcium concentrations may be sufficiently high to activate the receptor. Recent evidence supports a model whereby CaSR-mediated activation of integrins promotes cellular migration. Integrins are single transmembrane spanning heterodimeric adhesion receptors that mediate cell migration by binding to extracellular matrix proteins. The CaSR has been shown to form signaling complexes with the integrins to facilitate both the movement and differentiation of cells, such as neurons during normal brain development and tumor cells under pathological circumstances. Thus, CaSR/integrin complexes may function as a universal cell migration or homing complex. Manipulation of this complex may be of potential interest for treating metastatic cancers, and for developmental disorders pertaining to aberrant neuronal migration.

Graphene oxide scaffold accelerates cellular proliferative response and alveolar bone healing of tooth extraction socket

Graphene oxide (GO) consisting of a carbon monolayer has been widely investigated for tissue engineering platforms because of its unique properties. For this study, we fabricated a GO-applied scaffold and assessed the cellular and tissue behaviors in the scaffold. A preclinical test was conducted to ascertain whether the GO scaffold promoted bone induction in dog tooth extraction sockets. For this study, GO scaffolds were prepared by coating the surface of a collagen sponge scaffold with 0.1 and 1 µg/mL GO dispersion. Scaffolds were characterized using scanning electron microscopy (SEM), physical testing, cell seeding, and rat subcutaneous implant testing. Then a GO scaffold was implanted into a dog tooth extraction socket. Histological observations were made at 2 weeks postsurgery. SEM observations show that GO attached to the surface of collagen scaffold struts. The GO scaffold exhibited an interconnected structure resembling that of control subjects. GO application improved the physical strength, enzyme resistance, and adsorption of calcium and proteins. Cytocompatibility tests showed that GO application significantly increased osteoblastic MC3T3-E1 cell proliferation. In addition, an assessment of rat subcutaneous tissue response revealed that implantation of 1 µg/mL GO scaffold stimulated cellular ingrowth behavior, suggesting that the GO scaffold exhibited good biocompatibility. The tissue ingrowth area and DNA contents of 1 µg/mL GO scaffold were, respectively, approximately 2.5-fold and 1.4-fold greater than those of the control. Particularly, the infiltration of ED2-positive (M2) macrophages and blood vessels were prominent in the GO scaffold. Dog bone-formation tests showed that 1 µg/mL GO scaffold implantation enhanced bone formation. New bone formation following GO scaffold implantation was enhanced fivefold compared to that in control subjects. These results suggest that GO was biocompatible and had high bone-formation capability for the scaffold. The GO scaffold is expected to be beneficial for bone tissue engineering therapy.

Activation of intracellular calcium signaling in osteoblasts colocalizes with the formation of post-yield diffuse microdamage in bone matrix

Previous studies demonstrated that extracellular calcium efflux ([Ca(2+)]E) originates from the regions of bone extracellular matrix that are undergoing microdamage. Such [Ca(2+)]E is reported to induce the activation of intracellular calcium signaling ([Ca(2+)]I) in MC3T3-E1 cells. The current study investigated the association between microdamage and local activation of intracellular calcium signaling quantifiably in MC3T3-E1 cells. Cells were seeded on devitalized notched bovine bone samples to induce damage controllably within the field of observation. A sequential staining procedure was implemented to stain for intracellular calcium activation followed by staining for microdamage on the same sample. The increase in [Ca(2+)]I fluorescence in cells of mechanically loaded samples was greater than that of unloaded negative control cells. The results showed that more than 80% of the cells with increased [Ca(2+)]I fluorescence were located within the damage zone. In conclusion, the findings demonstrate that there are spatial proximity between diffuse microdamage induction and the activation of intracellular calcium ([Ca(2+)]I) signaling in MC3T3-E1 cells. The downstream responses to the observed activation in future research may help understand how bone cells repair microdamage.

Gelatine modified monetite as a bone substitute material: An in vitro assessment of bone biocompatibility

Calcium phosphate phases are increasingly used for bone tissue substitution, and the load bearing properties of these inherently brittle biomaterials are increased by inclusion of organic components. Monetite prepared using mineralization of gelatine pre-structured through phosphate leads to a significantly increased biaxial strength and indirect tensile strength compared to gelatine-free monetite. Besides the mechanical properties, degradation in physiological solutions and osteoblast and osteoclast cell response were investigated. Human bone marrow stromal cells (hBMSCs) showed considerably higher proliferation rates on the gelatine modified monetite than on polystyrene reference material in calcium-free as well as standard cell culture medium (α-MEM). Osteogenic differentiation on the material was comparable to polystyrene in both medium types. Osteoclast-like cells derived from monocytes were able to actively resorb the biomaterial. Osteoblastic differentiation and perhaps even more important the cellular resorption of the biomaterial indicate that it can be actively involved in the bone remodeling process. Thus the behavior of osteoblasts and osteoclasts as well as the adequate degradation and mechanical properties are strong indicators for bone biocompatibility, although in vivo studies are still required to prove this.

STATEMENT OF SIGNIFICANCE

New and unique? A low temperature precipitationprocessforcalcium anhydrous hydrogen phosphateallows for the first time to produce monolithic compact composites of monetite and gelatine. The composite is degradable and resorbable. To prove that, the question arises: what is bone biocompatibility? The reaction of both mayor cell types of bone represents this biocompatibility. Therefore, human bone marrow stromal cells were seeded revealing the materials pro-osteogenic properties. Monocyte cultivation, becoming recently focus of interest, revealed the capability of the biomaterial to be actively resorbed by derived osteoclast-like cells. Not new but necessary ismechanical characterization, which is often only investigated as uniaxial property. Here, a biaxial method is applied, to characterize the materials properties closer to its application loads.

Calcium Sensing Receptor Function Supports Osteoblast Survival and Acts as a Co-Factor in PTH Anabolic Actions in Bone

Anabolic actions of PTH in bone involve increased deposition of mineralizing matrix. Regulatory feedback of the process may be important to maintain calcium homeostasis and, in turn, calcium may inform the process. This investigation clarified the role of calcium availability and the calcium sensing receptor (CaSR) in the anabolic actions of PTH. CaSR function promoted osteoblastic cell numbers, with lower cell numbers in post-confluent cultures of primary calvarial cells from Col1-CaSR knock-out (KO) mice, and for calvarial cells from wild-type (WT) mice treated with a calcilytic. Increased apoptosis of calvarial cells with calcilytic treatment suggested CaSR is critical for protection against stage-dependent cell death. Whole and cortical, but not trabecular, bone parameters were significantly lower in Col1-CaSR KO mice versus WT littermates. Intact Col1-CaSR KO mice had lower serum P1NP levels relative to WT. PTH treatment displayed anabolic actions in WT and, to a lesser degree, KO mice, and rescued the lower P1NP levels in KO mice. Furthermore, PTH effects on whole tibiae were inhibited by osteoblast-specific CaSR ablation. Vertebral body implants (vossicles) from untreated Col1-CaSR KO and WT mice had similar bone volumes after 4 weeks of implantation in athymic mice. These findings suggest that trabecular bone formation can occur independently of the CaSR, and that the CaSR plays a collaborative role in the PTH anabolic effects on bone. J. Cell. Biochem. 117: 1556-1567, 2016. © 2015 Wiley Periodicals, Inc.

Microdamage induced calcium efflux from bone matrix activates intracellular calcium signaling in osteoblasts via L-type and T-type voltage-gated calcium channels

Mechanisms by which bone microdamage triggers repair response are not completely understood. It has been shown that calcium efflux ([Ca(2+)]E) occurs from regions of bone undergoing microdamage. Such efflux has also been shown to trigger intracellular calcium signaling ([Ca(2+)]I) in MC3T3-E1 cells local to damaged regions. Voltage-gated calcium channels (VGCCs) are implicated in the entry of [Ca(2+)]E to the cytoplasm. We investigated the involvement of VGCC in the extracellular calcium induced intracellular calcium response (ECIICR). MC3T3-E1 cells were subjected to one dimensional calcium efflux from their basal aspect which results in an increase in [Ca(2+)]I. This increase was concomitant with membrane depolarization and it was significantly reduced in the presence of Bepridil, a non-selective VGCC inhibitor. To identify specific type(s) of VGCC in ECIICR, the cells were treated with selective inhibitors for different types of VGCC. Significant changes in the peak intensity and the number of [Ca(2+)]I oscillations were observed when L-type and T-type specific VGCC inhibitors (Verapamil and NNC55-0396, respectively) were used. So as to confirm the involvement of L- and T-type VGCC in the context of microdamage, cells were seeded on devitalized notched bone specimen, which were loaded to induce microdamage in the presence and absence of Verapamil and NNC55-0396. The results showed significant decrease in [Ca(2+)]I activity of cells in the microdamaged regions of bone when L- and T-type blockers were applied. This study demonstrated that extracellular calcium increase in association with damage depolarizes the cell membrane and the calcium ions enter the cell cytoplasm by L- and T-type VGCCs.

Enhanced biocompatibility of PLGA nanofibers with gelatin/nano-hydroxyapatite bone biomimetics incorporation

The biocompatibility of biomaterials is essentially for its application. The aim of current study was to evaluate the biocompatibility of poly(lactic-co-glycolic acid) (PLGA)/gelatin/nanohydroxyapatite (n-HA) (PGH) nanofibers systemically to provide further rationales for the application of the composite electrospun fibers as a favorable platform for bone tissue engineering. The PGH composite scaffold with diameter ranging from nano- to micrometers was fabricated by using electrospinning technique. Subsequently, we utilized confocal laser scanning microscopy (CLSM) and MTT assay to evaluate its cyto-compatibility in vitro. Besides, real-time quantitative polymerase chain reaction (qPCR) analysis and alizarin red staining (ARS) were performed to assess the osteoinductive activity. To further test in vivo, we implanted either PLGA or PGH composite scaffold in a rat subcutaneous model. The results demonstrated that PGH scaffold could better support osteoblasts adhesion, spreading, and proliferation and show better cyto-compatibility than pure PLGA scaffold. Besides, qPCR analysis and ARS showed that PGH composite scaffold exhibited higher osteoinductive activity owing to higher phenotypic expression of typical osteogenic genes and calcium deposition. The histology evaluation indicated that the incorporation of Gelatin/nanohydroxyapatite (GH) biomimetics could significantly reduce local inflammation. Our data indicated that PGH composite electrospun nanofibers possessed excellent cyto-compatibility, good osteogenic activity, as well as good performance of host tissue response, which could be versatile biocompatible scaffolds for bone tissue engineering.

Role of the calcium-sensing receptor in extracellular calcium homeostasis

Maintaining a constant level of blood Ca(2+) is essential because of calcium's myriad intracellular and extracellular roles. The CaSR plays key roles in maintaining [Formula: see text] homeostasis by detecting small changes in blood Ca(2+) and modulating the production/secretion of the Ca(2+)-regulating hormones, PTH, CT, FGF23 and 1,25(OH)2D3, so as to appropriately regulate Ca(2+) transport into or out of blood via kidney, intestine, and/or bone. When Ca(2+) is high, the CaSR suppresses PTH synthesis and secretion, promotes its degradation, and inhibits parathyroid cellular proliferation. It has just the opposite effects on the C-cell, stimulating CT when [Formula: see text] is high. In bone, Ca(2+), acting via the CaSR, stimulates recruitment and proliferation of preosteoblasts, their differentiation to mature osteoblasts, and synthesis and mineralization of bone proteins. Conversely, [Formula: see text] inhibits the formation and activity and promotes apoptosis of osteoclasts, likely via the CaSR. These actions tend to mobilize skeletal Ca(2+) during [Formula: see text] deficiency and retain it when Ca(2+) is plentiful.

How smart do biomaterials need to be? A translational science and clinical point of view

Over the last 4 decades innovations in biomaterials and medical technology have had a sustainable impact on the development of biopolymers, titanium/stainless steel and ceramics utilized in medical devices and implants. This progress was primarily driven by issues of biocompatibility and demands for enhanced mechanical performance of permanent and non-permanent implants as well as medical devices and artificial organs. In the 21st century, the biomaterials community aims to develop advanced medical devices and implants, to establish techniques to meet these requirements, and to facilitate the treatment of older as well as younger patient cohorts. The major advances in the last 10 years from a cellular and molecular knowledge point of view provided the scientific foundation for the development of third-generation biomaterials. With the introduction of new concepts in molecular biology in the 2000s and specifically advances in genomics and proteomics, a differentiated understanding of biocompatibility slowly evolved. These cell biological discoveries significantly affected the way of biomaterials design and use. At the same time both clinical demands and patient expectations continued to grow. Therefore, the development of cutting-edge treatment strategies that alleviate or at least delay the need of implants could open up new vistas. This represents the main challenge for the biomaterials community in the 21st century. As a result, the present decade has seen the emergence of the fourth generation of biomaterials, the so-called smart or biomimetic materials. A key challenge in designing smart biomaterials is to capture the degree of complexity needed to mimic the extracellular matrix (ECM) of natural tissue. We are still a long way from recreating the molecular architecture of the ECM one to one and the dynamic mechanisms by which information is revealed in the ECM proteins in response to challenges within the host environment. This special issue on smart biomaterials lists a large number of excellent review articles which core is to present and discuss the basic sciences on the topic of smart biomaterials. On the other hand, the purpose of our review is to assess state of the art and future perspectives of the so called "smart biomaterials" from a translational science and specifically clinical point of view. Our aim is to filter out and discuss which biomedical advances and innovations help us to achieve the objective to translate smart biomaterials from bench to bedside. The authors predict that analyzing the field of smart biomaterials from a clinical point of view, looking back 50 years from now, it will show that this is our heritage in the 21st century.

Expression of the calcium sensing receptor in human peripheral blood T lymphocyte and its contribution to cytokine secretion through MAPKs or NF-κB pathways

The calcium-sensing receptor (CaSR) has been reported to play an important role in many tissues and organs. However, studies about the expression and function of CaSR in T lymphocytes are still not very lucid. In this study, we investigated the above-mentioned issues using RT-PCR, immunofluorescence staining, Western blotting, and the ELISA techniques. We found that the CaSR protein was expressed, and mainly located in the membrane in the normal human peripheral blood T lymphocytes. GdCl(3) (an agonist of CaSR) increased the dose-dependency of the CaSR expression, which was abolished by NPS2390 (an inhibitor of CaSR). GdCl(3) and Ca(2+) increased the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 (one subgroup of MAPKs) and P65 (subunit of NF-κB),but, they had no significant effects on the JNK and P38 subgroups of MAPKs. Meantime, GdCl(3) and Ca(2+) stimulated both the IL-6 and TNF-β releases and their mRNA expressions. However, these effects of GdCl(3) and Ca(2+) were inhibited by NPS2390, U0126 (MAPKs pathway inhibitor) or Bay-11-7082 (NF-κB pathway inhibitor). These results suggested that CaSR was functionally expressed in the T cells, and the activated CaSR contributed to the cytokine secretion through the partial MAPK and NF-κB pathways.

Preparation and characterization of collagen-nanohydroxyapatite biocomposite scaffolds by cryogelation method for bone tissue engineering applications

Recent efforts of bone repair focus on development of porous scaffolds for cell adhesion and proliferation. Collagen-nanohydroxyapatite (HA) scaffolds (70:30; 50:50; and 30:70 mass percentage) were produced by cryogelation technique using 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide as crosslinking agents. A pure collagen scaffold was used as control. Morphology analysis revealed that all cryogels had highly porous structure with interconnective porosity and the nanoHA aggregates were randomly dispersed throughout the scaffold structure. Chemical analysis showed the presence of all major peaks related to collagen and HA in the biocomposites and indicated possible interaction between nanoHA aggregates and collagen molecules. Porosity analysis revealed an enhancement in the surface area as the nanoHA percentage increased in the collagen structure. The biocomposites showed improved mechanical properties as the nanoHA content increased in the scaffold. As expected, the swelling capacity decreased with the increase of nanoHA content. In vitro studies with osteoblasts cells showed that they were able to attach and spread in all cryogels surfaces. The presence of collagen-nanoHA biocomposites resulted in higher overall cellular proliferation compared to pure collagen scaffold. A statistically significant difference between collagen and collagen-nanoHA cryogels was observed after 21 day of cell culture. These innovative collagen-nanoHA cryogels could have potentially appealing application as scaffolds for bone regeneration.

Extracellular calcium chronically induced human osteoblasts effects: specific modulation of osteocalcin and collagen type XV

Fluctuation in extracellular calcium (Ca(2+)) concentration occurs during bone remodeling. Free ionized Ca(2+) plays a critical role in regulating osteoblast functions. We analyzed the effects of different concentrations of free ionized Ca(2+) (0.5, 1.3, and 2.6 mM) on human osteoblasts and we evaluated osteoblastic phenotype (marker expression and cell morphology) and functions (osteogenic differentiation, cell proliferation, and cell signaling). Our data show human osteoblasts that chronically stimulated with 0.5, 1.3, or 2.6 mM Ca(2+) significantly increase intracellular content of alkaline phosphatase, collagen type I, osteocalcin, and bone sialoprotein, whereas collagen type XV was down-modulated and RUNX2 expression was not affected. We also found a Ca(2+) concentration-dependent increase in osteogenic differentiation and cell proliferation, associated to an increase of signaling protein PLCβ1 and p-ERK. Human osteoblast morphology was affected by Ca(2+) as seen by the presence of numerous nucleoli, cells in mitosis, cell junctions, and an increased number of vacuoles. In conclusion, our data show a clear phenotypical and functional effect of extracellular Ca(2+) on human osteoblasts and support the hypothesis of a direct role of this cation in the bone remodeling processes.

Calcium ions promote osteogenic differentiation and mineralization of human dental pulp cells: implications for pulp capping materials

Calcium (Ca) is the main element of most pulp capping materials and plays an essential role in mineralization. Different pulp capping materials can release various concentrations of Ca ions leading to different clinical outcomes. The purpose of this study was to investigate the effects of various concentrations of Ca ions on the growth and osteogenic differentiation of human dental pulp cells (hDPCs). Different concentrations of Ca ions were added to growth culture medium and osteogenic inductive culture medium. A Cell Counting Kit-8 was used to determine the proliferation of hDPCs in growth culture medium. Osteogenic differentiation and mineralization were measured by alkaline phosphatase (ALP) assay, Alizarin red S/von kossa staining, Ca content quantitative assay. The selected osteogenic differentiation markers were investigated by quantitative real-time polymerase chain reaction (qRT-PCR). Within the range of 1.8-16.2 mM, increased concentrations of Ca ions had no effect on cell proliferation, but led to changes in osteogenic differentiation. It was noted that enhanced mineralized matrix nodule formation was found in higher Ca ions concentrations; however, ALP activity and gene expression were reduced. qRT-PCR results showed a trend towards down-regulated mRNA expression of type I collagen and Runx2 at elevated concentrations of Ca ions, whereas osteopontin and osteocalcin mRNA expression were significantly up-regulated. Ca ions content in the culture media can significantly influence the osteogenic properties of hDPCs, indicating the importance of optimizing Ca ions release from dental pulp capping materials in order to achieve desirable clinical outcomes.

Effects of varied ionic calcium and phosphate on the proliferation, osteogenic differentiation and mineralization of human periodontal ligament cells in vitro

BACKGROUND AND OBJECTIVE

A number of bone-filling materials containing calcium (Ca(2+) ) and phosphate (P) ions have been used in the repair of periodontal bone defects; however, the effects that local release of Ca(2+) and P ions has on biological reactions are not fully understood. In this study, we investigated the effects of various levels of Ca(2+) and P ions on the proliferation, osteogenic differentiation and mineralization of human periodontal ligament cells (hPDLCs).

MATERIAL AND METHODS

The hPDLCs were obtained using an explant culture method. Defined concentrations and ratios of ionic Ca(2+) to inorganic P were added to standard culture and osteogenic induction media. The ability of hPDLCs to proliferate in these growth media was assayed using the Cell Counting Kit-8. Cell apoptosis was evaluated by the fluorescein isothiocyanate-annexin V/propidium iodide double-staining method. Osteogenic differentiation and mineralization were investigated by morphological observations, alkaline phosphatase activity and Alizarin Red S/von Kossa staining. The mRNA expression of osteogenic related markers was analysed using RT-PCR.

RESULTS

Within the ranges of Ca(2+) and P ion concentrations tested, we observed that increased concentrations of Ca(2+) and P ions enhanced cell proliferation and formation of mineralized matrix nodules, whereas alkaline phosphatase activity was reduced. The RT-PCR results showed that elevated concentrations of Ca(2+) and P ions led to a general increase of Runx2 mRNA expression and decreased alkaline phosphatase mRNA expression, but gave no clear trend on osteocalcin mRNA levels.

CONCLUSION

The concentrations and ratios of Ca(2+) and P ions could significantly influence proliferation, differentiation and mineralization of hPDLCs. Within the range of concentrations tested, we found that the combination of 9.0 mm Ca(2+) ions and 4.5 mm P ions were the optimal concentrations for proliferation, differentiation and mineralization in hPDLCs.

Ca2+ chemotaxis in Dictyostelium discoideum

Using a newly developed microfluidic chamber, we have demonstrated in vitro that Ca(2+) functions as a chemoattractant of aggregation-competent Dictyostelium discoideum amoebae, that parallel spatial gradients of cAMP and Ca(2+) are more effective than either alone, and that cAMP functions as a stronger chemoattractant than Ca(2+). Effective Ca(2+) gradients are extremely steep compared with effective cAMP gradients. This presents a paradox because there is no indication to date that steep Ca(2+) gradients are generated in aggregation territories. However, given that Ca(2+) chemotaxis is co-acquired with cAMP chemotaxis during development, we speculate on the role that Ca(2+) chemotaxis might have and the possibility that steep, transient Ca(2+) gradients are generated during natural aggregation in the interstitial regions between cells.

Use of bovine hydroxyapatite with or without biomembrane in sinus lift in rabbits: histopathologic analysis and immune expression of core binding factor 1 and vascular endothelium growth factor

PURPOSE

Considering the clinical discussion on the necessity of using a barrier membrane in the osteotomy area of sinus lift procedures to prevent fibrous tissue formation in this area and as a physical limit, the aim of this study was to analyze and compare the use of bovine hydroxyapatite (HA) with and without a biologic membrane by histopathologic analysis and immune expression of core binding factor 1 and vascular endothelium growth factor in the sinus lift in rabbits.

MATERIALS AND METHODS

Sixteen male rabbits underwent bilateral sinus lift procedures and were divided into 2 groups according to the sinus filling material: group 1 received bovine HA (Bio-Oss; Geistlich Pharma AG, Wohlhusen, Switzerland) and group 2 received bovine HA and a nonporous polytetrafluorethylene membrane. All groups were sacrificed after 7, 14, 30, and 60 days for microscopic, histomorphometric, and immunohistochemical analyses.

RESULTS

Microscopic analysis showed a similar bone repair pattern between the tested groups. New bone formation, soft tissue, and the remaining material were analyzed by histomorphometric analysis. No statistically significant differences (P > .05) were detected between groups for all periods analyzed. In addition, no remarkable differences were noticed in core binding factor 1 or vascular endothelium growth factor immune expression.

CONCLUSION

Taken together, these results show that using a biologic membrane does not improve bone repair induced by bovine HA, as shown by histopathologic and immunohistochemical analyses.