Developmental expression of osteopontin (OPN) mRNA in rat tissues: evidence for a role for OPN in bone formation and resorption

Ionic release from bioactive SiO2-CaOCME/poly(tetrahydrofuran)/poly(caprolactone) hybrids drives human-bone marrow stromal cell osteogenic differentiation

This study demonstrates that dissolution products of inorganic/organic SiO2-CaOCME/PTHF/PCL-diCOOH hybrid (70S30CCME-CL) drive human bone marrow stromal cells (h-BMSCs) down an osteogenic pathway with the production of mineralised matrix. We investigated osteogenesis through combined analyses of mRNA dynamics for key markers and targeted staining of mineralised matrix. We demonstrate that h-BMSCs undergo accelerated differentiation in vitro in response to the 70S30CCME-CL ionic milieu, as compared to incubation with osteogenic media. Extracts from 70S30CCME-CL promote osteogenesis by inducing changes in cellular metabolic activity, promoting changes in cell morphology consistent with the osteogenic lineage, and by enhancing mineralisation of hydroxyapatite in the extracellular matrix. Additionally, our results show that 70S30CCME-CL hybrids prove sustained functional resilience by maintaining osteostimulatory effects despite cumulated dissolution cycles. In co-differentiation medium, 70S30CCME-CL ionic release can modulate signalling pathways associated with non-osteogenic functions, further supporting their potential for bone regeneration applications. Overall, our study provides compelling experimental evidence that the 70S30CCME-CL hybrid is a promising biomaterial for bone tissue regeneration applications.

NOX4 and its association with myeloperoxidase and osteopontin in regulating endochondral ossification

IMPORTANCE

Endochondral ossification plays an important role in skeletal development. Recent studies have suggested a link between increased intracellular reactive oxygen species (ROS) and skeletal disorders. Moreover, previous studies have revealed that increasing the levels of myeloperoxidase (MPO) and osteopontin (OPN) while inhibiting NADPH oxidase 4 (NOX4) can enhance bone growth. This investigation provides further evidence by showing a direct link between NOX4 and MPO, OPN in bone function.

OBJECTIVE

This study investigates NOX4, an enzyme producing hydrogen peroxide, in endochondral ossification and bone remodeling. NOX4's role in osteoblast formation and osteogenic signaling pathways is explored.

METHODS

Using NOX4-deficient (NOX4-/-) and ovariectomized (OVX) mice, we identify NOX4's potential mediators in bone maturation.

RESULTS

NOX4-/- mice displayed significant differences in bone mass and structure. Compared to the normal Control and OVX groups. Hematoxylin and eosin staining showed NOX4-/- mice had the highest trabecular bone volume, while OVX had the lowest. Proteomic analysis revealed significantly elevated MPO and OPN levels in bone marrow-derived cells in NOX4-/- mice. Immunohistochemistry confirmed increased MPO, OPN, and collagen II (COLII) near the epiphyseal plate. Collagen and chondrogenesis analysis supported enhanced bone development in NOX4-/- mice.

CONCLUSIONS AND RELEVANCE

Our results emphasize NOX4's significance in bone morphology, mesenchymal stem cell proteomics, immunohistochemistry, collagen levels, and chondrogenesis. NOX4 deficiency enhances bone development and endochondral ossification, potentially through increased MPO, OPN, and COLII expression. These findings suggest therapeutic implications for skeletal disorders.

Physico-biological and in vivo evaluation of irisin loaded 45S5 porous bioglass granules for bone regeneration

In this study, we investigated the physico-biological and in-vivo evaluation of irisin loaded 45S5 bioglass bone graft for enhancing osteoblastic differentiation and bone regeneration in rat femur head defect model. Highly porous structure was obtained in the bioglass by burn-out process with varying the concentration of poly (methyl methacrylate) (PMMA) spheres. 10 % polyvinyl alcohol (PVA) was used as a binder for the sustain releasing of irisin on porous bioglass. Different concentrations of irisin were loaded on the selected bioglass samples and these were further evaluated for the biocompatibility and osteoblastic differentiation properties. The in vitro results demonstrated not only its biocompatibility but also that it stimulated pre-osteoblast differentiation. The in vivo data showed new bone formation as well as expression of osteogenic proteins like alkaline phosphatase (ALP), Runt-related transcription factor 2 (Runx-2), osteopontin (OPN), and collagen-1 (Col-1). Our results support the use of irisin loaded bioglass for the use of early bone regeneration.

Targeted biomarkers of progression in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is an increasingly significant health issue worldwide. Early stages of CKD can be asymptomatic and disease trajectory difficult to predict. Not everyone with CKD progresses to kidney failure, where kidney replacement therapy is the only life-sustaining therapy. Predicting which patients will progress to kidney failure would allow better use of targeted treatments and more effective allocation of health resources. Current diagnostic tests to identify patients with progressive disease perform poorly but there is a suite of new and emerging predictive biomarkers with great clinical promise.

METHODS

This narrative review describes new and emerging biomarkers of pathophysiologic processes of CKD development and progression, accessible in blood or urine liquid biopsies. Biomarkers were selected based on their reported pathobiological functions in kidney injury, inflammation, oxidative stress, repair and fibrosis. Biomarker function and evidence of involvement in CKD development and progression are reported.

CONCLUSION

Many biomarkers reviewed here have received little attention to date, perhaps because of conflicting conclusions of their utility in CKD. The functional roles of the selected biomarkers in the underlying pathobiology of progression of CKD are a powerful rationale for advancing and validating these molecules as prognosticators and predictors of CKD trajectory.

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

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

Coaxially Fabricated Dual-Drug Loading Electrospinning Fibrous Mat with Programmed Releasing Behavior to Boost Vascularized Bone Regeneration

In clinical treatment, the bone regeneration of critical-size defects is desiderated to be solved, and the regeneration of large bone segment defects depends on early vascularization. Therefore, overcoming insufficient vascularization in artificial bone grafts may be a promising strategy for critical-size bone regeneration. Herein, a novel dual-drug programmed releasing electrospinning fibrous mat (EFM) with a deferoxamine (DFO)-loaded shell layer and a dexamethasone (DEX)-loaded core layer is fabricated using coaxial electrospinning technology, considering the temporal sequence of vascularization and bone repair. DFO acts as an angiogenesis promoter and DEX is used as an osteogenesis inducer. The results demonstrate that the early and rapid release of DFO promotes angiogenesis in human umbilical vascular endothelial cells and the sustained release of DEX enhances the osteogenic differentiation of rat bone mesenchymal stem cells. DFO and DEX exert synergetic effects on osteogenic differentiation via the Wnt/β-catenin signaling pathway, and the dual-drug programmed releasing EFM acquired perfect vascularized bone regeneration ability in a rat calvarial defect model. Overall, the study suggests a low-cost strategy to enhance vascularized bone regeneration by adjusting the behavior of angiogenesis and osteogenesis in time dimension.

Cellular plasticity in bone metastasis

Metastasis is responsible for a large majority of death from malignant solid tumors. Bone is one of the most frequently affected organs in cancer metastasis, especially in breast and prostate cancer. Development of bone metastasis requires cancer cells to successfully complete a number of challenging steps, including local invasion and intravasation, survival in circulation, extravasation and initial seeding, and finally, formation of metastatic colonies after a period of dormancy or indolent growth. During this process, cancer cells often undergo a series of cellular and molecular changes to gain cellular plasticity that helps them adapt to various environments they encounter along the journey of metastasis. Understanding the mechanisms behind cellular plasticity and adaptation during the formation of bone metastasis is crucial for the development of novel therapies.

Introduction of a Cys360Tyr Mutation in ANO5 Creates a Mouse Model for Gnathodiaphyseal Dysplasia

Gnathodiaphyseal dysplasia (GDD) is a rare autosomal dominant genetic disease characterized by the osteosclerosis of tubular bones and the formation of cemento-osseous lesions in mandibles. Although genetic mutations for GDD have been identified in the ANO5/TMEM16E gene, the cellular and molecular mechanisms behind the pathogenesis of GDD remain unclear. Here, we generated the first knock-in mouse model for GDD with the expression of human mutation p.Cys360Tyr in ANO5. Homozygous Ano5 knock-in mice (Ano5^KI/KI ) replicated GDD-like skeletal features, including massive jawbones, bowing tibia, bone fragility, sclerosis, and cortical thickening of the femoral and tibial diaphysis. Serum alkaline phosphatase (ALP) levels were elevated in Ano5^KI/KI mice as in GDD patients with p.Cys360Tyr mutation. Calvaria-derived Ano5^KI/KI osteoblast cultures showed increased osteoblastogenesis, including hypermineralized bone matrix and enhanced bone formation-related factors expression. Interestingly, Ano5^KI/KI bone marrow-derived macrophage cultures showed decreased osteoclastogenesis, and Ano5^KI/KI osteoclasts exhibited disrupted actin ring formation, which may be associated with some signaling pathways. In conclusion, this new mouse model may facilitate elucidation of the pathogenesis of GDD and shed more light on its treatment. © 2021 American Society for Bone and Mineral Research (ASBMR).

Sulfated Undaria pinnatifida polysaccharide inhibits the formation of kidney stones by inhibiting HK-2 cell damage and reducing the adhesion of nano‑calcium oxalate crystals

OBJECTIVE

The formation of kidney stone is closely related to cell injury and crystal adhesion.

METHOD

The sulfur trioxide-pyridine method was used to sulfate raw Undaria pinnatifida polysaccharide (UPP) with a molecular weight (Mw) of 8.33 kDa. Four polysaccharides with the sulfate group (-OSO3-) contents of 1.59% (UPP0), 6.03% (UPP1), 20.83% (UPP2), and 36.39% (UPP3) were obtained. The antioxidant activity of the four UPPs, the difference in oxidative damage inflicted by nano-CaOx monohydrate (nano-COM) on human proximal tubular epithelial (HK-2) cells before and after protection by UPPs, and the inhibitory effect on nano-COM adhesion were explored.

RESULTS

Structural characterization showed that sulfation was successful. As the -OSO3- content in the UPPs was increased, the antioxidant activity and capability of the UPPs to regulate the growth of calcium oxalate (CaOx) crystals gradually increased. The damage caused by nano-COM crystals to HK-2 cells under protection by UPPs was weakened. This effect enhanced cell viability, enabled the maintenance of good cell morphology, reduced reactive oxygen species (ROS) levels, and inhibited the decrease in mitochondrial membrane potential, as well as decreased the eversion of phosphatidylserine (PS) and the expression of the adhesion proteins osteopontin (OPN), heat shock protein (HSP 90), and Annexin A1 (ANXA1). The adhesion of nano-COM to HK-2 cells was inhibited under the protection by UPPs.

CONCLUSION

UPP3 with the highest content of -OSO3- presented the best antioxidant activity and crystal regulation ability, while UPP2 with the second highest -OSO3- content showed optimal cell protection ability and crystal adhesion inhibition ability. The biological activity of UPPs was regulated by Mw and -OSO3- content. UPP2 with moderate -OSO3- content may become a potential drug for preventing CaOx stones.

Comparison of Synthetic vs. Biogenic Polymeric Process-Directing Agents for Intrafibrillar Mineralization of Collagen

With the aging population, there is a growing need for mineralized tissue restoration and synthetic bone substitutes. Previous studies have shown that a polymer-induced liquid-precursor (PILP) process can successfully mineralize collagen substrates to achieve compositions found in native bone and dentin. This process also leads to intrafibrillar apatitic crystals with their [001] axes aligned roughly parallel to the long axis of the collagen fibril, emulating the nanostructural organization found in native bone and dentin. When demineralized bovine bone was remineralized via the PILP process using osteopontin (OPN), the samples were able to activate mouse marrow-derived osteoclasts to similar levels to those of native bone, suggesting a means for fabricating bioactive bone substitutes that could trigger remodeling through the native bone multicellular unit (BMU). In order to determine if OPN derived from bovine milk could be a cost-effective process-directing agent, the mineralization of type I collagen scaffolds using this protein was compared to the benchmark polypeptide of polyaspartic acid (sodium salt; pAsp). In this set of experiments, we found that OPN led to much faster and more uniform mineralization when compared with pAsp, making it a cheaper and commercially attractive alternative for mineralized tissue restorations.

Osteopontin, a bridge links osteoarthritis and osteoporosis

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

Effects of the combination of bone morphogenetic protein-2 and nano-hydroxyapatite on the osseointegration of dental implants

OBJECTIVES

This study aimed to investigate the in vitro osteoinductivity of the combination of bone morphogenetic protein-2 (BMP-2) and nanohydroxyapatite (nHAp) and the in vivo effects of implants coated with nHAp/BMP-2.

MATERIALS AND METHODS

To evaluate the in vitro efficacy of nHAp/BMP-2 on bone formation, bone marrow-derived mesenchymal stem cells (BMMSCs) were seeded onto titanium disks coated with collagen (Col), Col/nHAp, or Col/nHAp/BMP-2. Protein levels were determined by a biochemical assay and reverse transcriptase-polymerase chain reaction. Stem cell differentiation was analyzed by flow cytometry. For in vivo studies with mice, Col, Col/nHAp, and Col/nHAp/BMP-2 were injected in subcutaneous pockets. Titanium implants or implants coated with Col/nHAp/BMP-2 were placed bilaterally on rabbit tibias and evaluated for 4 weeks.

RESULTS

In the in vitro study, BM-MSCs on Col/nHAp/BMP-2 showed reduced levels of CD73, CD90, and CD105 and increased levels of glycosaminoglycan, osteopontin, and alkaline phosphatase activity. After 4 weeks, the Col/nHAp/BMP-2 implant showed greater bone formation than the control (P=0.07), while no differences were observed in bone implant contact and removal torque.

CONCLUSION

These results suggest that a combination of BMP-2 and an nHAp carrier would activate osseointegration on dental implant surfaces.

The Bone Marrow Microenvironment Mechanisms in Acute Myeloid Leukemia

Bone marrow (BM) is a highly complex tissue that provides important regulatory signals to orchestrate hematopoiesis. Resident and transient cells occupy and interact with some well characterized niches to produce molecular and cellular mechanisms that interfere with differentiation, migration, survival, and proliferation in this microenvironment. The acute myeloid leukemia (AML), the most common and severe hematological neoplasm in adults, arises and develop in the BM. The osteoblastic, vascular, and reticular niches provide surface co-receptors, soluble factors, cytokines, and chemokines that mediate important functions on hematopoietic cells and leukemic blasts. There are some evidences of how AML modify the architecture and function of these three BM niches, but it has been still unclear how essential those modifications are to maintain AML development. Basic studies and clinical trials have been suggesting that disturbing specific cells and molecules into the BM niches might be able to impair leukemia competencies. Either through niche-specific molecule inhibition alone or in combination with more traditional drugs, the bone marrow microenvironment is currently considered the potential target for new strategies to treat AML patients. This review describes the cellular and molecular constitution of the BM niches under healthy and AML conditions, presenting this anatomical compartment by a new perspective: as a prospective target for current and next generation therapies.

In situ construction of a nano-structured akermanite coating for promoting bone formation and osseointegration of Ti-6Al-4V implants in a rabbit osteoporosis model

With the aging population worldwide, osteoporosis, as an age-related bone metabolic disease, is becoming a hot issue in public health. However, it is still a great challenge to realize osteoporotic bone healing due to the alteration of the bone microenvironment in osteoporosis patients. In this study, a nano-structured akermanite (nAK) coating was in situ constructed on Ti-6Al-4V implants to improve osteoporotic bone repair. In vitro studies indicated that both the surface nano-topography and bioactive ions released from the nAK coatings promoted the proliferation, osteogenesis, angiogenesis and inhibited osteoclastogenesis of ovariectomy rabbit-derived bone marrow mesenchymal stem cells (OVX-rBMSCs). Furthermore, the nAK-coated Ti-6Al-4V implants improved new bone formation and osseointegration in an osteoporosis rabbit model in vivo. These results indicated that the AK coating with a nano-structured surface on the Ti-6Al-4V implant could synergistically promote bone formation and osseointegration for osteoporosis patients. This may be a promising strategy to improve the bone regeneration and osseointegration capability of orthopedic implants under osteoporosis conditions.

The culture microenvironment of juvenile idiopathic arthritis synovial fibroblasts is favorable for endochondral bone formation through BMP4 and repressed by chondrocytes

BACKGROUND

We examined influences of conditioned media from chondrocytes (Ch) on juvenile idiopathic arthritis synovial fibroblasts (JFLS) and potential for JFLS to undergo endochondral bone formation (EBF).

METHODS

Primary cells from three control fibroblast-like synoviocytes (CFLS) and three JFLS were cultured in Ch-conditioned media and compared with untreated fibroblast-like synoviocytes (FLS). RNA was analyzed by ClariomS microarray. FLS cells cultured in conditioned media were exposed to either TGFBR1 inhibitor LY3200882 or exogenous BMP4 and compared with FLS cultured in conditioned media from Ch (JFLS-Ch). Media supernatants were analyzed by ELISA.

RESULTS

In culture, JFLS downregulate BMP2 and its receptor BMPR1a while upregulating BMP antagonists (NOG and CHRD) and express genes (MMP9, PCNA, MMP12) and proteins (COL2, COLX, COMP) associated with chondrocytes. Important TGFβ superfamily member gene expression (TGFBI, MMP9, COL1A1, SOX6, and MMP2) is downregulated when JFLS are cultured in Ch-conditioned media. COL2, COLX and COMP protein expression decreases in JFLS-Ch. BMP antagonist protein (NOG, CHRD, GREM, and FST) secretion is significantly increased in JFLS-Ch. Protein phosphorylation increases in JFLS-Ch exposed to exogenous BMP4, and chondrocyte-like phenotype is restored in BMP4 presence, evidenced by increased secretion of COL2 and COLX. Inhibition of TGFBR1 in JFLS-Ch results in overexpression of COL2.

CONCLUSIONS

JFLS are chondrocyte-like, and Ch-conditioned media can abrogate this phenotype. The addition of exogenous BMP4 causes JFLS-Ch to restore this chondrocyte-like phenotype, suggesting that JFLS create a microenvironment favorable for endochondral bone formation, thereby contributing to joint growth disturbances in juvenile idiopathic arthritis.

The effect of graft application and simvastatin treatment on tibial bone defect in rats. A histological and immunohistochemical study

Purpose:

To evaluate histologically and immunohistochemically the bone regeneration after application of simvastatin on tibial bone defects in rats.

Methods:

Sixty Wistar albino rats were divided into 3 groups as control (6 mm tibial bone defect), defect + graft (allograft treatment), and defect + graft + simvastatin (10 mg/kg/day) for 28 days.

Results:

Histopathological examination revealed inflammation in control group (defect group), congestion in blood vessels, and an increase in osteoclast cells. In defect + graft group, osteoclastic activity was observed and osteocyte cells were continued to develop. In defect + graft + simvastatin group, osteocytes and matrix formation were increased in the new bone trabeculae. Osteopontin and osteonectin expression were positive in the osteclast cells in the control group. Osteoblasts and some osteocytes showed a positive reaction of osteopontin and osteopontin. In defect + graft + simvastatin group, osteonectin and osteopontin expression were positive in osteoblast and osteocyte cells, and a positive expression in osteon formation was also seen in new bone trabeculae.

Conclusion:

The simvastatin application was thought to increase bone turnover by increasing the osteoinductive effect with graft and significantly affect the formation of new bone.

Identification of a Novel Transcription Factor Required for Osteogenic Differentiation of Mesenchymal Stem Cells

Osteogenic differentiation is a complex and still poorly understood biological process regulated by intrinsic cellular signals and extrinsic microenvironmental cues. Following appropriate stimuli, mesenchymal stem cells (MSCs) differentiate into osteoblasts through a tightly regulated multistep process driven by several transcription factors and characterized by the expression of a number of bone-specific proteins. In this study, we describe a novel transcription factor that we named osteoblast inducer (ObI)-1, involved in MSC differentiation toward the osteogenic lineage. ObI-1 encodes for a nuclear protein subjected to proteasomal degradation and expressed during osteoblast differentiation both in a murine multipotent mesenchymal cell line (W20-17) and in primary murine MSCs. RNA interference-mediated knockdown of ObI-1 expression significantly impairs osteoblast differentiation and matrix mineralization with reduced expression of the osteogenic markers, Runt-related transcription factor 2 (Runx2) and osteopontin. Conversely, ObI-1 overexpression enhances osteogenic differentiation and bone-specific markers expression. ObI-1 stimulates bone morphogenetic protein (BMP)-4 expression and the consequent activation of the Smad pathway; treatment with a BMP receptor type I antagonist completely abolishes ObI-1-mediated stimulation of osteogenic differentiation. Collectively, our findings suggest that ObI-1 modulates osteogenic differentiation, at least in part, through the BMP signaling pathway, increasing Runx2 activation and leading to osteoblast commitment and maturation.

Microwave-assisted synthesis and in vitro osteogenic analysis of novel bioactive glass fibers for biomedical and dental applications

Glass fiber-based materials have gained interest for use in biomedical and dental applications. The aim of this study was to make E-glass fiber bioactive by a novel method using the microwave irradiation technique. Industrial E-glass fibers were used after surface activation with the hydrolysis method. The ratio of calcium and phosphorous precursors was set at 1.67. After maintaining the pH of the calcium solution, E-glass fibers in two ratios, i.e. 30% (nHA/E30) and 50% (nHA/E50) wt/wt, were added. The phosphorous precursor was added later and the solution was irradiated in a microwave to obtain nano-hydroxyapatite (nHA) particles on E-glass fibers. The structural, physical and in vitro biocompatibility analyses of the resulting materials were conducted. The expression of osteopontin (OPN) and collagen (Col) type 1 was measured by reverse transcription polymerase chain reaction (RT-PCR) and comparison was made between all the groups. Fourier transform infrared spectroscopy and x-ray diffraction showed characteristic peaks of nHA, and a change in the peak intensities was observed with an increase in the concentration of E-glass fibers. Scanning electron microscopic (SEM) images confirmed the homogenous adhesion of nHA spherical particles all over the fibers. Cell viability with mesenchymal stem cells showed growth, proliferation, and adhesion. All the materials were able to upregulate the expression of the OPN and Col, where gene expression was highest in nHA followed by nHA/E30 and nHA/E50. The bioactive glass fibers were synthesized in the shortest time and showed osteogenic properties. These materials have the potential for use in bone tissue engineering, dental prosthesis, and tooth restoration.

Surface-immobilized plant-derived osteopontin as an effective platform to promote osteoblast adhesion and differentiation

In this report, recombinant human osteopontin synthesized in tobacco plants (p-rhOPN) is introduced as a potential bioactive molecule that can promote osteoblast adhesion and differentiation. A glass substrate (SiO₂/Si-OH) grafted with poly(acrylic acid) (SiO₂/Si-PAA) was prepared by surface-initiated reversible addition-fragmentation chain transfer polymerization and used as a carboxyl-rich platform for the chemical conjugation of p-rhOPN. The PAA grafting and subsequent p-rhOPN immobilization were confirmed by water contact angle, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy analyses. Indirect ELISA quantification revealed that the p-rhOPN immobilization efficiency was above 95% and the surface coverage was a function of the p-rhOPN concentration. MC-3T3-E1 cells cultured on the SiO₂/Si-PAA substrate immobilized with various concentrations (0.6-30 ng/mL) of p-rhOPN (SiO₂/Si-p-rhOPN) exhibited superior cell spreading compared to those cultured on SiO₂/Si-OH or gelatin-modified glass substrate (SiO₂/Si-gelatin). Polymerase chain reaction analysis indicated that the SiO₂/Si-p-rhOPN substrates with high level of immobilized p-rhOPN promoted MC-3T3-E1 cell differentiation, as demonstrated by the higher transcript expression levels of the osteogenic differentiation regulatory gene, Runt-related transcription factor 2, compared to cells cultured on SiO₂/Si-OH or SiO₂/Si-gelatin. Given that p-rhOPN can be more economically produced than the commercially available OPN derived from human or mammalian sources, then, together with its well-preserved biological function in spite of being chemically conjugated to the substrates, it is likely that p-rhOPN could be more broadly applied for the development of materials for bone tissue engineering with a promising medical and commercial value.

Polymeric electrospun scaffolds for bone morphogenetic protein 2 delivery in bone tissue engineering

HYPOTHESIS

The development of novel scaffolds based on biocompatible polymers is of great interest in the field of bone repair for fabrication of biodegradable scaffolds that mimic the extracellular matrix and have osteoconductive and osteoinductive properties for enhanced bone regeneration.

EXPERIMENTS

Polycaprolactone (PCL) and polycaprolactone/polyvinyl acetate (PCL/PVAc) core-shell fibers were synthesised and decorated with poly(lactic-co-glycolic acid) [PLGA] particles loaded with bone morphogenetic protein 2 (BMP2) by simultaneous electrospinning and electrospraying. Hydroxyapatite nanorods (HAn) were loaded into the core of fibers. The obtained scaffolds were characterised by scanning and transmission electron microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The in vitro potential of these materials for bone regeneration was assessed in biodegradation assays, osteoblast viability assays, and analyses of expression of specific bone markers, such as alkaline phosphatase (ALP), osteocalcin (OCN), and osteopontin (OPN).

FINDINGS

PLGA particles were homogeneously distributed in the entire fibre mat. The growth factor load was 1.2-1.7 μg/g of the scaffold whereas the HAn load was in the 8.8-12.6 wt% range. These scaffolds were able to support and enhance cell growth and proliferation facilitating the expression of osteogenic and osteoconductive markers (OCN and OPN). These observations underline the great importance of the presence of BMP2 in scaffolds for bone remodelling as well as the good potential of the newly developed scaffolds for clinical use in tissue engineering.

Strontium-Doped Bioactive Glass Nanoparticles in Osteogenic Commitment

The present work has explored bioactive glass nanoparticles (BGNPs) and developed strontium-doped nanoparticles (BGNPsSr), envisioning orthopedic strategies compatible with vascularization. The nanoparticles were synthesized by the sol-gel method, achieving a diameter of 55 nm for BGNPs and 75 nm for BGNPsSr, and the inclusion of strontium caused no structural alteration. The nanoparticles exhibited high cytocompatibility for human umbilical vein endothelial cells (HUVECs) and SaOS-2. Additionally, the incorporation of strontium emphasized the tubule networking behavior of HUVECs. Our results demonstrate that the nanoparticle dissolution products encouraged the osteogenic differentiation of human adipose stem cells as it favored the expression of key genes and proteins associated with osteogenic lineage. This effect was markedly enhanced for BGNPsSr, which could prompt stem cell osteogenic differentiation without the typical osteogenic inducers. This study not only supports the hypothesis that BGNPs might play a significant role in osteogenic commitment but also highlights that the designed BGNPsSr is a valuable tool for stem cell "tune-up" in bone tissue engineering applications.

Upregulation of osteogenesis of mesenchymal stem cells with virus-based thin films

A major aim of tissue engineering is to develop biomimetic scaffolding materials that can guide the proliferation, self-renewal and differentiation of multipotent stem cells into specific lineages. Cellular functions can be controlled by the interactions between cells and biomaterials. Therefore, the surface chemistry and topography of support materials play a pivotal role in modulating cell behaviors at many stages of cell growth and development. Due to their highly ordered structure and programmable surface chemistries, which provide unique topography as biomaterials, viral nanoparticles have been utilized as building blocks for targeted cell growth and differentiation. This review article discusses the fabrication of two-dimensional virus-based thin film on substrates and highlights the study of the effect of chemical and physical cues introduced by plant virus nanoparticle thin films on the promotion of osteogenic differentiation of BMSCs.

The potential role of Osteopontin in the maintenance of commensal bacteria homeostasis in the intestine

Osteopontin (Opn), a multifunctional extracellular matrix protein, is implicated in the pathogenesis of various inflammatory disorders. Under physiologic conditions, its expression is restricted to certain tissues including bone and kidney tubule. However, cellular activation during disease development induces Opn expression in various immune cells. In this study, using Opn-EGFP knock-in (KI) mice we found that CD8α⁺ T cells in the intestinal tissues, including Peyer’s patch, lamina propria and epithelium, express Opn under steady state conditions. Therefore, we examined the role of Opn-expressing CD8α⁺ T cells in intestinal homeostasis. Interestingly, Opn knockout (KO) mice had altered fecal microflora concordant with a reduction of TCRγδ⁺ intraepithelial lymphocytes (IELs). Consistent with this result, both treatment with anti-Opn blocking antibody and deficiency of Opn resulted in decreased survival of TCRγδ⁺ and TCRαβ⁺ IELs. This data suggests that a possibility that Opn may function as a survival factor for IELs in the intestinal tissue. Collectively, these data suggest the possibility that Opn might regulate the homeostasis of intestinal microflora through maintenance of TCRγδ⁺ IELs, possibly by support of IEL survival.

Osteopontin as a discriminating marker for pancreatic cancer and chronic pancreatitis

INTRODUCTION

We analyzed concentrations of osteopontin (OPN) in patients with pancreatic ductal adenocarcinoma (PDAC) in order to determine firstly whether it is useful to distinguish between PDAC patients and those with chronic non-hereditary pancreatitis (CP) and type 2 diabetes mellitus (T2DM), and secondly whether OPN concentrations depend on the PDAC stage.

METHODS

Groups consisting of 64 patients with PDAC, 71 with CP, 67 with T2DM and 48 healthy controls (CON) were enrolled in the study. Controls were compared with regard to levels of OPN, oxidative stress markers, conventional tumor markers and other biochemical parameters.

RESULTS

Levels of OPN were higher in patients with PDAC compared with CP patients (P< 0.001), T2DM (P< 0.001) and CON (P< 0.001). There were increased OPN levels in CP patients in comparison with T2DM (P< 0.001) and CON (P< 0.001). Patients with PDAC in stage IV had higher OPN levels than PDAC patients in stage III (P< 0.01). There was no difference in OPN levels of PDAC patients in stage III compared to patients in stage II.

CONCLUSION

Our pilot study demonstrates the usefulness of estimating OPN levels to differentiate between pancreatic cancer and chronic pancreatitis. Higher OPN levels over 102 ng/ml could be a potential diagnostic biomarker for pancreatic cancer.

Aluminum Trichloride Inhibits the Rat Osteoblasts Mineralization In Vitro

Aluminum (Al) is an accumulative toxic metal. Excessive Al accumulation inhibits osteoblasts mineralization and induces osteoporosis. However, the inhibition mechanism of Al on the mineralization is not fully understood. Thus, in this study, the rat osteoblasts were cultured and exposed to 0 mmol L^-1 (control group, CG) and 0.52 mmol L^-1 aluminum trichloride (AlCl₃, treatment group, TG) for 7, 14, and 21 days, respectively. We found that mineralized matrix nodules, the activity of bone alkaline phosphatase, the concentration of extracellular calcium, the mRNA expression of type-I collagen, the mRNA and protein expressions of osteopontin, osteocalcin, and bone sialoprotein were all decreased, while the concentration of extracellular phosphorus was increased in TG compared with CG with time prolonged. Taken together, these results indicated that AlCl₃ inhibited osteoblasts mineralization in vitro.

Cancer Secretome May Influence BSP and DSP Expression in Human Salivary Gland Cells

One of the biggest challenges in managing head and neck cancers, especially salivary gland cancers, is the identification of secreted biomarkers of the disease that can be evaluated noninvasively. A relevant source of enriched tumor markers could potentially be found in the tumor secretome. Although numerous studies have evaluated secretomes from various cancers, the influence of the cancer secretome derived from salivary gland cancers on the behavior of normal cells has not yet been elucidated. Our data indicate that secretome derived from salivary gland cancer cells can influence the expression of two potential biomarkers of oral cancer-namely, bone sialoprotein (BSP) and dentin sialoprotein (DSP)-in normal salivary gland cells. Using routine immunohistochemistry, immunofluorescence, and immunoblotting techniques, we demonstrate an enrichment of BSP and DSP in human salivary gland (HSG) cancer tissue, unique localizations of BSP and DSP in HSG cancer cells, and enriched expression of BSP and DSP in normal salivary gland cells exposed to a cancer secretome. The secretome domain of the cancer microenvironment could alter signaling cascades responsible for normal cell proliferation, migration, and invasion, thus enhancing cancer cell survival and the potential for cancer progression. The cancer secretome may be critical in maintaining and stimulating "cancer-ness," thus potentially promoting specific hallmarks of metastasis.

The influence of calcitonin gene-related peptide on markers of bone metabolism in MG-63 osteoblast-like cells co-cultured with THP-1 macrophage-like cells under virtually osteolytic conditions

Background

The neuropeptide calcitonin gene-related peptide (CGRP) has been described to have an inhibitory effect on endotoxin- and wear particle-induced inflammation in the early stages of periprosthetic osteolysis. In the present study, the crosstalk between immune cells and osteoblasts in osteolytic conditions treated with CGRP has been analyzed to evaluate whether the anti-inflammatory properties of the peptide also have a beneficial, i.e. an anti-resorptive and osteo-anabolic impact on bone metabolism.

Methods

MG-63 osteoblast-like cells were co-cultured with THP-1 macrophage-like cells stimulated with either ultra-high molecular weight polyethylene (UHMWPE) particles or different concentrations of bacterial lipopolysaccharides (LPS) and simultaneously treated with CGRP. Inflammation was monitored in terms of measuring the levels of tumor necrosis factor (TNF)-α secretion. Furthermore, the production of the osteoblast markers osteoprotegerin (OPG), receptor activator of nuclear factor κB ligand (RANKL), alkaline phosphatase (ALP) and osteopontin (OPN) was quantified. Also, ALP enzymatic activity was measured.

Results

Stimulation of co-cultured THP-1 macrophages with either high levels of LPS or UHMWPE induced the secretion of TNF-α which could be inhibited by CGRP to a great extent. However, no remarkable changes in the OPG/RANKL ratio or bone ALP activity were observed. Interestingly, OPN was exclusively produced by THP-1 cells, thus acting as a marker of inflammation. In addition, TNF-α production in THP-1 single cell cultures was found to be considerably higher than in co-cultured cells.

Conclusions

In the co-culture system used in the present study, no obvious relation between inflammation, its mitigation by CGRP, and the modulation of bone metabolism became evident. Nonetheless, the results suggest that during the onset of periprosthetic osteolysis the focus might lie on the modulation of inflammatory reactions. Possibly, implant-related inflammation might merely have an impact on osteoclast differentiation rather than on the regulation of osteoblast activity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-1044-5) contains supplementary material, which is available to authorized users.

Proinflammatory Cytokines Regulate Cementogenic Differentiation of Periodontal Ligament Cells by Wnt/Ca(2+) Signaling Pathway

Periodontal inflammation can inhibit cell differentiation of periodontal ligament cells (PDLCs), resulting in decreased bone/cementum regeneration ability. The Wnt signaling pathway, including canonical Wnt/β-catenin signaling and noncanonical Wnt/Ca(2+) signaling, plays essential roles in cell proliferation and differentiation during tooth development. However, little is still known whether noncanonical Wnt/Ca(2+) signaling cascade could regulate cementogenic/osteogenic differentiation capability of PDLCs within an inflammatory environment. Therefore, in this study, human PDLCs (hPDLCs) and their cementogenic differentiation potential were investigated in the presence of cytokines. The data demonstrated that both cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) inhibited cell proliferation, relative alkaline phosphatase activity, bone/cementum-related gene/protein expression, and canonical Wnt pathway-related gene/protein expression in hPDLCs. Interestingly, both cytokines upregulated the noncanonical Wnt/Ca(2+) signaling-related gene and protein expression in hPDLCs. When the Wnt/Ca(2+) pathway was blocked by Ca(2+)/calmodulin-dependent protein kinase II inhibitor KN93, even in the presence of IL-6 and TNF-α, cementogenesis could be stimulated in hPDLCs. Our data indicate that the Wnt/Ca(2+) pathway plays an inhibitory role on PDLC cementogenic differentiation in inflammatory microenvironments. Therefore, targeting the Wnt/Ca(2+) pathway may provide a novel therapeutic approach to improve periodontal regeneration for periodontal diseases.

Pyruvate Kinase M2: A Novel Biomarker for the Early Detection of Acute Kidney Injury

The identification of biomarkers for the early detection of acute kidney injury (AKI) is clinically important. Acute kidney injury (AKI) in critically ill patients is closely associated with increased morbidity and mortality. Conventional biomarkers, such as serum creatinine (SCr) and blood urea nitrogen (BUN), are frequently used to diagnose AKI. However, these biomarkers increase only after significant structural damage has occurred. Recent efforts have focused on identification and validation of new noninvasive biomarkers for the early detection of AKI, prior to extensive structural damage. Furthermore, AKI biomarkers can provide valuable insight into the molecular mechanisms of this complex and heterogeneous disease. Our previous study suggested that pyruvate kinase M2 (PKM2), which is excreted in the urine, is a sensitive biomarker for nephrotoxicity. To appropriately and optimally utilize PKM2 as a biomarker for AKI requires its complete characterization. This review highlights the major studies that have addressed the diagnostic and prognostic predictive power of biomarkers for AKI and assesses the potential usage of PKM2 as an early biomarker for AKI. We summarize the current state of knowledge regarding the role of biomarkers and the molecular and cellular mechanisms of AKI. This review will elucidate the biological basis of specific biomarkers that will contribute to improving the early detection and diagnosis of AKI.

Isolation, Characterization, and Differentiation of Dental Pulp Stem Cells in Ferrets

INTRODUCTION

The ferret canine tooth has been introduced as a suitable model for studying dental pulp regeneration. The aim of this study was to isolate and characterize ferret dental pulp stem cells (fDPSCs) and their differentiation potential.

METHODS

Dental pulp stem cells were isolated from freshly extracted ferret canine teeth. The cells were examined for the expression of stem cell markers STRO-1, CD90, CD105, and CD146. The osteo/odontogenic and adipogenic differentiation potential of fDPSCs was evaluated. Osteogenic and odontogenic marker genes were evaluated using quantitative real-time polymerase chain reaction (qRT-PCR) on days 1, 4, and 8 after osteo/odontogenic induction of fDPSCs including dentin sialophosphoprotein (DSPP), dentin matrix protein-1, osteopontin, and alkaline phosphatase. Human dental pulp cells were used as the control. The results were analyzed using 3-way analysis of variance.

RESULTS

fDPSCs were positive for STRO1, CD90, and CD105 and negative for CD146 markers with immunohistochemistry. fDPSCs showed strong osteogenic and weak adipogenic potential. The overall expression of DSPP was not significantly different between fDPSCs and human dental pulp cells. The expression of DSPP in osteo/odontogenic media was significantly higher in fDPSCs on day 4 (P < .01). The overall expression of dentin matrix protein-1, osteopontin, and alkaline phosphatase was significantly higher in fDPSCs (P = .0005).

CONCLUSIONS

fDPSCs were positive for several markers of dental pulp stem cells resembling human DPSCs and appeared to show a stronger potential to differentiate to osteoblastic rather than odontoblastic lineage.

A potential mechanism for amino acid-controlled crystal growth of hydroxyapatite

The mineral component of bone, dentin and calcified parts of avian tendon, hydroxyapatite (HAP), has non-stoichiometric composition (idealized as Ca₁₀(PO₄)₆(OH)₂), plate-like morphology and nanometer size. This unique crystal morphology contributes to the physico-chemical and biochemical properties of bone. Thus, understanding the mechanism for the controlled growth of plate-like HAP nanocrystals is significant in the study of bone biomineralization. Previous studies have shown that acidic non-collagenous proteins (ANCPs), which are enriched in the residues of acidic amino acids, may play an important role in HAP crystal growth modulation. In this study, glutamic acid (Glu) and phosphoserine (Ser-OPO₃) were used as model compounds to modify the synthesis of HAP nanocrystals. To identify the mechanisms of amino acids as regulators, X-ray diffraction (XRD), transmission electron microscopy (TEM) and solid state nuclear magnetic resonance (ssNMR) were used. The crystals obtained in the inorganic controls were needle-like, while crystals synthesized in the presence of the amino acids presented a plate-like morphology. The plate-like crystals had a preferred crystal orientation on (300) face, which was lacking in the inorganically grown crystals, indicating preferential adsorption and suppression of growth in specific crystal directions. Ser-OPO₃ was more efficient than Glu in modulating HAP nucleation and crystal growth. Furthermore, NMR revealed interactions between the charged side chain groups in amino acids and the crystal surfaces. These results were successfully explained through our MD simulations for the free energy calculation of amino acid binding on HAP crystal faces. The present study revealed that amino acids may act as effective regulators of HAP morphology without the need to invoke large NCPs in bone biomineralization and in designing bioinspired materials for orthopaedic and dental applications.

Virus Nanoparticles Mediated Osteogenic Differentiation of Bone Derived Mesenchymal Stem Cells

There are few methodologies that allow manipulating a biomaterial surface at nanometer scale, which controllably influence different cellular functions. In this study, virus nanoparticles with different structural features are selected to prepare 2D substrates with defined nanoscale topographies and the cellular responses are investigated. It is demonstrated that the viral nanoparticle based substrates could accelerate and enhance osteogenesis of bone derived mesenchymal stem cells as indicated by the upregulation of osteogenic markers, including bone morphogenetic protein-2, osteocalcin, and osteopontin, at both gene and protein expression levels. Moreover, alkaline phosphatase activity and calcium mineralization, both indicators for a -successful bone formation, are also increased in cells grown on these nanoscale possessed substrates. These discoveries and developments present a new paradigm for nanoscale engineering of a biomaterial surface.

Molecular targets in arthritis and recent trends in nanotherapy

Due to its severity and increasing epidemiology, arthritis needs no description. There are various forms of arthritis most of which are disabling, very painful, and common. In spite of breakthroughs in the field of drug discovery, there is no cure for arthritis that can eliminate the disease permanently and ease the pain. The present review focuses on some of the most successful drugs in arthritis therapy and their side effects. Potential new targets in arthritis therapy such as interleukin-1β, interleukin-17A, tumor necrosis factor alpha, osteopontin, and several others have been discussed here, which can lead to refinement of current therapeutic modalities. Mechanisms for different forms of arthritis have been discussed along with the molecules that act as potential biomarkers for arthritis. Due to the difficulty in monitoring the disease progression to detect the advanced manifestations of the diseases, drug-induced cytotoxicity, and problems with drug delivery; nanoparticle therapy has gained the attention of the researchers. The unique properties of nanoparticles make them highly attractive for the design of novel therapeutics or diagnostic agents for arthritis. The review also focuses on the recent trends in nanoformulation development used for arthritis therapy. This review is, therefore, important because it describes the relevance and need for more arthritis research, it brings forth a critical discussion of successful drugs in arthritis and analyses the key molecular targets. The review also identifies several knowledge gaps in the published research so far along with the proposal of new ideas and future directions in arthritis therapy.

Osteopontin mediates mineralization and not osteogenic cell development in vitro

Biomineralization is a complex process in the development of mineralized tissues such as bone and pathological calcifications such as atherosclerotic plaques, kidney stones and gout. Osteopontin (OPN), an anionic phosphoprotein, is expressed in mineralizing tissues and has previously been demonstrated to be a potent inhibitor of hydroxyapatite formation. The OPN-deficient (Opn-/-) mouse displays a hypermineralized bone phenotype starting at 12 weeks postnatally. By isolating and culturing Opn-/- and wild-type (WT) osteoblasts, we sought to determine the role of OPN and two of its functional peptides in osteoblast development and mineralization. Opn-/- osteoblasts had significantly increased mineral deposition relative to their WT counterparts, with no physiologically relevant change in gene expression of osteogenic markers. Supplementation with bovine milk OPN (mOPN) led to a dramatic reduction in mineral deposition by the Opn-/- osteoblasts. Treatment with OPN-derived peptides corresponding to phosphorylated OPN-(220-235) (P3) and non-phosphorylated OPN-(65-80) (OPAR) also rescued the hypermineralization phenotype of Opn-/- osteogenic cultures. Supplementation with mOPN or the OPN-derived peptides did not alter the expression of terminal osteogenic markers. These data suggest that OPN plays an important role in the regulation of biomineralization, but that OPN does not appear to affect osteoblast cell development in vitro.

Zbtb20 regulates the terminal differentiation of hypertrophic chondrocytes via repression of Sox9

The terminal differentiation of hypertrophic chondrocytes is a tightly regulated process that plays a pivotal role in endochondral ossification. As a negative regulator, Sox9 is essentially downregulated in terminally differentiated hypertrophic chondrocytes. However, the underlying mechanism of Sox9 silencing is undefined. Here we show that the zinc finger protein Zbtb20 regulates the terminal differentiation of hypertrophic chondrocytes by repressing Sox9. In the developing skeleton of the mouse, Zbtb20 protein is highly expressed by hypertrophic chondrocytes from late embryonic stages. To determine its physiological role in endochondral ossification, we have generated chondrocyte-specific Zbtb20 knockout mice and demonstrate that disruption of Zbtb20 in chondrocytes results in delayed endochondral ossification and postnatal growth retardation. Zbtb20 deficiency caused a delay in cartilage vascularization and an expansion of the hypertrophic zone owing to reduced expression of Vegfa in the hypertrophic zone. Interestingly, Sox9, a direct suppressor of Vegfa expression, was ectopically upregulated at both mRNA and protein levels in the late Zbtb20-deficient hypertrophic zone. Furthermore, knockdown of Sox9 greatly increased Vegfa expression in Zbtb20-deficient hypertrophic chondrocytes. Our findings point to Zbtb20 as a crucial regulator governing the terminal differentiation of hypertrophic chondrocytes at least partially through repression of Sox9.

Multifunctional role of osteopontin in directing intrafibrillar mineralization of collagen and activation of osteoclasts

Mineralized collagen composites are of interest because they have the potential to provide a bone-like scaffold that stimulates the natural processes of resorption and remodeling. Working towards this goal, our group has previously shown that the nanostructure of bone can be reproduced using a polymer-induced liquid-precursor (PILP) process, which enables intrafibrillar mineralization of collagen with hydroxyapatite to be achieved. This prior work used polyaspartic acid (pASP), a simple mimic for acidic non-collagenous proteins, to generate nanodroplets/nanoparticles of an amorphous mineral precursor which can infiltrate the interstices of type-I collagen fibrils. In this study we show that osteopontin (OPN) can similarly serve as a process-directing agent for the intrafibrillar mineralization of collagen, even though OPN is generally considered a mineralization inhibitor. We also found that inclusion of OPN in the mineralization process promotes the interaction of mouse marrow-derived osteoclasts with PILP-remineralized bone that was previously demineralized, as measured by actin ring formation. While osteoclast activation occurred when pASP was used as the process-directing agent, using OPN resulted in a dramatic effect on osteoclast activation, presumably because of the inherent arginine-glycine-aspartate acid ligands of OPN. By capitalizing on the multifunctionality of OPN, these studies may lead the way to producing biomimetic bone substitutes with the capability of tailorable bioresorption rates.

Characterization of adipose-derived mesenchymal stem cell combinations for vascularized bone engineering

Since bone repair and regeneration depend on vasculogenesis and osteogenesis, both of these processes are essential for successful vascularized bone engineering. Using adipose-derived stem cells (ASCs), we investigated temporal gene expression profiles, as well as bone nodule and endothelial tubule formation capacities, during osteogenic and vasculogenic ASC lineage commitment. Osteoprogenitor-enriched cell populations were found to express RUNX2, MSX2, SP7 (osterix), BGLAP (osteocalcin), SPARC (osteonectin), and SPP1 (osteopontin) in a temporally specific sequence. Irreversible commitment of ASCs to the osteogenic lineage occurred between days 6 and 9 of differentiation. Endothelioprogenitor-enriched cell populations expressed CD34, PECAM1 (CD31), ENG (CD105), FLT1 (Vascular endothelial growth factor [VEGFR1]), and KDR (VEGFR2). Capacity for microtubule formation was evident in as early as 3 days. Functional capacity was assessed in eight coculture combinations for both bone nodule and endothelial tubule formation, and the greatest expression of these end-differentiation phenotypes was observed in the combination of well-differentiated endothelial cells with less-differentiated osteoblastic cells. Taken together, our results demonstrate vascularized bone engineering utilizing ASCs is a promising enterprise, and that coculture strategies should focus on developing a more mature vascular network in combination with a less mature osteoblastic stromal cell.

Mechanical strain promotes osteoblast ECM formation and improves its osteoinductive potential

BACKGROUND

The extracellular matrix (ECM) provides a supportive microenvironment for cells, which is suitable as a tissue engineering scaffold. Mechanical stimulus plays a significant role in the fate of osteoblast, suggesting that it regulates ECM formation. Therefore, we investigated the influence of mechanical stimulus on ECM formation and bioactivity.

METHODS

Mouse osteoblastic MC3T3-E1 cells were cultured in cell culture dishes and stimulated with mechanical tensile strain. After removing the cells, the ECMs coated on dishes were prepared. The ECM protein and calcium were assayed and MC3T3-E1 cells were re-seeded on the ECM-coated dishes to assess osteoinductive potential of the ECM.

RESULTS

The cyclic tensile strain increased collagen, bone morphogenetic protein 2 (BMP-2), BMP-4, and calcium levels in the ECM. Compared with the ECM produced by unstrained osteoblasts, those of mechanically stimulated osteoblasts promoted alkaline phosphatase activity, elevated BMP-2 and osteopontin levels and mRNA levels of runt-related transcriptional factor 2 (Runx2) and osteocalcin (OCN), and increased secreted calcium of the re-seeded MC3T3-E1 cells.

CONCLUSION

Mechanical strain promoted ECM production of osteoblasts in vitro, increased BMP-2/4 levels, and improved osteoinductive potential of the ECM. This study provided a novel method to enhance bioactivity of bone ECM in vitro via mechanical strain to osteoblasts.

Sequential expression of osteoblast phenotypic genes during medullary bone formation and resorption in estrogen-treated male Japanese quails

Medullary bone is formed reticularly in the bone marrow cavity of the long bones of female birds. Although this bone matrix contains fewer collagen fibers and more acid mucopolysaccharides than cortical bone, it is not clear that the expression pattern of osteoblast phenotypic genes during bone remodeling. Therefore, 17β-estradiol (E2)-treated male Japanese quails were used to examine the temporal expression patterns of osteoblast phenotypic genes, and to simultaneously confirm the morphological changes occurring in the bone marrow cavity during medullary bone formation and resorption. After E2 treatment, bone lining cells proliferated and developed into mature osteoblasts that had intense alkaline phosphatase (ALP) activity. These cells began to form medullary bone that contained acid mucopolysaccharides and tartrate-resistantacid phosphatase. Runt-related gene 2 (Runx2) mRNA was stably expressed throughout the process. The expression of both ALP and type I collagen mRNAs increased initially, and then rapidly decreased after day 7, while osteoclasts began to resorb medullary bone at day 5. The expression of bone matrix-related genes peaked at day 5, and suddenly decreased at day 7, except for osteopontin. Taken together with these results, the expression patterns of bone matrix-related genes during the later stages might be related to osteoclast activity. Additionally, the constant expression of Runx2 during bone formation and resorption suggested that osteoprogenitor cells always exist in the bone marrow cavity. Therefore, the expression patterns of these genes and the characteristics of bone matrix might extremely be related to the quick remodeling of medullary bone.

Biodegradable poly(butylene succinate) modified by gas plasmas and their in vitro functions as bone implants

Artificial implants are alternatives to autologous grafts in repairing severe bone damage and in many clinical applications, the artificial implant materials should be biodegradable in order to avoid chronic problems associated with biostable implants. In this study, a biodegradable biopolymer, poly(butylene succinate) (PBSu), is treated by N(2), NH(3) and H(2)O plasmas and investigated as bone replacement materials in vitro to obtain a better understanding of the behavior of osteoblasts on the different plasma-treated materials. N(2), NH(3), and H(2)O plasma immersion ion implantation (PIII) produces dominant C-N, C═N, and C-O surface functional groups, respectively rendering the materials with hydrophilic characteristics which favor osteoblast adhesion and early proliferation. In particular, N-containing groups, especially C═N, are more positive to osteogenic differentiation of the seeded osteoblasts than C-O. Among the 3 plasma treatments, NH(3) PIII is the most effective, yielding surface properties that are suitable for artificial bone implants.

Behaviour of rat-cultured dental pulp cells in three-dimensional collagen type-1 gel in vitro and in vivo

The purpose of this study was to investigate the growth and differentiation potential of dental pulp cells (DPCs) in three-dimensional (3-D) collagen type-1 scaffold in vitro and in vivo. Third passage DPCs were cultured in a 3-D collagen and expression of both bone- or dentin-related mRNA (alkaline phosphatase (ALP), bone sialoprotein (BSP) and osteopontin (OPN)) and morphological changes evaluated in vitro. In the in vivo study, two types of grafts were transplanted into the rectus abdominus muscles of rats and harvested after 7 days: DPCs in α-minimal essential medium and DPCs mixed with a collagen gel. ALP, BSP and OPN were used as primary antibodies for immunohistochemical study. Histological and immunohistochemical results showed that DPCs in collagen gel were spindle shaped and showed significantly greater expression of ALP, BSP and OPN in vitro than the controls. Transplanted DPCs in collagen type-1 gel showed greater positive immunoreactivity for ALP, BSP and OPN than the controls. It was concluded that the collagen gel scaffold encouraged the differentiation of DPCs into osteoblastic cells.

Transcriptional profiling of bovine milk using RNA sequencing

BACKGROUND

Cow milk is a complex bioactive fluid consumed by humans beyond infancy. Even though the chemical and physical properties of cow milk are well characterized, very limited research has been done on characterizing the milk transcriptome. This study performs a comprehensive expression profiling of genes expressed in milk somatic cells of transition (day 15), peak (day 90) and late (day 250) lactation Holstein cows by RNA sequencing. Milk samples were collected from Holstein cows at 15, 90 and 250 days of lactation, and RNA was extracted from the pelleted milk cells. Gene expression analysis was conducted by Illumina RNA sequencing. Sequence reads were assembled and analyzed in CLC Genomics Workbench. Gene Ontology (GO) and pathway analysis were performed using the Blast2GO program and GeneGo application of MetaCore program.

RESULTS

A total of 16,892 genes were expressed in transition lactation, 19,094 genes were expressed in peak lactation and 18,070 genes were expressed in late lactation. Regardless of the lactation stage approximately 9,000 genes showed ubiquitous expression. Genes encoding caseins, whey proteins and enzymes in lactose synthesis pathway showed higher expression in early lactation. The majority of genes in the fat metabolism pathway had high expression in transition and peak lactation milk. Most of the genes encoding for endogenous proteases and enzymes in ubiquitin-proteasome pathway showed higher expression along the course of lactation.

CONCLUSIONS

This is the first study to describe the comprehensive bovine milk transcriptome in Holstein cows. The results revealed that 69% of NCBI Btau 4.0 annotated genes are expressed in bovine milk somatic cells. Most of the genes were ubiquitously expressed in all three stages of lactation. However, a fraction of the milk transcriptome has genes devoted to specific functions unique to the lactation stage. This indicates the ability of milk somatic cells to adapt to different molecular functions according to the biological need of the animal. This study provides a valuable insight into the biology of lactation in the cow, as well as many avenues for future research on the bovine lactome.

Potential therapeutic applications of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) are a non-homogeneous population of plastic-adherent cells which were initially isolated from post-natal bone marrow. They have the capacity to differentiate to multiple mesodermal lineages including bone, cartilage and adipose tissue. In stringent culture conditions, MSCs can also be induced to differentiate into different cell types of endoderm and neuroectoderm lineages. To date, no specific marker identifies MSCs, although a number of cell surface antigens have been described which enrich for MSCs. Mesenchymal stromal cells possess a number of properties which have generated considerable interest in diverse cellular therapeutic applications. The capacity of MSCs to differentiate into multiple different cell lineages has seen them actively explored for tissue repair, particularly in cardiac, orthopaedic and neurological applications. A large body of data indicates that MSCs possess immunomodulatory properties. Mesenchymal stromal cells are immunosuppressive, interacting with T lymphocytes, antigen presenting cells, B lymphocytes, and natural killer cells. In addition, they are immunoprivileged, allowing transplantation across allogeneic barriers. These immunomodulatory properties have seen infusion of MSCs for the treatment of steroid refractory graft versus host disease, a life threatening complication of haemopoietic cell transplantation, with promising results. Furthermore, these immune functions may lead to roles in the facilitation of engraftment, induction of tolerance and as therapy in autoimmune disease.

Pannexin 3 is a novel target for Runx2, expressed by osteoblasts and mature growth plate chondrocytes

Pannexins are a class of chordate channel proteins identified by their homology to insect gap junction proteins. The pannexin family consists of three members, Panx1, Panx2, and Panx3, and the role each of these proteins plays in cellular processes is still under investigation. Previous reports of Panx3 expression indicate enrichment in skeletal tissues, so we have further investigated this distribution by surveying the developing mouse embryo with immunofluorescence. High levels of Panx3 were detected in intramembranous craniofacial flat bones, as well as long bones of the appendicular and axial skeleton. This distribution is the result of expression in both osteoblasts and hypertrophic chondrocytes. Furthermore, the Panx3 promoter contains putative binding sites for transcription factors involved in bone formation, and we show that the sequence between bases -275 and -283 is responsive to Runx2 activation. Taken together, our data suggests that Panx3 may serve an important role in bone development, and is a novel target for Runx2-dependent signaling.