Development and transplantation of a mineralized matrix formed by osteoblasts in vitro for bone regeneration

Harnessing the potential of hydrogels for advanced therapeutic applications: current achievements and future directions

The applications of hydrogels have expanded significantly due to their versatile, highly tunable properties and breakthroughs in biomaterial technologies. In this review, we cover the major achievements and the potential of hydrogels in therapeutic applications, focusing primarily on two areas: emerging cell-based therapies and promising non-cell therapeutic modalities. Within the context of cell therapy, we discuss the capacity of hydrogels to overcome the existing translational challenges faced by mainstream cell therapy paradigms, provide a detailed discussion on the advantages and principal design considerations of hydrogels for boosting the efficacy of cell therapy, as well as list specific examples of their applications in different disease scenarios. We then explore the potential of hydrogels in drug delivery, physical intervention therapies, and other non-cell therapeutic areas (e.g., bioadhesives, artificial tissues, and biosensors), emphasizing their utility beyond mere delivery vehicles. Additionally, we complement our discussion on the latest progress and challenges in the clinical application of hydrogels and outline future research directions, particularly in terms of integration with advanced biomanufacturing technologies. This review aims to present a comprehensive view and critical insights into the design and selection of hydrogels for both cell therapy and non-cell therapies, tailored to meet the therapeutic requirements of diverse diseases and situations.

Demethylbelamcandaquinone B (Dmcq B) Is the Active Compound of Marantodes pumilum var. alata (Blume) Kuntze with Osteoanabolic Activities

Phytoestrogens have attracted considerable attention for their potential in the prevention of postmenopausal osteoporosis. Recently, a phytoestrogen-rich herbal plant, Marantodes pumilum var. alata (Blume) Kuntze was reported to protect against bone loss in ovariectomized rat. However, the bioactive compound responsible for these effects and the underlying mechanism were not known. Through bioassay-guided isolation, demethylbelamcandaquinone B (Dmcq B) was isolated and identified from Marantodes pumilum var. alata leaf extract. In terms of its bone anabolic effects, Dmcq B was at par with 17β-estradiol (E2), in promoting the proliferation, differentiation and mineralization of osteoblast cells. Dmcq-B increased early differentiation markers, collagen content and enzymatic ALP activity. It was demonstrated to regulate BMP2 signaling pathway which further activated the transcription factor, osterix. Subsequently, Dmcq B was able to increase the osteocalcin expression which promoted matrix mineralization as evidenced by the increase in calcium deposition. Dmcq B also reduced the protein level of receptor activator of NF-κβ ligand (RANKL) and promoted osteoprotegerin (OPG) protein expression by osteoblast cells, therefore hastening bone formation rate by decreasing RANKL/OPG ratio. Moreover, Dmcq B was able to increase ER expression, postulating its phytoestrogen property. As the conclusion, Dmcq B is the active compound isolated from Marantodes pumilum var. alata leaves, regulating osteoanabolic activities potentially through the BMP2 and ER signaling pathways.

Mandibular Jaw Bone Regeneration Using Human Dental Cell-Seeded Tyrosine-Derived Polycarbonate Scaffolds

Here we present a new model for alveolar jaw bone regeneration, which uses human dental pulp cells (hDPCs) combined with tyrosine-derived polycarbonate polymer scaffolds [E1001(1k)] containing beta-tricalcium phosphate (β-TCP) [E1001(1k)/β-TCP]. E1001(1k)/β-TCP scaffolds (5 mm diameter × 1 mm thickness) were fabricated to fit a 5 mm rat mandibular ramus critical bone defect. Five experimental groups were examined in this study: (1) E1001(1k)/β-TCP scaffolds seeded with a high density of hDPCs, 5.0 × 10(5) hDPCs/scaffold (CH); (2) E1001(1k)/β-TCP scaffolds seeded with a lower density of hDPCs, 2.5 × 10(5) hDPCs/scaffold (CL); (3) acellular E1001(1k)/β-TCP scaffolds (SA); (4) acellular E1001(1k)/β-TCP scaffolds supplemented with 4 μg recombinant human bone morphogenetic protein-2 (BMP); and (5) empty defects (EDs). Replicate hDPC-seeded and acellular E1001(1k)/β-TCP scaffolds were cultured in vitro in osteogenic media for 1 week before implantation for 3 and 6 weeks. Live microcomputed tomography (μCT) imaging at 3 and 6 weeks postimplantation revealed robust bone regeneration in the BMP implant group. CH and CL groups exhibited similar uniformly distributed mineralized tissue coverage throughout the defects, but less than the BMP implants. In contrast, SA-treated defects exhibited sparse areas of mineralized tissue regeneration. The ED group exhibited slightly reduced defect size. Histological analyses revealed no indication of an immune response. In addition, robust expression of dentin and bone differentiation marker expression was observed in hDPC-seeded scaffolds, whereas, in contrast, BMP and SA implants exhibited only bone and not dentin differentiation marker expression. hDPCs were detected in 3-week but not in 6-week hDPC-seeded scaffold groups, indicating their survival for at least 3 weeks. Together, these results show that hDPC-seeded E1001(1k)/β-TCP scaffolds support the rapid regeneration of osteo-dentin-like mineralized jaw tissue, suggesting a promising new therapy for alveolar jaw bone repair and regeneration.

Cellular properties of the fermented microalgae Pavlova lutheri and its isolated active peptide in osteoblastic differentiation of MG‑63 cells

Fermented microalgae Pavlova lutheri (P. lutheri), the product of Hansenula polymorpha fermentation, exhibited an increase in alkaline phosphatase (ALP) activity in MG‑63 osteoblastic cells when compared to that of non‑fermented P. lutheri. Fractionation of the fermented P. lutheri resulted in identification of the active peptide [peptide of P. lutheri fermentation (PPLF)] with the sequence of EPQWFL. PPLF significantly increased ALP release from MG‑63 cells and mineralization in a dose‑dependent manner. In addition, the intracellular levels of ALP and osteocalcin (OCN) proteins were augmented by PPLF treatment. To identify the molecular mechanism underlying the effect of PPLF on osteoblastic differentiation, the phosphorylation levels of the mitogen‑activated protein kinases, p38, extracellular signal‑regulated kinases 1/2 and Jun, and nuclear factor (NF)‑κB were determined following PPLF treatment and the differences in expression were analyzed using p38 and NF‑κB selective inhibitors. These results concluded that PPLF from fermented P. lutheri induced osteoblastic differentiation by increasing ALP and OCN release in MG‑63 cells via the p38/p65 signaling pathway, indicating that PPLF supplement may be effective for therapeutic application in the field of bone health.

A 3D graphene coated bioglass scaffold for bone defect therapy based on the molecular targeting approach

Development of a cell-free scaffold with excellent mechanical properties and osteoconductivity is of significant need for bone regeneration. Herein, a reduced graphene oxide (rGO) functionalized hierarchical macro-mesoporous bioactive glass scaffold integrated with an osteoblast-specific aptamer is rationally designed to recruit and induce the rapid differentiation of osteoblasts for bone regeneration. This scaffold exhibits a macroporous structure with fully interconnected open pores and shows excellent mechanical properties with a Young's modulus of ∼80 kPa, which provides a strong scaffold to support the growth of osteoblasts and bone tissue regeneration. Furthermore, the scaffold displays good performance in accelerating osteoblast differentiation and promoting new bone formation. The osteoblast recruitment is achieved since the osteoblast-specific aptamer can specifically target osteoblasts with strong binding affinity. Micro-computed tomography and histological tests confirmed that the large bone defects fully heal with new plate-like-pattern bone appearing both peripherally and centrally, suggesting the outstanding bone regeneration performance of this cell-free and graphene functionalized scaffold. Considering the promising bioapplications of the graphene functionalized bioactive glass scaffold with osteoblast recruitment capacity, our strategy paves a way for the design of new bioactive functional materials for tissue regeneration and shows attractive prospects in targeted therapy.

Preparation and characterization of chitosan-natural nano hydroxyapatite-fucoidan nanocomposites for bone tissue engineering

Solid three dimensional (3D) composite scaffolds for bone tissue engineering were prepared using the freeze-drying method. The scaffolds were composed of chitosan, natural nano-hydroxyapatite (nHA) and fucoidan in the following combinations: chitosan, chitosan-fucoidan, chitosan-nHA, and chitosan-nHA-fucoidan. Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and optical microscopy (OM) were used to determine the physiochemical constituents and the morphology of the scaffolds. The addition of nHA into the chitosan-fucoidan composite scaffold reduced the water uptake and water retention. FT-IR analysis confirmed the presence of a phosphate group in the chitosan-nHA-fucoidan scaffold. This group is present because of the presence of nHA (isolated via alkaline hydrolysis from salmon fish bones). Microscopic results indicated that the dispersion of nHA and fucoidan in the chitosan matrix was uniform with a pore size of 10-400μm. The composite demonstrated a suitable micro architecture for cell growth and nutrient supplementation. This compatibility was further elucidated in vitro using periosteum-derived mesenchymal stem cells (PMSCs). The cells demonstrated high biocompatibility and excellent mineralization for the chitosan-nHA-fucoidan scaffold. We believe that a chitosan-nHA-fucoidan composite is a promising biomaterial for the scaffold that can be used for bone tissue regeneration.

In vitro evaluation of osteoprotegerin in chitosan for potential bone defect applications

BACKGROUND

The receptor activator of nuclear factor kappa-B (RANK)/RANK ligand/osteoprotegerin (OPG) system plays a critical role in bone remodelling by regulating osteoclast formation and activity. OPG has been used systemically in the treatment of bone diseases. In searching for more effective and safer treatment for bone diseases, we investigated newly formulated OPG-chitosan complexes, which is prepared as a local application for its osteogenic potential to remediate bone defects.

METHODS

We examined high, medium and low molecular weights of chitosan combined with OPG. The cytotoxicity of OPG in chitosan and its proliferation in vitro was evaluated using normal, human periodontal ligament (NHPL) fibroblasts in 2D and 3D cell culture. The cytotoxicity of these combinations was compared by measuring cell survival with a tetrazolium salt reduction (MTT) assay and AlamarBlue assay. The cellular morphological changes were observed under an inverted microscope. A propidium iodide and acridine orange double-staining assay was used to evaluate the morphology and quantify the viable and nonviable cells. The expression level of osteopontin and osteocalcin protein in treated normal human osteoblast cells was evaluated by using Western blot.

RESULTS

The results demonstrated that OPG in combination with chitosan was non-toxic, and OPG combined with low molecular weight chitosan has the most significant effect on NHPL fibroblasts and stimulates proliferation of cells over the period of treatment.

Dose-dependent inhibitory effects of zoledronic acid on osteoblast viability and function in vitro

Zoledronic acid (ZA), which is one of the most potent and efficacious bisphosphonates, has been commonly used in clinical practice for the treatment of various bone disorders. The extensive use of ZA has been associated with increasing occurrence of jaw complications, now known as bisphosphonate-associated osteonecrosis of the jaw (BRONJ). However, the mechanism underlying BRONJ remains to be fully elucidated. The aim of the present study was to investigate the effects of different concentrations of ZA on the MC3T3-E1 murine preosteoblast cell line cells and examine the possible pathogenesis of BRONJ. In the present study, the effect of ZA on the viability, apoptosis, differentiation and maturation of MC3T3-E1 cells, as well as its relevant molecular mechanism, were examined The results of a Cell Counting Kit 8 assay, a flow cytometric Annexin-V/propidium iodide assay and western blot analysis demonstrated that ZA exhibited a significant inhibition of cell viability and induction of apoptosis at concentrations >10 µM. Subsequently, the effect of ZA on cell differentiation at concentrations <1 µM were investigated. In this condition, ZA inhibited bone nodule formation and decreased the activity of alkaline phosphatase. The results of reverse transcription-quantitative polymerase chain reaction and western blot analyses indicated that ZA downregulated the expression levels of the marker genes and proteins associated with osteogenic differentiation. Further investigation revealed that the suppression of differentiation by ZA was associated with decreased expression of bone morphogenetic protein-2 (BMP-2) and downregulation of the phosphorylation levels in the downstream extracellular signal-regulated kinase 1/2 and p38 pathways. These adverse effects of ZA were observed to be concentration-dependent. The results from the present study suggested that ZA at higher concentrations induces cytotoxicity towards osteoblasts, and ZA at lower concentrations suppresses osteoblast differentiation by downregulation of BMP-2. These results assist in further understanding the mechanisms of BRONJ.

The in vitro and in vivo effects of the low molecular weight fucoidan on the bone osteogenic differentiation properties

Osteoporosis has been reported as a hidden death factor in aged people. So far, prevention and treatment therapies for osteoporosis only slow down the progress but do not treat the disease. Fucoidan has been recognized its roles in anti-tumor, anti-inflammatory, anti-coagulant and antiviral activities. To date, low molecular weight (LMW) fucoidan role in bone loss disease has been not determined yet. Therefore, this study aims to figure out potential effects of LMW fucoidan in osteoporosis in vitro and in vivo. LMW fucoidan was extracted from fresh Sargassum hemiphyllum showing a significant increase in 7F2 cell viability to 150.33 ± 6.50 % relative to normal fucoidan (130.12 ± 5.74 %). The expression of level BMP-2, ALP, osteocalcin significantly increased with 2.28 ± 0.06, 2.18 ± 0.12 and 2.06 ± 0.07 fold, respectively. The RT-PCR assay showed that LMW fucoidan increased mRNA expression of BMP-2, ALP, osteocalcin, COL I, BSP and osteonectin. Furthermore, the bone density and bone ash weight were considerably boosted by the oral administration of 280 mg/kg LMW fucoidan and 100 mg/kg calcium carbonate in C57BL/6J female aged mice. The present finding indicated that LMW fucoidan triggered osteogenic differentiation in vitro, and had an anabolic effect on bone mineralization in vivo. Dietary intake of LMW fucoidan from S. hemiphyllum suggested playing a role in the enhancement of bone loss with increasing age.

Emulating native periosteum cell population and subsequent paracrine factor production to promote tissue engineered periosteum-mediated allograft healing

Emulating autograft healing within the context of decellularized bone allografts has immediate clinical applications in the treatment of critical-sized bone defects. The periosteum, a thin, osteogenic tissue that surrounds bone, houses a heterogenous population of stem cells and osteoprogenitors. There is evidence that periosteum-cell derived paracrine factors, specifically vascular endothelial growth factor (VEGF) and bone morphogenetic protein 2 (BMP2), orchestrate autograft healing through host cell recruitment and subsequent tissue elaboration. In previous work, we demonstrated that the use of poly(ethylene glycol) (PEG) hydrogels as a tissue engineered (T.E.) periosteum to localize mesenchymal stem cells (MSCs) to the surface of decellularized bone enhances allograft healing and integration. Herein, we utilize a mixed population of 50:50 MSCs and osteoprogenitor cells to better mimic native periosteum cell population and paracrine factor production to further promote allograft healing. This mixed cell population was localized to the surface of decellularized allografts within degradable hydrogels and shown to expedite allograft healing. Specifically, bone callus formation and biomechanical graft-host integration are increased as compared to unmodified allografts. These results demonstrate the dual importance of periosteum-mediated paracrine factors orchestrating host cell recruitment as well as new bone formation while developing clinically translatable strategies for allograft healing and integration.

iNOS expression and osteocyte apoptosis in idiopathic, non-traumatic osteonecrosis

BACKGROUND AND PURPOSE

Non-traumatic osteonecrosis is a progressive disease with multiple etiologies. It affects younger individuals more and more, often leading to total hip arthroplasty. We investigated whether there is a correlation between inducible nitric oxide synthase (iNOS) expression and osteocyte apoptosis in non-traumatic osteonecrosis.

PATIENTS AND METHODS

We collected and studied 20 human idiopathic, non-traumatic osteonecrosis femoral heads. Subchondral bone samples in the non-sclerotic region (n = 30), collected from osteoarthritis patients, were used as controls. Spontaneously hypertensive rats were used as a model for osteonecrosis in the study. We used scanning electron microscopy, TUNEL assay, and immunohistochemical staining to study osteocyte changes and apoptosis.

RESULTS

The morphology of osteocytes in the areas close to the necrotic region changed and the number of apoptotic osteocytes increased in comparison with the same region in control groups. The expression of iNOS and cytochrome C in osteocytes increased while Bax expression was not detectable in osteonecrosis samples. Using spontaneously hypertensive rats, we found a positive correlation between iNOS expression and osteocyte apoptosis in the osteonecrotic region. iNOS inhibitor (aminoguanidine) added to the drinking water for 5 weeks reduced the production of iNOS and osteonecrosis compared to a control group without aminoguanidine.

INTERPRETATION

Our findings show that increased iNOS expression can lead to osteocyte apopotosis in idiopathic, non-traumatic osteonecrosis and that an iNOS inhibitor may prevent the progression of the disease.

Multidirectional effects of Sr-, Mg-, and Si-containing bioceramic coatings with high bonding strength on inflammation, osteoclastogenesis, and osteogenesis

Ideal coating materials for implants should be able to induce excellent osseointegration, which requires several important parameters, such as good bonding strength, limited inflammatory reaction, and balanced osteoclastogenesis and osteogenesis, to gain well-functioning coated implants with long-term life span after implantation. Bioactive elements, like Sr, Mg, and Si, have been found to play important roles in regulating the biological responses. It is of great interest to combine bioactive elements for developing bioactive coatings on Ti-6Al-4 V orthopedic implants to elicit multidirectional effects on the osseointegration. In this study, Sr-, Mg-, and Si-containing bioactive Sr2MgSi2O7 (SMS) ceramic coatings on Ti-6Al-4 V were successfully prepared by the plasma-spray coating method. The prepared SMS coatings have significantly higher bonding strength (∼37 MPa) than conventional pure hydroxyapatite (HA) coatings (mostly in the range of 15-25 MPa). It was also found that the prepared SMS coatings switch the macrophage phenotype into M2 extreme, inhibiting the inflammatory reaction via the inhibition of Wnt5A/Ca(2+) and Toll-like receptor (TLR) pathways of macrophages. In addition, the osteoclastic activities were also inhibited by SMS coatings. The expression of osteoclastogenesis-related genes (RANKL and MCSF) in bone-marrow-derived mesenchymal cells (BMSCs) with the involvement of macrophages was decreased, whereas OPG expression was enhanced on SMS coatings compared to HA coatings, indicating that SMS coatings also downregulated the osteoclastogenesis. However, the osteogenic differentiation of BMSCs with the involvement of macrophages was comparable between SMS and HA coatings. Therefore, the prepared SMS coatings showed multidirectional effects, such as improving bonding strength, reducing inflammatory reaction, and downregulating osteoclastic activities, but maintaining a comparable osteogenesis, as compared with HA coatings. The combination of bioactive elements of Sr, Mg, and Si into bioceramic coatings can be a promising method to develop bioactive implants with multifunctional properties for orthopedic application.

Primary human alveolar bone cells isolated from tissue samples acquired at periodontal surgeries exhibit sustained proliferation and retain osteogenic phenotype during in vitro expansion

OBJECTIVES

Bone tissue regeneration requires a source of viable, proliferative cells with osteogenic differentiation capacity. Periodontal surgeries represent an opportunity to procure small amounts of autologous tissues for primary cell isolation. Our objective was to assess the potential of human alveolar bone as a source of autologous osteogenic cells for tissue engineering and biomaterials and drug testing studies.

MATERIALS AND METHODS

Alveolar bone tissue was obtained from 37 patients undergoing routine periodontal surgery. Tissue harvesting and cell isolation procedures were optimized to isolate viable cells. Primary cells were subcultured and characterized with respect to their growth characteristics, gene expression of osteogenic markers, alkaline phosphatase activity and matrix mineralization, under osteogenic stimulation.

RESULTS

Alveolar bone cells were successfully isolated from 28 of the 30 samples harvested with bone forceps, and from 2 of the 5 samples obtained by bone drilling. The yield of cells in primary cultures was variable between the individual samples, but was not related to the site of tissue harvesting and the patient age. In 80% of samples (n = 5), the primary cells proliferated steadily for eight subsequent passages, reaching cumulative numbers over 10(10) cells. Analyses confirmed stable gene expression of alkaline phosphatase, osteopontin and osteocalcin in early and late cell passages. In osteogenic medium, the cells from late passages increased alkaline phosphatase activity and accumulated mineralized matrix, indicating a mature osteoblastic phenotype.

CONCLUSIONS

Primary alveolar bone cells exhibited robust proliferation and retained osteogenic phenotype during in vitro expansion, suggesting that they can be used as an autologous cell source for bone regenerative therapies and various in vitro studies.

Establishment and characterization of the Masquelet induced membrane technique in a rat femur critical-sized defect model

The Masquelet induced membrane technique for reconstructing large diaphyseal defects has been shown to be a promising clinical treatment, yet relatively little is known about the cellular, histological and biochemical make-up of these membranes and how they produce this positive clinical outcome. We compared cellular make-up, histological changes and growth factor expression in membranes induced around femur bone defects and in subcutaneous pockets at 2, 4 and 6 weeks after induction, and to the periosteum. We found that membranes formed around bone defects were similar to those formed in subcutaneous pockets; however, both were significantly different from periosteum with regard to structural characteristics, location of blood vessels and overall thickness. Membranes induced at the femur defect (at 2 weeks) and in periosteum contain mesenchymal stem cells (MSCs; STRO-1⁺ ) which were not found in membranes induced subcutaneously. BMP-2, TGFβ and VEGF were significantly elevated in membranes induced around femur defects in comparison to subcutaneously induced membranes, whereas SDF-1 was not detectable in membranes induced at either site. We found that osteogenic and neovascular activity had mostly subsided by 6 weeks in membranes formed at both sites. It was conclude that cellular composition and growth factor content in induced membranes depends on the location where the membrane is induced and differs from periosteum. Osteogenic and neovascular activity in the membranes is maximal between 2 and 4 weeks and subsides after 6. Based on this, better and quicker bone healing might be achieved if the PMMA cement were replaced with a bone graft earlier in the Masquelet technique. Copyright © 2013 John Wiley & Sons, Ltd.

The beneficial effect of Radix Dipsaci total saponins on bone metabolism in vitro and in vivo and the possible mechanisms of action

The purpose of this study is to investigate the anti-osteoporotic effects of Radix Dipsaci total saponins (RTS). We showed that RTS was able to improve bone properties by either an increase of osteoblastic activity or a decrease in osteoclastic activity.

INTRODUCTION

Radix Dipsaci has long been used as an anti-osteoporotic drug. The present study investigates the anti-osteoporotic effects of RTS.

METHODS

Three-month-old female rats were randomly assigned into a sham-operated group (sham) and five ovariectomy (OVX) subgroups, namely, OVX with vehicle (OVX), OVX with 17β-ethinylestradiol (E(2)), and OVX with graded doses of RTS (50, 100, or 200 mg/kg/d). RTS and E(2) were administered orally, daily from 1 week after OVX treatment for 4 months. Bone mass, turnover, and strength were evaluated by dual-energy X-ray absorptiometry, biochemical markers, and the three-point bending test. The trabecular bone microarchitecture was assessed by microCT. In vitro experiments were performed to determine the potential molecular mechanisms of the anti-osteoporotic effect of RTS.

RESULTS

RTS prevented the loss of bone mass induced by OVX. The preventive effect on bone loss was primarily indicated by decreasing levels of bone turnover markers and confirmed by the changes in urinary calcium and phosphorus excretion. The treatment also enhanced the biomechanical strength of bone and prevented the deterioration of trabecular bone microarchitecture. RTS induced MC3T3-E1 and primary osteoblastic cell maturation and differentiation and increased bone formation by increasing BMP-2 synthesis. In addition, RTS inhibited osteoclastogenesis through an increase in osteoprotegrin and a decrease in NF-kB ligand expression in vitro.

CONCLUSIONS

RTS treatment can effectively suppress the loss of bone mass induced by OVX and in vitro evidence suggests this could be through actions on both osteoblasts and osteoclasts.

Implantation of osteogenic differentiated donor mesenchymal stem cells causes recruitment of host cells

The interaction between host and donor cells is believed to play an important role in osteogenesis. However, it is still unclear how donor osteogenic cells behave and interact with host cells in vivo. The purpose of this study was to track the interactions between transplanted osteogenic cells and host cells during osteogenesis. In vitro migration assay was carried out to investigate the ability of osteogenic differentiated human mesenchymal stem cells (O-hMSCs) to recruit MSCs. At the in vivo level, O-hMSCs were implanted subcutaneously or into skull defects in severe combined immunodeficient (SCID) mice. New bone formation was observed by micro-CT and histological procedures. In situ hybridization (ISH) against human Alu sequences was performed to distinguish donor osteogenic cells from host cells. In vitro migration assay revealed an increased migration potential of MSCs by co-culturing with O-hMSCs. In agreement with the results of in vitro studies, ISH against human Alu sequences showed that host mouse MSCs migrated in large numbers into the transplantation site in response to O-hMSCs. Interestingly, host cells recruited by O-hMSCs were the major cell populations in newly formed bone tissues, indicating that O-hMSCs can trigger and initiate osteogenesis when transplanted in orthotopic sites. The observations from this study demonstrated that in vitro induced O-hMSCs were able to attract host MSCs in vivo and were involved in osteogenesis together with host cells, which may be of importance for bone tissue-engineering applications.

Osteoblast-like cell response to calcium phosphate coating chemistry and morphology on etched silicon surfaces

Being able to control the behaviour of osteoblast-like cells on a surface may provide a genuine insight into the material surface characteristics and help in creating a successful coating/cell interface. The possibility of creating a micro-environment that can induce proliferation, differentiation and mineralisation of bone cells in vitro, by successfully combining both chemistry and topography of a micro-fabricated substrate is an area that requires a multi-disciplinary approach. Utilising sputter deposition, a process that lends itself to high processability, in conjunction with photolithography allowing for the creation of highly repeatable etched surfaces, we aim to provide a successful combination of chemistry and topography. Correlating the substrate conditions with resultant osteoblast biological function and activity can ultimately be used with a view to modulating the behavior of osteoblast-like cells in vitro.

Osteogenic effect of low intensity pulsed ultrasound on rat adipose-derived stem cells in vitro

The osteogenic in vitro effect of low intensity pulsed ultrasound (LIPUS) on SD rat adipose-derived stem cells (ADSCs) was investigated. Rat ADSCs underwent LIPUS (intensity=100 mW/cm(2)) or sham exposure for 8 min per treatment once everyday in vitro, and then the alkaline phosphatase (ALP) activity and mineralized nodule formation were assessed to evaluate the osteogenic effect of LIPUS on ADSCs. To further explore the underlying mechanism, the osteogenic-related gene mRNA expression was determined by using reverse transcriptase-polymerase chain reaction (RT-PCR) at 1st, 3rd, 5th, 7th day after exposure repectively. Westen blot was used to evaluate the protein expression levels of two osteogenic differentiation associated genes at 7th and 14th day repectively. It was found that ALP activity was increased after LIPUS exposure and LIPUS resulted in mineralized nodule formation of ADSCs in vitro. LIPUS-treated ADSCs displayed higher mRNA expression levels of runt-related transcription factor 2 (Runx2), osteocalcin (OCN), ALP and bone sialoprotein (BSP) genes than controls, and the protein levels of Runx2 and BSP were also increased. The results suggested that LIPUS may induce the osteogenic differentiation of ADSCs in vitro.

Asperosaponin VI, a saponin component from Dipsacus asper wall, induces osteoblast differentiation through bone morphogenetic protein-2/p38 and extracellular signal-regulated kinase 1/2 pathway

Osteoporosis is a reduction in skeletal mass because of the loss of osteoblastic activity or an increase in osteoclastic activity. The survival of osteoblast cells plays a crucial role in the development of osteoporosis. Asperosaponin VI (ASA VI) is a kind of saponin in the medicinal herb Dipsacus asper Wall which has long been used as an antiosteoporosis drug. The assay of cell proliferation, alkaline phosphatase (ALP) activity and measurement of mineralized matrix, showed that ASA VI exhibited a significant induction of proliferation, differentiation and mineralization in MC3T3-E1 and primary osteoblastic cells. Induction of differentiation by ASA VI was associated with increased bone morphogenetic protein-2 (BMP-2), indicating that BMP-2 is essential in ASA VI to mediate osteoblast maturation and differentiation. In addition, ASA VI may induce differentiation by increasing the activity of p38 and ERK1/2. In conclusion, ASA VI may induce osteoblast maturation and differentiation, and then increase bone formation via increasing BMP-2 synthesis, and activating p38 and ERK1/2.

Psoralen stimulates osteoblast differentiation through activation of BMP signaling

Osteoporosis is a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture. In order to improve the treatment of osteoporosis, identification of anabolic and orally available agents with minimal side effects is highly desirable. Psoralen is a coumarin-like derivative extracted from Chinese herbs, which have been used to treat bone diseases for thousands of years. However, the role of Psoralen in osteoblast function and the underlying molecular mechanisms remain poorly understood. In this study, we found that Psoralen promoted osteoblast differentiation in primary mouse calvarial osteoblasts in a dose-dependent manner, demonstrated by up-regulation of expressions of osteoblast-specific marker genes including type I collagen, osteocalcin and bone sialoprotein and enhancement of alkaline phosphatase activity. We further demonstrated that Psoralen up-regulated the expression of Bmp2 and Bmp4 genes, increased the protein level of phospho-Smad1/5/8, and activated BMP reporter (12xSBE-OC-Luc) activity in a dose-dependent manner, as well as enhanced the expression of Osx, the direct target gene of BMP signaling. Deletion of the Bmp2 and Bmp4 genes abolished the stimulatory effect of Psoralen on the expression of osteoblast marker genes, such as Col1, Alp, Oc and Bsp. Our results suggest that Psoralen acts through the activation of BMP signaling to promote osteoblast differentiation and demonstrate that Psoralen could be a potential anabolic agent to treat patients with bone loss-associated diseases such as osteoporosis.

Cell-derived matrix enhances osteogenic properties of hydroxyapatite

The study aimed to evaluate osteogenic properties of hydroxyapatite (HA) scaffold combined with extracellular matrix (ECM) derived in vitro from rat primary calvarial osteoblasts or dermal fibroblasts. The cellular viability, and the ECM deposited onto synthetic HA microparticles were assessed by MTT, Glycosaminoglycan, and Hydroxyproline assays as well as immunohistochemistry and scanning electron microscopy after 21 days of culture. The decellularized HA-ECM constructs were implanted in critical-sized calvarial defects of Sprague-Dawley rats, followed by bone repair and local inflammatory response assessments by histomorphometry and immunohistochemistry at 12 weeks postoperatively. We demonstrated that HA supported cellular adhesion, growth, and ECM production in vitro, and the HA-ECM constructs significantly enhanced calvarial bone repair (p<0.05, Mann-Whitney U-test), compared with HA alone, despite the significantly increased number of CD68+ macrophages, and foreign body giant cells (p<0.05, Mann-Whitney U-test). Selective accumulation of bone sialoprotein, osteopontin, and periostin was observed at the tissue-HA interfaces. In conclusion, in vitro-derived ECM mimics the native bone matrix, enhances the osteogenic properties of the HA microparticles, and might modulate the local inflammatory response in a bone repair-favorable way. Our findings highlight the ability to produce functional HA-ECM constructs for bone tissue engineering applications.

Icariin isolated from Epimedium pubescens regulates osteoblasts anabolism through BMP-2, SMAD4, and Cbfa1 expression

Epimedii herba is one of the most frequently used herbs in formulas prescribed for the treatment of osteoporosis in China. The main active flavonoid glucoside extracted from Epimedium pubescens is Icariin, which has been reported to enhance bone healing and reduce osteoporosis occurrence. However, the detailed molecular mechanisms remain unclear. In this present study, we examine the molecular mechanisms of icariin by using primary osteoblast cell cultures obtained from adult mice. The osteoblast cells were harvested from 8-month old female Imprinting Control Region (ICR) mice. The effects of icariin stimulation on the proliferation, differentiation and maturation of osteoblasts were examined. The production of nitric oxide (NO) and caspase-3 were analyzed, along with the gene expressions of bone morphogenetic protein-2 (BMP-2), SMAD4, Cbfa1/Runx2, OPG, and RANKL. The viability of the osteoblasts reached its maximum at 10(-8)M icariin. At this concentration, icariin increased the proliferation and matrix mineralization of osteoblasts and promoted NO synthesis. With icariin treatment, the BMP-2, SMAD4, Cbfa1/Runx2, and OPG gene expressions were up-regulated; the RANKL gene expression was however down-regulated. Concurrent treatment involving the BMP antagonist (Noggin) or the NOS inhibitor (L-NAME) diminished the icariin-induced cell proliferation, ALP activity, NO production, as well as the BMP-2, SMAD4, Cbfa1/Runx2, OPG, RANKL gene expressions. In this study, we demonstrate that in vitro icariin is a bone anabolic agent that may exert its osteogenic effects through the induction of BMP-2 and NO synthesis, subsequently regulating Cbfa1/Runx2, OPG, and RANKL gene expressions. This effect may contribute to its action on the induction of osteoblasts proliferation and differentiation, resulting in bone formation.

Enhancing in vivo vascularized bone formation by cobalt chloride-treated bone marrow stromal cells in a tissue engineered periosteum model

The periosteum plays an indispensable role in both bone formation and bone defect healing. In this study we constructed an artificial in vitro periosteum by incorporating osteogenic differentiated bone marrow stromal cells (BMSCs) and cobalt chloride (CoCl(2))-treated BMSCs. The engineered periostea were implanted both subcutaneously and into skull bone defects in SCID mice to investigate ectopic and orthotopic osteogenesis and vascularization. After two weeks in subcutaneous and four weeks in bone defect areas, the implanted constructs were assessed for ectopic and orthotopic osteogenesis and vascularization by micro-CT, histomorphometrical and immunohistochemical methods. The results showed that CoCl(2) pre-treated BMSCs induced higher degree of vascularization and enhanced osteogenesis within the implants in both ectopic and orthotopic areas. This study provided a novel approach using BMSCs sourced from the same patient for both osteogenic and pro-angiogenic purposes in constructing tissue engineered periosteum to enhance vascularized osteogenesis.

Enhancement of bone morphogenetic protein-2 expression and bone formation by coumarin derivatives via p38 and ERK-dependent pathway in osteoblasts

Osteoporosis is a reduction in skeletal mass due to an imbalance between bone resorption and bone formation. Bone morphogenetic protein (BMP) plays important roles in osteoblastic differentiation and bone formation. Therefore, components involved in BMP activation are good targets for the development of anti-osteoporosis drugs. In this study, imperatorin and bergapten, two coumarin derivatives, were shown to enhance alkaline phosphatase (ALP) activity, type I collagen synthesis and bone nodule formation in primary cultured osteoblasts. Imperatorin and bergapten increased mRNA levels of BMP-2 using quantitative RT-PCR, whereas the BMP-2 antagonist noggin attenuated the increase of ALP activity induced by imperatorin and bergapten, indicating that BMP-2 expression is required for the action of imperatorin and bergapten in osteoblastic maturation. Both imperatorin and bergapten enhanced the phosphorylation of SMAD (transcription factors activated by TGF-beta) 1/5/8, p38 and extracellular signal-regulated protein (ERK). Pretreatment of osteoblasts with p38 inhibitor (SB203580) or mitogen-activated protein kinase inhibitor (PD98059) or transfected with dominant negative mutant of p38 or ERK antagonized the elevation of BMP-2 expression and ALP activity induced by imperatorin and bergapten. Local administration of imperatorin or bergapten into the metaphysis of the tibia via the implantation of a needle cannula significantly increased the BMP-2 immunostaining and bone volume of secondary spongiosa in tibia. Taken together, our results provide evidence that coumarin derivatives increase BMP-2 expression and enhance bone formation in rat via the p38 and ERK-dependent signaling pathway.

Myricetin induces human osteoblast differentiation through bone morphogenetic protein-2/p38 mitogen-activated protein kinase pathway

Myricetin (3,3',4',5,5',7-hexahydroxyflavone), a flavonoid compound, is present in vegetables and fruits. By means of alkaline phosphatase (ALP) activity, osteocalcin, and type I collagen enzyme-linked immunosorbent assay (ELISA), we have shown that myricetin exhibits a significant induction of differentiation in MG-63 and hFOB human osteoblasts. Alkaline phosphatase and osteocalcin are phenotypic markers for early-stage differentiated osteoblasts and terminally differentiated osteoblasts, respectively. Our results indicate that myricetin stimulates osteoblast differentiation at various stages, from maturation to terminally differentiated osteoblasts. Induction of differentiation by myricetin is associated with increased bone morphogenetic protein-2 (BMP-2) production. The BMP-2 antagonist noggin blocked myricetin-mediated ALP activity and osteocalcin secretion enhancement, indicating that BMP-2 production is required in myricetin-mediated osteoblast maturation and differentiation. Induction of differentiation by myricetin is associated with increased activation of SMAD1/5/8 and p38 mitogen-activated protein kinases. Cotreatment of p38 inhibitor SB203580 inhibited myricetin-mediated ALP upregulation and osteocalcin production. In conclusion, myricetin increased BMP-2 synthesis, and subsequently activated SMAD1/5/8 and p38 MAPK, and this effect may contribute to its action on the induction of osteoblast maturation and differentiation, followed by an increase of bone mass.

Piceatannol stimulates osteoblast differentiation that may be mediated by increased bone morphogenetic protein-2 production

Piceatannol (3,3',4,5'-tetrahydroxy-trans-stilbene) is a polyphenol present in grapes and wine. By means of alkaline phosphatase activity and osteocalcin enzyme-linked immunosorbent assay (ELISA), we have shown that piceatannol exhibits a significant induction of differentiation in immortalized fetal osteoblasts (hFOB), and osteosarcoma cells (MG-63). Alkaline phosphatase and osteocalcin are phenotypic markers for early-stage differentiated osteoblasts and terminally differentiated osteoblasts, respectively, our results indicate that piceatannol stimulate osteoblast differentiation at various stages (from maturation to terminally differentiated osteoblasts). Induction of differentiation by piceatannol was associated with increased bone morphogenetic protein-2 (BMP-2) production. Addition of purified BMP-2 protein did not increase the upregulation of alkaline phosphatase activity and osteocalcin secretion by piceatannol, whereas the BMP-2 antagonist noggin blocked piceatannol and BMP-2-mediated alkaline phosphatase activity, and osteocalcin secretion enhancement, indicating that BMP-2 production is required in piceatannol-mediated osteoblast maturation and differentiation. In conclusion, piceatannol increased BMP-2 synthesis, and this effect may contribute to its action on the induction of osteoblasts maturation and differentiation, followed by an increase of bone mass. Decreases in new bone formation, followed by estrogen deficiency or various pathologic factors, may contribute to the mechanisms involved in postmenopausal osteoporosis.

Stromal-epithelial interaction in prostate cancer progression

Cancer is not a single-cell disease, and its existence and behavior are constantly modulated by the host. Cancer gene expression and genetics are also highly dynamic and are regulated epigenetically by the host through gene-environment interaction. In this article, we describe the molecular pathways leading to an unusual property of cancer cells: the ability to mimic the host microenvironment and, in particular, the characteristics of osteomimicry and vasculogenic mimicry, which are likely to be regulated by soluble and insoluble factors in the tumor-adjacent microenvironment. We also discuss the importance of host inflammatory and stem cells that contribute to the growth and survival of cancer cells. By understanding the salient features of cancer-host interaction, novel therapeutics might be developed to target the cancer and its host in the treatment of lethal prostate cancer metastases.

Alveolar bone osteoblast differentiation and Runx2/Cbfa1 expression

Alveolar bone cells have a unique origin and functionality, but may resemble skeletal osteoblasts. Osteoblast differentiation and gene expression are regulated by the Runx2/Cbfa1 transcription factor. However, most studies on Runx2/Cbfa1 expression have been on rodent cells and the few studies on human osteoblasts have had differing results. The purpose of this study was to characterize Runx2/Cbfa1 expression in primary cell cultures derived from human alveolar bone. An alveolar bone chip was incubated in alpha-minimum essential medium (alpha-MEM) supplemented with fetal calf serum (10% FCS). Explant cultures were harvested after 3-4 weeks of outgrowth and grown in alpha-MEM with FCS. This media was supplemented with ascorbate, beta-glycerophosphate and dexamethasone to promote osteoblast differentiation over 14 days. RT-PCR analysis and Western blots showed a rapid increase in Runx2/Cbfa1 mRNA (2.1-fold) and protein (2.3-fold) levels in 3 days, followed by a slight decline. There was also a rapid increase in bone sialoprotein expression (2.9-fold) in 3 days, followed by a further increase (3.6-fold) at 14 days. There was a slower increase in alkaline phosphatase expression (1.6-fold) and activity (3.1-fold) over 7 days, followed by a gradual decline. In contrast, collagen mRNA levels showed little change over 14 days. These findings attest to the osteogenic potential of primary cell cultures derived from human alveolar bone. Osteoblastic differentiation in human alveolar bone involves an increase in Runx2/Cbfa1 expression that may be an important component of the differentiation process.

Bone morphogenetic protein-2 and -4 (BMP-2 and -4) mediates fraxetin-induced maturation and differentiation in human osteoblast-like cell lines

Fraxetin (7,8-dihydroxy-6-methoxy coumarin), a coumarin derivative, was investigated for its effects on differentiation of osteoblasts. By means of alkaline phosphatase (ALP) activity and osteocalcin ELISA assay, we have shown that fraxetin exhibits a significant induction of differentiation in two human osteoblast-like cell lines, MG-63 and hFOB. Alkaline phosphatase and osteocalcin are phenotypic markers for early-stage differentiated osteoblasts and terminally differentiated osteoblasts, respectively. Our results indicated that fraxetin stimulated osteoblast differentiation at various stages (from osteoprogenitors to terminally differentiated osteoblasts). Induction of differentiation by fraxetin was associated with increased bone morphogenetic protein-2 (BMP-2) and BMP-4 productions. Addition of purified BMP-2 and BMP-4 proteins did not increase the upregulation of ALP activity and osteocalcin secretion by fraxetin, whereas the BMPs antagonist noggin blocked both fraxetin and BMP-2 and BMP-4 mediated ALP activity and osteocalcin secretion enhancement, indicating that BMP-2 and BMP-4 productions are required in fraxetin-mediated osteoblast maturation and differentiation. These findings are novel and may be important in the treatment and prevention of osteoporosis.

A comparative qualitative histological analysis of tissue-engineered bone using bone marrow mesenchymal stem cells, alveolar bone cells, and periosteal cells

For tissue-engineered bone formation, autogenous osteogenic cells are of paramount importance for successful bone formation. In order to investigate the donor cell-related differences in tissue-engineered bone, cultured bone marrow mesenchymal stem cells, cultured alveolar bone cells, and cultured periosteal cells were examined for their in vivo potential to form bone. These cells were isolated from dogs, expanded in vitro, mixed with autologous fibrin glue and BMP-2, and then injected into the subcutaneous space on the dorsum of nude mice. Bone formation was evaluated at 12 weeks. Histomorphometric analysis demonstrated that the subcutaneous nodules formed in nude mice contained 26.9% newly formed bone when using the bone marrow mesenchymal stem cells, 41.1% newly formed bone when using the alveolar bone cells, and 58.2% newly formed bone when using the periosteal cells. The results suggest that periosteal cells are the best choice for enhancing bone formation in tissue engineering of bone regeneration.

Osthole-mediated cell differentiation through bone morphogenetic protein-2/p38 and extracellular signal-regulated kinase 1/2 pathway in human osteoblast cells

The survival of osteoblast cells is one of the determinants of the development of osteoporosis in patients. Osthole (7-methoxy-8-isopentenoxycoumarin) is a coumarin derivative present in many medicinal plants. By means of alkaline phosphatase (ALP) activity, osteocalcin, osteopontin, and type I collagen, enzyme-linked immunosorbent assay, we have shown that osthole exhibits a significant induction of differentiation in two human osteoblast-like cell lines, MG-63 and hFOB. Induction of differentiation by osthole was associated with increased bone morphogenetic protein (BMP)-2 production and the activations of SMAD1/5/8 and p38 and extracellular signal-regulated kinase (ERK) 1/2 kinases. Addition of purified BMP-2 protein did not increase the up-regulation of ALP activity and osteocalcin by osthole, whereas the BMP-2 antagonist noggin blocked both osthole and BMP-2-mediated ALP activity enhancement, indicating that BMP-2 production is required in osthole-mediated osteoblast maturation. Pretreatment of osteoblast cells with noggin abrogated p38 activation but only partially decreased ERK1/2 activation, suggesting that BMP-2 signaling is required in p38 activation and is partially involved in ERK1/2 activation in osthole-treated osteoblast cells. Cotreatment of p38 inhibitor SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole] or p38 small interfering RNA (siRNA) expression inhibited osthole-mediated activation of ALP but only slightly affected osteocalcin production. In contrast, the production of osteocalcin induced by osthole was inhibited by the mitogen-activated protein kinase kinase inhibitor PD98059 (2'-amino-3'-methoxyflavone) or by expression of an ERK2 siRNA. These data suggest that BMP-2/p38 pathway links to the early phase, whereas ERK1/2 pathway is associated with the later phase in osthole-mediated differentiation of osteoblast cells. In this study, we demonstrate that osthole is a promising agent for treating osteoporosis.

Cement lines of secondary osteons in human bone are not mineral-deficient: New data in a historical perspective

Using qualitative backscattered electron (BSE) imaging and quantitative energy dispersive X-ray (EDX) spectroscopy, some investigators have concluded that cement (reversal) lines located at the periphery of secondary osteons are poorly mineralized viscous interfaces with respect to surrounding bone. This conclusion contradicts historical observations of apparent highly mineralized (or collagen-deficient) cement lines in microradiographs. Such conclusions, however, may stem from unrecognized artifacts that can occur during scanning electron microscopy. These include specimen degradation due to high-energy beams and the sampling of electron interaction volumes that extend beyond target locations during EDX analysis. This study used quantitative BSE imaging and EDX analysis, each with relatively lower-energy beams, to test the hypothesis that cement lines are poorly mineralized. Undemineralized adult human femoral diaphyses (n = 8) and radial diaphyses (n = 5) were sectioned transversely, embedded in polymethyl methacrylate, and imaged in a scanning electron microscope for BSE and EDX analyses. Unembedded samples were also evaluated. Additional thin embedded samples were stained and evaluated with light microscopy and correlated BSE imaging. BSE analyses showed the consistent presence of a bright line (higher atomic number) coincident with the classical location and description of the cement line. This may represent relative hypermineralization or, alternatively, collagen deficiency with respect to surrounding bone. EDX analyses of cement lines showed either higher Ca content or equivalent Ca content when compared to distant osteonal and interstitial bone. These data reject the hypothesis that cement lines of secondary osteons are poorly mineralized.