Progressive changes in the protein composition of the nuclear matrix during rat osteoblast differentiation

Osteopathy in Complex Lymphatic Anomalies

Complex Lymphatic Anomalies (CLA) are lymphatic malformations with idiopathic bone and soft tissue involvement. The extent of the abnormal lymphatic presentation and boney invasion varies between subtypes of CLA. The etiology of these diseases has proven to be extremely elusive due to their rarity and irregular progression. In this review, we compiled literature on each of the four primary CLA subtypes and discuss their clinical presentation, lymphatic invasion, osseous profile, and regulatory pathways associated with abnormal bone loss caused by the lymphatic invasion. We highlight key proliferation and differentiation pathways shared between lymphatics and bone and how these systems may interact with each other to stimulate lymphangiogenesis and cause bone loss.

Comparison of Hydroxyapatite/Poly(lactide-co-glycolide) and Hydroxyapatite/Polyethyleneimine Composite Scaffolds in Bone Regeneration of Swine Mandibular Critical Size Defects: In Vivo Study

Reconstruction of jaw bone defects present a significant problem because of specific aesthetic and functional requirements. Although widely used, the transplantation of standard autograft and allograft materials is still associated with significant constraints. Composite scaffolds, combining advantages of biodegradable polymers with bioceramics, have potential to overcome limitations of standard grafts. Polyethyleneimine could be an interesting novel biocompatible polymer for scaffold construction due to its biocompatibility and chemical structure. To date, there have been no in vivo studies assessing biological properties of hydroxyapatite bioceramics scaffold modified with polyethyleneimine. The aim of this study was to evaluate in vivo effects of composite scaffolds of hydroxyapatite ceramics and poly(lactide-co-glycolide) and novel polyethyleneimine on bone repair in swine’s mandibular defects, and to compare them to conventional bone allograft (BioOss). Scaffolds were prepared using the method of polymer foam template in three steps. Pigs, 3 months old, were used and defects were made in the canine, premolar, and molar area of their mandibles. Four months following the surgical procedure, the bone was analyzed using radiological, histological, and gene expression techniques. Hydroxyapatite ceramics/polyethyleneimine composite scaffold demonstrated improved biological behavior compared to conventional allograft in treatment of swine’s mandibular defects, in terms of bone density and bone tissue histological characteristics.

Implantable electrical stimulation bioreactor with liquid crystal polymer-based electrodes for enhanced bone regeneration at mandibular large defects in rabbit

The osseous regeneration of large bone defects is still a major clinical challenge in maxillofacial and orthopedic surgery. Previous studies demonstrated that biphasic electrical stimulation (ES) stimulates bone formation; however, polyimide electrode should be removed after regeneration. This study presents an implantable electrical stimulation bioreactor with electrodes based on liquid crystal polymer (LCP), which can be permanently implanted due to excellent biocompatibility to bone tissue. The bioreactor was implanted into a critical-sized bone defect and subjected to ES for one week, where bone regeneration was evaluated four weeks after surgery using micro-CT. The effect of ES via the bioreactor was compared with a sham control group and a positive control group that received recombinant human bone morphogenetic protein (rhBMP)-2 (20 μg). New bone volume per tissue volume (BV/TV) in the ES and rhBMP-2 groups increased to 132% (p < 0.05) and 174% (p < 0.01), respectively, compared to that in the sham control group. In the histological evaluation, there was no inflammation within the bone defects and adjacent to LCP in all the groups. This study showed that the ES bioreactor with LCP electrodes could enhance bone regeneration at large bone defects, where LCP can act as a mechanically resistant outer box without inflammation. Graphical abstract To enhance bone regeneration, a bioreactor comprising collagen sponge and liquid crystal polymer-based electrode was implanted in the bone defect. Within the defect, electrical current pulses having biphasic waveform were applied from the implanted bioreactor.

Effect of Functionally-Graded Calcium Titanate Film, Prepared by Metal-Organic Chemical Vapor Deposition, on Titanium Implant

Calcium Titanate (CaTiO3) has been introduced as an attractive biomaterial for the enhancement of calcium phosphate deposition in vivo and in vitro. We hypothesized that CaTiO3 directly coated on titanium (Ti) by metal-organic chemical vapor deposition (MOCVD) could be a suitable candidate for biocompatible coatings for medical devices, particularly dental implants. To prove this hypothesis, surface characterization, cell culture, and animal study were completed in this study. The result of this study showed that CTO 800, a CaTiO3 film prepared by heating at 800 °C, had a high hydrophilic surface. Mouse bone marrow stromal ST-2 cells cultured on substrates and CTO 800 exhibited cell differentiation, represented by alkaline phosphatase activity, compared with cells cultured on non-coated Ti and CTO 700 (a CaTiO3 film prepared by heating at 700 °C). The push-in test value of CTO 800, a parameter that indicates the degree of osseointegration, was significantly higher than that of Ti. Calcium titanate coated on Ti by MOCVD has the potential to accelerate the process of osseointegration; thus, our results support the use of CaTiO3 coating for biocompatible biomaterial for medical applications, particularly dental implants.

Human Mesenchymal Stem Cells Differentiation Regulated by Hydroxyapatite Content within Chitosan-Based Scaffolds under Perfusion Conditions

The extensive need for hard tissue substituent greatly motivates development of suitable allogeneic grafts for therapeutic recreation. Different calcium phosphate phases have been accepted as scaffold's components with positive influence on osteoinduction and differentiation of human mesenchymal stem cells, in terms of their higher fraction within the graft. Nevertheless, the creation of unlimited nutrients diffusion through newly formed grafts is of great importance. The media flow accomplished by perfusion forces can provide physicochemical, and also, biomechanical stimuli for three-dimensional bone-construct growth. In the present study, the influence of a different scaffold's composition on the human mesenchymal stem cells (hMSCs) differentiation performed in a U-CUP bioreactor under perfusion conditioning was investigated. The histological and immunohistochemical analysis of cultured bony tissues, and the evaluation of osteogenic genes' expression indicate that the lower fraction of in situ formed hydroxyapatite in the range of 10⁻30% within chitosan scaffold could be preferable for bone-construct development.

Modified silk fibroin scaffolds with collagen/decellularized pulp for bone tissue engineering in cleft palate: Morphological structures and biofunctionalities

Cleft palate is a congenital malformation that generates a maxillofacial bone defect around the mouth area. The creation of performance scaffolds for bone tissue engineering in cleft palate is an issue that was proposed in this research. Because of its good biocompatibility, high stability, and non-toxicity, silk fibroin was selected as the scaffold of choice in this research. Silk fibroin scaffolds were prepared by freeze-drying before immerging in a solution of collagen, decellularized pulp, and collagen/decellularized pulp. Then, the immersed scaffolds were freeze-dried. Structural organization in solution was observed by Atomic Force Microscope (AFM). The molecular organization of the solutions and crystal structure of the scaffolds were characterized by Fourier transform infrared (FT-IR) and X-ray diffraction (XRD), respectively. The weight increase of the modified scaffolds and the pore size were determined. The morphology was observed by a scanning electron microscope (SEM). Mechanical properties were tested. Biofunctionalities were considered by seeding osteoblasts in silk fibroin scaffolds before analysis of the cell proliferation, viability, total protein assay, and histological analysis. The results demonstrated that dendrite structure of the fibrils occurred in those solutions. Molecular organization of the components in solution arranged themselves into an irregular structure. The fibrils were deposited in the pores of the modified silk fibroin scaffolds. The modified scaffolds showed a beta-sheet structure. The morphological structure affected the mechanical properties of the silk fibroin scaffolds with and without modification. Following assessment of the biofunctionalities, the modified silk fibroin scaffolds could induce cell proliferation, viability, and total protein particularly in modified silk fibroin with collagen/decellularized pulp. Furthermore, the histological analysis indicated that the cells could adhere in modified silk fibroin scaffolds. Finally, it can be deduced that modified silk fibroin scaffolds with collagen/decellularized pulp had the performance for bone tissue engineering and a promise for cleft palate treatment.

Subnuclear domain proteins in cancer cells support the functions of RUNX2 in the DNA damage response

Cancer cells exhibit modifications in nuclear architecture and transcriptional control. Tumor growth and metastasis are supported by RUNX family transcriptional scaffolding proteins, which mediate the assembly of nuclear-matrix-associated gene-regulatory hubs. We used proteomic analysis to identify RUNX2-dependent protein-protein interactions associated with the nuclear matrix in bone, breast and prostate tumor cell types and found that RUNX2 interacts with three distinct proteins that respond to DNA damage - RUVBL2, INTS3 and BAZ1B. Subnuclear foci containing these proteins change in intensity or number following UV irradiation. Furthermore, RUNX2, INTS3 and BAZ1B form UV-responsive complexes with the serine-139-phosphorylated isoform of H2AX (γH2AX). UV irradiation increases the interaction of BAZ1B with γH2AX and decreases histone H3 lysine 9 acetylation levels, which mark accessible chromatin. RUNX2 depletion prevents the BAZ1B-γH2AX interaction and attenuates loss of H3K9 and H3K56 acetylation. Our data are consistent with a model in which RUNX2 forms functional complexes with BAZ1B, RUVBL2 and INTS3 to mount an integrated response to DNA damage. This proposed cytoprotective function for RUNX2 in cancer cells might clarify its expression in chemotherapy-resistant and/or metastatic tumors.

Multipotent adult progenitor cell-loaded demineralized bone matrix for bone tissue engineering

Multipotent adult progenitor cells (MAPCs) from bone marrow have been shown to be capable of forming bone, cartilage and other connective tissues. In addition, MAPCs differentiate into lineages that are different from their germ layers of origin. Previous studies showed the ability of MAPCs to improve cardiac function and control allogenic-reactive responses associated with acute graft versus host disease. In the current study, we evaluated the ability of MAPCs to produce bone matrix on demineralized bone allograft substrates. Specifically, MAPCs expressed alkaline phosphatase, produced extracellular matrix proteins and deposited calcium-containing mineral on demineralized bone matrices. Furthermore, the addition of MAPCs on demineralized bone matrix (DBM) scaffolds enhanced osteoinductivity of the carrier in a rat ectopic pouch model. These results demonstrated the potential of MAPCs as a new approach for bone repair in tissue-engineering applications.

Transposable element 'roo' attaches to nuclear matrix of the Drosophila melanogaster

The genome of eukaryotes is organized into structural units of chromatin loops. This higher order organization is supported by a nuclear skeleton called the nuclear matrix. The genomic DNA associated with the nuclear matrix is called the matrix associated region (MAR). Only a few genome-wide screens have been attempted, although many studies have characterized locusspecific MAR DNA sequences. In this study, a MAR DNA library was prepared from the Drosophila melanogaster Meigen (Diptera: Drosophilidae) genome. One of the sequences identified as a MAR was from a long terminal repeat region of 'roo' retrotransposon (roo MAR). Sequence analysis of roo MAR showed its distribution across the D. melanogaster genome. roo MAR also showed high sequence similarity with a previously identified MAR in Drosophila, namely the 'gypsy' retrotransposon. Analysis of the genes flanking roo MAR insertions in the Drosophila genome showed that genes were co-ordinately expressed. The results from the present study in D. melanogaster suggest this sequence plays an important role in genome organization and function. The findings point to an evolutionary role of retrotransposons in shaping the genomic architecture of eukaryotes.

Novel oxysterols activate the Hedgehog pathway and induce osteogenesis

Localized induction of bone formation is essential during orthopedic procedures that involve skeletal repair, such as surgical treatment of non-union bone fractures and degenerative disk disease. Herein we disclose the synthesis and biological evaluation of novel oxysterol derivatives designed as anabolic bone growth agents. Structure-activity relationship studies of oxysterol 4 have identified analogues such as 18, 21 and 30. These new analogues are characterized by higher potency in an osteoblast differentiation assay and/or by increased metabolic stability in human liver microsomes. Oxysterols 4, 18 and 21 were evaluated in vivo in a rat spinal fusion model.

The role of nuclear matrix proteins binding to matrix attachment regions (Mars) in prostate cancer cell differentiation

In tumor progression definite alterations in nuclear matrix (NM) protein composition as well as in chromatin structure occur. The NM interacts with chromatin via specialized DNA sequences called matrix attachment regions (MARs). In the present study, using a proteomic approach along with a two-dimensional Southwestern assay and confocal laser microscopy, we show that the differentiation of stabilized human prostate carcinoma cells is marked out by modifications both NM protein composition and bond between NM proteins and MARs. Well-differentiated androgen-responsive and slowly growing LNCaP cells are characterized by a less complex pattern and by a major number of proteins binding MAR sequences in comparison to 22Rv1 cells expressing androgen receptor but androgen-independent. Finally, in the poorly differentiated and strongly aggressive androgen-independent PC3 cells the complexity of NM pattern further increases and a minor number of proteins bind the MARs. Furthermore, in this cell line with respect to LNCaP cells, these changes are synchronous with modifications in both the nuclear distribution of the MAR sequences and in the average loop dimensions that significantly increase. Although the expression of many NM proteins changes during dedifferentiation, only a very limited group of MAR-binding proteins seem to play a key role in this process. Variations in the expression of poly (ADP-ribose) polymerase (PARP) and special AT-rich sequence-binding protein-1 (SATB1) along with an increase in the phosphorylation of lamin B represent changes that might trigger passage towards a more aggressive phenotype. These results suggest that elucidating the MAR-binding proteins that are involved in the differentiation of prostate cancer cells could be an important tool to improve our understanding of this carcinogenesis process, and they could also be novel targets for prostate cancer therapy.

p53 and MDM2 are involved in the regulation of osteocalcin gene expression

Osteocalcin (OC) is a major noncollagenous bone matrix protein and an osteoblast marker whose expression is limited to mature osteoblasts during the late differentiation stage. In previous studies we have shown osteosarcomas to lose p53 function with a corresponding loss of osteocalcin gene expression. Introduction of wild type p53 resulted in re expression of the osteocalcin gene. Using gel shift and chromatin immunoprecipitation assays, we have identified a putative p53 binding site within the rat OC promoter region and observed an increase in OC promoter activity when p53 accumulates using a CAT assay. The p53 inducible gene Mdm2 is a well-known downstream regulator of p53 levels. Our results showed a synergistic increase in the OC promoter activity when both p53 and MDM2 were transiently overexpressed. We further demonstrate that p53 is not degraded during overexpression of MDM2 protein. Increased OC expression was observed with concomitantly increased p53, VDR, and MDM2 levels in ROS17/2.8 cells during treatment with differentiation promoting (DP) media, but was significantly decreased when co-treated with DP media and the small molecule inhibitor of MDM2-p53 interaction, Nutlin-3. We have also observed a dramatic increase of the OC promoter activity in the presence of p53 and Mdm2 with inclusion of Cbfa-1 and p300 factors. Our results suggest that under some physiological conditions the oncoprotein MDM2 may cooperate with p53 to regulate the osteocalcin gene during osteoblastic differentiation.

Cross-immunoreactivity between the LH1 antibody and cytokeratin epitopes in the differentiating epidermis of embryos of the grass snake Natrix natrix L. during the end stages of embryogenesis

The monoclonal anti-cytokeratin 1/10 (LH1) antibody recognizing K1/K10 keratin epitopes that characterizes a keratinized epidermis of mammals cross-reacts with the beta and Oberhäutchen layers covering the scales and gastrosteges of grass snake embryos during the final period of epidermis differentiation. The immunolocalization of the anti-cytokeratin 1/10 (LH1) antibody appears in the beta layer of the epidermis, covering the outer surface of the gastrosteges at the beginning of developmental stage XI, and in the beta layer of the epidermis, covering the outer surface of the scales at the end of developmental stage XI. This antibody cross-reacts with the Oberhäutchen layers in the epidermis covering the outer surface of both scales and gastrosteges at developmental stages XI and XII just before its fusion with the beta layers. After fusion of the Oberhäutchen and beta layers, LH1 immunolabeling is weaker than before. This might suggest that alpha-keratins in these layers of the epidermis are masked by beta-keratins, modified, or degraded. The anti-cytokeratin 1/10 (LH1) antibody stains the Oberhäutchen layer in the epidermis covering the inner surface of the gastrosteges and the hinge regions between gastrosteges at the end of developmental stage XI. However, the Oberhäutchen of the epidermis covering the inner surfaces of the scales and the hinge regions between scales does not show cytokeratin 1/10 (LH1) immunolabeling until hatching. This cross-reactivity suggests that the beta and Oberhäutchen layers probably contain some alpha-keratins that react with the LH1 antibody. It is possible that these alpha-keratins create specific scaffolding for the latest beta-keratin deposition. It is also possible that the LH1 antibody cross-reacts with other epidermal proteins such as filament-associated proteins, i.e., filaggrin-like. The anti-cytokeratin 1/10 (LH1) antibody does not stain the alpha and mesos layers until hatching. We suppose that the differentiation of these layers will begin just after the first postnatal sloughing.

Modulation of the functions of osteoblast-like cells on poly(allylamine hydrochloride) and poly(acrylic acid) multilayer films

Deposition of layer-by-layer polyelectrolyte multilayer (PEM) films has been a widely applied surface modification technique to improve the biocompatibility of biomaterials. The objective of this study was to investigate the impact of the deposition of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) multilayer films on adhesion, growth and differentiation of osteoblasts-like MG63 cells. PAH and PAA were deposited sequentially onto tissue culture polystyrene at either pH 2.0 or pH 6.5 with 4-21 layers. While the MG63 cells attached poorly on the PAH/PAA multilayer films deposited at pH 2.0, while the cells adhered to the PEM films deposited at pH 6.5, depending on layer numbers. Cell adhesion, proliferation and osteogenic activities (alkaline phosphatase activity, expression of osteogenic marker genes and mineralization) were highest on the 4-layer PAH/PAA film and decreased with increasing layer numbers. On the other hand, the behavior of MG63 cells did not show any difference on the adjacent even and odd layers, except PEM4 and PEM5, i.e. the surface charges of the PAH/PAA multilayer films with over ten layers seem indifferent to osteoblastic functions. The results in this study suggested that the mechanical properties of PEM films may play a critical role in modulating the behavior of osteoblasts, providing guidance for application of PEM films to osteopaedic implants.

N-acetyl-L-cysteine enhances the osteogenic differentiation and inhibits the adipogenic differentiation through up regulation of Wnt 5a and down regulation of PPARG in bone marrow stromal cells

Nowadays, the treatment of osteoporosis is still a great challenge in the medical field. The combination of enhancement of osteogenesis and the inhibition of adipogenesis of bone marrow stromal cells (BMSCs) is considered an efficient therapeutic strategy for the treatment of osteoporosis. In the present study, we investigated the effects of N-acetyl-L-cysteine (NAC) on the proliferation, osteogenesis and adipogenesis of BMSCs. NAC treatment enhanced the alkaline phosphatase activity, mineral deposition and mRNA expression levels of osteogenesis markers collagen I, osteopontin, and signal pathway related protein Wingless-type family member 5a in addition to Wingless-type family member 3a during osteogenic induction, and inhibited the accumulation of lipid droplets and the expression levels of lipoprotein lipase, fatty acid binding protein 4 and peroxisome proliferator-activated receptor gamma mRNA during adipogenic induction. Meanwhile, NAC had the same effects as enhancing mineral deposition in regular culture condition. In addition, cell proliferation was also promoted by NAC treatment in regular culture condition. These results suggested that NAC may enhance osteogenic differentiation and inhibit adipogenic differentiation of BMSCs, which is at least partially mediated by up regulating Wnt 5a and down regulating PPARG. Taking into account the extensive protective effects of NAC and that the maintenance of BMSCs number is an important factor in osteoporosis prevention and treatment, these observations suggested that NAC is a promising potential drug for the prevention and treatment of osteoporosis and its associated diseases.

Human adipose-derived side population stem cells cultured on demineralized bone matrix for bone tissue engineering

BACKGROUND

Tissue engineering of new bone relies on the combination and application of osteoconductive, osteoinductive, and osteogenic elements. Natural scaffolds, such as demineralized bone matrix (DBM), contain collagenous networks with growth factors such as bone morphogenetic protein-2. Stem cells from readily available sources, including discarded adipose tissue, have the propensity to differentiate into bone. The present study examines a multi-component technique consisting of a novel side population of adipose stem cells cultured on DBM for tissue engineering applications.

METHODS

Adipose-derived side population stem cells were cultured on DBM for up to 14 days. Cell proliferation, alkaline phosphatase activity, extracellular matrix protein production, and calcium-containing mineral deposit formation were assayed. Ectopic bone formation in a rat model was also evaluated.

RESULTS

Side population stem cells attached to and proliferated on DBM while generating markers of new bone formation. When these cell/substrate composites were implanted into an ectopic model, newly formed bone was 30% greater than that of DBM alone.

CONCLUSIONS

Novel populations of adipose-derived stem cells cultured on DBM compose a system that develops new bone matrix in vitro and in vivo. This strategy provides a novel approach using naturally occurring materials for bone repair in tissue engineering applications.

Nuclear matrix proteome analysis of Drosophila melanogaster

The nucleus is a highly structured organelle and contains many functional compartments. Although the structural basis for this complex spatial organization of compartments is unknown, a major component of this organization is likely to be the non-chromatin scaffolding called nuclear matrix (NuMat). Experimental evidence over the past decades indicates that most of the nuclear functions are at least transiently associated with the NuMat, although the components of NuMat itself are poorly known. Here, we report NuMat proteome analysis from Drosophila melanogaster embryos and discuss its links with nuclear architecture and functions. In the NuMat proteome, we found structural proteins, chaperones, DNA/RNA-binding proteins, chromatin remodeling and transcription factors. This complexity of NuMat proteome is an indicator of its structural and functional significance. Comparison of the two-dimensional profile of NuMat proteome from different developmental stages of Drosophila embryos showed that less than half of the NuMat proteome is constant, and the rest of the proteins are stage-specific dynamic components. These NuMat dynamics suggest a possible functional link between NuMat and embryonic development. Finally, we also showed that a subset of NuMat proteins remains associated with the mitotic chromosomes, implicating their role in mitosis and possibly the epigenetic cellular memory. NuMat proteome analysis provides tools and opens up ways to understand nuclear organization and function.

Polyelectrolyte multilayer films functionalized with peptides for promoting osteoblast functions

Layer-by-layer deposition of polyelectrolyte multilayer (PEM) thin films has recently been applied to biomaterial applications. This simple and versatile technique provides a wide variety of potential utilization by insertion of biomolecules such as cell adhesion peptides. In this work dual peptides containing RGD (a cell-binding domain) and LHRRVKI (a heparin-binding domain) were immobilized onto polystyrene by the PEM technique and the effects on osteoblast cell culture were investigated. These peptides were conjugated to the amino groups of poly(allylamine hydrochloride) and then adsorbed onto the top of a 10 layer poly(allylamine hydrochloride)/poly(acrylic acid) film assembled at either pH 2.0 or pH 6.5. Osteoblasts, isolated from neonatal rat calvariae, were then seeded and cultured on the peptide-conjugated surfaces. We found that the cells adhered and grew better on the RGD-conjugated PEM films. The osteoblasts exhibited a better differentiated phenotype on the pH 2.0 films than the pH 6.5 films with respect to calcium deposition. The incorporation of LHRRVKI did not support cell adhesion, growth and matrix mineral deposition. Our results showed that the efficacy of RGD conjugation on osteoblast behavior was affected by the base PEM film.

Composite chitosan/nano-hydroxyapatite scaffolds induce osteocalcin production by osteoblasts in vitro and support bone formation in vivo

There is a significant clinical need to develop alternatives to autografts and allografts for bone grafting procedures. Porous, biodegradable scaffolds based on the biopolymer chitosan have been investigated as bone graft substitutes, and the addition of calcium phosphate to these scaffolds has been shown to improve the mechanical properties of the scaffold and may increase osteoconductivity. In this study, in vitro mineralization was examined for osteoblasts seeded in a porous scaffold composed of fused chitosan/nano-hydroxyapatite microspheres. Human fetal osteoblasts were cultured on composite and chitosan scaffolds for 21 days. On days 1, 4, 7, 14, and 21, total dsDNA, alkaline phosphatase, type I collagen, and osteocalcin production were measured. Total cellularity (measured by dsDNA), alkaline phosphatase, and type I collagen production were similar between the two scaffold groups. However, osteocalcin production occurred significantly earlier (day 7 vs. day 21) and was more than three times greater (0.0022 vs. 0.0068 ng/mL/ng DNA) on day 21 when osteoblasts were cultured on composite scaffolds. Osteocalcin is a marker of late osteoblastic differentiation and mineralized bone matrix formation. Therefore, the increase in osteocalcin production seen when cells were cultured on composite scaffolds may indicate that these scaffolds were superior to chitosan-only scaffolds in facilitating osteoblast mineralization. Composite scaffolds were also shown to be biocompatible and osteoconductive in a preliminary critical size rat calvarial defect study. These results demonstrate the potential of composite chitosan/nano-hydroxyapatite scaffolds to be used in bone tissue engineering.

Nuclear deformation and expression change of cartilaginous genes during in vitro expansion of chondrocytes

Cartilaginous gene expression decreased when chondrocytes were expanded on cell-culture plates. Understanding the dedifferentiation mechanism may provide valuable insight into cartilage tissue engineering. Here, we demonstrated the relationship between the nuclear shape and gene expression during in vitro expansion culture of chondrocytes. Specifically, the projected nuclear area increased and cartilaginous gene expressions decreased during in vitro expansion culture. When the nuclear deformation was recovered by cytochalasin D treatment, aggrecan expression was up-regulated and type I collagen (Col1a2) expression was down-regulated. These results suggest that nuclear deformation may be one of the mechanisms for chondrocyte dedifferentiation during in vitro expansion culture.

Long-term effects of tripeptide Ile-Pro-Pro on osteoblast differentiation in vitro

Bone mineralization is a result of the function of bone-forming osteoblasts. Osteoblast differentiation from their precursors is a carefully controlled process that is affected by many signaling molecules. Protein-rich food-derived bioactive peptides are reported to express a variety of functions in vivo. We studied the long-term in vitro effect of bioactive tripeptide Ile-Pro-Pro (IPP) on osteoblasts differentiated from human mesenchymal stem cells. Osteoblast bone alkaline phosphatase activity (bALP), bone-forming capacity and gene expression were investigated. Treatment with 50 microM IPP had no effect on bALP activity, but osteoblast mineralization was increased. Gene expression of beta-catenin, Cbfa1/Runx2, PTHrP, CREB-5, osteoglycin, osteocalcin, caspase-8, osteoprotegerin (OPG) and RANKL was analyzed by quantitative real-time PCR on Days 13, 17 and 20 of culture. The results indicate that IPP increased mineral formation due to enhanced cell survival and matrix formation. In addition, IPP reduced the RANKL/OPG ratio. Bioactive peptides, such as IPP, could be one method by which a protein-rich diet promotes bone integrity.

Miscibility and in vitro osteocompatibility of biodegradable blends of poly[(ethyl alanato) (p-phenyl phenoxy) phosphazene] and poly(lactic acid-glycolic acid)

Previously we demonstrated the ability of ethyl glycinato substituted polyphosphazenes to neutralize the acidic degradation products and control the degradation rate of poly(lactic acid-glycolic acid) (PLAGA) by blending. In this study, blends of high strength poly[(50% ethyl alanato) (50% p-phenyl phenoxy) phosphazene] (PNEA(50)PhPh(50)) and 85:15 PLAGA were prepared using a mutual solvent approach. Three different solvents, methylene chloride (MC), chloroform (CF) and tetrahydrofuran (THF) were studied to investigate solvent effects on blend miscibility. Three different blends were then fabricated at various weight ratios namely 25:75 (BLEND25), 50:50 (BLEND50), and 75:25 (BLEND75) using THF as the mutual solvent. The miscibility of the blends was evaluated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). Among these, BLEND25 was miscible while BLEND50 and BLEND75 were partially miscible. Furthermore, BLEND25 formed apatite layers on its surface as evidenced in a biomimetic study performed. These novel blends showed cell adhesion and proliferation comparable to PLAGA. However, the PNEA(50)PhPh(50) component in the blends was able to increase the phenotypic expression and mineralized matrix synthesis of the primary rat osteoblasts (PRO) in vitro. Blends of high strength PNEA(50)PhPh(50) and 85:15 PLAGA are promising biomaterials for a variety of musculoskeletal applications.

Osteogenic phenotypes and mineralization of cultured human periosteal-derived cells

Stem cells or osteogenic precursor cells isolated from bone marrow, trabecular tissues in bone, cartilage, muscle, and fat are the most suitable source for bone tissue engineering. In this study, we investigated the osteogenic phenotypes and mineralization of cultured human periosteal-derived cells obtained from mandibular periosteums. These periosteal-derived cells were positive for CD44, CD90, and CD166 antigens. They are successfully differentiated into osteoblasts in the medium containing dexamethasone, ascorbic acid, and beta-glycerophosphate. We observed that alkaline phosphatase (ALP) was largely expressed in the earlier stage of osteoblastic differentiation according to histochemical staining and RT-PCR analysis, whereas osteocalcin was dominantly expressed and secreted into the medium at the later stage. In addition, mineralized nodule formation has been observed by von Kossa staining in a time-dependent manner. These results suggest that periosteal-derived cell has the potential osteogenic activity and could be a good candidate for tissue engineering to restore the bony defects of the maxillofacial region.

The BTB domain of the nuclear matrix protein NRP/B is required for neurite outgrowth

The neuronal nuclear matrix protein, NRP/B, contains a BTB domain and kelch repeats and is expressed in primary neurons but not in primary glial cells. To examine the function of NRP/B in neurons, we analyzed the structure/function of the NRP/B-BTB domain and its role in neurite outgrowth. Based on three-dimensional modeling of NRP/B, we generated an NRP/B-BTB mutant containing three mutations in the conserved amino acids D47A, H60A and R61D that was termed BTB mutant A. BTB mutant A significantly reduced the dimerization of NRP/B compared to wild-type NRP/B. The NRP/B-BTB domain was required for nuclear localization and mediated the association of NRP/B with p110RB through the TR subdomain within the B pocket of p110RB. Overexpression of wild-type NRP/B and NRP/B-BTB domain significantly induced neurite outgrowth in PC12 cells and enhanced the G0-G1 cell population by ∼23% compared to the control cells, whereas NRP/B-BTB mutant A reduced neurite outgrowth by 70-80%, and inhibited NRP/B-p110RB association. Single cell microinjection of NRP/B-specific antibodies also blocked the neurite outgrowth of PC12 cells upon NGF stimulation. Interference of NRP/B expression by small interfering RNA (NRP/B-siRNA) inhibited neurite outgrowth and suppressed the NGF-induced outgrowth of neurites in PC12 cells. Additionally, p110RB phosphorylation at serine residue 795 was significantly reduced in PC12 cells treated with NRP/B siRNA compared to those treated with control GFP-siRNA, indicating that p110RB is a downstream target of NRP/B. Thus, the BTB domain of NRP/B regulates neurite outgrowth through its interaction with the TR subdomain within the B pocket of p110RB, and the conserved amino acids D47A, H60A and R61D within this domain of NRP/B are crucial residues for neurite extension in neuronal cells. These findings support a role for the BTB-domain of NRP/B as an important regulator of neuronal differentiation.

Runx2: A master organizer of gene transcription in developing and maturing osteoblasts

Runx2 is essential for osteoblast development and proper bone formation. A member of the Runt domain family of transcription factors, Runx2 binds specific DNA sequences to regulate transcription of numerous genes and thereby control osteoblast development from mesenchymal stem cells and maturation into osteocytes. Although necessary for gene transcription and osteoblast development, Runx2 is not sufficient for optimal gene expression or bone formation. Runx2 cooperates with numerous proteins, including transcription factors and cofactors, is posttranslationally modified, and associates with the nuclear matrix to integrate a variety of signals and organize crucial events during osteoblast development and maturation. Consistent with its role as a master organizer, alterations in Runx2 expression levels are associated with skeletal diseases. Runx2 haploinsufficiency causes cleidocranial dysplasia, while Runx2 overexpression is common in many bone-metastatic cancers. In this review, we summarize the molecular mechanisms by which Runx2 integrates signals through coregulatory interactions, and discuss how its role as a master organizer may shift depending on promoter structure, developmental cues, and cellular context.

A systematic review of the influence of different titanium surfaces on proliferation, differentiation and protein synthesis of osteoblast-like MG63 cells

OBJECTIVES

Titanium is the standard material for dental and orthopaedical implants. The good biocompatibility has been proven in many experimental and clinical investigations. Different titanium topographies were tested in vitro using different cell culture models. The aim of this systematic review was to evaluate and summarize the medical/dental literature to assess on which kind of titanium surface structure the osteoblast-like osteosarcoma cells MG63 show the best proliferation and differentiation rate, and the best protein synthesis.

METHODS

A systematic search was carried out using different on-line databases (PubMed, Web of Science, Cochrane Library, International Poster Journal), supplemented by handsearch in selected journals and by examination of the bibliographies of the identified articles. Inclusion and exclusion criterias were applied when considering relevant articles. Studies which met the inclusion criteria were included and data extraction was undertaken by one reviewer.

RESULTS

The search yielded 348 references. Nine articles referring to nine different studies were relevant to our question. Additionally 8 less relevant articles were identified. It was found that regularly textured surfaces of pure titanium with R(a) values (average roughness) of around 4 mum are well-accepted by MG63 cells.

CONCLUSIONS

The surfaces and culture conditions vary widely. Therefore it is still difficult to recommend one particular surface. It seems that there are no differences in cell proliferation and differentiation on surfaces treated by blasting and etching. Standardization in fabrication and size of the different test surfaces as well as homogeneity in culture times and plating densities should be aspects for future research.

Nuclear structure in cancer cells

Nuclear architecture - the spatial arrangement of chromosomes and other nuclear components - provides a framework for organizing and regulating the diverse functional processes within the nucleus. There are characteristic differences in the nuclear architectures of cancer cells, compared with normal cells, and some anticancer treatments restore normal nuclear structure and function. Advances in understanding nuclear structure have revealed insights into the process of malignant transformation and provide a basis for the development of new diagnostic tools and therapeutics.

Expression and functional significance of mouse paraspeckle protein 1 on spermatogenesis

Paraspeckle protein 1 (PSP1) in humans is a recently identified component protein of a novel nuclear body, paraspeckle. The protein has a DBHS (Drosophila behavior, human splicing) motif that is found in PSF and p54(nrb)/NonO proteins. These DBHS-containing proteins have been reported to be involved in various nuclear events such as DNA replication, transcription, and mRNA processing. Here we show that mouse paraspeckle protein 1 (mPSP1; encoded by the Pspc1 gene) has two isoforms with different C-termini lengths. Abundant expression of the longer isoform (mPSP1-alpha) and the shorter one (mPSP1-beta) were observed in testis and kidney, respectively. Transiently expressed mPSP1-alpha was localized in nuclei, but mPSP1-beta was localized in both nuclei and cytoplasm. These observations suggest that alternative splicing regulates tissue distribution and subcellular localization. Like other DBHS-containing proteins, mPSP1 has RNA-binding activity. In mouse testis, mPSP1-alpha was found in the nuclear matrix fraction. Furthermore, by coimmunoprecipitation, we confirmed that mPSP1 interacts with other DBHS-containing proteins, PSF and p54(nrb)/NonO. Therefore, we conclude that mPSP1 may regulate multiple phases of important nuclear events during spermatogenesis.

The influence of culture conditions on extracellular matrix proteins synthesized by osteoblasts derived from rabbit bone marrow

The influence of culture conditions on the extracellular matrix (ECM) protein expressions of rabbit bone marrow stromal cells has been studied. The focus was on the effects of two kinds of sera, fetal calf serum (FCS) and Ultroser, on cells treated with dexamethasone. The induction of osteoblastic differentiation by dexamethasone addition is confirmed, particularly when cells are cultured in FCS. Bone marrow stromal cells produce alkaline phosphatase positive CFU-F and produce ECM with some mineralized nodules. Analysis by means of two-dimensional gel electrophoresis showed important changes in the composition of ECM proteins after dexamethasone treatment. Overexpression, underexpression, and new synthesized proteins were observed. The most significant modification was linked to the synthesis of four new proteins visible in the acidic area with a low molecular weight of around 17 kDa. These proteins did not correspond to those ECM proteins known to be induced by dexamethasone. Moreover, the effect of dexamethasone on osteoblastic differentiation induction appears very limited when cells are cultured in Ultroser compared to FCS. The protein pattern with Ultroser is different to that obtained with FCS. Cells cultured in Ultroser synthesized no new protein. The different behavior of cells according to the type of medium used is discussed in terms of the osteogenic factors present in the two different sera.

Further characterization of human fetal osteoblastic hFOB 1.19 and hFOB/ER alpha cells: bone formation in vivo and karyotype analysis using multicolor fluorescent in situ hybridization

We have previously generated an immortalized human fetal osteoblastic cell line (hFOB) using stably transfected temperature sensitive SV40 T-antigen (Harris et al. [1995a] J. Bone. Miner. Res. 10:178-1860). To characterize these cells for phenotypic/genotypic attributes desired for a good cell model system, we performed karyotype analysis by multicolor fluorescent in situ hybridization (M-FISH), their ability to form bone in vivo without developing cell transformation, and finally their ability to form extracellular matrix formation in vitro. The karyotype analysis of hFOB cells revealed structural or numeric anomalies involving 1-2 chromosomes. In contrast, the human osteosarcoma MG63 cells displayed multiple, and often complex, numeric, and structural abnormalities. Subcutaneous injection of hFOB cells in the presence of Matrigel into nude mice resulted in bone formation after 2-3 weeks. Electron microscopic analysis of the extracellular matrix deposited by hFOB cells in culture revealed a parallel array of lightly banded fibrils typical of the fibrillar collagens such as type I and III. These results demonstrate that the hFOB cell line has minimal chromosome abnormalities, exhibit the matrix synthetic properties of differentiated osteoblasts, and are immortalized but non-transformed cell line. These hFOB cells thus appear to be an excellent model system for the study of osteoblast biology in vitro.

Cytokine release by osteoblast-like cells cultured on implant discs of varying alloy compositions

OBJECTIVE

The aims of this study were (i). to assess the morphological features of osteo-blast-like, osteosarcoma cells (cell line SaOS-2) cultured on implant surfaces of varying alloys and (ii). to evaluate the biological activity of these cells, following their adhesion onto these surfaces.

MATERIALS AND METHODS

SaOS-2 cells (6 x 104) were grown on titanium discs (diameter 30 mm), each with a surface of differing composition and roughness (commercially pure titanium, titanium-aluminium-vanadium alloy, oxide-blasted titanium and Astra-Tech special treatment titanium; the alloys are directly comparable with those used to construct implants). The cells were grown for time periods of 1, 3, 5 and 7 days, the media were collected and the cells were fixed with 2.5% glutaraldehyde. The media were then assayed (using enzyme-linked immunosorbant assay) for the levels of interleukin (IL)-1, interleukin-6, interleukin-18 and osteoprotegerin (OPG) produced by the cells. The discs, with the cells fixed on them, were viewed under scanning electron microscopy (SEM, x 2.0 k) to evaluate cell morphology.

RESULTS

Following attachment, the cells changed their morphology and released local factors known to activate osteoclasts. Commercially pure titanium stimulated the cells the most and titanium-aluminium-vanadium alloy the least. All implant materials stimulated production of IL-1, IL-6, IL-18 above that produced by cells grown on Petri dishes (polystyrene). The titanium-aluminium-vanadium alloy allowed cell attachment but levels of IL-1 in this medium were significantly lower (31.5 +/- 5.2 pg/ml on same day) than cultures with pure titanium (201.8 +/- 11.5 pg/ml at day 5). The same pattern was observed with the IL-6, IL-18, and OPG with polystyrene appearing to stimulate most production of OPG. Titanium-aluminium-vanadium produced the least biological response.

Identification of nuclear type II [(3)H]estradiol binding sites as histone H4

[3H]Luteolin binds covalently to uterine nuclear type II sites [B. Markaverich, K. Shoulars, M.A. Alejandro, T. Brown, Steroids 66 (2001) 707] and was used to identify this protein(s). SDS-PAGE analyses of [3H]luteolin-labeled type II site preparations revealed specific binding to 11- and 35-kDa proteins. The 11-kDa protein was identified as histone H4 by amino acid sequencing. Western blotting confirmed that the 11- and 35-kDa proteins were acetylated forms of histone H4. Anti-histone H4 antibodies (but not H2A, H2B, or H3 antibodies) quantitatively immunoadsorbed type II binding sites from nuclear extracts. Binding analyses by [3H]estradiol exchange, using luteolin as a competitor, detected specific type II binding activity to histone H4 (but not histones H2A, H2B, or H3) generated in a rabbit reticulocyte lysate translation system and confirmed that histone H4 is the type II site.

The matrix attachment region-binding protein SATB1 interacts with multiple elements within the gp91phox promoter and is down-regulated during myeloid differentiation

The gp91(phox) gene encodes a component of the respiratory burst NADPH oxidase complex and is highly expressed in mature myeloid cells. The transcriptional repressor CCAAT displacement protein binds to at least five sites within the proximal gp91(phox) promoter and represses expression prior to terminal phagocyte differentiation. The DNA binding activity of CCAAT displacement protein decreases during terminal phagocyte differentiation, thus permitting the binding of transcriptional activators and induction of gp91(phox) expression. We report here that the matrix attachment region-binding protein SATB1 interacts with at least seven sites within the -1542 to +12-base pair gp91(phox) promoter. Four additional binding sites for CCAAT displacement protein were also identified. Furthermore, the most proximal SATB1-binding site within the gp91(phox) promoter binds specifically to the nuclear matrix fraction in vitro. SATB1 expression is down-regulated during terminal myeloid cell differentiation, coincident with induction of gp91(phox) expression. Transient transfection assays demonstrate that a SATB1-binding site derived from the gp91(phox) promoter represses promoter activity in cells expressing SATB1. These findings underscore the importance of transcriptional repression in the regulation of gp91(phox) expression and reveal a candidate myeloid cell target gene for SATB1, a factor previously found to be essential for T cell development.

A specific targeting signal directs Runx2/Cbfa1 to subnuclear domains and contributes to transactivation of the osteocalcin gene

Key components of DNA replication and the basal transcriptional machinery as well as several tissue-specific transcription factors are compartmentalized in specialized nuclear domains. In the present study, we show that determinants of subnuclear targeting of the bone-related Runx2/Cbfa1 protein reside in the C-terminus. With a panel of C-terminal mutations, we further demonstrate that targeting of Runx2 to discrete subnuclear foci is mediated by a 38 amino acid sequence (aa 397-434). This nuclear matrix-targeting signal (NMTS) directs the heterologous Gal4 protein to nuclear-matrix-associated Runx2 foci and enhances transactivation of a luciferase gene controlled by Gal4 binding sites. Importantly, we show that targeting of Runx2 to the NM-associated foci contributes to transactivation of the osteoblast-specific osteocalcin gene in osseous cells. Taken together, these findings identify a critical component of the mechanisms mediating Runx2 targeting to subnuclear foci and provide functional linkage between subnuclear organization of Runx2 and bone-specific transcriptional control.

Nuclear matrix in developing rat spermatogenic cells

The nonchromatin structure or nuclear matrix in developing spermatogenic cells of the rat was studied using a biochemical fractionation in concert with resinless section electron microscopy. Observations demonstrated that the nuclear matrix of spermatogenic cells consisted of a three-dimensional network of filaments of variable thicknesses. In spermatogonia and spermatocytes the nuclear matrix consisted of relatively thin filaments, while that of round spermatids consisted of a thicker interconnecting network of filament. In elongating spermatids, the interior of the nuclear matrix consisted of a network of dense filaments bounded by a peripheral lamina. The protein composition of the nuclear matrix in spermatogenic cells was examined by high-resolution two-dimensional gel electrophoresis and correlated with morphological changes characteristic of each stage. The results showed that the proteins of nuclear matrix changed in a cell stage-specific manner. These stage-specific changes corresponded to the major transitions of chromatin structure and function during spermatogenesis. Furthermore, immunocytochemical and immunoblotting analysis of DNA topoisomerase II (topo II) revealed that this enzyme exhibited stage-specific variations and was associated with the nuclear matrix. These results suggest that the nuclear matrix in spermatogenic cells may be involved in mediating DNA modifications and maintaining nuclear organization during spermatogenesis. Mol. Reprod. Dev. 59:314-321, 2001.

Contributions of nuclear architecture and chromatin to vitamin D-dependent transcriptional control of the rat osteocalcin gene

The vitamin D response element in the bone tissue-specific osteocalcin gene has served as a prototype for understanding molecular mechanisms regulating physiologic responsiveness of vitamin D-dependent genes in bone cells. We briefly review factors which contribute to vitamin D transcriptional control. The organization of the vitamin D response element (VDRE), the multiple activities of the vitamin D receptor transactivation complex, and the necessity for protein-protein interactions between the VDR-RXR heterodimer activation complex and DNA binding proteins at other regulatory elements, including AP-1 sites and TATA boxes, provide for precise regulation of gene activity in concert with basal levels of transcription. We present evidence for molecular mechanisms regulating vitamin D-dependent mediated transcription of the osteocalcin gene that involve chromatin structure of the gene and nuclear architecture. Modifications in nucleosomal organization, DNase I hypersensitivity and localization of vitamin D receptor interacting proteins in subnuclear domains are regulatory components of vitamin D-dependent gene transcription. A model is proposed to account for the inability of vitamin D induction of the osteocalcin gene in the absence of ongoing basal transcription by competition of the YY1 nuclear matrix-associated transcription factor for TFIIB-VDR interactions. Activation of the VDR-RXR complex at the OC VDRE occurs through modifications in chromatin mediated in part by interaction of OC gene regulatory sequences with the nuclear matrix-associated Cbfa1 (Runx2) transcription factor which is required for osteogenesis.

The p38 mitogen-activated protein kinase pathway regulates interleukin-6 synthesis in response to tumor necrosis factor in osteoblasts

The induction of interleukin-6 (IL-6), using a proinflammatory cytokine (tumor necrosis factor-alpha), was studied in a human osteoblast cell line (MG-63) in relation to p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-kappaB transcription factor. When added to MG-63 cells, tumor necrosis factor-alpha (TNF-alpha) had a stimulatory effect on the production of IL-6, and this elevation was significantly reduced by SB203580, a specific p38 MAPK inhibitor. In addition, the stimulation of IL-6 release was also reduced by pyrrolidine dithiocarbamate (PDTC) or NF-kappaB SN50, which has been reported to be a potent NF-kappaB inhibitor. Both the NF-kappaB inhibitors in the presence of SB203580 had a more inhibitory effect on IL-6 release. In this study, TNF-alpha stimulated NF-kappaB binding affinity as well as p38 MAP kinase activation, leading to the release of IL-6. However, the specific inhibitor of p38 MAPK, SB203580, had no effect on TNF-alpha-induced NF-kappaB activation and both NF-kappaB inhibitors failed to reduce the p38 MAPK activation in the TNF-alpha-stimulated osteoblasts. In addition, inhibition of p38 MAPK partially, but significantly, impaired TNF-alpha-regulated release of osteocalcin, an important differentiation marker in osteoblasts. These results strongly suggest that both p38 MAPK and NF-kappaB are required in TNF-alpha-induced IL-6 synthesis and that these two TNF-alpha-activated pathways can be primarily dissociated. Furthermore, p38 MAPK may play a significant role in differentiation in MG-63 cells.

Genomic organization, chromosomal localization and regulation of expression of the neuronal nuclear matrix protein NRP/B in human brain tumors

The nuclear matrix and its role in cell physiology are largely unknown, and the discovery of any matrix constituent whose expression is tissue- and/or cell-specific offers a new avenue of exploration. Studies of the novel neuronal nuclear matrix protein, NRP/B, reveal that it is an early and highly specific marker of neuronal induction and development in vertebrates, since its expression is restricted mainly to the developing and mature nervous system. These studies also show that NRP/B is involved in neuronal differentiation. To further examine the structure-function of NRP/B, we have cloned and characterized the murine Nrp/b gene. The murine gene consists of four exons interrupted by three introns that span 7.6kb of DNA. The complete open reading frame is localized in exon 3, suggesting that NRP/B is highly conserved during evolution. Chromosomal analysis shows that NRP/B is localized to chromosome 13 in mouse and chromosome 5q12-13 in human. Since our previous studies demonstrated that NRP/B is expressed in primary hippocampal neurons but not in primary astrocytes, we have characterized NRP/B mRNA and protein expression in various brain cell lines and in human brain tumors. Abundant expression of NRP/B mRNA and protein was observed in human neuroblastoma cell lines (IMR32, SKN-MC, SKN-SH), in glioblastoma cell lines (A172, T98G, U87-MG, U118-MG, U138-MG, and U373-MG), in neuroglioma (H4) and astrocytoma cell lines (CCF-STTG1 and SW1088). Confocal analysis of NRP/B in U87-MG glioblastoma cells indicated nuclear localization of NRP/B. NRP/B expression was also observed in human primary brain tumors including glioblastoma multiformae and astrocytomas (total of five cases). These results suggest that NRP/B expression is upregulated in human brain tumors including glioblastomas and astrocytomas, while under normal conditions NRP/B expression is restricted to neurons. This study implicates a role for NRP/B in brain tumor development.

Carboxyl-terminal propeptide of type I collagen (c-propeptide) modulates the action of TGF-beta on MC3T3-E1 osteoblastic cells

Previously we found that the carboxyl-terminal propeptide of type I collagen (c-propeptide) is a major secretory protein of MC3T3-E1 osteoblastic cells. In this study, we found that c-propeptide suppresses collagen synthesis and alkaline phosphatase activity of MC3T3-E1 osteoblastic cells at the early-differentiated stage in a dose dependent manner. Mature osteoblasts did not respond to c-propeptide. These findings imply that c-propeptide modulates the function of osteoblasts at an early differentiation stage. Transforming growth factor-beta (TGF-beta) is stored in bone and released from bone matrix after the resorption by osteoclasts. We investigated the effect of c-propeptide on the action of TGF-beta, and found that it enhanced the effect of TGF-beta. We conclude that c-propeptide is a physiological modulator of TGF-beta in bone metabolism.

Pulsed electromagnetic field stimulation of MG63 osteoblast-like cells affects differentiation and local factor production

Pulsed electromagnetic field stimulation has been used to promote the healing of chronic nonunions and fractures with delayed healing, but relatively little is known about its effects on osteogenic cells or the mechanisms involved. The purpose of this study was to examine the response of osteoblast-like cells to a pulsed electromagnetic field signal used clinically and to determine if the signal modulates the production of autocrine factors associated with differentiation. Confluent cultures of MG63 human osteoblast-like cells were placed between Helmholtz coils and exposed to a pulsed electromagnetic signal consisting of a burst of 20 pulses repeating at 15 Hz for 8 hours per day for 1, 2, or 4 days. Controls were cultured under identical conditions, but no signal was applied. Treated and control cultures were alternated between two comparable incubators and, therefore, between active coils; measurement of the temperature of the incubators and the culture medium indicated that application of the signal did not generate heat above the level found in the control incubator or culture medium. The pulsed electromagnetic signal caused a reduction in cell proliferation on the basis of cell number and [3H]thymidine incorporation. Cellular alkaline phosphatase-specific activity increased in the cultures exposed to the signal, with maximum effects at day 1. In contrast, enzyme activity in the cell-layer lysates, which included alkaline phosphatase-enriched extracellular matrix vesicles, continued to increase with the time of exposure to the signal. After 1 and 2 days of exposure, collagen synthesis and osteocalcin production were greater than in the control cultures. Prostaglandin E2 in the treated cultures was significantly reduced at 1 and 2 days, whereas transforming growth factor-beta1 was increased; at 4 days of treatment, however, the levels of both local factors were similar to those in the controls. The results indicate enhanced differentiation as the net effect of pulsed electromagnetic fields on osteoblasts, as evidenced by decreased proliferation and increased alkaline phosphatase-specific activity, osteocalcin synthesis, and collagen production. Pulsed electromagnetic field stimulation appears to promote the production of matrix vesicles on the basis of higher levels of alkaline phosphatase at 4 days in the cell layers than in the isolated cells, commensurate with osteogenic differentiation in response to transforming growth factor-beta1. The results indicate that osteoblasts are sensitive to pulsed electromagnetic field stimulation, which alters cell activity through changes in local factor production.

Colorectal cancer-associated nuclear antigen

By using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting assays in the presence of polyclonal antiserum raised against electrophoretically specific polypeptides of colorectal cancer nuclear polypeptides with M(r) of 35-40 kDa, we have identified p36 protein whose expression accompanies tumorigenesis of large intestine. Immunological analysis of 35 nuclear protein preparations has indicated expression of p36 antigen in nine of 11 right-sided (81.8%) and 21 of 24 (87.5%) left-sided colorectal tumor cases, but not in any control tissue samples. In this study, we have identified p36 antigen in two colon tumor cell lines, i.e., SW620 and HT29 as well. Fractionation experiments based on selective extraction of nuclei isolated from cancerous specimens, which enables their separation into chromatin, nuclear matrix and its subfraction, i.e., internal and peripheral matrix have revealed the concentration of this particular antigen in the internal matrix.