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Patterns of SPARC expression and basement membrane intactness at the tumour-brain border of invasive meningiomas.

The matricellular glycoprotein SPARC (secreted protein, acidic and rich in cysteine), also termed osteonectin, has been found to regulate the invasive behaviour of several tumour types by interacting with basement membrane constituents. Brain invasive meningiomas are supposed to disrupt the pial-glial basement membrane. In the present study we aimed at determining the relationship of basement membrane intactness and SPARC protein expression at the meningioma-brain border. Sections of 51 brain-invasive meningiomas (31 meningothelial meningiomas WHO grade I, 11 atypical WHO grade II, and nine anaplastic WHO grade III tumours) were immunolabelled with antibodies against SPARC, epithelial membrane antigen (EMA), collagen IV and glial fibrillary acidic protein (GFAP). Twenty-two non-invasive WHO grade I meningothelial meningiomas were included in the study for comparison. At the tumour-brain border of invasive meningiomas, spindle-shaped tumour cells expressed SPARC. The number of tumours containing SPARC+ spindle cells did not differ significantly between WHO grades. By contrast, the number of WHO grade I tumours expressing collagen IV (15/31) was highly significantly elevated when compared with WHO grade II (1/11) and WHO grade III (0/9) (both P < 0.0001). There was an inverse relationship of the presence of SPARC+ spindle cells and basement membrane material. In conclusion, the destruction of the basement membrane is correlated with meningioma malignancy grade whereas the expression of SPARC protein at the tumour-brain border is not. Destruction of the basement membrane and appearance of SPARC+ spindle cells are not coincident during the course of brain invasion by meningiomas.

Adult↗

Investigating the effects of preinduction on human adipose-derived precursor cells in an athymic rat model.

The osteogenic potential of human adipose-derived precursor cells seeded on medical-grade polycaprolactone-tricalcium phosphate scaffolds was investigated in this in vivo study. Three study groups were investigated: (1) induced--stimulated with osteogenic factors only after seeding into scaffold; (2) preinduced--induced for 2 weeks before seeding into scaffolds; and (3) uninduced--cells without any introduced induction. For all groups, scaffolds were implanted subcutaneously into the dorsum of athymic rats. The scaffold/cell constructs were harvested at the end of 6 or 12 weeks and analyzed for osteogenesis. Gross morphological examination using scanning electron microscopy indicated good integration of host tissue with scaffold/cell constructs and extensive tissue infiltration into the scaffold interior. Alizarin Red histology and immunostaining showed a heightened level of mineralization and an increase in osteonectin, osteopontin, and collagen type I protein expression in both the induced and preinduced groups compared with the uninduced groups. However, no significant differences were observed in these indicators when compared between the induced and preinduced groups.

Adipose Tissue↗

High-affinity and low-affinity calcium binding and stability of the multidomain extracellular 40-kDa basement membrane glycoprotein (BM-40/SPARC/osteonectin).

Reversible binding of calcium ions to a single high-affinity binding site in the 40-kDa basement membrane protein (BM-40) caused a 33% increase of alpha-helicity, an about 60% change in intrinsic fluorescence and a dramatic increase of the rate of cleavage by alpha-chymotrypsin. All these effects exhibited identical dependencies on calcium concentration from which a dissociation constant Kd = 0.6 microM was determined. Calcium release was accompanied by an increase of the frictional ratio in solution but not by denaturation which occurred at about equal guanidine.HCl concentration for both calcium-saturated and calcium-depleted protein (midpoint 1.5 M). The cleavage sites for alpha-chymotrypsin are located in or near to the EF-hand domain IV of calcium-depleted BM-40 (also known as SPARC, i.e. secreted protein acidic and rich in cysteine, and osteonectin). These and other data indicate that binding occurs in the EF-hand domain from which a large conformational change is transmitted. Low-affinity calcium-binding sites in the N-terminal glutamic-acid-rich domain I of BM-40 were identified by human leukocyte elastase which was found to cleave very specifically in the middle of this domain. From the increase of cleavage rate with increasing calcium concentration a Kd greater than or equal to 10 mM was estimated. It is suggested that variations of calcium levels in the extracellular space in this range may regulate functions of BM-40 such as collagen binding and that high-affinity binding is important for stabilization, folding and secretion during biosynthesis.

Amino Acid Sequence↗

Testican, a multidomain testicular proteoglycan resembling modulators of cell social behaviour.

The molecular characterization of a human testicular proteoglycan, the progenitor of a seminal plasma glycosaminoglycan-bearing peptide, was achieved by cDNA cloning. Its protein core encompasses several domains encountered in various proteins associated with adhesion, migration and cell proliferation. An osteonectin-like domain, a Kazal-like sequence and a 46-amino-acid motif around a Cys-Trp-Cys-Val peptide encountered in cell-surface antigens, cell-adhesion molecules and growth-factor-binding proteins are distributed within the testican protein core. Testican is the progenitor of the unique heparan/chondroitin-sulfate-bearing peptide present in human seminal plasma, a feature which might confer additional potentialities to this hybrid proteoglycan.

Agrin↗

The effect of bioactive glass ceramics on the expression of bone-related genes and proteins in vitro.

Using biodegradable bone substitutes in alveolar ridge augmentation avoids second-site surgery for autograft harvesting. Considerable efforts have been undertaken to develop rapidly resorbable bone substitute materials with a higher degree of biodegradability than tricalcium phosphate (TCP). This study examines the effect of novel biodegradable glass ceramics on the expression of bone-related genes and proteins by human bone-derived cells (HBDC) and compares this behavior with that of TCP. Test materials used were alpha-TCP, a surface-treated glass ceramic GB9N with crystalline phase Ca(2)KNa(PO(4))(2) and a small amount of amorphous silica phosphate; AP40 - a glass ceramic based on crystalline phases of apatite and wollastonite; and a glass ceramic Mg5 composed of 20.6% CaO, 58.5% P(2)O(5), 14.4% Na(2)O, 4.1% MgO and 2.4% CaF(2) (wt%). HBDC were grown on the substrata for 3, 5, 7, 14 and 21 days, counted and probed for various bone-related mRNAs and proteins (type I collagen (Col I), osteocalcin (OC), osteopontin (OP), osteonectin (ON), alkaline phosphatase (ALP) and bone sialoprotein (BSP)). The substrata supported continuous cellular growth for 21 days. By day 21, GB9N had the highest number of HBDC. GB9N induced significantly enhanced expression of Col I, ALP, OP, OC and ON mRNA at 3 days; of OP, OC and ON mRNA and protein at 7 and 14 days; and of ALP, OP and OC mRNA and Col I, ALP, BSP, ON and OP protein at 21 days. Since all novel glass ceramics supported cellular proliferation together with expression of bone-related genes and proteins at least as much as TCP, these ceramics can be regarded as potential bone substitutes. GB9N had the most effect on osteoblastic differentiation, thus suggesting that this material may possess a higher potency to enhance osteogenesis than TCP.

Absorbable Implants↗

Three-dimensional composites manufactured with human mesenchymal cambial layer precursor cells as an alternative for sinus floor augmentation: an in vitro study.

Bone tissue engineering is a promising approach for treatment of defective and lost bone in the maxillofacial region. Creating functional tissue for load bearing bone reconstruction using biocompatible and biodegradable scaffolds seeded with living cells is of crucial importance. The aim of our study was to compare the effects of poly-lactic-co-glycolic acid (PLGA) and hydroxyapatite (HA) ceramic granulae on growth, differentiation, mineralization and gene expression of mandibular mesenchymal cambial layer precursor cells (MCLPCs) cultured onto tissue engineered three-dimensional (3-D) composites in vitro. These 3-D composites were cultivated in a rotating cultivation system under osteogenic differentiation conditions for a maximum period of 21 days. After 6 and 21 days, histological examination was performed; scanning electron microscopy (SEM), alkaline phosphatase (ALP) activity and levels of DNA were investigated. Expression of bone-specific genes osteocalcin, osteonectin, osteopontin, ALP, core binding factor alpha 1 and collagen type I were investigated by using a reverse transcription-polymerase chain reaction (RT-PCR) method. After 6 and 21 days of incubation an initiation of mineralization and the presence of newly formed bone at the surface of the composites were shown after evaluation of ALP activity, DNA content, SEM and histological staining. Expression of bone-specific genes confirmed the bone-like character of these composites and different effects of PLGA or HA granulae on the osteogenic differentiation of human MCLPCs in vitro. The results of this study support the concept that substrate signals significantly influence MCLPCs growth, differentiation, mineralization and gene expression in vitro, and that the use of these cells in the manufacturing of 3-D cell/HA composites is a promising approach for load bearing bone reconstruction in the maxillofacial region in vivo.

Alkaline Phosphatase↗

Does rotational strain at screw tightening affect the attainment or maintenance of osseointegration?

OBJECTIVES: This study investigated whether rotational strain affects osseointegration. MATERIAL AND METHODS: A total of 135 male rats were divided into five groups: 2-w rotation, 4-w rotation, 8-w rotation, 12-w rotation and control. Two hundred and seventy implants were inserted in rat tibia. The control group received no strain, while the 2-w, 4-w, 8-w and 12-w rotation groups received rotational strain at 2, 4, 8 and 12 weeks after implant placement, respectively. Removal torque (N cm) was measured in vivo. Bone contact rate (%) was calculated histomorphologically. Immunostaining for osteonectin (ON), osteopontin (OPN) and osteocalcin (OCN) was performed. The removal torque and bone contact rate were analyzed using one-way analyses of variance and the Scheffé method. RESULTS: At 4 weeks, the torque was significantly higher in the 2-w rotation group (1.30+/-0.44 N cm) than in the control group (0.79+/-0.67 N cm). From 8 to 16 weeks, the strained groups showed no significant differences from the control group. From the bone contact rates, bone formation was larger in the 4-week rotation group (62.9+/-10.7%) than in the control group (42.1+/-17.9%) at 8 weeks. The 4-week rotation group showed higher bone contact rate (61.1+/-11.3%) compared with the other strained groups and maintained this higher value until 16 weeks, showing no significant difference from the control group (72+/-5.2%). At the implant-bone interface, OPN was widely distributed and OCN was detected at a low level; however, ON could not be observed in any group. CONCLUSIONS: The bone contact rate changed when rotational strain was exerted at different periods after implant placement. However, the removal torque and distribution of extracellular matrix proteins were not adversely affected by the rotational strain.

Animals↗

Hypertrophic chondrocytes. The terminal stage of differentiation in the chondrogenic cell lineage?

Chondrocytes emerging in the limb or other locations during embryogenesis are currently considered terminally differentiated cells and thus represent the last stage of differentiation in the chondrogenic cell lineage. Most chondrocytes, however, undergo further major phenotypic changes during late embryogenesis and early postnatal life as they take part in the endochondral ossification process. During this process, "resting" chondrocytes first enter an active, proliferative phase and then develop into large, round hypertrophic chondrocytes with unique phenotypic traits. The question thus arises as to whether hypertrophic chondrocytes actually represent the terminal stage of differentiation in the chondrogenic lineage. To assess the developmental position of these cells along the lineage, we examined the expression of four genes encoding extracellular matrix components in chondrocytes undergoing endochondral ossification in chicken tibial growth cartilage. We found that the steady-state levels of mRNAs coding for proteoglycan core protein increased in regions of cartilage destined for endochondral ossification. Similarly, type II collagen gene expression increased markedly in proliferating chondrocytes and then returned to basal levels in hypertrophic chondrocytes. As revealed by in situ hybridization, type X collagen gene expression was undetectable in resting and early proliferating chondrocytes and was detectable in hypertrophic chondrocytes. Osteonectin synthesis appeared to characterize chondrocytes in the resting, proliferating, and hypertrophic zones of growth cartilage. The protein was scarce, however, and cell-associated in the former zones, although it was very abundant and matrix-associated in the hypertrophic zone. Clearly, the emergence of hypertrophic chondrocytes during endochondral ossification is accompanied by marked quantitative and qualitative changes in gene expression. Interestingly, these changes occur during or immediately after the period of active chondrocyte proliferation. On the premises of the cell lineage definition proposed by Holtzer, the above data suggest that the hypertrophic chondrocytes represent the terminal stage of differentiation in the chondrogenic cell lineage.

Animals↗

Expression of bone-regulatory proteins in human valve allografts.

OBJECTIVE: To test the hypothesis that valve allograft (VA) calcification results from an ossification process in which bone-regulatory proteins are expressed. METHODS: 15 VA that were explanted at the time of surgery for dysfunction were studied. VA were analysed and compared with normal aortic valves (n = 20). RESULTS: All the VA (5 aortic, 10 pulmonary) exhibited heavy calcification and important fibrosis. Immunohistochemistry studies showed that the bone-specific transcription factor Cbfa-1 was expressed by stromal cells. Bone alkaline phosphatase was expressed in calcified regions. Immunostaining for alpha smooth muscle (alpha-SM) actin was increased in VA compared with normal valves and in 6 of the 15 valves formed cellular clusters close to the calcified nodules. In VA osteopontin and osteonectin were expressed by stromal cells, whereas osteocalcin was closely associated with the calcified regions. Furthermore, analysis of the bone-regulatory proteins that control bone resorption showed that receptor activator of nuclear factor kappaB ligand (RANKL), receptor activator of nuclear factor kappaB (RANK) and osteoprotegerin (OPG) were differentially expressed in calcified VA and normal valves. Normal valve leaflets expressed OPG, whereas OPG expression was absent or faint in calcified VA. RANKL and RANK were not detected in normal valves, whereas calcified VA expressed RANKL and RANK. CONCLUSION: These data suggest that calcification of VA results from an ossification process, which relies on tight control of bone-regulatory protein expression. The expression pattern of the RANKL/RANK/OPG system suggests that it may have a regulatory role not only in osteoclastogenesis but also in the calcification of human VA.

Actins↗

Expression profiling of purified normal human luminal and myoepithelial breast cells: identification of novel prognostic markers for breast cancer.

The normal duct-lobular system of the breast is lined by two epithelial cell types, inner luminal secretory cells and outer contractile myoepithelial cells. We have generated comprehensive expression profiles of the two normal cell types, using immunomagnetic cell separation and gene expression microarray analysis. The cell-type specificity was confirmed at the protein level by immunohistochemistry in normal breast tissue. New prognostic markers for survival were identified when the luminal- and myoepithelial-specific molecules were evaluated on breast tumor tissue microarrays. Nuclear expression of luminal epithelial marker galectin 3 correlated with a shorter overall survival in these patients, and the expression of SPARC (osteonectin), a myoepithelial marker, was an independent marker of poor prognosis in breast cancers as a whole. These data provide a framework for the interpretation of breast cancer molecular profiling experiments, the identification of potential new diagnostic markers, and development of novel indicators of prognosis.

Breast↗

Alterations in vascular gene expression in invasive breast carcinoma.

The molecular signature that defines tumor microvasculature will likely provide clues as to how vascular-dependent tumor proliferation is regulated. Using purified endothelial cells, we generated a database of gene expression changes accompanying vascular proliferation in invasive breast cancer. In contrast to normal mammary vasculature, invasive breast cancer vasculature expresses extracellular matrix and surface proteins characteristic of proliferating and migrating endothelial cells. We define and validate the up-regulated expression of VE-cadherin and osteonectin in breast tumor vasculature. In contrast to other tumor types, invasive breast cancer vasculature induced a high expression level of specific transcription factors, including SNAIL1 and HEYL, that may drive gene expression changes necessary for breast tumor neovascularization. We demonstrate the expression of HEYL in tumor endothelial cells and additionally establish the ability of HEYL to both induce proliferation and attenuate programmed cell death of primary endothelial cells in vitro. We also establish that an additional intracellular protein and previously defined metastasis-associated gene, PRL3, appears to be expressed predominately in the vasculature of invasive breast cancers and is able to enhance the migration of endothelial cells in vitro. Together, our results provide unique insights into vascular regulation in breast tumors and suggest specific roles for genes in driving tumor angiogenesis.

Blood Vessels↗

Gene expression profiling and genetic markers in glioblastoma survival.

Despite the strikingly grave prognosis for older patients with glioblastomas, significant variability in patient outcome is experienced. To explore the potential for developing improved prognostic capabilities based on the elucidation of potential biological relationships, we did analyses of genes commonly mutated, amplified, or deleted in glioblastomas and DNA microarray gene expression data from tumors of glioblastoma patients of age >50 for whom survival is known. No prognostic significance was associated with genetic changes in epidermal growth factor receptor (amplified in 17 of 41 patients), TP53 (mutated in 11 of 41 patients), p16INK4A (deleted in 15 of 33 patients), or phosphatase and tensin homologue (mutated in 15 of 41 patients). Statistical analysis of the gene expression data in connection with survival involved exploration of regression models on small subsets of genes, based on computational search over multiple regression models with cross-validation to assess predictive validity. The analysis generated a set of regression models that, when weighted and combined according to posterior probabilities implied by the statistical analysis, identify patterns in expression of a small subset of genes that are associated with survival and have value in assessing survival risks. The dominant genes across such multiple regression models involve three key genes-SPARC (Osteonectin), Doublecortex, and Semaphorin3B-which play key roles in cellular migration processes. Additional analysis, based on statistical graphical association models constructed using similar computational analysis methods, reveals other genes which support the view that multiple mediators of tumor invasion may be important prognostic factor in glioblastomas in older patients.

Aged↗

Quantitative analysis of extracellular matrix proteins in hypertrophic layers of the mandibular condyle and temporal bone during human fetal development.

A computer image analysis of immunostained extracellular matrix (ECM) proteins (collagen types I, II, III and V, fibronectin and tenascin) in hypertrophic layers in the mandibular condyle and temporal bone of human fetuses, which ranged in gestational age from 12 to 32 weeks, was performed. The percentage of cells positive for proliferating cell nuclear antigen (PCNA) increased in almost the same manner in each region. The level of PCNA was markedly elevated at 16 weeks. The percentage of PCNA-positive cells was low in temporal bone and in the bone-forming layer of the mandibular condyle at 24 weeks. Specific concentration patterns of proteins in the ECM were found at each stage of development. The extent of accumulation of fibrillar collagen and of fibronectin differed, while those of other proteins in the ECM, such as tenascin, osteocalcin and osteonectin, were similar at the two sites.

Bone Density↗

Stimulation of motility of human renal cell carcinoma by SPARC/Osteonectin/BM-40 associated with type IV collagen.

SPARC is known to be important in development and tissue remodelling. Here, we examined the effects of SPARC (secreted protein, acidic and rich in cysteine; osteonectin) derived from a rat osteosarcoma cell line on migration of renal cell carcinoma (RCC) by a Boyden chamber assay. YCR RCC cells migrated through type IV collagen-coated filters without stimuli (basal level). SPARC in the lower compartment stimulated chemotactic activity to 120% of the basal level, whereas premixing of YCR with purified SPARC before inoculation reduced their migration to 72% of the basal level. Furthermore, SPARC mixed with type IV collagen more efficiently stimulated their migration in a concentration-dependent manner (up to 170% of the basal level). This suggests that SPARC bound to type IV collagen plays a role in tumor invasion.

Animals↗

Collagen type I increases bone remodelling around hydroxyapatite implants in the rat tibia.

The early interface reaction of cancellous bone to a nanocrystalline hydroxyapatite (HA) cement containing 3 wt% collagen type I (HA/Coll) with a setting under physiological temperature and pH was observed using immunohistochemical techniques. Pure HA served as a control. Cylinders with a diameter of 2 mm were implanted into the proximal tibia of 72 adult Wistar rats. Histological sections of 6 animals were prepared after 1, 2, 4, 6, 14 and 28 days. First, osteoblast-like cells as well as a marked reaction for osteonectin, osteopontin and its ligand CD44 were observed as early as 2 days after implantation at the interface around HA/Coll implants. Further, reactivity for ED1 and cathepsin D, both markers for phagocytotic cells, appeared earlier and stronger around HA/Coll. In cell counts, a significantly higher average number of ED1- and cathepsin D-positive phagocytotic cells was observed around the HA/Coll implants on days 6 (p < 0.01), 14 and 28 (p < 0.05). The number of osteopontin-positive cells was significantly higher around HA/Coll implants at days 6 and 14 (p < 0.05). Two weeks after the implantation, first islands of newly formed woven bone were observed around the HA/Coll implant, but not around the control implant. The amount of direct bone contact after 28 days averaged 28% around pure HA and 51% around HA/Coll implants (p < 0.05). While both implants displayed a good osteoconductivity, a higher bone remodelling activity was observed around collagen-containing HA implants compared to pure HA implants. It appears that the addition of collagen to HA implants can enhance both phagocytotic and osteogenic processes. This may result in an earlier acceptance and better osseointegration of the HA/Coll implants into the surrounding tissue.

Animals↗

Osteo/chondrocytic transcription factors and their target genes exhibit distinct patterns of expression in human arterial calcification.

OBJECTIVE: Mineralization-regulating proteins are found deposited at sites of vascular calcification. However, the relationship between the onset of calcification in vivo and the expression of genes encoding mineralization-regulating proteins is unknown. This study aimed to determine the temporal and spatial pattern of expression of key bone and cartilage proteins as atherosclerotic calcification progresses. METHODS AND RESULTS: Using reverse transcription-polymerase chain reaction on a panel of noncalcified and calcified human arterial samples, two classes of proteins could be identified: (1) Matrix Gla protein, osteonectin, osteoprotegerin, and aggrecan were constitutively expressed by vascular smooth muscle cells (VSMCs) in the normal vessel media but downregulated in calcified arteries whereas (2) alkaline phosphatase, bone sialoprotein, osteocalcin, and collagen II were expressed predominantly in the calcified vessel together with Cbfa1, Msx2, and Sox9, transcription factors that regulate expression of these genes. In the calcified plaque in situ hybridization identified subsets of VSMCs expressing osteoblast and chondrocyte-like gene expression profiles whereas osteoclast-like macrophages were present around sites of calcification. CONCLUSIONS: These observations suggest a sequence of molecular events in vascular calcification beginning with the loss of expression by VSMCs, of constitutive inhibitory proteins, and ending with expression by VSMCs and macrophages of chondrocytic, osteoblastic, and osteoclastic-associated proteins that orchestrate the calcification process.

Calcinosis↗

Alterations of bone matrix protein mRNA expression in rat aorta in vitro.

We examined the expression of matrix Gla protein (MGP), osteopontin (OPN), and osteonectin (ON) mRNAs in aortic rings excised from 3-month-, 10-month-, and 2-week-old rats during 72-hour incubations in serum-free media. In the aortic rings from 3-month-old rats, the expression of MGP mRNA was strong before incubation and increased during the 72-hour incubation. The expression of OPN mRNA was first detected after a 5-hour incubation and increased thereafter, and that of ON mRNA was strong before the incubation and decreased during the incubation. The expression of MGP and OPN mRNAs in 10-month- and 2-week-old rats was similar to that in 3-month-old rats. In contrast, expression of ON mRNA in 10-month-old rats and the expression of ON mRNA in 2-week-old rats was stronger than that in 3-month-old rats at every incubation period. In situ hybridization and immunohistochemistry identified the MGP, OPN, and ON mRNA-expressing cells as vascular smooth muscle cells. These results suggest that the expression of these mRNAs was regulated in incubation time-dependent and age-specific ways. We believe that this organ culture model is useful for further studies of the function of these bone matrix proteins and regulation of their expression in the vessel wall.

Animals↗

Effect of a derivatized dextran on human osteoblast growth and phenotype expression.

Water soluble derivatized dextran named E9 with a molecular weight of 45,000 g l-1 containing 58% methyl carboxylic acid unit, 19% benzylamide unit, and 26% sulfonate with a specific anticoagulant activity of 0.29 IU mg-1 was studied for its effects on human osteoblast growth and phenotype expression for short-term treatment. At concentrations between 1 ng ml-1 and 1 microgram ml-1 E9 has no effect on DNA synthesis whereas at higher concentrations DNA synthesis is inhibited in a dose related fashion (87% for 400 micrograms ml-1). For concentrations which do not modify osteoblast growth, E9 promotes alkaline phosphatase activity, type I collagen and osteocalcin synthesis with a maximum effect for 0.1-1 microgram ml-1. It has a synergistic effect with hPTH increasing AMPc. Moreover, osteonectin synthesis was enhanced in a dose-dependent manner between 0.1 and 5 micrograms ml-1. These results seem to indicate that E9 is able to stimulate human osteoblast phenotype expression and could be useful in clinical applications.

Adult↗