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T Aigner

Publications and source records attributed to T Aigner.

At least 91 records · Page 5Linked to original sources
PubMed1997

Type X collagen expression and hypertrophic differentiation in chondrogenic neoplasias.

Little is known about matrix biochemistry and cell differentiation patterns in chondrogenic neoplasms. This is the first description of the focal expression of collagen type X by neoplastic chondrocytes in situ and its incorporation into the extracellular matrix of cartilaginous tumors. This shows that neoplastic chondrocytes have the potential to undergo the full program of cell differentiation, including hypertrophy, comparable to their physiological counterparts in the growth plate. However, only in benign osteochondromas was a zonal expression of type X collagen found similar to that observed in the growth plate, where the cells immediately above the ossification frontier are selectively positive for type X collagen. In enchondromas and chondrosarcomas, the expression was randomly distributed within the tumors. Surprisingly, in less differentiated chondrosarcomas with spindle-shaped cells and non-cartilaginous extracellular matrix, exceptional expression of collagen type X was observed, which indicates potential uncoupling of collagen type X expression from the differentiated chondrocytic phenotype in neoplastic chondrocytes in vivo.

Bone Neoplasms↗
PubMed1997

Extracellular matrix composition and gene expression in collagenous colitis.

BACKGROUND & AIMS: Collagenous colitis is a rare diarrheal disease of unknown pathophysiology that is histologically defined by subepithelial bandlike structures. The objective of this study was to elucidate the biochemical composition and the origin of the bandlike structures in collagenous colitis. METHODS: Immunohistochemical and in situ hybridization analyses were performed on endoscopic specimens using specific antibodies and riboprobes for collagen types I, III, IV, and VI and for the glycoprotein tenascin. RESULTS: In collagenous colitis, the mucosal matrix with the exception of the bands retained a normal architecture and extracellular matrix composition. The bands stained most prominently for type VI collagen and tenascin. Less abundant staining for both proteins was also found in the subepithelial matrix of the normal mucosa. In situ hybridization showed no significant increase in collagen type VI messenger RNA expression in cells around and entrapped in the bands in collagenous colitis compared with normal specimens. CONCLUSIONS: The results support the suggestion that collagenous colitis is a localized alteration of the extracellular matrix, which involves the pericryptal-subepithelial myofibroblast sheath. The data suggest that reduced matrix degradation and not overactivation of matrix synthesis may be the reason for the subepithelial accumulation of matrix proteins.

Adult↗
PubMed1997

Activation of fibrillar collagen synthesis and phenotypic modulation of chondrocytes in early human osteoarthritic cartilage lesions.

The objective of this study was to investigate the expression and extracellular distribution of fibrillar collagen types I, II, and III in early stage osteoarthritic cartilage in order to elucidate matrix gene expression and cell differentiation in early phases of the disease. Arthroscopically, derived specimens of early stage osteoarthritic articular cartilage were analyzed by histochemistry, immunohistochemistry and by in situ hybridization and compared with normal articular cartilage samples. In normal articular cartilage no significant mRNA expression of any of the investigated collagen types was found. In early stage osteoarthritic specimens, a strongly enhanced mRNA expression of the major cartilage matrix component type II collagen was detected. Additionally, a focal onset of type III, but not type I collagen expression was observed. Thus, besides activation of matrix synthesis, the modulation of the chondrocytic phenotype is likely to play a distinct role in the cellular response in the early phases of the degenerative process in osteoarthritis.

Adult↗
PubMed1997

Phenotypic diversity of neoplastic chondrocytes and extracellular matrix gene expression in cartilaginous neoplasms.

Chondrocyte differentiation is characterized by distinct cellular phenotypes, which can be identified by specific extracellular matrix gene expression profiles. By applying in situ analysis on the mRNA and protein level in a series of benign and malignant human chondrogenic neoplasms, we were able to identify for the first time different phenotypes of neoplastic chondrocytes in vivo: 1) mature chondrocytes, which synthesized the characteristic cartilaginous extracellular tumor matrix, 2) cells resembling hypertrophic chondrocytes of the fetal growth plate, 3) cells resembling so-called dedifferentiated chondrocytes, and 4) well differentiated chondrocytic cells, which expressed type I collagen, indicating the presence of post-hypertrophic differentiated neoplastic chondrocytes. Chondrocytes exhibiting a range of phenotypes were found to be present in the same neoplasm. The different observed phenotypes, including the dedifferentiated phenotype, were in contrast to the anaplastic cells of high-grade chondrosarcomas. Comparison of expression data with tumor morphology revealed a relationship between the cellular phenotypes, the tumor matrix composition, and the matrix and cell morphology within the neoplasms. The distinctly different phenotypes of neoplastic chondrocytes are the basis of the characteristic high biochemical and morphological heterogeneity of chondroid neoplasms and shed light on their biological and clinical behavior.

Aggrecans↗
PubMed1996

Identification and immunolocalization of laminin in cartilage.

In a previous study on the role of integrins in the interaction of human chondrocytes with extracellular collagen and fibronectin (Dürr et al., (1993) Exp. Cell Res. 207, 235) we showed that chondrocytes adhere to laminin-1 (LN-1) in a beta 1-integrin-dependent manner. FACS analysis with various integrin antibodies including the monoclonal antibody GOH3 indicated the presence of the alpha 6 beta 1-laminin receptor on the chondrocyte surface. Anti-alpha 6 antibodies inhibited adhesion to the LN-1/E8 fragment, but not to whole laminin or heat-denatured Laminin-1, indicating that chondrocytes utilize at least two beta 1-integrins for laminin adhesion, one of which is alpha 6 beta 1 recognizing the LN-1/E8 fragment. The presence of alpha 6 beta 1-integrin on the chondrocyte surface also suggested the existence of laminin-like molecules in cartilage. Here we provide immunological and biochemical evidence in support of this possibility. Several polyclonal antibodies raised against laminin-1 or the LN-1/E8 fragment revealed a strong pericellular reaction in sections of human fetal epiphyseal cartilage and adult articular cartilage. In the fetal epiphysis laminin staining was most prominent in mature, large chondrocytes appearing in the secondary ossification zone, in particular, in the vicinity of invading capillary sprouts. Chondrocytes in the proliferating and hypertrophic zone of the growth plate and perichondrium cells were negative. All chondrocytes that stained for alpha 6-integrin also stained for laminin-1. A laminin-1-like molecule was extracted from hyaline cartilage with two bands migrating slightly faster than the alpha 1 and beta 1/gamma 1 subunits of laminin on SDS-gel electrophoresis. The two bands stained with anti-laminin-1 antibodies and could be immunoprecipitated with the same antibodies from metabolically labeled chondrocyte cultures. These findings suggests a role for laminin in developing cartilage and thus additional roles for laminins outside basement membranes.

Adult↗
PubMed1996

Chondrocytic cell differentiation in clear cell chondrosarcoma.

Clear cell chondrosarcoma is a rare mesenchymal neoplasm of unclear differentiation. Besides having a chondrogenic nature, an osteogenic differentiation was also proposed. In this study, expression analysis of extracellular matrix genes, which are specific for different mesenchymal cell differentiation pathways, were used to get a better understanding of origin and differentiation pattern of the clear cell chondrosarcoma tumor cells. Our in situ analysis of two cases shows that (1) chondrocytic cell differentiation as marked by the expression of cartilage collagen type II and proteoglycans is a characteristic feature within the development of the neoplasm, (2) multifocal chondrocyte hypertrophy as shown by the expression of type X collagen does occur, and (3) no significant expression of collagen type I, the main gene product of osteoblastic cells, is found by the neoplastic cells. Thus, our study indicates that clear cell chondrosarcoma shows a chondrogenic, but not osteogenic, differentiation and represents a true chondrosarcoma. The unusual scarcity of its extracellular and the multifocal expression of type X collagen marks clear cell chondrosarcoma as a chondrosarcoma tumor entity of a particular cell differentiation pattern. The expression of cartilage type collagens represents a distinct marker from bone metastases of clear cell neoplasms of other origins.

Adult↗
PubMed1996

Immunolocalization of type X collagen in normal fetal and adult osteoarthritic cartilage with monoclonal antibodies.

For studies on processing and tissue distribution of type X collagen, monoclonal antibodies were prepared against human recombinant collagen type X (hrCol X) and tested by ELISA, immunoblotting and immunohistology. Forty-two clones were obtained which were grouped into four different subsets based on their reactivity against native and denatured hrCol X, pepsin-treated hrCol X, and the C-terminal NC-1 domain. Here we present results obtained with four monoclonal antibodies: Clone X 53, a representative of group I, binds with high affinity to both native and pepsin-digested hrCol X but with low affinity to the NC-1 dimer; monoclonal antibodies of group II and III recognized native and denatured hrCol X but not NC-1; antibodies of group II, but not III, reacted to some extent with pepsin treated hrCol X; one antibody (X 34) was obtained that reacted strongly with the isolated NC-1 dimer and native hrCol X but not with the NC-1 monomer or pepsin-digested hrCol X (group IV). Antibodies of all groups stained specifically the hypertrophic zone of fetal human epiphyseal cartilage. Mab X 53 stained the peri- and extracellular matrix of hypertrophic chondrocytes in the lower hypertrophic zone and in the calcified cartilage core in endochondral bone trabecules, while clone X 34 stained intracellularly and the pericellular matrix. All other tissues or cells of the epiphysis were negative. Antibody X 53 reacted also with canine, murine and guinea pig hypertrophic cartilage in tissue sections, but not with bovine or porcine type X collagen. In sections of osteoarthritic cartilage, clusters of hypertrophic chondrocytes in the deep zone were stained, confirming previous observations on enhanced chondrocyte hypertrophy and type X collagen expression in osteoarthritic articular cartilage.

Adult↗
PubMed1996

Expression of collagen types IX and XI and other major cartilage matrix components by human fetal chondrocytes in vivo.

Coordinate differentiation of the chondrocytes plays a crucial role during skeletal development. In the cascade of endochondral bone formation, mature chondrocytes of the fetal growth plate represent metabolically highly active cells. They show high expression levels of the major cartilage matrix genes, collagen types II, IX, and XI, the major cartilage proteoglycan aggrecan, and proteoglycan link protein. The strongest signals are found in areas of maximal growth, the proliferative and upper hypertrophic zones. The major cartilage matrix components are co-expressed by the chondrocytes of the resting and proliferative zones. Type X collagen is restricted to lower hypertrophic chondrocytes. Interestingly, in the lower hypertrophic zone type IX collagen, but not type II and XI collagen, mRNA expression is downregulated, indicating a discoordinate expression of these collagen types in hypertrophic chondrocytes. The results of this study confirm the strict zonal differentiation pattern of chondrocytes in the developing fetal growth plate, which can be monitored by the expression patterns of its major expression products, the collagen subtypes and aggrecan and proteoglycan link protein.

Cartilage↗
PubMed1996

[Inflammatory cytokine mediated anti-anabolic effects: a potential mechanism in rheumatoid cartilage degeneration].

Increased levels of inflammatory cytokines such as II-1 and TNF-alpha are described in rheumatoid and osteoarthritic synovial fluid. These mediators are also very well established anti-anabolic modulators of chondrocyte synthetic activity in vitro. Our study aimed to investigate, whether chondrocytes in rheumatoid and osteoarthritic cartilage in situ show reaction pattern compatible with the putative effects of these modulatory agents. Immunohistochemical analysis using type II collagen specific antibodies showed considerable loss of staining in many sites of osteoarthritic and rheumatoid articular cartilage. mRNA analysis showed besides an overall activation of synthetic activity in rheumatoid and osteoarthritic cartilage, a decreased expression of cartilage matrix proteins in the upper zone. The cease of the anabolic activity of rheumatoid and osteoarthritic chondrocytes and the increased catabolism of matrix components contributes to the anabolic-catabolic imbalance in rheumatoid and osteoarthritic cartilage and is suggestive to be a crucial event in the progress of the disease. It correlates well to the putative anti-anabolic effect of inflammatory cytokines such as II-1 and TNF-alpha and could indicate a potential role of these mediators in rheumatoid and osteoarthritic cartilage destruction.

Arthritis, Rheumatoid↗
PubMed1995

Osteogenic differentiation of hypertrophic chondrocytes involves asymmetric cell divisions and apoptosis.

We have investigated the early cellular events that take place during the change in lineage commitment from hypertrophic chondrocytes to osteoblast-like cells. We have induced this osteogenic differentiation by cutting through the hypertrophic cartilage of embryonic chick femurs and culturing the explants. Immunocytochemical characterization, [3H]thymidine pulse-chase labeling, in situ nick translation or end labeling of DNA breaks were combined with ultrastructural studies to characterize the changing pattern of differentiation. The first responses to the cutting, seen after 2 d, were upregulation of alkaline phosphatase activity, synthesis of type I collagen and single-stranded DNA breaks, probably indicating a metastable state. Associated with the change from chondrogenic to osteogenic commitment was an asymmetric cell division with diverging fates of the two daughter cells, where one daughter cell remained viable and the other one died. The available evidence suggests that the viable daughter cell then divided and generated osteogenic cells, while the other daughter cell died by apoptosis. The results suggest a new concept of how changes in lineage commitment of differentiated cells may occur. The concepts also reconcile previously opposing views of the fate of the hypertrophic chondrocyte.

Alkaline Phosphatase↗
PubMed1995

Immunolocalization of type III collagen in human articular cartilage prepared by high-pressure cryofixation, freeze-substitution, and low-temperature embedding.

We localized Type III collagen by immunogold electron microscopy in resin sections of intact normal and osteoarthritic human articular cartilage. Comparisons of antibody staining between tissue prepared by high-pressure cryofixation and freeze-substitution without fixatives and that exposed to conventional mild chemical fixation with paraformaldehyde showed that dedicated cryotechniques yielded superior preservation of epitopes that are modified by chemical fixation, and simultaneously provided good ultrastructural preservation. Type III collagen was detected with two polyclonal antibodies, one against the triple-helical domain of the molecule and a second against the more antigenic, globular amino pro-peptide domain, which in this collagen is retained in the extracellular matrix after secretion. Positive labeling was seen in association with the major interstitial fibrils, suggesting co-polymerization of Types III and II collagen in cartilage. Type III collagen could not be detected in aldehyde-fixed normal cartilage. In fixed osteoarthritic cartilage, Type III was detectable only when the antibody to the amino pro-peptide was employed. In contrast, high-pressure cryofixation and freeze-substitution preserved epitopes for both antibodies, permitting immunodetection of Type III collagen in normal and osteoarthritic cartilage. Cryotechniques offer exciting possibilities for significantly improving the immunolocalization of collagens and other fixative-sensitive antigens in situ.

Cartilage, Articular↗
PubMed1995

Synovial fibroblast-like cells strongly express jun-B and C-fos proto-oncogenes in rheumatoid- and osteoarthritis.

To identify recently activated cells in the synovial membrane (SM) of patients with rheumatoid arthritis (RA), the in situ expression of the proto-oncogenes jun-B, c-jun, jun-D, and c-fos was assessed by means of immunohistochemistry and in situ hybridization techniques. SM from patients with osteoarthritis (OA) or joint trauma (JT), as well as from normals (No) were used as controls. Numerous cells expressing high levels of jun-B and c-fos were found within lining layer and diffuse infiltrates in the vicinity of inflammatory cells, but only a few in lymphoid follicles and endothelia. The positive cells were spindle-shaped, CD14- and CD3-negative and, in addition, expressed mRNA for collagen alpha 2 (I) and alpha 1 (III), indicating that they were fibroblasts. In control OA, JT, and even No SM, individual fibroblast-like cells stained as strongly as in RA; however, the density of positive cells was substantially lower. In RA SM, fibroblasts, but not lymphocytes or macrophages, appear to undergo in situ activation. Quantitative differences among RA, OA, and JT may be related to different degrees of inflammatory infiltration.

Arthritis, Rheumatoid↗
PubMed1995

Chondrocytes and antirheumatic drugs.

Effects of antirheumatic drugs upon cartilage matrix metabolism have been studied in a variety of chondrocyte in vitro systems. When compared longterm in 60 experiments under standardized conditions, articular chondrocytes cultured in agarose exhibit variability in proteoglycan synthesis, and its suppression by interleukin 1 (IL-1), but a high reproducibility in the modulation of these effects by antirheumatic drugs. Pentosan polysulfate, tenidap, tiaprofenic acid, and RO 31-9790 all compensated to a certain extent the IL-1 induced suppression of matrix synthesis in bovine chondrocytes, but only for tiaprofenic acid could this be confirmed using chondrocytes of human origin. Culture conditions as well as species differences should therefore be considered carefully when chondrocyte cultures are used as pharmacological models.

Animals↗
PubMed1995

Differential expression of collagen types I, II, III, and X in human osteophytes.

BACKGROUND: Osteophytes are neoplastic cartilaginous and osseous protrusions growing at the margins of osteoarthritic joints. Their formation involves complex patterns of cellular proliferation, differentiation, as well as matrix synthesis and turnover that are poorly understood. EXPERIMENTAL DESIGN: Here we report on an experimental approach using in situ hybridization and immunohistology to elucidate pathways of chrondrocyte differentiation in human osteophytes. Ab and cDNA probes for collagen types were used as specific parameters for chondrocyte phenotypes. RESULTS: In early precartilaginous mesenchymal tissue, cytoplasmic mRNA for alpha 1(I) and alpha 1(III) collagen genes (Col1A1 and Col3A1) were found by in situ hybridization, correlating with the distribution of type I and III collagen as revealed by Ab staining. Strong expression of type II collagen both at mRNA and protein levels was the hallmark of chondrogenic differentiation in the cartilaginous zone of osteophytes. Type II collagen expression increased in all cartilaginous and fibrocartilaginous areas with growth and maturation of osteophytes. The signal intensity obtained after in situ hybridization with a COL2A1 probe was high and corresponded to that obtained in fetal cartilage, whereas normal adult articular cartilage usually did not show measurable type II collagen expression. In fibrocartilaginous areas, the most abundant, but heterogeneous tissue type seen in osteophytes, type II and III collagen mRNA expression overlapped considerably. Type III collagen was scattered, both pericellularly and interterritorially, over the whole osteophyte, excluding bone and chondrocytic cells of the deep zone. The strongest type I collagen expression was seen in bone and in the superficial fibrous layer. In areas of endochondral ossification, large chondrocytes were found expressing type X collagen, a specific marker for hypertrophic chondrocytes. CONCLUSIONS: These results show that discrete stages of cartilage differentiation can be precisely followed in osteophytes using collagen type-specific cDNA probes and Ab as markers. In addition, a fibrocartilaginous chondrocyte phenotype was identified that expresses type II and III, but not type I collagen.

Aged↗
PubMed1994

Transcriptional and translational regulation of IL-1 alpha and IL-1 beta account for the control of IL-1 in experimental yersiniosis.

Interleukin 1 (IL-1) gene expression was investigated in mice following oral infection with Yersinia enterocolitica 08. In Peyer's patches (PP), the primary site of bacterial invasion, induction of IL-1 alpha mRNA was delayed when compared to IL-1 beta mRNA. As shown by in situ hybridization. IL-1 alpha and IL-1 beta mRNA were found to be expressed within different cell types. These results indicate that expression of the two forms of IL-1 is regulated in a cell-specific manner at the transcriptional level. Moreover, IL-1 (alpha and beta) mRNA was increased in other organs such as spleen and lung. In spleens, IL-1 beta mRNA was found within the red pulp, and IL-1 alpha mRNA was located to the marginal zone confirming that differential expression of IL-1 alpha and IL-1 beta mRNA does not represent a tissue-specific event. However, as revealed by immunohistochemistry and measuring IL-1 activity in tissue homogenates, synthesis of IL-1 proteins was not detectable in spleens, unless mice were challenged with LPS. Because IL-1 synthesis was inducible in spleen cells following actinomycin D treatment, the results indicate that at distant sites of infection IL-1 (alpha and beta) mRNA is expressed but not translated into protein. It is concluded that cell-specific transcription of IL-1 alpha and IL-1 beta as well as dissociation between IL-1 mRNA and protein synthesis are two mechanisms effective in regulating the production of IL-1 during infection.

Animals↗
PubMed1993

Alterations of collagen mRNA expression during retinoic acid induced chondrocyte modulation: absence of untranslated alpha 1(I) mRNA in hyaline chondrocytes.

Retinoic acid (RA) has been shown to rapidly modulate the collagen expression pattern of chondrocytes in vitro at doses of 1-10 microM. Embryonic chicken sternal chondrocytes stop synthesizing the cartilage-specific type II collagen within 2-4 days of RA treatment and turn on the synthesis of types I and III collagen and fibronectin. While suppression of type II collagen synthesis and onset of type III collagen and fibronectin synthesis have been shown to be regulated at the transcriptional level, conflicting data are available on a possible post-translational regulation of alpha 1(I) collagen gene expression. In this study we demonstrate by comparing a commonly used alpha 1(I) cDNA probe from the 3' end of the alpha 1(I) mRNA with a newly prepared alpha 1(I) cDNA probe from the 5' end (p1E1) that--in contrast to previous reports--chicken sternal chondrocytes do not contain untranslated alpha 1(I) mRNA which may become translatable after RA treatment. By in situ hybridization we show the absence of cytoplasmic alpha 1(I) mRNA from chondrocytes and its presence in the perichondrium of sternal cartilage. Perichondral cells might have contaminated sternal chondrocyte preparations, explaining low levels of alpha 1(I) mRNA seen by Northern hybridization and RNase protection assays of chicken sternal cartilage mRNA even with the p1E1 probe. We show by Northern hybridization and metabolic labeling with 3H-proline followed by SDS-gel electrophoresis that retinoic acid at 3 microM suppresses type II, IX, and X collagen gene expression within 2 days both at the mRNA and protein level and induces the onset of alpha 1(I), alpha 2(I), and alpha 1(III) expression within 3 days. No expression of CRABP, the cellular retinoic acid binding protein, was seen in RA-treated or control chondrocytes, indicating that CRABP protein is not involved in the RA-induced modulation of the chondrocytes.

Animals↗