Biomedical subjects

T Aigner

Publications and source records attributed to T Aigner.

105 records · Page 6Linked to original sources

PubMed1993

Type X collagen expression in osteoarthritic and rheumatoid articular cartilage.

Type X collagen is a short chain, non-fibril-forming collagen synthesized primarily by hypertrophic chondrocytes in the growth plate of fetal cartilage. Previously, we have also identified type X collagen in the extracellular matrix of fibrillated, osteoarthritic but not in normal articular cartilage using biochemical and immunohistochemical techniques (von der Mark et al. 1992a). Here we compare the expression of type X with types I and II collagen in normal and degenerate human articular cartilage by in situ hybridization. Signals for cytoplasmic alpha 1(X) collagen mRNA were not detectable in sections of healthy adult articular cartilage, but few specimens of osteoarthritic articular cartilage showed moderate expression of type X collagen in deep zones, but not in the upper fibrillated zone where type X collagen was detected by immunofluorescence. This apparent discrepancy may be explained by the relatively short phases of type X collagen gene activity in osteoarthritis and the short mRNA half-life compared with the longer half-life of the type X collagen protein. At sites of newly formed osteophytic and repair cartilage, alpha 1(X) mRNA was strongly expressed in hypertrophic cells, marking the areas of endochondral bone formation. As in hypertrophic chondrocytes in the proliferative zone of fetal cartilage, type X collagen expression was also associated with strong type II collagen expression.

Arthritis, Rheumatoid↗

PubMed1993

Independent expression of fibril-forming collagens I, II, and III in chondrocytes of human osteoarthritic cartilage.

Normal and osteoarthritic human articular cartilage was investigated by in situ hybridization for expression patterns of the fibrillar collagens type I, II, and III to evaluate phenotypic changes of articular chondrocytes related to the disease. In 11 out of 20 samples, a defined subset of chondrocytes in the superficial and upper middle zone of osteoarthritic cartilage showed significant levels of cytoplasmic alpha 1 (III) mRNA, whereas strong signals of alpha 1 (II) mRNA were found in the upper and lower middle zone, partially overlapping with the zone of alpha 1 (III) mRNA-expressing cells. The extent of type II and III collagen expression depended on the integrity of the extracellular matrix surrounding the chondrocytes, and the location within the articular cartilage. No alpha 1 (I) mRNA was detectable in osteoarthritic original articular cartilage. The alpha 1 (I) probe did, however, reveal signals in pannus-like tissue, osteophytes, and bone cells. In normal articular cartilage, no detectable levels of cytoplasmic mRNA for alpha 1(I), alpha 2 (I), or alpha 1 (III) were seen. Using specific mono- and polyclonal antibodies, we found deposition of type III collagen but hardly any of type I collagen in the superficial zone of osteoarthritic cartilage that is consistent with the in situ hybridization results. These results indicate a phenotypic alteration in a defined subset of chondrocytes in conditions of diseased cartilage, expressing and synthesizing collagen type III independently from type I collagen, but in part simultaneously with type II collagen.

Adult↗

PubMed1992

The serine-protease inhibitor of cartilage matrix is not a chondrocytic gene product.

Human articular cartilage contains significant amounts of antileukoprotease, a cationic low-molecular-mass serine-protease inhibitor, which was originally purified from mucous secretions (synonym: secretory leukocyte proteinase inhibitor). As it was not known whether the inhibitor molecule is also synthesized locally, we investigated antileukoprotease gene expression in chondrocytes. No antileukoprotease-specific mRNA was detected in adult or foetal human chondrocytes by in situ hybridization, Northern-blot analysis or polymerase chain reaction. Concurrently, the chondrocytes remained unstained on immunohistology, whereas immunoreactive antileukoprotease was demonstrated in the cartilage matrix. By Northern-blot analysis, the antileukoprotease message was detected in the promyelocytic cell line HL60, the myelomonocytic cell line U937 and even in mature polymorphonuclear leukocytes from the peripheral blood of healthy donors. Immunoperoxidase staining of polymorphonuclear leukocytes for the antileukoprotease protein indicated that this cell is likely to be the physiological source of the inhibitor in serum. The results further suggest an accumulation of the inhibitor in the cartilage matrix.

Base Sequence↗

PubMed1992

Activation of collagen type II expression in osteoarthritic and rheumatoid cartilage.

In situ hybridization and immunohistochemical techniques were applied to investigate gene expression and extracellular deposition of collagen type II in normal, osteoarthritic and rheumatoid human articular cartilage. Normal cartilage showed an essentially even extracellular distribution of type II collagen with poly- and monoclonal antibodies, while only a few cells were positive for alpha 1(II) collagen mRNA. In situ hybridization of osteoarthritic and rheumatoid cartilage, however, showed strong enhancement of type II collagen gene expression; transcripts were observed predominantly in the upper middle zone of the articular cartilage while the upper layer was mostly negative and correlated with a zone of reduced proteoglycan staining. The elevated mRNA levels frequently coincided with pericellular immunostaining for type II collagen, indicative for enhanced synthesis of the protein. In two samples, however, pericellular loss of collagen type II staining was found despite positive cytoplasmic signals with the alpha 1(II) RNA probe, suggesting enhanced collagen destruction. Control hybridization with a probe for 18S rRNA revealed very few negative cells throughout both normal and arthritic cartilage samples, ruling out major cell necrosis in the specimens investigated. Thus, our observations identify sites of activated type II collagen synthesis in osteoarthritic cartilage that were predicted by previous biochemical studies and support the notion that damaged cartilage attempts to restore matrix by enhanced synthesis of its components.

Adolescent↗

PubMed1991

In situ hybridization studies on the expression of type X collagen in fetal human cartilage.

Type X collagen is a short, non-fibril-forming collagen restricted to the hypertrophic, calcifying zone of growth plate cartilage. It is developmentally regulated and found exclusively in hypertrophic cartilage. Here we report on the structure and distribution of human type X collagen based on the cloning of a PCR fragment covering 292 bp of the carboxy-terminal, non-triple-helical domain. Seventy-five percent of the sequence are identical to that of chicken type X collagen at nucleic acid level and 84% at amino acid level. This probe was used for in situ hybridization analyses of type X collagen expression in a human growth plate. Human fetal cartilage, which is different from the avian cartilage-bone transition zone, showed strong type X collagen expression confined to the lower hypertrophic zone of the growth plate. The upper zone of hypertrophic chondrocytes did not contain alpha 1(X) transcripts, indicating that type X collagen expression follows cellular hypertrophy. The distribution of type X collagen mRNA has been previously unreported in chondrocytes from zones of secondary ossification and in chondrocytes associated with endochondral bone trabecules containing calcified cartilage. In situ hybridization analyses with probes for type I and II collagen on consecutive sections indicated a spatial gradient in chondrocyte differentiation in the human epiphysis. Chondrocytes of low type II collagen expression in the resting zone are followed by proliferating columnar chondrocytes with strong type II collagen expression and a zone of hypertrophic chondrocytes synthesizing type X and type II collagen. In contrast to findings in avian growth cartilage in some of our samples of human epiphyseal cartilage hypertrophic chondrocytes continued to strongly express type II collagen down to the chondro-osseous junction. Transcripts of the alpha 2(I) collagen gene, however, were detected only in perichondrium, vascular cavities, and bone, but not in hypertrophic or any other chondrocytes. The above observations demonstrate that the isolation of the human type X collagen DNA will contribute to studies of pathways of chondrocyte differentiation in the mammalian growth plate.

Amino Acid Sequence↗

PubMed1982

Experimental studies of the abuse potential of d, l-glaucine. 1.5-phosphate in rhesus monkeys.

d-Glaucine is an alkaloid derived from Glaucium flavum, which is as effective as codeine as an antitussive. d, l-Glaucine. 1.5 phosphate is a synthetic compound related to d-glaucine. The ability of d, l-glaucine.1.5 phosphate to maintain responding in rhesus monkeys was assessed in 2 procedures. In the first responding was maintained under a fixed-ratio 10 schedule of codeine delivery during daily 3-hr sessions. When d, l-glaucine.1.5 phosphate (0.05-0.4 mg/kg) was substituted for codeine, responding was not maintained. In the second procedure, monkeys given 23-hr/day access to 0.5-1.0 mg/kg under a fixed-ratio schedule did not self-administer d,l-glaucine.1.5 phosphate above saline levels even after a 21-day period of programmed injections. Following the period of programmed injections, there were not signs of opiate withdrawal following the administration of naloxone. These results indicate that the abuse potential of d,l-glaucine.1.5 phosphate is low relative to codeine.

Animals↗

PubMed1981

Comparison of the reinforcing properties of cocaine and procaine in rhesus monkeys.

Previous studies have shown that a variety of local anesthetics including procaine are self-administered at high rates by rhesus monkeys. In the present study two rhesus monkeys were given a mutually exclusive choice between various doses of intravenous cocaine and procaine. In almost all comparisons cocaine was preferred even when the procaine dose was 16 times that of cocaine. Other measures of performance such as rate of responding did not vary systematically with preference. These data provide further support for the idea that rate of responding under simple schedules of drug delivery is an unreliable measure of relative reinforcing efficacy. In addition, the consistent preference for cocaine over procaine in monkeys suggests that the infrequent abuse of procaine by humans may be related to its low reinforcing efficacy relative to drugs such as cocaine.

Animals↗

PubMedDate not supplied

[Characterisation and differentiation of chondroblastomas and chondromyxoidfibromas - presence and expression of collagen types I and II].

AIM: Chondroblastomas and chondromyxoidfiibromas are rare benign skeletal neoplasms with reported overlapping histology. Aim of this study was to analyse the biochemical composition of the matrix of these tumour entities in order to further characterise the cellular phenotypes of these neoplasms using typical cell biological marker genes. METHODS: The matrix compositions of chondroblastomas and chondromyxoidfibromas were analyzed by HE-histology, histochemistry, and immunolocalization techniques. Cellular gene expression patterns were detected by mRNA in situ hybridization. RESULTS: Chondroblastomas are rich in collagen type I and show foci of an osteoid-like matrix, whereas collagen type II as a typical marker of chondrocytic differentiation was not detected in any of the specimens. Chondromyxoidfiibromas had foci of chondroid appearance with chondroblastic cellular differentiation characterised by collagen type II expression. CONCLUSION: These results characterise chondroblastomas and chondromyxoidfiibromas as skeletal neoplasms that have a different biology and which can be distinguished by matrix protein expression products: collagen type II, the typical marker of chondroblast differentiation, could only be detected in chondromyxoidfibromas, but not in chondroblastomas. Thus, both neoplasms are clearly different on the cell biological level.

Biomarkers, Tumor↗

PubMedDate not supplied

[cDNA-microarrays in cartilage research - functional genomics of osteoarthritis].

Functional genomics represents a new challenging approach in order to analyze complex diseases such as osteoarthritis on a molecular level. The characterization of the molecular changes of the cartilage cells, the chondrocytes, enables a better understanding of the pathomechanisms of the disease. In particular, the identification and characterization of new target molecules for therapeutic intervention is of interest. Also, potential molecular markers for diagnosis and monitoring of osteoarthritis contribute to a more appropriate patient management. The DNA-microarray technology complements (but does not replace) biochemical and biological research in new disease-relevant genes. Large-scale functional genomics will identify molecular networks such as yet identified players in the anabolic-catabolic balance of articular cartilage as well as disease-relevant intracellular signaling cascades so far rather unknown in articular chondrocytes. However, at the moment it is also important to recognize the limitations of the microarray technology in order to avoid over-interpretation of the results. This might lead to misleading results and prevent to a significant extent a proper use of the potential of this technology in the field of osteoarthritis.

Cartilage↗

PubMedDate not supplied

Subtyping of osteoarthritic synoviopathy.

OBJECTIVE: Osteoarthritis research is traditionally concentrating on events within the degenerated articular cartilage. Changes in the synovial membrane are largely neglected. In fact, they are generally interpreted as secondary to the cartilage changes and not pathogenetically involved in the disease process. In this study, we present a systematic analysis of the synovial reaction pattern in early and late stages of the osteoarthritic disease process. METHODS: A large series of synovial specimens derived from early and late stage osteoarthritic cartilage disease were investigated by histological and immunohistochemical means for tissue architecture and inflammatory cell infiltrates. For comparison, also samples with rheumatoid arthritis, seronegative arthritis, and septic arthritis were included as well as normal synovial membrane specimens. RESULTS: In all specimens derived from patients with diagnosed osteoarthritis alterations of the synovial tissue were observed. A large spectrum of alterations was found in different stages of osteoarthritic joint disease and four different basic pattern of synovial reactions could be identified: (i) hyperplastic, (ii) inflammatory, (iii) fibrotic, and (iv) detritus-rich synoviopathy. CONCLUSION: We show that in all cases of clinically overt osteoarthritic joint disease significant synovial pathology is associated. Furthermore, our study clearly documents that in osteoarthritic synovium significant inflammation can occur. This is suggestive of a distinct pathogenetic role of the synovium also in osteoarthritic cartilage degeneration at least in a subset of cases.

Adult↗

PubMedDate not supplied

MMP-8 is only a minor gene product of human adult articular chondrocytes of the knee.

OBJECTIVE: The initial degradation of collagen fibrils during osteoarthritic cartilage destruction depends on the cleavage at the collagenase site, for which there exist three major candidate enzymes: collagenase 1 (MMP-1), collagenase 2 (MMP-8), and collagense 3 (MMP-13). The objective of this study was to determine the quantitative expression as well as distribution levels in normal and osteoarthritic cartilage and synovium and in cultured articular chondrocytes with and without stimulation by Il-1 beta. METHODS: Conventional and online PCR technology and immunohistochemistry were used to determine MMP-8 expression levels on the mRNA and protein level. RESULTS: Whereas conventional PCR analysis could demonstrate the presence of MMP-8 mRNA in normal and osteoarthritic chondrocytes, online quantitative PCR showed that only very minor amounts of MMP-8 mRNA expression is found in articular chondrocytes in vivo (and in vitro) and that there is no significant upregulation in osteoarthritic cartilage in vivo nor by Il-1 beta in vitro. The in vivo results were confirmed by the absence of significant protein staining with monoclonal antibodies for MMP-8 in normal and osteoarthritic chondrocytes. CONCLUSIONS: The presented results confirm the presence of a very minor MMP-8 expression by articular chondrocytes, but clearly question the hypothesis that MMP-8 is a major cartilage matrix degrading protease and is involved in enhanced cartilage matrix breakdown in osteoarthritic cartilage degeneration or by Il-1 beta stimulation in vitro.

Adult↗

PubMedDate not supplied

Regulation of anabolic and catabolic gene expression in normal and osteoarthritic adult human articular chondrocytes by osteogenic protein-1.

OBJECTIVE: Osteoarthritis is characterized by dramatic changes in chondrocyte metabolism including the overexpression of catabolic enzymes, but also a lack of anabolic activity. In this respect, osteogenic protein 1 (OP-1) appears to be one of the most potent anabolic factors of chondrocytes. In this study, we were interested in: (1) whether recombinant human OP-1 exerts its anabolic effects also on osteoarthritic chondrocytes, (2) whether OP-1 modulates the expression of catabolic genes, and (3) whether the BMP effects are related to the expression levels of its intracellular mediators (R- and I-Smads). METHODS: Chondrocytes were isolated from cartilage of either normal (n = 5) or osteoarthritic (n = 8) human knee joints and cultured in short-term high-density monolayer cultures with and without recombinant OP-1. RNA was isolated and analyzed for mRNA expression levels of anabolic (aggrecan, collagen type II), catabolic (MMP-1, -3, -13, ADAMTS-4), and intracellular signaling mediators (Smad 1, 4, 5, 6, 7, and 8) by quantitative online PCR. RESULTS: After OP-1 stimulation, the anabolic genes were significantly up-regulated in osteoarthritic chondrocytes in comparison to normal chondrocytes. Neither in normal nor osteoarthritic chondrocytes were significant changes observed for the matrix degrading enzymes. Smads were also expressed in both normal and osteoarthritic cells at roughly the same level with and without stimulation with OP-1. CONCLUSION: Osteoarthritic chondrocytes are not hypo-responsive to anabolic stimulation by OP-1. Thus, human recombinant OP-1 could be a suitable anabolic activator of osteoarthritic chondrocytes. This might be of particular interest as chondrocytes themselves showed very low levels of OP-1 expression.

ADAM Proteins↗

PubMedDate not supplied

MMP-2/gelatinase A is a gene product of human adult articular chondrocytes and is increased in osteoarthritic cartilage.

OBJECTIVE: Collagen fibril degeneration involves initially the cleavage within the triple helix by the collagenases (1 and 3), but then mainly involves also the gelatinases, of which gelatinase A (MMP-2) appears to play a central role in many tissues. The objective of this study was to determine the quantitative expression levels as well as the distribution in normal and osteoarthritic cartilage of gelatinase A and in cultured articular chondrocytes with and without stimulation by Il-1beta. METHODS: Conventional and online PCR technology and immunohistochemistry were used to determine MMP-2 expression levels on the mRNA and protein level. RESULTS: Conventional PCR analysis could demonstrate the presence of MMP-2 mRNA in normal and osteoarthritic chondrocytes. Online quantitative PCR confirmed the presence of MMP-2 mRNA expression in normal articular chondrocytes in vivo (and in vitro). An increase of 5x (p < 0.001) was observed in osteoarthritic cartilage in vivo. Of note, no significant up-regulation of gelatinase A was observed by Il-1beta in vitro. Immunostaining for gelatinase A confirmed the presence of MMP-2 with mono- and polyclonal antibodies in normal and osteoarthritic chondrocytes with somewhat higher levels observed in the latter. CONCLUSIONS: The presented results confirm the increased expression of gelatinase A by osteoarthritic articular chondrocytes as previously described. Of note, also normal adult articular chondrocytes expressed significant amounts of gelatinase A in vivo and in vitro suggesting gelatinase A as being also involved in physiological collagen turnover in human adult articular cartilage.

Aged↗

PubMedDate not supplied

MMP-9/gelatinase B is a gene product of human adult articular chondrocytes and increased in osteoarthritic cartilage.

OBJECTIVE: Collagen fibril degeneration involves initially the cleavage within the triple helix by the collagenases 1 (MMP-1) and 3 (MMP-13), but then mainly involves also the gelatinases A (MMP-2) and B (MMP-9). The objective of this study was to determine the quantitative expression levels as well as the distribution in normal and osteoarthritic cartilage of gelatinase B and in cultured articular chondrocytes with and without stimulation by Il-1Beta. METHODS: Conventional and real-time quantitative PCR technology and immunohistochemistry were used to determine gelatinase B expression on the mRNA and protein level. RESULTS: Conventional PCR analysis could demonstrate the presence of gelatinase B mRNA only in osteoarthritic chondrocytes. Real-time quantitative PCR confirmed the increased expression of gelatinase B mRNA expression in osteoarthritic chondrocytes. No significant up-regulation of gelatinase B was observed by Il-1Beta. Immunostaining for gelatinase B showed the presence of gelatinase B in a subset of normal and in a large portion of osteoarthritic chondrocytes with a more extended distribution in the latter. CONCLUSION: In osteoarthritic cartilage destruction, gelatinase B is involved in collagen destruction though still at a very much lower level than gelatinase A. Only a very small subset of normal adult articular chondrocytes express gelatinase B in vivo suggesting that gelatinase B unlike gelatinase A is hardly or only very focally involved in physiological collagen turnover.

Aged↗

PubMedDate not supplied

CDRAP is expressed in adult articular cartilage, but its expression is not significantly regulated in osteoarthritic chondrocytes.

OBJECTIVE: In this study we assessed the differential in vivo mRNA expression levels of CDRAP, a potential marker of cartilage degeneration. METHODS: Conventional and real time PCR in a large series of normal (n = 18) and late stage osteoarthritic (n = 24) cartilage specimens were performed. RESULTS: Conventional PCR analysis could demonstrate the presence of CDRAP mRNA in normal and osteoarthritic chondrocytes. Real time quantitative PCR confirmed the presence of CDRAP mRNA expression in normal articular chondrocytes in vivo (and in vitro). No significant up-regulation of CDRAP was observed in osteoarthritic chondrocytes in vivo. CONCLUSION: The presented results confirm expression of CDRAP by normal and osteoarthritic articular chondrocytes, but indicate that increased expression levels by chondrocytes are not the cause of the increased levels of CDRAP in the synovial fluid of patients with osteoarthritis.

Adult↗