Synthesis Of Interstitial Collagens Research Articles

Atherosclerotic Plaque Stability—What Determines the Fate of a Plaque?

Although the understanding of the underlying pathology of atherosclerosis has improved in recent years, the disease is still the main cause of death globally. Current evidence has implicated the role of inflammation in atherogenesis and plaque destabilization. Thus, inflammatory cytokines may attenuate interstitial collagen synthesis, increase matrix degradation, and promote apoptosis in several atheroma-associated cell types, and all these cellular events may enhance plaque vulnerability. Several cell types found within the lesion (ie, monocyte/macrophages, T cells, mast cells, platelets) contribute to this immune-mediated plaque destabilization, and a better understanding of these processes is a prerequisite for the development of new treatment strategies in these individuals. Such knowledge could also facilitate a better identification of high-risk individuals. In the present study, these issues will be discussed in more detail, particularly focusing on the interactions between matrix degradation, apoptotic, and inflammatory processes in plaque destabilization.

Collecting duct epithelium and injury: Not all cells are created equal

Studies by Butt et al. in the developing fetus provide new and timely insights into the regulation of repair and fibrosis in the injured kidney. Using a clinically relevant model, they have examined the response of the medullary collecting duct to ureteral obstruction, with some unexpected findings.

Comparative analysis of gene expression profiles in intact and damaged regions of human osteoarthritic cartilage

To analyze the differences in gene expression profiles of chondrocytes in intact and damaged regions of cartilage from the same knee joint of patients with osteoarthritis (OA) of the knee. We compared messenger RNA expression profiles in regions of intact and damaged cartilage (classified according to the Mankin scale) obtained from patients with knee OA. Five pairs of intact and damaged regions of OA cartilage were evaluated by oligonucleotide array analysis using a double in vitro transcription amplification technique. The microarray data were confirmed by real-time quantitative polymerase chain reaction (PCR) amplification and were compared with previously published data. About 1,500 transcripts, which corresponded to 8% of the expressed transcripts, showed > or = 2-fold differences in expression between the cartilage tissue pairs. Approximately 10% of these transcripts (n = 151) were commonly expressed in the 5 patient samples. Accordingly, 114 genes (35 genes expressed in intact > damaged; 79 genes expressed in intact < damaged) were selected. The expression of some genes related to the wound-healing process, including cell proliferation and interstitial collagen synthesis, was higher in damaged regions than in intact regions, similar to the findings for genes that inhibit matrix degradation. Comparisons of the real-time quantitative PCR data with the previously reported data support the validity of our microarray data. Differences between intact and damaged regions of OA cartilage exhibited a similar pattern among the 5 patients examined, indicating the presence of common mechanisms that contribute to cartilage destruction. Elucidation of this mechanism is important for the development of effective treatments for OA.

Potential role for immunomodulatory therapy in atherosclerotic plaque stabilisation

Our understanding of the mechanisms underlying acute coronary syndromes has evolved beyond the view that this syndrome reflects a progressive collection of lipids and cellular debris in the vascular wall. Current evidence has implicated a role for inflammation in the pathogenesis of this process. Thus, inflammatory cytokines may attenuate interstitial collagen synthesis, increase matrix degradation and promote apoptosis in several atheroma-associated cell types, and all these cellular events may enhance plaque vulnerability. Recently, a series of experimental studies have reported the plaque-stabilising effects of immunomodulatory therapy such as chemokine blockade, anti-CD40 ligand and IL-10. It is conceivable that some of these approaches will be tested clinically and, if successful, they could provide novel treatment strategies for atherosclerotic plaque stabilisation.

Interstitial collagen synthesis and processing in human amnion: a property of the mesenchymal cells.

This study was conducted to evaluate the ontogeny and cellular site of interstitial collagen formation in amnion, the tissue that provides the tensile strength of the human fetal membranes. The levels of procollagen alpha 1(I), alpha 2(I), and alpha 1(III) subunit mRNAs and the specific activities of the enzymes prolyl 4-hydroxylase and lysyl hydroxylase were greatest in human amnion tissue early in gestation, decreasing rather abruptly after 12-14 wk gestation to a nadir that persisted to term. To evaluate these findings further, amnion epithelial and mesenchymal cells were separated by differential proteinase treatment. The freshly separated cells as well as epithelial and mesenchymal cells maintained in culture were evaluated to assess the cellular site of interstitial collagen synthesis. By Northern analysis of total RNA, large amounts of procollagens alpha 1(I), alpha 2(I), and alpha 1(III) mRNAs were found in mesenchymal cells (freshly separated and in culture), but only negligible amounts of these transcripts were detected in RNA of freshly separated or cultured epithelial cells. The level of prolyl 4-hydroxylase alpha-subunit mRNA in mesenchymal cells was somewhat greater than that in epithelial cells. Radiolabeled collagen I synthesis from [3H]proline and [3H]glycine was not detected in amnion epithelial cells, whereas [3H]collagen alpha 1(I) and alpha 2(I) subunits were synthesized in large amounts by mesenchymal cells. A very small amount of [3H]collagen alpha 1(III) was synthesized in epithelial cells, but large amounts were formed in mesenchymal cells. These findings indicate that the mesenchymal cells are the site of interstitial collagen synthesis and processing in amnion. The density of mesenchymal cells in human amnion declines after the first trimester of pregnancy, and a significant decline in DNA content per unit of amnion tissue dry weight as pregnancy progressed was demonstrated in this study. Since the epithelial cells form an uninterrupted epithelium throughout gestation, the decline in DNA content probably corresponds to the decrease in the density of mesenchymal cells that commences after the first trimester pregnancy. Thus, the increase in the ratio of epithelial to mesenchymal cells as a function of gestational age may explain, at least in part, the decline in the levels of collagen mRNAs and the specific activities of lysyl and prolyl 4-hydroxylase in amnion tissue during human pregnancy.

Interstitial collagen synthesis by somatic testicular cells in culture

The synthesis, distribution and types of collagen produced by somatic testicular cells in culture was studied. To investigate whether changes in collagen synthesis correlate with the age of the animal, cultures derived from immature and pubertal rats were established. Immature rats synthesize 40 per cent more collagen than pubertal rats. Both groups of animals synthesize procollagen types I and III. Pro-collagen type I is present in the culture medium as well as in the cell fraction, while type III is only detected in the culture medium. In the transition from immature to pubertal rat, the ratio of procollagen type III to procollagen type I diminishes from 5.7 to 1.7. These results indicate that the synthesis, distribution and molecular characteristics of interstitial collagens changes with the age of the animal. Since, the content of other extracellular matrix components such as proteoglycans and collagen type IV also varies with age, we postulate that the composition of the extracellular matrix in the testes is not constant but changes with sexual development.

Establishment and characterization of five cell lines derived from human malignant gliomas.

We established and characterized five cell lines derived from human malignant gliomas (four glioblastomas multiforme and one highly anaplastic astrocytoma). All cell lines exhibited tumor cell morphology and growth kinetics, and anchorage-independent growth in soft agar. Cytogenetic analysis revealed significant aneuploidy in all five cases as well as clonal chromosomal alterations unique to each cell line. No cell line was tumorigenic in athymic mice. Two of the cell lines were sensitive to carmustine (BCNU) in monolayer and soft-agar cultures. Electron microscopy showed marked variability between cell lines in the number and structure of intracytoplasmic organelles; SF-126 formed collagen fibers in vitro. Immunohistochemical analysis of the surgical specimens showed variable expression of glial fibrillary acidic protein (GFAP) in malignant astrocytes; positive immunostaining for glycoproteins of the extracellular matrix was found predominantly in perivascular regions. In early-passage cultures, only cell line SF-295 expressed GFAP; at establishment, none of the cell lines expressed GFAF or glutamine synthetase. Fibronectin and laminin were expressed by all cell lines in early-passage culture, but expression of these glycoproteins at establishment was variable. Only SF-126 was positively identified by immunostains for procollagen III; this was also the only cell line in which DEAE-cellulose chromatography and SDS-PAGE demonstrated interstitial collagen synthesis. These well-characterized glioma-derived cell lines may now serve as useful tools with which to study the cell biology of gliomas. The synthesis of interstitial collagen by a glioma-derived cell line may suggest a derivation from vascular mesenchymal elements, either reactive or transformed, in the original heterogeneous malignant glioma, rather than from a glial precursor cell.

Collagen production by human mesothelial cells in vitro.

Serous effusions from a variety of malignant and non-malignant conditions were found to contain cells which had the morphological, histochemical and ultrastructural characteristics of mesothelial cells. In culture they were the predominant cell type and synthesised large quantities of the interstitial collagens type I and III, with the proportion of type III frequently approaching or exceeding 50 per cent. There was no evidence that they synthesised basement membrane collagen chains of type IV or type V. Since mesothelial cells are assumed to secrete the mesothelial basement membrane, the synthesis of interstitial collagens by desquamated mesothelial cells appears to reflect a change in the phenotype of collagen synthesis. We suggest that this change may be an important factor in the fibrosis of the serosal wall which frequently accompanies diseases with chronic serious effusion.

Synthesis of collagen type I, type I trimer and type III by embryonic mouse dental epithelial and mesenchymal cells in vitro

Epithelial and mesenchymal dental cells were grown in primary monolayer culture and the ability of both cell types to synthesize interstitial collagens was investigated. Pepsin-solubilized collagens were analyzed by CM-cellulose chromatography and both cell types were found to synthesize collagen type I, type III and type I trimer. The collagen phenotype of mesenchymal cells (type I: 82.4%, type III: 8.5%, type I trimer: 9.1%) was different from that of epithelial cells (type I: 71.8%, type III: 9.5%, type I trimer: 18.7%). The radioactivity incorporated into collagen molecules by mesenchymal cells was 34-times greater than the radioactivity incorporated by epithelial cells. This result agreed with previous observations obtained from tissue culture experiments (Lesot, H. and Ruch, J.V. (1979) Biol. Cell. 34, 23–37) which indicated a low synthesis of interstitial collagens by isolated dental epithelia when compared to isolated dental mesenchymes.

Synthesis of interstitial collagens by pig aortic endothelial cells in culture

Examination of the collagens synthesized by pig aortic endothelial cells in culture and precipitated from either the cell layer or medium, following pepsin digestion, demonstrated that the major species was Type I together with some Type III collagen and α1 (I) trimer. Additional chains in the cell layer chromatographing with Type I α1-chains on CM cellulose may be partly derived from basement-membrane-associated collagen but in the medium would appear to be entirely derived from α1 (I) trimer. These results imply that the endothelial cell may secrete the Type III collagen located in the immediate subendothelial space and, in part at least, the Types I and III occurring in diffusely thickened intima and the atherosclerotic plaque.

Complement component C1q is sensitive to acute vitamin C defficiency in guinea pigs

In acutely scorbutic guinea pigs, where interstitial collagen synthesis is markedly impaired, there was no significant reduction in total complement component C1 activity measured by a functional assay, and no significant reduction in the ratio of protein-bound hydroxyproline to protein-bound proline or to total serum protein, in comparison with pair-fed controls. There was a moderate increase in non-protein-bound hydroxyproline in the serum of the deficient animals. These result suggest that component C1q is largely resistant to the effects of severe acute scurvy, adn that some hydroxyproline-containing proteins may respond differently others, during vitamin C deficiency.