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PubMed1989

Type 3 procollagen peptide in bronchoalveolar lavage fluid. Poor indicator of course and prognosis in sarcoidosis.

To investigate the role of bronchoalveolar lavage type 3 procollagen peptide as a prognostic indicator in sarcoidosis, we measured type 3 procollagen N-terminal peptide levels in lavage fluids from 84 sarcoidosis patients and monitored disease progress in these patients for a period of 12 months. Lavage procollagen peptide levels were significantly elevated in sarcoidosis patients compared to control subjects (p less than 0.001). No association was observed between lavage type 3 procollagen peptide and disease severity, as assessed by lung function tests. Follow-up monitoring of patients failed to demonstrate any relationship between subsequent functional deterioration and initial lavage type 3 procollagen peptide. These results suggest that elevated lavage type 3 procollagen peptide concentrations in sarcoidosis may reflect increased type 3 collagen synthesis associated with the inflammatory process rather than signal an early event in the development of chronic disease.

Adult↗
PubMed1987

Estimation of the production rates of serum aminoterminal propeptide of type III procollagen and laminin in human fibrotic liver.

The concentrations of laminin, a high molecular weight non-collagenous glycoprotein of basement membranes, and of the N-terminal propeptide of type III procollagen were determined in the serum of the liver outflow vascular region (hepatic vein) and of a peripheral vein (cubital vein) in patients with chronic liver diseases (fibrosis, cirrhosis, unspecified histology; n = 173), in order to determine their secretion rates from the injured livers. The mean levels of laminin (1.84 kU/l) and of procollagen peptide (28.0 micrograms/l) in hepatic vein were significantly higher (about 9.5% at p less than 0.02, and 37% at p less than 0.001, respectively) than those in the periphery (1.68 kU/l and 20.4 micrograms/l, respectively). In chronic liver diseases, however, laminin and procollagen peptide concentrations in the hepatic vein were lower than or equal to those in the cubital vein in 18% and 27% of patients, respectively. The highest regional differences of the concentrations were noted in cirrhotic subjects. The serum levels of laminin (rs 0.93) and of procollagen peptide (rs 0.73) in hepatic and in cubital vein are highly positively correlated (p less than 0.001), but the levels of procollagen peptide in hepatic vein are only weakly but still significantly statistically related with those of laminin (rs 0.446, p less than 0.001). Similarly, the hepatic-cubital venous concentration differences of both proteins are weakly (rs 0.312) but significantly (p less than 0.001) correlated. On the basis of several assumptions we estimated secretion rates from the livers of 120 U.min-1 for laminin, and 5.7 micrograms.min-1 for procollagen peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic Disease↗
PubMedDate not supplied

Effects of platelet-derived growth factor isoforms on human lung fibroblast proliferation and procollagen gene expression.

Platelet-derived growth factor (PDGF), a potent mitogen for fibroblasts, is a potentially important cytokine in the pathogenesis of fibroproliferative disorders of lung. Different isoforms of PDGF include a heterodimer composed of A and B chains and homodimers composed of A or B chains. The biological significance of the different isoforms is unknown, but they have been shown to differ in their mitogenic potency in some systems. Their effects on other fibroblast functions have not been fully examined. We undertook this study to determine the effect of PDGF isoforms on human lung fibroblast proliferation and procollagen synthesis. Cultured lung fibroblasts (IMR-90, WI-38, GeNA) were incubated in the presence of varying concentrations of highly purified PDGF-AB obtained from platelets or recombinant PDGF-AA or -BB homodimers. Incorporation of [3H]thymidine was determined as a measure of mitogenic activity. Fetal lung fibroblasts (IMR-90, WI-38) and an adult fibroblast strain (GeNA) responded similarly to the different isoforms, with maximum mitogenic activity observed at 5-10 ng/mL. Cell cycle analysis using three additional normal adult lung fibroblast strains indicated that all PDGF isoforms stimulated similar proportions of cells to cycle over a 7-day period. Fibroblast procollagen synthesis, measured after pulse labeling with [3H]proline, was not increased even at concentrations of the PDGF isoforms that were maximally mitogenic. Moreover, steady-state levels of alpha 1(I) and alpha 1(III) procollagen mRNA levels, determined by northern analysis and dot blot hybridization, were not changed after exposure to any of the PDGF isoforms. While all PDGF isoforms are potent mitogens for fetal and adult lung fibroblasts, it was concluded that they do not directly stimulate procollagen gene expression or procollagen synthesis in vitro. The results suggest that PDGF isoforms are potentially important mitogens for lung fibroblasts, but other factors are likely to be involved in the stimulation of fibroblast procollagen synthesis that is observed in fibroproliferative disorders of lung.

Cell Cycle↗
PubMedDate not supplied

Molecular mechanisms of antifibrotic effect of interferon gamma in bleomycin-mouse model of lung fibrosis: downregulation of TGF-beta and procollagen I and III gene expression.

The present study was undertaken to elucidate the mechanism for the antifibrotic effect of interferon gamma (IFN-gamma) in the bleomycin (BL)-mouse model of lung fibrosis. The expression of transforming growth factor (TGF-beta) and procollagen I and III and their mRNAs was investigated in the BL-mouse model of lung fibrosis with and without IFN-gamma treatment by Northern and slot blot analyses. Temporal changes in the content of procollagen and TGF-beta mRNAs in the lungs of mice receiving saline or BL by intratracheal route, with and without IFN-gamma treatment by intramuscular route, were quantitated. The level of TGF-beta mRNA increased rapidly and peaked at day 5, whereas the levels of mRNAs for procollagens alpha 1(I) and alpha 1(III) peaked at 10 days after BL instillation. The peak levels of these mRNAs in BL-treated animals were five- to sevenfold higher than those of the control. The increase in TGF-beta mRNA in the lungs of BL-treated mice preceded the increase in the synthesis of type I and type III procollagen mRNAs. BL treatment also increased the hydroxyproline content significantly from 3 to 14 days as compared to the corresponding saline control groups. A maximal increase to 447 micrograms/lung from 223 micrograms/lung in saline control was obtained at 10 days after instillation. Daily treatment with IFN-gamma markedly reduced the BL-induced increases in the mRNA levels of TGF-beta, and procollagen alpha 1(I) and alpha 1(III) without any effect on the lung level of beta-actin mRNA. IFN-gamma treatment also caused significant reduction in the BL-induced increase in the lung hydroxyproline content from 417 to 283 micrograms/lung at 7 days and from 447 to 264 micrograms/lung at 10 days. It may be concluded from the findings of the present study that the cellular mechanisms for the antifibrotic effect of IFN-gamma in the BL-mouse model of lung fibrosis are to initially downregulate the BL-induced overexpression of TGF-beta mRNA, and subsequently procollagen mRNAs, leading to a decreased collagen content.

Animals↗
PubMed1982

Studies on the underhydroxylated basement membrane procollagen synthesized by rat parietal yolk sacs in the presence of alpha,alpha'-dipydridyl.

Rat embryo parietal yolk sacs synthesized and secreted underhydroxylated [14C]proline-labeled basement membrane procollagen when incubated in the presence of the iron chelator alpha,alpha'-dipyridyl and [14C]proline. Upon reduction and sodium dodecyl sulfate-agarose gel filtration, this procollagen eluted as a discrete peak of labeled material close to the position of the beta components of type I collagen. Secreted underhydroxylated procollagen contained interchain disulfide bonds and was completely degraded by a 6 hr treatment with alpha-chymotrypsin at 4 degrees C. Results from 4 hr incubations indicated that the distribution of 14C-procollagen between tissue and medium was unaffected by the presence of alpha,alpha'-dipyridyl, but analysis of results from pulse-label and chase experiments revealed that underhydroxylated procollagen was secreted at less than half the rate of control procollagen.

2,2'-Dipyridyl↗
PubMed1991

Acetaldehyde increases procollagen type I and fibronectin gene transcription in cultured rat fat-storing cells through a protein synthesis-dependent mechanism.

We previously reported that acetaldehyde increases the production of type I collagen in cultured rat fat-storing cells. We studied the regulation of this effect by determining the expression of procollagen type I, fibronectin and transforming growth factor-beta 1 messenger RNAs in passage 1 and 2 cultures of fat-storing cells exposed to acetaldehyde for up to 24 hr. By 6 hr, acetaldehyde increased the steady-state levels of alpha 1 procollagen type I messenger RNA 3.2-fold and of fibronectin messenger RNA 2.8-fold above control values. At 24 hr, messenger RNA levels remained elevated. In contrast, transforming growth factor-beta 1 messenger RNA steady-state levels remained unaltered by 6 hr, but increased 1.5-fold by 24 hr. Cycloheximide (0.3 mmol/L) completely inhibited the acetaldehyde effect when added at zero time but was less effective when added at 15 min. The effect of acetaldehyde was not modified when cells were cultured in the presence of the acetaldehyde dehydrogenase inhibitor cyanamide (100 mumol/L). Fat-storing cells were also cultured in the presence of lactate (5, 15 and 25 mmol/L) for 6 hr. At none of these concentrations was any effect seen on either alpha 1(I) procollagen or fibronectin messenger RNAs. In the presence of methylene blue, a scavenger of reducing equivalents, the effect of acetaldehyde on alpha 1(I) procollagen and fibronectin gene expression was totally inhibited. Transcription run-on assay showed that acetaldehyde increased both procollagen type I and fibronectin transcriptional activity threefold and 2.5-fold, respectively. We conclude that acetaldehyde increases alpha 1(I) procollagen and fibronectin gene expression through enhanced transcription by a mechanism dependent on newly synthesized proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗
PubMed1990

Cellular localization of type I III and IV procollagen gene transcripts in normal and fibrotic human liver.

The authors have determined the cell types producing alpha 1 (I), alpha 2 (I), alpha 1 (III), and alpha 1 (IV) procollagen gene transcripts in adult human liver by in situ hybridization with [35S]-labeled RNA probes. The liver specimens comprised a total of 20 biopsies with normal histology and biopsies with fibrosis or cirrhosis at different clinical stages and of heterogeneous origins. In normal liver, procollagen type I, III, and IV transcripts were detected in stromal and vascular mesenchymal cells of portal tracts and central veins, as well as in some perisinusoidal cells of the lobule. In fibrotic liver, increased levels of these procollagen mRNAs were observed in the same locations, and particularly enhanced in stromal cells of fibrotic septa and portal tracts, as well as in perisinusoidal cells. Expression of alpha 1 (IV) procollagen RNA was additionally found in some vascular endothelial and bile duct epithelial cells. Although previously suggested as the major source of liver collagens, hepatocytes showed no significant procollagen transcript levels in any of our samples. Thus, procollagen synthesis does not appear to be a function of hepatocytes, but rather of mesenchymal, endothelial, and bile duct epithelial cells in adult human liver. These findings may have implications for the development of specifically targeted antifibrotic therapies.

Adult↗
PubMed1988

Alterations in pulmonary mRNA encoding procollagens, fibronectin and transforming growth factor-beta precede bleomycin-induced pulmonary fibrosis in mice.

Female C57Bl/6 mice treated by constant s.c. infusion for 1 week with 100 mg of bleomycin per kg of body weight develop a more pronounced pulmonary fibrosis than BALB/c mice. Within 4 weeks after bleomycin treatment, the pulmonary content of mRNAs encoding fibronectin, alpha 2I procollagen and alpha 1III procollagen was increased. The increases were greater and occurred earlier in C57Bl/6 mice compared to BALB/c mice. Fibronectin mRNA increased 12-fold in C57Bl/6 mice and only 3-fold in BALB/c mice, whereas alpha 1III procollagen mRNA increased 4-fold in C57Bl/6 mice and 2-fold in BALB/c mice. alpha 2I procollagen mRNA was increased only in C57Bl/6 mice (2-fold). The increases were sequential in C57Bl/6 mice: fibronectin mRNA was elevated first, followed by alpha 2I procollagen, then alpha 1III procollagen mRNA. The temporal relationship between these mRNA elevations and extracellular matrix accumulation, and the exaggerated responses in C57Bl/6 mice, suggest that matrix accumulation is a function of the mRNA levels. Transforming growth factor-beta mRNA relative to total polyadenylated RNA was elevated 5-fold in C57Bl/6 mice and depressed 80% in BALB/c mice 1 week after treatment. Early alterations in transforming growth factor-beta mRNA may contribute to murine strain variation in bleomycin-induced pulmonary fibrosis and suggest the involvement of transforming growth factor-beta in this disease.

Animals↗
PubMed1985

Altered triple helical structure of type I procollagen in lethal perinatal osteogenesis imperfecta.

Cultured dermal fibroblasts from an infant with the lethal perinatal form of osteogenesis imperfecta (type II) synthesize normal and abnormal forms of type I procollagen. The abnormal type I procollagen molecules are excessively modified during their intracellular stay, have a lower than normal melting transition temperature, are secreted at a reduced rate, and form abnormally thin collagen fibrils in the extracellular matrix in vitro. Overmodification of the abnormal type I procollagen molecules was limited to the NH2-terminal three-fourths of the triple helical domain. Two-dimensional mapping of modified and unmodified alpha chains of type I collagen demonstrated neither charge alterations nor large insertions or deletions in the region of alpha 1(I) and alpha 2(I) in which overmodification begins. Both the structure and function of type I procollagen synthesized by cells from the parents of this infant were normal. The simplest interpretation of the results of this study is that the osteogenesis imperfecta phenotype arose from a new dominant mutation in one of the genes encoding the chains of type I procollagen. Given the requirement for glycine in every third position of the triple helical domain, the mutation may represent a single amino acid substitution for a glycine residue. These findings demonstrate further heterogeneity in the biochemical basis of osteogenesis imperfecta type II and suggest that the nature and location of mutations in type I procollagen may determine phenotypic variation.

Cyanogen Bromide↗
PubMed1987

Basement membrane procollagen IV and its specialized carboxyl domain are conserved in Drosophila, mouse, and human.

Interaction with the extracellular matrix is important for the proliferation and differentiation of cells during development. A specialized extracellular matrix, basement membrane, is built around a scaffold of procollagen IV molecules. We report the sequence of a 2.5-kilobase cDNA which contains the carboxyl end of a Drosophila melanogaster procollagen IV. The amino acid sequence of the carboxyl-terminal domain, which forms an essential intermolecular linkage between procollagen IV molecules, is 59% identical in Drosophila and vertebrate procollagens IV, and an additional 17% of residues are conservatively substituted. This implies that the nature of the linkage is also conserved. We suggest that intermolecular junctions through procollagen IV carboxyl domains are fundamental elements of the molecular architecture of Metazoan basement membranes and have been conserved during evolution. The isolation and identification of this basement membrane collagen gene of Drosophila will help in deducing the function of procollagen IV in basement membranes.

Amino Acid Sequence↗
PubMed1987

Interchain disulfide bond formation in types I and II procollagen. Evidence for a protein disulfide isomerase catalyzing bond formation.

The assembly of reduced pro-alpha chains of type I and type II procollagen into the native triple-helical molecule was examined in vitro in the presence and absence of pure protein disulfide isomerase. The data clearly indicates that protein disulfide isomerase is able to accelerate the formation of native interchain disulfide bonds in these procollagens. It takes about 6 min after disulfide bonding before triple-helical molecules exist, while the time required to produce triple-helical type I procollagen in the presence of protein disulfide isomerase is 9.4 min and that for type II procollagen 17.2 min. These values agree with those obtained for type I and II procollagen in vivo suggesting that protein disulfide isomerase is also an enzyme catalyzing interchain disulfide bond formation in procollagen in vivo. The formation of native disulfide bonds can proceed without any enzyme catalysis but then requires the presence of reduced and oxidized glutathione. Bonding is rather slow in such a case, however, resulting in a delay in the formation of the triple helix.

Animals↗
PubMed1987

Increased procollagen mRNA levels in carbon tetrachloride-induced liver fibrosis in rats.

Carbon tetrachloride-induced liver damage is a well-characterized experimental model for studying liver fibrosis. We used this model to examine alpha 1(I), alpha 1(III), and alpha 1(IV) procollagen mRNA levels during the development of liver fibrosis. Rats were given 0.5 ml of carbon tetrachloride/kg of body weight for 1-6 weeks. The liver tissue was assayed for collagen content by measuring total hydroxyproline content. Specific increases in procollagen mRNAs were assayed by slot blot hybridization. There was a significant increase in hydroxyproline content of liver tissue following 3 weeks of carbon tetrachloride treatment. The increase in tissue collagen content correlated with an increase in alpha 1(I) procollagen mRNA levels. At 5 and 6 weeks of treatment, there was an increase in alpha 1(III) procollagen mRNA levels. alpha 1(IV) procollagen levels increased slightly with five injections of carbon tetrachloride treatment. These results suggest that specific increases in procollagen mRNAs in liver fibrosis parallel, but do not precede, increases in tissue collagen content.

Animals↗
PubMed1979

Procollagen synthesized by newborn rat skin in culture.

Newborn rat skin explants in culture have been found to synthesize and secrete into the medium a considerable amount of collagen precursors (procollagens). Gel-electrophoresis analysis of the material extracted from the medium indicates that it is constituted mainly by procollagen Type I with a small percentage of procollagen Type III. Antibodies have been raised to the extracted procollagen and, although no attempt has been made to render these antibodies specific to one procollagen type by appropriate immunoadsorption, the immunofluorescence patterns that have been obtained are in good agreement with those reported on procollagen Type I by other groups. When unfixed cultured fibroblasts are examined by indirect immunofluorescence in the presence of the antiprocollagen antibody, a fluorescent network of interwoven fibres on the cell surface is observed which is similar to the network formed by fibronectin (LETS) on the fibroblasts' cell membranes.

Animals↗
PubMed1982

Procollagen-type III-peptide serum concentrations in chronic persistent and chronic active hepatitis and in cirrhosis of the liver and their diagnostic value.

Until now the determination of fibrotic processes in liver disease was restricted to histological examination of liver tissue. Recently a RIA was developed to determine the procollagen-type III-peptide concentrations in biological fluids. We used this RIA to measure the serum procollagen-type III-peptide concentrations in patients with chronic liver disease. Additionally in 24 patients with chronic persistent and chronic active hepatitis the collagen content in liver biopsies was determined histomorphometrically. The serum procollagen-type III-peptide concentrations in healthy controls (n = 40) were 6.4 +/- 0.6 ng/ml, in chronic persistent hepatitis (n = 47) 8.7 +/- 0.5 ng/ml, in chronic active hepatitis (n = 53) 20.8 +/- 2.9 ng/ml, and in alcoholic cirrhosis of the liver (n = 22) 47.7 +/- 6.1 ng/ml. Thus the patients with chronic active hepatitis and cirrhosis of the liver showed significantly elevated serum procollagen-type III-peptide levels. In chronic hepatitis a highly significant correlation (p less than 0.001) could be demonstrated between collagen content in liver tissue and serum procollagen-type III-peptide concentrations. The determination of serum procollagen-type III-peptide concentrations may prove a new useful parameter in biochemical evaluation of liver disease.

Biopsy↗
PubMed1993

Regulation of human lung fibroblast alpha 1(I) procollagen gene expression by tumor necrosis factor alpha, interleukin-1 beta, and prostaglandin E2.

We investigated the participation of prostaglandin (PG) E2 in the regulation of the alpha 1(I) procollagen gene expression by tumor necrosis factor alpha (TNF alpha), and interleukin-1 beta (IL-1 beta) in normal adult human lung fibroblasts. TNF alpha (100 units/ml) and IL-1 beta (100 units/ml) stimulated the production of PGE2 and caused a dose-dependent inhibition of up to 54 and 66%, respectively, of the production of type I procollagen. Preincubation of cultures with indomethacin partially reversed the inhibition of procollagen production induced by the cytokines. Cytokine-stimulated endogenous fibroblast PG accounted for 35 and 68% of the inhibition induced by TNF alpha and IL-1 beta, respectively. Steady-state mRNA levels for alpha 1(I) procollagen paralleled the changes in collagen production. The transcription rate of the alpha 1(I) procollagen gene was reduced by 58% by TNF alpha and by 43% by IL-1 beta. Cytokine-stimulated endogenous PG production accounted for half of these effects. These results indicate that TNF alpha and IL-1 beta inhibit the expression of the alpha 1(I) procollagen gene in human lung fibroblasts at the transcriptional level by a PGE2-independent effect as well as through the effect of endogenous fibroblast PGE2 released under the stimulus of the cytokines.

Adult↗
PubMed1995

Induction of an acute phase response in rats stimulates the expression of alpha 1(I) procollagen messenger ribonucleic acid in their livers. Possible role of interleukin-6.

BACKGROUND: In response to nonspecific inflammatory stimuli, circulating monocytes produce several cytokines that regulate the expression of liver acute phase protein genes. Patients with alcoholic liver disease have several manifestations of the acute phase response, including elevated serum levels of interleukin (IL)-1 (IL-1), IL-6 and tumor necrosis factor-alpha (TNF-alpha). However, the role of the acute phase response on liver fibrogenesis has not been explored. EXPERIMENTAL DESIGN: In this communication we report experiments performed to investigate whether turpentine, an acute phase response inducer in rats has any effect on alpha 1 (I) procollagen gene expression in the liver. We also investigated which of the cytokines is responsible for the turpentine effect and whether IL-6 and TNF-alpha had an effect on alpha 1 (I) procollagen mRNA expression by liver fat-storing cells (FSC). RESULTS: We show that alpha 1 (I) procollagen mRNA is increased in livers of turpentine-treated rats, and that an antibody to IL-6 as well as colchicine inhibit this effect. We also show that rIL-6 induces the expression of alpha 1 (I) procollagen mRNA in cultured FSC but not in hepatocytes. We demonstrated that the IL-6 effect is a transcriptional event that requires "de novo" protein synthesis. In addition to its effect on collagen gene expression, rIL-6 also stimulates expression of transforming growth factor-beta and fibronectin mRNAs. TNF-alpha inhibits alpha 1 (I) procollagen expression in FSC by 24 to 48 hours. However, TNF-alpha induces a transient expression of alpha 1 (I) procollagen mRNA by 2 to 3 hours. This increase is preceded by the induction of IL-6 mRNA. CONCLUSIONS: We conclude that IL-6 produced during the acute phase response, alone or in conjunction with other cytokines, could play an important role in liver fibrogenesis by inducing the expression of collagen, fibronectin, and transforming growth factor-beta mRNAs in FSC.

Acute-Phase Reaction↗
PubMed1993

BiP binds type I procollagen pro alpha chains with mutations in the carboxyl-terminal propeptide synthesized by cells from patients with osteogenesis imperfecta.

Of 20 fibroblast cell strains from patients with osteogenesis imperfecta (OI), a disease caused by mutations in the genes encoding type I procollagen, three had increased synthesis of BiP (GRP78), an hsp70-related, endoplasmic reticulum-resident protein. All three strains carry unique mutations in pro alpha 1(I) chains which impair type I procollagen chain association. Immunoprecipitation and pulse-chase experiments show that BiP (immunoglobulin heavy chain-binding protein) stably binds pro alpha 1(I) chains in these three cell strains after a brief lag. Ascorbate, which increases procollagen synthesis, increases BiP synthesis and content in these three strains and not in the others. In one of these three strains, BiP content is constitutively elevated prior to ascorbate treatment, and BiP is less inducible. This strain also has relatively high levels of synthesis and content of GRP94, another endoplasmic reticulum-resident stress protein. Pretreating each of the three cell strains to increase their BiP content reduces subsequent ascorbate-mediated BiP induction. BiP synthesis in the 17 other OI strains examined, which had a variety of type I procollagen mutations, was normal. These results suggest that BiP is induced by and binds procollagen with specific types of mutations: ones in the carboxyl-terminal propeptide that interfere with chain association. The recognition by BiP of such procollagen in OI cell strains shows that BiP plays a role in the physiological response to the production of some disease-producing abnormal proteins.

2,2'-Dipyridyl↗
PubMed1996

Maturation of collagen fibrils in the corneal stroma results in masking of tyrosine-rich region of type V procollagen.

PURPOSE: To determine the molecular form of type V procollagen in collagen fibrils in mammalian corneal stromas. METHODS: The presence of the tyrosine-rich region in the NH2-propeptide of type V procollagen in collagen fibrils was examined in human, bovine, and mouse corneas and human corneal fibroblast cultures by immunofluorescence microscopy and immunoblot analysis using a polyclonal antibody specific for this region. The antibody was generated using a glutathione S-transferase-fusion peptide. RESULTS: The tyrosine-rich region was detected readily in frozen sections of 5- to 6-month-old mouse corneal stromas without the need for any unmasking techniques, indicating that this domain is exposed on the surface of striated collagen fibrils. In contrast, frozen sections of adult human and bovine corneas did not label with the polyclonal sera to the tyrosine-rich region. Immunoblot analysis of bacterial collagenase digests of human and bovine corneas, however, indicated that peptide fragments containing the tyrosine-rich region of type V procollagen and of the expected molecular weight of 70 to 85 kDa were present. Further immunofluorescence microscopic studies and immunoblot analysis of mouse corneas at different ages and of collagen fibrils formed in human corneal fibroblast cultures over time indicated that, initially, the tyrosine-rich region of type V procollagen could be detected in all these collagen fibrils; however, as the age of the mouse and the culture increased, the ability to detect this region decreased. CONCLUSIONS: These results suggest that, in vivo, the tyrosine-rich region of type V procollagen is retained on type V procollagen molecules within mammalian collagen fibrils from corneal stromas and that this region becomes masked as collagen fibrils mature or the species ages.

Adult↗