Development of molecular hybridization technology to evaluate albumin and procollagen mRNA content in baboons and man

Evidence of de novo collagen synthesis in healing human gastric ulcers

BACKGROUND

The fibrillar collagens, types I and III, have been demonstrated in healthy human gastric mucosa as well as in the submucosa of gastric ulcer edges, where they are remarkably increased.

METHODS

To verify the occurrence and activity of de novo collagen synthesis, we examined gastric biopsy specimens from six patients with antral ulcers and six normal controls. By means of in situ hybridization, using a 35S-labeled RNA probe, we could localize the specific procollagen mRNA for type-I collagen.

RESULTS

In normal gastric mucosa this mRNA was expressed by only a very limited number of cells, whereas at the ulcer edges the specific signal could be demonstrated in a large number of submucosal cells.

CONCLUSION

These results suggest a substantial role of fibroneogenesis in the process of gastric ulcer healing.

Detection of alpha-fetoprotein mRNA, an indicator of hematogenous spreading hepatocellular carcinoma, in the circulation: a possible predictor of metastatic hepatocellular carcinoma

We attempted to detect circulating hepatocellular carcinoma by demonstrating hepatocyte-associated mRNA in the nuclear cell component of peripheral blood using nested reverse transcription-polymerase chain reaction because of the extremely small number of tumor cells in the circulation. Albumin mRNA was demonstrated not only in the liver tissue (hepatocytes) and HepG2 cells but also in nuclear cells of the blood from normal healthy volunteers (neutrophils and lymphocytes) by reverse transcription-polymerase chain reaction. In contrast, alpha-fetoprotein mRNA was demonstrated in the liver tissue, as well as in HepG2 cells, but not in peripheral blood of normal healthy volunteers, indicating the possibility of using alpha-fetoprotein mRNA for detection of benign and malignant hepatocytes among the population of neutrophils and lymphocytes. alpha-Fetoprotein mRNA in peripheral blood was detected in 17 of 33 cases of hepatocellular carcinoma (52%), 2 of 13 cases of cirrhosis (15%) and 2 of 17 cases of chronic hepatitis (12%). alpha-Fetoprotein mRNA was not demonstrated in 26 cases of normal healthy volunteers (0%). Among the patients with hepatocellular carcinoma, total volume of tumor tissue, maximum size of tumor and serum alpha-fetoprotein level were markedly increased in the patients with alpha-fetoprotein mRNA in blood. In addition, alpha-fetoprotein mRNA was detected in the blood of all 6 patients showing metastasis at extrahepatic organs (100%), in contrast to 11 of 27 cases without metastasis (41%). From these results, we conclude that the presence of alpha-fetoprotein mRNA in peripheral blood may be an indicator of circulating malignant or benign hepatocytes, which might predict hematogenous spreading metastasis of tumor cells in patients with hepatocellular carcinoma.

Ethanol inhibits asialoglycoprotein receptor synthesis but augments its mRNA expression in a human hepatoma cell line

The effect of ethanol on the expression of asialoglycoprotein receptor protein and its mRNA was studied in a human hepatoma cell line, HepG2. The number of asialoglycoprotein receptors on the cell surface was decreased to 60% of the control level, without a loss in affinity, by incubating the cells with 100 mM ethanol. The decrease in cell surface asialoglycoprotein receptors was paralleled by a decrease in total receptor numbers, including intracellular and surface receptors. The internalization of asialoglycoprotein was also diminished, to 44% of that in control cells. The decreases in cell surface receptors and total receptor numbers were partially restored by 2 mM 4-methylpyrazole, suggesting that ethanol metabolites participated in the diminution of asialoglycoprotein receptor expression. However, the steady-state expression of asialoglycoprotein receptor mRNA was increased in ethanol-treated cells and further augmented by a longer ethanol exposure. These paradoxical results, i.e., the decrease of asialoglycoprotein receptor protein and the increase of its mRNA expression, suggest that the reduction in the asialoglycoprotein receptor protein is a post-transcriptional event and that a possible feedback regulatory mechanism may control asialoglycoprotein receptor gene transcription and/or impair the degradation of its mRNA.

Myofibroblast-like cells produce mRNA for type I and III procollagens in chronic active hepatitis

In chronic active hepatitis the rate of collagen biosynthesis is largely determined by intracellular mRNA concentrations. To localize procollagen mRNA-producing cells, we investigated biopsy specimens from five patients with hepatitis B surface antigen-positive chronic active hepatitis and five patients without liver disease by in situ hybridization. We used type I and III procollagen cDNAs for transcription to (35S)-labeled probes. Parallel sections were stained with anti-actin monoclonal antibodies. Our results show that cells in which collagen synthesis is ostensibly enhanced can be localized by in situ hybridization of procollagen mRNAs. These cells were also anti-actin-positive in parallel sections and were localized in areas of inflammatory cell infiltration and necrosis. We conclude that myofibroblast-like cells may express procollagen mRNAs in chronic active hepatitis. Moreover, in situ hybridization may be a valuable diagnostic tool for providing additional morphologic information on the degree of fibrogenesis activity.

Simultaneous expression of type I procollagen mRNA and albumin in cirrhotic human liver

The gene expression of human type I procollagen was investigated in cirrhotic human liver by using in situ hybridization with nonradioactive DNA probes. Using in situ hybridization can provide direct evidence for the cell type capable for type I collagen synthesis in tissues. T-T dimerized DNA probes were used and DNAs hybridized in situ were detected immunohistochemically using specific antibodies against T-T dimer. The data demonstrated that type I collagen is synthesized in hepatocytes and stellate cells in pseudolobules and in fibroblasts in Glissons capsules in cirrhotic human livers. We indicated hepatocytes morphologically and functionally by using immunohistochemical localization of albumin, which was used as a marker of hepatocyte, since albumin is synthesized exclusively by hepatocytes.

The serum concentrations of the aminoterminal propeptide of procollagen type III and the hepatic content of mRNA for the alpha 1 chain of procollagen type III in carbon tetrachloride-induced rat liver fibrogenesis

Serum concentrations of the aminoterminal propeptide of procollagen type III (PIIIP) are elevated in fibrogenic diseases of the liver, but the mechanism of elevation is not fully understood. To investigate the mechanism, we compared serum concentrations of PIIIP with total liver content of mRNA for the pro alpha 1 (III) chain, in rats with carbon tetrachloride (CCl4)-induced liver fibrosis. Adult male rats received CCl4 in mineral oil twice weekly for 8 weeks and were compared with age-matched controls. Serum concentrations of PIIIP were measured by a specific radioimmunoassay; molecular sizes of PIIIP in serum were also determined. Pro alpha 1 (III) mRNA content in the liver was quantitated by RNA slot-blot hybridization and chemical measurement of total hepatic RNA content. Total collagen content of the liver was estimated by hydroxyproline measurement. All CCl4-treated animals had septal fibrosis after 4 weeks, and evidence of cirrhosis (regenerative nodules, ascites) was seen after 7 weeks of treatment. Serum concentrations of PIIIP and pro alpha 1 (III) mRNA content in the liver were correlated well until cirrhosis has established. They increased simultaneously after 3 weeks of treatment, 1 week before any elevation of hepatic hydroxyproline could be detected. After cirrhosis has established, pro alpha 1 (III) mRNA content in the liver decreased markedly, but serum PIIIP levels continued to be elevated. Hepatic hydroxyproline plateaued after 5 weeks. The molecular sizes of serum PIIIP indicate the release of intact native procollagen peptide during the development of cirrhosis. In conclusion, at least in CCl4-induced liver fibrosis in the rats, serum PIIIP levels can be used as a fibrogenic marker for the period progressing to cirrhosis. But the use of the serum PIIIP levels in cirrhosis seems to be limited by factors other than liver fibrogenesis.

Albumin mRNA expression in human liver diseases and its correlation to serum albumin concentration

The expression of albumin mRNA in human liver samples was investigated in order to understand the molecular mechanism of albumin gene expression in various liver diseases. Albumin mRNA in acute hepatic failure and decompensated liver cirrhosis was reduced significantly compared to normal control liver (P less than 0.05). Serum albumin concentration is closely correlated with albumin mRNA content (r = 0.895, P less than 0.01). These data suggest that albumin concentration is mainly regulated at albumin mRNA level in the liver despite the presence of other regulatory mechanisms and that expression of albumin mRNA level is correlated with disease severity. But in several cases there was a discrepancy between albumin mRNA level and severity of liver disease, so further investigation of the regulatory factors of albumin gene expression should be performed.

Albumin and collagen gene regulation in alcohol- and virus-induced human liver disease

Common features of chronic alcoholic liver disease are progressive hypoalbuminemia and a spectrum of liver fibrosis. The molecular mechanisms that account for these effects are still the subject of controversy. Therefore, in the present study we evaluated albumin and collagen gene expression in livers of alcohol abusers and patients with virus-induced liver disease. Albumin and pro alpha 1(I) collagen messenger RNA levels were determined in 30 patients who underwent diagnostic liver biopsy. Of 14 alcoholics, 7 had alcoholic hepatitis alone and the other 7 had cirrhosis plus alcoholic hepatitis. Of 16 nonalcoholic patients with chronic viral infection, 6 had chronic active hepatitis and 10 had cirrhosis plus chronic active hepatitis. Total RNA was extracted from a portion of each biopsy specimen, hybridized with a human albumin or collagen complementary DNA clone, and compared with 2 normal surgical specimens, which served as controls. The Northern hybridization studies showed that (a) despite the presence of inflammation and fibrosis, the albumin messenger RNA levels of alcoholics were similar to those of the controls; (b) these alcoholics had significantly higher levels of albumin messenger RNA than did patients with similar histological levels of disease due to viral infection; and (c) all the categories of patients had markedly increased procollagen messenger RNA levels compared with controls. Given these results it is tempting to speculate that alcohol may actually increase albumin messenger RNA content in humans as it does in animals. Furthermore, the increased procollagen messenger RNA levels in fibrotic livers suggest that an increase in collagen syntheses may be a significant factor in the pathogenesis of hepatic fibrosis.

Apolipoprotein AI is a serum and tissue marker of liver fibrosis in alcoholic patients

The aim of this study was to assess the specific correlation of apolipoprotein-AI to hepatic fibrosis in alcoholic patients. Four hundred eighty two patients were prospectively included with serum measurement of apolipoprotein-AI within 10 days before liver biopsy. Pathologic features were semiquantitatively assessed by two observers. In 28 patients liver biopsy was used for histomorphometric assessment of fibrosis and immunohistochemical labeling of apolipoprotein-AI. Serum apolipoprotein-AI was negatively correlated to semiquantitative score of fibrosis (r = -0.50; p less than 0.001), independently of the scores of steatosis and alcoholic hepatitis (r = -0.44; p less than 0.001) and of the value of serum albumin, bilirubin, and prothrombin time (r = -0.22; p less than 0.001) and independently of the nutritional parameters (r = -0.29; p less than 0.009). The mean value of apolipoprotein-AI decreased according to the grade of fibrosis from 220 +/- 6 mg/dl (mean +/- SEM) to 110 +/- 8 mg/dl. Serum apolipoprotein-AI was negatively correlated to the percentage of fibrosis (r = -0.70; p less than 0.001) in the biopsies morphometrically assessed. The labeling was superimposed to the extracellular matrix. In conclusion, this study shows that decrease of apolipoprotein-AI is a serum and tissue marker of liver fibrosis independently of steatosis, alcoholic hepatitis, liver function tests, and nutritional parameters.

Liver collagen mRNA and serum amino-terminal peptide of type III procollagen (PIIINP) levels in patients with alcoholic liver disease

We have investigated the alpha 1 (I), alpha 2 (I) and alpha 1 (III) liver collagen mRNA levels in 38 patients with alcoholic liver disease. The patients were divided into 3 groups according to the severity of their liver disease. Liver collagen mRNA levels were estimated by densitometric analysis after hybridization with the corresponding cDNA. Serum amino-terminal peptide of type III procollagen (PIIINP) was determined by radioimmunoassay in 30 patients. The results indicated that there was no increase but rather a decrease in the liver alpha 1 (I), alpha 2 (I) and alpha 1 (III) collagen mRNA in patients with the most severe liver lesions as compared to those with minimal changes. This decrease was significant for alpha 2 (I) and alpha 1 (III) cDNA probes. In contrast, serum PIIINP levels showed a positive correlation with the severity of the disease. Thus this study indicates that collagen accumulation in the liver as well as elevation of the serum PIIINP during the development of alcoholic liver disease probably reflects posttranscriptional events in collagen synthesis.

Proline-incorporating cells in chronic active liver diseases

The incorporation of 3H-proline in cells of liver biopsy specimens from patients with chronic active liver diseases has been studied by light and electron microscopic autoradiography. The labeled proline is incorporated by hepatocytes of the external rows of the residual liver lobule, by the cells of the proliferating bile ductule and very actively by the plasma cells localized at the boundary between the inflammatory infiltrate and the liver lobule. These plasma cells, which are often in close contact with the hepatocytes at the edge of the liver lobule, appear to be either negative or positive after the immunohistochemical tests for the k and lambda chains of immunoglobulins. Results are discussed in relation to both the synthesis of collagen and the role of the immunocompetent cells during the process of the piecemeal necrosis.

Liver fibrosis and extracellular matrix

Liver fibrosis and extracellular matrix play a central role in liver function impairment. Little information is available on the dynamic aspects and the natural history of fibroplasia, even if there is growing evidence that extracellular matrix accumulation (collagen I, III, IV, fibronectin, laminin, proteoglycans, etc.) is not to be considered only a passive structural support for damaged hepatic tissue, but may actively modulate liver cell behaviour. Clinicians need to date liver fibrosis and to monitor connective tissue synthesis and degradation, but attempts to develop reliable serological markers for collagen metabolism are hampered by the absence of a well defined golden standard to validate them. Nevertheless, serum type III aminoterminal procollagen peptide, at the moment, seems to be the most acceptable parameter of fibrogenesis. The data concerning the mechanisms of collagen production-degradation are becoming so precise and numerous that even if they have not, to date, led to 'routine' advantages for patients, they will end up becoming important tools in the clinical practice and management of liver fibrosis.