Radioimmunoassay for aminoterminal procollagen peptides in liver disease

Biochemical markers of hepatic fibrosis

Most liver diseases lead to a pathobiochemical reaction termed liver fibrosis. This is a dynamic process implying different rates of progression or regression. Thus, histological examination of a liver biopsy is essential for a diagnosis but biochemical tests are necessary for assessing the activity of the process and monitoring its evolution. We review the most important constituents of liver connective tissue and the biochemical tests developed for evaluating liver fibrosis. The aminopeptide of type III procollagen is the most widely used parameter: two different radioimmunoassays have been developed with different affinities for the two circulating forms of the molecule. The determination of serum P3P reveals an elevation of blood levels both in acute and chronic liver diseases. In the first, serum P3P is an index of hepatic necrosis and inflammation which correlates with other biochemical parameters. In the second it is an index of active fibrogenesis. Moreover, in primary biliary cirrhosis this parameter is an independent prognostic variable and an important predictor of survival. Other immunoassays exist for different collagen cleavage products, but their clinical value is not established. Laminin and fibronectin are the principal structural glycoproteins in liver. Fibronectin determination does not seem to be of clinical value in liver disease. In contrast, serum laminin correlates with the severity of portal venous pressure in advanced liver disease. Its concentration parallels the severity of varices and may indicate the risk of bleeding. Hyaluronate is a high molecular weight polysaccharide, raised serum concentrations reflect both its increased synthesis by activated fibroblasts and its impaired catabolism by the liver. Thus, it may be useful for evaluating and monitoring the progression of chronic liver disease. The measurement of the activity of prolyl 4-hydroxylase as well as that of lysine oxidase and other enzymes has been proposed, but their clinical value is not sufficiently demonstrated. A panel of tests (e.g., laminin, hyaluronate and the aminopeptide of type III procollagen) seems to be recommended for a biochemical assessment of liver fibrosis in clinical practice.

Serum type III procollagen peptide and laminin (Lam-P1) detect alcoholic hepatitis in chronic alcohol abusers

The diagnosis of alcoholic hepatitis is difficult to establish by conventional clinical and laboratory methods, and a firm diagnosis relies on liver histology. Since there are severe limitations in following patients with repeated liver biopsies, noninvasive procedures are needed to assess the presence of alcoholic hepatitis in chronic alcohol abusers. It has been suggested that serum Type III procollagen peptide levels correlates with the degree of inflammation in chronic liver disease. Since inflammation is a major histological finding in alcoholic hepatitis, we therefore studied the usefulness of measuring serum Type III procollagen peptide and laminin values in 45 consecutive chronic alcohol abusers, with or without cirrhosis, in detecting those with alcoholic hepatitis. The results showed that both Type III procollagen peptide and laminin values were elevated in all of the patients with established liver damage. However, the values were highest in those with liver cirrhosis plus alcoholic hepatitis (Type III procollagen peptide 50.4 +/- 36.4 ng per ml vs. 8.1 +/- 2.6 in controls, p less than 0.01; laminin 4.50 +/- 1.49 units per liter vs. 1.24 +/- 0.26 units per liter in controls, p less than 0.01), followed by subjects with alcoholic hepatitis alone (Type III procollagen peptide 23.5 +/- 17.6 ng per ml, p less than 0.01; laminin 2.60 +/- 1.09 units per liter, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Procollagen-III peptide serum levels in Paget's disease of the bone

A commercially available radioimmunoassay kit was used to determine aminoterminal procollagen-III peptide (pNcoll III) serum levels in patients with Paget's disease of the bone and control subjects. In patients with Paget's disease pNcoll III concentrations were significantly elevated. They decreased to varying degrees under chronic therapy with human and salmon calcitonin, disodium ethane 1-hydroxy 1,1-diphosphonate (EHDP), or a combination therapy of EHDP and human calcitonin. The results were compared with the effect on traditional biochemical markers of disease activity: serum alkaline phosphatase and urinary hydroxyproline excretion, both of which reacted more acutely to the various therapies than pNcoll III, although pretreatment correlations were close. The most probable source of pNcoll III is not the Pagetic bone per se, but the vascular, fibrous connective tissue replacing normal bone marrow.

Serum procollagen type III peptide as a marker of hepatic fibrogenesis in alcoholic hepatitis

To evaluate if serum procollagen type III peptide levels reflect the extent of liver fibrosis and hepatic collagen synthesis, we have studied 19 patients with histologically proven alcoholic hepatitis and 9 chronic alcoholics with normal liver histology or minimal steatosis. Serum procollagen peptide type III was measured at the time of liver biopsy, and determination of hepatic prolyl-hydroxylase activity, as an index of collagen synthesis, was performed in all liver samples. Hepatic prolyl-hydroxylase activity and serum procollagen peptide levels were significantly higher in patients with alcoholic hepatitis (959 +/- 115 cpm/mg and 33.2 +/- 5.3 ng/ml, respectively) than in alcoholics from the control group (537 +/- 62 cpm/mg and 10.9 +/- 1.5 ng/ml, respectively) (p less than 0.05 and p less than 0.01, respectively). All patients with alcoholic hepatitis had fibrosis (10 mild and 9 severe). Prolyl-hydroxylase activity and procollagen peptide levels were significantly higher in alcoholic hepatitis patients with severe fibrosis than in those with mild fibrosis (1208 +/- 154 cpm/mg vs. 734 +/- 138 cpm/mg, p less than 0.05 and 49.1 +/- 8.8 ng/ml vs. 20.4 +/- 2.6 ng/ml, p less than 0.01). Furthermore, a close correlation was found between the hepatic prolyl-hydroxylase activity and the serum level of procollagen peptide (r = 0.76, p less than 0.001). We conclude that the serum procollagen peptide level is a good marker of hepatic fibrogenesis in alcoholic hepatitis; thus, its serial measurement could be useful in identifying patients in progress to cirrhosis and in assessing the therapeutic efficiency of antifibrogenic drugs.

Etiopathogenesis of otosclerosis: a hypothesis

It is hypothesized that otosclerosis is an autoimmune disease in response to native type II collagens of cartilage rests associated with globular ossei in the endochondral layer of the otic capsule. To support this hypothesis animal experimental data and human antibody data are shown.

Procollagen production by rat hepatocytes in primary culture

Hepatocytes were obtained from rat liver and maintained in primary culture for periods up to 14 days. Collagen synthesis was maximal after 3-5 days and declined thereafter. The rate of collagen production was approx. one-tenth that observed by rat skin fibroblasts of the same animals after 3-5 passages. Type I procollagen, the major macromolecular collagenous species, was identified as a 450 000 dalton molecule which was converted to 120 000 dalton, denatured, reduced procollagen chains. Prior pepsin digestion of the native procollagen released 95 000 dalton collagen chains identified as alpha 1(I) and alpha2(I) by co-migration with carrier rat skin type I collagen chains. The production of type III procollagen was also tentatively identified by DEAE-cellulose chromatography. This material was isolated and identified with type-specific antibodies developed against the amino-terminal extension peptide of bovine skin type III procollagen. The relative distribution of type I:type III procollagen was estimated at 7:3 similar to the ratio previously found in whole rat liver. No evidence of type IV or type V procollagen biosynthesis was observed. These results suggest that rat hepatocytes in primary culture are capable of interstitial type I and type III collagen biosynthesis in a ratio similar to that found in their parent hepatic tissue in situ. They also suggest that the less abundant type IV (basement membrane-associated) or type V are not major collagenous products of these cells.

Connective tissue components of the normal and fibrotic human liver. II. Clinical aspects

In this second part, clinical aspects of connective tissue metabolism in the liver will be described and two main aspects considered. The first is the possibility to monitor the activity of fibrosis by the use of metabolites and enzymes of connective tissue metabolism. In recent studies the qualification for this purpose of enzymes such as procollagen prolyl hydroxylase and lysosomal N-Acetyl-beta-glucosaminidase and the N-terminal peptide of procollagen type III has been tested. The serum activities or concentrations of these substances in patients with chronic active liver diseases increase in due relation to the histologically estimated activity of liver fibrosis. The second aspect deals with therapeutic approaches to fibrosis in the liver by using connective tissue specific agents. So far none of the antifibrotic substances such as proline analogues, colchicine, lathyrogens and penicillamine has been used in longer-term antifibrotic treatment.

Radioimmunoassay for type III procollagen peptide and its application to human liver disease

A sensitive and specific radioimmunoassay was developed for the precursor-specific peptide segment located at the amino end of bovine type III procollagen. Human material showed high cross-reactivity in this assay. Two forms of human procollagen peptides were detected in body fluids. The larger peptide (45K) was found in serum and ascites, and resembled the whole precursor-specific segment which is presumably released from human type III procollagen by a single enzymatic cleavage. The smaller peptide (10K) was found mainly in urine indicating that further degradation of circulating procollagen peptides is required prior to their passage through the kidney. Compared to peptide concentrations in normal human serum two to twenty-fold increases were observed in all patients with alcoholic liver disease, in fifteen of seventeen patients with acute hepatitis, and in ten of fourteen patients with chronic active hepatitis. Much higher levels were detected in ascites fluid. Patients with rheumatoid arthritis and other diseases showed far smaller elevations of the serum peptide. In alcoholic liver disease peptide levels correlated well with inflammation and necrosis observed in liver biopsies, but not with other laboratory parameters.