Liver ploidy

Hepatocyte ploidy in normal young rat

The aim of the present study was to examine the relation between hepatocyte size and ploidy in Sprague-Dawley rat liver. Therefore, subpopulations of hepatocytes of various sizes were separated from the isolated crude hepatocyte population either mechanically or by using centrifugal elutriation. Hepatocyte size was determined on scanning electron microscopy photographs. Ploidy of hepatocytes was assessed by flow cytometry. The crude hepatocyte population was very heterogeneous in sizes, with diameters ranging from 8 to 39 microm. Hepatocyte ultrastructure was well preserved as demonstrated by transmission electron microscopy. The distribution of hepatocytes within the ploidy classes was the following: 19.6+/-3.6% diploid, 56.2+/-3.2% tetraploid and 3.4+/-0.6% octoploid mononucleated cells. Thus approximately 79% of hepatocytes appeared mononucleated. The binucleated hepatocytes (21%) had two diploid nuclei (18.7+/-2.9%) or two tetraploid nuclei (2.1+/-0.6%). A similar distribution of hepatocytes into ploidy classes was obtained in subpopulations of hepatocytes of various sizes. Our findings suggest that distribution into ploidy classes is not strictly correlated with hepatocyte size. In accordance with previous observations, our results on hepatocyte ploidy from periportal or perivenous origin using digitonin perfusion, is in favour of the existence of ploidy zonation within the rat hepatic lobule.

Importance of detecting numerical versus structural chromosome aberrations

The aim is to review briefly the key questions related to aneuploidy/polyploidy and to compare the advantages and disadvantages of the in vitro micronucleus test to assess aneuploidy/polyploidy in vitro. The key questions that will be addressed, concern the importance of polyploidy for health, and cancer in particular, the mechanisms leading to aneuploidy and polyploidy, and the survival of aneuploid/polyploid cells. The recently recognised contribution of numerical chromosome changes to carcinogenesis triggered the development and the implementation of tests specifically aiming at the detection of aneugens in the test battery for mutagenicity and carcinogenicity. The validation of the in vitro micronucleus test in combination with the identification of in vitro divided cells with the cytokinesis-block methodology and of centromeres with pancentromeric or chromosome specific centromeric probes fluorescence in situ hybridisation (FISH) provides a sensitive, easy to score and powerful test which allows assessment of cell proliferation, the discrimination between chromosome breaks, chromosome loss and chromosome non-disjunction and polyploidy. Moreover, classic histology permits the estimation of necrosis and apoptosis on the same slide. The cytokinesis-blocked micronucleus assay could be considered as a multi-endpoint test for genotoxic responses to clastogens/aneugens. This methodology has also shown to be capable of identifying threshold values for the induction of chromosome loss and/or non-disjunction by microtubule inhibitors, data which are particularly important for risk calculations. Similar approaches were conducted in vivo on bone marrow in mice and rats (except for identification of chromosome non-disjunction), and are in development for gut in mice.

Primary malignant epithelial tumors of the liver in children: a study of DNA content and oncogene expression

Primary malignant epithelial tumors of the liver (PMETL) are rare in the pediatric age group, and very little is known about their biology as compared with adult tumors. The prognostic value of the DNA contents measured by image analysis and expression of oncogene c-erb2 and tumor suppressor gene p53 were studied in 30 cases of PMETL in children, including 24 with hepatoblastomas (HB) and 6 with hepatocellular carcinomas (HCC). p53 overexpression was detected in 12 out of 26 cases (46.0%), or in 3 of 5 HCC and 9 of 21 HB cases. A relatively high concordance of staining was observed with the two antibodies used (clone DO7, Dako and clone DO1, Santa Cruz Biotechnology). c-erb-B2 did not yield the characteristic membrane staining in any of the 27 cases in which reliable staining was obtained. However, 1 out of 4 patients with HCC and 1 of 23 with HB revealed strong granular cytoplasmic staining in several neoplastic cells. Interestingly, these were two of the three aneuploid multiploid cases. DNA histograms of 13 out of 29 cases (54.8%) were classified as DNA aneuploid (5/6 HCC and 8/23 HB): nine were hyperdiploid, one was hypodiploid (1HB), and three were multiploid (2HB and 1HCC). In the HB group, DNA aneuploidy was strongly associated with embryonal histological areas, suggesting that a disturbance in the process of cell differentiation is associated with marked genetic aberrations. Only the group of HB was submitted to univariate analysis of survival by the Kaplan-Meier method for age (< 24 months vs. > or = 24 months), sex, preoperative chemotherapy (yes vs. no), residual disease (metastasis, and/or unresectable tumor), p53 expression by immunohistochemistry (positive vs. negative), and DNA ploidy (diploid vs. aneuploid). Only residual disease at the time of diagnosis (P < 0.017) and preoperative chemotherapy (0.030) were found to be negatively correlated with biological behavior, estimated as overall survival. DNA aneuploidy tumors (P < 0.125) and male patients (P = 0.123) showed a trend toward a more aggressive clinical behavior, although the difference was not statistically significant. Combining DNA ploidy and residual disease, patients were categorized into three groups: group I, patients with no adverse prognostic factors, i.e., diploid tumors without residual disease; group II, patients with only one adverse prognostic factor, i.e., aneuploid tumor or residual disease; and group III, patients with both adverse factors, aneuploid tumors and residual disease at time of diagnosis. A log-rank test comparing the three survival curves showed a statistically significant difference between them (P < 0.003). Although the series of cases is small, the results of this study highlight the importance of including DNA ploidy in the protocols designed for HB in children by international cooperative groups.

Diagnostic and prognostic value of DNA ploidy and cell nuclearity in ultrasound-guided liver biopsies

BACKGROUND

Focal nodule lesions in patients with cirrhotic livers may be visualized by using imaging techniques; however, the diagnostic and prognostic judgment of biopsies from borderline lesions may be difficult using conventional histologic criteria.

METHODS

The diagnostic and prognostic value of DNA ploidy analysis determined by image cytometry of Feulgen-stained isolated hepatocytes was investigated in ultrasound-guided biopsies from 50 nodular lesions found in patients with cirrhotic livers (39 hepatocellular carcinomas [HCCs] and 11 macroregenerative nodules) and from 10 patients with livers affected by viral chronic hepatitis. Of the 11 macroregenerative nodules, 7 presented a subsequent neoplastic behavior. Specimens from the morphologically normal livers of five patients who underwent liver surgery served as control tissues. Image cytometry was performed on Feulgen-stained cytologic preparations, obtained by enzymatic digestion of formalin fixed biopsies. The DNA ploidy of the main stem line and the distribution of mononucleated and binucleated hepatocytes (nuclearity) were compared using histologic diagnosis, Edmondson's grade, tumor size, and patient follow-up.

RESULTS

The main stem line was peridiploid in all benign specimens and in 31 clinically confirmed HCCs, peritetraploid in 11 HCCs, perioctaploid in 1 HCC, and aneuploid in 3 HCCs. The fraction of mononucleated polyploid hepatocytes was found to be the best diagnostic parameter in euploid HCCs and was significantly correlated with the Edmondson grade and the nodular size. Survival information was available for 43 patients, with a median observation period of 350 days. A DNA ploidy value of the main stem line greater than 3c was an important determinant of survival as a single parameter and in association with histologic grade and greatest dimension of tumor.

CONCLUSIONS

This study suggests that the ploidy distribution analysis of mononucleated and binucleated hepatocytes can provide valuable information for making correct diagnoses and for predicting survival outcome for patients with HCCs.