ENHANCEMENT OF PROLIFERATION OF INTRASPLENICALLY TRANSPLANTED HEPATOCYTES IN CIRRHOTIC RATS BY HEPATIC STIMULATORY SUBSTANCE1

Abstract

This study aimed at investigating the efficacy of hepatic stimulatory substance (HSS) on the proliferation of transplanted hepatocytes in the spleen of rats with carbon tetrachloride (CCl4)-induced liver cirrhosis. After hepatocyte transplantation (HTx; 1x10(7) cells/rat), the recipients received intravenous administration of HSS (3ml) of 2, 4, or 7 times/week to investigate the effect of the frequency of HSS treatment on the proliferation of intrasplenically transplanted hepatocytes. Next, to investigate the effect of the severity of liver cirrhosis on HSS-stimulated proliferation of transplanted hepatocytes, different doses (0.00, 0.08, 0.12, and 0.16 ml/week) of CCl4 were given to rats after HTx. The recipients were killed and the spleens were removed at 2 and 4 weeks after HTx and stained with bromodeoxyuridine (BrdU) and hematoxylin and eosin for determining the BrdU labeling index (L.I.) and the hepatocyte-occupied area ratio in the longitudinal cut surface of the spleen (H:S ratio), respectively. The H:S ratio was measured in the hematoxylin and eosin-stained splenic sections under a light microscope connected to an image processor. HSS-treated rats showed significantly higher BrdU L.I. and H:S ratios than the untreated control rats at 2 and 4 weeks after HTx. However, the difference in the BrdU L.I. and H:S ratio was not statistically significant among the HSS-treated rats. Without HSS treatment, the severity of liver cirrhosis did not affect the proliferation of intrasplenically transplanted hepatocytes. On the other hand, HSS-induced proliferation of transplanted hepatocytes was further enhanced in proportion to the severity of liver cirrhosis. The H:S ratio of the rats treated with 0.04, 0.08, and 0.16 ml/week of CCl4 after HTx was 1.27+/-0.5%, 4.32+/-0.65%, and 6.25+/-0.70%, respectively, at week 4. During the long-term observation of up to 12 weeks, a marked decrease in the H:S ratio was observed in HSS-untreated control rats at weeks 4-12 compared with week 2. While HSS-treated rats revealed gradual proliferation of intrasplenically transplanted hepatocytes, the difference in the H:S ratio between HSS-treated and -untreated rats became larger. These results indicate that HSS treatment of recipient rats stimulated the proliferation of intrasplenically transplanted hepatocytes in cirrhotic rats and that the severity of liver cirrhosis enhanced the stimulative effect of HSS on the proliferation of transplanted hepatocytes.