Hiromitsu Hamaguchi

Effect of cyclosporine on liver regeneration after orthotopic reduced-size hepatic transplantation in the rat

These experiments were undertaken to study the effects of cyclosporine A (CsA) on liver regeneration after an isogeneic orthotopic reduced-size hepatic transplantation (RSHT) in rats. Male Wistar rats were treated with or without a daily injection of CsA beginning 24 hr before surgery and were subjected to a 68% partial hepatectomy. A isogeneic orthotopic reduced-size hepatic transplantation was performed in recipient rats pretreated with or without CsA. A daily injection of CsA was continued until the recipient rats were sacrificed. Animals were sacrificed at various time points (12, 24, 36, 48, and 72 hr) postoperatively. The incorporation of bromodeoxyuridine (BrdU) into the DNA of the remnant hepatocytes was evaluated by immunohistochemical staining with a monoclonal antibody against BrdU. CsA (10 mg/kg/day) significantly augmented BrdU incorporation into hepatocytes after hepatectomy. The maximum labeling index (LI) was observed at 24 hr after hepatectomy. In contrast, the maximum LI in the recipient rats not receiving CsA was seen at 36 hr after RSHT, and 10 mg/kg/day of CsA decreased the LI at 36 hr after RSHT. A lower dose of CsA (3 mg/kg/day), however, significantly increased the LI in the recipient rats (P<0.01), and it reached a peak at 24 hr after RSHT when compared to the transplant recipients not receiving CsA. The time course of the increase in the LI in the transplant recipient rats receiving 3 mg/kg/day of CsA was similar to that observed in the rats after hepatectomy. This dosage improved the delay in the reduced-size hepatic transplant LI reaching its peak. These findings suggest that after RSHT the liver graft is more sensitive to both hepatotrophic and hepatotoxic effects of CsA.

PROLONGED SURVIVAL OF RAT HEPATIC ALLOGRAFTS AFTER TOTAL-BODY IRRADIATION OF THE DONORS

&NA; The effect of total-body irradiation of the donor on hepatic allograft survival was studied in the rat, with ACI(RT1a) as the donor and LEW(RT1) as the recipient. LEW recipients of ACI liver transplants experienced severe acute rejection, with a mean survival of only 10.2±0.3 days. The doses of irradiation were 450, 750, and 1000 rads administered 24 hr prior to harvesting or subsequent transplantation. TBI with a dose of 750 rads significantly prolonged the survival of the hepatic allograft to 30.3±1.7 days, without concomitant immunosuppression. However, neither 450 rads nor 1000 rads of TBI resulted in successful suppression of graft rejection. TBI appeared to have a beneficial effect on hepatic allograft survival and to have no deleterious effect on isograft survival, suggesting a possible modulation of the immunogenicity of the donor organ. Although the cause of this beneficial effect is not clear, TBI with a dose of 750 rads 24 hr prior to organ harvest seems to be optimal to eliminate-antigen presenting cells in the donor organs.

Recombinant Human Hepatocyte Growth Factor Facilitates Biliary Transport After Hepatocyte Transplantation in Eisai Hyperbilirubinemic Rats

Hepatocyte transplantation may offer anattractive treatment for inborn errors of livermetabolism. However, factor(s) are required as stimulito induce proliferation of the limited number ofhepatocytes transplanted. The Eisai hyperbilirubinemic rat(EHBR) is a SpragueDawley (SD) mutant rat withconjugated hyperbilirubinemia. EHBRs have impairedcanalicular excretory transport of organic anions, bileacid glucuronide, and sulfate. Recombinant humanhepatocyte growth factor (rhHGF) (100 μg/kg) wasinjected intravenously at 2-hr intervals for 10 hr,immediately and 35 days following the intraportalinjection of 1 × 107 wild-type SD rathepatocytes. Serum bilirubin concentrations decreasedsignificantly within 35 days and were maintained atsignificantly reduced levels for 120 days followingtransplantation. Biliary excretion was demonstrated by the biliarytransport of indocyanine green and sulfobromophthaleinsodium into the bile. These results indicate thathepatic transport of bile acid conjugates in EHBRs can be restored by hepatocyte transplantationcombined with repeated administration of exogenousrhHGF, in conjunction with functioning of therecipients excretory biliary system.

Effect of Cyclosporine on Distribution of Macrophage Subpopulations in Rat Hepatic Allograft

Macrophage subpopulations infiltrating the grafts of ACI(RT1a) to LEW(RT11) orthotopic rat liver transplants treated with or without immunosuppressive therapy were studied using immunohistochemical staining. LEW recipients of ACI liver transplants experienced severe acute graft rejection, with a mean survival of only 10.2±0.7 days. An indirect immunoperoxidase technique on cryostat sections of the liver grafts was used to determine the localization of macrophage subpopulations infiltrating the grafts, as defined by specific anti-rat macrophage monoclonal antibodies, designated TRPM-1 (panmacrophage), TRPM-3 (activated macrophage) and Ki-M2R (tissue macrophage). TRPM-1+ or TRPM-3+ cells gradually increased on days 5 and 7 in the untreated hepatic allografts, whereas no significant changes in the number of these cells were observed in the isografts. Treatment with cyclosporine (CsA) greatly decreased the number of these two different types of cells infiltrating the hepatic allografts, compared to the untreated hepatic allografts or the isografts. The time course of the accumulation of these cells in the allografts treated with CsA showed a similar pattern; the cells increased gradually by day 5 and thereafter decreased. This pattern is different from that observed in the untreated allografts or in the isografts. There was no significant difference in the number of Ki-M2R+ cells between the untreated hepatic allografts and the isografts. However, the number of the Ki-M2R+ cells in the hepatic allografts treated with CsA was much less than that of either the untreated allografts or the isografts. These findings suggest that a progressive relative increase in host TRPM-3+ macrophage is a characteristic feature of ongoing first-set rejection in the rat hepatic allograft. The administration of CsA significantly decreased the number of macrophages infiltrating the allograft, even when compared with the isografts.