The role of survivin in liver regeneration
Zusammenfassung der Projektergebnisse
In this project, we investigated the role of survivin in liver regeneration. In our first approach we investigated liver regeneration in rats after 70% resection and in humans after living-related liver transplantation. We found a significant increase of survivin RNA expression and protein expression during liver regeneration in rodents as well as in humans. The survivin expression correlated significantly with the degree of hepatocyte proliferation but not with the extent of apoptosis. By means of immunohistochemistry the survivin immune-localization was predominantly in hepatocytes. To investigate the role of survivin in liver regeneration we used two different genetic mouse models: 1. heterozygous survivin KO+/- 2. hepatocyte-specific survivin KO-/-. Both genetic models were forced to regenerate by 70% liver resection. Heterozygous survivin KO+/-. As deletion of survivin is embryonically lethal, we investigated mice heterozygous for the gene. Although phenotypically normal, this mouse has been shown to display increased basal levels of procaspase activation and an increased rate of Fas-induced apoptosis in the liver. This suggests that a reduction of survivin by half is already significant in liver pathophysiology. We performed 70% liver resection and determined liver regeneration after 2, 4, and 7 days. We observed that liver regeneration was clearly impaired after 2 days in the heterozygous survivin KO+/-. This went along with a significant increase in plasma GOT and GPT values compared to controls and a ~10-fold decrease in hepatocyte proliferation as measured by BrdU incorporation. The number of hepatocytes on histology was also reduced by ~15%. However, after 4 and 7 days, no differences were observed in any of the above parameters between survivin KO+/- and controls. This suggests that heterozygous deletion of survivin results in a transient impairment of liver regeneration that can be compensate over time. Hepatocyte-specific survivin KO-/-. Conditional hepatocyte-restricted survivin KO mice were generated by using the Cre-Lox recombination technique. Mice with floxed survivin gene were crossbred with mice expressing Cre under the albumin promoter. The offspring were vital, fertile and showed no phenotype. Gross examination of the liver showed no alteration, however, histologically the hepatocytes and their nuclei were larger. This together with a normal liver weight / body weight-ratio prompted us to determine the total hepatocyte number by a 3-dimensional stereological approach. The total number of hepatocytes in survivin-deficient mice was significantly decreased (by 63%) compared to wild type (WT). The appearance of enlarged nuclei directed us to measure their DNA content using automated DNA cytometry. Survivindeficient hepatocytes showed an increased DNA content with individual cells exhibiting DNA-content up to 28n. After 70% liver resection, the KO mice showed insufficient increase of total hepatocytes. While the liver weight / body weight-ratio increased equally compared to controls, the hepatocytes enlarged even further. The proliferation determined by Ki-67 was significantly lower in KO liver compared to WT mice. Since survivin is a member of the chromosomal passenger complex, we studied other passenger proteins (aurora B and INCENP). Compared to WT mitosis, both aurora B and INCENP were not correctly localized at centromeres, which implicates a dysfunction of the chromosomal passenger complex. In conclusion, we showed that survivin is expressed during liver regeneration in rodents and humans. Deletion of survivin causes a chromosomal segregation defect with the generation of polyploid hepatocyte nuclei and an impairment of proliferation. The cause is a disturbed spatial distribution of the chromosomal passenger complex.
Projektbezogene Publikationen (Auswahl)
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Evaluation of a modified HTK solution containing the new iron chelator LK 614 in an isolated rat liver perfusion model. J Invest Surg 2009, 22: 340-347
Wu S, Wohlschlaeger J, de Groot H, Rauen U
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Survivin is upregulated during liver regeneration in rats and humans and is associated with hepatocyte proliferation. Liver Int 2009, 29: 585-592
Baba HA, Wohlschlaeger J, Schmitz KJ, Nadalin S, Lang H, Benesch A, Gu Y, Biglarnia AR, Sotiropoulos GC, Takeda A, Takeda N, von Wnuck Lipinski K, Levkau B
