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Effect of transforming growth factor beta on cell death of cultured rat hepatocytes
F Oberhammer1, W Bursch, W Parzefall
1Institut für Tumorbiologie-Krebsforschung Universität Wien, Vienna, Austria.
Abstract:
We investigate mechanisms of regression of liver hyperplasia which occurs after induction of growth by hepatomitogens and their subsequent withdrawal. We hypothesized that transforming growth factor beta 1 (TGF-beta 1) might be involved in the control of regression. Therefore we studied the effect of this agent on DNA synthesis and death of hepatocytes cultured in vitro. Both the low basal rate of DNA synthesis of untreated cells and its increase by epidermal growth factor (10 ng/ml) were suppressed by TGF-beta 1 at concentrations higher than 0.01-0.1 ng/ml. At the same range of concentrations of TGF-beta 1, the DNA content of the cultures declined significantly and numerous dead cells could be seen in the monolayer. Time course studies showed that TGF-beta 1 (1 ng/ml) decreased DNA content in the cultures linearly to 41 +/- 7% of controls during a period of 48 h. A similar decrease occurred with vital hepatocytes in hematoxylin and eosin stained monolayers. These changes were accompanied by an extensive release of lactate dehydrogenase which began at 20 h and was 70% of the total lactate dehydrogenase content of the cultures at 40-48 h. Little formation of guanidine hydrochloride resistant bodies and no fragmentation of DNA, indicators of apoptotic cell death, were detected after TGF-beta 1 (1 ng/ml) treatment. Time lapse cinematography revealed an active detachment of the cells from the underlying collagen gel. These studies show that inhibition of DNA synthesis by TGF-beta 1 is associated with enhanced cell death in cultured hepatocytes.
Insights
Transforming growth factor beta 1 (TGF-β1) inhibits liver cell DNA synthesis and promotes cell death during liver hyperplasia regression. This study reveals TGF-β1
Area of Science:
- Hepatology
- Cell Biology
- Molecular Biology
Background:
- Liver hyperplasia can be induced by growth factors and subsequently regress.
- The mechanisms controlling liver regression after mitogen withdrawal are not fully understood.
Purpose of the Study:
- To investigate the role of transforming growth factor beta 1 (TGF-β1) in the regression of liver hyperplasia.
- To elucidate the effects of TGF-β1 on hepatocyte DNA synthesis and cell death in vitro.
Main Methods:
- Primary hepatocyte cultures were treated with TGF-β1.
- DNA synthesis was measured using [3H]-thymidine incorporation.
- Cell death was assessed by lactate dehydrogenase release and cell morphology.
- Time-lapse cinematography was used to observe cell behavior.
Main Results:
- TGF-β1 suppressed both basal and epidermal growth factor-stimulated DNA synthesis in hepatocytes.
- TGF-β1 significantly decreased DNA content and induced cell death at concentrations above 0.01-0.1 ng/ml.
- Cell death induced by TGF-β1 was characterized by cell detachment rather than apoptosis.
Conclusions:
- TGF-β1 plays a crucial role in the regression of liver hyperplasia by inhibiting hepatocyte proliferation and promoting cell death.
- TGF-β1-induced cell death in hepatocytes involves active detachment rather than classical apoptotic pathways.