Related Experiment Videos
Down-regulation of transforming growth factor beta receptor type I, II, and III during liver regeneration
Background:
After partial hepatectomy (PH), it has been shown that hepatocytes are resistant to the mitoinhibitory effects of transforming growth factor beta (TGF-beta). Three types of TGF-beta receptors have been characterized in mammals.
Materials And Methods:
In this study, changes in the protein and mRNA expression of TGF-beta types I, II, and III receptors relative to DNA synthesis were studied as a function of time after PH in the rat.
Results:
There was a significant decrease in the protein and mRNA for all three receptor subtypes immediately after PH. All three receptors reached a nadir at 24 hours after PH, which correlated to the time of peak DNA synthesis. The type II receptor recovered to preoperative levels by 120 hours after PH, whereas the types I and III receptors remained at 60% of prehepatectomy levels. Sham-operated rats did not experience a significant drop in receptor protein or mRNA levels.
Conclusions:
This decrease in TGF-beta type II receptor expression may account for the reduction in the sensitivity of hepatocytes to TGF-beta after PH. Furthermore, the TGF-beta receptors appear to represent a class of immediate-early genes that are negatively, rather than positively, regulated after PH.
Insights
Hepatocytes resist transforming growth factor beta (TGF-beta) after partial hepatectomy (PH). TGF-beta receptor expression decreases, potentially explaining reduced TGF-beta sensitivity during liver regeneration.
Area of Science:
- Hepatology
- Molecular Biology
- Cell Signaling
Background:
- Hepatocytes exhibit resistance to transforming growth factor beta (TGF-beta) after partial hepatectomy (PH).
- Mammals possess three characterized types of TGF-beta receptors.
Purpose of the Study:
- To investigate changes in TGF-beta receptor (types I, II, and III) protein and mRNA expression.
- To correlate these changes with DNA synthesis over time following PH in rats.
Main Methods:
- Quantification of TGF-beta receptor subtypes I, II, and III protein and mRNA.
- Time-course analysis after partial hepatectomy in a rat model.
- Comparison with sham-operated controls.
Main Results:
- A significant decrease in all three TGF-beta receptor subtypes' mRNA and protein was observed immediately after PH.
- Receptor levels reached a minimum at 24 hours post-PH, coinciding with peak DNA synthesis.
- Type II receptor normalized by 120 hours, while types I and III remained at 60% of pre-PH levels. Sham-operated rats showed no significant receptor changes.
Conclusions:
- Reduced TGF-beta type II receptor expression likely contributes to the decreased sensitivity of hepatocytes to TGF-beta after PH.
- TGF-beta receptors function as immediate-early genes, negatively regulated following partial hepatectomy.