Related Experiment Videos
Transforming growth factor-beta suppresses proliferation of rabbit corneal endothelial cells in vitro
1Schephens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
Abstract:
Corneal endothelial cells in vivo appear to be inhibited in G1 phase of the cell cycle. Studies were carried out to determine whether cultured rabbit corneal endothelium expresses transforming growth factor-beta (TGF-beta) receptor types I, II, and III, suggesting they would be sensitive to a TGF-beta-induced signal. In addition, we explored if TGF-beta might mediate this G1 phase inhibition by implementing flow cytometry and 5-bromo-2'-deoxyuridine (BrdU) immunofluorescence. Reverse transcription-polymerase chain reaction (RT-PCR) products of the expected size were obtained for all three TGF-beta receptor types. Flow cytometry revealed a dose-dependent suppression in the percentage of S phase cells in cultures treated with TGF-beta1 or TGF-beta2. The lowest percentage of S phase cells was found for 10 ng/ml TGF-beta1 and 0.1 ng/ml TGF-beta2. BrdU, an S phase marker, was immunolocalized, and semiquantitative analysis of stained cells showed a maximum suppression of S phase entry at 18 h for 10 ng/ml of TGF-beta11 and 24 h for 10 ng/ml of TGF-beta2. In rabbit, the corneal endothelium expresses TGF-beta receptor types I, II, and III, permitting a TGF-beta signal to be transduced. Flow cytometry reveals a dose-dependent response to both TGF-beta1 and TGF-beta2, and the cells are more sensitive to TGF-beta2. At optimal TGF-beta concentrations, the percentage of S phase cells is comparable to that of a non-proliferating culture, suggesting TGF-beta prevents the cells from proceeding through the G1/S phase transition. This suppression was also seen with BrdU labeling. Together, these results indicate that TGF-beta could be one of the pathways that leads to G1 phase arrest in corneal endothelial cells.
Insights
Transforming growth factor-beta (TGF-beta) inhibits corneal endothelial cell proliferation. Rabbit corneal endothelium expresses TGF-beta receptors, and TGF-beta treatment arrests cells in the G1 phase, suggesting its role in regulating cell cycle.
Area of Science:
- Cell Biology
- Ophthalmology
- Molecular Biology
Background:
- Corneal endothelial cells (CECs) normally exhibit limited proliferation in vivo, often arrested in the G1 phase of the cell cycle.
- Understanding the molecular mechanisms regulating CEC proliferation is crucial for corneal health and regenerative medicine.
Purpose of the Study:
- To investigate the expression of transforming growth factor-beta (TGF-beta) receptors (types I, II, and III) in rabbit corneal endothelium.
- To determine if TGF-beta can inhibit CECs' cell cycle progression, specifically the G1 to S phase transition.
- To elucidate the potential role of TGF-beta in mediating the G1 phase arrest observed in vivo.
Main Methods:
- Reverse transcription-polymerase chain reaction (RT-PCR) to detect TGF-beta receptor gene expression.
- Flow cytometry to quantify cell cycle phases (S phase) after TGF-beta treatment.
- 5-bromo-2'-deoxyuridine (BrdU) immunofluorescence to label cells in S phase and assess proliferation.
Main Results:
- All three TGF-beta receptor types (I, II, and III) were detected in cultured rabbit corneal endothelium via RT-PCR.
- Treatment with TGF-beta1 and TGF-beta2 resulted in a dose-dependent decrease in the percentage of S phase cells.
- BrdU labeling confirmed that TGF-beta suppressed the entry of cells into S phase, with maximum inhibition observed at specific time points and concentrations for TGF-beta1 and TGF-beta2.
- Corneal endothelial cells demonstrated higher sensitivity to TGF-beta2 compared to TGF-beta1.
Conclusions:
- Rabbit corneal endothelium expresses functional TGF-beta receptors, making it responsive to TGF-beta signaling.
- TGF-beta effectively inhibits corneal endothelial cell proliferation by preventing progression through the G1/S phase transition.
- TGF-beta is identified as a key signaling molecule potentially responsible for the G1 phase arrest of corneal endothelial cells in vivo.