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Apoptosis in proliferative vitreoretinal disorders: possible involvement of TGF-beta-induced RPE cell apoptosis
P Esser1, K Heimann, K U Bartz-schmidt
1Department of Vitreoretinal Surgery, University Eye Clinic Cologne, Germany.
Abstract:
The targeted induction of apoptosis is a novel therapeutic approach to control the unlimited growth of proliferating cells. Since massive proliferation of cells at the vitreoretinal interface is a key feature of proliferative vitreoretinal disorders, we sought to identify apoptosis in epiretinal membranes from patients with proliferative vitreoretinopathy (PVR), proliferative diabetic retinopathy (PDR) and macular pucker. Further, we evaluated the possible induction of apoptosis of retinal pigment epithelial (RPE) cells by transforming growth factor-beta(TGF-beta). Apoptotic cells were identified by in situ DNA end labeling and acridine orange staining on paraffin-embedded tissue sections from epiretinal membranes of patients with all vitreoretinal disorders examined. Labeled nuclei or condensed chromatin were scattered throughout the membranes or occurred in clusters. Most apoptotic cells were RPE-derived, as assessed by cytokeratin immunochemistry. No apoptotic glial cells were detected. In PVR, proliferative activity, as confirmed by Ki-67 immunochemistry, was associated with short history and rapid disease progression. Apoptotic nuclei were observed more frequently in long-standing PVR or slow progression towards traction retinal detachment. TGF-beta was detected in all control vitreous samples by bioassay at concentrations below 20 ng ml-1. TGF-beta levels increased up to 20-fold in pathological vitreous. Marked heterogeneity was observed in all patient groups. The degree of TGF-beta activation was significantly higher in PVR than in PDR. Proapoptotic effects of TGF-beta were demonstrated in cultured human RPE cells by electron microscopy, in situ DNA end labeling, comet assay and a photometric enzyme immunoassay for histone-associated DNA fragments. Apoptosis appears to be a key regulatory mechanism of growth control of specific cell populations in proliferative vitreoretinal disorders. Administration of proapoptotic growth factors such as TGF-beta may provide a novel approach to inhibit cellular proliferation at the vitreoretinal interface.
Insights
Targeted apoptosis induction is a novel therapy for proliferative vitreoretinal disorders. Transforming growth factor-beta (TGF-beta) induces apoptosis in retinal pigment epithelial cells, offering a potential treatment to control cell growth.
Area of Science:
- Ophthalmology
- Cell Biology
- Molecular Medicine
Background:
- Proliferative vitreoretinal disorders are characterized by excessive cell proliferation at the vitreoretinal interface.
- Targeted induction of apoptosis offers a potential therapeutic strategy to manage uncontrolled cell growth.
Purpose of the Study:
- To identify apoptosis in epiretinal membranes from patients with proliferative vitreoretinopathy (PVR), proliferative diabetic retinopathy (PDR), and macular pucker.
- To evaluate the potential of transforming growth factor-beta (TGF-beta) to induce apoptosis in retinal pigment epithelial (RPE) cells.
Main Methods:
- In situ DNA end labeling and acridine orange staining on epiretinal membrane sections.
- Cytokeratin and Ki-67 immunochemistry to identify cell types and proliferative activity.
- Bioassays and enzyme immunoassays to quantify TGF-beta levels and assess RPE cell apoptosis in vitro.
Main Results:
- Apoptotic cells, primarily RPE-derived, were found in epiretinal membranes across all examined vitreoretinal disorders.
- Higher TGF-beta levels were observed in pathological vitreous, with significantly greater activation in PVR than PDR.
- TGF-beta demonstrated proapoptotic effects on cultured human RPE cells.
Conclusions:
- Apoptosis is a critical regulatory mechanism controlling cell populations in proliferative vitreoretinal disorders.
- TGF-beta plays a significant role in inducing apoptosis in RPE cells.
- Administration of proapoptotic factors like TGF-beta may represent a novel therapeutic approach for these conditions.