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Expression of three forms of melanoma growth stimulating activity (MGSA)/gro in human retinal pigment epithelial
G J Jaffe1, A Richmond, L Van Le
1Department of Ophthalmology, Duke University, Durham, North Carolina.
Purpose:
To characterize mRNA expression and protein production of the cytokine MGSA/gro in human retinal pigment epithelial (RPE) cells and to determine whether expression of MGSA/gro is modulated by serum and the cytokines interleukin 1 beta (IL-1 beta), tumor necrosis factor alpha (TNF alpha), or transforming growth factor beta (TGF beta) mediators implicated in proliferative vitreoretinopathy (PVR).
Methods:
Reverse-transcription polymerase chain reaction was used to determine the steady-state mRNA expression of three forms of MGSA/gro, alpha, beta, and gamma, by cultured human RPE cells in the presence or absence of recombinant IL-1 beta, TNF alpha, or TGF beta, or when serum-starved cells were re-fed with medium containing serum. Immunocytochemistry was used to characterize RPE cell-associated MGSA/gro protein, and immunoprecipitation of MGSA/gro from cell-conditioned medium was used to demonstrate MGSA/gro secretion.
Results:
MGSA/gro mRNA was expressed minimally under basal conditions. Expression for all three forms of MGSA/gro mRNA was induced in a dose- and time-dependent manner after exposure to IL-1 beta, to a lesser extent after exposure to TNF alpha, but not after exposure to TGF beta. Serum induced MGSA/gro alpha and gamma transcripts, but not beta transcripts. Cell-associated MGSA/gro was identified on RPE cells grown in the absence of cytokines, but MGSA/gro was not secreted under these conditions. Exposure to IL-1 beta did not consistently cause increased cell-associated MGSA/gro; however, IL-1 beta induced secretion of MGSA/gro in a time-dependent manner.
Conclusion:
MGSA/gro is produced by human RPE in response to mediators implicated in PVR. Because MGSA/gro is a pleiotropic modulator of cell proliferation and inflammation, it may contribute to the intraocular wound healing response that characterizes PVR.
Insights
Human retinal pigment epithelial cells produce the cytokine MGSA/gro, particularly when exposed to inflammatory mediators like IL-1 beta. This cytokine may play a role in proliferative vitreoretinopathy (PVR) by influencing cell proliferation and inflammation.
Area of Science:
- Ophthalmology
- Cell Biology
- Immunology
Background:
- Proliferative vitreoretinopathy (PVR) is a severe complication of retinal detachment.
- Mediators such as IL-1 beta, TNF alpha, and TGF beta are implicated in PVR pathogenesis.
- Retinal pigment epithelial (RPE) cells play a crucial role in the intraocular wound healing response.
Purpose of the Study:
- To characterize mRNA expression and protein production of MGSA/gro in human RPE cells.
- To investigate the modulation of MGSA/gro expression by serum and specific cytokines (IL-1 beta, TNF alpha, TGF beta).
- To assess the potential role of MGSA/gro in PVR.
Main Methods:
- Reverse-transcription polymerase chain reaction (RT-PCR) to quantify MGSA/gro mRNA.
- Immunocytochemistry to detect cell-associated MGSA/gro protein.
- Immunoprecipitation to confirm MGSA/gro secretion.
Main Results:
- MGSA/gro mRNA expression was low under basal conditions but significantly induced by IL-1 beta and, to a lesser extent, by TNF alpha.
- Serum induced MGSA/gro alpha and gamma transcripts, but not beta.
- IL-1 beta induced time-dependent secretion of MGSA/gro from RPE cells.
Conclusions:
- Human RPE cells produce MGSA/gro in response to inflammatory mediators relevant to PVR.
- MGSA/gro, a modulator of cell proliferation and inflammation, may contribute to the wound healing processes in PVR.