Korean J Ophthalmol.  1999 Jun;13(1):16-24. 10.3341/kjo.1999.13.1.16.

Synthesized TGF-beta s in RPE regulates cellular proliferation

• Lee SC
• Seong GJ
• Kim SH
• Kwon OW

• KMID: 1081831
• DOI: http://doi.org/10.3341/kjo.1999.13.1.16

Abstract

Retinal pigment epithelial (RPE) cells transdifferentiate in culture, a transition which is accompanied by a shift in biological activity. The present study investigates whether transforming growth factor (TGF)-beta has the same effects on morphologically transformed RPE cells that it has on primary RPE cells. It also evaluates the autocrine and paracrine activities of TGF-beta s synthesized by RPE cells as well as the anti-TGF-beta effect of mannose-6-phosphate (M-6-P). RPE cells were subcultured at the sixth passage to induce morphological change. The effect of second passaged RPE-conditioned medium (CM) on DNA synthesis was evaluated by the incorporation of 3H-thymidine in rabbit subconjunctival fibroblasts (SCFs) and primary RPE cells. The presence of TGF-beta in RPE-CM was determined using immunoblotting analysis. And the inhibitory effect of M-6-P on cell proliferation mediated by RPE-CM was also analyzed using 3H-thymidine incorporation into DNA. TGF-beta 1, TGF-beta 2, and TGF-beta 3 inhibited the proliferation of the primary cultures of RPE cells in a dose-dependent manner, but the spindle-shaped sixth passaged RPE cells were not inhibited by these growth factors. The medium conditioned by RPE cells stimulated the proliferation of SCFs and inhibited the proliferation of primary RPE cells, in a manner similar to TGF-beta. When this medium was precipitated with either anti-TGF-beta 1, anti-TGF-beta 2, or anti-TGF-beta 3 antibodies, all three TGF-beta s, with an apparent molecular size of 25 kDa, were detected. Mannose-6-phosphate significantly blocked the effect of RPE-CM on cell proliferation. These findings indicate that RPE cells produce biologically functional TGF-beta s and that M-6-P can block the inhibitory effect of RPE-CM on cell proliferation.

Keyword

Mannose-6-phosphate; Proliferative; Vitreoretinopathy, retinal pigment epithelial cells; Transforming growth factor-beta

MeSH Terms

Animal
Cell Division/drug effects
Cells, Cultured
Comparative Study
Conjunctiva/metabolism
Conjunctiva/drug effects
Conjunctiva/cytology
Culture Media, Conditioned/pharmacology
Fibroblasts/metabolism
Fibroblasts/drug effects
Fibroblasts/cytology
Immunoblotting
Mannosephosphates/pharmacology
Pigment Epithelium of Eye/metabolism*
Pigment Epithelium of Eye/drug effects
Pigment Epithelium of Eye/cytology
Rabbits
Swine
Transforming Growth Factor beta/biosynthesis*
Transforming Growth Factor beta/antagonists & inhibitors