Production of latent transforming growth factor-beta and other inhibitory factors by cultured murine iris and ciliary body cells.

Aqueous humor contains transforming growth factor-beta (TGF-beta) and other inhibitory factors for cellular proliferation. In the present study we investigated the possibility that these factors are produced locally by cells found within the iris and ciliary body. Iris and ciliary body (I/CB) cells or whole tissue explants from C57BL/6 mice produced soluble factors which inhibited both murine thymocyte and mink lung epithelial cell proliferation. Indomethacin partially blocked inhibition of thymocyte proliferation, but did not affect inhibition of Mv1 Lu proliferation. The inhibitory activity of culture supernatants was not blocked by neutralizing antibodies to TGF-beta 1 or TGF-beta 2. However, following acid activation of culture supernatants from both I/CB and corneal tissue, increased inhibitory activity consistent with activation of latent TGB-beta was detected. Antibody neutralization experiments demonstrated that this increase in activity was due primarily to TGF-beta 2 for I/CB tissue. Polymerase chain reaction (PCR) analysis of cDNA generated from I/CB tissue mRNA showed prominent fragments representing both TGF-beta 1 and TGF-beta 2 mRNA. Corneal tissue, however, showed a prominent fragment for TGF-beta 1 mRNA, but either no band or a barely detectable fragment for TGF-beta 2 mRNA. Therefore, it remains uncertain whether TGF-beta 2 mRNA is produced by the cornea in this strain. Overall, these results demonstrated that three distinct categories of substances inhibitory to proliferation may be locally produced by resident iris and ciliary body cells: 1) indomethacin sensitive products, 2) TGF-beta 2 in latent form, and 3) factors not blocked by indomethacin or anti-TGF-beta neutralizing antibodies. Products generated by these tissues may have important regulatory properties in the development of immune responses to antigens introduced into the anterior chamber.