TRANSFORMING GROWTH-FACTOR-BETA-1 AND GROWTH-FACTOR-BETA-2 POSITIVELYREGULATE TGF-BETA-1 MESSENGER-RNA EXPRESSION IN TRABECULAR CELLS

Purpose. To determine whether transforming growth factor (TGF)-beta 1 and -beta 2 and basic fibroblast growth factor (bFGF) induce the gene expression of TGF-beta 1 in the first-passage trabecular meshwork cell s of the eye. Methods, Trabecular meshwork cells were cultured from fr esh porcine eyes and treated with 1 ng/ml of TGF-beta 1, TGF-beta 2, o r bFGF for I hour. Cells maintained in serum-free medium were used as controls. Total cellular RNA was extracted, and the first-strand cDNA was synthesized. Multiplex polymerase chain reaction (PCR) and competi tive PCR were performed on aliquots of the cDNAs by using either endog enous (glyceraldehyde-3-phosphate dehydrogenase [G3PDH]) or exogenous sequence (PCR mimic for TGF-beta 1) as internal standards, respectivel y. The obtained products were quantitated by laser densitometry, and s tatistical analysis was performed. Results. The findings show that tra becular cells in vitro express the TGF-beta I messenger RNA constituti vely. Both the techniques of multiplex PCR and competitive PCR demonst rated that the addition of either TGF-beta 1 or TGF-beta 2 at a concen tration present in normal aqueous humor increased the mRNA levels of T GF-beta 1 by 2.82- to 3.07-fold over the controls, and these results w ere statistically significant (P < 0.01). Basic fibroblast growth fact or did not have an effect on TGF-beta 1 expression (P > 0.05). Conclus ions, Transforming growth factor-pi activates its own gene expression in trabecular cells. Considering the multifunctional property of this cytokine, which includes increased deposition of extracellular matrix material and growth inhibition of trabecular cells, a change in its co ncentration within the eye would have a profound effect because of thi s autoinductive activity.