The expression of TGF-beta 1, TGF-beta 2 and TGF-beta 3 precursors mRNA transcripts in in vivo human corneal cells were studied. Complementary DNA (cDNA) was generated from poly A+RNA extracted from in vivo human corneal epithelial cells, stromal keratocytes and endothelial cells. With the cDNAs as template, polymerase chain reaction (PCR) was carried out using specific primers of TGF-beta 1, TGF-beta 2 and TGF-beta 3 precursors, synthesized by choosing specific nucleotide sequences in the latency-associated peptide region of each precursor. Southern blot analysis of the PCR products was carried out. In corneal epithelial cells, TGF-beta 2 mRNA transcript was strongly expressed; TGF-beta 1 and -beta 3 mRNA transcripts were also expressed; stromal keratocyte samples expressed TGF-beta 1 and -beta 2 mRNA transcripts but not TGF-beta 3 mRNA transcript. Endothelial cells expressed all three transcripts. The present study, together with the authors' previous immunohistochemical study demonstrates that both protein and mRNA of TGF-beta 2-LAP are present in human corneal epithelium, indicating that TGF-beta 2 may play a crucial role in corneal epithelial cell layers.