Comparative studies on the platelet-derived growth factor-A and -B gene expression in human monocytes

1. Platelet-derived growth factor (PDGF)-A and -B gene expression was studied in human monocytes. 2. Resting monocytes constitutively transcribed both PDGF-A and -B genes. When monocytes were stimulated by lipopolysaccharide (LPS), transcription rates of both genes were increased in a similar fashion. 3. Consistent with the transcription rates, resting monocytes constitutively expressed both PDGF-A and -B mRNAs. After LPS stimulation, the PDGF-A mRNA level increased gradually, while the PDGF-B mRNA level increased markedly and then decreased rapidly. 4. Reverse transcription-polymerase chain reaction showed that resting monocytes expressed only short PDGF-A mRNA species (representing exons I-V + VII), but LPS-stimulated monocytes expressed long PDGF-A mRNA species (representing exons I-VII) as well. Both resting and LPS-stimulated monocytes expressed only one PDGF-B mRNA species (representing exons I-VII). 5. Together these observations indicate that expression of PDGF-A and -B genes is differentially regulated at the levels of mRNA splicing and mRNA accumulation in monocytes, while transcription of both genes seems to be similarly controlled.