To investigate the expression pattern of KLF5 in normal and pulmonary hypertensive lungs, we examined KLF5 expression levels in 1) lung biopsies from 10 individuals with non-familial PAH compared to biopsies from 8 individuals without pulmonary hypertension, 2) lungs from 5 rats with monocrotaline-induced pulmonary hypertension compared to 10 control littermates (Figure 1A). This evidence concerns the gene KLF5 and pulmonary arterial hypertension.