Summary
In a recent study, we purified and cloned a newly identified bioactive factor that
stimulates prostacyclin (PGI2) production by vascular endothelial cells (ECs) using conditioned medium (CM) from
cultured human diploid fibroblast cells. The present study was undertaken to clarify
whether PSF is expressed in ECs and vascular smooth muscle cells (SMCs) of human tissues
at a protein level. In an immunohistochemical study of seven human autopsy cases,
all arteries in all lungs (n = 4) and kidneys (n = 6) examined stained positive to
variable extents for PGI2-stimulating factor (PSF). PSF was predominantly expressed by SMCs in the media of
small arteries. Staining for PSF was weaker in SMCs of aortic media (n = 3) and strong
in SMCs of vaso vasorum (n = 3). PSF staining was also found in the SMCs of human
bronchi (n = 4). Immunoblot analysis confirmed that PSF is present in CM from cultured
bovine aortic SMCs.