Human umbilical cord and fetal membranes co-express leptin and its receptor genes.

Leptin, protein product of the ob gene, not only regulates food intake and energy expenditure but also has a number of other actions in the body. Leptin actions are mediated by its receptors that have either a long or a truncated intracellular domain, which is coupled to signal transduction pathways. Previous studies have demonstrated that human placenta expresses both leptin and its receptors. However, it is not known whether human umbilical cord and fetal membranes are also sites of expression of these molecules. Therefore, the present study investigated leptin and its receptor expression in these tissues from term pregnancy. Reverse-transcription polymerase chain reaction (RT-PCR) amplified expected size fragments of leptin and also its short and long receptor isoforms from umbilical cord and fetal membranes. The authenticity of PCR-amplified fragments was confirmed by Southern blot hybridization with corresponding cDNA probes. Western blotting revealed that the transcripts were translated into 16-kDa leptin, and 125-kDa (long) and 100-kDa (short) leptin receptor isoforms. However, the long form is present in umbilical cord and the short form in the fetal membranes. Immunocytochemistry revealed that leptin and its receptor isoforms were present in endothelial cells and smooth muscle of umbilical veins and artery, myofibroblasts in Wharton's jelly, amnion covering the cord, amnion and chorion in reflected fetal membranes and decidua from membranes. Amnion, however, contained the highest levels of leptin and its receptor immunostaining. In summary, term pregnancy human umbilical cord and fetal membranes co-express leptin and its receptor genes, which supports the hypothesis that leptin is an autocrine and paracrine regulator in these tissues.