Immunolocalization of substance P and NK-1 receptor in Hofbauer cells in human normal placenta

Substance P (SP) after binding to the neurokinin-1 (NK-1) receptor regulates many biological functions. Both SP and the NK-1 receptor are expressed in human normal placenta cells, monocytes, and macrophages. However, to our knowledge, the presence of both SP and the NK-1 receptor in macrophages of the placenta, the Hofbauer cells, is unknown. We demonstrate by immunohistochemistry in human normal placenta samples the presence of both SP and NK-1 receptors in the cytoplasm and in the nucleus of Hofbauer cells. The findings suggest a functional role of the SP/NK-1 receptor system in the physiology and pathophysiology of Hofbauer cells in the human placenta.