Constitutive expression of cyclooxygenase-2 (COX-2) in developing brain. A. Choroid plexus in human fetuses.

It is believed that prostanoids produced by COX-1 activity are essential for the physiological functions of tissues while those produced by COX-2 lead to various pathological changes in these tissues. Brain is an exceptional organ where in some neurons COX-2 mRNA and its protein are constitutively expressed. Since some prostaglandins may play an important role in the control of blood-brain barrier and cerebral blood flow the purpose of the present study was to examine the COX-2 expression in choroid plexus, which participate in the nutrition of brain parenchyma of human fetuses. Study was performed on 25 brains of human fetuses from 12 to 38 weeks of gestation. In light and electron microscopy characteristic developmental transformation of choroid morphology was observed. In young fetuses from 12 to 20 week of gestation epithelial cells of choroid plexus are cuboidal, contain large amount of glycogen storage and their nuclei are COX-2 immunopositive. From 25 week of gestation until term the amount of glycogen in the choroid plexus diminishes, some apical nuclei are shifted toward central parts of the cells and number of cytoplasm organelles increases. In these cells expression of COX-2 protein is located in cytoplasm but epithelial nuclei are immunonegative. Our results provided evidence that COX-2 is constitutively expressed in the developing human choroid plexus. Different localization of COX-2 in choroid epithelial cells suggests that this enzyme may play a different role in various periods of the choroid plexus development.