Choroid plexus in the central nervous system: Biology and physiopathology

Choroid plexuses (CPs) are localized in the ventricular system of the brain and form one of the interfaces between the blood and the central nervous s ystem (CNS). They are composed of a tight epithelium responsible for cerebr ospinal fluid secretion, which encloses a loose connective core containing permeable capillaries and cells of the lymphoid lineage. In accordance with its peculiar localization between 2 circulating fluid compartments, the CP epithelium is involved in numerous exchange processes that either supply t he brain with nutrients and hormones, or clear deleterious compounds and me tabolites from the brain. Choroid plexuses also participate in neurohumoral brain modulation and neuroimmune interactions, thereby contributing greatl y in maintaining brain homeostasis. Besides these physiological functions, the implication of choroid plexuses in pathological processes is increasing ly documented. In this review, we focus on some of the novel aspects of CP functions in relation to brain development, transfer of neuro-humoral infor mation, brain/immune system interactions, brain aging, and cerebral pharmac o-toxicology.