The influence of the choroid plexus on brain function: beyond its role in cerebrospinal fluid production.

The choroid plexus (ChP) is a highly vascularized tissue located within the brain ventricles. Traditionally recognized for its primary role in cerebrospinal fluid (CSF) production, recent research has unveiled a far more complex and dynamic picture of the ChP's contributions to brain health and homeostasis. The ChP is composed of tight-junction-bound epithelial cells and the underlying stroma-rich fenestrated capillaries of blood vessels. This unique architecture creates a barrier between the peripheral blood and CSF, regulating the brain's internal environment. The discovery that CSF enters the brain parenchyma via the perivascular space, coupled with the identification of a functional brain lymphatic system linked to CSF turnover, further highlights the ChP as a gatekeeper of waste clearance and fluid homeostasis. This review will cover the development and histology of ChP, focusing on the dynamic response of the blood-CSF barrier in the context of systemic inflammation, a process whose molecular mechanisms have recently been elucidated.