Main Focus: Study of blood-brain interfaces in contributing to the delivery of blood-borne molecules to their neuronal targets
The blood-brain interfaces are the structures through which the peripheral organs and the central nervous system communicate to regulate body homeostasis. Our works focus on the role of circumventricular organs (CVOs) in contributing to the delivery of blood-borne molecules to their neuronal targets.
We have shown that tanycytes and fenestrated vessels, the two main features of CVOs, form a blood-brain interface that regulates the diffusion of blood-borne molecules into the cerebrospinal fluid and the rest of the brain while allowing their free diffusion into the parenchyma of the CVOs (Figure) (Mullier et al., 2010, Langlet et al., 2013a).
Moreover this “brain window” can be extended to CVO surrounding parenchyma as shown for the hypothalamic arcuate nucleus (ARC) that adjoins the median eminence (ME) (Langlet et al., 2013b). After fasting for 24h, a number of the blood-brain-barrier capillaries of the arcuate nucleus became fenestrated, resulting in the barrier properties becoming delocalized to the tanycytes they are in contact with. We showed that fasting-induced increased capillary permeability enhanced the penetration and action of circulating metabolic signals on ARH neurons.
These results highlight a new concept in the way the energy balance can be regulated: via the plasticity of the circumventricular organ interfaces. They emphasize the role of the CVOs in contributing to the delivery of blood-borne molecules conveying metabolic information to the sensory neurons whilst ensuring brain homeostasis.