To dissect the role of progesterone on BBB integrity using our in-vivo CCMs mutant mice model.

Cerebral cavernous malformations (CCM) result in increased susceptibility to hemorrhagic strokes. CCM1, CCM2, and CCM3 form the CCM signaling complex (CSC), which regulates numerous signaling cascades including Blood-Brain Barrier (BBB) integrity. Progesterone can bind to either its nuclear receptors (PR1/2) or membrane progesterone receptors (mPRs) and has been linked to hemorrhagic CCMs.

CCM (1,2,3) mutants and wild type (WT) mice were injected with progesterone and mifepristone (100mg/kg body weight) 5 days a week for 30, 60, and 90 days, respectively. Mice were also injected with carrier oil only or left untreated for vehicle and naïve controls, respectively. Evans Blue dye (EBD)was then used to quantitatively measure the permeability of blood vessels in the brain, liver, and lungs.

Increased permeability of blood vessels in the lung and liver was observed in CCM2 mutant mice as early as 30-days compared to WT. We also observed increased permeability in the lungs and liver in our 60-days treatment group with CCM3 mutant mice. Similarly, significantly increased permeability of the BBB was observed in all CCMs (1, 2, 3) mutant mice in 90-days treatment groups compared to WT. Similar intensity of EBD signals was observed among control groups, indicating no apparent influence of vehicle injection on the permeability of blood vessels in these three organs.

We demonstrate that a novel signaling network among the CSC and mPRs is dynamically modulated with intricate feedback regulations. The depletion of any of the three CCM genes results in the disruption of non-classic mPRs-mediated signaling as well as defective homeostasis of PRG in-vivo. Deficiency of any of the three CCM genes in combination with long exposure to excessive Progesterone significantly increases disruption of the BBB.