This study investigates the effects of repetitive hypoxic preconditioning (RHP) on neuronal resilience during ischemic stroke. Mice exposed to fluctuating low oxygen levels show improved adaptation and reduced brain damage when subjected to subsequent ischemic conditions.
Place a mouse in a sealed induction chamber connected to an inlet for controlled oxygen delivery.
Expose it to cycles of fluctuating low oxygen levels, called repetitive hypoxic preconditioning, or RHP.
With each cycle of reduced oxygen, the mouse’s blood oxygen levels drop, creating a hypoxic state.
Some neurons in the brain gradually adapt, adjusting their metabolism to survive in a low-oxygen environment.
The blood-brain barrier, which protects the brain, remains stable and prevents brain inflammation.
Remove the mouse from the chamber and allow recovery. Then, induce an ischemic stroke by blocking the middle cerebral artery.
This prevents oxygen-rich blood from reaching the brain, placing neurons under extreme stress.
The blood-brain barrier is disrupted, triggering inflammation.
However, RHP-trained neurons are better adapted to low-oxygen conditions, making them more damage-resistant and preserving their function.
This suggests that RHP helps neurons adapt and reduces brain damage caused by ischemic stroke and oxygen deprivation.
To begin, divide mice into two groups, the RHP group, which receives exposures of 8% and 11% oxygen, and the control group, which receives exposures of 21% oxygen concurrently. Remove the top filter lid of each cage, and place the cage with food and water bottles intact into the chambers connected to their respective oxygen tanks. Close and secure the lid of the chamber.
Open the main gas valve for the tanks, and set the initial flow for each induction chamber to 2 liters per minute, or LPM. After five minutes of exposure, reduce the flow rate to 1 LPM for the remainder of the exposure. At the end of the exposure, reduce the flow to zero LPM, and close the gas valve for the tanks.
Open the chamber lids and replace the filter top lid on each cage. Place the cages in standard housing until the next hypoxic exposure. Spray down each induction chamber with a disinfectant and deodorizer after each use.
Expose both RHP and control mice at the same time of day over the course of the two weeks of the protocol. Then perform a transient middle cerebral artery occlusion, or a TMCAO, as described in the text.
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