Choroidal readaptation to gravity in rats after spaceflight and head-down tilt

Area of Science:

• Space biology
• Gravitational biology
• Physiology

Background:

• Spaceflight and altered gravity (orthostatic position) impact physiological systems.
• The choroid plexus, crucial for cerebrospinal fluid production and brain homeostasis, is susceptible to microgravity effects.

Purpose of the Study:

• To investigate the timeline of choroidal structure and function recovery after spaceflight and head-down tilt (HDT).
• To assess the restoration of protein distribution in the choroid plexus post-exposure to altered gravity.

Main Methods:

• Rat choroid plexus tissues were analyzed 6 hours and 2 days after spaceflight (SLS-2 and NIH-R1 experiments).
• Tissues were also analyzed 6 hours after head-down tilt (HDT) experiments.
• Fine structure and protein distribution (ezrin, carbonic anhydrase II) were examined.

Main Results:

• Apical alterations in choroidal cells confirmed impairment by weightlessness and HDT.
• Rapid initial recovery of apical organization (microvilli, kinocilia) was observed within 6 hours post-landing.
• Enlarged microvilli after 2 days suggested increased activity, but protein distributions remained altered.

Conclusions:

• Choroidal structures and functions are impaired by weightlessness.
• Apical organization shows rapid but incomplete recovery after return to Earth gravity.
• Full restoration of choroidal structures and functions, including specific protein distributions, is not achieved within 2 days of readaptation.