Changes of iron dynamics in the duodenum and bone marrow under partial gravity condition in mice

With the advancement of the space age, research on physiological changes during long-term space missions has become increasingly important. Spaceflight-induced anemia, along with muscle and bone loss, is a significant concern for astronaut health, potentially disrupting iron metabolism and absorption. However, the mechanisms underlying intestinal iron absorption in space remain unclear.

This study investigated iron dynamics in the duodenum and bone marrow of mice exposed to partial gravity (PG) to assess potential alterations in iron absorption and storage.

Using samples provided by the Japan Aerospace Exploration Agency (Kibo mouse sample share), we analyzed duodenal and bone marrow tissues from mice reared in PG (1/6G) and compared them to those of mice reared in ground gravity (control gravity (CG): 1G). We conducted Perls staining to visualize iron distribution, measured iron concentrations, and analyzed iron regulatory proteins (ferritin heavy chain, divalent metal transporter 1, and ferroportin) using qRT-PCR, immunohistochemistry, and western blotting.

Iron staining, concentration, and ferritin heavy chain expression in the duodenum were reduced in the PG group compared with those in the CG group. The expression of iron transporters (divalent metal protein 1 and ferroportin) was also attenuated. Furthermore, the PG group showed fewer macrophages and more goblet cells in duodenal villi. Stainability of iron and ferritin heavy chain expression in the sternal bone marrow similarly decreased in the PG group.

These findings indicate reduced iron retention in the duodenum under partial gravity, suggesting that the space environment may impair iron absorption.