Researchers led by Professor Ido Amit of Israel’s Weizmann Institute, have discovered that the kidney is the source of the hormone EPO (erythropoietin), which turns cells in the bone marrow into oxygen-carrying red blood cells. Increasing EPO in kidney disease patients could prevent anemia.

https://nocamels.com/2023/05/breakthrough-discovery-on-the-origin-of-red-blood-cells/