Erythropoietin can be produced by :

Erythropoietin is a glycoprotein hormone, produced by the kidney, which increases erythropoietic activity. The production of erythropoietin is increased in response to reduced oxygen tension in the blood reaching the kidney. It results in an increase in the number of cells committed to the erythroid line, reduced maturation time and early release of erythrocytes from the bone marrow. Erythropoietin mediates the physiological response of the bone marrow to anemia or hypoxia.