HIF signaling transduction via changes in erythropoietin or VEGF can lead to adjustments of the oxygen-carrying capacity of the blood (e.g., increased erythropoiesis) and enhanced vascularization [132]; for example, development of high-altitude polycythemia (HAPC) in the gastric mucosa is characterized by increased capillary density/erythropoiesis as well as elevations in ROS generation, HIF-1α, apoptosis, and mitochondrial vacuole density [133]. Here, HIF1A is linked to polycythemia.