Differential expression of HIF-1α and its hypoxia-related inducers in the spleens of plateau yaks and plain yellow cattle.

The present study aims to investigate the distribution and expression characteristics of HIF-1α, VEGF, VEGFR-2, VCAM-1, and IL-4 in the spleen of plateau yaks and plain yellow cattle and to speculate the possible regulatory role of HIF-1α and its related hypoxia-inducible factors in the adaptation of the yak spleen to the plateau hypoxic environment. Histological features were observed using H&E and PAS stains. Immunohistochemical staining and optical density analysis were applied to investigate the distribution and differences in the expression of HIF-1α, VEGF, VEGFR-2, VCAM-1, and IL-4 in the spleen of yaks and cattle. The results showed that the area of splenic trabeculae and splenic nodules was significantly larger in the yak than in yellow cattle (P<0.05). Glycogen was mainly distributed in splenic arterial endothelial cells, vascular smooth muscle cells, splenic blood sinusoidal endothelial cells, and fibroblasts, and the distribution was significantly higher in the spleen of yaks than in cattle (P<0.05). HIF-1α, VEGF, VEGFR-2, VCAM-1, and IL-4 were mainly expressed in lymphocytes, arterial endothelial cells, vascular smooth muscle cells, splenic blood sinusoidal endothelial cells, and fibroblast cytoplasm, with higher expression in yak spleen (P<0.05). In conclusion, combining the differences in spleen tissue structure, glycogen distribution, and expression distribution of several hypoxia-related factors between yaks and cattle, we suggest that HIF-1α, VEGF, VEGFR-2, VCAM-1, and IL-4 may be important factors in the adaptation of yak spleen to the plateau environment, which provides a theoretical basis for further exploring the adaptation mechanism of plateau hypoxia in yaks.