The yak (Bos grunniens), a unique bovine species that is endemic to the Qinghai–Tibet Plateau and adjacent mountainous regions, exhibits remarkable adaptations to chronic high-altitude hypoxia. However, the molecular mechanisms underlying yaks’ adaptation to this extreme environment remain poorly understood. This study aimed to elucidate the spatiotemporal expression dynamics of hypoxia-inducible factor 1α (HIF-1α) and 2α (HIF-2α) in major tissues of yaks across developmental stages (0.5, 1.5, 2.5, and 4.5 years; n = 3 per group). The tissues (heart, liver, spleen, lungs, kidneys, blood vessels and skeletal muscles) were analyzed using hematoxylin and eosin (H HIF-2α: r = 0.493). In pulmonary tissues, HIF-1α in bronchial smooth muscle peaked at 2.5 years, whereas alveolar septal HIF-2α peaked at 1.5 years (p < 0.05). In the kidney, HIF-1α was primarily localized to tubular epithelial cells and HIF-2α was diffusely distributed in the glomerular interstitium; neither factor showed significant variation across ages. In vascular tissues, HIF-1α expression remained stable across all ages and was predominantly observed in the smooth muscle layer, while HIF-2α exhibited a significant peak in endothelial cells at 2.5 years (p < 0.01). These findings suggest that HIF-1α predominates during early development stages, while HIF-2α becomes dominant as yaks approach maturity.
Wu et al. (Wed,) studied this question.