EPO and pulmonary arterial hypertension: In this review, we examine the molecular mechanisms underlying the hypoxia-pulmonary hypertension axis, focusing on the complex and interconnected signaling networks involving redox imbalance, PI3K–Akt signaling, Na+/H+ exchange, nitric oxide bioavailability, autophagy, mitochondrial dynamics and mitophagy, metabolic reprogramming, inflammation, adventitial remodeling with particular emphasis on pulmonary arterial adventitial fibroblasts, and erythropoietin signaling.