Objective: High altitude is characterized by low oxygen pressure, resulting in multiple adaptive responses. Tibetans who have lived in the plateau for thousands of years have developed unique phenotypes, such as downregulation of the HIF pathway through EPAS1 and EGLN1 gene mutation. However, the changes of hemoglobin–oxygen affinity under hypoxia environment remain elusive. Methods: A blood cell analyzer and a blood oxygen analyzer were used to conduct routine blood tests and measure the oxygen affinity P₅₀ in in the Han population that rapidly entered the plateau (for 3–7 days), the plateau-acclimatized Han population (residing for 30 days on the plateau), the plateau Han population (more than 10 years on the plateau), and the Tibetan population. Results: The Han population that rapidly entered the plateau had increasing higher P₅₀ values, RBCs counts and hemoglobin (HGB) levels, while the acclimatized Han population, the plateau Han population and Tibetan all had significantly lower P₅₀ values. However, there were no significant differences in the RBCs counts and HGB levels between the plateau Han, Tibetan populations and the Han population of the plains. Discussion: The adaptability of the Tibetan and plateau Han populations to the plateau was mainly due to the strong affinity of HGB for oxygen, which provided sufficient oxygen for tissues and organs. Conclusions: The change of P₅₀ could be a feature of the adaptation to the plateau and to avoid altitude sickness, such as high-altitude polycythemia and dyspnea.

In the Chinese Han population, prolonged exposure to hypoxic conditions can promote compensatory erythropoiesis which improves hypoxemia. However, Tibetans have developed unique phenotypes, such as downregulation of the hypoxia-inducible factor pathway through EPAS1 gene mutation, thus the mechanism of adaption of the Han population should be further studied. The results indicated that, under plateau hypoxic conditions, the plains population was able to acclimate rapidly to hypoxia through increasing EPAS1 mRNA expression and changing the hemoglobin conformation. Furthermore, the mutant genotype frequencies of the rs13419896, rs1868092 and rs4953354 loci in the EPAS1 gene were significantly higher in the Tibetan population than in the plains population. The EPAS1 gene expression level was lowest in the Han population carrying the A-A homozygous mutant of the rs13419896 locus but that it increased rapidly after these individuals entered the plateau. At this time, the hemoglobin content was lower in the homozygous mutant Han group than in the wild-type and heterozygous mutant populations, and the viscosity of blood was reduced in populations carrying the A-A haplotypes in rs13419896 and rs1868092 Among Tibetans, the group carrying homozygous mutations of the three SNPs also had lower hemoglobin concentrations than the wild-type. The Raman spectroscopy results showed that exposure of the Tibetan and Han population to hypoxic conditions changed the spatial conformation of hemoglobin and its binding ability to oxygen. The Tibetan population has mainly adapted to the plateau through genetic mutations, whereas some individuals adapt through changes in hemoglobin structure and function.

In vitro generation of red blood cells has the potential to circumvent shortfalls in the global demand for blood for transfusion applications. However, cell differentiation and proliferation are often regulated by precise changes in gene expression, but the underlying mechanisms and molecular changes remain unclear. Quantitative reverse transcription–polymerase chain reaction (qRT-PCR) can be used to evaluate multiple target genes. To make the results more reliable, suitable reference genes should be used to calibrate the error associated with qRT-PCR. In this study, we utilized bioinformatics to screen 3 novel candidate reference genes (calcium and integrin binding family member 2 [CIB2], olfactory receptor family 8 subfamily B member 8 [OR8B8], and zinc finger protein 425 [ZNF425]) along with eight traditional reference genes (glyceraldehyde-3-phosphate dehydrogenase [GAPDH], β-actin [ACTB], 18S RNA, β2-microglobulin [β2-MG], peptidylprolyl isomerase A [PPIA], TATA box-binding protein [TBP], hydroxymethylbilane synthase [HMBS], and hypoxanthine phosphoribosyltransferase 1 [HPRT1]). Two software algorithms (geNorm and NormFinder) were used to evaluate the stability of expression of the 11 genes at different stages of erythrocyte development. Comprehensive analysis showed that expression of GAPDH and TBP was the most stable, whereas ZNF425 and OR8B8 were the least suitable candidate genes. These results suggest that appropriate reference genes should be selected before performing gene expression analysis during erythroid differentiation and that GAPDH and TBP are suitable reference genes for gene expression studies on erythropoiesis.

The Qing-Tibet Plateau is characterized by low oxygen pressure, which is an important biomedical and ecological stressor. However, the variation in gene expression during periods of stay on the plateau has not been well studied. We recruited eight volunteers to stay on the plateau for 3, 7, and 30 days. Human Clariom D arrays were used to measure transcriptome changes in the mRNA expression profiles in these volunteers' blood. Analysis of variance (ANOVA) indicated that 699 genes were significantly differentially expressed in response to entering the plateau during hypoxic exposure. The genes with changes in transcript abundance were involved in the terms phosphoprotein, acetylation, protein binding, and protein transport. Furthermore, numerous genes involved in hematopoietic functions, including erythropoiesis and immunoregulation, were differentially expressed in response to hypoxia. This phenomenon may be one of reasons why the majority of people entering the plateau do not have excessive erythrocyte proliferation and are susceptible to infection.