How Placenta Promotes the Successful Reproduction in High-Altitude Populations: A Transcriptome Comparison between Adaptation and Acclimatization.

As the best adapted high altitude population, Tibetans feature a relatively high offspring survival rate. Genome-wide studies have identified hundreds of candidate SNPs related to high altitude adaptation of Tibetans, although most of them have unknown functional relevance. To explore the mechanisms behind successful reproduction at high altitudes, we compared the placental transcriptomes of Tibetans, sea level Hans (SLHan), and Han immigrants (ImHan). Among the three populations, placentas from ImHan showed a hyperactive gene expression pattern. Their increased activation demonstrates a hypoxic stress response similar to sea level individuals experiencing hypoxic conditions. Unlike ImHan, Tibetan placentas were characterized by the significant up-regulation of placenta-specific genes, and the activation of autophagy and the tricarboxylic acid (TCA) cycle. Certain conserved hypoxia response functions, including the antioxidant system and angiogenesis, were activated in both ImHan and Tibetans, but mediated by different genes. The coherence of specific transcriptome features linked to possible genetic contribution was observed in Tibetans. Furthermore, we identified a novel Tibetan-specific EPAS1 isoform with a partial deletion at exon six, which may be involved in the adaption to hypoxia through the EPAS1-centred gene network in the placenta. Overall, our results show that the placenta grants successful pregnancies in Tibetans by strengthening the natural functions of the placenta itself. On the other hand, the placenta of ImHan was in an inhabiting time-dependent acclimatization process representing a common hypoxic stress response pattern.

Natural selection on EPAS1 (HIF2alpha) associated with low hemoglobin concentration in Tibetan highlanders.

By impairing both function and survival, the severe reduction in oxygen availability associated with high-altitude environments is likely to act as an agent of natural selection. We used genomic and candidate gene approaches to search for evidence of such genetic selection. First, a genome-wide allelic differentiation scan (GWADS) comparing indigenous highlanders of the Tibetan Plateau (3,200-3,500 m) with closely related lowland Han revealed a genome-wide significant divergence across eight SNPs located near EPAS1. This gene encodes the transcription factor HIF2alpha, which stimulates production of red blood cells and thus increases the concentration of hemoglobin in blood. Second, in a separate cohort of Tibetans residing at 4,200 m, we identified 31 EPAS1 SNPs in high linkage disequilibrium that correlated significantly with hemoglobin concentration. The sex-adjusted hemoglobin concentration was, on average, 0.8 g/dL lower in the major allele homozygotes compared with the heterozygotes. These findings were replicated in a third cohort of Tibetans residing at 4,300 m. The alleles associating with lower hemoglobin concentrations were correlated with the signal from the GWADS study and were observed at greatly elevated frequencies in the Tibetan cohorts compared with the Han. High hemoglobin concentrations are a cardinal feature of chronic mountain sickness offering one plausible mechanism for selection. Alternatively, as EPAS1 is pleiotropic in its effects, selection may have operated on some other aspect of the phenotype. Whichever of these explanations is correct, the evidence for genetic selection at the EPAS1 locus from the GWADS study is supported by the replicated studies associating function with the allelic variants.

[Clinical effect of Kirschner wire intramedullary fixation in the treatment of pediatric both-bone forearm fractures at high altitude area].

OBJECTIVE: To explore the clinical effect of Kirschner wire intramedullary fixation in the treatment of both-bone forearm fractures in children of high altitude area. METHODS: From August 2020 to December 2021, 19 children were treated with Kirschner wire intramedullary fixation including 11 males and 8 females, aged from 4 to 13 years old with an average of (8.16±2.71) years old. The course of disease was 1 to 10 days, with a mean of (4.11±2.51) d. First, close reduction was performed. If the reduction was unsuccessful, limited open reduction was performed, followed by Kirschner wire intramedullary fixation of the radius and ulna. The fracture healing was evaluated by X-ray after operation, and the curative effect was evaluated by Anderson forearm function score standard. RESULTS: The wound healed well after operation, 2 cases had clinical manifestations of needle tail irritation after operation, and the symptoms disappeared after removing the internal fixation. The average follow-up time was(7.68±3.50) months (3 to 14 months). X-ray showed that all fracture healing in follow-up, Anderson forearm function score showed excellent in 16 cases, good in 2 cases and fair in 1 case at the final follow-up. CONCLUSION: Children with fractures in plateau areas often have delayed medical treatment, lack of medical conditions and insufficient compliance. Based on these characteristics, Kirschner wire intramedullary fixation for the treatment of children's double forearm fractures has the advantages of small injury and rapid recovery. It is a kind of operation method that can be popularized.