Chunhua Jiang

Hypobaric hypoxia causes deleterious effects on spermatogenesis in rats

The study was conducted to explore the effects of hypobaric hypoxia on spermatogenesis in rats. Adult male Wistar rats were randomly divided into four groups: three hypoxia-exposed groups and one normoxic control group. Rats in the normoxic control group were raised at an altitude of 300 m, while rats in the 5-, 15-, and 30-day hypoxic groups were raised in a hypobaric chamber simulating a high altitude of 5000 m for 5, 15, and 30 days respectively. Flow cytometry was used to detect the DNA content of testicular spermatogenic cells in rats. The apoptosis of germ cells in testis was analyzed by using TUNEL assay. Spermatogenesis was also evaluated by morphology. Flow cytometry analysis revealed that 5-30 days of hypobaric hypoxia exposure significantly reduced the percentage of tetraploid cell population in rat testis. After rats were exposed to hypobaric hypoxia for 30 days, the ratio of haploid and diploid cell populations in testis reduced significantly. Seminiferous tubules with apoptotic germ cell increased after exposure to hypoxia. Most apoptotic germ cells were spermatogonia and spermatocytes. Hypoxia also caused decrease of cellularity of seminiferous epithelium, degeneration and sloughing of seminiferous epithelial cells occasionally. The data suggest that hypobaric hypoxia inhibits the spermatogenesis in rats. Decrease of tetraploid spermatogenic cells (primary spermatocytes) induced by hypoxia is an important approach to suppress spermatogenesis. The apoptosis of primary spermatocytes and spermatogonia may contribute to the loss of tetraploid cell populations.

Regulation of bone marrow hematopoietic stem cell is involved in high-altitude erythrocytosis

OBJECTIVE Hypoxia at high altitudes can lead to increased production of red blood cells through the hormone erythropoietin (EPO). In this study, we observed how the EPO-unresponsive hematopoietic stem cell (HSC) compartment responds to high-altitude hypoxic environments and contributes to erythropoiesis. MATERIALS AND METHODS Using a mouse model at simulated high altitude, the bone marrow (BM) and spleen lineage marker(-)Sca-1(+)c-Kit(+) (LSK) HSC compartment were observed in detail. Normal LSK cells were then cultured under different conditions (varying EPO levels, oxygen concentrations, and BM supernatants) to investigate the causes of the HSC responses. RESULTS Hypoxic mice exhibited a marked expansion in BM and spleen LSK compartments, which were associated with enhanced proliferation. BM HSCs seemed to play a more important role in erythropoiesis at high altitude than spleen HSCs. There was also a lineage fate change of BM HSCs in hypoxic mice that was manifested in increased megakaryocyte-erythrocyte progenitors and periodically reduced granulocyte-macrophage progenitors in the BM. The LSK cells in hypoxic mice displayed upregulated erythroid-specific GATA-1 and downregulated granulocyte-macrophage-specific PU.1 messenger RNA expression, as well as the capacity to differentiate into more erythroid precursors after culture. BM culture supernatant from hypoxic mice (but not elevated EPO or varying O(2) tension) could induce expansion and erythroid-priority differentiation of the HSC population, a phenomenon partially caused by increasing interleukin-3 and interleukin-6 secretion in the BM. CONCLUSIONS The present study suggests a new EPO-independent HSC mechanism of high-altitude erythrocytosis.

Gene expression profiling of high altitude polycythemia in Han Chinese migrating to the Qinghai-Tibetan plateau

Chronic mountain sickness (CMS) is a condition in which the hematocrit is increased above the normal level in residents at high altitude. High altitude polycythemia (HAPC) is the most characteristic sign of CMS. However, the pathogenesis of HAPC is poorly understood. The present study aimed to investigate the gene expression profile of HAPC in Han Chinese migrating to the Qinghai-Tibetan Plateau and to identify the pathogenetic mechanisms. A total of 9 differentially expressed genes were identified in HAPC patients using microarrays: 5 were up-regulated and 4 were down-regulated. Functional analysis of the array data revealed that cell division cycle 42 (CDC42) and the human immune response may be key features underlying the mechanism and development of HAPC.

Mitochondrial genome sequence of the Tibetan wild ass (Equus kiang)

The Tibetan wild ass, or kiang (Equus kiang) is endemic to the cold and hypoxic (4000–7000 m above sea level) climates of the montane and alpine grasslands of the Tibetan Plateau. We report here the complete nucleotide sequence of the E. kiang mitochondrial genome. Our results show that E. kiang mitochondrial DNA is 16,634 bp long, and predicted to encode all the 37 genes that are typical for vertebrates.

An EPAS1 Haplotype Is Associated With High Altitude Polycythemia in Male Han Chinese at the Qinghai-Tibetan Plateau

BACKGROUND Hemoglobin concentration at high altitude is considered an important marker of high altitude adaptation, and native Tibetans in the Qinghai-Tibetan plateau show lower hemoglobin concentrations than Han people who have emigrated from plains areas. Genetic studies revealed that EPAS1 plays a key role in high altitude adaptation and is associated with the low hemoglobin concentration in Tibetans. Three single nucleotide polymorphisms (rs13419896, rs4953354, rs1868092) of noncoding regions in EPAS1 exhibited significantly different allele frequencies in the Tibetan and Han populations and were associated with low hemoglobin concentrations in Tibetans. METHODS To explore the hereditary basis of high altitude polycythemia (HAPC) and investigate the association between EPAS1 and HAPC in the Han population, these 3 single nucleotide polymorphisms were assessed in 318 male Han Chinese HAPC patients and 316 control subjects. Genotyping was performed by high resolution melting curve analysis. RESULTS The G-G-G haplotype of rs13419896, rs4953354, and rs1868092 was significantly more frequent in HAPC patients than in control subjects, whereas no differences in the allele or genotype frequencies of the 3 single nucleotide polymorphisms were found between HAPC patients and control subjects. Moreover, genotypes of rs1868092 (AA) and rs4953354 (GG) that were not observed in the Chinese Han in the Beijing population were found at frequencies of 1.6% and 0.9%, respectively, in our study population of HAPC patients and control subjects. CONCLUSIONS Carriers of this EPAS1 haplotype (G-G-G, rs13419896, rs4953354, and rs1868092) may have a higher risk for HAPC. These results may contribute to a better understanding of the pathogenesis of HAPC in the Han population.

Interaction of CARD14, SENP1 and VEGFA polymorphisms on susceptibility to high altitude polycythemia in the Han Chinese population at the Qinghai–Tibetan Plateau

High altitude polycythemia (HAPC) is a serious public health problem among Han Chinese immigrants to the Qinghai-Tibetan Plateau. This study aims to explore the genetic basis of HAPC in the Han Chinese population. 484 male subjects (234 patients and 250 controls) were enrolled in this study. Genotyping was performed for polymorphisms of I/D in ACE, C1772T and G1790A in exon 12 of HIF-1α, rs2567206 in CYP1B1, rs726354 in SENP1, rs3025033 in VEGFA, rs7251432 in HAMP, rs2075800 in HSPA1L and rs8065364 in CARD14. Gene-gene interaction was assessed by multifactor dimensionality reduction. A significant association was seen between CARD14 polymorphism rs8065364 and risk of HAPC development in male Han Chinese, and the C allele of rs8065364 was a risk factor (odds ratio (OR)=1.59, 95% confidence interval (95% CI)=1.21-2.08). Gene-gene interaction analysis indicated that a synergistic relationship existed between rs3025033 and rs8065364 (1.00%), rs3025033 and rs726354 (0.18%), and rs726354 and rs8065364 (0.17%). The combination of rs8065364 in CARD14, rs3025033 in VEGFA and rs726354 in SENP1 was the best model to predict HAPC development in this study (testing accuracy=0.6183, p=0.0010, cross-validated consistency=10/10). Genetic interactions of SNPs in CARD14, SENP1 and VEGFA might represent a functional mechanism in the pathogenesis of HAPC.

Mitochondrial DNA 10609T promotes hypoxia-induced increase of intracellular ROS and is a risk factor of high altitude polycythemia.

Hypobaric hypoxia is the primary cause of high altitude polycythemia (HAPC). Mitochondria are critical organelles that consume high levels of oxygen and generate ATP. We hypothesize that the mitochondrion may be at the center of HAPC, and mitochondrial DNA (mtDNA) SNPs may be involved in its development. First, we conducted a case-control study to investigate the association of mtDNA variants with HAPC in Han Chinese migrating to the Qinghai-Tibetan Plateau. Pearson’s chi-square tests revealed that mtDNA 8414T (MU) frequency (19.5%) in the HAPC group was significantly higher than that of the control (13.0%, P = 0.04, OR = 1.615, 95%CI: 1.020–2.555). The multivariate logistic regression analysis, after adjustment for environmental factors, revealed that mtDNA 10609T (WT) was significantly associated with an increased risk of HAPC (P<0.01, OR = 2.558, 95%CI: 1.250–5.236). Second, to verify the association, in vitro experiments of transmitochondrial cybrids was performed and revealed that the mtDNA 10609 variant promoted hypoxia-induced increase of intracellular ROS, but the mtDNA 8414 variant did not. Our findings provide evidence that, in Han Chinese, mtDNA 10609T promotes hypoxia-induced increase of intracellular ROS and is a HAPC risk factor.

Potential beneficial effects of oral administration of isoflavones in patients with chronic mountain sickness.

Soy isoflavones (Ifs), which are natural phytoestrogens, have beneficial effects in cardiovascular disease. We have previously shown that genistein, the most active component of Ifs, inhibits pulmonary vascular structural remodeling and right ventricular hypertrophy induced by chronic hypoxia in male Wistar rats. This study aimed to evaluate the effects of Ifs on right ventricular and pulmonary hemodynamics in individuals with chronic mountain sickness (CMS). Twenty-eight male patients living on the Qinghai-Tibetan plateau (5,200 m) who were suffering from CMS were treated orally with Ifs (20 mg, twice daily) for 45 days. Physiological and plasma biochemical indices, hematology and echocardiography were investigated. It was observed that 45 days of treatment with Ifs significantly increased blood oxygen saturation and markedly decreased the CMS score and heart rate (all P<0.05) of the subjects. Following treatment with Ifs, hematocrit (P<0.05), hemoglobin concentration (P<0.01) and plasma levels of malondialdehyde (P<0.05) were significantly decreased, while plasma levels of nitric oxide (P<0.01) and the plasma activity of nitric oxide synthase (P<0.01) and superoxide dismutase (P<0.01) were markedly increased compared with the respective values obtained prior to treatment with Ifs. The echocardiography results showed that Ifs significantly decreased the main pulmonary artery diameter (P<0.05), right ventricular end-diastolic anteroposterior diameter (P<0.01), right ventricular end-diastolic trans diameter (P<0.01), right ventricular anterior wall (P<0.01) and right ventricular outflow tract (P<0.01). These results indicate the potential beneficial effects of Ifs in the reduction of excessive erythrocytosis, the alleviation of oxidative damage and the amelioration of right ventricular index and pulmonary hemodynamics in CMS.