Novel insight into the genetic basis of high-altitude pulmonary hypertension in Kyrgyz highlanders

Expression Profiles of circRNAs and Identification of hsa_circ_0007608 and hsa_circ_0064656 as Potential Biomarkers for COPD-PH Patients

Introduction

Pulmonary hypertension (PH) is a common complication of chronic obstructive pulmonary disease (COPD), which can worsen the prognosis and increase the mortality of COPD patients. Circular RNA (circRNA) has been discovered to participate in the occurrence and progression of PH in COPD and may have significant prospects for advanced diagnostics and prognosis evaluation. However, the expression profile of circRNAs in human lung tissues with definite diagnosis of COPD-PH remains to be further explored and validated.

Methods

Twelve human lung tissue samples (6 each from COPD-PH and control groups) were collected and subjected to high-throughput sequencing. QRT-PCR was performed to validate the differential expression levels of the top 10 dysregulated circRNAs in patients' plasma samples, HPAECs and HPASMCs. Functional and pathway enrichment analysis on target genes was performed to explore the potential functions and pathways of those circRNAs. Hub genes obtained after conducting bioinformatics analysis on the predicted target mRNAs were verified by qRT-PCR in HPAECs and HPASMCs, and then we selected VCAN as a potential key gene involved in the pathogenesis of COPD-PH for immunohistochemistry validation in lung tissue.

Results

A total of 136 circRNAs (39 up-regulated and 97 down-regulated) were differentially expressed between the two groups. Following qRT-PCR validation, two circRNAs (hsa_circ_0007608 and hsa_circ_0064656) were believed to be involved in the pathogenesis. GO and KEGG pathway analysis suggested that these two DECs were mainly related to the celluar proliferation, migration and EndMT. PPI network revealed 11 pairs of key mRNAs. VCAM1, VCAN and THBS1, three hub mRNAs with the highest reliability among all, were validated and proven to be up-regulated in COPD-PH. We innovatively found that VCAN may be involved in COPD-PH.

Conclusion

This study identified the functional circRNAs, providing insights into the molecular mechanisms and predictions of COPD-PH, and may provide potential diagnostic biomarkers or therapeutic targets for COPD-PH.

Single-cell analysis of peripheral blood from high-altitude pulmonary hypertension patients identifies a distinct monocyte phenotype

Immune and inflammatory responses have an important function in the pathophysiology of pulmonary hypertension (PH). However, little is known about the immune landscape in peripheral circulation in patients with high-altitude pulmonary hypertension (HAPH). We apply single-cell transcriptomics to characterize the monocytes that are significantly enriched in the peripheral blood mononuclear cells (PBMC) of HAPH patients. We discover an increase in C1 (non-classical) and C2 (intermediate) monocytes in PBMCs and a decrease in hypoxia-inducible transcription factor-1α (HIF-1α) in all monocyte subsets associated with HAPH. In addition, we demonstrate that similar immune adaptations may exist in HAPH and PH. Overall, we characterize an immune cell atlas of the peripheral blood in HAPH patients. Our data provide evidence that specific monocyte subsets and HIF-1α downregulation might be implicated in the pathogenesis of HAPH.

Establishing a prediction model of severe acute mountain sickness using machine learning of support vector machine recursive feature elimination

Severe acute mountain sickness (sAMS) can be life-threatening, but little is known about its genetic basis. The study was aimed to explore the genetic susceptibility of sAMS for the purpose of prediction, using microarray data from 112 peripheral blood mononuclear cell (PBMC) samples of 21 subjects, who were exposed to very high altitude (5260 m), low barometric pressure (406 mmHg), and hypobaric hypoxia (VLH) at various timepoints. We found that exposure to VLH activated gene expression in leukocytes, resulting in an inverted CD4/CD8 ratio that interacted with other phenotypic risk factors at the genetic level. A total of 2286 underlying risk genes were input into the support vector machine recursive feature elimination (SVM-RFE) system for machine learning, and a model with satisfactory predictive accuracy and clinical applicability was established for sAMS screening using ten featured genes with significant predictive power. Five featured genes (EPHB3, DIP2B, RHEBL1, GALNT13, and SLC8A2) were identified upstream of hypoxia- and/or inflammation-related pathways mediated by microRNAs as potential biomarkers for sAMS. The established prediction model of sAMS holds promise for clinical application as a genetic screening tool for sAMS.

The Oxygen Cascade from Atmosphere to Mitochondria as a Tool to Understand the (Mal)adaptation to Hypoxia

Hypoxia is a life-threatening challenge for about 1% of the world population, as well as a contributor to high morbidity and mortality scores in patients affected by various cardiopulmonary, hematological, and circulatory diseases. However, the adaptation to hypoxia represents a failure for a relevant portion of the cases as the pathways of potential adaptation often conflict with well-being and generate diseases that in certain areas of the world still afflict up to one-third of the populations living at altitude. To help understand the mechanisms of adaptation and maladaptation, this review examines the various steps of the oxygen cascade from the atmosphere to the mitochondria distinguishing the patterns related to physiological (i.e., due to altitude) and pathological (i.e., due to a pre-existing disease) hypoxia. The aim is to assess the ability of humans to adapt to hypoxia in a multidisciplinary approach that correlates the function of genes, molecules, and cells with the physiologic and pathological outcomes. We conclude that, in most cases, it is not hypoxia by itself that generates diseases, but rather the attempts to adapt to the hypoxia condition. This underlies the paradigm shift that when adaptation to hypoxia becomes excessive, it translates into maladaptation.

Local adaptations of Mediterranean sheep and goats through an integrative approach

Small ruminants are suited to a wide variety of habitats and thus represent promising study models for identifying genes underlying adaptations. Here, we considered local Mediterranean breeds of goats (n = 17) and sheep (n = 25) from Italy, France and Spain. Based on historical archives, we selected the breeds potentially most linked to a territory and defined their original cradle (i.e., the geographical area in which the breed has emerged), including transhumant pastoral areas. We then used the programs PCAdapt and LFMM to identify signatures of artificial and environmental selection. Considering cradles instead of current GPS coordinates resulted in a greater number of signatures identified by the LFMM analysis. The results, combined with a systematic literature review, revealed a set of genes with potentially key adaptive roles in relation to the gradient of aridity and altitude. Some of these genes have been previously implicated in lipid metabolism (SUCLG2, BMP2), hypoxia stress/lung function (BMPR2), seasonal patterns (SOX2, DPH6) or neuronal function (TRPC4, TRPC6). Selection signatures involving the PCDH9 and KLH1 genes, as well as NBEA/NBEAL1, were identified in both species and thus could play an important adaptive role.

Heterozygous Tropomodulin 3 mice have improved lung vascularization after chronic hypoxia

The molecular mechanisms leading to high altitude pulmonary hypertension (HAPH) remains poorly understood. We previously analyzed the whole genome sequence of Kyrgyz highland population and identified eight genomic intervals having a potential role in HAPH. Tropomodulin 3 gene (TMOD3) which encodes a protein that binds and caps the pointed ends of actin filaments and inhibits cell migration, was one of the top candidates. Here we systematically sought additional evidence to validate the functional role of TMOD3. In-silico analysis reveals that some of the SNPs in HAPH associated genomic intervals were positioned in a regulatory region that could result in alternative splicing of TMOD3. In order to functionally validate the role of TMOD3 in HAPH, we exposed Tmod3-/+ mice to 4 weeks of constant hypoxia, i.e. 10% O2 and analyzed both functional (hemodynamic measurements) and structural (angiography) parameters related to HAPH. The hemodynamic measurements, such as right ventricular systolic pressure, a surrogate measure for pulmonary arterial systolic pressure, and right ventricular contractility (RV- ± dP/dt), increases with hypoxia did not separate between Tmod3-/+ and control mice. Remarkably, there was a significant increase in the number of lung vascular branches and total length of pulmonary vascular branches (p < 0.001) in Tmod3-/+ after 4 weeks of constant hypoxia as compared to controls. Notably, the Tmod3-/+ endothelial cells migration was also significantly higher than that from the wild-type littermates. Our results indicate that, under chronic hypoxia, lower levels of Tmod3 play an important role in the maintenance or neo-vascularization of pulmonary arteries.

Pulmonary hypertension in majority countries: opportunities amidst challenges

PURPOSE OF REVIEW

Pulmonary hypertension is a deadly disease, the causes of which vary between geographical regions. Eighty four percentage of the world's population lives in majority countries (also called low-income and middle-income countries), yet data on pulmonary hypertension in these settings are proportionally scarce. This article provides a review of pulmonary hypertension in majority countries, focusing in detail on the most common causes in these regions, and highlights contextual challenges faced.

RECENT FINDINGS

Epidemiological data confirms a complex and overlapping array of causes, with pulmonary hypertension because of conditions such as rheumatic heart disease, HIV, schistosomiasis, chronic lung disease and sickle cell disease. Delayed pulmonary hypertension diagnosis remains a concern and is ascribed to a lack of resources and lack of pulmonary hypertension awareness by health professionals. Pulmonary hypertension diagnosis is frequently considered once signs of right heart failure emerge, while echocardiography and right heart catheterization are unavailable in many settings. Accurate data on the prevalence of pulmonary hypertension in many of these regions are needed and could be achieved by establishing and frequent review of national databases where the incident and prevalent pulmonary hypertension cases are captured.

SUMMARY

There is urgent need for pulmonary hypertension advocacy among clinicians in the primary, secondary and tertiary healthcare sectors of majority countries, and validated noninvasive diagnostic algorithms are needed. Increased awareness and early diagnosis are likely to improve outcomes of pulmonary hypertension patients in these regions, and potentially stimulate locally relevant research.

Genetics of pulmonary hypertension and high-altitude pulmonary edema

Heritable pulmonary arterial hypertension (PAH) is an autosomal dominantly inherited disease caused by mutations in the bone morphogenetic protein receptor 2 (BMPR2) gene and/or genes of its signaling pathway in ~85% of patients. A genetic predisposition to high-altitude pulmonary edema (HAPE) has long been suspected because of familial HAPE cases, but very few possibly disease-causing mutations have been identified to date. This minireview provides an overview of genetic analyses investigating common polymorphisms in HAPE-susceptible patients and the directed identification of disease-causing mutations in PAH patients. Increased pulmonary artery pressure is highlighted as an overlapping clinical feature of the two diseases. Moreover, studies showing increased pulmonary artery pressures in HAPE-susceptible patients during exercise or hypoxia as well as in healthy BMPR2 mutation carriers are illustrated. Finally, high-altitude pulmonary hypertension is introduced and future research perspectives outlined.

Pulmonary hypertension: From an orphan disease to a global epidemic

[No abstract. Showing first paragraph of article]Pulmonary hypertension is a progressive disease characterized by an elevation of pulmonary artery pressure and pulmonary vascular resistance, leading to right ventricular failure and death. It remains a challenging chronic progressive disease, but the current interest and advent of medical therapy in the last 20 years has significantly changed the perception of medical community in this disease. Pulmonary hypertension is not a specific disease; the majority of cases present with other diseases and various pathological processes that affect the pulmonary vasculature, and consequently increase pulmonary pressure and vascular resistance.