Today's and tomorrow's imaging and circulating biomarkers for pulmonary arterial hypertension

miRNAs orchestration of cardiovascular diseases - Particular emphasis on diagnosis, and progression

MicroRNAs (miRNAs; miRs) are small non-coding ribonucleic acids sequences vital in regulating gene expression. They are significant in many biological and pathological processes and are even detectable in various body fluids such as serum, plasma, and urine. Research has demonstrated that the irregularity of miRNA in multiplying cardiac cells is linked to developmental deformities in the heart's structure. It has also shown that miRNAs are crucial in diagnosing and progressing several cardiovascular diseases (CVDs). The review covers the function of miRNAs in the pathophysiology of CVD. Additionally, the review provides an overview of the potential role of miRNAs as disease-specific diagnostic and prognostic biomarkers for human CVD, as well as their biological implications in CVD.

MicroRNAs in Pulmonary Hypertension, from Pathogenesis to Diagnosis and Treatment

Pulmonary hypertension (PH) is a fatal and untreatable disease, ultimately leading to right heart failure and eventually death. microRNAs are small, non-coding endogenous RNA molecules that can regulate gene expression and influence various biological processes. Changes in microRNA expression levels contribute to various cardiovascular disorders, and microRNAs have been shown to play a critical role in PH pathogenesis. In recent years, numerous studies have explored the role of microRNAs in PH, focusing on the expression profiles of microRNAs and their signaling pathways in pulmonary artery smooth muscle cells (PASMCs) or pulmonary artery endothelial cells (PAECs), PH models, and PH patients. Moreover, certain microRNAs, such as miR-150 and miR-26a, have been identified as good candidates of diagnosis biomarkers for PH. However, there are still several challenges for microRNAs as biomarkers, including difficulty in normalization, specificity in PH, and a lack of longitudinal and big sample-sized studies. Furthermore, microRNA target drugs are potential therapeutic agents for PH treatment, which have been demonstrated in PH models and in humans. Nonetheless, synthetic microRNA mimics or antagonists are susceptible to several common defects, such as low drug efficacy, inefficient drug delivery, potential toxicity and especially, off-target effects. Therefore, finding clinically safe and effective microRNA drugs remains a great challenge, and further breakthrough is urgently needed.

LncRNA CASC2 inhibits hypoxia-induced pulmonary artery smooth muscle cell proliferation and migration by regulating the miR-222/ING5 axis

Background

Pulmonary arterial hypertension (PAH) is often characterized by cell proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs). LncRNA cancer susceptibility candidate 2 (CASC2) has been revealed to be involved in PASMC injury in hypoxia-induced pulmonary hypertension. However, the exact molecular mechanisms whereby CASC2 regulates PASMC proliferation and migration are still incompletely understood.

Methods

The expression levels of CASC2, miR-222 and inhibitor of growth 5 (ING5) were measured using quantitative real-time polymerase chain reaction (qRT-PCR) or western blot, respectively. Cell proliferation was analyzed by Cell Counting Kit-8 (CCK-8) assay. Wound healing assay was used to analyze cell migration ability. The relationship between miR-222 and CASC2 or ING5 was confirmed using bioinformatics analysis, luciferase reporter assay and RNA immunoprecipitation assay.

Results

CASC2 was down-regulated in hypoxia-induced PASMCs in a dose- and time-dependent manner. Functional experiments showed that CASC2 overexpression could reverse hypoxia-induced proliferation and migration of PASMCs. Bioinformatics analysis indicated that CASC2 acted as a competing endogenous RNA of miR-222, thereby regulating the expression of ING5, the downstream target of miR-222, in PASMCs. In addition, rescue assay suggested that the inhibition mediated by CASC2 of hypoxia-induced PASMC proliferation and migration could be attenuated by miR-222 inhibition or ING5 overexpression.

Conclusion

CASC2 attenuated hypoxia-induced PASMC proliferation and migration by regulating the miR-222/ING5 axis to prevent vascular remodeling and the development of PAH, providing a novel insight and therapeutic strategy for hypoxia-induced PAH.

Critical effects of epigenetic regulation in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by persistent pulmonary vasoconstriction and pulmonary vascular remodeling. The pathogenic mechanisms of PAH remain to be fully clarified and measures of effective prevention are lacking. Recent studies; however, have indicated that epigenetic processes may exert pivotal influences on PAH pathogenesis. In this review, we summarize the latest research findings regarding epigenetic regulation in PAH, focusing on the roles of non-coding RNAs, histone modifications, ATP-dependent chromatin remodeling and DNA methylation, and discuss the potential of epigenetic-based therapies for PAH.

Reliable and developmentally appropriate study end points are needed to achieve drug development for treatment of pediatric pulmonary arterial hypertension

OBJECTIVE

To identify suitable end points and surrogates for pediatric pulmonary arterial hypertension (PAH) as the lack of developmentally appropriate end point and clinical trials contribute to the unmet medical need.

STUDY DESIGN

Reviewed the efficacy end points and surrogates for all trials (1995 to 2013) that were submitted to the Food and Drug Administration (FDA) to support the approval of PAH therapy and conducted literature search.

RESULTS

An increase in the 6 min walking distance (6MWD) was used as a primary end point in 8/9 adult PAH trials. This end point is not suitable for infants and young children because of performance limitations and lack of control data. One adult PAH trial used time to the first morbidity or mortality event as a primary end point, which could potentially be used in pediatric PAH trials. In the sildenafil pediatric PAH trial, the change in pulmonary vascular resistance index or mean pulmonary artery pressure was used as a surrogate for the 6MWD to assess exercise capacity. However, two deaths and three severe adverse events during the catheterizations made this an unacceptably high-risk surrogate. The INOmax persistent pulmonary hypertension of the newborn trial used a reduction in initiation of extracorporeal membrane oxygenation treatment as a primary end point, which is not feasible for other pediatric PAH trials. A Literature review revealed none of the existing noninvasive markers are fully validated as surrogates to assess PAH efficacy and long-term safety.

CONCLUSIONS

For pediatric PAH trials, clinical end points are acceptable, and novel validated surrogates would be helpful. FDA seeks collaboration with academia, industry and parents to develop other suitable and possibly more efficient efficacy end points to facilitate pediatric PAH drug development.

The Role of Biomarkers and Surrogate End Points in Drug Development for Neonatal Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a rare disease in newborns, infants, and children. It is associated with significant morbidity and mortality, but has limited treatment options. Except for inhaled nitric oxide, which is approved for persistent pulmonary hypertension of the newborn (PPHN), no drug is approved for the treatment of newborns, infants, and children with PAH. The lack of developmentally appropriate pediatric efficacy end points and pediatric clinical trials contribute to this unmet medical need. The noninvasive biomarkers reported in the literature that can be used as potential surrogate end points to assess disease severity and treatment response in neonates, infants, and children with PAH are reviewed herein. In addition, the role of the US Food and Drug Administration in developing potential biomarkers as surrogate end points to facilitate drug development for the treatment of children with PPHN and PAH in children is reviewed herein.

Imaging the heart in pulmonary hypertension: an update

Noninvasive imaging of the heart plays an important role in the diagnosis and management of pulmonary hypertension (PH), and several well-established techniques are available for assessing performance of the right ventricle, the key determinant of patient survival. While right heart catheterisation is mandatory for establishing a diagnosis of PH, echocardiography is the most important screening tool for early detection of PH. Cardiac magnetic resonance imaging (CMRI) is also a reliable and practical tool that can be used as part of the diagnostic work-up. Echocardiography can measure a range of haemodynamic and anatomical variables (e.g. pericardial effusion and pulmonary artery pressure), whereas CMRI provides complementary information to echocardiography via high-resolution, three-dimensional imaging. Together with echocardiography and CMRI, techniques such as high-resolution computed tomography and positron emission tomography may also be valuable for screening, monitoring and follow-up assessments of patients with PH, but their clinical relevance has yet to be established. Technological advances have produced new variants of echocardiography, CMRI and positron emission tomography, and these permit closer examination of myocardial architecture, motion and deformation. Integrating these new tools into clinical practice in the future may lead to more precise noninvasive determination of diagnosis, risk and prognosis for PH.

Biomarkers for pediatric pulmonary arterial hypertension: challenges and recommendations

Pediatric pulmonary arterial hypertension (PAH) is an uncommon disease that can occur in neonates, infants, and children, and is associated with high morbidity and mortality. Despite advances in treatment strategies over the last two decades, the underlying structural and functional changes to the pulmonary arterial circulation are progressive and lead eventually to right heart failure. The management of PAH in children is complex due not only to the developmental aspects but also because most evidence-based practices derive from adult PAH studies. As such, the pediatric clinician would be greatly aided by specific characteristics (biomarkers) objectively measured in children with PAH to determine appropriate clinical management. This review highlights the current state of biomarkers in pediatric PAH and looks forward to potential biomarkers, and makes several recommendations for their use and interpretation.

Increasing pulmonary artery pulsatile flow improves hypoxic pulmonary hypertension in piglets

Pulmonary arterial hypertension (PAH) is a disease affecting distal pulmonary arteries (PA). These arteries are deformed, leading to right ventricular failure. Current treatments are limited. Physiologically, pulsatile blood flow is detrimental to the vasculature. In response to sustained pulsatile stress, vessels release nitric oxide (NO) to induce vasodilation for self-protection. Based on this observation, this study developed a protocol to assess whether an artificial pulmonary pulsatile blood flow could induce an NO-dependent decrease in pulmonary artery pressure. One group of piglets was exposed to chronic hypoxia for 3 weeks and compared to a control group of piglets. Once a week, the piglets underwent echocardiography to assess PAH severity. At the end of hypoxia exposure, the piglets were subjected to a pulsatile protocol using a pulsatile catheter. After being anesthetized and prepared for surgery, the jugular vein of the piglet was isolated and the catheter was introduced through the right atrium, the right ventricle and the pulmonary artery, under radioscopic control. Pulmonary artery pressure (PAP) was measured before (T0), immediately after (T1) and 30 min after (T2) the pulsatile protocol. It was demonstrated that this pulsatile protocol is a safe and efficient method of inducing a significant reduction in mean PAP via an NO-dependent mechanism. These data open up new avenues for the clinical management of PAH.

Selectins and platelet-derived growth factor (PDGF) in schistosomiasis-associated pulmonary hypertension

PURPOSE

The aim of this study was to evaluate the expression profiles of the relevant selectins and PDGF in schistosomiasis-associated pulmonary hypertension.

METHODOLOGY

Patients with three distinct clinical profiles were enrolled in the study: IPAH(n = 11), schistosomiasis-associated PH (Sch-PH))(n = 13), and schistosomiasis without PH (Sch) (n = 13). Healthy volunteers, were recruited as a control group(n = 13). Echocardiography was performed in all groups, and the PH patients underwent right heart catheterization. Plasma soluble adhesion molecules E- and P-Selectin, PDGF-AB, PDGF-BB were determined by ELISA.

RESULTS

E-selectin was significantly increased in the IPAH group compared with the other groups [the control, Sch + PH and Sch groups) (p < 0.001) (Fig. 2)]. P-selectin was lower in Sch (20.2 + 8.9 × 103 pg/mL) as compared to the control, (43 16.8 × 103 pg/mL), IPAH (35.8 7.8 × 103 pg/mL), and Sch + PH (36.8 ± 15.7 × 103 pg/mL) (p = 0.005) groups. Serum PDGF-BB levels were higher in the control group (8.9 ± 4.8 × 103 pg/mL) compared with the IPAH (3.7 ± 2.17 × 103 pg/mL), Sch + PH (5.2 ± 3.7 × 103 pg/mL) and Sch (2.4 ± 1.7 × 103 pg/mL) groups (p < 0.05). PDGF-AB levels were also higher in the control group (25.6 ± 8.6 × 103 pg/mL), compared with the other three groups, being the Sch group the one with lower serum levels of this marker (11.4 ± 8.6 × 103 pg/mL) (p = 0.006).

CONCLUSIONS

In conclusion, vascular inflammation in schistosomiasis, with or without PH, is different from IPAH suggesting distinct pathophysiological mechanisms associated with the development of pulmonary hypertension.

miRNAs in PAH: biomarker, therapeutic target or both?

Pulmonary arterial hypertension (PAH) is characterized by progressive increase in pulmonary vascular resistance leading to right ventricular hypertrophy and failure. There is a need to find new biomarkers to detect PAH at its early stages and also for new, more effective treatments for this disease. miRNAs have emerged as key players in cardiovascular diseases and cancer development and progression and, more recently, in PAH pathogenesis. In this review, we focus on the potential of miRNAs as biomarkers and new therapeutic targets for PAH.

Subcellular distribution patterns and elevated expression of GNA11 and GNA14 proteins in the lungs of humans with pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH), a progressive and devastating disease, is characterized by abnormal proliferation of pulmonary artery endothelial and smooth muscle cells. GTP-binding protein subunits, GNA11 and GNA14, transmembrane and intracellular signaling molecules, participate in the regulating endothelial function and vascular development. We followed the expression of GNA11 and GNA14 in human lungs in control and PAH patients using immunohistochemical and Western blot analyses. Both GNA11 and GNA14 were expressed in lung tissue, primarily in artery endothelial and smooth muscle cells. Expression was more pronounced in PAH lung tissues compared with controls. Using immunocytochemistry and laser scanning confocal microscopy, the subcellular distribution of GNA11 and GNA14 in human pulmonary arterial endothelial (HPAECs) and smooth muscle (HPASMCs) cells in culture was investigated. GNA11 was predominantly localized in the cytoplasm and nucleus of HPASMCs, but it was only found in the cytoplasm of HPAECs. On the other hand, GNA14 immunolocalized to the nucleus and cytoplasm of both HPAECs and HPASMCs. Based on bioinformatic analyses, nuclear localization signal and transmembrane topology confirm the different subcellular distributions of GNA11 and GNA14. The data suggest that GNA11 and GNA14 are related to PAH pathogenesis, and help further functional studies of these proteins in this severe disease.

Biomarkers for pediatric pulmonary arterial hypertension - a call to collaborate

Therapeutic approaches in pediatric pulmonary arterial hypertension (PAH) are based primarily on clinician experience, in contrast to the evidence-based approach in adults with pulmonary hypertension. There is a clear and present need for non-invasive and objective biomarkers to guide the accurate diagnosis, treatment, and prognosis of this disease in children. The multifaceted spectrum of disease, clinical presentation, and association with other diseases makes this a formidable challenge. However, as more progress is being made in the understanding and management of adult PAH, the potential to apply this knowledge to children has never been greater. This review explores the state of the art with regard to non-invasive biomarkers in PAH, with an eye toward those adult PAH biomarkers potentially suitable for application in pediatric PAH.