Stem cell therapy targeting the right ventricle in pulmonary arterial hypertension: is it a potential avenue of therapy?

Three-Dimensional Cell Cultures: The Bridge between In Vitro and In Vivo Models

Although historically, the traditional bidimensional in vitro cell system has been widely used in research, providing much fundamental information regarding cellular functions and signaling pathways as well as nuclear activities, the simplicity of this system does not fully reflect the heterogeneity and complexity of the in vivo systems. From this arises the need to use animals for experimental research and in vivo testing. Nevertheless, animal use in experimentation presents various aspects of complexity, such as ethical issues, which led Russell and Burch in 1959 to formulate the 3R (Replacement, Reduction, and Refinement) principle, underlying the urgent need to introduce non-animal-based methods in research. Considering this, three-dimensional (3D) models emerged in the scientific community as a bridge between in vitro and in vivo models, allowing for the achievement of cell differentiation and complexity while avoiding the use of animals in experimental research. The purpose of this review is to provide a general overview of the most common methods to establish 3D cell culture and to discuss their promising applications. Three-dimensional cell cultures have been employed as models to study both organ physiology and diseases; moreover, they represent a valuable tool for studying many aspects of cancer. Finally, the possibility of using 3D models for drug screening and regenerative medicine paves the way for the development of new therapeutic opportunities for many diseases.

A review on experimental surgical models and anesthetic protocols of heart failure in rats

Heart failure (HF) is a serious health and economic burden worldwide, and its prevalence is continuously increasing. Current medications effectively moderate the progression of symptoms, and there is a need for novel preventative and reparative treatments. The development of novel HF treatments requires the testing of potential therapeutic procedures in appropriate animal models of HF. During the past decades, murine models have been extensively used in fundamental and translational research studies to better understand the pathophysiological mechanisms of HF and develop more effective methods to prevent and control congestive HF. Proper surgical approaches and anesthetic protocols are the first steps in creating these models, and each successful approach requires a proper anesthetic protocol that maintains good recovery and high survival rates after surgery. However, each protocol may have shortcomings that limit the study's outcomes. In addition, the ethical regulations of animal welfare in certain countries prohibit the use of specific anesthetic agents, which are widely used to establish animal models. This review summarizes the most common and recent surgical models of HF and the anesthetic protocols used in rat models. We will highlight the surgical approach of each model, the use of anesthesia, and the limitations of the model in the study of the pathophysiology and therapeutic basis of common cardiovascular diseases.

Prostaglandin E1 reduces apoptosis and improves the homing of mesenchymal stem cells in pulmonary arterial hypertension by regulating hypoxia-inducible factor 1 alpha

Background

Pulmonary arterial hypertension (PAH) is associated with oxidative stress and affects the survival and homing of transplanted mesenchymal stem cells (MSCs) as well as cytokine secretion by the MSCs, thereby altering their therapeutic potential. In this study, we preconditioned the MSCs with prostaglandin E1 (PGE1) and performed in vitro and in vivo cell experiments to evaluate the therapeutic effects of MSCs in rats with PAH.

Methods

We studied the relationship between PGE1 and vascular endothelial growth factor (VEGF) secretion, B-cell lymphoma 2 (Bcl-2) expression, and C-X-C chemokine receptor 4 (CXCR4) expression in MSCs and MSC apoptosis as well as migration through the hypoxia-inducible factor (HIF) pathway in vitro. The experimental rats were randomly divided into five groups: (I) control group, (II) monocrotaline (MCT) group, (III) MCT + non-preconditioned (Non-PC) MSC group, (IV) MCT + PGE1-preconditioned (PGE1-PC) MSC group, and (V) MCT^{+PGE1+YC-1-PC}MSC group. We studied methane dicarboxylic aldehyde (MDA) levels, MSC homing to rat lungs, mean pulmonary artery pressure, pulmonary artery systolic pressure, right ventricular hypertrophy index, wall thickness index (%WT), and relative wall area index (%WA) of rat pulmonary arterioles.

Results

Preconditioning with PGE1 increased the protein levels of HIF-1 alpha (HIF-1α) in MSCs, which can reduce MSC apoptosis and increase the protein levels of CXCR4, MSC migration, and vascular endothelial growth factor secretion. Upon injection with ^PGE1-PCMSCs, the pulmonary artery systolic pressure, mean pulmonary artery pressure, right ventricular hypertrophy index, %WT, and %WA decreased in rats with PAH. ^PGE1-PCMSCs exhibited better therapeutic effects than ^non-PCMSCs. Interestingly, lificiguat (YC-1), an inhibitor of the HIF pathway, blocked the effects of PGE1 preconditioning.

Conclusions

Our findings indicate that PGE1 modulates the properties of MSCs by regulating the HIF pathway, providing insights into the mechanism by which PGE1 preconditioning can be used to improve the therapeutic potential of MSCs in PAH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03011-x.

Future Perspectives of Pulmonary Hypertension Treatment

Since the discovery of three major pathophysiological mechanisms of pulmonary arterial hypertension (PAH), including prostacyclin, endothelin and nitric oxide pathways, the therapeutic options for PAH have increased. Nevertheless, despite these advances, the prognosis remains unsatisfactory for many patients with PAH. With the progress of both pre-clinical and clinical research on PAH, several novel therapeutic targets have been identified for the treatment of PAH. In this study, we review updated information of novel pathophysiological pathways of pulmonary hypertension, mainly focusing on WHO Group I PAH. Drugs based on these pathways are currently under clinical or pre-clinical investigation, however they have been approved for clinical use. Large clinical trials are required to validate the clinical safety and effects of these novel therapies.

Autologous skeletal myoblast patch implantation prevents the deterioration of myocardial ischemia and right heart dysfunction in a pressure-overloaded right heart porcine model

Right ventricular dysfunction is a predictor for worse outcomes in patients with congenital heart disease. Myocardial ischemia is primarily associated with right ventricular dysfunction in patients with congenital heart disease and may be a therapeutic target for right ventricular dysfunction. Previously, autologous skeletal myoblast patch therapy showed an angiogenic effect for left ventricular dysfunction through cytokine paracrine effects; however, its efficacy in right ventricular dysfunction has not been evaluated. Thus, this study aimed to evaluate the angiogenic effect of autologous skeletal myoblast patch therapy and amelioration of metabolic and functional dysfunction, in a pressure-overloaded right heart porcine model. Pulmonary artery stenosis was induced by a vascular occluder in minipigs; after two months, autologous skeletal myoblast patch implantation on the right ventricular free wall was performed (n = 6). The control minipigs underwent a sham operation (n = 6). The autologous skeletal myoblast patch therapy alleviated right ventricular dilatation and ameliorated right ventricular systolic and diastolic dysfunction. 11C-acetate kinetic analysis using positron emission tomography showed improvement in myocardial oxidative metabolism and myocardial flow reserve after cell patch implantation. On histopathology, a higher capillary density and vascular maturity with reduction of myocardial ischemia were observed after patch implantation. Furthermore, analysis of mRNA expression revealed that the angiogenic markers were upregulated, and ischemic markers were downregulated after patch implantation. Thus, autologous skeletal myoblast patch therapy ameliorated metabolic and functional dysfunction in a pressure-overloaded right heart porcine model, by alleviating myocardial ischemia through angiogenesis.

Current and emerging therapeutic approaches to pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a progressive and fatal lung disease of multifactorial etiology. Most of the available drugs and FDA-approved therapies for treating pulmonary hypertension attempt to overcome the imbalance between vasoactive and vasodilator mediators, and restore the endothelial cell function. Traditional medications for treating PAH include the prostacyclin analogs and receptor agonists, phosphodiesterase 5 inhibitors, endothelin-receptor antagonists, and cGMP activators. While the current FDA-approved drugs showed improvements in quality of life and hemodynamic parameters, they have shown only very limited beneficial effects on survival and disease progression. None of them offers a cure against PAH, and the median survival rate remains less than three years from diagnosis. Extensive research efforts have led to the emergence of innovative therapeutic approaches in the area of PAH. In this review, we provide an overview of the current FDA-approved therapies in PAH and discuss the associated clinical trials and reported-side effects. As recent studies have led to the emergence of innovative therapeutic approaches in the area of PAH, we also focus on the latest promising therapies in preclinical studies such as stem cell-based therapies, gene transfer, and epigenetic therapies.

Pharmacology of Pulmonary Arterial Hypertension: An Overview of Current and Emerging Therapies

Pulmonary arterial hypertension is a rare and devastating disease characterized by an abnormal chronic increase in pulmonary arterial pressure above 20 mmHg at rest, with a poor prognosis if not treated. Currently, there is not a single fully effective therapy, even though a dozen of drugs have been developed in the last decades. Pulmonary arterial hypertension is a multifactorial disease, meaning that several molecular mechanisms are implicated in its pathology. The main molecular pathways regulating the pulmonary vasomotor tone-endothelin, nitric oxide, and prostacyclin-are the most biologically and therapeutically explored to date. However, drugs targeting these pathways have already found their limitations. In the last years, translational research and clinical trials have made a strong effort in suggesting and testing novel therapeutic strategies for this disease. These approaches involve targeting the main molecular pathways with novel drugs, drug repurposing for novel targets, and also using combinatorial therapies. In this review, we summarize current strategies and drugs targeting the endothelin, nitric oxide, and prostacyclin pathways, as well as, the emerging new drugs proposed to cope with vascular remodelling, metabolic switch, perivascular inflammation, epigenetic modifications, estrogen deregulation, serotonin, and other neurohumoral mechanisms characteristic of this disease. Nowadays, pulmonary arterial hypertension remains an incurable disease; however, the incoming new knowledge makes us believe that new promising therapies are coming to the clinical arena soon.

Pulmonary hypertension: Pathophysiology beyond the lung

Pulmonary hypertension (PH) is classically considered a disease of pulmonary vasculature which has been the predominant target for drug development and PH therapy. Despite significant advancement in recent years in identification of new drug targets and innovative treatment strategies, the prognosis of PH remains poor, with median survival of 5 years. Recent studies have demonstrated involvement of neuroinflammation, altered autonomic and gastrointestinal functions and increased trafficking of bone marrow-derived cells in cardiopulmonary pathophysiology. This has led to the proposal that PH could be considered a systemic disease involving complex interactions among many organs. Our objectives in this review is to summarize evidence for the involvement of the brain, bone marrow and gut in PH pathophysiology. Then, to synthesize all evidence supporting a brain-gut-lung interaction hypothesis for consideration in PH pathophysiology and finally to summarize unanswered questions and future directions to move this novel concept forward. This forward-thinking view, if proven by further experiments, would provide new opportunities and novel targets for the control and treatment of PH.

Therapeutic efficacy of mesenchymal stromal cells and secretome in pulmonary arterial hypertension: A systematic review and meta-analysis

Mesenchymal stromal cells (MSCs) and secretome are promising therapies for pulmonary arterial hypertension (PAH). This meta-analysis aimed to provide a precise estimate and compare the therapeutic efficacy of MSC and secretome in PAH. We searched six databases (CINAHL, Cochrane, Ovid Medline, PubMed, Science Direct and Scopus) until December 2018 using search terms related to MSCs, secretome and PAH. Twenty-three studies were included for the meta-analysis. The effect size of pulmonary hemodynamics and right ventricular hypertrophy markers was estimated using random effects model. MSCs and secretome significantly improved pulmonary hemodynamics and right ventricular hypertrophy compared to control. Comparison between MSCs and secretome indicate no significant difference in reducing right ventricular systolic pressure (RVSP) and medial wall thickening (MWT). However, treatment of PAH with secretome significantly improved mean pulmonary arterial pressure (mPAP) (p = 0.018) and right ventricular/left ventricular + septum (RV/LV+S) (p = 0.017) better than MSCs. Meta-regression shows that cell type (p = 0.034) is a predictor of MSCs to reduce RVSP in PAH. Similarly, the effect of secretome on MWT was significantly (p = 0.011) better at 4 weeks compared to 2 weeks of intervention. The overall risk of bias ranges from low to moderate; however, some of the essential elements required in reports of animal trials were not reported. There was evidence of publication bias for RV/LV+S and MWT, but not RVSP. This meta-analysis provides evidence of the therapeutic benefits of MSCs and secretome in PAH and the effect of secretome was similar or superior to MSCs.

Right Ventricular Fibrosis

The role of right ventricular (RV) fibrosis in pulmonary hypertension (PH) remains a subject of ongoing discussion. Alterations of the collagen network of the extracellular matrix may help prevent ventricular dilatation in the pressure-overloaded RV. At the same time, fibrosis impairs cardiac function, and a growing body of experimental data suggests that fibrosis plays a crucial role in the development of RV failure. In idiopathic pulmonary arterial hypertension and chronic thromboembolic PH, the RV is exposed to a ≈5 times increased afterload, which makes these conditions excellent models for studying the impact of pressure overload on RV structure. With this review, we present clinical evidence of RV fibrosis in idiopathic pulmonary arterial hypertension and chronic thromboembolic PH, explore the correlation between fibrosis and RV function, and discuss the clinical relevance of RV fibrosis in patients with PH. We postulate that RV fibrosis has a dual role in patients with pressure-overloaded RVs of idiopathic pulmonary arterial hypertension and chronic thromboembolic PH: as part of an adaptive response to prevent cardiomyocyte overstretch and to maintain RV shape for optimal function, and as part of a maladaptive response that increases diastolic stiffness, perturbs cardiomyocyte excitation-contraction coupling, and disrupts the coordination of myocardial contraction. Finally, we discuss potential novel therapeutic strategies and describe more sensitive techniques to quantify RV fibrosis, which may be used to clarify the causal relation between RV fibrosis and RV function in future research.

Mesenchymal stem/stromal cell therapy for pulmonary arterial hypertension: Comprehensive review of preclinical studies

Pulmonary arterial hypertension (PAH) is a disease characterized by progressive pulmonary vascular remodeling, resulting in right-sided heart failure and premature death. Current available therapies for PAH have limited efficacy, and new therapeutic strategies need to be developed. Mesenchymal stem/stromal cells (MSCs) may offer a novel therapeutic approach to PAH. Since the first report in 2006, a number of preclinical studies have demonstrated a potential therapeutic effect of this approach, with attenuated hemodynamic and histological progression of PAH, in animal models of PAH. However, there remain several issues that should be addressed for this approach to be clinically successful. With the aim to highlight such issues, this review clarifies existing knowledge on MSC therapy for PAH in preclinical studies, including types of PAH animal models used for MSC therapy, MSC sources, and administration protocol (route, cell dose, and timing of administration). This review thereafter summarizes thoroughly and discusses the mechanism underpinning MSC therapy for PAH. For clinical success of MSC therapy, insufficient evidence of safety (e.g. critical risk of pulmonary embolism) and therapeutic efficacy of MSCs on established PAH with severe vascular remodeling, as well as further optimization of the MSC administration protocol, are considered as remaining issues to be addressed. In terms of the efficacy, it is controversial whether angiogenic cytokines, which are considered as one of the therapeutic mechanisms of MSC, have beneficial effect for human PAH. To address these issues, further preclinical data using more clinically-relevant animal models of PAH, such as SU5416 model, should be accumulated, whereas most preclinical studies have been conducted using monocrotaline-induced PAH model. While MSC therapy has a great potential to become a novel therapy in PAH, continuing careful preclinical research is warranted for clinical success in PAH.

Paving the Road for Mesenchymal Stem Cell-Derived Exosome Therapy in Bronchopulmonary Dysplasia and Pulmonary Hypertension

Bronchopulmonary dysplasia (BPD) is a chronic neonatal lung disease characterized by inflammation and arrest of alveolarization. Its common sequela, pulmonary hypertension (PH), presents with elevated pulmonary vascular resistance associated with remodeling of the pulmonary arterioles. Despite notable advancements in neonatal medicine, there is a severe lack of curative treatments to help manage the progressive nature of these diseases. Numerous studies in preclinical models of BPD and PH have demonstrated that therapies based on mesenchymal stem/stromal cells (MSCs) can resolve pulmonary inflammation and ameliorate the severity of disease. Recent evidence suggests that novel, cell-free approaches based on MSC-derived exosomes (MEx) might represent a compelling therapeutic alternative offering major advantages over treatments based on MSC transplantation. Here, we will discuss the development of MSC-based therapies, stressing the centrality of paracrine action as the actual vector of MSC therapeutic functionality, focusing on MEx. We will briefly present our current understanding of the biogenesis and secretion of MEx, and discuss potential mechanisms by which they afford such beneficial effects, including immunomodulation and restoration of homeostasis in diseased states. We will also review ongoing clinical trials using MSCs as treatment for BPD that pave the way for bringing cell-free, MEx-based therapeutics from the bench to the NICU setting.

Drug abuse and HIV-related pulmonary hypertension: double hit injury

: Improved survival among HIV-1-infected individuals with the advent of antiretroviral therapy has clearly led to a greater prevalence of noninfectious complications. One of the most devastating sequelae in these individuals is the development of pulmonary arterial hypertension (PAH). Various epidemiological studies suggest worse survival of HIV-PAH patients when compared with other forms of PAH. Given that only a subset and not all HIV-infected individuals develop HIV-PAH, it is suggested that an additional second-hit of genetic or environmental trigger is needed for the development of PAH. In this context, it has been well documented that HIV patients who abuse illicit drugs such as stimulants, opioids, and the like, are more susceptible to develop PAH. In this review, we highlight the studies that support the significance of a double hit of HIV and drug abuse in the incidence of PAH and focus on the research that has been undertaken to unravel the pathobiology and vascular remodeling mechanisms underlying the deleterious synergy between HIV infection and drugs of abuse in orchestrating the development of PAH.

Autologous endothelial progenitor cell therapy improves right ventricular function in a model of chronic thromboembolic pulmonary hypertension

BACKGROUND

Right ventricular (RV) failure is the main prognostic factor in pulmonary hypertension, and ventricular capillary density (CD) has been reported to be a marker of RV maladaptive remodeling and failure. Our aim was to determine whether right intracoronary endothelial progenitor cell (EPC) infusion can improve RV function and CD in a piglet model of chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

We compared 3 groups: sham (n = 5), CTEPH (n = 6), and CTEPH with EPC infusion (CTEPH+EPC; n = 5). After EPC isolation from CTEPH+EPC piglet peripheral blood samples at 3 weeks, the CTEPH and sham groups underwent right intracoronary infusion of saline, and the CTEPH+EPC group received EPCs at 6 weeks. RV function, pulmonary hemodynamics, and myocardial morphometry were investigated in the animals at 10 weeks.

RESULTS

After EPC administration, the RV fractional area change increased from 32.75% (interquartile range [IQR], 29.5%-36.5%) to 39% (IQR, 37.25%-46.50%; P = .030). The CTEPH+EPC piglets had reduced cardiomyocyte surface areas (from 298.3 μm² [IQR, 277.4-335.3 μm²] to 234.6 μm² (IQR, 211.1-264.7 μm²; P = .017), and increased CD31 expression (from 3.12 [IQR, 1.27-5.09] to 7.14 [IQR, 5.56-8.41; P = .017). EPCs were found in the RV free wall at 4 and 24 hours after injection but not 4 weeks later.

CONCLUSIONS

Intracoronary infusion of EPC improved RV function and CD in a piglet model of CTEPH. This novel cell-based therapy might represent a promising RV-targeted treatment in patients with pulmonary hypertension.

Macrophage Immunomodulation: The Gatekeeper for Mesenchymal Stem Cell Derived-Exosomes in Pulmonary Arterial Hypertension?

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by remodeling of the pulmonary arteries, increased pulmonary infiltrates, loss of vascular cross-sectional area, and elevated pulmonary vascular resistance. Despite recent advances in the management of PAH, there is a pressing need for the development of new tools to effectively treat and reduce the risk of further complications. Dysregulated immunity underlies the development of PAH, and macrophages orchestrate both the initiation and resolution of pulmonary inflammation, thus, manipulation of lung macrophage function represents an attractive target for emerging immunomodulatory therapies, including cell-based approaches. Indeed, mesenchymal stem cell (MSC)-based therapies have shown promise, effectively modulating the macrophage fulcrum to favor an anti-inflammatory, pro-resolving phenotype, which is associated with both histological and functional benefits in preclinical models of pulmonary hypertension (PH). The complex interplay between immune system homeostasis and MSCs remains incompletely understood. Here, we highlight the importance of macrophage function in models of PH and summarize the development of MSC-based therapies, focusing on the significance of MSC exosomes (MEx) and the immunomodulatory and homeostatic mechanisms by which such therapies may afford their beneficial effects.