The role of cardiac pericytes in health and disease: therapeutic targets for myocardial infarction

Millions of cardiomyocytes die immediately after myocardial infarction, regardless of whether the culprit coronary artery undergoes prompt revascularization. Residual ischaemia in the peri-infarct border zone causes further cardiomyocyte damage, resulting in a progressive decline in contractile function. To date, no treatment has succeeded in increasing the vascularization of the infarcted heart. In the past decade, new approaches that can target the heart's highly plastic perivascular niche have been proposed. The perivascular environment is populated by mesenchymal progenitor cells, fibroblasts, myofibroblasts and pericytes, which can together mount a healing response to the ischaemic damage. In the infarcted heart, pericytes have crucial roles in angiogenesis, scar formation and stabilization, and control of the inflammatory response. Persistent ischaemia and accrual of age-related risk factors can lead to pericyte depletion and dysfunction. In this Review, we describe the phenotypic changes that characterize the response of cardiac pericytes to ischaemia and the potential of pericyte-based therapy for restoring the perivascular niche after myocardial infarction. Pericyte-related therapies that can salvage the area at risk of an ischaemic injury include exogenously administered pericytes, pericyte-derived exosomes, pericyte-engineered biomaterials, and pharmacological approaches that can stimulate the differentiation of constitutively resident pericytes towards an arteriogenic phenotype. Promising preclinical results from in vitro and in vivo studies indicate that pericytes have crucial roles in the treatment of coronary artery disease and the prevention of post-ischaemic heart failure.

The tyrosine kinase inhibitor Dasatinib reduces cardiac steatosis and fibrosis in obese, type 2 diabetic mice

BACKGROUND

Cardiac steatosis is an early yet overlooked feature of diabetic cardiomyopathy. There is no available therapy to treat this condition. Tyrosine kinase inhibitors (TKIs) are used as first or second-line therapy in different types of cancer. In cancer patients with diabetes mellitus, TKIs reportedly improved glycemic control, allowing insulin discontinuation. They also reduced liver steatosis in a murine model of non-alcoholic fatty liver disease. The present study aimed to determine the therapeutic effect of the second-generation TKI Dasatinib on lipid accumulation and cardiac function in obese, type 2 diabetic mice. We also assessed if the drug impacts extra-cardiac fat tissue depots.

METHODS

Two studies on 21-week-old male obese leptin receptor mutant BKS.Cg-+Leprdb/+Leprdb/OlaHsd (db/db) mice compared the effect of Dasatinib (5 mg/kg) and vehicle (10% DMSO + 90% PEG-300) given via gavage once every three days for a week or once every week for four weeks. Functional and volumetric indices were studied using echocardiography. Post-mortem analyses included the assessment of fat deposits and fibrosis using histology, and senescence using immunohistochemistry and flow cytometry. The anti-adipogenic action of Dasatinib was investigated on human bone marrow (BM)-derived mesenchymal stem cells (MSCs). Unpaired parametric or non-parametric tests were used to compare two and multiple groups as appropriate.

RESULTS

Dasatinib reduced steatosis and fibrosis in the heart of diabetic mice. The drug also reduced BM adiposity but did not affect other fat depots. These structural changes were associated with improved diastolic indexes, specifically the E/A ratio and non-flow time. Moreover, Dasatinib-treated mice had lower levels of p16 in the heart compared with vehicle-treated controls, suggesting an inhibitory impact of the drug on the senescence signalling pathway. In vitro, Dasatinib inhibited human BM-MSC viability and adipogenesis commitment.

CONCLUSIONS

Our findings suggest that Dasatinib opposes heart and BM adiposity and cardiac fibrosis. In the heart, this was associated with favourable functional consequences, namely improvement in an index of diastolic function. Repurposing TKI for cardiac benefit could address the unmet need of diabetic cardiac steatosis.

BPIFB4 and its longevity-associated haplotype protect from cardiac ischemia in humans and mice

Long-living individuals (LLIs) escape age-related cardiovascular complications until the very last stage of life. Previous studies have shown that a Longevity-Associated Variant (LAV) of the BPI Fold Containing Family B Member 4 (BPIFB4) gene correlates with an extraordinarily prolonged life span. Moreover, delivery of the LAV-BPIFB4 gene exerted therapeutic action in murine models of atherosclerosis, limb ischemia, diabetic cardiomyopathy, and aging. We hypothesize that downregulation of BPIFB4 expression marks the severity of coronary artery disease (CAD) in human subjects, and supplementation of the LAV-BPIFB4 protects the heart from ischemia. In an elderly cohort with acute myocardial infarction (MI), patients with three-vessel CAD were characterized by lower levels of the natural logarithm (Ln) of peripheral blood BPIFB4 (p = 0.0077). The inverse association between Ln BPIFB4 and three-vessel CAD was confirmed by logistic regression adjusting for confounders (Odds Ratio = 0.81, p = 0.0054). Moreover, in infarcted mice, a single administration of LAV-BPIFB4 rescued cardiac function and vascularization. In vitro studies showed that LAV-BPIFB4 protein supplementation exerted chronotropic and inotropic actions on induced pluripotent stem cell (iPSC)-derived cardiomyocytes. In addition, LAV-BPIFB4 inhibited the pro-fibrotic phenotype in human cardiac fibroblasts. These findings provide a strong rationale and proof of concept evidence for treating CAD with the longevity BPIFB4 gene/protein.

The longevity-associated BPIFB4 gene supports cardiac function and vascularization in aging cardiomyopathy

AIMS

The aging heart naturally incurs a progressive decline in function and perfusion that available treatments cannot halt. However, some exceptional individuals maintain good health until the very late stage of their life due to favourable gene-environment interaction. We have previously shown that carriers of a longevity-associated variant (LAV) of the BPIFB4 gene enjoy prolonged health spans and lesser cardiovascular complications. Moreover, supplementation of LAV-BPIFB4 via an adeno-associated viral vector improves cardiovascular performance in limb ischemia, atherosclerosis, and diabetes models. Here, we asked if the LAV-BPIFB4 gene could address the unmet therapeutic need to delay the heart's spontaneous aging.

METHODS AND RESULTS

Immunohistological studies showed a remarkable reduction in vessel coverage by pericytes in failing hearts explanted from elderly patients. This defect was attenuated in patients carrying the homozygous LAV-BPIFB4 genotype. Moreover, pericytes isolated from older hearts showed low levels of BPIFB4, depressed pro-angiogenic activity, and loss of ribosome biogenesis. LAV-BPIFB4 supplementation restored pericyte function and pericyte-endothelial cell interactions through a mechanism involving the nucleolar protein nucleolin. Conversely, BPIFB4 silencing in normal pericytes mimed the heart failure pericytes. Finally, gene therapy with LAV-BPIFB4 prevented cardiac deterioration in middle-aged mice and rescued cardiac function and myocardial perfusion in older mice by improving microvasculature density and pericyte coverage.

CONCLUSIONS

We report the success of the LAV-BPIFB4 gene/protein in improving homeostatic processes in the heart's aging. These findings open to using LAV-BPIFB4 to reverse the decline of heart performance in older people.

Cardiac pericyte reprogramming by MEK inhibition promotes arteriologenesis and angiogenesis of the ischemic heart

Pericytes (PCs) are abundant yet remain the most enigmatic and ill-defined cell population in the heart. Here, we investigated whether PCs can be reprogrammed to aid neovascularization. Primary PCs from human and mouse hearts acquired cytoskeletal proteins typical of vascular smooth muscle cells (VSMCs) upon exclusion of EGF/bFGF, which signal through ERK1/2, or upon exposure to the MEK inhibitor PD0325901. Differentiated PCs became more proangiogenic, more responsive to vasoactive agents, and insensitive to chemoattractants. RNA sequencing revealed transcripts marking the PD0325901-induced transition into proangiogenic, stationary VSMC-like cells, including the unique expression of 2 angiogenesis-related markers, aquaporin 1 (AQP1) and cellular retinoic acid-binding protein 2 (CRABP2), which were further verified at the protein level. This enabled us to trace PCs during in vivo studies. In mice, implantation of Matrigel plugs containing human PCs plus PD0325901 promoted the formation of αSMA+ neovessels compared with PC only. Two-week oral administration of PD0325901 to mice increased the heart arteriolar density, total vascular area, arteriole coverage by PDGFRβ+AQP1+CRABP2+ PCs, and myocardial perfusion. Short-duration PD0325901 treatment of mice after myocardial infarction enhanced the peri-infarct vascularization, reduced the scar, and improved systolic function. In conclusion, myocardial PCs have intrinsic plasticity that can be pharmacologically modulated to promote reparative vascularization of the ischemic heart.

The SARS-CoV-2 Spike protein disrupts human cardiac pericytes function through CD147 receptor-mediated signalling: a potential non-infective mechanism of COVID-19 microvascular disease

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes a broad range of clinical responses including prominent microvascular damage. The capacity of SARS-CoV-2 to infect vascular cells is still debated. Additionally, the SARS-CoV-2 Spike (S) protein may act as a ligand to induce non-infective cellular stress. We tested this hypothesis in pericytes (PCs), which are reportedly reduced in the heart of patients with severe coronavirus disease-2019 (COVID-19). Here we newly show that the in vitro exposure of primary human cardiac PCs to the SARS-CoV-2 wildtype strain or the α and δ variants caused rare infection events. Exposure to the recombinant S protein alone elicited signalling and functional alterations, including: (1) increased migration, (2) reduced ability to support endothelial cell (EC) network formation on Matrigel, (3) secretion of pro-inflammatory molecules typically involved in the cytokine storm, and (4) production of pro-apoptotic factors causing EC death. Next, adopting a blocking strategy against the S protein receptors angiotensin-converting enzyme 2 (ACE2) and CD147, we discovered that the S protein stimulates the phosphorylation/activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) through the CD147 receptor, but not ACE2, in PCs. The neutralisation of CD147, either using a blocking antibody or mRNA silencing, reduced ERK1/2 activation, and rescued PC function in the presence of the S protein. Immunoreactive S protein was detected in the peripheral blood of infected patients. In conclusion, our findings suggest that the S protein may prompt PC dysfunction, potentially contributing to microvascular injury. This mechanism may have clinical and therapeutic implications.

The SARS-CoV-2 Spike protein disrupts human cardiac pericytes function through CD147 receptor-mediated signalling: a potential non-infective mechanism of COVID-19 microvascular disease

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes a broad range of clinical responses including prominent microvascular damage. The capacity of SARS-CoV-2 to infect vascular cells is still debated. Additionally, the SARS-CoV-2 Spike (S) protein may act as a ligand to induce non-infective cellular stress. We tested this hypothesis in pericytes (PCs), which are reportedly reduced in the heart of patients with severe coronavirus disease-2019 (COVID-19). Here we newly show that the in vitro exposure of primary human cardiac PCs to the SARS-CoV-2 wildtype strain or the α and δ variants caused rare infection events. Exposure to the recombinant S protein alone elicited signalling and functional alterations, including: (1) increased migration, (2) reduced ability to support endothelial cell (EC) network formation on Matrigel, (3) secretion of pro-inflammatory molecules typically involved in the cytokine storm, and (4) production of pro-apoptotic factors causing EC death. Next, adopting a blocking strategy against the S protein receptors angiotensin-converting enzyme 2 (ACE2) and CD147, we discovered that the S protein stimulates the phosphorylation/activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) through the CD147 receptor, but not ACE2, in PCs. The neutralisation of CD147, either using a blocking antibody or mRNA silencing, reduced ERK1/2 activation, and rescued PC function in the presence of the S protein. Immunoreactive S protein was detected in the peripheral blood of infected patients. In conclusion, our findings suggest that the S protein may prompt PC dysfunction, potentially contributing to microvascular injury. This mechanism may have clinical and therapeutic implications.

The SARS-CoV-2 Spike protein alters human cardiac pericyte function and interaction with endothelial cells through a non-infective mechanism involving activation of CD147 receptor signalling

Background

Human cardiac pericytes (PC) were proposed as the main cellular target for SARS-CoV-2 in the heart due to high transcriptional levels of the angiotensin-converting enzyme 2 (ACE2) receptor. Emerging reports indicate CD147/Basigin (BSG), highly expressed in endothelial cells (EC), is an alternative SARS-CoV-2 receptor. To date, the mechanism by which the virus infects and disrupts the heart vascular cells was not identified yet. Moreover, cleaved Spike (S) protein molecules could be released into the bloodstream from the leaking pulmonary epithelial-endothelial barrier in patients with severe COVID-19, opening to the possibility of non-infective diseases in organs distant from the primary site of infection.

Purposes

(1) to confirm that human primary cardiac PC express ACE2 and CD147; (2) to verify if PC are permissible to SARS-CoV-2 infection; (3) to investigate if the recombinant SARS-CoV-2 S protein alone, without the other viral elements, can trigger molecular signalling and induce functional alterations in PC; (4) to explore which viral receptor is responsible for the observed events.

Methods and results

Cardiac PC express both the ACE2 and CD147 receptors at mRNA and protein level. Incubation of PC for up to 5 days with SARS-CoV-2 expressing the green fluorescent protein (GFP) did not show any evidence of cell infection or viral replication. Next, we exposed the PC to the recombinant S protein (5.8 nM) and confirmed that the protein engaged with cellular receptors (western blot analysis of S protein in treated and control PC). Incubation with the S protein increased PC migration (wound closure assay, P<0.01 vs ctrl) and reduced the formation of tubular structures between PC and EC in a Matrigel assay (P<0.01 vs ctrl). Moreover, the S protein promoted the production of pro-inflammatory factors typical of the cytokine storm in PC (ELISA measurement of MCP1, IL-6, IL-1β, TNFα, P<0.05 vs ctrl), and induced the secretion of pro-apoptotic factors responsible for EC death (Caspase 3/7 assay, P<0.05 vs ctrl). Signalling studies revealed that the S protein triggers the phosphorylation/activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) through the CD147 receptor, but not ACE2, in cardiac PC. The neutralization of CD147, using a blocking antibody, prevented ERK1/2 activation in PC, and was reflected into a partial rescue of the cell functional behaviour (migration and pro-angiogenic capacity). In contrast, blockage of CD147 failed to prevent the pro-inflammatory response in PC.

Conclusions

We propose the novel hypothesis that COVID-19 associated heart's microvascular dysfunction is prompted by circulating S protein molecules rather than by the direct coronavirus infection of PC. Besides, we propose CD147, and not ACE2, as the leading receptor mediating S protein signalling in cardiac PC.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): BHF project grant “Targeting the SARS-CoV-2 S-protein binding to the ACE2 receptor to preserve human cardiac pericytes function in COVID-19” BHF Centre for Vascular Regeneration II

Reconstruction of the Swine Pulmonary Artery Using a Graft Engineered With Syngeneic Cardiac Pericytes

The neonatal heart represents an attractive source of regenerative cells. Here, we report the results of a randomized, controlled, investigator-blinded preclinical study, which assessed the safety and effectiveness of a matrix graft cellularized with cardiac pericytes (CPs) in a piglet model of pulmonary artery (PA) reconstruction. Within each of five trios formed by 4-week-old female littermate piglets, one element (the donor) was sacrificed to provide a source of CPs, while the other two elements (the graft recipients) were allowed to reach the age of 10 weeks. During this time interval, culture-expanded donor CPs were seeded onto swine small intestinal submucosa (SIS) grafts, which were then shaped into conduits and conditioned in a flow bioreactor. Control unseeded SIS conduits were subjected to the same procedure. Then, recipient piglets were randomized to surgical reconstruction of the left PA (LPA) with unseeded or CP-seeded SIS conduits. Doppler echocardiography and cardiac magnetic resonance imaging (CMRI) were performed at baseline and 4-months post-implantation. Vascular explants were examined using histology and immunohistochemistry. All animals completed the scheduled follow-up. No group difference was observed in baseline imaging data. The final Doppler assessment showed that the LPA’s blood flow velocity was similar in the treatment groups. CMRI revealed a mismatch in the average growth of the grafted LPA and contralateral branch in both treatment groups. Histology of explanted arteries demonstrated that the CP-seeded grafts had a thicker luminal cell layer, more intraparietal arterioles, and a higher expression of endothelial nitric oxide synthase (eNOS) compared with unseeded grafts. Moreover, the LPA stump adjacent to the seeded graft contained more elastin and less collagen than the unseeded control. Syngeneic CP engineering did not accomplish the primary goal of supporting the graft’s growth but was able to improve secondary outcomes, such as the luminal cellularization and intraparietal vascularization of the graft, and elastic remodeling of the recipient artery. The beneficial properties of neonatal CPs may be considered in future bioengineering applications aiming to reproduce the cellular composition of native arteries.

Secreted Protein Acidic and Cysteine Rich Matricellular Protein is Enriched in the Bioactive Fraction of the Human Vascular Pericyte Secretome

Aims: To ascertain if human pericytes produce SPARC (acronym for Secreted Protein Acidic and Cysteine Rich), a matricellular protein implicated in the regulation of cell proliferation, migration, and cell-matrix interactions; clarify if SPARC expression in cardiac pericytes is modulated by hypoxia; and determine the functional consequences of SPARC silencing. Results: Starting from the recognition that the conditioned media (CM) of human pericytes promote proliferation and migration of cardiac stromal cells, we screened candidate mediators by mass-spectrometry analysis. Of the 14 high-confidence proteins (<1% FDR) identified in the bioactive fractions of the pericyte CM, SPARC emerged as the top-scored matricellular protein. SPARC expression was validated using ELISA and found to be upregulated by hypoxia/starvation in pericytes that express platelet-derived growth factor receptor α (PDGFRα). This subfraction is acknowledged to play a key role in extracellular matrix remodeling. Studies in patients with acute myocardial infarction showed that peripheral blood SPARC correlates with the levels of creatine kinase Mb, a marker of cardiac damage. Immunohistochemistry analyses of infarcted hearts revealed that SPARC is expressed in vascular and interstitial cells. Silencing of SPARC reduced the pericyte ability to secrete collagen1a1, without inhibiting the effects of CM on cardiac and endothelial cells. These data indicate that SPARC is enriched in the bioactive fraction of the pericyte CM, is induced by hypoxia and ischemia, and is essential for pericyte ability to produce collagen. Innovation: This study newly indicates that pericytes are a source of the matricellular protein SPARC. Conclusion: Modulation of SPARC production by pericytes may have potential implications for postinfarct healing.

Treatment of COVID-19 by stage: any space left for mesenchymal stem cell therapy?

In many countries, COVID-19 now accounts for more deaths per year than car accidents and even the deadliest wars. Combating the viral pandemics requires a coordinated effort to develop therapeutic protocols adaptable to the disease severity. In this review article, we summarize a graded approach aiming to shield cells from SARS-CoV-2 entry and infection, inhibit excess inflammation and evasion of the immune response, and ultimately prevent systemic organ failure. Moreover, we focus on mesenchymal stem cell therapy, which has shown safety and efficacy as a treatment of inflammatory and immune diseases. The cell therapy approach is now repurposed in patients with severe COVID-19. Numerous trials of mesenchymal stem cell therapy are ongoing, especially in China and the USA. Leader companies in cell therapy have also started controlled trials utilizing their quality assessed cell products. Results are too premature to reach definitive conclusions.

Human adventitial pericytes provide a unique source of anti-calcific cells for cardiac valve engineering: Role of microRNA-132-3p

AIMS

Tissue engineering aims to improve the longevity of prosthetic heart valves. However, the optimal cell source has yet to be determined. This study aimed to establish a mechanistic rationale supporting the suitability of human adventitial pericytes (APCs).

METHODS AND RESULTS

APCs were immunomagnetically sorted from saphenous vein leftovers of patients undergoing coronary artery bypass graft surgery and antigenically characterized for purity. Unlike bone marrow-derived mesenchymal stromal cells (BM-MSCs), APCs were resistant to calcification and delayed osteochondrogenic differentiation upon high phosphate (HP) induction, as assessed by cytochemistry and expression of osteogenic markers. Moreover, glycolysis was activated during osteogenic differentiation of BM-MSCs, whereas APCs showed no increase in glycolysis upon HP challenge. The microRNA-132-3p (miR-132), a known inhibitor of osteogenesis, was found constitutively expressed by APCs and upregulated following HP stimulation. The anti-calcific role of miR-132 was further corroborated by in silico analysis, luciferase assays in HEK293 cells, and transfecting APCs with miR-132 agomir and antagomir, followed by assessment of osteochondrogenic markers. Interestingly, treatment of swine cardiac valves with APC-derived conditioned medium conferred them with resistance to HP-induced osteogenesis, with this effect being negated when using the medium of miR-132-silenced APCs. Additionally, as an initial bioengineering step, APCs were successfully engrafted onto pericardium sheets, where they proliferated and promoted aortic endothelial cells attraction, a process mimicking valve endothelialization.

CONCLUSIONS

Human APCs are resistant to calcification compared with BM-MSCs and convey the anti-calcific phenotype to heart valves through miR-132. These findings may open new important avenues for prosthetic valve cellularization.

Umbilical Cord Pericytes Provide a Viable Alternative to Mesenchymal Stem Cells for Neonatal Vascular Engineering

Reconstructive surgery of congenital heart disease (CHD) remains inadequate due to the inability of prosthetic grafts to match the somatic growth of pediatric patients. Functionalization of grafts with mesenchymal stem cells (MSCs) may provide a solution. However, MSCs represent a heterogeneous population characterized by wide diversity across different tissue sources. Here we investigated the suitability of umbilical cord pericytes (UCPs) in neonatal vascular engineering. Explant outgrowth followed by immunomagnetic sorting was used to isolate neural/glial antigen 2 (NG2)+/CD31- UCPs. Expanded NG2 UCPs showed consistent antigenic phenotype, including expression of mesenchymal and stemness markers, and high proliferation rate. They could be induced to a vascular smooth muscle cell-like phenotype after exposure to differentiation medium, as evidenced by the expression of transgelin and smooth muscle myosin heavy chain. Analysis of cell monolayers and conditioned medium revealed production of extracellular matrix proteins and the secretion of major angiocrine factors, which conferred UCPs with ability to promote endothelial cell migration and tube formation. Decellularized swine-derived grafts were functionalized using UCPs and cultured under static and dynamic flow conditions. UCPs were observed to integrate into the outer layer of the graft and modify the extracellular environment, resulting in improved elasticity and rupture strain in comparison with acellular grafts. These findings demonstrate that a homogeneous pericyte-like population can be efficiently isolated and expanded from human cords and integrated in acellular grafts currently used for repair of CHD. Functional assays suggest that NG2 UCPs may represent a viable option for neonatal tissue engineering applications.

Fabrication of New Hybrid Scaffolds for in vivo Perivascular Application to Treat Limb Ischemia

Cell therapies are emerging as a new therapeutic frontier for the treatment of ischemic disease. However, femoral occlusions can be challenging environments for effective therapeutic cell delivery. In this study, cell-engineered hybrid scaffolds are implanted around the occluded femoral artery and the therapeutic benefit through the formation of new collateral arteries is investigated. First, it is reported the fabrication of different hybrid “hard-soft” 3D channel-shaped scaffolds comprising either poly(ε-caprolactone) (PCL) or polylactic-co-glycolic acid (PLGA) and electro-spun of gelatin (GL) nanofibers. Both PCL-GL and PLGA-GL scaffolds show anisotropic characteristics in mechanical tests and PLGA displays a greater rigidity and faster degradability in wet conditions. The resulting constructs are engineered using human adventitial pericytes (APCs) and both exhibit excellent biocompatibility. The 3D environment also induces expressional changes in APCs, conferring a more pronounced proangiogenic secretory profile. Bioprinting of alginate-pluronic gel (AG/PL), containing APCs and endothelial cells, completes the hybrid scaffold providing accurate spatial organization of the delivered cells. The scaffolds implantation around the mice occluded femoral artery shows that bioengineered PLGA hybrid scaffold outperforms the PCL counterpart accelerating limb blood flow recovery through the formation arterioles with diameters >50 μm, demonstrating the therapeutic potential in stimulating reparative angiogenesis.

Heart failure impairs the mechanotransduction properties of human cardiac pericytes

The prominent impact that coronary microcirculation disease (CMD) exerts on heart failure symptoms and prognosis, even in the presence of macrovascular atherosclerosis, has been recently acknowledged. Experimental delivery of pericytes in non-revascularized myocardial infarction improves cardiac function by stimulating angiogenesis and myocardial perfusion. Aim of this work is to verify if pericytes (Pc) residing in ischemic failing human hearts display altered mechano-transduction properties and to assess which alterations of the mechano-sensing machinery are associated with the observed impaired response to mechanical cues. RESULTS: Microvascular rarefaction and defects of YAP/TAZ activation characterize failing human hearts. Although both donor (D-) and explanted (E-) heart derived cardiac Pc support angiogenesis, D-Pc exert this effect significantly better than E-Pc. The latter are characterized by reduced focal adhesion density, decreased activation of the focal adhesion kinase (FAK)/ Crk-associated substrate (CAS) pathway, low expression of caveolin-1, and defective transduction of extracellular stiffness into cytoskeletal stiffening, together with an impaired response to both fibronectin and lysophosphatidic acid. Importantly, Mitogen-activated protein kinase kinase inhibition restores YAP/TAZ nuclear translocation. CONCLUSION: Heart failure impairs Pc mechano-transduction properties, but this defect could be reversed pharmacologically.

Umbilical cord-derived pericytes present an optimal cell population for vascular tissue engineering in newborns

Introduction

Newborns with severe congenital heart defects often require implantation of a graft to replace defective arteries and valves soon after birth. The current materials used for grafts all possess an inability to integrate and grow with the patient, resulting in repeated surgical interventions to replace failed grafts. Tissue engineering has aimed to address this limitation by seeding grafts with cells to create a biological “living” graft, however, the choice of cells is a critical aspect that is often not thoroughly explored, and thus limited success has been achieved. Here we identify and characterise a novel umbilical cord-derived pericyte (UCP) population with enhanced therapeutic potential for vascular tissue engineering in patients with CHD.

Methods and results

CD31-/NG2+ UCPs were isolated from the umbilical cord by explant outgrowth, and purified using magnetic activated cell sorting and flow cytometry. Doubling time and viability was quantified by counting cells on consecutive days for 1 week. UCPs maintained a viability of above 90% throughout culture and demonstrated a population doubling time of 50–70 hours. To assess angiogenic potential, endothelial-fibroblast cocultures were treated with UCP-conditioned medium and the cumulative tube network was measured. UCPs induced an increase of 9.9mm±2mm in tube length whereas mesenchymal stromal cells (MSCs) only induced a 1.8±1mm increase. The promigratory effect of UCPs on endothelial cells was tested using a scratch assay treated with conditioned medium. Endothelial cells treated with UCP conditioned medium demonstrated a 3.0±0.2-fold increase in migration compared with endothelial cells treated with MSC conditioned medium. Finally, the capability of UCPs to form functional vascular tissue was assessed using a differentiation and contraction assay. Differentiated cells demonstrated an increased expression of vascular smooth muscle markers alpha smooth muscle actin (aSMA; 7.1±1.6 protein fold change vs control), calponin (22.5±3.9 protein fold change vs control), Transgelin (7.4±1.6 protein fold change vs control) and smooth muscle myosin heavy chain (SM-MHC; 1.7±0.1 protein fold change vs control). Both differentiated and undifferentiated UCPs exhibited a contractile response to vasoactive peptide endothelin-1, however, differentiated UCPs demonstrated a 65.3±14.9% increase in contraction from the inhibited state, compared to 37.3±10.7% for undifferentiated UCPs.

Conclusion

UCPs are an ideal autologous cell population for vascular tissue engineering in newborns. They are capable of forming functional vascular tissue and can be expanded sufficiently within the surgical window for CHD treatment. Furthermore, UCPs hold distinct advantages over MSCs. Namely, UCPs induce a greater increase in endothelial migration and network formation, which is essential for endothelisation and perfusion of engineered tissue.

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): Heart Research UK

Rescue of cardiac function in obese type-2 diabetic mice by transfer of a human longevity gene

Background

Healthy longevity is the result of the interaction between favourable environment and unique genetic makeup. We showed that horizontal transfer of a longevity-associated gene variant (LAV-BPIFB4) improves endothelial function and accelerates the recovery from ischemia.

Purpose

To determine if the benefit of LAV-BPIFB4 gene therapy can be extended to diabetic cardiomyopathy.

Methods and results

We confirmed that human diabetic patients with heart failure (n=13) show a decreased cardiac expression of BPIFB4 compared with healthy subjects (n=10). Obese db/db mice received a systemic injection of adeno-associated viral vector (AAV9)-LAV-BPIFB4, AAV9-wild type (WT)-BPIFB4 (both 100 μL at 1×1012 GC/mL) or vehicle before the onset of cardiomyopathy, and were euthanised four weeks later for histological, metabolic and transcriptional analyses. Echocardiographic evaluation (n=8/group), performed at baseline and after gene therapy, showed that LAV-BPIFB4 treatment, despite not resolving hyperglycaemia, improved left ventricular function compared with the other groups. Histological analyses of the hearts (n=5 to 10/group) revealed that LAV-BPIFB4 reduced myocardial fibrosis and increased angiogenesis compared with vehicle and WT-hearts; moreover, LAV increased the expression of the alpha-isoform of the cardiac myosin heavy chain, which is associated with a superior cardiomyocyte contractility. Interestingly, LAV-BPIFB4 treatment induced an increase in cardiac SDF1 expression compared with WT and vehicle, despite the mechanism linking the two events is still unknown. The oral administration of the CXCR4 antagonist AMD-070, given at 2 mg/kg/day for four weeks, abolished several of the beneficial effects exerted by the LAV-BPIFB4 therapy in the obese diabetic mice, as assessed by echocardiography and histology (n=7/group).

At the molecular level, next-generation RNA sequencing (n=3 to 4 /group) showed 8 genes were differentially expressed by LAV-BPIFB4-hearts compared with vehicle-hearts. These genes are associated with mitochondrial and metabolic functions. Among them, changes in the UCP3, HMGCS2, CS, ATPB and TOMM20 expression were also validated at the protein level by western blotting. Lipidomics using ultrahigh-performance liquid chromatography-mass spectrometry (n=6 or 7/group) showed 63 metabolites differentially expressed by LAV-BPIFB4- compared with vehicle-hearts, with only 3 (two cardiolipins and one glycerophospholipid) returning close to the non-diabetic phenotype following LAV-BPIFB4 treatment.

Conclusions

This study newly shows the possibility of transferring the benefit of salutary polymorphic gene variants to protect the cardiovascular system from metabolic pressure. Rather than combating pathogenic mechanisms, the strategy activates alternative pathways overriding disease risk factors.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): British Heart Foundation project grant “Longevity-associated BPIFB4 gene therapy for treatment of ischemic disease”

Human adventitial pericytes secrete bioactive factors exerting distinct biological effects on cardiac cells: hints for cardiac repair

Background

Pericytes are attracting much attention as potential candidates for successful cell therapy of myocardial ischaemia. Intramyocardially delivered adventitial pericytes (APCs) secrete paracrine factors which stimulate angiogenesis and recruitment of cardiac stromal cells, reduce fibrosis and promote cardiomyocyte proliferation and viability. However, factors responsible for these biological effects have not been elucidated yet.

Purpose

To exploit the components of APC secretome exerting a biological effect on cardiac cells with the aim to discover new druggable targets with potential therapeutic activity.

Methods and results

APCs were derived from saphenous veins of adult patients (n=13, 68±11 yrs, all with coronary artery disease - CAD). The APC-conditioned medium (CM) stimulated the proliferation of human iPS-derived cardiomyocytes compared with unconditioned medium (UCM) (EdU incorporation, 1.3-fold increases, P=0.004). Stimulation with APC-CM increased the number of mitotic figures in cardiomyocytes (Aurora B, 1.5-fold increases compared to UCM, P=0.002). Furthermore, APC-CM abrogated the hypoxia-induced apoptosis in cardiomyocytes (2-fold increase in Caspase 3/7 activity in hypoxic cells exposed to UCM compared to normoxic cells, P=0.002). We also found that APC-CM stimulates the migration of human cardiac stromal cells (CSCs) obtained from healthy donors (n=6, 54±11 yrs) in both a transwell and scratch migration assays (n=6, P&lt;0.01 and P&lt;0.05 vs UCM respectively). Interestingly, APC-CM activated also the migration of HUVECs (n=6, P&lt;0.01 vs UCM) but did not attract fibroblasts. Next, we aimed to identify the biologically active components of the APC-CM. Depletion of exosomes and heat and RNase treatments did not abolish the pro-migratory action of the APC-CM, while this was abrogated by Proteinase K. Fractionation of the APC-CM based on the MW indicated that the bioactive peptides have MW &gt;30KDa. The pro-migratory fractions of the APC-CM obtained from size exclusion chromatography underwent mass spectrometry analysis (n=3 APCs). This identified 14 proteins uniquely present in the pro-migratory fractions. The two most relevant candidates were SPARC and TGFBI, both confirmed by ELISA. Intriguingly, the recombinant SPARC and TGFBI failed to reproduce the biological effect of APC-CM on CSC migration, suggesting that the secreted proteins may carry unique post-translational modifications not found in synthetic peptides. Further analyses are being carried out to reveal the biological properties of the endogenous SPARC and TGFBI.

Conclusions

This study suggests a fascinating approach based on the use of the active component of the APC-CM as a surrogate of APC therapy. If the biological properties of the cellular proteins will be successfully reproduced in synthetic peptides in vitro, this innovative approach may extend the benefits of APC therapy to all those patients with CAD for whom cell therapy is not an available option.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): British Heart Foundation programme grant “Unravelling mechanism of stem cell depletion for the preservation of regenerative fitness in patients with diabetes”

A short term treatment with a Mek1/2 inhibitor promotes myocardial arteriogenesis and perfusion in vivo: focus on cardiac mural cells

Background

Arteriogenesis is crucial for heart recovery after ischaemia, but cellular and molecular mechanisms able to foster this phenomenon are still poorly characterised.

Purpose

To discover novel pro-arteriogenic approaches by exploiting cardiac mural cells endowed with arteriogenic capacity: pericytes (PCs) and vascular smooth muscle cells (VSMCs).

Methods and results

We derived human and murine CD31neg CD34pos cardiac PCs (cPCs) from myocardial samples of adult subjects and confirmed the pericyte phenotype and function in vitro. We discovered that the withdrawal of EGF and bFGF from the culture media induces the differentiation of cPCs into contractile VSMCs. Molecular investigations of pathways associated with the two factors showed that the Mek1/2-Erk1/2 signalling exerts an inhibitory transcriptional control on contractile VSMC genes. Screening of compounds able to interfere with this pathway revealed that PD0325901 – a potent Mek1/2 inhibitor (MeKi) tested in clinical trials for the treatment of cancer – activates the VSMC phenotype in cPCs. We observed a similar effect on coronary artery VSMCs. Next, we interrogated the effect of PD0325901 on cardiac arteriogenesis in vivo. Adult C57BL6/J mice were given the MeKi 10 mg/kg/day or vehicle (DMSO), orally for 14 days (n=11/group). At the endpoint, echocardiographic evaluation of left ventricle (LV) function and dimensions (n=6/group) showed no difference in comparison with the respective baseline in both groups. Effective inhibition of Mek1/2 in the heart of PD-treated mice was confirmed by the reduced immunostaining for the phosphorylated form of Erk1/2. The MeKi cardiotoxicity was ruled out by assessment of cardiomyocytes and vascular cells apoptosis (Tunel) and plasmatic levels of cTn-I. Histological analyses of the hearts (n=5/group) showed an increase in small arterioles (diameter &lt;20μm) density in the LV of PD-mice compared with the DMSO group (16.4 vs 11.7 art/mm2). No change was observed for the capillary density. The drug promoted the maturation of VSMCs within both small and large (&gt;20μm) arterioles, as shown by the higher ratio between the areas of the vascular wall occupied by the mature contractile marker SM myosin heavy chain and the synthetic/early contractile marker alpha-SM actin (αSMA). The PD treatment reduced the fraction of small arterioles covered with a CD34pos layer (53% vs 70% of total arterioles), along with a lower ratio between the areas occupied by adventitial CD34pos cells and αSMApos VSMCs, suggesting a contribution of cPCs to the arteriolar remodelling. Last, the drug improved the LV myocardial perfusion in the PD- vs the DMSO-group (6.8 vs 5.3 ml/min/g of LV tissue, n=6/group).

Conclusions

We show that a short treatment with a Mek1/2 inhibitor stimulates myocardial arteriogenesis and perfusion without either inducing cardiotoxicity or deteriorating heart function. This may be a novel, intriguing approach to promote therapeutic arteriogenesis.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): British Heart Foundation Centre for Vascular Regeneration II

Transfer of a human gene variant associated with exceptional longevity improves cardiac function in obese type 2 diabetic mice through induction of the SDF-1/CXCR4 signalling pathway

AIMS

Homozygosity for a four-missense single-nucleotide polymorphism haplotype of the human BPIFB4 gene is enriched in long-living individuals. Delivery of this longevity-associated variant (LAV) improved revascularisation and reduced endothelial dysfunction and atherosclerosis in mice through a mechanism involving the stromal cell-derived factor-1 (SDF-1). Here, we investigated if delivery of the LAV-BPIFB4 gene may attenuate the progression of diabetic cardiomyopathy.

METHODS AND RESULTS

Compared with age-matched lean controls, diabetic db/db mice showed altered echocardiographic indices of diastolic and systolic function and histological evidence of microvascular rarefaction, lipid accumulation, and fibrosis in the myocardium. All these alterations, as well as endothelial dysfunction, were prevented by systemic LAV-BPIFB4 gene therapy using an adeno-associated viral vector serotype 9 (AAV9). In contrast, AAV9 wild-type-BPIFB4 exerted no benefit. Interestingly, LAV-BPIFB4-treated mice showed increased SDF-1 levels in peripheral blood and myocardium and up-regulation of the cardiac myosin heavy chain isoform alpha, a contractile protein that was reduced in diabetic hearts. SDF-1 up-regulation was instrumental to LAV-BPIFB4-induced benefit as both haemodynamic and structural improvements were inhibited by an orally active antagonist of the SDF-1 CXCR4 receptor.

CONCLUSIONS

In mice with type-2 diabetes, LAV-BPIFB4 gene therapy promotes an advantageous remodelling of the heart, allowing it to better withstand diabetes-induced stress. These results support the viability of transferring healthy characteristics of longevity to attenuate diabetic cardiac disease.

In Vitro and In Vivo Preclinical Testing of Pericyte-Engineered Grafts for the Correction of Congenital Heart Defects

Background

We have previously reported the possibility of using pericytes from leftovers of palliative surgery of congenital heart disease to engineer clinically certified prosthetic grafts.

Methods and Results

Here, we assessed the feasibility of using prosthetic conduits engineered with neonatal swine pericytes to reconstruct the pulmonary artery of 9‐week‐old piglets. Human and swine cardiac pericytes were similar regarding anatomical localization in the heart and antigenic profile following isolation and culture expansion. Like human pericytes, the swine surrogates form clones after single‐cell sorting, secrete angiogenic factors, and extracellular matrix proteins and support endothelial cell migration and network formation in vitro. Swine pericytes seeded or unseeded (control) CorMatrix conduits were cultured under static conditions for 5 days, then they were shaped into conduits and incubated in a flow bioreactor for 1 or 2 weeks. Immunohistological studies showed the viability and integration of pericytes in the outer layer of the conduit. Mechanical tests documented a reduction in stiffness and an increase in strain at maximum load in seeded conduits in comparison with unseeded conduits. Control and pericyte‐engineered conduits were then used to replace the left pulmonary artery of piglets. After 4 months, anatomical and functional integration of the grafts was confirmed using Doppler echography, cardiac magnetic resonance imaging, and histology.

Conclusions

These findings demonstrate the feasibility of using neonatal cardiac pericytes for reconstruction of small‐size branch pulmonary arteries in a large animal model.

Personalized Cardiovascular Regenerative Medicine: Targeting the Extreme Stages of Life

Cardiovascular regenerative medicine is an exciting new approach that promises to change the current care of million people world-wide. Major emphasis was given to the quality and quantities of regenerative products, but recent evidence points to the importance of a better specification of the target population that may take advantage of these advanced medical treatments. Patient stratification is an important step in drug development. Tailoring treatment to the patient's specificity allowed significant improvement in cancer therapy, but personalized regenerative medicine is still at the initial stage in the cardiovascular field. For example, new-borns with a congenital heart condition and elderly people require dedicated therapeutic approaches, which adapt to their lifetime needs. In these people, personalized treatments may overcome the benefits delivered by standard protocols. In this review, we provide insights into these extreme stages of life as potential targets for cardiovascular reconstitution.

The Effect of Matrix Stiffness of Biomimetic Gelatin Nanofibrous Scaffolds on Human Cardiac Pericyte Behavior

Congenital heart disease (CHD) is the most common and deadly congenital anomaly, accounting for up to 7.5% of all infant deaths. Survival in children born with CHD has improved dramatically over the past several decades (this positive trend being counterbalanced by the fact that more patients develop heart failure). Seminal data indicate an alteration of the extracellular matrix occurs with time in these hearts due to diffuse and abundant interstitial fibrosis. This results in an escalation in the stiffness of the local myocardial microenvironment. However, the influence of matrix stiffness in regulating the function of resident human stromal cells has not been reported. The objective of this study was to determine the impact of scaffold stiffness on the antigenic and functional profile of cardiac pericytes (CPs) isolated from patients with CHD. To this end, we have first manufactured gelatin nanofibrous scaffolds with varying degrees of stiffness using an in situ cross-linking electrospinning technique in a pure water solvent system. We assessed Young's modulus and performed a comprehensive physicochemical characterization of the scaffolds employing scanning electron microscopy and Fourier transform infrared spectroscopy. We next evaluated the changes induced by a different scaffold stiffness on CP morphology, antigenic profile, viability, proliferation, angiocrine activity, and induced differentiation. Results indicate that soft matrixes with a fiber diameter of ∼400 nm increase CP proliferation, secretion of angiopoietin 2, and F-actin stress fiber formation, without affecting the antigenic profile, viability, or differentiation. These data indicate for the first time that human CPs can be functionally influenced by slight changes in matrix stiffness. The study elucidates the importance of mechanical/morphological cues in modulating the behavior of stromal cells isolated from patients with CHD.

P1936Selective inhibition of the Mek1/2-Erk1/2 signalling pathway induces the differentiation of human cardiac pericyte-like cells into contractile vascular smooth muscle cells

Background

Arteriogenesis is key for tissue repair but whether myocardial stromal cells contribute to this phenomenon remains unknown.

Purpose

Investigate if cardiac pericytes are a druggable target for therapeutic arteriogenesis.

Methods and results

The localization of pericyte-like cells (PCs) was assessed in the human and murine heart by immunohistochemistry of typical antigenic markers. CD34+ PCs co-expressing NG2 and PDGFRβ but not endothelial cell (EC) or vascular smooth muscle cell (VSMC) antigens were identified in peri-arterial position in normal hearts. Interestingly, we also found rare PCs co-expressing αSMA in the peri-infarct myocardium, suggesting these cells could represent a transitory phenotype between PCs and VSMCs. Next, we isolated human cardiac PCs by immunosorting for CD31 and CD34 and established the purity of the isolated CD34+CD31- fraction by flow cytometry. Following culture expansion, cardiac PCs maintain the typical antigenic profile except for CD34. Moreover, we confirmed the PCs' ability to promote angiogenesis in-vitro. The withdrawal of EGF and bFGF from the culture media for 10 days induced the differentiation of PCs into mature VSMCs, as documented by a massive upregulation of contractile genes MYH11, CNN1 and ACTA2 (200-, 35- and 15-folds increase versus naïve PCs, p<0.01), which was followed by the induction of SM-MHC, Smoothelin B, αSMA, Calponin and SM22α proteins (p<0.05 versus PCs). In addition, PC-derived cells lost migratory capacity, secreted elastin, and responded to endothelin-1 in a contraction assay, thus phenocopying the behaviour of control coronary artery-derived VSMCs. We excluded contamination of the PC preparation by verifying similar phenomena occur in PCs expanded from single cell clonogeneic assays. Moreover, the process is partially reversible, with PC-derived VSMCs being able to reacquire some intermediate markers following EGF/bFGF re-challenge. ECs secrete EGF and bFGF, with this GF signalling being enhanced by hypoxia, suggesting ECs may control the PC phenotype in a paracrine fashion. Mechanistic studies revealed the Mek1/2-Erk1/2-Elk1 signalling is accountable for the transcriptional repression of VSMC genes in PCs. Accordingly, a selective Mek1/2 inhibitor (PD0325901) was able to switch the definitive VSMC phenotype of PCs maintained in full media. The drug prevented the phosphorylation of Erk1/2 and its downstream target Elk1. This likely relieves the complex SRF/MyocD and abolishes the transcriptional repression at the gene promoter.

Conclusions

Cardiac PCs have a VSMC potential which is under the inhibitory control of the Mek1/2-Erk1/2-Elk1 signalling. Mek1/2 inhibitors showed promises for the treatment of melanoma and solid tumours. A novel application of this class of compounds to improve arteriogenesis in myocardial ischemia is fascinating. The caveat about their potential cardiotoxicity could be less relevant with short duration treatments of myocardial ischemia.

Acknowledgement/Funding

British Heart Foundation Centre for Regenerative Medicine Award (II) - “Centre for Vascular Regeneration” (RM/17/3/33381)

Nerve growth factor gene therapy improves bone marrow sensory innervation and nociceptor-mediated stem cell release in a mouse model of type 1 diabetes with limb ischaemia

AIMS/HYPOTHESIS

Sensory neuropathy is common in people with diabetes; neuropathy can also affect the bone marrow of individuals with type 2 diabetes. However, no information exists on the state of bone marrow sensory innervation in type 1 diabetes. Sensory neurons are trophically dependent on nerve growth factor (NGF) for their survival. The aim of this investigation was twofold: (1) to determine if sensory neuropathy affects the bone marrow in a mouse model of type 1 diabetes, with consequences for stem cell liberation after tissue injury; and (2) to verify if a single systemic injection of the NGF gene exerts long-term beneficial effects on these phenomena.

METHODS

A mouse model of type 1 diabetes was generated in CD1 mice by administration of streptozotocin; vehicle was administered to non-diabetic control animals. Diabetic animals were randomised to receive systemic gene therapy with either human NGF or β-galactosidase. After 13 weeks, limb ischaemia was induced in both groups to study the recovery post injury. When the animals were killed, samples of tissue and peripheral blood were taken to assess stem cell mobilisation and homing, levels of substance P and muscle vascularisation. An in vitro cellular model was adopted to verify signalling downstream to human NGF and related neurotrophic or pro-apoptotic effects. Normally distributed variables were compared between groups using the unpaired Student's t test and non-normally distributed variables were assessed by the Wilcoxon-Mann-Whitney test. The Fisher's exact test was employed for categorical variables.

RESULTS

Immunohistochemistry indicated a 3.3-fold reduction in the number of substance P-positive nociceptive fibres in the bone marrow of type 1 diabetic mice (p < 0.001 vs non-diabetic). Moreover, diabetes abrogated the creation of a neurokinin gradient which, in non-diabetic mice, favoured the mobilisation and homing of bone-marrow-derived stem cells expressing the substance P receptor neurokinin 1 receptor (NK1R). Pre-emptive gene therapy with NGF prevented bone marrow denervation, contrasting with the inhibitory effect of diabetes on the mobilisation of NK1R-expressing stem cells, and restored blood flow recovery from limb ischaemia. In vitro hNGF induced neurite outgrowth and exerted anti-apoptotic actions on rat PC12 cells exposed to high glucose via activation of the canonical neurotrophic tyrosine kinase receptor type 1 (TrkA) signalling pathway.

CONCLUSIONS/INTERPRETATION

This study shows, for the first time, the occurrence of sensory neuropathy in the bone marrow of type 1 diabetic mice, which translates into an altered modulation of substance P and depressed release of substance P-responsive stem cells following ischaemia. NGF therapy improves bone marrow sensory innervation, with benefits for healing on the occurrence of peripheral ischaemia. Nociceptors may represent a new target for the treatment of ischaemic complications in diabetes.

Transplantation of Allogeneic Pericytes Improves Myocardial Vascularization and Reduces Interstitial Fibrosis in a Swine Model of Reperfused Acute Myocardial Infarction

BACKGROUND

Transplantation of adventitial pericytes (APCs) promotes cardiac repair in murine models of myocardial infarction. The aim of present study was to confirm the benefit of APC therapy in a large animal model.

METHODS AND RESULTS

We performed a blind, randomized, placebo-controlled APC therapy trial in a swine model of reperfused myocardial infarction. A first study used human APCs (hAPCs) from patients undergoing coronary artery bypass graft surgery. A second study used allogeneic swine APCs (sAPCs). Primary end points were (1) ejection fraction as assessed by cardiac magnetic resonance imaging and (2) myocardial vascularization and fibrosis as determined by immunohistochemistry. Transplantation of hAPCs reduced fibrosis but failed to improve the other efficacy end points. Incompatibility of the xenogeneic model was suggested by the occurrence of a cytotoxic response following in vitro challenge of hAPCs with swine spleen lymphocytes and the failure to retrieve hAPCs in transplanted hearts. We next considered sAPCs as an alternative. Flow cytometry, immunocytochemistry, and functional/cytotoxic assays indicate that sAPCs are a surrogate of hAPCs. Transplantation of allogeneic sAPCs benefited capillary density and fibrosis but did not improve cardiac magnetic resonance imaging indices of contractility. Transplanted cells were detected in the border zone.

CONCLUSIONS

Immunologic barriers limit the applicability of a xenogeneic swine model to assess hAPC efficacy. On the other hand, we newly show that transplantation of allogeneic sAPCs is feasible, safe, and immunologically acceptable. The approach induces proangiogenic and antifibrotic benefits, though these effects were not enough to result in functional improvements.

The adipokine leptin modulates adventitial pericyte functions by autocrine and paracrine signalling

Transplantation of adventitial pericytes (APCs) improves recovery from tissue ischemia in preclinical animal models by still unknown mechanisms. This study investigates the role of the adipokine leptin (LEP) in the regulation of human APC biological functions. Transcriptomic analysis of APCs showed components of the LEP signalling pathway are modulated by hypoxia. Kinetic studies indicate cultured APCs release high amounts of immunoreactive LEP following exposure to hypoxia, continuing upon return to normoxia. Secreted LEP activates an autocrine/paracrine loop through binding to the LEP receptor (LEPR) and induction of STAT3 phosphorylation. Titration studies using recombinant LEP and siRNA knockdown of LEP or LEPR demonstrate the adipokine exerts important regulatory roles in APC growth, survival, migration and promotion of endothelial network formation. Heterogeneity in LEP expression and secretion may influence the reparative proficiency of APC therapy. Accordingly, the levels of LEP secretion predict the microvascular outcome of APCs transplantation in a mouse limb ischemia model. Moreover, we found that the expression of the Lepr gene is upregulated on resident vascular cells from murine ischemic muscles, thus providing a permissive milieu to transplanted LEP-expressing APCs. Results highlight a new mechanism responsible for APC adaptation to hypoxia and instrumental to vascular repair.

Effects of very-low-calorie diet on body composition, metabolic state, and genes expression: a randomized double-blind placebo-controlled trial

OBJECTIVE

Very low-calorie diets (VLCDs, < 800 kcal day-1) and Ketogenic diet (KD) are generally used as part of integrated intervention, medical monitoring and a program of lifestyle modification, to improve a multitude of clinical states. The effect of three different very low calories KD (VLCKD), with (VLCKD1) or without (VLCKD2,3) synthetic amino acid replacement of the 50% protein intake, were analyzed after weight loss.

PATIENTS AND METHODS

The clinical study used a cross-over randomized double-blind placebo-controlled trial. Obese subjects, who were eligible for the study, were randomly (R) divided into three groups: one intervention group (IG) and two control groups (CG1 and CG2). We comprehensively analyzed body composition, serum metabolites, superoxide dismutase (SOD1), nuclear factor kappa-light-chain-enhancer of activated B cells (NfKB), Chemokine (C-C Motif) Ligand 2 (CCL2) gene expression.

RESULTS

After VLDKDs a significant decreased in BMI was observed. TBF (kg) significantly decrease after VLCKD1 and VLCKD3. After VLCKD2, a reduction of waist circumference (p = 0.02), FM L2-L5 (p < 0.05) was observed. After VLCKD1 reduction of IMAT (p = 0.00), LDL-C (p = 0.00) and HDL-C (p = 0.00) were observed. No significant changes of GH, ESR, and fibrinogen were highlighted. CRP (p = 0.02) reduced significantly after VLCKD3. Significant modulation of SOD1 expression (p = 0.009), CRP and decrease of glucose levels (p = 0.03) were obtained after VLCKD3.

CONCLUSIONS

This is the first study that analyzes comprehensively body composition, metabolic profile, and inflammation and oxidative stress genes expression after VLCKD. Our results show the efficacy of VLCKD with synthetic aminoacidic protein replacement, for the reduction of cardiovascular risk, without the development of sarcopenia and activation of inflammatory and oxidative processes.

Perivascular cells and tissue engineering: Current applications and untapped potential

The recent development of tissue engineering provides exciting new perspectives for the replacement of failing organs and the repair of damaged tissues. Perivascular cells, including vascular smooth muscle cells, pericytes and other tissue specific populations residing around blood vessels, have been isolated from many organs and are known to participate to the in situ repair process and angiogenesis. Their potential has been harnessed for cell therapy of numerous pathologies; however, in this Review we will discuss the potential of perivascular cells in the development of tissue engineering solutions for healthcare. We will examine their application in the engineering of vascular grafts, cardiac patches and bone substitutes as well as other tissue engineering applications and we will focus on their extensive use in the vascularization of engineered constructs. Additionally, we will discuss the emerging potential of human pericytes for the development of efficient, vascularized and non-immunogenic engineered constructs.

Discovering cardiac pericyte biology: From physiopathological mechanisms to potential therapeutic applications in ischemic heart disease

Microvascular pericytes and the more recently discovered adventitial pericyte-like progenitor cells are a subpopulation of vascular stem cells closely associated with small and large blood vessels respectively. These populations of perivascular cells are remarkably abundant in the heart. Pericytes control important physiological processes such as angiogenesis, blood flow and vascular permeability. In the heart, this pleiotropic activity makes pericytes extremely interesting for applications in regenerative medicine. On the other hand, dysfunction of pericytes could participate in the pathogenesis of cardiovascular disease, such as arterial hypertension, fibro-calcific cardiovascular remodeling, myocardial edema and post-ischemic coronary no-reflow. On a therapeutic standpoint, preclinical studies in small animal models of myocardial infarction have demonstrated the healing potential of pericytes transplantation, which has been ascribed to direct vascular incorporation and paracrine pro-angiogenic and anti-apoptotic activities. These promising findings open the door to the clinical use of pericytes for the treatment of cardiovascular diseases.

Ex vivo molecular rejuvenation improves the therapeutic activity of senescent human cardiac stem cells in a mouse model of myocardial infarction

Cardiac stem cells (CSC) from explanted decompensated hearts (E-CSC) are, with respect to those obtained from healthy donors (D-CSC), senescent and functionally impaired. We aimed to identify alterations in signaling pathways that are associated with CSC senescence. Additionally, we investigated if pharmacological modulation of altered pathways can reduce CSC senescence in vitro and enhance their reparative ability in vivo. Measurement of secreted factors showed that E-CSC release larger amounts of proinflammatory cytokine IL1β compared with D-CSC. Using blocking antibodies, we verified that IL1β hampers the paracrine protective action of E-CSC on cardiomyocyte viability. IL1β acts intracranially inducing IKKβ signaling, a mechanism that via nuclear factor-κB upregulates the expression of IL1β itself. Moreover, E-CSC show reduced levels of AMP protein kinase (AMPK) activating phosphorylation. This latter event, together with enhanced IKKβ signaling, increases TORC1 activity, thereby impairing the autophagic flux and inhibiting the phosphorylation of Akt and cAMP response element-binding protein. The combined use of rapamycin and resveratrol enhanced AMPK, thereby restoring downstream signaling and reducing IL1β secretion. These molecular corrections reduced E-CSC senescence, re-establishing their protective activity on cardiomyocytes. Moreover ex vivo treatment with rapamycin and resveratrol improved E-CSC capacity to induce cardiac repair upon injection in the mouse infarcted heart, leading to reduced cardiomyocyte senescence and apoptosis and increased abundance of endogenous c-Kit(+) CSC in the peri-infarct area. Molecular rejuvenation of patient-derived CSC by short pharmacologic conditioning boosts their in vivo reparative abilities. This approach might prove useful for refinement of CSC-based therapies.

Stem cell therapy and tissue engineering for correction of congenital heart disease

This review article reports on the new field of stem cell therapy and tissue engineering and its potential on the management of congenital heart disease. To date, stem cell therapy has mainly focused on treatment of ischemic heart disease and heart failure, with initial indication of safety and mild-to-moderate efficacy. Preclinical studies and initial clinical trials suggest that the approach could be uniquely suited for the correction of congenital defects of the heart. The basic concept is to create living material made by cellularized grafts that, once implanted into the heart, grows and remodels in parallel with the recipient organ. This would make a substantial improvement in current clinical management, which often requires repeated surgical corrections for failure of implanted grafts. Different types of stem cells have been considered and the identification of specific cardiac stem cells within the heterogeneous population of mesenchymal and stromal cells offers opportunities for de novo cardiomyogenesis. In addition, endothelial cells and vascular progenitors, including cells with pericyte characteristics, may be necessary to generate efficiently perfused grafts. The implementation of current surgical grafts by stem cell engineering could address the unmet clinical needs of patients with congenital heart defects.

Expansion and characterization of neonatal cardiac pericytes provides a novel cellular option for tissue engineering in congenital heart disease

Background

Living grafts produced by combining autologous heart-resident stem/progenitor cells and tissue engineering could provide a new therapeutic option for definitive correction of congenital heart disease. The aim of the study was to investigate the antigenic profile, expansion/differentiation capacity, paracrine activity, and pro-angiogenic potential of cardiac pericytes and to assess their engrafting capacity in clinically certified prosthetic grafts.

Methods and Results

CD34^pos cells, negative for the endothelial markers CD31 and CD146, were identified by immunohistochemistry in cardiac leftovers from infants and children undergoing palliative repair of congenital cardiac defects. Following isolation by immunomagnetic bead-sorting and culture on plastic in EGM-2 medium supplemented with growth factors and serum, CD34^pos/CD31^neg cells gave rise to a clonogenic, highly proliferative (>20 million at P5), spindle-shape cell population. The following populations were shown to expresses pericyte/mesenchymal and stemness markers. After exposure to differentiation media, the expanded cardiac pericytes acquired markers of vascular smooth muscle cells, but failed to differentiate into endothelial cells or cardiomyocytes. However, in Matrigel, cardiac pericytes form networks and enhance the network capacity of endothelial cells. Moreover, they produce collagen-1 and release chemo-attractants that stimulate the migration of c-Kit^pos cardiac stem cells. Cardiac pericytes were then seeded onto clinically approved xenograft scaffolds and cultured in a bioreactor. After 3 weeks, fluorescent microscopy showed that cardiac pericytes had penetrated into and colonized the graft.

Conclusions

These findings open new avenues for cellular functionalization of prosthetic grafts to be applied in reconstructive surgery of congenital heart disease.

Migration towards SDF-1 selects angiogenin-expressing bone marrow monocytes endowed with cardiac reparative activity in patients with previous myocardial infarction

Introduction

Chemokine-directed migration is crucial for homing of regenerative cells to the infarcted heart and correlates with outcomes of cell therapy trials. Hence, transplantation of chemokine-responsive bone marrow cells may be ideal for treatment of myocardial ischemia. To verify the therapeutic activity of bone marrow mononuclear cells (BM-MNCs) selected by in vitro migration towards the chemokine stromal cell-derived factor-1 (SDF-1) in a mouse model of myocardial infarction (MI), we used BM-MNCs from patients with previous large MI recruited in the TransACT-1&2 cell therapy trials.

Methods

Unfractioned BM-MNCs, SDF-1-responsive, and SDF-1-nonresponsive BM-MNCs isolated by patients recruited in the TransACT-1&2 cell therapy trials were tested in Matrigel assay to evaluate angiogenic potential. Secretome and antigenic profile were characterized by flow cytometry. Angiogenin expression was measured by RT-PCR. Cells groups were also intramyocardially injected in an in vivo model of MI (8-week-old immune deficient CD1-FOXN1^nu/nu mice). Echocardiography and hemodynamic measurements were performed before and at 14 days post-MI. Arterioles and capillaries density, infiltration of inflammatory cells, interstitial fibrosis, and cardiomyocyte proliferation and apoptosis were assessed by immunohistochemistry.

Results

In vitro migration enriched for monocytes, while CD34⁺ and CD133⁺ cells and T lymphocytes remained mainly confined in the non-migrated fraction. Unfractioned total BM-MNCs promoted angiogenesis on Matrigel more efficiently than migrated or non-migrated cells. In mice with induced MI, intramyocardial injection of unfractionated or migrated BM-MNCs was more effective in preserving cardiac contractility and pressure indexes than vehicle or non-migrated BM-MNCs. Moreover, unfractioned BM-MNCs enhanced neovascularization, whereas the migrated fraction was unique in reducing the infarct size and interstitial fibrosis. In vitro studies on isolated cardiomyocytes suggest participation of angiogenin, a secreted ribonuclease that inhibits protein translation under stress conditions, in promotion of cardiomyocyte survival by migrated BM-MNCs.

Conclusions

Transplantation of bone marrow cells helps post-MI healing through distinct actions on vascular cells and cardiomyocytes. In addition, the SDF-1-responsive fraction is enriched with angiogenin-expressing monocytes, which may improve cardiac recovery through activation of cardiomyocyte response to stress. Identification of factors linking migratory and therapeutic outcomes could help refine regenerative approaches.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0028-y) contains supplementary material, which is available to authorized users.

Combined intramyocardial delivery of human pericytes and cardiac stem cells additively improves the healing of mouse infarcted hearts through stimulation of vascular and muscular repair

RATIONALE

Optimization of cell therapy for cardiac repair may require the association of different cell populations with complementary activities.

OBJECTIVE

Compare the reparative potential of saphenous vein-derived pericytes (SVPs) with that of cardiac stem cells (CSCs) in a model of myocardial infarction, and investigate whether combined cell transplantation provides further improvements.

METHODS AND RESULTS

SVPs and CSCs were isolated from vein leftovers of coronary artery bypass graft surgery and discarded atrial specimens of transplanted hearts, respectively. Single or dual cell therapy (300 000 cells of each type per heart) was tested in infarcted SCID (severe combined immunodeficiency)-Beige mice. SVPs and CSCs alone improved cardiac contractility as assessed by echocardiography at 14 days post myocardial infarction. The effect was maintained, although attenuated at 42 days. At histological level, SVPs and CSCs similarly inhibited infarct size and interstitial fibrosis, SVPs were superior in inducing angiogenesis and CSCs in promoting cardiomyocyte proliferation and recruitment of endogenous stem cells. The combination of cells additively reduced the infarct size and promoted vascular proliferation and arteriogenesis, but did not surpass single therapies with regard to contractility indexes. SVPs and CSCs secrete similar amounts of hepatocyte growth factor, vascular endothelial growth factor, fibroblast growth factor, stem cell factor, and stromal cell-derived factor-1, whereas SVPs release higher quantities of angiopoietins and microRNA-132. Coculture of the 2 cell populations results in competitive as well as enhancing paracrine activities. In particular, the release of stromal cell-derived factor-1 was synergistically augmented along with downregulation of stromal cell-derived factor-1-degrading enzyme dipeptidyl peptidase 4.

CONCLUSIONS

Combinatory therapy with SVPs and CSCs may complementarily help the repair of infarcted hearts.

Epigenetic profile of human adventitial progenitor cells correlates with therapeutic outcomes in a mouse model of limb ischemia

OBJECTIVE

We investigated the association between the functional, epigenetic, and expressional profile of human adventitial progenitor cells (APCs) and therapeutic activity in a model of limb ischemia.

APPROACH AND RESULTS

Antigenic and functional features were analyzed throughout passaging in 15 saphenous vein (SV)-derived APC lines, of which 10 from SV leftovers of coronary artery bypass graft surgery and 5 from varicose SV removal. Moreover, 5 SV-APC lines were transplanted (8×10(5) cells, IM) in mice with limb ischemia. Blood flow and capillary and arteriole density were correlated with functional characteristics and DNA methylation/expressional markers of transplanted cells. We report successful expansion of tested lines, which reached the therapeutic target of 30 to 50 million cells in ≈10 weeks. Typical antigenic profile, viability, and migratory and proangiogenic activities were conserved through passaging, with low levels of replicative senescence. In vivo, SV-APC transplantation improved blood flow recovery and revascularization of ischemic limbs. Whole genome screening showed an association between DNA methylation at the promoter or gene body level and microvascular density and to a lesser extent with blood flow recovery. Expressional studies highlighted the implication of an angiogenic network centered on the vascular endothelial growth factor receptor as a predictor of microvascular outcomes. FLT-1 gene silencing in SV-APCs remarkably reduced their ability to form tubes in vitro and support tube formation by human umbilical vein endothelial cells, thus confirming the importance of this signaling in SV-APC angiogenic function.

CONCLUSIONS

DNA methylation landscape illustrates different therapeutic activities of human APCs. Epigenetic screening may help identify determinants of therapeutic vasculogenesis in ischemic disease.

Antihypertensive and neuroprotective effects of catestatin in spontaneously hypertensive rats: interaction with GABAergic transmission in amygdala and brainstem

The chromogranin A-derived peptide catestatin (CST) exerts sympathoexcitatory and hypertensive effects when microinjected into the rostral ventrolateral medulla (RVLM: excitatory output); it exhibits sympathoinhibitory and antihypertensive effects when microinjected into the caudal ventrolateral medulla (CVLM: inhibitory output) of vagotomized normotensive rats. Here, continuous infusion of CST into the central amygdalar nucleus (CeA) of spontaneously hypertensive rats (SHRs) for 15 days resulted in a marked decrease of blood pressure (BP) in 6-month- (by 37 mm Hg) and 9-month- (by 65 mm Hg)old rats. Whole-cell patch-clamp recordings on pyramidal CeA neurons revealed that CST increased both spontaneous inhibitory postsynaptic current (sIPSC) amplitude plus frequency, along with reductions of sIPSC rise time and decay time. Inhibition of GABAA receptors (GABAARs) by bicuculline completely abolished CST-induced sIPSC, corroborating that CST signals occur through this major neuroreceptor complex. Hypertension is a major risk factor for cerebrovascular diseases, leading to vascular dementia and neurodegeneration. We found a marked neurodegeneration in the amygdala and brainstem of 9-month-old SHRs, while CST and the GABAAR agonist Muscimol provided significant neuroprotection. Enhanced phosphorylation of Akt and ERK accounted for these neuroprotective effects through anti-inflammatory and anti-apoptotic activities. Overall our results point to CST exerting potent antihypertensive and neuroprotective effects plausibly via a GABAergic output, which constitute a novel therapeutic measure to correct defects in blood flow control in disorders such as stroke and Alzheimer's disease.

Boosting the pentose phosphate pathway restores cardiac progenitor cell availability in diabetes

AIMS

Diabetes impinges upon mechanisms of cardiovascular repair. However, the biochemical adaptation of cardiac stem cells to sustained hyperglycaemia remains largely unknown. Here, we investigate the molecular targets of high glucose-induced damage in cardiac progenitor cells (CPCs) from murine and human hearts and attempt safeguarding CPC viability and function through reactivation of the pentose phosphate pathway.

METHODS AND RESULTS

Type-1 diabetes was induced by streptozotocin. CPC abundance was determined by flow cytometry. Proliferating CPCs were identified in situ by immunostaining for the proliferation marker Ki67. Diabetic hearts showed marked reduction in CPC abundance and proliferation when compared with controls. Moreover, Sca-1(pos) CPCs isolated from hearts of diabetic mice displayed reduced activity of key enzymes of the pentose phosphate pathway, glucose-6-phosphate dehydrogenase (G6PD), and transketolase, increased levels of superoxide and advanced glucose end-products (AGE), and inhibition of the Akt/Pim-1/Bcl-2 signalling pathway. Similarly, culture of murine CPCs or human CD105(pos) progenitor cells in high glucose inhibits the pentose phosphate and pro-survival signalling pathways, leading to the activation of apoptosis. In vivo and in vitro supplementation with benfotiamine reactivates the pentose phosphate pathway and rescues CPC availability and function. This benefit is abrogated by either G6PD silencing by small interfering RNA (siRNA) or Akt inhibition by dominant-negative Akt.

CONCLUSION

We provide new evidence of the negative impact of diabetes and high glucose on mechanisms controlling CPC redox state and survival. Boosting the pentose phosphate pathway might represent a novel mechanistic target for protection of CPC integrity.

Global remodeling of the vascular stem cell niche in bone marrow of diabetic patients: implication of the microRNA-155/FOXO3a signaling pathway

RATIONALE

The impact of diabetes mellitus on bone marrow (BM) structure is incompletely understood.

OBJECTIVE

Investigate the effect of type-2 diabetes mellitus (T2DM) on BM microvascular and hematopoietic cell composition in patients without vascular complications.

METHODS AND RESULTS

Bone samples were obtained from T2DM patients and nondiabetic controls (C) during hip replacement surgery and from T2DM patients undergoing amputation for critical limb ischemia. BM composition was assessed by histomorphometry, immunostaining, and flow cytometry. Expressional studies were performed on CD34(pos) immunosorted BM progenitor cells (PCs). Diabetes mellitus causes a reduction of hematopoietic tissue, fat deposition, and microvascular rarefaction, especially when associated with critical limb ischemia. Immunohistochemistry documented increased apoptosis and reduced abundance of CD34(pos)-PCs in diabetic groups. Likewise, flow cytometry showed scarcity of BM PCs in T2DM and T2DM+critical limb ischemia compared with C, but similar levels of mature hematopoietic cells. Activation of apoptosis in CD34(pos)-PCs was associated with upregulation and nuclear localization of the proapoptotic factor FOXO3a and induction of FOXO3a targets, p21 and p27(kip1). Moreover, microRNA-155, which regulates cell survival through inhibition of FOXO3a, was downregulated in diabetic CD34(pos)-PCs and inversely correlated with FOXO3a levels. The effect of diabetes mellitus on anatomic and molecular end points was confirmed when considering background covariates. Furthermore, exposure of healthy CD34(pos)-PCs to high glucose reproduced the transcriptional changes induced by diabetes mellitus, with this effect being reversed by forced expression of microRNA-155.

CONCLUSIONS

We provide new anatomic and molecular evidence for the damaging effect of diabetes mellitus on human BM, comprising microvascular rarefaction and shortage of PCs attributable to activation of proapoptotic pathway.