Ex Vivo Perfusion Culture of Large Blood Vessels in a 3D Printed Bioreactor

Vascular disease forms the basis of most cardiovascular diseases (CVDs), which remain the primary cause of mortality and morbidity worldwide. Efficacious surgical and pharmacological interventions to prevent and treat vascular disease are urgently needed. In part, the shortage of translational models limits the understanding of the cellular and molecular processes involved in vascular disease. Ex vivo perfusion culture bioreactors provide an ideal platform for the study of large animal vessels (including humans) in a controlled dynamic environment, combining the ease of in vitro culture and the complexity of the live tissue. Most bioreactors are, however, custom manufactured and therefore difficult to adopt, limiting the reproducibility of the results. This paper presents a 3D printed system that can be easily produced and applied in any biological lab, and provides a detailed protocol for its setup, enabling users' operation. This innovative and reproducible ex vivo perfusion culture system enables the culture of blood vessels for up to 7 days in physiological conditions. We expect that adopting a standardized perfusion bioreactor will support a better understanding of physiological and pathological processes in large animal blood vessels and accelerate the discovery of new therapeutics.

Enhancing Techniques for Determining Inflammatory Edema Formation and Neutrophil Accumulation in Murine Skin

Inflammatory edema formation and polymorphonuclear leukocyte (neutrophil) accumulation are common components of cutaneous vascular inflammation, and their assessment is a powerful investigative and drug development tool but typically requires independent cohorts of animals to assess each. We have established the use of a mathematical formula to estimate the ellipsoidal-shaped volume of the edematous wheal or bleb after intradermal injections of substances in mice pretreated intravenously with Evans blue dye (which binds to plasma albumin) to act as an edema marker. Whereas previous extraction of Evans blue dye with formamide is suitable for all strains of mice, we report this quicker and more reliable assessment of edema volume in situ. This therefore allows neutrophil accumulation to be assessed from the same mouse using the myeloperoxidase assay. Importantly, we examined the influence of Evans blue dye on the spectrometry readout at the wavelength at which myeloperoxidase activity is measured. The results indicate that it is feasible to quantify edema formation and neutrophil accumulation in the same mouse skin site. Thus, we show techniques that can assess edema formation and neutrophil accumulation at the same site in the same mouse, allowing paired measurements and reducing the total use of mice by 50%.

Porcine Organotypic Epicardial Slice Protocol: A Tool for the Study of Epicardium in Cardiovascular Research

The epicardium has recently gained interest in the cardiovascular field due to its capacity to support heart regeneration after ischemic injury. Models to study the epicardium of large animals in vitro are limited and mainly based on epicardial cell isolation/differentiation from stem cells, followed by 2D cells culture. In this method paper, we describe the procedure to obtain and culture 3D organotypic heart slices presenting an intact epicardium, as a novel model to study the epicardial physiology and activation. Epicardial slices are obtained from porcine hearts using a high-precision vibratome and retain a healthy epicardial layer embedded in its native extracellular environment and connected with other cardiac cells (cardiomyocytes, fibroblasts, vascular cells etc.). Epicardial slices can be cultured for 72 h, providing an ideal model for studying the epicardium physiology or perform pharmacological interventions/gene therapy approaches. We also report on methods to assesses the viability and composition of the epicardial slices, and evaluate their architecture in 3D through tissue decoloration. Finally, we present a potential application for a nanomaterial-based gene transfer method for tracking of epicardial cells within the slice. Crucially, given the similarity in morphology and physiology of porcine heart with its human counterpart, our system provides a platform for translational research while providing a clinically relevant and ethical alternative to the use of small animals in this type of research.

3D Printed Bioreactor Enabling the Pulsatile Culture of Native and Angioplastied Large Arteries

Routine interventions such as balloon angioplasty, result in vascular activation and remodeling, often requiring re-intervention. 2D in vitro models and small animal experiments have enabled the discovery of important mechanisms involved in this process, however the clinical translation is often underwhelming. There is a critical need for an ex vivo model representative of the human vascular physiology and encompassing the complexity of the vascular wall and the physical forces regulating its function. Vascular bioreactors for ex vivo culture of large vessels are viable alternatives, but their custom-made design and insufficient characterization often hinders the reproducibility of the experiments. The objective of the study was to design and validate a novel 3D printed cost-efficient and versatile perfusion system, capable of sustaining the viability and functionality of large porcine arteries for 7 days and enabling early post-injury evaluations. MultiJet Fusion 3D printing was used to engineer the EasyFlow insert, converting a conventional 50 ml centrifuge tube into a mini bioreactor. Porcine carotid arteries either left untreated or injured with an angioplasty balloon, were cultured under pulsatile flow for up to 7 days. Pressure, heart rate, medium viscosity and shear conditions were adjusted to resemble arterial in vivo hemodynamics. Tissue viability, cell activation and matrix remodeling were analyzed by immunohistochemistry, and vascular function was monitored by duplex ultrasound. Culture conditions in the EasyFlow bioreactor preserved endothelial coverage and smooth muscle organization and extracellular matrix structure in the vessel wall, as compared to static culture. Injured arteries presented hallmarks of early remodeling, such as intimal denudation, smooth muscle cell disarray and media/adventitia activation in flow culture. Duplex ultrasound confirmed continuous pulsatile blood flow conditions, dose-dependent vasodilator response to nitroglycerin in untreated vessels and impaired dilator response in angioplastied vessels. The scope of this work is to validate a low-cost, robust and reproducible system to explore the culture of native and injured large arteries under pulsatile flow. While the study of vascular pathology is beyond the scope of the present paper, our system enables future investigations and provides a platform to test novel therapies and devices ex vivo, in a patient relevant system.

Mechanical Strain Induces Transcriptomic Reprogramming of Saphenous Vein Progenitors

Intimal hyperplasia is the leading cause of graft failure in aortocoronary bypass grafts performed using human saphenous vein (SV). The long-term consequences of the altered pulsatile stress on the cells that populate the vein wall remains elusive, particularly the effects on saphenous vein progenitors (SVPs), cells resident in the vein adventitia with a relatively wide differentiation capacity. In the present study, we performed global transcriptomic profiling of SVPs undergoing uniaxial cyclic strain in vitro. This type of mechanical stimulation is indeed involved in the pathology of the SV. Results showed a consistent stretch-dependent gene regulation in cyclically strained SVPs vs. controls, especially at 72 h. We also observed a robust mechanically related overexpression of Adhesion Molecule with Ig Like Domain 2 (AMIGO2), a cell surface type I transmembrane protein involved in cell adhesion. The overexpression of AMIGO2 in stretched SVPs was associated with the activation of the transforming growth factor β pathway and modulation of intercellular signaling, cell-cell, and cell-matrix interactions. Moreover, the increased number of cells expressing AMIGO2 detected in porcine SV adventitia using an in vivo arterialization model confirms the upregulation of AMIGO2 protein by the arterial-like environment. These results show that mechanical stress promotes SVPs' molecular phenotypic switching and increases their responsiveness to extracellular environment alterations, thus prompting the targeting of new molecular effectors to improve the outcome of bypass graft procedure.

P40 COVID 19: A NEW RISK FACTOR IN CARDIAC SURGERY?

Introduction

Since the beginning of the actual pandemia, several patients with positive anamnesis for Covid 19, are undergoing a cardiac operation. Aim of the study is to analize if the Covid 19 past infection may impact on cardiac surgery outcome.

Method

All the patients with a history of Covid 19 positivity, who underwent a cardiac operation at the Clinica Mediterranea in Naples from the 1st of february 2021 to the 31st dicember 2021, have been included in the study. For those patients we evaluated the basal respiratory condition, with a chest Xray or CT scan, a pneumology consult and a spirometry if required. Postoperative outcome has been evaluated analizing ventilation time, intensive care and postoperative lenght of stay, acute renal failure, acute espiratory failure, postoperative complications and death.

Results

Thirtheen patients on 358 had a positive anamnesis for Covid19, but a negative swab at the admission. The mean time from the infection has been 5.1 +/– months, 5 patients have had poor or no symptoms, while the remnants moderate or sever ones with evidence of interstitial pneumonia, one patient had developed extrapulmonary complications (valvular thrombosis).

Epicardial slices: an innovative 3D organotypic model to study epicardial cell physiology and activation

The epicardium constitutes an untapped reservoir for cardiac regeneration. Upon heart injury, the adult epicardium re-activates, leading to epithelial-to-mesenchymal transition (EMT), migration, and differentiation. While interesting mechanistic and therapeutic findings arose from lower vertebrates and rodent models, the introduction of an experimental system representative of large mammals would undoubtedly facilitate translational advancements. Here, we apply innovative protocols to obtain living 3D organotypic epicardial slices from porcine hearts, encompassing the epicardial/myocardial interface. In culture, our slices preserve the in vivo architecture and functionality, presenting a continuous epicardium overlaying a healthy and connected myocardium. Upon thymosin β4 treatment of the slices, the epicardial cells become activated, upregulating epicardial and EMT genes, resulting in epicardial cell mobilization and differentiation into epicardial-derived mesenchymal cells. Our 3D organotypic model enables to investigate the reparative potential of the adult epicardium, offering an advanced tool to explore ex vivo the complex 3D interactions occurring within the native heart environment.

Novel perfusion ex-vivo culture system enables physiological and pathological studies on porcine arteries

Introduction

Routine cardiovascular interventions such as cardiac bypass, balloon angioplasty and stenting provoke vascular activation and remodelling often leading to rehospitalization and further interventions. Conventional in vitro models fail to account for the complex vascular environment essential for vascular tissue fitness.

Purpose

Our research aims to culture whole porcine arteries in using a novel cost efficient and versatile perfusion system (EasyFlow) and identify the contribution of adventitial progenitors to post-injury remodelling.

Methods

EasyFlow insert was 3D printed to convert a conventional 50 ml centrifuge tube into a mini bioreactor. Porcine arteries were excised and cultured under constant pulsatile flow for up to 7 days. Injury was performed by balloon catheter at day 0. Tissues were evaluated by doppler ultrasound, immunofluorescence and confocal imaging and PCR, at different timepoints.

Results

The EasyFlow adaptor takes advantage of 50 ml centrifuge tubes isolating reaction space from the environment and reducing the culture volume. The adaptability of the design facilitates the incubation of vessels of different size and origin while the self-contained perfusion allows parallel cultures and minimal media consumption. EasyFlow perfusion culture of porcine arteries preserves the endothelial coverage and the smooth muscle cell organisation, as compared to static culture.

Gene expression analysis and immunofluorescence indicated an increased expression of platelet-derived growth factor receptor beta (PDGFRb) and a decrease in smooth muscle actin (SMA) in the static culture, compared to the perfusion. Furthermore, static culture showed an increased cellular activation in adventitia (proliferating cell nuclear antigen expression), as compared to perfused tissues. Balloon injury followed by flow culture recapitulated the early hallmarks of vascular remodelling, including intimal denudation indicated by loss of platelet endothelial cell adhesion molecule signal, smooth muscle cell disarray shown by loss of actin stress fibre organisation and activation in the media, as supported by confocal microscope and gene expression analysis, accompanied by significant morphological changes based on ultrasound imaging.

Conclusion

This work lay the basis for future investigations into the pathological remodelling of blood vessels, by providing a robust and controlled culture system for the maintenance of porcine blood vessels in culture.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): University of Surrey En-Face Staining of Arterial Lumen

Hypoxia-induced miR-210 modulates inflammatory response and fibrosis upon acute peripheral ischemia

Introduction

We previously demonstrated in mouse models of peripheral and heart ischemia that miR-210 is necessary and sufficient to stimulate blood perfusion recovery, as well as arteriolar and capillary density increase following ischemic damage.

Aim

To clarify the role of inflammatory cells in miR-210-induced angiogenesis.

Methods and results

In a mouse model of acute limb ischemia, miR-210 loss-of-function was obtained by administration of complementary anti-miR-210 LNA oligonucleotides (anti-210), while doxycycline-inducible miR-210 transgenic mice (Tg210) were used for gain-of-function experiments. Transcriptomic and gene ontology analysis in ischemic gastrocnemius muscles upon miR-210 blocking displayed an enrichment of categories related not only to angiogenesis, but also to inflammation, suggesting that miR-210 decrease prompted a pro-inflammatory and anti-regenerative response. Accordingly, immunofluorescence staining of ischemic muscles of anti-210 treated mice, showed an increased presence of granulocytes (Scr = 28±7, anti-210 = 108±17 cells/mm2, p<0.001), T and B lymphocytes (Scr = 32±8 SE, anti-210 = 112±19 cells/mm2, p<0.003; Scr = 45±10, anti-210 = 103±14 cells/mm2, p<0.006, respectively) and macrophages (Scr = 17±1, anti-210 = 27±4 cells/mm2; p<0.03), with a higher M1/M2 macrophage ratio (Scr = 0.6±0.1, anti-210 = 1.7±0.3; p<0.02). Conversely macrophages (WT = 17±2, Tg210 = 5±1 cells/mm2, p<0.003) and M1/M2 ratio (WT = 1.0±0.1, Tg210 = 0.3±0.1, p<0.02) were decreased in ischemic TG-210 mice. To clarify the role of inflammatory cells in miR-210-induced angiogenesis, bone-marrow (BM) transplantation experiments were performed. Tg210 mice transplanted with WT BM cells (BM-wt/R-Tg210), compared with WT mice transplanted with Tg210 BM (BM-Tg210/R-wt) showed increased blood perfusion (vascularity ratio: BM-wt/R-Tg210 = 0.8±0.1, BM-Tg210/R-wt = 0.6±0.1; p<0.01) and capillary density after ischemia (BM-wt/R-Tg210 = 497±41, BM-Tg210/R-wt = 212±32 cap./mm2; P<0.00001). Thus, miR-210 expression in the muscle and not in the BM-derived cells was crucial for miR-210-stimulated angiogenesis. Interestingly, BM-wt/R-Tg210 mice also showed increased fibrotic areas (sirius red staining: BM-wt/R-Tg210 = 12±2, BM-Tg210/R-wt = 22±3 A.U.; p<0.01), characterized by α-SMA+, vimentin+ and collagen V+ stainings. Fibrotic regions were enriched in cells double-positive for both CD206/α-SMA and CD45/α-SMA, as well as in phospho-Smad3+ cells, suggesting the activation of the TGFβ pathway. In vitro experiments showed higher expression of α-SMA and collagens in TG-210 BM-derived macrophages compared to WT, both in the presence and in the absence of TGFβ (α-SMA: w/o TGFβ 2.3±1.4 fold increase p<0.004; TGFβ+ 11.3±2 fold increase p<0.003).

Conclusions

Collectively, these data show that a miR-210 enriched milieu was sufficient to improve angiogenesis after ischemia. Moreover, a context-dependent regulation by miR-210 of the inflammatory response and of fibrosis were identified.

Funding Acknowledgement

Type of funding source: Public hospital(s). Main funding source(s): Italian Ministry of health: Ricerca Corrente and 5X1000

A Critical Role for Perivascular Cells in Amplifying Vascular Leakage Induced by Dengue Virus Nonstructural Protein 1

Dengue is the most prevalent arthropod-borne viral disease affecting humans, with severe dengue typified by potentially fatal microvascular leakage and hypovolemic shock. Blood vessels of the microvasculature are composed of a tubular structure of endothelial cells ensheathed by perivascular cells (pericytes). Pericytes support endothelial cell barrier formation and maintenance through paracrine and contact-mediated signaling and are critical to microvascular integrity. Pericyte dysfunction has been linked to vascular leakage in noncommunicable pathologies such as diabetic retinopathy but has never been linked to infection-related vascular leakage. Dengue vascular leakage has been shown to result in part from the direct action of the secreted dengue virus (DENV) nonstructural protein NS1 on endothelial cells. Using primary human vascular cells, we show here that NS1 also causes pericyte dysfunction and that NS1-induced endothelial hyperpermeability is more pronounced in the presence of pericytes. Notably, NS1 specifically disrupted the ability of pericytes to support endothelial cell function in a three-dimensional (3D) microvascular assay, with no effect on pericyte viability or physiology. These effects are mediated at least in part through contact-independent paracrine signals involved in endothelial barrier maintenance by pericytes. We therefore identify a role for pericytes in amplifying NS1-induced microvascular hyperpermeability in severe dengue and thus show that pericytes can play a critical role in the etiology of an infectious vascular leakage syndrome. These findings open new avenues of research for the development of drugs and diagnostic assays for combating infection-induced vascular leakage, such as severe dengue.IMPORTANCE The World Health Organization considers dengue one of the top 10 global public health problems. There is no specific antiviral therapy to treat dengue virus and no way of predicting which patients will develop potentially fatal severe dengue, typified by vascular leakage and circulatory shock. We show here that perivascular cells (pericytes) amplify the vascular leakage-inducing effects of the dengue viral protein NS1 through contact-independent signaling to endothelial cells. While pericytes are known to contribute to noncommunicable vascular leakage, this is the first time these cells have been implicated in the vascular effects of an infectious disease. Our findings could pave the way for new therapies and diagnostics to combat dengue and potentially other infectious vascular leakage syndromes.

MicroRNA-21/PDCD4 Proapoptotic Signaling From Circulating CD34+ Cells to Vascular Endothelial Cells: A Potential Contributor to Adverse Cardiovascular Outcomes in Patients With Critical Limb Ischemia

OBJECTIVE

In patients with type 2 diabetes (T2D) and critical limb ischemia (CLI), migration of circulating CD34⁺ cells predicted cardiovascular mortality at 18 months after revascularization. This study aimed to provide long-term validation and mechanistic understanding of the biomarker.

RESEARCH DESIGN AND METHODS

The association between CD34⁺ cell migration and cardiovascular mortality was reassessed at 6 years after revascularization. In a new series of T2D-CLI and control subjects, immuno-sorted bone marrow CD34⁺ cells were profiled for miRNA expression and assessed for apoptosis and angiogenesis activity. The differentially regulated miRNA-21 and its proapoptotic target, PDCD4, were titrated to verify their contribution in transferring damaging signals from CD34⁺ cells to endothelial cells.

RESULTS

Multivariable regression analysis confirmed that CD34⁺ cell migration forecasts long-term cardiovascular mortality. CD34⁺ cells from T2D-CLI patients were more apoptotic and less proangiogenic than those from control subjects and featured miRNA-21 downregulation, modulation of several long noncoding RNAs acting as miRNA-21 sponges, and upregulation of the miRNA-21 proapoptotic target PDCD4. Silencing miR-21 in control CD34⁺ cells phenocopied the T2D-CLI cell behavior. In coculture, T2D-CLI CD34⁺ cells imprinted naive endothelial cells, increasing apoptosis, reducing network formation, and modulating the TUG1 sponge/miRNA-21/PDCD4 axis. Silencing PDCD4 or scavenging reactive oxygen species protected endothelial cells from the negative influence of T2D-CLI CD34⁺ cells.

CONCLUSIONS

Migration of CD34⁺ cells predicts long-term cardiovascular mortality in T2D-CLI patients. An altered paracrine signaling conveys antiangiogenic and proapoptotic features from CD34⁺ cells to the endothelium. This damaging interaction may increase the risk for life-threatening complications.

P5400CD34+ cells predict long-term cardiovascular mortality in people with critical limb ischemia: a possible pathogenic role of the microRNA-21/PDCD4 axis

Background/Introduction

The annual rate of restenosis, amputation, and death of subjects with type 2 diabetes (T2DM) and critical limb ischemia (CLI) is very high even after successful revascularization. We have recently demonstrated that the in-vitro migratory ability of proangiogenic bone marrow (BM)-derived CD45dimKDR+CXCR4+ CD34+ cells predicts cardiovascular mortality at 18 months after percutaneous angioplasty (PTA) in people with T2DM and CLI.

Purpose

To verify the predictor at a longer follow-up time and to investigate the underpinning mechanism.

Methods

We analyzed the rate of cardiovascular mortality in the previously studied cohort of 119 subjects at a six-year follow-up. In addition, we compared apoptosis and angiogenic capability of MAC-sorted BM-CD34+ cells in a newly-recruited series of patients with T2DM and CLI and control nondiabetic subjects (CTRL). Following the screening of a spectrum of microRNA (miR) using PCR-based Exiqon technology, we validated the modulated miRs in BM-CD34+ cells from 6 new donors per group. Finally, we focused on miR-21 and its inhibitory targets, by assessing the effect of miR-21 modulation of functional outcomes, including apoptosis (caspase assay and Annexin V positive staining) and the induction of in-vitro endothelial networking on Matrigel.

Results

Multivariable regression model analysis confirmed that CD34+ cell migration forecasts cardiovascular mortality after revascularization. BM-CD34+ cells isolated from T2DM-CLI donors undergo apoptosis in a higher percentage and are less proangiogenic in-vitro than cells from CTRL. Of the 56 microRNAs commonly expressed in CD34+ cells from the two studied groups, 6 miRs were differentially expressed. Biological validation confirmed a significant down-modulation of miR-21 in CD34+ cells from T2DM-CLI patients. The expression of the miR-21 inhibitory target, PDCD4, a regulator of apoptosis, was increased in CD34+ cells from T2DM-CLI patients compared to CTRL (1.6±0.6 vs. 74.4±14.9 average±SE 2ddCt via PCR). Silencing miR-21 in CD34+ cells from CTRL phenocopied the T2DM-CLI behavior, resulting in significantly increased apoptosis and inhibition of EC networking. Likewise, exposure of endothelial cells to patient-derived CD34+ CCM induced apoptosis and reduced the network formation ability on Matrigel, with these functional liabilities being associated with miR-21 inhibition and PDCD4 upregulation.

Conclusions

Migratory activity of CD34+ cells predicts cardiovascular mortality at 6 years follow-up after PTA in subjects with T2DM and CLI. Complicated T2DM is associated with a specific miR signature in BM CD34+ cells which could negatively impact on vascular cell survival and angiogenic capacity, thereby possibly contributing to adverse cardiovascular outcomes. The miR-21/ PDCD4 duo may represent a therapeutic target to rescue diabetes-associated complications.

Acknowledgement/Funding

British Heart Foundation grant RG/13/17/30545, Cariplo Foundation (code: 2016-0922)

P4488Organotypic culture of the epicardium: a new tool for cardiovascular research

Background

The epicardium, the most external layer of the heart, is composed of a layer of epithelial cells and underlying connective tissue. Following myocardial infarction, epicardial cells are activated and provide a source of paracrine factors and progenitor cells. In the border zone of the ischaemic tissue, the activated epicardial cells support cardiac and vascular regeneration by releasing pro-angiogenic and pro-survival factors, and by differentiating towards multiple cell lineages. During this process, activated epicardial cells migrate to the site of injury where they contribute to both post-ischemic remodelling and fibrosis. There is limited knowledge of the cellular and molecular regulation of these processes in large animals and humans, in part due to the lack of robust and representative models.

Purpose

In this project, we developed an ex vivo 3D organotypic model derived from porcine hearts, amenable to culture, which enables structural, molecular and cellular studies of the epicardium.

Methods

Thin epicardial/cardiac tissue slices (EpCardio-TS) were obtained by using a vibratome to cut the first layer of tissue from the epicardial side of porcine heart cubes. Slices were cultured for up to 72h in a bioreactor that uses a 3D printed chamber connected to a control system that allows maintenance and adjustment of culture conditions, and ensures continuous media flow. Local intracellular delivery of fluorescent quantum-dots (Qdots) was performed using nanoneedle chips to track epicardial cells, whilst cell fate is visualised in 3D by performing immunofluorescence on decolourised slices.

Results

Intact EpCardio-TS obtained from porcine heart included a viable epicardium, expressing typical epicardial markers (wt-1, mesothelin, uroplakin), and an electrically active myocardium. Live/dead staining showed epicardial (67.8±16.2%, N=5) and myocardial (40.8±28.6%, N=3) viability, and TUNEL assay confirmed low levels of apoptosis (6.3±5.1% of wt-1+ epicardial cells N=1). Moreover, the presence of proliferating epicardial cells (PCNA+), the increase in wt-1+ cells, and the increase in epicardial gene expression (Tbx18 and TCF21) suggested that cells maintain their progenitor phenotype and undergo activation in culture. Nanoinjection of fluorescent Qdots to EpCardio-TS localized them to the wt-1+ cells on the slice surface, presenting a strategy to mark the epicardial layer. This, combined with the successful decolourisation of the slices, provides an in vitro platform to track the role of epicardial cells in cardiac remodelling and fibrosis.

Conclusions

EpCardio-TS represents a robust ex vivo model merging the complexity of a 3D organotypic culture with the simplicity of the in vitro culture. EpCardio-TS are amenable to culture and cell tracking, and can therefore find application in toxicology and gene therapy screening for the modulation of epicardial interactions with myocardial and non-myocardial cells of the heart.

Correction to: Bone marrow pericyte dysfunction in individuals with type 2 diabetes

Unfortunately, three errors were made in the conversion of HbA_1c to per cent values.

Bone marrow pericyte dysfunction in individuals with type 2 diabetes

AIMS/HYPOTHESIS

Previous studies have shown that diabetes mellitus destabilises the integrity of the microvasculature in different organs by damaging the interaction between pericytes and endothelial cells. In bone marrow, pericytes exert trophic functions on endothelial cells and haematopoietic cells through paracrine mechanisms. However, whether bone marrow pericytes are a target of diabetes-induced damage remains unknown. Here, we investigated whether type 2 diabetes can affect the abundance and function of bone marrow pericytes.

METHODS

We conducted an observational clinical study comparing the abundance and molecular/functional characteristics of CD146⁺ pericytes isolated from the bone marrow of 25 individuals without diabetes and 14 individuals with uncomplicated type 2 diabetes, referring to our Musculoskeletal Research Unit for hip reconstructive surgery.

RESULTS

Immunohistochemistry revealed that diabetes causes capillary rarefaction and compression of arteriole size in bone marrow, without changing CD146⁺ pericyte counts. These data were confirmed by flow cytometry on freshly isolated bone marrow cells. We then performed an extensive functional and molecular characterisation of immunosorted CD146⁺ pericytes. Type 2 diabetes caused a reduction in pericyte proliferation, viability, migration and capacity to support in vitro angiogenesis, while inducing apoptosis. AKT is a key regulator of the above functions and its phosphorylation state is reportedly reduced in the bone marrow endothelium of individuals with diabetes. Surprisingly, we could not find a difference in AKT phosphorylation (at either Ser473 or Thr308) in bone marrow pericytes from individuals with and without diabetes. Nonetheless, the angiocrine signalling reportedly associated with AKT was found to be significantly downregulated, with lower levels of fibroblast growth factor-2 (FGF2) and C-X-C motif chemokine ligand 12 (CXCL12), and activation of the angiogenesis inhibitor angiopoietin 2 (ANGPT2). Transfection with the adenoviral vector carrying the coding sequence for constitutively active myristoylated AKT rescued functional defects and angiocrine signalling in bone marrow pericytes from diabetic individuals. Furthermore, an ANGPT2 blocking antibody restored the capacity of pericytes to promote endothelial networking.

CONCLUSIONS/INTERPRETATION

This is the first demonstration of pericyte dysfunction in bone marrow of people with type 2 diabetes. An altered angiocrine signalling from pericytes may participate in bone marrow microvascular remodelling in individuals with diabetes.

MCP-1 Feedback Loop Between Adipocytes and Mesenchymal Stromal Cells Causes Fat Accumulation and Contributes to Hematopoietic Stem Cell Rarefaction in the Bone Marrow of Patients With Diabetes

Fat accumulates in bone marrow (BM) of patients with diabetes. In this study, we investigated the mechanisms and consequences of this phenomenon. BM mesenchymal stromal cells (BM-MSCs) from patients with type 2 diabetes (T2D) constitutively express adipogenic markers and robustly differentiate into adipocytes (ADs) upon in vitro induction as compared with BM-MSCs from subjects without diabetes. Moreover, BM-ADs from subjects with T2D (T2D BM-ADs) paracrinally stimulate a transcriptional adipogenic program in BM-MSCs. Antagonism of MCP-1, a chemokine pivotally expressed in T2D BM-ADs, prevented the T2D BM-AD secretome from converting BM-MSCs into ADs. Mechanistic validation of human data was next performed in an obese T2D mouse model. Systemic antagonism of MCP-1 improved metabolic control, reduced BM fat, and increased osteocyte density. It also indirectly re-established the abundance of long-term versus short-term hematopoietic stem cells. We reveal a diabetic feedback loop in which 1) BM-MSCs are constitutively inclined to make ADs, and 2) mature BM-ADs, via secreted MCP-1, relentlessly fuel BM-MSC determination into new fat. Pharmacological inhibition of MCP-1 signaling can contrast this vicious cycle, restoring, at least in part, the balance between adipogenesis and hematopoiesis in BM from subjects with T2D.

Concise Review: The Regenerative Journey of Pericytes Toward Clinical Translation

Coronary artery disease (CAD) is the single leading cause of death worldwide. Advances in treatment and management have significantly improved patient outcomes. On the other hand, although mortality rates have decreased, more people are left with sequelae that require additional treatment and hospitalization. Moreover, patients with severe nonrevascularizable CAD remain with only the option of heart transplantation, which is limited by the shortage of suitable donors. In recent years, cell-based regenerative therapy has emerged as a possible alternative treatment, with several regenerative medicinal products already in the clinical phase of development and others emerging as competitive preclinical solutions. Recent evidence indicates that pericytes, the mural cells of blood microvessels, represent a promising therapeutic candidate. Pericytes are abundant in the human body, play an active role in angiogenesis, vessel stabilization and blood flow regulation, and possess the capacity to differentiate into multiple cells of the mesenchymal lineage. Moreover, early studies suggest a robustness to hypoxic insult, making them uniquely equipped to withstand the ischemic microenvironment. This review summarizes the rationale behind pericyte-based cell therapy and the progress that has been made toward its clinical application. We present the different sources of pericytes and the case for harvesting them from tissue leftovers of cardiovascular surgery. We also discuss the healing potential of pericytes in preclinical animal models of myocardial ischemia (MI) and current practices to upgrade the production protocol for translation to the clinic. Standardization of these procedures is of utmost importance, as lack of uniformity in cell manufacturing may influence clinical outcome. Stem Cells 2018;36:1295-1310.

Overexpression of miR-210 and its significance in ischemic tissue damage

Hypoxia-induced miR-210 displays a pro-survival, cytoprotective and pro-angiogenic role in several in vitro systems. In vivo, we previously found that miR-210 inhibition increases ischemic damage. Here we describe the generation of a versatile transgenic mouse model allowing the evaluation of miR-210 therapeutic potential in ischemic cardiovascular diseases. We generated a Tet-On miR-210 transgenic mouse strain (TG-210) by targeted transgenesis in the ROSA26 locus. To functionally validate miR-210 transgenic mice, hindlimb ischemia was induced by femoral artery dissection. Blood perfusion was evaluated by power Doppler while tissue damage and inflammation were assessed by histological evaluation. We found that miR-210 levels were rapidly increased in TG-210 mice upon doxycycline administration. miR-210 overexpression was maintained over time and remained within physiological levels in multiple tissues. When hindlimb ischemia was induced, miR-210 overexpression protected from both muscular and vascular ischemic damage, decreased inflammatory cells density and allowed to maintain a better calf perfusion. In conclusion, we generated and functionally validated a miR-210 transgenic mouse model. Albeit validated in the context of a specific cardiovascular ischemic disease, miR-210 transgenic mice may also represent a useful model to assess the function of miR-210 in other physio-pathological conditions.

Activation of the Pro-Oxidant PKCβII-p66Shc Signaling Pathway Contributes to Pericyte Dysfunction in Skeletal Muscles of Patients With Diabetes With Critical Limb Ischemia

Critical limb ischemia (CLI), foot ulcers, former amputation, and impaired regeneration are independent risk factors for limb amputation in subjects with diabetes. The present work investigates whether and by which mechanism diabetes negatively impacts on functional properties of muscular pericytes (MPs), which are resident stem cells committed to reparative angiomyogenesis. We obtained muscle biopsy samples from patients with diabetes who were undergoing major limb amputation and control subjects. Diabetic muscles collected at the rim of normal tissue surrounding the plane of dissection showed myofiber degeneration, fat deposition, and reduction of MP vascular coverage. Diabetic MPs (D-MPs) display ultrastructural alterations, a differentiation bias toward adipogenesis at the detriment of myogenesis and an inhibitory activity on angiogenesis. Furthermore, they have an imbalanced redox state, with downregulation of the antioxidant enzymes superoxide dismutase 1 and catalase, and activation of the pro-oxidant protein kinase C isoform β-II (PKCβII)-dependent p66^Shc signaling pathway. A reactive oxygen species scavenger or, even more effectively, clinically approved PKCβII inhibitors restore D-MP angiomyogenic activity. Inhibition of the PKCβII-dependent p66^Shc signaling pathway could represent a novel therapeutic approach for the promotion of muscle repair in individuals with diabetes.

Contribution of pericyte paracrine regulation of the endothelium to angiogenesis

During physiological development and after a stressor event, vascular cells communicate with each other to evoke new vessel formation-a process known as angiogenesis. This communication occurs via direct contact and via paracrine release of proteins and nucleic acids, both in a free form or encapsulated into micro-vesicles. In diseases with an altered angiogenic response, such as cancer and diabetic vascular complications, it becomes of paramount importance to tune the cell communication process. Endothelial cell growth and migration are essential processes for new vessel formation, and pericytes, together with some classes of circulating monocytes, are important endothelial regulators. The interaction between pericytes and the endothelium is facilitated by their anatomical apposition, which involves endothelial cells and pericytes sharing the same basement membrane. However, the role of pericytes is not fully understood. The characteristics and the function of tissue-specific pericytesis are the focus of this review. Factors involved in the cross-talk between these cell types and the opportunities afforded by micro-RNA and micro-vesicle techniques are discussed. Targeting these mechanisms in pathological conditions, in which the vessel response is altered, is considered in relation to identification of new therapies for restoring the blood flow.

Sensory neuropathy hampers nociception-mediated bone marrow stem cell release in mice and patients with diabetes

AIMS/HYPOTHESIS

Upon tissue injury, peripheral sensory neurons release nociceptive factors (e.g. substance P [SP]), which exert local and systemic actions including the recruitment of bone marrow (BM)-derived haematopoietic stem and progenitor cells (HSPCs) endowed with paracrine pro-angiogenic properties. We herein explore whether diabetic neuropathy interferes with these phenomena.

METHODS

We first investigated the presence of sensory neuropathy in the BM of patients with type 2 diabetes by immunohistochemistry and morphometry analyses of nerve size and density and assessment of SP release by ELISA. We next analysed the association of sensory neuropathy with altered HSPC release under ischaemia or following direct stimulation with granulocyte colony-stimulating factor (G-CSF). BM and circulating HSPCs expressing the neurokinin 1 receptor (NK1R), which is the main SP receptor, were measured by flow cytometry. We finally assessed whether an altered modulation of SP secretion interferes with the mobilisation and homing of NK1R-HSPCs in a mouse model of type 2 diabetes after limb ischaemia (LI).

RESULTS

Nociceptive fibres were reduced in the BM of patients and mice with type 2 diabetes. Patients with neuropathy showed a remarkable reduction in NK1R-HSPC mobilisation under ischaemia or upon G-CSF stimulation. Following LI, diabetic mice manifested an altered SP gradient between BM, peripheral blood and limb muscles, accompanied by a depressed recruitment of NK1R-HSPCs to the ischaemic site.

CONCLUSIONS/INTERPRETATION

Sensory neuropathy translates into defective liberation and homing of reparative HSPCs. Nociceptors may represent a new target for treatment of diabetic complications.

Early results of synchronous carotid endarterectomy and off-pump coronary revascularization

AIM

This study reports results of synchronous carotid endarterectomy (CEA) and off-pump coronary artery bypass grafting (CABG) in further support of the hypothesis that carotid and coronary artery revascularization can be safely performed in most patients.

METHODS

The series includes 74 consecutive patients underwent synchronous CEA and off-pump CABG (group A) compared with 50 patients undergoing synchronous CEA and on-pump CABG (group B). Primary endpoint of this study are death, stroke, perioperative myocardial infarction and need for repeated revascularization within 30 days of the procedures. The secondary endpoint includes local and systemic complications.

RESULTS

No stroke was observed in group A. Ipsilateral minor stroke occurred in two patients of group B (4%). Two deaths within 30 days were observed in group A (2.7%) compared with 4 deaths in group B (8%). Combined stroke/death rate at 30 days was 2.7% in group A compared with 12% in group B (P< 0.05). No significant differences in myocardial infarction, local and systemic complications were observed.

CONCLUSION

Synchronous CEA and off-pump CABG may reduce the high surgical risk of patients who actually require combined carotid and coronary revascularization. This opinion has to be substantiated by larger studies and randomized trial.

Cardiac protection by volatile anaesthetics

BACKGROUND AND OBJECTIVES

To evaluate the effects of total intravenous anaesthesia vs. volatile anaesthesia on cardiac troponin release in coronary artery bypass grafting with cardiopulmonary bypass, we performed a multicentre randomized controlled study to compare postoperative cardiac troponin release in patients receiving two different anaesthesia plans.

METHODS

We randomly assigned 75 patients to propofol (intravenous anaesthetic) and 75 patients to desflurane (volatile anaesthetic) in addition to an opiate-based anaesthesia for coronary artery bypass grafting. Peak postoperative troponin I release was measured as a marker of myocardial necrosis.

RESULTS

There was a significant (P < 0.001) difference in the postoperative median (25th-75th percentiles) peak of troponin I in patients receiving propofol 5,5 (2,3-9,5) ng dL(-1) when compared to patients receiving desflurane 2,5 (1,1-5,3) ng dL(-1). The median (interquartile) troponin I area under the curve analysis confirmed the results: 68 (30.5-104.8) vs. 36.3 (17.9-86.6) h ng dL(-1) (P = 0.002). Patients receiving volatile anaesthetics had reduced need for postoperative inotropic support (24/75, 32.0% vs. 31/75, 41.3%, P = 0.04), and tends toward a reduction in number of Q-wave myocardial infarction, time on mechanical ventilation, intensive care unit and overall hospital stay.

CONCLUSIONS

Myocardial damage measured by cardiac troponin release could be reduced by volatile anaesthetics in coronary artery bypass surgery.

Septal dissection and rupture evolved as an inferobasal pseudoaneurysm

We report two cases of postinfarction dissecting hematoma of the interventricular septum with restrictive ventricular septal defect that evolved as an inferobasal pseudoaneurysm. The difficult anatomical pattern was assessed by two-dimensional (2-D) echocardiography with Doppler and color analysis, left ventriculography and perioperative transoesophageal echo. Because the patient had no signs of heart failure, the surgical repair was successfully delayed until the dissecting tissue became fibrotic. Problems of diagnosis, decision making and surgical management are discussed.

Left ventricular mass reduction after aortic valve replacement: homografts, stentless and stented valves

BACKGROUND

We studied the effect of four different types of prosthetic aortic valves on time course and extent of regression of left ventricular hypertrophy after aortic valve replacement for aortic stenosis.

METHODS

Four groups of 10 patients each were randomly assigned to receive: (1) aortic homograft preserved in antibiotic solution at 4 degrees C, (2) Toronto stentless porcine valve, (3) Medtronic Freestyle stentless valve, or (4) Medtronic Intact aortic valve. The left ventricular mass index, effective orifice area index, and peak and mean transaortic gradients were measured by Doppler echocardiography before the operation and 8 months postoperatively.

RESULTS

The hemodynamic performance indices were much better for the homograft and stentless valves than for the stented one. The absolute left ventricular mass index reduction was greater in the homograft group compared with the Intact (p = 0.0004) and Toronto (p = 0.007) groups. The extent of percent left ventricular mass index reduction was greater only in the homograft group versus Intact group (p = 0.005). The multilinear regression analysis showed that the only predictors of a larger percentage of left ventricular mass index reduction were the homograft type, a higher valve size index, and a higher preoperative left ventricular mass index.

CONCLUSIONS

When a stentless or homograft aortic valve was used instead of a stented valve to replace a stenotic aortic valve there was more complete or at least faster regression of left ventricular hypertrophy. The hemodynamic performance of stentless porcine valves was similar to that of aortic homografts, nevertheless the aortic homografts preserved in antibiotic solution offered a faster regression of left ventricular hypertrophy during the same period of time.

[Aortic valve replacement in patients over 70: a Doppler echocardiographic study]

Aortic valve disease is known to be the most frequent valvular disease in the elderly and aortic valve replacement is often the best therapeutic strategy. Hemodynamic performance of prostheses is critical in this subset of patients to ensure an optimal quality of life. Moreover, old patients with small aortic ostia are getting more and more common in clinical practice, making often necessary to implant small prostheses. If a significant pressure drop is not achieved, hypertrophy persists and left ventricular function may not improve. Such conditions have not yet been extensively studied in the elderly. The aim of this study was firstly to assess echocardiographically the performance of aortic prosthetic heart valves in old patients (> or = 70 years) and compare the results obtained in patients with prostheses of different type and size, and secondly to evaluate the postoperative changes in left ventricular hypertrophy and function in a subset of patients with isolated or prevalent aortic stenosis. One hundred fifty-one patients were initially considered; global mortality was 9.3% at 20 +/- 12 months from intervention. In the 75 patients with a postoperative echocardiogram, transprosthetic gradient was 27 +/- 12 (max) and 15.1 +/- 6.6 (mean) mmHg. Mean functional prosthetic area (FPA) was 1.5 +/- 0.5 cm2. No statistically significant differences could be demonstrated between mechanical and biological prostheses. Three groups were identified, according to prosthetic size (Group 1: diameter < 23 mm, Group 2: diameter 23 mm, Group 3: diameter > 23 mm). Among groups, max and mean gradients as well as FPA were found to be significantly different. Respectively max gradient was 33.2 +/- 13, 26 +/- 11, 20.2 +/- 7.2 mmHg (p < 0.05), mean gradient was 17.2 +/- 6.1, 15.4 +/- 7.6, 11.7 +/- 4.3 mmHg (p < 0.01) and FPA was 1.2 +/- 0.3, 1.5 +/- 0.3, 1.8 +/- 0.7 cm2 (p < 0.05 between Group 1 and Group 3). In a subgroup of 31 patients with isolated or prevalent aortic stenosis, a significant interventricular septal thickness reduction was found postoperatively (14.3 +/- 2.3 vs 12.6 +/- 8.0 mm, p < 0.001). Posterior wall thickness decreased similarly, but to a lesser extent; left ventricular diameters and myocardial mass also significantly decreased (left ventricular mass: 186 +/- 45 vs 146 +/- 38 g/m2, p < 0.001). When prosthetic size was considered, septal thickness reduction was more evident in Group 1 and Group 2 (p < 0.05 and p < 0.01). On the contrary, a significant improvement in left ventricular diameters was observed only in Group 3 (p < 0.05). Left ventricular mass decreased significantly in Group 2 and Group 3 (p < 0.01 and p < 0.05). Such improvements could be demonstrated only in those patients (79%) who showed at least a 50% reduction in the transvalvular gradient. In this subset, left ventricular function also significantly improved (fractional shortening: 29 +/- 0.7 vs 33 +/- 0.7%, p < 0.02). In conclusion, aortic valve replacement in the elderly is a safe and effective therapeutic strategy. In patients with small aortic prostheses, the transvalvular gradient was found to be slightly but significantly higher as compared to that of larger prostheses. However, left ventricular function was good and similar in all subgroups. No significant differences were found between mechanical and biological prostheses. In old patients with isolated or prevalent aortic stenosis a significant reduction in left ventricular hypertrophy and mass is observed within 2 years from intervention. An increase in myocardial contractility can also be expected, if at least a 50% reduction in transvalvular gradient is obtained.

Posttraumatic left ventricular pseudoaneurysm due to intramyocardial dissecting hematoma

A left ventricular aneurysm can develop in patients sustaining blunt chest injury. This condition has been attributed to myocardial contusion or to a direct vascular lesion leading to myocardial necrosis. We report the case of a pseudoaneurysm resulting from myocardial dissection beginning from a small tear in the endocardial wall. Successful surgical exclusion of the pseudoaneurysm by endoaneurysmal patch closure of the communications between the aneurysm and the left ventricular cavity is described.

Left main coronary artery atresia: literature review and therapeutical considerations

OBJECTIVE

Left main coronary artery atresia is a rare coronary anomaly in which there is no left coronary ostium, the proximal left main trunk ends blindly, blood flows from the right coronary artery to the left via small collateral arteries and retrogradely in at least one of the left-sided arteries. Since published case reports are few and rather scattered, no comprehensive information about this uncommon anomaly is available.

METHODS

A through search for published cases of left main coronary atresia was performed in the major medical journals by electronic (MEDLINE and INTERNET) and hand-scanning.

RESULTS

The authors found 28 cases of left main atresia (including two from their own experience), 15 of which were pediatric; five of these cases had associated cardiac anomalies. While pediatric patients were usually overtly symptomatic early in their life (syncope, dyspnea, sudden death, failure to thrive, infarction, ventricular tachycardia), adult patients began showing symptoms (angina, dyspnea, sudden death) only at an advanced age; associated coronary atherosclerosis seemed to be uncommon, though (2/13 adult patients, 15%). We know of only one asymptomatic patient, a 76-year old lady who had died of unrelated causes; in her case left main atresia was an unforeseen autopsy finding. Four untreated patients had died suddenly; most of the others were highly symptomatic and required surgical therapy, usually as direct coronary artery revascularization via one or more saphenous vein or mammary artery grafts to the left-sided arteries; all revascularized patients were reported to be alive and well; in one pediatric case the left main coronary artery was reconstructed using an aortic wall baffle, with a good result. In contrast, the outcome of patients who did not receive revascularization has been poor.

CONCLUSION

In light of the favorable results obtained by surgical therapy, the authors endorse prompt coronary artery revascularization for all patients with left main coronary artery atresia.

[Structural and morphometric analysis of the internal mammary artery used in coronary bypass surgery]

The internal mammary artery is currently regarded as the optimal canal in coronary bypass surgery. Even if the motives for the excellent behaviour of this artery are still not fully clarified, the morphological and morphofunctional study of its wall can contribute to explain the clinical results obtained using this canal. In order to complete existing studies on this topic and to increase our knowledge of the structure of this artery, segments of internal mammary artery taken from patients undergoing coronary bypass surgery were analysed. Histological, immunohistochemical, histochemical and morphometrical tests were performed in these samples. The results of the tests underline the considerable complexity of the internal mammary artery whose walls appear to be rich in elastic fibres, divided into numerous lamellar structures concentric to the vasal lumen and without vasa vasorum in the tunica media given that this is adjacent to the tunica adventitia. Moreover, the marked presence of the NO-synthase enzyme, responsible for nitrogen monoxide synthesis, was observed in the endothelial layer and tunica media, as suggested by histochemical analysis. These data argue in favour of a structure able to resist the considerable hemodynamic stress to which the artery is subjected after bypass, a structure which is functionally well adapted to receive the majority of nutrition through its own lumen, and, lastly, a structure capable of self-regulation in response to the requirements made from time to time. These findings may further our understanding of the morphofunctional aspects of the internal mammary artery and may contribute to explaining the latter's relative immunity to atherosclerosis and, thus, its success in coronary bypass.

[Surgical revascularization of the myocardium for atresia of the left main coronary artery and atherosclerotic coronary disease]

The authors report a rare case of atresia of the left main coronary artery in an adult patient, symptomatic for effort angina. At coronarography, the left main coronary artery was not found; instead, the arteries of the left coronary tree were filled via a single collateral vessel arising from the ostium of the right coronary artery and ending in the trunk of the left anterior descending artery. All left arteries had very narrow calibres, almost hypoplastic, while the right coronary artery had a normal calibre. All the principal arteries had important stenoses. The patient underwent complete cardiac revascularization, and, sixteen months later, is free from angina. Rest and stress myocardial scintigraphy, control coronary angiography and Doppler analysis of internal mammary artery flow demonstrated normal myocardial perfusion, adequate blood flow through the grafts and good runoff in the native vessels. Hence, the authors conclude that such patients should be referred for coronary artery revascularization, since surgical results are good and the small calibre of the left coronary arteries is no contraindication.