Corrigendum: Robotic Cardiac Surgery in Europe: Status 2020.

[This corrects the article DOI: 10.3389/fcvm.2021.827515.].

Fibrin-based factor delivery for therapeutic angiogenesis: friend or foe?

Therapeutic angiogenesis aims at promoting the growth of blood vessels to restore perfusion in ischemic tissues or aid tissue regeneration. Vascular endothelial growth factor (VEGF) is the master regulator of angiogenesis in development, repair, and disease. However, exploiting VEGF for therapeutic purposes has been challenging and needs to take into account some key aspects of VEGF biology. In particular, the spatial localization of angiogenic signals within the extracellular matrix is crucial for physiological assembly and function of new blood vessels. Fibrin is the provisional matrix that is universally deposited immediately after injury and supports the initial steps of tissue regeneration. It provides therefore several ideal features as a substrate to promote therapeutic vascularization, especially through its ability to present growth factors in their physiological matrix-bound state and to modulate their availability for signaling. Here, we provide an overview of fibrin uses as a tissue-engineering scaffold material and as a tunable platform to finely control dose and duration of delivery of recombinant factors in therapeutic angiogenesis. However, in some cases, fibrin has also been associated with undesirable outcomes, namely the promotion of fibrosis and scar formation that actually prevent physiological tissue regeneration. Understanding the mechanisms that tip the balance between the pro- and anti-regenerative functions of fibrin will be the key to fully exploit its therapeutic potential.

Robotic Cardiac Surgery in Europe: Status 2020.

BACKGROUND: European surgeons were the first worldwide to use robotic techniques in cardiac surgery and major steps in procedure development were taken in Europe. After a hype in the early 2000s case numbers decreased but due to technological improvements renewed interest can be noted. We assessed the current activities and outcomes in robotically assisted cardiac surgery on the European continent. METHODS: Data were collected in an international anonymized registry of 26 European centers with a robotic cardiac surgery program. RESULTS: During a 4-year period (2016-2019), 2,563 procedures were carried out [30.0% female, 58.5 (15.4) years old, EuroSCORE II 1.56 (1.74)], including robotically assisted coronary bypass grafting (n = 1266, 49.4%), robotic mitral or tricuspid valve surgery (n = 945, 36.9%), isolated atrial septal defect closure (n = 225, 8.8%), left atrial myxoma resection (n = 54, 2.1%), and other procedures (n = 73, 2.8%). The number of procedures doubled during the study period (from n = 435 in 2016 to n = 923 in 2019). The mean cardiopulmonary bypass time in pump assisted cases was 148.6 (63.5) min and the myocardial ischemic time was 88.7 (46.1) min. Conversion to larger thoracic incisions was required in 56 cases (2.2%). Perioperative rates of revision for bleeding, stroke, and mortality were 56 (2.2%), 6 (0.2 %), and 27 (1.1%), respectively. Median postoperative hospital length of stay was 6.6 (6.6) days. CONCLUSION: Robotic cardiac surgery case numbers in Europe are growing fast, including a large spectrum of procedures. Conversion rates are low and clinical outcomes are favorable, indicating safe conduct of these high-tech minimally invasive procedures.

Fibrin hydrogels promote scar formation and prevent therapeutic angiogenesis in the heart.

Therapeutic angiogenesis is the delivery of factors to promote vascular growth and holds promise for the treatment of ischemic heart conditions. Recombinant protein delivery to the myocardium by factor-decorated fibrin matrices is an attractive approach, thanks to the ability to precisely control both dose and duration of the treatment, the use of a clinically approved material like fibrin, and the avoidance of genetic modification. Here, we investigated the feasibility of inducing therapeutic angiogenesis in the rat myocardium by a state-of-the-art fibrin-based delivery platform that we previously optimized. Engineered versions of murine vascular endothelial growth factor A (VEGF164 ) and platelet-derived growth factor BB (PDGF-BB) were fused with an octapeptide substrate of the transglutaminase coagulation factor fXIIIa (TG) to allow their covalent cross-linking into fibrin hydrogels and release by enzymatic cleavage. Hydrogels containing either 100 µg/mL TG-VEGF alone or in combination with 10 µg/mL TG-PDGF-BB or no factor were injected into rat myocardium. Surprisingly, vascular density was severely reduced in all conditions, both in and around the injection site, where large fibrotic scars were formed. Scar formation was not due to the presence of growth factors, adaptive immunity to human proteins, damage from injection, nor to mechanical trauma from the hydrogel stiffness or volume. Rather scar was induced directly by fibrin and persisted despite hydrogel degradation within 1 week. These results caution against the suitability of fibrin-based platforms for myocardial growth factor delivery, despite their efficacy in other tissues, like skeletal muscle. The underlying molecular mechanisms must be further investigated in order to identify rational targets to prevent this serious side effect.

Therapeutic vascularization in regenerative medicine.

Therapeutic angiogenesis, that is, the generation of new vessels by delivery of specific factors, is required both for rapid vascularization of tissue-engineered constructs and to treat ischemic conditions. Vascular endothelial growth factor (VEGF) is the master regulator of angiogenesis. However, uncontrolled expression can lead to aberrant vascular growth and vascular tumors (angiomas). Major challenges to fully exploit VEGF potency for therapy include the need to precisely control in vivo distribution of growth factor dose and duration of expression. In fact, the therapeutic window of VEGF delivery depends on its amount in the microenvironment around each producing cell rather than on the total dose, since VEGF remains tightly bound to extracellular matrix (ECM). On the other hand, short-term expression of less than about 4 weeks leads to unstable vessels, which promptly regress following cessation of the angiogenic stimulus. Here, we will briefly overview some key aspects of the biology of VEGF and angiogenesis and discuss their therapeutic implications with a particular focus on approaches using gene therapy, genetically modified progenitors, and ECM engineering with recombinant factors. Lastly, we will present recent insights into the mechanisms that regulate vessel stabilization and the switch between normal and aberrant vascular growth after VEGF delivery, to identify novel molecular targets that may improve both safety and efficacy of therapeutic angiogenesis.

Fifty years of coronary artery bypass grafting.

Coronary artery bypass grafting (CABG) remains the most common cardiac surgery performed today worldwide. The history of this procedure can be traced back for more than 100 years, and its development has been touched by several pioneers in the field of cardiac surgery, who have contributed with both their successes and failures. With ever increasing follow up and number of patients treated, thinking regarding optimal CABG technique evolves continually. This article reviews the history of CABG from its early experimental work to recent technological advances.

Myocardial infarction stabilization by cell-based expression of controlled Vascular Endothelial Growth Factor levels.

Vascular Endothelial Growth Factor (VEGF) can induce normal or aberrant angiogenesis depending on the amount secreted in the microenvironment around each cell. Towards a possible clinical translation, we developed a Fluorescence Activated Cell Sorting (FACS)-based technique to rapidly purify transduced progenitors that homogeneously express a desired specific VEGF level from heterogeneous primary populations. Here, we sought to induce safe and functional angiogenesis in ischaemic myocardium by cell-based expression of controlled VEGF levels. Human adipose stromal cells (ASC) were transduced with retroviral vectors and FACS purified to generate two populations producing similar total VEGF doses, but with different distributions: one with cells homogeneously producing a specific VEGF level (SPEC), and one with cells heterogeneously producing widespread VEGF levels (ALL), but with an average similar to that of the SPEC population. A total of 70 nude rats underwent myocardial infarction by coronary artery ligation and 2 weeks later VEGF-expressing or control cells, or saline were injected at the infarction border. Four weeks later, ventricular ejection fraction was significantly worsened with all treatments except for SPEC cells. Further, only SPEC cells significantly increased the density of homogeneously normal and mature microvascular networks. This was accompanied by a positive remodelling effect, with significantly reduced fibrosis in the infarcted area. We conclude that controlled homogeneous VEGF delivery by FACS-purified transduced ASC is a promising strategy to achieve safe and functional angiogenesis in myocardial ischaemia.

Robotic lymphadenectomy of an internal mammary lymph node metastasis.

A 58-year-old woman was diagnosed with a left-sided lone internal mammary swollen lymph node on a routine follow-up computer tomography, 42 months after a left mastectomy in the context of a ductal carcinoma grade III. The suspected metastasis was successfully removed in toto using a 3-port-da Vinci robotic procedure and the patient was discharged home without any complication on the third postoperative day. Robotically assisted oncological lymph node removal is safe, easily performed and economically affordable.

Case report: osteogenesis imperfecta, internal mammary artery graft & nitinol clips.

BACKGROUND: Osteogenesis imperfecta is a genetic disorder of connective tissue causing mostly left-sided heart valves and aortic root pathologies, but a coronary artery involvement reflecting an increased sensitivity to cardiovascular risk factors is also suspected in this patient population. CASE PRESENTATION: We report a 38-year-old patient with an osteogenesis imperfecta and a typical presentation of an acute myocardial infarction. The coronary angiogram showed a coronary 3-vessel disease. The patient underwent a bypass grafting surgery with the internal mammary artery. The sternum was closed using four nitinol clips and had totally stabilized at 4 months with excellent bone healing. CONCLUSIONS: With the successful clinical outcome in this patient severely affected by its osteogensis imperfecta, we underline the safe use of the LIMA, if precaution is taken towards the sternal bone, and its closure with nitinol clips.

Scaffold Composition Determines the Angiogenic Outcome of Cell-Based Vascular Endothelial Growth Factor Expression by Modulating Its Microenvironmental Distribution.

Delivery of genetically modified cells overexpressing Vascular Endothelial Growth Factor (VEGF) is a promising approach to induce therapeutic angiogenesis in ischemic tissues. The effect of the protein is strictly modulated by its interaction with the components of the extracellular matrix. Its therapeutic potential depends on a sustained but controlled release at the microenvironmental level in order to avoid the formation of abnormal blood vessels. In this study, it is hypothesized that the composition of the scaffold plays a key role in modulating the binding, hence the therapeutic effect, of the VEGF released by 3D-cell constructs. It is found that collagen sponges, which poorly bind VEGF, prevent the formation of localized hot spots of excessive concentration, therefore, precluding the development of aberrant angiogenesis despite uncontrolled expression by a genetically engineered population of adipose tissue-derived stromal cells. On the contrary, after seeding on VEGF-binding egg-white scaffolds, the same cell population caused aberrantly enlarged vascular structures after 14 d. Collagen-based engineered tissues also induced a safe and efficient angiogenesis in both the patch itself and the underlying myocardium in rat models. These findings open new perspectives on the control and the delivery of proangiogenic stimuli, and are fundamental for the vascularization of engineered tissues/organs.

Engineered mesenchymal cell-based patches as controlled VEGF delivery systems to induce extrinsic angiogenesis.

UNLABELLED: Therapeutic over-expression of Vascular Endothelial Growth Factor (VEGF) by transduced progenitors is a promising strategy to efficiently induce angiogenesis in ischemic tissues (e.g. limb muscle and myocardium), but tight control over the micro-environmental distribution of the dose is required to avoid induction of angioma-like tumors. Therapeutic VEGF release was achieved by purified transduced adipose mesenchymal stromal cells (ASC) that homogeneously produce specific VEGF levels, inducing only normal angiogenesis after injection in non-ischemic tissues. However, the therapeutic potential of this approach mostly in the cardiac field is limited by the poor cell survival and the restricted area of effect confined to the cell-injection site. The implantation of cells previously organized in vitro in 3D engineered tissues could overcome these issues. Here we hypothesized that collagen sponge-based construct (patch), generated by ASC expressing controlled VEGF levels, can function as delivery device to induce angiogenesis in surrounding areas (extrinsic vascularization). A 7-mm-thick acellular collagen scaffold (empty), sutured beneath the patch, provided a controlled and reproducible model to clearly investigate the ongoing angiogenesis in subcutaneous mice pockets. VEGF-expressing ASC significantly increased the capillary in-growth inside both the patch itself and the empty scaffold compared to naïve cells, leading to significantly improved survival of implanted cells. These data suggest that this strategy confers control (i) on angiogenesis efficacy and safety by means of ASC expressing therapeutic VEGF levels and (ii) over the treated area through the specific localization in an engineered collagen sponge-based patch. STATEMENT OF SIGNIFICANCE: Development of efficient pro-angiogenic therapies to restore the micro-vascularization in ischemic tissues is still an open issue. Although extensively investigated, the promising approach based on injections of progenitors transduced to over-express Vascular Endothelial Growth Factor (VEGF) has still several limitations: (i) need of a tight control over the microenvironmental VEGF dose to avoid angioma-like tumor growth; (ii) poor implanted cell survival; (iii) effect area restricted mainly to the injection sites. Here, we aimed to overcome these drawbacks by generating a novel cell-based controlled VEGF delivery device. In particular, transduced mesenchymal cells, purified to release a sustained, safe and efficient VEGF dose, were organized in three-dimensional engineered tissues to improve cell survival and provide a uniform vascularization throughout both the mm-thick implanted constructs themselves and the surrounding area.

Three dimensional multi-cellular muscle-like tissue engineering in perfusion-based bioreactors.

Conventional tissue engineering strategies often rely on the use of a single progenitor cell source to engineer in vitro biological models; however, multi-cellular environments can better resemble the complexity of native tissues. Previous described co-culture models used skeletal myoblasts, as parenchymal cell source, and mesenchymal or endothelial cells, as stromal component. Here, we propose instead the use of adipose tissue-derived stromal vascular fraction cells, which include both mesenchymal and endothelial cells, to better resemble the native stroma. Percentage of serum supplementation is one of the crucial parameters to steer skeletal myoblasts toward either proliferation (20%) or differentiation (5%) in two-dimensional culture conditions. On the contrary, three-dimensional (3D) skeletal myoblast culture often simply adopts the serum content used in monolayer, without taking into account the new cell environment. When considering 3D cultures of mm-thick engineered tissues, homogeneous and sufficient oxygen supply is paramount to avoid formation of necrotic cores. Perfusion-based bioreactor culture can significantly improve the oxygen access to the cells, enhancing the viability and the contractility of the engineered tissues. In this study, we first investigated the influence of different serum supplementations on the skeletal myoblast ability to proliferate and differentiate during 3D perfusion-based culture. We tested percentages of serum promoting monolayer skeletal myoblast-proliferation (20%) and differentiation (5%) and suitable for stromal cell culture (10%) with a view to identify the most suitable condition for the subsequent co-culture. The 10% serum medium composition resulted in the highest number of mature myotubes and construct functionality. Co-culture with stromal vascular fraction cells at 10% serum also supported the skeletal myoblast differentiation and maturation, hence providing a functional engineered 3D muscle model that resembles the native multi-cellular environment.

Osteogenic graft vascularization and bone resorption by VEGF-expressing human mesenchymal progenitors.

Rapid vascularisation of tissue-engineered osteogenic grafts is a major obstacle in the development of regenerative medicine approaches for bone repair. Vascular endothelial growth factor (VEGF) is the master regulator of vascular growth. We investigated a cell-based gene therapy approach to generate osteogenic grafts with an increased vascularization potential in an ectopic nude rat model in vivo, by genetically modifying human bone marrow-derived stromal/stem cells (BMSC) to express rat VEGF. BMSC were loaded onto silicate-substituted apatite granules, which are a clinically established osteo-conductive material. Eight weeks after implantation, the vascular density of constructs seeded with VEGF-BMSC was 3-fold greater than with control cells, consisting of physiologically structured vascular networks with both conductance vessels and capillaries. However, VEGF specifically caused a global reduction in bone quantity, which consisted of thin trabeculae of immature matrix. VEGF did not impair BMSC engraftment in vivo, but strongly increased the recruitment of TRAP- and Cathepsin K-positive osteoclasts. These data suggest that VEGF over-expression is effective to improve the vascularization of osteogenic grafts, but also has the potential to disrupt bone homoeostasis towards excessive degradation, posing a challenge to its clinical application in bone tissue engineering.

A new cable-tie-based sternal closure device: infectious considerations.

OBJECTIVES: To determine the difference in sternal infection and other infectious events between conventional wire and cable-tie-based closure techniques post-sternotomy in a collective of patients after cardiac surgery. METHODS: The sternal ZipFix™ (ZF) system consists of a biocompatible poly-ether-ether-ketone (PEEK) cable-tie that surrounds the sternum through the intercostal space and provides a large implant-to-bone contact. Between 1 February 2011 and 31 January 2012, 680 cardiac operations were performed via sternotomy at our institution. After the exclusion of operations for active endocarditis and early mortality within 7 days, 95 patients were exclusively closed with ZF and could be compared with 498 who were closed with conventional wires (CWs) during the same period. A multivariable logistic regression analysis, including body mass index, renal impairment and emergency as suspected confounders and inverse propensity weights was performed on the infection rate. RESULTS: Total infection rate was 6.1%, with a total of 36 diagnosed sternal infections (5 in ZF and 31 in CW). Comparing ZF with CW with regard to sternal infection, there is no statistically significant difference related to the device (odds ratio: 0.067, confidence interval: 0.04-9.16, P=0.72). The propensity modelling provided excellent overlap and the mean propensity was almost the same in both groups. Thus, we have observed no difference in receiving either ZF or CW. No sternal instability was observed with the ZF device, unlike 4/31 patients in the CW group. The overall operation time is reduced by 11 min in the ZF group with identical perfusion and clamping times. CONCLUSIONS: Our study underlines a neutral effect of the sternal ZipFix™ system in patients regarding sternal infection. Postoperative complications are similar in both sternal closure methods. The cable-tie-based system is fast, easy to use, reliable and safe.