Sebastian V. Rojas

Induced pluripotent stem cell (iPSC)-derived Flk-1 progenitor cells engraft, differentiate, and improve heart function in a mouse model of acute myocardial infarction

AIMS Induced pluripotent stem cell (iPSC)-derived cardiovascular progenitor cells represent a suitable autologous cell source for myocardial regeneration as they have the capability to form myocardial cells and to contribute to revascularization. As a first proof of concept we evaluated the potential of a murine iPSC-derived cardiovascular progenitor population, which expresses the surface marker foetal liver kinase-1 (Flk-1), to restore myocardial tissue and improve cardiac function after acute myocardial infarction (MI) in mice. METHODS AND RESULTS iPSC-derived Flk-1(pos) vs. Flk-1(neg) cells were selected by fluorescence activated cell sorting (FACS) and injected into the ischaemic myocardium of left anterior descending coronary artery (LAD)-ligated mice. Addressing safety aspects we used an octamer binding factor 4 (Oct4)-enhanced green fluorescent protein (eGFP) expressing iPSC clone from the transgenic Oct4-eGFP reporter mouse strain OG2 to enable FACS-based depletion of undifferentiated cells prior to transplantation. Infarcted animals were treated with placebo (phosphate-buffered saline, n = 13), Flk-1(neg) cells (n = 14), or Flk-1(pos) cells (n = 11; 5 × 10(5) cells each). Heart function was evaluated by magnetic resonance imaging and conductance catheter analysis 2 weeks postoperatively. Cardiovascular in vitro and in vivo differentiations were investigated by immunofluorescence staining. Treatment with Flk-1(pos) and Flk-1(neg) cells resulted in a favourable myocardial remodelling and improved left ventricular function. Engraftment and functional benefits were superior after transplantation of Flk-1(pos) compared with Flk-1(neg) cells. Furthermore, Flk-1(pos) grafts contained considerably more vascular structures in relation to Flk-1(neg) grafts. CONCLUSION iPSC-derived Flk-1(pos) progenitor cells differentiate into cardiovascular lineages in vitro and in vivo and improve cardiac function after acute MI. This proof of concept study paves the way for an autologous iPSC-based therapy of MI.

First implantation in man of a new magnetically levitated left ventricular assist device (HeartMate III).

Outcomes of heart failure patients supported by a continuous-flow left ventricular assist device (LVAD) have steadily improved during the past decade, largely due to better patient selection and management. Nevertheless, adverse events, such as bleeding, infection, stroke, and thrombus, persist and limit the overall effectiveness of this therapy. Bleeding is the most common serious adverse event that results from the extensive surgery required for implantation and blood component damage due to shear forces in the small blood flow paths of current design axialflow and centrifugal-flow pumps. Excessive bleeding results in reoperations, intensive care time, and total hospital stay, which greatly increases a patient’s exposure for infection. The current clinically used pumps create levels of shear force that can activate platelets and damage von Willebrand factor, causing a disruption in the coagulation system that can manifest as thrombosis or gastrointestinal bleeding. The HeartMate III LVAD (Thoratec Corp, Pleasanton, CA) is a new compact intrapericardial centrifugal-flow pump with a full magnetically levitated rotor (Figure 1). The design differs from currently used devices due to actively controlled rotation and levitation of the rotor allowing gaps in the blood flow that are 10 to 20 times wider, which may minimize blood component trauma and result in more stable coagulation. The HeartMate III is now under clinical investigation, and we present here a case report of the first implantation of the device to support a patient with severe heart failure. The patient is a 55-year-old man with the diagnosis of dilated cardiomyopathy and a recent history of multiple hospital admissions due to worsening heart failure symptoms. With multiple medications, the mean arterial blood pressure was 70 mm Hg, cardiac index was 2.1 liters/min/m, and the left ventricular ejection fraction was 10% to 15%. He was classified as Interagency Registry for Mechanically Assisted Circulatory Support Profile 3. After meeting the HeartMate III Conformite Europeene Mark Study inclusion criteria, the patient gave informed consent, and the implantation was performed by Dr. Schmitto and his team at Hannover Medical School, Hanover, Germany on June 25, 2014. After a median sternotomy, the pericardium was only partially opened to help protect right heart function yet allowing access to the vena cava and aorta for cardiopulmonary bypass cannulation. Once full cardiopulmonary bypass was started, the pericardium was fully opened, the heart was elevated, and the myocardium was cored with the HeartMate coring knife approximately 1 cm medial to the left ventricular apex. The sewing cuff was attached around the apical opening with 2-0 Ethibond pledgeted sutures. The inflow conduit was inserted into the left ventricle, and the device was quickly secured to the heart with a locking mechanism. The outflow graft was trimmed for length and anastomosed to the ascending aorta. The percutaneous lead (driveline) was externalized with a doubletunnel technique and exited through the right upper quadrant of the abdominal wall. Cardiopulmonary bypass lasted 59 minutes, and the total operative time was 149 minutes.

Minimally Invasive Off-Pump Left Ventricular Assist Device Exchange: Anterolateral Thoracotomy

The new generation of left ventricular assist devices has enabled minimally invasive surgical procedures. Herein we present a novel technique of left ventricular assist device exchange through a left-sided anterolateral thoracotomy.

Minimally-invasive LVAD Implantation: State of the Art

Nowadays, the worldwide number of left ventricular assist devices (LVADs) being implanted per year is higher than the number of cardiac transplantations. The rapid developments in the field of mechanical support are characterized by continuous miniaturization and enhanced performance of the pumps, providing increased device durability and a prolonged survival of the patients. The miniaturization process enabled minimally-invasive implantation methods, which are associated with generally benefitting the overall outcome of patients. Therefore, these new implantation strategies are considered the novel state of the art in LVAD surgery. In this paper we provide a comprehensive review on the existing literature on minimally-invasive techniques with an emphasis on the different implantation approaches and their individual surgical challenges.

Minimally Invasive Ventricular Assist Device Surgery

The use of mechanical circulatory support to treat patients with congestive heart failure has grown enormously, recently surpassing the number of annual heart transplants worldwide. The current generation of left ventricular assist devices (LVADs), as compared with older devices, is characterized by improved technologies and reduced size. The result is that minimally invasive surgery is now possible for the implantation, explantation, and exchange of LVADs. Minimally invasive procedures improve surgical outcome; for example, they lower the rates of operative complications (such as bleeding or wound infection). The miniaturization of LVADs will continue, so that minimally invasive techniques will be used for most implantations in the future. In this article, we summarize and describe minimally invasive state-of-the-art implantation techniques, with a focus on the most common LVAD systems in adults.

Minimally Invasive Left Ventricular Assist Device Explantation After Cardiac Recovery: Surgical Technical Considerations

The new generation of left ventricular assist devices (LVADs) has enabled minimally invasive surgical procedures for implantation. Herein we present two alternative approaches for minimally invasive LVAD explantation following cardiac recovery, avoiding a sternotomy and improving patient safety.

First series of mechanical circulatory support in non-compaction cardiomyopathy: Is LVAD implantation a safe alternative?

BACKGROUND Left ventricular non-compaction (LVNC) is a rare cardiac disorder characterized by prominent trabeculae and deep recesses of the ventricular myocardium. Patients with LVNC may develop severe congestive heart failure refractory to medical therapy. However, heart transplantation is strongly limited due to donor organ shortage. Thus mechanical circulatory support by left ventricular assist devices (LVADs) is a promising alternative. Nevertheless, hypertrabeculation and proarrhythmogenic potential in LVNC might represent important hurdles for success of LVAD therapy in these patients. METHODS AND RESULTS We retrospectively analyzed the data of a total of 5 patients (3 HVAD, Heartware®; 2 HeartMate II, Thoratec®) with LVNC who underwent LVAD implantation in our institution between 2010 and 2014. Mean follow-up time was 86.5weeks. 30-day survival was 100% without major intrahospital complications. During follow-up, 3 patients developed pump thrombosis requiring pump replacement. Arrhythmias were not detected during follow-up as assessed by ICD interrogation. CONCLUSIONS LVAD implantation in LVNC can be performed with low intrahospital complication rates. However, we observed a high incidence of pump thrombosis during follow-up, possibly related to thromboembolic predisposition by the underlying LVNC. Therefore, careful management of anticoagulation appears to be critical in these patients.

Substantial Early Loss of Induced Pluripotent Stem Cells Following Transplantation in Myocardial Infarction

The limited success of cardiac stem cell therapy has lately generated discussion regarding its effectiveness. We hypothesized that immediate cell loss after intramyocardial injection significantly obscures the regenerative potential of stem cell therapy. Therefore, our aim was to assess the distribution and quantity of induced pluripotent stem cells after intramyocardial delivery using in vivo bioluminescence analysis. In this context, we wanted to investigate if the injection of different cell concentrations would exert influence on cardiac cell retention. Murine-induced pluripotent stem cells were transfected for luciferase reporter gene expression and transplanted into infarcted myocardium in mice after left anterior descending coronary artery ligation. Cells were delivered constantly in aqueous media (15 μL) in different cell concentrations (group A, n = 10, 5.0 × 10(5) cells; group B, n = 10, 1.0 × 10(6) cells). Grafts were detected using bioluminescence imaging. Organ explants were imaged 10 min after injection to quantify early cardiac retention and cell biodistribution. Bioluminescence imaging showed a massive early displacement from the injection site to the pulmonary circulation, leading to lung accumulation. Mean cell counts of explanted organs in group A were 7.51 × 10(4) ± 4.09 × 10(3) (heart), 6.44 × 10(4) ± 2.48 × 10(3) (left lung), and 8.06 × 10(5) ± 3.61 × 10(3) (right lung). Respective cell counts in group B explants were 1.69 × 10(5) ± 7.69 × 10(4) (heart), 2.11 × 10(5) ± 4.58 × 10(3) (left lung), and 3.25 × 10(5) ± 9.35 × 10(3) (right lung). Applying bioluminescence imaging, we could unveil and quantify massive early cardiac stem cell loss and pulmonary cell accumulation following intramyocardial injection. Increased injection concentrations led to much higher intracardiac cell counts; however, pulmonary biodistribution of transplanted cells still persisted. Therefore, we recommend applying tissue engineering techniques for cardiac stem cell transplantations in order to improve cardiac retention and limit biodistribution.

Rhesus monkey cardiosphere-derived cells for myocardial restoration

BACKGROUND AIMS Cardiosphere-derived cells (CDC) have been proposed as a promising myocardial stem cell source for cardiac repair. They have been isolated from human, porcine and rodent cardiac biopsies. However, their usefulness for myocardial restoration remains controversial. We aimed to determine the survival, differentiation and functional effects of Rhesus monkey CDC (RhCDC) in a mouse model of myocardial infarction. METHODS RhCDC were isolated and characterized by flow cytometry and reverse transcriptase (RT)-polymerase chain reaction (PCR) and compared with human CDC. They were injected intramyocardially into severe combined immune deficiency (SCID) beige mice after ligature of the left anterior descending artery (LAD). Phosphate-buffered saline (PBS) served as placebo. Medium treatment alone was used to distinguish between cellular and non-cellular effects. Animals were divided into a non-infarcted control group (n = 7), infarct control groups (n = 24), medium-treated infarct groups (n = 35) and RhCDC-treated infarct groups (n = 33). Follow-up was either 1 or 4 weeks. LV function was assessed by pressure-volume loop analysis. Differentiation was analyzed by immunhistochemical profiling and RT-PCR. RESULTS Proliferating RhCDC grafts were detected after transplantation in an acute infarct model. RhCDC as well as medium treatment protected myocardium within the infarct area and improved LV function. RhCDC had a superior regenerative effect than medium alone. CONCLUSIONS For the first time, RhCDC have been used for the restoration of infarcted myocardium. RhCDC proliferated in vivo and positively influenced myocardial remodeling. This effect could be mimicked by treatment with unconditioned medium alone, emphasizing a non-cellular paracrine therapeutic mechanism. However, as a robust cardiac stem cell source, CDC might be useful to evoke prolonged paracrine actions in cardiac stem cell therapy.

First experiences with HeartMate 3 follow-up and adverse events

Background: The novel HeartMate 3 (HM3) left ventricular assist device (LVAD) received its CE mark in October 2015. It is a new compact LVAD featuring fully magnetically levitated pump, artificial pulse, large pump gaps, and a modular driveline. Here, we present outcomes and adverse events of a single‐center cohort 6 months after HM3 implantation. Methods: We retrospectively studied a patient cohort of 27 patients who were supported with the HM3 at a single institution. We excluded patients with biventricular assist devices and other types of assist devices as well as LVAD exchange and re‐operative procedures. Results: Twenty‐seven patients were enrolled into the study. Within 1 year after HM3 implantation, 1 patient received a heart transplant and 3 patients died. Thirty‐day survival was 88.9% and 6 months 85.2%. No pump thrombosis and no strokes were observed within 6 months. Right heart failure was diagnosed in 1 patient after HM3 implantation (3.7%). No technical complications of the pump were documented. No pump exchanges were necessary. Conclusions: The novel LVAD HM3 has already shown good CE mark trial results. Within this first report after the CE mark trial, the 6‐month survival after HM3 implantation was 85.2%. The HM3 showed excellent midterm results with 0% stroke and 0% pump thrombosis rates 6 months after implantation.