Lior Yankelson

Identification and selection of cardiomyocytes during human embryonic stem cell differentiation

Human embryonic stem cells (hESC) are pluripotent lines that can differentiate in vitro into cell derivatives of all three germ layers, including cardiomy‐ocytes. Successful application of these unique cells in the areas of cardiovascular research and regenerative medicine has been hampered by difficulties in identifying and selecting specific cardiac progenitor cells from the mixed population of differentiating cells. We report the generation of stable transgenic hESC lines, using lentiviral vectors, and single‐cell clones that express a reporter gene (eGFP) under the transcriptional control of a cardiac‐specific promoter (the human myosin light chain‐2V promoter). Our results demonstrate the appearance of eGFP‐expressing cells during the differentiation of the hESC as embryoid bodies (EBs) that can be identified and sorted using FACS (purity>95%, viability>85%). The eGFP‐expressing cells were stained positively for cardiac‐specific proteins (>93%), expressed cardiac‐specific genes, displayed cardiac‐specific action‐potentials, and could form stable myocardial cell grafts following in vivo cell transplantation. The generation of these transgenic hESC lines may be used to identify and study early cardiac precursors for developmental studies, to robustly quantify the extent of cardiomyocyte differentiation, to label the cells for in vivo grafting, and to allow derivation of purified cell populations of cardiomyocytes for future myocardial cell therapy strategies.—Huber, I., Itzhaki, I., Caspi, O., Arbel, G., Tzukerman, M., Gepstein, A., Habib, M., Yankelson, L., Kehat, I., Gepstein, L. Identification and selection of cardiomy‐ocytes during human embryonic stem cell differentiation. FASEB J. 21, 2551–2563 (2007)

Cell Therapy for Modification of the Myocardial Electrophysiological Substrate

Background— Traditional antiarrhythmic pharmacological therapies are limited by their global cardiac action, low efficacy, and significant proarrhythmic effects. We present a novel approach for the modification of the myocardial electrophysiological substrate using cell grafts genetically engineered to express specific ionic channels. Methods and Results— To test the aforementioned concept, we performed ex vivo, in vivo, and computer simulation studies to determine the ability of fibroblasts transfected to express the voltage-sensitive potassium channel Kv1.3 to modify the local myocardial excitable properties. Coculturing of the transfected fibroblasts with neonatal rat ventricular myocyte cultures resulted in a significant reduction (68%) in the spontaneous beating frequency of the cultures compared with baseline values and cocultures seeded with naive fibroblasts. In vivo grafting of the transfected fibroblasts in the rat ventricular myocardium significantly prolonged the local effective refractory period from an initial value of 84±8 ms (cycle length, 200 ms) to 154±13 ms (P<0.01). Margatoxin partially reversed this effect (effective refractory period, 117±8 ms; P<0.01). In contrast, effective refractory period did not change in nontransplanted sites (86±7 ms) and was only mildly increased in the animals injected with wild-type fibroblasts (73±5 to 88±4 ms; P<0.05). Similar effective refractory period prolongation also was found during slower pacing drives (cycle length, 350 to 500 ms) after transplantation of the potassium channels expressing fibroblasts (Kv1.3 and Kir2.1) in pigs. Computer modeling studies confirmed the in vivo results. Conclusions— Genetically engineered cell grafts, transfected to express potassium channels, can couple with host cardiomyocytes and alter the local myocardial electrophysiological properties by reducing cardiac automaticity and prolonging refractoriness.

Silicone-Based Scar Therapy: A Review of the Literature

Hypertrophic and keloid scars still are among the banes of plastic surgery. In the treatment arsenal at the disposal of the plastic surgeon, topical silicone therapy usually is considered the first line of treatment or as an adjuvant to other treatment methods. Yet, knowledge concerning its mechanisms of action, clinical efficacy, and possible adverse effects is rather obscure and sometimes conflicting. This review briefly summarizes the existing literature regarding the silicone elastomer’s mechanism of action on scars, the clinical trials regarding its efficacy, a description of some controversial points and contradicting evidence, and possible adverse effects of this treatment method. Topical silicone therapy probably will continue to be the preferred first-line treatment for hypertrophic scars due to its availability, price, ease of application, lack of serious adverse effects, and relative efficacy. Hopefully, future randomized clinical trials will help to clarify its exact clinical efficacy and appropriate treatment protocols to optimize treatment results.

Norton scale for predicting prognosis in elderly patients undergoing trans-catheter aortic valve implantation: A historical prospective study

BACKGROUND The Norton scale is traditionally used to assess the risk of pressure ulcers. However, recent studies have shown its prognostic utilization in elderly patients with diverse medical conditions. The association between low admission Norton scale scores (ANSS), complications, and mortality in elderly patients following trans-catheter aortic valve implantation (TAVI) has never been studied. We aimed to determine if low ANSS (≤16) is associated with complications and 30-day and 1-year mortality in elderly patients undergoing TAVI. METHODS The medical charts of elderly (≥70 years) TAVI patients at the Tel-Aviv Medical Center, a tertiary medical center, were studied for the following measurements: ANSS, demographics, co-morbidities, complications during hospitalization, and 30-day and 1-year mortality. Complications included: an atrio-ventricular block, stroke, and vascular complications. RESULTS The cohort included 302 elderly patients: 179 (59.3%) were women; the mean age was 83.3±5.1 years. Following TAVI, 112 (37.1%) patients had complications other than pressure ulcers, 10 (3.3%) patients died within 30 days, and 42 (13.9%) patients died within one year. Overall, 36 (11.9%) patients had low ANSS. 1-year mortality rates were almost three times higher in patients with low ANSS relative to patients with high ANSS (27.8% vs. 12.0%; the relative risk 1.1; p=0.018). A stepwise logistic regression analysis showed that ANSS was independently inversely associated with 1-year mortality (p=0.018). Complications and 30-day mortality rates were similar in both groups. CONCLUSIONS Low ANSS are associated with 1-year mortality after TAVI. The Norton scale may therefore be used as an additional tool for elderly patient selection before TAVI.

From gene therapy and stem cells to clinical electrophysiology.

Gene therapy, cell therapy, and tissue engineering are emerging as novel experimental therapeutic paradigms for a variety of cardiovascular disorders. In the current report we will review the possible implications of these emerging technologies in the field of cardiac electrophysiology. Initially, the possible role of myocardial gene and cell therapies in creating a biological alternative to electronic pacemakers for the treatment of bradyarrhythmias will be discussed. This will be followed by a description of the possible applications of using similar strategies for the treatment of common tachyarrhythmias. Finally, the electrophysiological implications of cardiac stem cell therapy for heart failure, as well as the possible in vitro applications of stem cell technology for electrophysiological studies and drug screening, will be discussed. While these emerging strategies provide a paradigm shift from conventional treatment modalities, this field is still at its infancy and several obstacles, discussed in this review, should be overcome before any clinical breakthroughs can be expected.