Comparison of photoreceptor grafts in preclinical models with incomplete or complete photoreceptor loss, showed differential transplant success with effective and impaired integration, respectively. Thus, Cpfl1/Rho-/- mice represent a potential benchmark model resembling patients with severe retinal degeneration to optimize photoreceptor replacement therapies.

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After two decades of intensive research and attempts of clinical translation, stem cell based therapies for cardiac diseases are not getting closer to clinical success. This review tries to unravel the obstacles and focuses on underlying mechanisms as the target for regenerative therapies. At present, the principal outcome in clinical therapy does not reflect experimental evidence. It seems that the scientific obstacle is a lack of integration of knowledge from tissue repair and disease mechanisms. Recent insights from clinical trials delineate mechanisms of stem cell dysfunction and gene defects in repair mechanisms as cause of atherosclerosis and heart disease. These findings require a redirection of current practice of stem cell therapy and a reset using more detailed analysis of stem cell function interfering with disease mechanisms. To accelerate scientific development the authors suggest intensifying unified computational data analysis and shared data knowledge by using open-access data platforms.

Cellular inflammation following acute myocardial infarction has gained increasing importance as a target mechanism for therapeutic approaches. We sought to investigate the effect of syngeneic cardiac induced cells (CiC) on myocardial inflammation using 18F-FDG PET (Positron emission tomography)-based imaging and the resulting effect on cardiac pump function using cardiac magnetic resonance (CMR) imaging in a mouse model of myocardial infarction. Mice underwent permanent left anterior descending coronary artery (LAD) ligation inducing an acute inflammatory response. The therapy group received an intramyocardial injection of 10 6 CiC into the border zone of the infarction. Five days after myocardial infarction, 18F-FDG PET was performed under anaesthesia with ketamine and xylazine (KX) to image the inflammatory response in the heart. Flow cytometry of the mononuclear cells in the heart was performed to analyze the inflammatory response. The effect of CiC therapy on cardiac function was determined after three weeks by CMR. The 18F-FDG PET imaging of the heart five days after myocardial infarction (MI) revealed high focal tracer accumulation in the border zone of the infarcted myocardium, whereas no difference was observed in the tracer uptake between infarct and remote myocardium. The CiC transplantation induced a shift in 18F-FDG uptake pattern, leading to significantly higher 18F-FDG uptake in the whole heart, as well as the remote area of the heart. Correspondingly, high numbers of CD11 + cells could be measured by flow cytometry in this region. The CiC transplantation significantly improved the left ventricular ejection function (LVEF) three weeks after myocardial infarction. The CiC transplantation after myocardial infarction leads to an improvement in pump function through modulation of the cellular inflammatory response five days after myocardial infarction. By combining CiC transplantation and the cardiac glucose uptake suppression protocol with KX in a mouse model, we show for the first time, that imaging of cellular inflammation after myocardial infarction using 18F-FDG PET can be used as an early prognostic tool for assessing the efficacy of cardiac stem cell therapies.

Background: Ventricular arrhythmias (VA) are a common cause of sudden death after myocardial infarction (MI). Therefore, developing new therapeutic methods for the prevention and treatment of VA is of prime importance. Methods: Human bone marrow derived CD271 + mesenchymal stem cells (MSC) were tested for their antiarrhythmic effect. This was done through the development of a novel mouse model using an immunocompromised Rag2 −/− γc −/− mouse strain subjected to myocardial "infarction-reinfarction". The mice underwent a first ischemia-reperfusion through the left anterior descending (LAD) artery closure for 45 min with a subsequent second permanent LAD ligation after seven days from the first infarct. Results: This mouse model induced various types of VA detected with continuous electrocardiogram (ECG) monitoring via implanted telemetry device. The immediate intramyocardial delivery of CD271 + MSC after the first MI significantly reduced VA induced after the second MI. Conclusions: In addition to the clinical relevance, more closely reflecting patients who suffer from severe ischemic heart disease and related arrhythmias, our new mouse model bearing reinfarction warrants the time required for stem cell engraftment and for the first time enables us to analyze and verify significant antiarrhythmic effects of human CD271 + stem cells in vivo. make them very unlikely to produce hazardous action potentials or contribute to arrhythmias [10,11]. However, the availability of a realistic small animal model reflecting the situation in patients is of utmost importance. For testing the rhythmological behavior of human cells, Rag2 −/− γc −/− has been selected. These mice (strain C, 129S4-Rag2 tm1.1Flv Il2rg tm1.1Flv /J) have been derived from a V17 embryonic stem cell line (BALB/c × 129 heterozygote) targeted for the Rag2 and Il2rg genes and lack B, T, and natural killer (NK) cells [12]. They have a deletion of the common cytokine receptor γ chain (γc) gene, and thus reduced numbers of peripheral T and B lymphocytes, and absent natural killer cell (NK) activity. A genetic cross with a recombinase activating gene 2 (RAG2) deficient strain produced mice doubly homozygous for the γc and RAG2 null alleles (Rag2 −/− γc −/− ) with a stable phenotype characterized by the absence of all T lymphocyte, B lymphocyte, and NK cell function [13]. This phenotype makes the completely a lymphoid strain useful for studies on human tissue xenotransplantation [14].As previously shown, stem cell antiarrhythmic effects appear after completion of an approximately one-week engraftment period [4]. The major objective of the present study was to develop a mouse model that enables us to reproduce VA several days after an initial MI. In vivo electrophysiological mouse models are well established: Previously, Berul et al. established an open chest epicardial study of conduction properties with the ability to induce second and third degree heart blocks, but no induction of tachyarrhythmias after programmed stimulation [15]. Hagendorff et al. used a rapid t...