SUMMARY In the heart, augmented Ca2+ fluxing drives contractility and ATP generation through mitochondrial Ca2+ loading. Pathologic mitochondrial Ca2+ overload with ischemic injury triggers mitochondrial permeability transition pore (MPTP) opening and cardiomyocyte death. Mitochondrial Ca2+ uptake is primarily mediated by the mitochondrial Ca2+ uniporter (MCU). Here we generated mice with adult and cardiomyocyte-specific deletion of Mcu, which produced mitochondria refractory to acute Ca2+ uptake, augmented ATP production and MPTP opening upon acute Ca2+ challenge. Mice lacking Mcu in the adult heart were also protected from acute ischemia-reperfusion injury. However, resting/basal mitochondrial Ca2+ levels were normal in hearts of Mcu-deleted mice and mitochondria lacking MCU eventually loaded with Ca2+ after stress stimulation. Indeed, Mcu-deleted mice were unable to immediately sprint on a treadmill unless warmed-up for 30 minutes. Hence, MCU is a dedicated regulator of short-term mitochondrial Ca2+ loading underlying a “fight-or-flight” response that acutely matches cardiac workload with ATP production.

Summary Human induced pluripotent stem cells (hiPSCs) hold promise for myocardial repair following injury, but preclinical studies in large animal models are required to determine optimal cell preparation and delivery strategies to maximize functional benefits and to evaluate safety. Here, we utilized a porcine model of acute myocardial infarction (MI) to investigate the functional impact of intramyocardial transplantation of hiPSC-derived cardiomyocytes, endothelial cells, and smooth muscle cells, in combination with a 3D fibrin patch loaded with insulin growth factor (IGF)-encapsulated microspheres. hiPSC-derived cardiomyocytes integrated into host myocardium and generated organized sarcomeric structures, and endothelial and smooth muscle cells contributed to host vasculature. Tri-lineage cell transplantation significantly improved left ventricular function, myocardial metabolism, and arteriole density, while reducing infarct size, ventricular wall stress and apoptosis without inducing ventricular arrhythmias. These findings in a large animal MI model highlight the potential of utilizing hiPSC-derived cells for cardiac repair.

We have fabricated a clinically relevant size of hCMP with trilineage cardiac cells derived from human induced-pluripotent stem cells. The hCMP matures in vitro during 7 days of dynamic culture. Transplantation of this type of hCMP results in significantly reduced infarct size and improvements in cardiac function that are associated with reduction in left ventricular wall stress. The hCMP treatment is not associated with significant changes in arrhythmogenicity.

Cardiac stem cell-like populations exist in adult hearts, and their roles in cardiac repair remain to be defined. Sca-1 is an important surface marker for cardiac and other somatic stem cells. We hypothesized that heart-derived Sca-1 ؉ / CD31 ؊ cells may play a role in myocardial infarction-induced cardiac repair/remodeling. Mouse heart-derived Sca-1 ؉ /CD31 ؊ cells cultured in vitro could be induced to express both endothelial cell and cardiomyocyte markers. Immunofluorescence staining and fluorescence-activated cell sorting analysis indicated that endogenous Sca-1 ؉ /CD31 ؊ cells were significantly increased in the mouse heart 7 days after myocardial infarction (MI). Western blotting confirmed elevated Sca-1 protein expression in myocardium 7 days after MI. Transplantation of Sca-1 ؉ /CD31 ؊ cells into the acutely infarcted mouse heart attenuated the functional decline and adverse structural remodeling initiated by MI as evidenced by an increased left ventricular (LV) ejection fraction, a decreased LV end-diastolic dimension, a decreased LV endsystolic dimension, a significant increase of myocardial neovascularization, and modest cardiomyocyte regeneration. Attenuation of LV remodeling was accompanied by remarkably improved myocardial bioenergetic characteristics. The beneficial effects of cell transplantation appear to primarily depend on paracrine effects of the transplanted cells on new vessel formation and native cardiomyocyte function. Sca-1 ؉ / CD31 ؊ cells may hold therapeutic possibilities with regard to the treatment of ischemic heart disease.

SummaryThere is no consensus in the stem cell field as to what constitutes the mature cardiac myocyte. Thus, helping formalize a molecular signature for cardiac myocyte maturation would advance the field. In the mammalian heart, inactivation of the “fetal” TNNI gene, TNNI1 (ssTnI), together in temporal concert with its stoichiometric replacement by the adult TNNI gene product, TNNI3 (cTnI), represents a quantifiable ratiometric maturation signature. We examined the TNNI isoform transition in human induced pluripotent stem cell (iPSC) cardiac myocytes (hiPSC-CMs) and found the fetal TNNI signature, even during long-term culture. Rodent stem cell-derived and primary myocytes, however, transitioned to the adult TnI profile. Acute genetic engineering of hiPSC-CMs enabled a rapid conversion toward the mature TnI profile. While there is no single marker to denote the mature cardiac myocyte, we propose that tracking the cTnI:ssTnI protein isoform ratio provides a valuable maturation signature to quantify myocyte maturation status across laboratories.

Rationale Conventional three-dimensional (3D) printing techniques cannot produce structures of the size at which individual cells interact. Objective Here, we used multiphoton-excited, 3-dimensional printing (MPE-3DP) to generate a native-like, extracellular matrix (ECM) scaffold with submicron resolution, and then seeded the scaffold with cardiomyocytes (CMs), smooth-muscle cells (SMCs), and endothelial cells (ECs) that had been differentiated from human induced-pluripotent stem cells (iPSCs) to generate a human, iPSC-derived cardiac muscle patch (hCMP), which was subsequently evaluated in a murine model of myocardial infarction (MI). Methods and Results The scaffold was seeded with ~50,000 human, iPSC-derived CMs, SMCs, and ECs (in a 2:1:1 ratio) to generate the hCMP, which began generating calcium transients and beating synchronously within 1 day of seeding; the speeds of contraction and relaxation and the peak amplitudes of the calcium transients increased significantly over the next 7 days. When tested in mice with surgically induced MI, measurements of cardiac function, infarct size, apoptosis, both vascular and arteriole density, and cell proliferation at week 4 after treatment were significantly better in animals treated with the hCMPs than in animals treated with cell-free scaffolds, and the rate of cell engraftment in hCMP-treated animals was 24.5% at week 1 and 11.2% at week 4. Conclusions Thus, the novel MPE-3DP technique produces ECM-based scaffolds with exceptional resolution and fidelity, and hCMPs fabricated with these scaffolds may significantly improve recovery from ischemic myocardial injury.

Background-The present study examined whether transplantation of adherent bone marrow-derived stem cells, termed pMultistem, induces neovascularization and cardiomyocyte regeneration that stabilizes bioenergetic and contractile function in the infarct zone and border zone (BZ) after coronary artery occlusion. Methods and Results-Permanent left anterior descending artery occlusion in swine caused left ventricular remodeling with a decrease of ejection fraction from 55Ϯ5.6% to 30Ϯ5.4% (magnetic resonance imaging). Four weeks after left anterior descending artery occlusion, BZ myocardium demonstrated profound bioenergetic abnormalities, with a marked decrease in subendocardial phosphocreatine/ATP ( 31 P magnetic resonance spectroscopy; 1.06Ϯ0.30 in infarcted hearts [nϭ9] versus 1.90Ϯ0.15 in normal hearts [nϭ8; PϽ0.01]). This abnormality was significantly improved by transplantation of allogeneic pMultistem cells (subendocardial phosphocreatine/ATP to 1.34Ϯ0.29; nϭ7; PϽ0.05). The BZ protein expression of creatine kinase-mt and creatine kinase-m isoforms was significantly reduced in infarcted hearts but recovered significantly in response to cell transplantation. MRI demonstrated that the infarct zone systolic thickening fraction improved significantly from systolic "bulging" in untreated animals with myocardial infarction to active thickening (19.7Ϯ9.8%, PϽ0.01), whereas the left ventricular ejection fraction improved to 42.0Ϯ6.5% (PϽ0.05 versus myocardial infarction). Only 0.35Ϯ0.05% donor cells could be detected 4 weeks after left anterior descending artery ligation, independent of cell transplantation with or without immunosuppression with cyclosporine A (with cyclosporine A, nϭ6; no cyclosporine A, nϭ7). The fraction of grafted cells that acquired an endothelial or cardiomyocyte phenotype was 3% and Ϸ2%, respectively. Patchy spared myocytes in the infarct zone were found only in pMultistem transplanted hearts. Vascular density was significantly higher in both BZ and infarct zone of cell-treated hearts than in untreated myocardial infarction hearts (PϽ0.05). Conclusions-Thus, allogeneic pMultistem improved BZ energetics, regional contractile performance, and global left ventricular ejection fraction. These improvements may have resulted from paracrine effects that include increased vascular density in the BZ and spared myocytes in the infarct zone.

ObjectiveThis study was to investigate factors influencing the length of stay and predictors for the risk of readmission at an acute psychiatric inpatient unit.MethodTwo comparative studies were embedded in a retrospective cross-sectional clinical file audit. A randomly selected 226 episodes of admissions including 178 patients during a twelve-month period were reviewed. A total of 286 variables were collected and analysed. A case control study was employed in the study of length of stay. A retrospective cohort study was used to investigate the predictors for the risk of readmission.ResultsLogistic regression analyses showed that 10 variables were associated with length of stay. Seclusion during the index admission, accommodation problems and living in an area lacking community services predicted longer stay. During the follow-up period 82 patients (46%) were readmitted. Cox regression analyses showed 9 variables were related to the risk of readmission. Six of these variables increased the risk of readmission, including history of previous frequent admission, risk to others at the time of the index admission and alcohol intoxication. More active and assertive treatment in the community post-discharge decreased the risk of readmission.ConclusionsLength of stay is multifactorially determined. Behavioural manifestations of illness and lack of social support structures predicted prolonged length of stay. Good clinical practice did not necessarily translate to a shorter length of stay. Therefore, length of stay is predictable, but not readily modifiable within the clinical domain. Good clinical practice within the community following discharge likely reduces the risk of readmission. Quality of inpatient care does not influence the risk of readmission, which therefore raises a question about the validity of using the rate of readmission as an outcome measure of psychiatric inpatient care.