-Rodent hearts can regenerate myocardium lost to apical resection or myocardial infarction for up to 7 days after birth, but whether a similar window for myocardial regeneration also exists in large mammals is unknown. -Acute myocardial infarction (AMI) was surgically induced in neonatal pigs on postnatal days 1, 2, 3, 7, and 14 (i.e., the P1, P2, P3, P7, and P14 groups, respectively). Cardiac systolic function was evaluated before AMI and at 30 days post AMI via transthoracic echocardiography. Cardiomyocyte cell cycle activity was assessed via immunostaining for proliferation and mitosis markers, infarct size was evaluated histologically, and telomerase activity was measured by quantitative PCR. -Systolic function at day 30 post- AMI was largely restored in P1 animals and partially restored in P2 animals, but significantly impaired when AMI was induced on postnatal day 3 or later. Hearts of P1 animals showed little evidence of scar formation or wall thinning on day 30 after AMI, with increased measures of cell-cycle activity seen six days after AMI (i.e. postnatal day 7) compared to postnatal day 7 in noninfarcted hearts. -The neonatal porcine heart is capable of regeneration following AMI during the first 2 days of life. This phenomenon is associated with induction of cardiomyocyte proliferation, and is lost when cardiomyocytes exit cell cycle shortly after birth.

The regenerative capacity of an adult cardiac tissue is insufficient to repair the massive loss of heart tissue, particularly cardiomyocytes (CMs), following ischemia or other catastrophic myocardial injuries. The delivery methods of therapeutics agents, such as small molecules, growth factors, exosomes, cells, and engineered tissues have significantly advanced in medical science. Furthermore, with the controlled release characteristics, nanoparticle (NP) systems carrying drugs are promising in enhancing the cardioprotective potential of drugs in patients with cardiac ischemic events. NPs can provide sustained exposure precisely to the infarcted heart via direct intramyocardial injection or intravenous injection with active targets. In this review, we present the recent advances and challenges of different types of NPs loaded with agents for the repair of myocardial infarcted heart tissue.

Background-We have shown that genetic overexpression of cell cycle proteins can increase the proliferation of transplanted cardiomyocytes derived from human induced-pluripotent stem cells (hiPSC-CMs) in animal models of myocardial infarction (MI). Here, we introduce a new, nongenetic approach to promote hiPSC-CM cell cycle activity and proliferation in transplanted human cardiomyocyte patches (hCMPs).Methods-Mice were randomly distributed into 5 experimental groups (n = 10 per group). One group underwent Sham surgery, and the other 4 groups underwent MI induction surgery followed by treatment with hCMPs composed of hiPSC-CMs and nanoparticles that contained CHIR99021 and FGF1 (the NP CF -hCMP group), with hCMPs composed of hiPSC-CMs and empty nanoparticles (the NP E -hCMP group); with patches containing the CHIR99021/FGF-loaded nanoparticles but lacking hiPSC-CMs (the NP CF -Patch group), or patches lacking both the nanoparticles and cells (the E-Patch group). Cell cycle activity was evaluated via Ki67 and Aurora B expression, bromodeoxyuridine incorporation, and phosphorylated histone 3 levels (immunofluorescence); engraftment via human cardiac troponin T or human nuclear antigen expression (immunofluorescence) and bioluminescence imaging; cardiac function via echocardiography; infarct size and wall thickness via histology; angiogenesis via isolectin B4 expression (immunofluorescence); and apoptosis via TUNEL and caspace 3 expression (immunofluorescence).

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Preconditioning with the ROCK inhibitor Y-27632 increased the engraftment of transplanted hiPSC-CM in a murine MI model, while reversibly impairing hiPSC-CM contractility and promoting adhesion.

Coronary artery disease (CAD) is a type of disease in which the lumen is narrowed or blocked due to atherosclerotic lesions in the coronary artery, resulting in myocardial ischaemia, oxygen deprivation and necrosis. CAD is one of the highest mortality diseases in the world, with an estimated 12 million deaths due to coronary atherosclerosis by the end of 2030, including non-ST-segment elevation myocardial infarction and ST segment elevation myocardial infarction. 1 The pathogenesis of CAD is complex, and there are no obvious

The paracrine effect, mediated by chemical signals that induce a physiological response on neighboring cells in the same tissue, is an important regenerative mechanism for stem cell-based therapy. Exosomes are cell-secreted nanovesicles (50-120 nm) of endosomal origin, and have been demonstrated to be a major contributor to the observed stem cell-mediated paracrine effect in the cardiac repair process. Following cardiac injury, exosomes deriving from exogenous stem cells have been shown to regulate cell apoptosis, proliferation, angiogenesis, and fibrosis in the infarcted heart. Exosomes also play a crucial role in the intercellular communication between donor and recipient cells. Human induced pluripotent stem cells (hiPSCs) are promising cell sources for autologous cell therapy in regenerative medicine. Here, we review recent advances in the field of progenitor-cell derived, exosome-based cardiac repair, with special emphasis on exosomes derived from hiPSCs.

NPs encapsulated with CHIR + FGF1 exerted substantial myocardial protective effects and represents a potentially novel strategy for improving postischemic myocardial protection. Results Identification of chemicals that promote cell cycle activity of human induced pluripotent stem cell-derived cardiomyocytes. Using the BrdU incorporation assay, we screened several chemicals for their capacity to enhance the cell cycle activity of cultured human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). We picked hiPSC-CMs because they are easy to handle and represent a practical system for drug testing and screening (5). These chemicals included Ly294002 (PI3K inhibitor) (6), FGF1 (6, 7), SB203580 and VX702 (p38 MAPK inhibitors) (6), KN93 (Ca 2+ /calmodulin-dependent protein kinase II inhibitor) (8), Su1498 (Flk-1 inhibitor) (8), and CHIR99021 (Wnt activator and GSK3α and 3β inhibitor) (8, 9). We found a combination of 5 μM CHIR99021 and 100 ng/mL FGF1 was the most potent treatment to induce cell cycle in hiPSC-derived cardiomyocytes (Supplemental Figure 1; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.132796DS1). Characterization of CHIR-FGF1-NPs. We have previously shown that PLGA NPs can be used as a platform for slow release (up to 4 weeks) of chemicals to injured animal hearts and that they provide cardioprotection (2). To characterize the long-term cardioprotective function of the FGF/CHIR combination in vivo, we formulated the PLGA NPs with these 2 factors. The size of PLGA NPs was measured using scanning electron microscopy, for both CHIR99021-and FGF1-loaded NPs (Supplemental Figure 2, A and B). Quantification of particle diameter for CHIR-NPs (Supplemental Figure 2C) and FGF1-NPs (Supplemental Figure 2D) yielded values of 123.63 ± 44.48 nm and 129.57 ± 45.94 nm, respectively. The size and shape of CHIR-NPs and FGF1-NPs were uniform. The encapsulation efficiency of CHIR-NPs and FGF1-NPs, i.e., (the amount encapsulated/total amount available) × 100%, was 50.41% and 62.8 ± 1.6%, respectively. The concentration of encapsulated CHIR and FGF1 was 8.07 μg/mg and 1.26 ± 0.03 μg/mg, respectively. Determination of release kinetics of CHIR-and FGF1-loaded NPs as a function of time, using either NanoDrop via UV-Vis spectrophotometer (for CHIR) or ELISA (for FGF1), and the cumulative percentage of CHIR and FGF1 released from NPs, are shown in Supplemental Figure 2, E and F. When 1000 μg of CHIR-and FGF1-loaded NPs were incubated in 1000 μL of Dulbecco's phosphate-buffered saline (DPBS), pH 7.4 at 37°C, 55% of the encapsulated CHIR was released during the first day and 85% by day 15 (Supplemental Figure 2E). In contrast, 55% of the encapsulated FGF1 was released during the initial 3 days, and 63% was released by day 10. Notably, between day 1 and day 30, the release kinetics strictly followed the Korsmeyer-Peppas model for FGF1-NPs (Supplemental Figure 2F). Fitting this model, C t /C 0 = kt n , where C t = concentration at time t; C 0 = equilibrium concentration; ...