Thymosin β4 increases cardiac cell proliferation, cell engraftment, and the reparative potency of human induced-pluripotent stem cell-derived cardiomyocytes in a porcine model of acute myocardial infarction

Abstract

Rationale: Previous studies have shown that human embryonic stem cell-derived cardiomyocytes improved myocardial recovery when administered to infarcted pig and non-human primate hearts. However, the engraftment of intramyocardially delivered cells is poor and the effectiveness of clinically relevant doses of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in large animal models of myocardial injury remains unknown. Here, we determined whether thymosin β4 (Tb4) could improve the engraftment and reparative potency of transplanted hiPSC-CMs in a porcine model of myocardial infarction (MI). Methods: Tb4 was delivered from injected gelatin microspheres, which extended the duration of Tb4 administration for up to two weeks in vitro. After MI induction, pigs were randomly distributed into 4 treatment groups: the MI Group was injected with basal medium; the Tb4 Group received gelatin microspheres carrying Tb4; the CM Group was treated with 1.2 × 10 8 hiPSC-CMs; and the Tb4+CM Group received both the Tb4 microspheres and hiPSC-CMs. Myocardial recovery was assessed by cardiac magnetic resonance imaging (MRI), arrhythmogenesis was monitored with implanted loop recorders, and tumorigenesis was evaluated via whole-body MRI. Results: In vitro, 600 ng/mL of Tb4 protected cultured hiPSC-CMs from hypoxic damage by upregulating AKT activity and BcL-XL and promoted hiPSC-CM and hiPSC-EC proliferation. In infarcted pig hearts, hiPSC-CM transplantation alone had a minimal effect on myocardial recovery, but co-treatment with Tb4 significantly enhanced hiPSC-CM engraftment, induced vasculogenesis and the proliferation of cardiomyocytes and endothelial cells, improved left ventricular systolic function, and reduced infarct size. hiPSC-CM implantation did not increase incidence of ventricular arrhythmia and did not induce tumorigenesis in the immunosuppressed pigs. Conclusions: Co-treatment with Tb4-microspheres and hiPSC-CMs was safe and enhanced the reparative potency of hiPSC-CMs for myocardial repair in a large-animal model of MI.

Cardiac Tissue Engineering for the Treatment of Myocardial Infarction

“…In terms of their differentiation capabilities, stem cells can be divided into four main types: totipotent stem cells, PSCs, multipotent stem cells, and unipotent stem cells [12]. The major progenitor/stem cells used in the field of cellular cardiomyoplasty are myoblasts [13][14][15], mesenchymal stem cells [16][17][18], ESCs [19,20], and iPSCs [21][22][23]. The advantages and disadvantages of each cell type are summarized in Table 1.…”

“…Common tissue engineering materials are made of either natural or synthetic biomaterials. Natural biomaterials include Matrigel [42][43][44], hyaluronic acid [45,46], gelatin [47][48][49], chitosan [50,51], alginate [52][53][54], collagen [42,[55][56][57][58][59], fibrin [21][22][23]55,[60][61][62][63], elastin [64], amniotic membrane [41], and spider silk proteins [65]. Synthetic biomaterials, on the other hand, include poly(ethylene glycol) (PEG) [66,67], polylactide-glycolic acid (PLGA) [68,69], polyacrylamide (PAA) [70], poly(N-isopropylacrylamide) (PNIPAAm) [71], polycaprolactone (PCL) [72], and polyurethane (PU) [73].…”

“…Fibrin is another natural biomaterial that has been extensively used to manufacture cardiac tissue [21][22][23]55,[60][61][62][63]78]. hiPSC-ECs or hiPSC-CMs have been co-cultured in fibrin gel to create cardiac patches, which were then implanted into infarcted rat hearts [60,61].…”

“…Fibrin/thrombin scaffold applied on epicardium [23] hiPSC-CM MI Micro mini-pigs Gelatin Applied on epicardium [88] hESC-SSEA-1 + I/R Patients Cells were cultured in fibrin/thrombin patch Applied on epicardium in adjunction to CABG [89,90] CABG, coronary ratery bypass graft; hESC-SSEA1, human embryonic stem cells derived stage-specific embryonic antigen-1 progenitor cells; hiPSC-CM, human induced pluripotent shiPSC-ECs, human induced pluripotent stem cells derived endothelial cells; hiPSC-SMCs, human induced pluripotent stem cells derived smooth muscle cells; hMSCs, human mesenchymal stem cells; I/R, ischemia/reperfusion; IGF-, insulin-like growth factor-1; ROA, route of administration.…”

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“…Existing research has tried several strategies to overcome the problem of low survival rate of transplanted cells, but these methods are not outstanding in improving cell survival rate (20)(21)(22). Recently, a variety of methods have been reported to enhance the survival of transplanted hiPSC-CMs to reduce myocardial infarction, including the addition of biologically active substances, genetic modification of cells, and the application of cell tissue patch (13,16,(23)(24)(25). The problem of low survival rate of transplanted cells can be partially overcome by giving repeated doses of cells (20).…”