Efficacy of Multi-Layered Human iPS Cell-Derived Cardiovascular Cell Sheets in a Pacing-Induced Canine Dilated Cardiomyopathy Model

Abstract

Background: Dilated cardiomyopathy (DCM) is a progressive, intractable disease leading to heart failure. Heart transplantation is the only curative treatment, but donor scarcity limits access. Induced pluripotent stem cell (iPSC)-based therapies are promising, yet suitable large-animal models and robust preclinical data are lacking. Methods: We generated multi-layered cardiovascular cell sheets from human iPSCs by combining cardiomyocytes with endothelial and stromal cells, overcoming stacking limits using interleaved gelatin hydrogel microspheres, yielding a thicker cardiac tissue-like construct (IHJ-301). To enable rigorous testing in non-ischemic heart failure, we established a modified canine rapid-pacing heart failure model that maintains depressed function without mortality by continuing pacing at a slightly reduced rate after induction (Step-Down Pacing Heart Failure model). IHJ-301 was implanted epicardially onto the left ventricular surface via thoracotomy, and cardiac function was assessed by echocardiography and right-heart catheterization. Results: After 4 weeks of rapid pacing (230±10 bpm), left ventricular ejection fraction (LVEF) was reduced from 77.8±1.1% (pre-pacing) to 44.9±1.9% (n=11) (0 W). Continued pacing at 210±10 bpm for additional 4 weeks resulted in no mortality and maintained depressed function (4 W LVEF 47.3±2.6%). IHJ-301 was implanted at 0 W. At 4 weeks post-implantation (4 W), all animals in the IHJ-301 group (n=5) showed greater functional improvement than sham (n=6). Absolute changes from 0 W to 4 W were: ΔLVEF (%) 9.38±1.47 vs. 1.90±0.34; Δfractional shortening (%) 4.84±0.75 vs. 0.97±0.18; stroke volume (mL/beat) 1.21±1.26 vs. −2.99±0.60; cardiac output (L/min) 0.19±0.19 vs. −0.58±0.12 (all p<0.05). Conclusions: We established a non-ischemic large-animal heart failure model that sustains depressed function for one month, enabling clear therapeutic readouts. IHJ-301 significantly improved multiple parameters of cardiac function, providing preclinical evidence that IHJ-301 could offer a promising therapeutic option for DCM.

1. Introduction

Dilated cardiomyopathy (DCM) is characterized by dilation of the ventricles, particularly the left ventricle, accompanied by systolic dysfunction. It is a progressive and intractable disease that often leads to heart failure or fatal arrhythmias, and no curative therapy exists other than heart transplantation [1]. Although viral infection, genetic mutations, and autoimmune mechanisms have been implicated, the etiology remains undetermined in many cases [2–4]. The prevalence of DCM is estimated to be approximately 1 in 2,500 adults worldwide and about 14 per 100,000 adults in Japan [5, 6]. Heart transplantation remains the only curative treatment; however, the number of eligible patients is severely restricted by the limited supply of donor hearts [7]. For example, in Japan, only 50–80 transplantations are performed annually, despite approximately 20,000 patients with DCM [5, 7]. Furthermore, transplanted donor hearts face a significant risk of functional failure beyond ten years after transplantation, caused by progressive diffuse intimal thickening of the coronary arteries [8].

Left ventricular assist devices (LVADs), initially introduced as bridge-to-transplantation therapy, are increasingly used as destination therapy in patients who are not transplant candidates [9, 10]. In Japan, approximately 50 cases per year are currently performed as destination therapy [7, 9]. Although LVADs provide circulatory support, their long-term use carries substantial risks, including cerebrovascular events due to thrombosis, infection, ventricular arrhythmias, right heart failure, and aortic insufficiency [11, 12]. These limitations underscore the urgent need for novel therapeutic strategies for DCM. Various cell therapies have been explored to date, such as transplantation of mesenchymal stem cells or differentiated cells [13, 14]. Skeletal myoblast sheets, for example, showed promising efficacy in ischemic cardiomyopathy (ICM), but failed to demonstrate statistically significant benefit in a clinical trial for DCM [15]. Recently, induced pluripotent stem cell (iPSC)–based therapies have attracted worldwide attention [16, 17]. Several iPSC-derived cardiac products are already under clinical trials, including cardiomyocyte sheets (jRCT2053190081) and cardiomyocyte spheroids (jRCT2033210163) for ICM. Following them, recently clinical trials for DCM with iPSC-derived cardiomyocyte sheets (jRCT2053230136) and IHJ-301 (jRCT2033240447) have been just launched.