Human iPSC-Derived Cardiomyocytes of Peripartum Patients With Cardiomyopathy Reveal Aberrant Regulation of Lipid Metabolism

Peripartum cardiomyopathy (PPCM) is a rare form of heart failure occurring in the last trimester of pregnancy or in the first months after delivery.1 The diagnosis is based on exclusion criteria, and specific biomarkers remain unidentified.1 Proposed mechanisms of PPCM pathophysiology are based on various mouse models harboring cardiac-specific genetic defects,2,3 which demonstrated typical PPCM characteristics, but mutations in these genes remain to be associated with PPCM in patients.4 This study aims to identify aberrant pathways in cardiomyocytes obtained from induced pluripotent stem cells (iPSC) derived from patients with PPCM. Two patients with PPCM with acute heart failure (diagnosed within weeks after delivery) have been included in the study. Patients A and B were aged 37 and 28 years with a left ventricular ejection fraction of 17% and 45% and elevated levels of N-terminal pro-B-type natriuretic peptide 1309 ng/L and 2743 ng/L at presentation, respectively. Patient A was compared with her sister and patient B with her mother in paired analyses; both controls were healthy, had a normal echocardiogram, and have had multiple uncomplicated deliveries. Patients were screened for genetic variations in 61 genes associated with cardiomyopathies, but none was identified. All participants provided written informed consent. This study was approved by the local Medical Ethical Committee (METc:2014.104). Pregnancy-associated wall stress was simulated in vitro by applying cyclic mechanical stretch to the iPSC-derived cardiomyocytes (iPSC-CM; Figure [A]). RNA sequencing analysis of these conditions resulted in a total of 3316 differentially expressed genes (Figure [B]). We identified 95 common differentially expressed genes in healthy mechanically stretched iPSC-CM and in both static and stretched PPCM iPSC-CM compared with healthy static iPSC-CM (designated as the intersection of interest in yellow, Figure [B]). Therefore, a stretch-induced stress response was observed in all mechanically stretched cells, but also in static PPCM iPSC-CM. Relative expression levels of these 95 genes were visualized in a heat map (Figure [C]), and a pathway overrepresentation analysis was performed. Predicted gene ontology terms were organized into superclusters (Figure [D]). Gene ontology terms pertained mostly to lipid metabolism as part of the fatty alcohol biosynthesis supercluster of gene ontology terms, and 28 of 95 differentially expressed genes were associated to metabolic processes (depicted in red, Figure [C]). In silico transcription factor enrichment analysis identified key transcription factors SREBP1 (sterol regulatory element-binding transcription factor 1), NFY (nuclear transcription factor Y), SP1 (Sp1 transcription factor), MAX (MYC-associated factor X), and CEBPB (CCAAT enhancer-binding protein beta). To underscore the relevance of these findings, we aimed to validate our findings in an established PPCM mouse model caused by cardiac-specific STAT3 conditional knockout (STAT3-CKO).2 These STAT3-CKO mice consistently developed PPCM as demonstrated by a severely reduced cardiac function (Figure [E]). Gene expression analysis Martijn F. Hoes , PhD* Nils Bomer , PhD* Melanie Ricke-Hoch, PhD* Tristan V. de Jong, PhD Karla F. Arevalo Gomez, MD, MSc Stefan Pietzsch, PhD Denise Hilfiker-Kleiner, PhD† Peter van der Meer , MD, PhD†