Lab-grown tissue reveals how inflammation may drive heart relaxation failure

Scientists study the underlying causes of a disease or test potential new drugs in animal models or cells obtained from human biopsy specimens before clinical trials. However, disease models in animals do not mimic actual human disease, and biopsy specimens are difficult to access for research purposes. Lab-grown tissues engineered from stem cells reprogrammed from human cells, called human induced pluripotent stem cells (hiPSCs), are rapidly emerging as a more reliable and accessible model in medical research.

A study led by Professor Shugo Tohyama and Senior Assistant Professor Hidenori Tani from the Department of Clinical Regenerative Medicine at Fujita Health University in Japan focused on developing robust lab models of cardiomyocytes (CMs), the heart muscle cells. Years of pioneering research have led to the development of high-quality CMs from hiPSCs in a petri dish.

“During efforts to adjust the concentrations of glucose and fatty acids in the culture medium to promote heart tissue maturation, we discovered that excessive fatty acids adversely affected the dilation capacity of the heart tissues,” Tani, the study’s first author, explains regarding this breakthrough.

“Around the same time, a study reported that the administration of high levels of fatty acids and nitric oxide synthase (NOS) inhibitors in mice induced heart failure (HF) with preserved ejection fraction (HFpEF), which led to the conception of this study.”

Building a human HFpEF model

The study, which resulted in the development of a human engineered heart tissue (hEHT) model of HFpEF, was published in Cell Stem Cell.

HFpEF is a defect in the relaxation (diastole) of the heart with normal contraction (systole). It affects more than 30 million people globally but has few effective treatment options and, therefore, poor outcomes.

Tohyama and his team induced hiPSC-CMs from readily available hiPSCs, created mature 3D heart tissue using collagen derived from porcine hearts—which the lab had previously developed—and cultured the tissues in vitro using a medium containing high fatty acid levels and L-N^G-nitroarginine methyl ester (L-NAME), an NOS inhibitor.

Supporting cells like epicardial cells, endothelial cells (ECs) and macrophages were also added to successfully create an HFpEF-hEHT that structurally and functionally mimicked diastolic HF with normal systole.

Molecular and genetic markers of HFpEF, like increased NT-proBNP and NPPB mRNA levels, reduced expression of key genes related to Ca²⁺ transport (RYR2, SERCA2A and PLN), increased fibrosis-related genes, and a shift to the stiffer, less pliable type collagen and TITIN, were demonstrated. Increased inflammation was also seen.

Drug testing points to one standout

Using the newly developed HFpEF model, the researchers tested the effectiveness of six drugs currently being used or explored in research for HFpEF treatment. Empagliflozin, a sodium-glucose cotransporter 2 inhibitor (SGLT2i) and antidiabetic medication, was the only drug that could partially prevent the development of diastolic HF.

The combined angiotensin receptor/neprilysin inhibitor, soluble guanylate cyclase activator, phosphodiesterase 5 inhibitor and nicotinamide phosphoribosyltransferase protein activator had no effect on hEHT relaxation time. On the other hand, a hyperpolarization-activated cyclic nucleotide-gated channel inhibitor worsened the disease.

Transcriptomic analysis revealed that SGLT2i had anti-inflammatory effects and partially prevented the increase in inflammatory molecules like IL-1β and IL-6 in HFpEF-hEHT. Also, the presence of ECs was required for SGLT2i to exert its effects. Further studies on the role of supporting cells revealed that the preventive effect of SGLT2i was exerted through ECs.

Inhibition of the eNOS-NO-cGMP-PKG signaling pathway in ECs was found to be the main pathological mechanism of HFpEF. SGLT2i was found to exert its anti-inflammatory effects by partially removing this inhibition and by improving the removal of Na⁺ and Ca²⁺ ions from the cells through their exchanger channels, thereby preventing their accumulation in the tissues.

A platform for tailored therapies

“The human HFpEF model established in this study can be applied to uncovering the pathophysiology of HFpEF and to research on aging,” Tohyama says.

“Furthermore, it is expected to serve as a research foundation that will contribute to the development of new therapeutic agents, the evaluation of drug efficacy, and personalized medicine for individual patients, paving the way for further research in the future,” Tohyama adds.

Who’s behind this story?

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries.

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Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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