Some surprising discoveries about heart failure from Harvard

Haley Bridger
Boston, USA, August 24, 2022

Heart failure is a common and devastating disorder for which there is no cure.

Many conditions that make it difficult for the heart to pump blood, such as dilated cardiomyopathy and arrhythmogenic cardiomyopathy, can lead to heart failure, but treatments for patients with heart failure do not take these distinct conditions into account.

Investigators from Harvard Medical School and Brigham and Women’s Hospital set out to identify molecules and pathways that may contribute to heart failure, to inform more effective and personalized treatments.

Potential for rethinking

Using single nucleus RNA sequencing, or snRNAseq, to gain insight into the specific changes that occur in different cell types and cell states, the team made several surprising discoveries.

They found that while there are some shared genetic signatures, others are distinct, providing new candidate targets for therapy and predicting that personalized treatment could improve patient care. Results were published online (Science) on August 4, 2022.

“Our findings hold enormous potential for rethinking how we treat heart failure and point to the importance of understanding its root causes and the mutations that lead to changes that may alter how the heart functions,” Thomas W Smith Professor of Medicine and Professor of Genetics at the Blavatnik Institute at HMS and Director of the Cardiovascular Genetics Center at Brigham and Women’s and Co-Senior Author Christine Seidman said.

“This is fundamental research, but it identifies targets that can be experimentally pursued to propel future therapeutics. Our findings also point to the importance of genotyping. Not only does genotyping empower research but it can also lead to better, personalized treatment for patients,” she said.

Seidman and Jonathan Seidman, the Henrietta B and Frederick H Bugher Foundation Professor of Genetics at HMS collaborated with an international team.

Professors Seidman and their colleagues analysed samples from 18 control and 61 failing human hearts from patients with dilated cardiomyopathy, arrhythmogenic cardiomyopathy, or an unknown cardiomyopathy disease.

About the Human Heart

The human heart is composed of many different cell types, including cardiomyocytes (beating heart cells), fibroblasts (which help form connective tissue and contribute to scarring), and smooth muscle cells. The team used single nucleus RNA sequencing to look at the genetic readouts from individual cells and determine cellular and molecular changes in each distinct cell type.

From these data, the team identified 10 major cell types and 71 distinct transcriptional states.

They found that in the tissue from patients with dilated or arrhythmogenic cardiomyopathy, cardiomyocytes were depleted while endothelial and immune cells were increased. Overall, fibroblasts did not increase but showed altered activity.

Analyses of multiple hearts with mutations in certain disease genes, including TTN, PKP2, and LMNA, uncovered molecular and cellular differences as well as some shared responses.

The team also leveraged machine learning approaches to identify cell and genotype patterns in the data. This approach further confirmed that while some disease pathways converged, differences in genotype promoted distinct signals, even in advanced disease.

Further studies needed

The authors noted that future studies are needed to further define the molecular underpinnings of cardiomyopathies and heart failure across sex, age, and other demographics as well as across different areas of the heart. The team has made its datasets and platform freely available.

“We could not have done this work without sample donations from patients. Our goal is to honour their contributions by accelerating research and making our work available so that others can continue to advance what we understand about the disease, improve treatment, and work on strategies to prevent heart failure,” Professor Christine Seidman said.

Funding, authorship, and disclosures

Co-first authors of the paper are Daniel Reichart, who conducted the work while a research fellow in genetics in the Seidman lab and is now at the Ludwig Maximilian University Hospital of Munich, and Eric Lindberg and Henrike Maatz of the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC). Christine and Jonathan Seidman are co-corresponding authors with Lindberg and with Norbert Hubner of the MDC, the German Centre for Cardiovascular Research (DZHK), and Charité-Universitätsmedizin.

Haley Bridger Is a Senior Communications Specialist at Brigham and Women’s Hospital, Boston. The above article, adapted from a Brigham and Women’s news release appeared In the Harvard Gazette of the Harvard Medical School.

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