Deletion of the Lmna Gene in Fibroblasts Causes Senescence-Associated Dilated Cardiomyopathy by Activating the Double-Stranded DNA Damage Response and Induction of Senescence-Associated Secretory Phenotype

Authors

Leila Rouhi
Gaelle Auguste
Qiong Zhou
Raffaella Lombardi
Melis Olcum
Kimia Pourebrahim
Sirisha M Cheedipudi
Saman Asghar
Kui Hong
Matthew J Robertson
Cristian Coarfa
Priyatansh Gurha
Ali J Marian

Publication Date

7-1-2022

Journal

The Journal of Cardiovascular Aging

DOI

10.20517/jca.2022.14

PMID

35891706

PMCID

PMC9311325

PubMedCentral® Posted Date

7-25-2022

PubMedCentral® Full Text Version

Author MSS

Published Open-Access

yes

Keywords

Fibroblasts, senescence, fibrosis, apoptosis, lamin A/C, heart failure, cardiomyopathy

Abstract

INTRODUCTION: Mutations in the LMNA gene, encoding Lamin A/C (LMNA), are established causes of dilated cardiomyopathy (DCM). The phenotype is typically characterized by progressive cardiac conduction defects, arrhythmias, heart failure, and premature death. DCM is primarily considered a disease of cardiac myocytes. However, LMNA is also expressed in other cardiac cell types, including fibroblasts.

AIM: The purpose of the study was to determine the contribution of the fibroblasts to DCM caused by LMNA deficiency.

METHODS AND RESULTS: The Lmna gene was deleted by crossing the platelet-derived growth factor receptor α-Cre recombinase (Pdgfra-Cre) and floxed Lmna (LmnaF/F) mice. The LMNA protein was nearly absent in ~80% of the cardiac fibroblasts and ~25% of cardiac myocytes in the Pdgfra-Cre:LmnaF/F mice. The Pdgfra-Cre:LmnaF/F mice showed an early phenotype characterized by cardiac conduction defects, arrhythmias, cardiac dysfunction, myocardial fibrosis, apoptosis, and premature death within the first six weeks of life. The Pdgfra-Cre:Lmnawild type/F (LmnaW/F) mice also showed a similar but slowly evolving phenotype that was expressed within one year of age. RNA sequencing of LMNA-deficient and wild-type cardiac fibroblasts identified differential expression of ~410 genes, which predicted activation of the TP53 and TNFA/NFκB and suppression of the cell cycle pathways. In agreement with these findings, levels of phospho-H2AFX, ATM, phospho-TP53, and CDKN1A, markers of the DNA damage response (DDR) pathway, were increased in the Pdgfra-Cre:LmnaF/F mouse hearts. Moreover, expression of senescence-associated beta-galactosidase was induced and levels of the senescence-associated secretory phenotype (SASP) proteins TGFβ1, CTGF (CCN2), and LGLAS3 were increased as well as the transcript levels of additional genes encoding SASP proteins in the Pdgfra-Cre:LmnaF/F mouse hearts. Finally, expression of pH2AFX, a bonafide marker of the double-stranded DNA breaks, was increased in cardiac fibroblasts isolated from the Pdgfra-Cre:LmnaF/F mouse hearts.

CONCLUSION: Deletion of the Lmna gene in fibroblasts partially recapitulates the phenotype of the LMNA-associated DCM, likely through induction of double-stranded DNA breaks, activation of the DDR pathway, and induction of expression of the SASP proteins. The findings indicate that the phenotype in the LMNA-associated DCM is the aggregate consequence of the LMNA deficiency in multiple cardiac cells, including cardiac fibroblasts.

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