Functional and transcriptional sequelae of cardiomyocyte telomere shortening and their pathologic relevance in dilated cardiomyopathy and ischemic heart failure
Authors: Brandt M , Khraisat S , Luo Q , Munzel T , Wenzel P 
Published: November 2023

Abstract

Background
Heart failure (HF) is associated with cardiomyocyte (CM) telomere shortening. Sequelae have been described with the telomere-p53-mitochondrion model. P53 deficiency only partially ameliorates mitochondrial defects in telomerase deficient mice hinting at additional pathways.

Purpose
We assessed the cardiac phenotype and transcriptome of early/advanced telomere shortening and evaluated the pathological relevance by correlation to published HF datasets.

Methods
Male (6-8w) telomerase RNA-component deficient mice, early (generation 2, mTRG2) and advanced (mTRG5) were phenotyped vs age-matched C57BL/6 mice (B6). Adult CMs from mTRG2/G5 vs B6 mice were characterized (live imaging, quantitative fluorescence in situ hybridization (Q-FISH) and transcriptome analysis (microarray Mouse MTA 1.0)). Gene expression analysis was performed (Ingenuity Pathway Analysis, Qiagen) and correlated to comparable datasets from &gt; 120 000 curated datasets.

Results
CMs exhibited significant telomere shortening in mTR(-/-) mice increasing with every generation (mTRG2/G5 p&lt;0.0001 vs B6). In parallel, echocardiography revealed increasing defects of left ventricular (LV) systolic function (LVEF, mTRG5 &lt;0.01 vs B6), LV global longitudinal strain mTRG2/G5 p&lt;0.001 vs B6) and LV contractile reserve (mTRG2/G5 p&lt;0.05 vs B6). Live imaging showed increasing impairment of mitochondrial polarization with all energy substrates (mTRG2/G5 p&lt;0.0001 vs B6). Transcriptome analysis revealed 357/2906 differentially expressed genes (DEGs) in mTRG2/G5-CMs vs B6-CMs (fold change &lt;-1.5 or &gt;1.5 and p-value &lt;0.05).
Upstream Regulator (UR) analysis revealed significant overrepresentation of numerous regulators including angiotensinogen (z-score 7.5, p-value 1.1E-32), transforming growth factor (TGF)-b1 (z-score 7.5, p-value 2.2E-60), interleukin (IL)-1 (z-score 5.6, p-value 1.1E-26), IL-6 (expression fold change 11.3, z-score 6.9 p-value 2.65E-32), IL-17A (z-score 4.8, p-value 4.4E-27) and NFkB (z-score 6.0 p-value 4.9E-19). Activation of TP53 (z-score 5.8, p-value 5.3E-31) and inhibition of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A) (z-score -4.4, p-value 6.3E-19) confirmed the relevance of the p53-mitochondrion-axis.
Analysis matching revealed a significant overlap of gene expression patterns in the same direction (positive z-score) between mTR-/--mice and all comparable datasets of dilated (DCM) and ischemic cardiomyopathy (ICM) (human/mouse), the overlap increasing with increasing telomere shortening (e.g. DCM vs mTRG2: z-score 17.7, UR p-value 1.5E-16; DCM vs mTRG5: z-score 56.8, UR-value 1.5E-62). Matching to datasets after cardiac regeneration (e.g. after left ventricular assist device implantation) revealed a reversal of gene expression patterns (negative z-score).

Conclusions
Our results reveal the large extent of transcriptional alterations upon cardiac telomere shortening and support their central role in the pathogenesis of HF.