Abstract Body: Background
LMNA-related dilated cardiomyopathy, also known as cardiolaminopathy, is an autosomal dominant disorder with complete penetrance that results in left ventricular dilation and cardiac dysfunction. LMNA mutations are associated with ventricular tachyarrhythmias and conduction abnormalities. Notably, some patients with cardiolaminopathy exhibit prominent cardiac fibrosis, which is linked to more severe clinical phenotypes and increased mortality. However, the mechanisms linking LMNA mutations to alterations in non-cardiomyocyte cell types and the development of fibrosis remain unclear.

Hypothesis
We hypothesize that LMNA mutations promote endothelial-to-mesenchymal transition (EndoMT) and disrupt intercellular communication, contributing to cardiac dysfunction and fibrosis.

Aims
By integrating multiomic sequencing with our patient-specific iPSC platform, we aim to elucidate mechanisms underlying microvascular dysfunction and fibrosis in LMNA-DCM and identify potential therapeutic targets.

Methods
We performed single-nucleus multiome sequencing (RNA and ATAC) on cardiac tissue from two patients with LMNA-related dilated cardiomyopathy and one healthy donor. We also profiled cardiac tissue from wild-type and LMNA-mutant mice. We further characterized patient-specific iPSCs and CRISPR-generated isogenic controls using both 2D culture and 3D organoid systems.

Results
Transcriptomic analyses of human and mouse cardiac tissue revealed that cardiomyocyte clusters in LMNA-DCM exhibited downregulation of muscle contraction and metabolic processes. Endothelial cell clusters from both species showed increased stress responses and mesenchymal markers, including upregulation of SMAD3, TGFb, and TWIST1, and downregulation of endothelial cell markers PECAM1 and VWF. These findings were corroborated in iPSC-derived cells from two LMNA-DCM cell lines.

Conclusion
These results highlight the role of microvascular dysfunction in LMNA-related dilated cardiomyopathy. Integrating analyses of LMNA-DCM cardiac tissue with our iPSC platform provides an opportunity to define mechanisms driving cardiac fibrosis and identify new therapeutic strategies.