# Enhancing KLF15 activity in cardiomyocytes: a novel approach to prevent pathological reprogramming and fibrosis via nuclease-deficient dCas9VPR

## TL;DR

This paper explores using CRISPRa to enhance KLF15 activity in heart cells, preventing harmful changes and fibrosis linked to heart disease.

## Contribution

The study introduces a novel CRISPRa approach to restore KLF15 activity and reveals a regulatory circuit involving TGF-β, KLF15, and AZGP1 in heart disease.

## Key findings

- Enhancing KLF15 activity via CRISPRa suppresses pathological gene expression and restores metabolic balance in stressed heart cells.
- KLF15-dependent AZGP1 regulation mediates an anti-fibrotic effect through cardiomyocyte-fibroblast communication.
- A CRISPRa system was engineered into an AAV vector for potential clinical use in human cardiomyocytes.

## Abstract

Transcriptional activity perturbation holds promise for selectively modulating harmful transcriptional networks, but its therapeutic potential remains largely unexplored. We employed a network-based analysis of single-cell heart transcriptomes to identify transcription factor activities linked to pathological cardiomyocytes in vivo. This analysis revealed that transcriptional activity of Krüppel-like factor 15 (KLF15) exhibited the most significant change in pathological cardiomyocytes, characterized by less effective repression of disease-associated genes in stressed hearts, which correlated with reduced KLF15 expression. To restore KLF15 activity, we utilized CRISPR/nuclease-dead (d)Cas9-based transcriptional enhancement (CRISPRa) in cardiomyocytes, which effectively abolished fetal reprogramming by simultaneously suppressing pathological gene expression and restoring metabolic homeostasis under sustained stress conditions. Furthermore, we identified a novel cell-nonautonomous anti-fibrotic effect mediated by cardiomyocyte-fibroblast crosstalk, and revealed the contribution of KLF15-dependent Alpha-2-glycoprotein 1, zinc-binding (AZGP1) regulation in this process. We also elucidated the upstream mechanisms of KLF15 regulation, highlighting its role as a cell-specific downstream target of the broad TGF-β canonical signaling pathway, along with its downstream-dependent mechanisms in human cardiomyocytes. Finally, to enhance the therapeutic potential of this approach, we engineered and validated an adeno-associated viral (AAV) vector with a small CRISPRa system for endogenous regulation in human cardiomyocytes suitable for clinical applications. Overall, we elucidated a regulatory circuit involving TGF-β, KLF15, and AZGP1, which coordinates critical pathological responses through cellular crosstalk between cardiomyocytes and fibroblasts. Importantly, we demonstrated the efficacy of CRISPRa as an epigenetic intervention restoring a critical transcriptional function disrupted in non-genetic heart failure. This approach provides a promising blueprint for future adaptation targeting additional non-hereditary pathologies.