Borriello, Federica (2025) LYSOPHOSPHATIDIC ACID RECEPTOR 4 (LPAR4) - DEPENDENT SIGNALING IS INVOLVED IN CELL PHENOTYPE REMODELLING DURING DIRECT CARDIAC REPROGRAMMING. [Tesi di dottorato]

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Abstract

Cardiovascular diseases remain the leading cause of morbidity worldwide. Following ischemic events, such as myocardial infarction (MI), cardiac fibroblasts(CFs) replace necrotic cardiomyocytes, contributing to inflammation and further tissue damage. Due to the heart's limited regenerative capacity, this leads to progressive cardiac dysfunction, and the only currently available therapy is heart transplantation. Developing therapeutic strategies based on Direct Cardiac Reprogramming (DCR) of fibroblasts into induced cardiomyocytes (iCMs)has garnered significant attention as a promising approach for myocardial repair. Among these strategies, chemical-induced Direct Cardiac Reprogramming(CiDCR) is particularly noteworthy for its potential to achieve transdifferentiation without altering the genetic profile, providing a safer alternative to virus based methods. Despite recent advances, significant challenges still remain. We have recently demonstrated that a 24-hour pre-treatment with PTC-209, a chemical inhibitor of Polycomb Repressive Complex 1 (PRC1), on CFs and mouse embryonic fibroblasts (MEFs) could enhance CiDCR efficiency. This preconditioning induces an epigenetic perturbation, altering the expression of 1.499 genes, including transcription factors and inflammatory pathways, among which we identified Lysophosphatidic Acid Receptor 4 (LPAR4), a GPCR recently recognized as a specific surface marker for cardiac progenitor cells (CPCs) during embryonic cardiovascular differentiation. Here we demonstrated that LPAR4 can play a crucial role in driving CiDCR. Stimulation of LPAR4 during early stages of transdifferentiation increases reprogramming yield, as demonstrated by increased numbers of beating cell clusters and generation of CPCs. Conversely, the knockdown LPAR4 reduces reprogramming efficiency. To further investigate the possible role of LPAR4 in CiDCR, we undertook an omics approach of proteomic analysis collaborating with ISPAAM CNR, to characterize any protein deregulation upon LPAR4 knockdown, finding a close relation between LPAR4 and basal cellular metabolic rate. In conclusion, this study could advance the optimization of the CiDCR protocol by improving cell maturation and identifying novel molecular targets. It provides deeper insights into the mechanisms that drive CiDCR, offering new opportunities for more targeted interventions in cardiac regeneration.

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