Engrailed 1 mediates fibroblast activation and tissue fibrosis

• Applicant: Dr. Alexandru-Emil Matei
• Subject Area: Rheumatology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 462543409

Fibrotic diseases are a major cause of morbidity and mortality in the developed countries. They are characterized by excessive deposition of extracellular matrix (ECM) that impairs the normal function of the affected organs. Systemic sclerosis (SSc) is a prototypical idiopathic fibrotic disease with systemic involvement. In SSc and other fibrotic diseases, resting resident fibroblasts become chronically active and differentiate into myofibroblasts, which deposit excessive ECM and generate contraction forces. Transforming growth factor β (TGFβ) is at the center of the processes that lead to fibroblast activation. Persistent TGFβ signaling is sufficient to induce a myofibroblast phenotype in resting fibroblasts and fibrotic disease in mice; moreover, it is required for experimental fibrosis of different etiologies. However, the TGFβ downstream intracellular signaling pathways that lead to fibroblast activation and the mechanisms by which TGFβ signaling is regulated are still incompletely understood. Engrailed 1 (EN1 / En1) is essentially required for normal development of many embryonal structures. En1 is transiently expressed during murine dermal embryonic development in a distinct fibroblast lineage that becomes the major fibroblast population as main producer of collagen 1 and 3 in adult dermis. However, it is not known how EN1 is regulated after embryogenesis and whether En1 signaling regulates fibroblast activation in fibrotic tissues. Our preliminary results showed that EN1 is upregulated in SSc and experimental skin fibrosis in a TGFβ-, SMAD-dependent manner. We also showed that EN1 promotes fibroblast activation induced by TGFβ. EN1 induces transcriptomic changes with increased expression of profibrotic genes and reduced expression of antifibrotic genes to promote fibroblast activation. Our in silico analyses predicted that En1 regulates gene expression both directly, by acting as a transcriptional activator, and indirectly. Moreover, we showed that fibroblast-specific knockout of En1 prevents experimental skin fibrosis of different etiologies in murine models that mimic different disease subtypes or stages of SSc. In the current proposal, we aim to: 1. characterize the role of secretion and internalization of EN1 in fibrosis, since EN1 was previously shown to be secreted and internalized and act as a signaling molecule in a paracrine manner; 2. study the potential involvement of EN1 in cytoskeletal rearrangements during myofibroblast differentiation, as suggested by the RNA sequencing analysis from our preliminary results; 3. identify the interaction partners of EN1 that modulate its effects on fibroblast activation, since these can influence the specificity of EN1 for target genes and be responsible for a potential involvement of EN1 in regulation of translation.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr. Jörg Hans Wilhelm Distler; Dr. Andrea-Hermina Györfi