Novel Role of delta like non-canonical notch ligand 1 ( <i>Dlk1</i> ) Gene in Cardiac Fibrogenesis

Introduction: Cardiac fibrosis characterized by excessive deposition of extracellular matrix in the heart muscle is a common feature of heart failure and has been associated with reduction in cardiac function. However, there is currently no FDA approved medication for the treatment of cardiac fibrosis. Delta like non-canonical notch ligand 1 ( Dlk1 ) gene is a paternally expressed gene on human chromosome 14 and 12 in mice. This gene plays a role in development and cell proliferation through embryonic life with tapered effect in adults. DLK1 regulates several processes including hematopoiesis, angiogenesis, adipogenesis (Falix et al 2012). Our previous study has shown that DLK1 expression is significantly reduced in cardiac fibrosis (Rodriguez et al., 2019), other studies has also shown that DLK1 could function as an inhibitor of notch signaling in renal damage experimental model and hence protects against renal damage (Marquez-Exposito et al., 2021). We hypothesize that DLK1 could prevent myocardial fibrosis by inhibition of fibroblast to myofibroblast conversion. Hence, hold a therapeutic potential for cardiac fibrosis. Methods: Wildtype (WT) and Dlk1 knockout ( Dlk1 -/-) mice were subjected to myocardial infarction (MI) by permanent ligation of the left anterior descending artery to induce cardiac fibrosis. Cardiac function was assessed by echocardiography, Histology of heart and Masson trichrome staining was used to assess excessive collagen deposition in heart tissue. Fibrotic markers were examined by RT-QPCR and protein expression by immunoblotting. Mice with cardiac fibroblast specific knockout of Dlk1 gene were generated and further used in this study to determine the effect of cardiac fibroblast -specific knockout of Dlk1 gene in cardiac fibrosis. Result: Echocardiography shows a reduction in Ejection fraction (EF) and Fractional shortening (FS), also an increase in LVID (Left Ventricular Internal Diameter) was observed in Dlk1 -/- mice compared to WT. RNA expression of fibrotic markers including Lysyl Oxidase (LOX), alpha Smooth Muscle Actin (αSMA) and Connective Tissue Growth Factor (CTGF) shows increased expression in Dlk1 null mice when compared to WT mice, similar result was observed with protein expression using western blotting. These findings were also confirmed in-vitro with isolated primary cardiac fibroblasts. Loss of Dlk1 also show an increase in fibroblast migration in wound scratch assay compared to WT. Knock out of Dlk1 was observed to have an exaggerated effect on Myocardial infarction (MI) evident by an increase in LVIDs and LVIDd while EF and FS were reduced with MI. Similar results were also observed in mice with cardiac fibroblast specific knockout of Dlk1 indicating the effect of DLK1 in cardiac function. Gene expression and protein expression of LOX, CTGF and alpha Smooth muscle Actin (αSMA) were further increased following MI and conditional knockout of Dlk1 compared to control. Conclusion: Loss of Dlk1 gene exaggerates cardiac fibrosis following MI, the current findings confirm increased expression of fibrotic markers with absence of Dlk1 and suggests the role of DLK1 in the prevention of cardiac fibrosis and heart failure. In addition, evidence of fibrosis is increased in cardiac fibroblast specific knockout of Dlk1 gene. Future study will show the effect of over-expression of Dlk1 gene in the prevention or possible reversal of fibrosis, also mechanism through which these activities occur will be further studied. Paul Quigley predoctoral Fellowship This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.