Abstract
<title>Abstract</title> <p> Hyperglycaemia-mediated cardiac injury is characterised by cardiac hypertrophy, fibrosis and progressive cardiac dysfunction. The <italic>Paired box 6 (Pax6)</italic> is a transcription factor described with a role in cardiac fibroblast cells in in-vitro conditions, and transforming growth factor-beta (Tgf-β) is a central pro-fibrotic mediator in the diabetic heart; however, the roles of Pax6 and Tgf-β1 in the streptozotocin (STZ)-induced hyperglycaemic mouse heart have not been elucidated. In the present study, hyperglycaemia was induced in mice using streptozotocin (STZ) at 50mg/kg body weight for five consecutive days. Mice with blood glucose levels > 200 mg/dL were considered hyperglycaemic. Cardiac tissues were subsequently analysed by hematoxylin and eosin (H&E) staining for structural deformities and immunohistochemistry to examine the cellular localisation and distribution of Pax6 across different cardiac layers along with Tgf-β1. Co-localisation of Pax6 with Tgf-β1 was observed in epicardial mesothelial cells, fibroblasts or activated fibroblasts, cardiomyocytes within the myocardium, and endocardial cells of the endocardium in both control and hyperglycaemic mouse heart. RNA-sequencing was performed to identify differentially expressed genes, Pax6 and Tgf-β1 mRNA and protein, validated by quantitative real-time PCR (qPCR) and Western blotting. Transcriptomic analysis identified Pax6 among the top 100 upregulated genes in STZ-induced hyperglycaemic heart as compared to control. These findings suggest STZ-induced hyperglycemia increases the expression of Pax6 and Tgf-β1 in the mouse heart and potentially promotes fibroblast to myofibroblast differentiation and contributes to cardiac dysfunction. Collectively, this study provides novel evidence linking hyperglycaemia to increased Pax6 and Tgf-β1 expression, and Pax6 co-expression with Tgf-β1 might contribute to fibroblast-to-myofibroblast differentiation and progression of cardiac complications. </p>