Notch signalling restricts inflammation and serpine1 expression in the dynamic endocardium of the regenerating zebrafish heart

Abstract

The zebrafish heart regenerates after ventricular damage through a process involving inflammation, fibrotic tissue deposition/removal and myocardial regeneration. Using 3D whole-mount imaging, we reveal a highly dynamic endocardium during cardiac regeneration, including changes in cell morphology, behaviour and gene expression. These events lay the foundation for an initial expansion of the endocardium that matures to form a coherent endocardial structure within the injury site. We studied two important endocardial molecules, Serpine1 and Notch, which are implicated in different aspects of endocardial regeneration. Notch signalling regulates developmental gene expression and features of endocardial maturation. Also, Notch manipulation interferes with attenuation of the inflammatory response and cardiomyocyte proliferation and dedifferentiation. serpine1 is strongly expressed very early in the wound endocardium, with decreasing expression at later time points. serpine1 expression persists in Notch-abrogated hearts, via what appears to be a conserved mechanism. Functional inhibition studies show that Serpine1 controls endocardial maturation and proliferation and cardiomyocyte proliferation. Thus, we describe a highly dynamic endocardium in the regenerating zebrafish heart, with two key endocardial players, Serpine1 and Notch signalling, regulating crucial regenerative processes.

Runx1 promotes scar deposition and inhibits myocardial proliferation and survival during zebrafish heart regeneration

“…These injury-specific endocardial populations were highly positive for serpine1 expression (Supp Fig. 4b), indicating that this population is largely similar to the previously identified highly mobile serpine1-positive endocardial population (36), which was confirmed on sections (Supp Fig. 4c-c', arrowheads).…”

“…5a). Upregulation of collagens in the wound endocardium has been observed before (36,37), but has not previously been analysed using single cell transcriptomics. Clustering of the citrine/mcherry double positive cells showed 2 clusters (C4 and C5) appearing after injury, with upregulation of genes involved in extracellular matrix formation ( Fig.…”

Zebrafish heart regeneration: 15 years of discoveries

“…Münch and colleagues have recently studied endocardial recovery in detail following cryoinjury. They demonstrate that endocardial cells surrounding the wound robustly proliferate between 3 and 5 dpi, prior to the peak of cardiomyocyte proliferation at 7 dpi (Bednarek et al., ; Münch, Grivas, Gonzalez‐Rajal, Torregrosa‐Carrión, & la Pompa, ). Thereafter, endocardial cells acquire a motile phenotype and migrate to cover the wound area, after which they reorganize into a coherent epithelium.…”

“…Endocardial maturation is Notch‐dependent, as inhibition of Notch signaling reduces the percentage of mature endocardial cells in the injured area. Notch activation is also required for resolving early inflammation (Münch et al., ).…”

Actomyosin dynamics, Bmp and Notch signaling pathways drive apical extrusion of proepicardial cells

“…7e). The effect of Notch1 inhibition for PE formation was also assessed with the Notch inhibitor, RO-4929097 (RO) 56 . RO administration reduced PE cluster size (2 ± 2 cells vs 8 ± 3 cells in controls), which occurred concomitant with the loss of actin cytoskeleton polarization in DP cells at the midline (Fig.…”