A dynamic notch injury response activates epicardium and contributes to fibrosis repair

JL Russell, SC Goetsch, NR Gaiano, JA Hill… - Circulation …, 2011 - Am Heart Assoc
JL Russell, SC Goetsch, NR Gaiano, JA Hill, EN Olson, JW Schneider
Circulation research, 2011Am Heart Assoc
Rationale: Transgenic Notch reporter mice express enhanced green fluorescent protein in
cells with C-promoter binding factor-1 response element transcriptional activity (CBF1-REx4-
EGFP), providing a unique and powerful tool for identifying and isolating “Notch-activated”
progenitors. Objective: We asked whether, as in other tissues of this mouse, EGFP localized
and functionally tagged adult cardiac tissue progenitors, and, if so, whether this cell-based
signal could serve as a quantitative and qualitative biosensor of the injury repair response of …
Rationale:
Transgenic Notch reporter mice express enhanced green fluorescent protein in cells with C-promoter binding factor-1 response element transcriptional activity (CBF1-REx4-EGFP), providing a unique and powerful tool for identifying and isolating “Notch-activated” progenitors.
Objective:
We asked whether, as in other tissues of this mouse, EGFP localized and functionally tagged adult cardiac tissue progenitors, and, if so, whether this cell-based signal could serve as a quantitative and qualitative biosensor of the injury repair response of the heart.
Methods and Results:
In addition to scattered endothelial and interstitial cells, Notch-activated (EGFP+) cells unexpectedly richly populated the adult epicardium. We used fluorescence-activated cell sorting to isolate EGFP+ cells and excluded hematopoietic (CD45+) and endothelial (CD31+) subsets. We analyzed EGFP+/CD45/CD31 cells, a small (<2%) but distinct subpopulation, by gene expression profiling and functional analyses. We called this mixed cell pool, which had dual multipotent stromal cell and epicardial lineage signatures, Notch-activated epicardial-derived cells (NECs). Myocardial infarction and thoracic aortic banding amplified the NEC pool, increasing fibroblast differentiation. Validating the functional vitality of clonal NEC lines, serum growth factors triggered epithelial–mesenchymal transition and the immobilized Notch ligand Delta-like 1–activated downstream target genes. Moreover, cardiomyocyte coculture and engraftment in NOD-SCID (nonobese diabetic–severe combined immunodeficiency) mouse myocardium increased cardiac gene expression in NECs.
Conclusions:
A dynamic Notch injury response activates adult epicardium, producing a multipotent cell population that contributes to fibrosis repair.
Am Heart Assoc