Wnt/β-catenin signaling promotes expansion of Isl-1–positive cardiac progenitor cells through regulation of FGF signaling
Ethan David Cohen, … , Douglas J. Epstein, Edward E. Morrisey
Ethan David Cohen, … , Douglas J. Epstein, Edward E. Morrisey
Published July 2, 2007
Citation Information: J Clin Invest. 2007;117(7):1794-1804. https://doi.org/10.1172/JCI31731.
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Research Article Cardiology

Wnt/β-catenin signaling promotes expansion of Isl-1–positive cardiac progenitor cells through regulation of FGF signaling

Abstract

The anterior heart field (AHF), which contributes to the outflow tract and right ventricle of the heart, is defined in part by expression of the LIM homeobox transcription factor Isl-1. The importance of Isl-1–positive cells in cardiac development and homeostasis is underscored by the finding that these cells are required for cardiac development and act as cardiac stem/progenitor cells within the postnatal heart. However, the molecular pathways regulating these cells’ expansion and differentiation are poorly understood. We show that Isl-1–positive AHF progenitor cells in mice were responsive to Wnt/β-catenin signaling, and these responsive cells contributed to the outflow tract and right ventricle of the heart. Loss of Wnt/β-catenin signaling in the AHF caused defective outflow tract and right ventricular development with a decrease in Isl-1–positive progenitors and loss of FGF signaling. Conversely, Wnt gain of function in these cells led to expansion of Isl-1–positive progenitors with a concomitant increase in FGF signaling through activation of a specific set of FGF ligands including FGF3, FGF10, FGF16, and FGF20. These data reveal what we believe to be a novel Wnt-FGF signaling axis required for expansion of Isl-1–positive AHF progenitors and suggest future therapies to increase the number and function of these cells for cardiac regeneration.

Authors

Ethan David Cohen, Zhishan Wang, John J. Lepore, Min Min Lu, Makoto M. Taketo, Douglas J. Epstein, Edward E. Morrisey

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Figure 2

Loss of Wnt/β-catenin signaling in the AHF leads to decreased right heart development and loss of Isl-1 progenitors.

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Loss of Wnt/β-catenin signaling in the AHF leads to decreased right hear...
(A and B) SM22α-cre is active in the AHF, demonstrated by lacZ expression throughout the outflow tract (brackets) and in the pharyngeal mesodermal apex (dotted lines) of SM22α-cre × R26R mice at E9.5 and E10.5. (C–H) Immunofluorescent staining for Isl-1 and β-galactosidase expression shows extensive overlap within the outflow tract (arrowheads) and AHF (dotted lines) at E9.5. Loss of β-catenin using the SM22α-cre transgenic line caused hypoplastic right ventricle as assessed by scanning electron microscopy (I and J) and ink injections of wild-type (K) and SM22cre/Catnbflox/flox (SM/Catfl/fl) embryos (L) at E9.5. Histological sectioning at multiple levels showed the reduction in right ventricle size (arrows) at E9.5 in SM22cre/Catnbflox/flox (O and P) compared with wild-type embryos (M and N). (Q) Right ventricular diameter in SM22cre/Catnbflox/flox compared with wild-type embryos. (R–T) To assess changes in Isl-1 AHF progenitors, wild-type and SM22cre/Catnbflox/flox embryos were immunostained for Isl-1 protein expression. SM22cre/Catnbflox/flox mutants have severely reduced numbers of Isl-1 AHF progenitors in the outflow tract at E9.5. (U–AA) Isl-1 and Ki-67 double immunofluorescence was performed to determine changes in proliferation in AHF progenitors. Reduced Ki-67 staining in Isl-1–positive cells within the outflow tract was observed in SM22cre/Catnbflox/flox mutant embryos (arrowheads). (AA) Quantitation showed an almost 50% reduction in Isl-1 AHF progenitor proliferation. **P < 0.005. Scale bars: 100 μm (A–J); 500 μm (M–P); 125 μm (R and S); 75 μm (U–Z).