Resident c-kit+ cells in the heart are not cardiac stem cells

Nishat Sultana,Chen-Leng Cai,Dongtak Jeong,Wei Sheng,Lei Bu,Lu Zhang,Guo-Ying Huang,Weibin Cai,Bin Zhou,Jianyun Yan,Mingjiang Xu,Roger J Hajjar,Jiqiu Chen,Anne Moon,Shegufta Razzaque

doi:10.1038/ncomms9701

Abstract

Identifying a bona fide population of cardiac stem cells (CSCs) is a critical step for developing cell-based therapies for heart failure patients. Previously, cardiac c-kit+ cells were reported to be CSCs with a potential to become myocardial, endothelial and smooth muscle cells in vitro and after cardiac injury. Here we provide further insights into the nature of cardiac c-kit+ cells. By targeting the c-kit locus with multiple reporter genes in mice, we find that c-kit expression rarely co-localizes with the expression of the cardiac progenitor and myogenic marker Nkx2.5, or that of the myocardial marker, cardiac troponin T (cTnT). Instead, c-kit predominantly labels a cardiac endothelial cell population in developing and adult hearts. After acute cardiac injury, c-kit+ cells retain their endothelial identity and do not become myogenic progenitors or cardiomyocytes. Thus, our work strongly suggests that c-kit+ cells in the murine heart are endothelial cells and not CSCs.

Highlights

Identifying a bona fide population of cardiac stem cells (CSCs) is a critical step for developing cell-based therapies for heart failure patients
Cardiac c-kit-positive (c-kitþ ) cells were the first population of putative CSCs described as being negative for the blood lineage marker (LinÀ ) in the adult rat heart, along with possessing selfrenewing, clonogenic and multipotent characteristics7,13,14. c-kitþ cardiac cells were shown to be necessary and sufficient for myocardial regeneration after cardiac injury in rats and mice[15]
What is the exact nature of cardiac c-kitþ cells? Do these cells give rise to multiple cardiac lineages during development and after heart failure? Do the benefits of c-kitþ cell-based therapies arise from an ability to differentiate into cardiomyocytes, or do c-kitþ cells generate paracrine factors or a paracellular environment that promotes recovery? Given that c-kitþ cells are being clinically tested on human patients with ischaemic cardiomyopathy[21,22,23], fully addressing these questions is critical

Summary

P90 97

1 mm (black) and 100 mm (white). in the infarcted region (Fig. 5c–f). Examination of adult c-kitMerCreMer/þ ;cTnTnlacZ-H2B-GFP/þ mice after LAD ligation (3–5 months old, n 1⁄4 3, Fig. 6d) revealed o20 cTnTH2B-GFP-positive cells per heart (B0.002% of total myocardial cells) throughout the injured region (Fig. 6e). These cells may be derived from uncommitted cells originally expressing c-kit, or they could be cardiomyocytes that express both c-kit and cTnT due to a rare stochastic event To explore these possibilities, we examined cTnTMerCreMer/þ ;c-kitnlacZ-H2B-GFP/þ adult mouse hearts (2–4 months old, uninjured) after tamoxifen injection for 2 consecutive days (days 1 and 2). This is probably due to much higher levels of cTnT expression than c-kit expression and/or to differential sensitivity of the reporters to Cre-mediated recombination

Tnnt2H2B-GFP

Methods