C-kit+ Cardiac stem cells alleviate post-myocardial infarction left ventricular dysfunction despite poor engraftment and negligible retention in the recipient heart.

Kyung U Hong,Xiaoping Zhu,Roberto Bolli,Yiru Guo,Michael J Book,Aruni Bhatnagar,Junjie Du,Qian-Hong Li,Yibing Nong,Pengxiao Cao,Tareq Al-Maqtari,Bathri N Vajravelu,Joshua M Hare

doi:10.1371/journal.pone.0096725

Abstract

Although transplantation of c-kit+ cardiac stem cells (CSCs) has been shown to alleviate left ventricular (LV) dysfunction induced by myocardial infarction (MI), the number of exogenous CSCs remaining in the recipient heart following transplantation and their mechanism of action remain unclear. We have previously developed a highly sensitive and accurate method to quantify the absolute number of male murine CSCs in female recipient organs after transplantation. In the present study, we used this method to monitor the number of donor CSCs in the recipient heart after intracoronary infusion. Female mice underwent a 60-min coronary occlusion followed by reperfusion; 2 days later, 100,000 c-kit+/lin- syngeneic male mouse CSCs were infused intracoronarily. Only 12.7% of the male CSCs present in the heart immediately (5 min) after infusion were still present in the heart at 24 h, and their number declined rapidly thereafter. By 35 days after infusion, only ∼1,000 male CSCs were found in the heart. Significant numbers of male CSCs were found in the lungs and kidneys, but only in the first 24 h. The number of CSCs in the lungs increased between 5 min and 24 h after infusion, indicating recirculation of CSCs initially retained in other organs. Despite the low retention and rapid disappearance of CSCs from the recipient heart, intracoronary delivery of CSCs significantly improved LV function at 35 days (Millar catheter). These results suggest that direct differentiation of CSCs alone cannot account for the beneficial effects of CSCs on LV function; therefore, paracrine effects must be the major mechanism. The demonstration that functional improvement is dissociated from survival of transplanted cells has major implications for our understanding of cell therapy. In addition, this new quantitative method of stem cell measurement will be useful in testing approaches of enhancing CSC engraftment and survival after transplantation.

Highlights

A unique resident c-kit+ cardiac stem cell (CSC) population which is able to give rise to cardiovascular progenies has been previously identified and characterized in adult myocardium [1,2,3,4,5,6,7,8]
The number of CSCs in the lungs increased at 24 h vs. 5 min (Fig. 2; Table 1), indicating that many CSCs that were retained in the heart and other organs at 5 min after infusion became dislodged and entered the venous circulation in the ensuing hours
Intracoronary infusion of 100,000 CSCs resulted in low initial retention (i.e., 39,797616,482 cells at 5 min) in the heart with subsequent rapid disappearance of the cells

Summary

Introduction

A unique resident c-kit+ cardiac stem cell (CSC) population which is able to give rise to cardiovascular progenies has been previously identified and characterized in adult myocardium [1,2,3,4,5,6,7,8]. In a recent phase I clinical trial (SCIPIO), CSCs isolated from patients with ischemic cardiomyopathy have been found to significantly improve cardiac function, functional status, and quality of life when transplanted back into the patients via intracoronary infusion [14,15], clearly demonstrating the utility of these cells for the treatment of ischemic heart failure. In a mouse model of acute MI, Tang et al reported that over 90% of the transplanted mesenchymal stem cells were lost during the first 24 h, and only 3.6% remained in the heart by 7 days post-transplantation [16]. In order to devise and test new approaches in CSC therapy, it is necessary to accurately monitor and compare the engraftment, retention, and fate of transplanted CSCs and correlate these variables with changes in cardiac function. Most of the methods currently used to estimate or monitor the number of transplanted cells (which involve histological, in vivo imaging, or PCR-based techniques) permit only measurement of the relative changes in the transplanted cell number and do not provide information regarding the absolute number of cells present in a recipient organ of interest at a given time

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