Abstract
We recently described a murine embryonic stem cell (ESC) line engineered to express the activated Notch 4 receptor in a tetracycline (doxcycline; Dox) regulated fashion (tet-notch4 ESCs). Notch 4 induction in Flk1(+) hematopoietic and vascular progenitors from this line respecified them to a cardiovascular fate. We reasoned that these cells would be ideal for evaluating the contribution of the cardiomyocyte and vascular lineages to the functional improvement noted following stem cell transplantation in infarcted hearts. Flk-1(+) Tet-notch4 cells from d 3 embryoid bodies exposed to doxycycline (Dox(+)) were compared to uninduced (Dox(-)) Flk-1(+) cells. Mice underwent transplantation of 5 x 10(5) Dox(+) cells, Dox(-)cells, or an equal volume of serum-free medium after surgically induced myocardial infarction. The mean ejection fraction was 59 + or - 15, 46 + or - 17, and 39 + or - 13% in the Dox(+), Dox(-), and serum-free medium groups, respectively (P<0.05 for the differences among all 3 groups). Immunohistochemistry of hearts injected with Dox(+) grafts expressed myocardial and vascular markers, whereas grafts of Dox(-) cells expressed primarily vascular markers. We conclude that cardiovascular progenitors are more effective than vascular progenitors in improving function after myocardial infarction. The transplantation of appropriate cell types is critical for maximizing the benefit of cardiovascular cell therapy.-Adler, E. D., Chen, V. C., Bystrup, A., Kaplan, A. D., Giovannone, S., Briley-Saebo, K., Young, W., Kattman, S., Mani, V., Laflamme, M., Zhu, W.-Z., Fayad, Z., Keller, G. The cardiomyocyte lineage is critical for optimization of stem cell therapy in a mouse model of myocardial infarction.