FIGURE 4.

Cardiogenic potential of transplanted MSCs. A: cluster of Ypos/BrdUpos cells (white arrowheads) located in infarct and border zones of treated hearts 12 wk after MSC implantation. Some of the transplanted MSCs do not exhibit BrdUpos signal (green), but maintain Ypos signal (red, yellow arrowheads). Conversely, another group shows BrdUpos signal (white arrows) and negative Y chromosome signal due to technique sensitivity. B: cluster of Ypos cells (green, white arrows) in the border zone of MSC-treated animals colocalizing with tropomyosin (red). C: evidence of cardiac differentiation in a panoramic view of an infarct border zone of MSC-treated hearts. Inset depicts one Ypos (green) myocyte costained with tropomyosin. High magnification of the square is shown in the inset. D: confocal microscopy analysis of the same cell by orthogonal section of a z-stack (arrows point the cell analyzed in xy-plane). E: two transplanted Ypos cells (green, arrows) coupled with the resident cardiomyocytes by expressing connexin-43 (orange). F: evidence of cardiac commitment in the transplanted cell by the colocalization of Ypos signal with the cardiac transcription factor Nkx2.5 (green, arrow). Nuclei were counterstained with DAPI in all of the immunofluorescence assays. G: cluster of BrdUpos cells (green) in the border zone of MSC-treated animals exhibiting colocalization with transcription factor GATA-4 (red, arrows). H: quantitation of transplanted cells according to Y chromosome cell tracking. Ypos cells show no preference in distribution according to LV areas (top). Importantly, at 12 wk posttransplantation, implanted MSCs showed commitment to repopulate the three major cardiac cell lineages and maintain a reservoir of nondifferentiated cells (bottom). Cell quantification per unit area for the Y chromosome (n = 6 for MSC-treated hearts, n = 4 for placebo-treated hearts). At least four tissue sections for infarct, border, and remote zone per heart were evaluated. Total area evaluated is 2,673.34 mm². CM, cardiomyocyte; End, endothelial cells; VSM, vascular smooth muscle. [From Quevedo et al. (290).]