Can mesenchymal stem cells induce tolerance to cotransplanted human embryonic stem cells?

Abstract

Mesenchymal stem cells (MSCs) are reported to be immune privileged. We assessed whether their transplantation (Tx) could create a suppressive microenvironment mitigating rejection of coinjected human embryonic stem cells (hESCs). Three weeks after ligation-induced myocardial infarction, 40 immunocompetent rats received 150 microl of cardiac-specified hESCs (5 x 10(6)), MSCs (5 x 10(6)), hESC + MSC (5 x 10(6) for each), or control medium. Two months after Tx, left ventricle (LV) function was assessed by echocardiography, and hearts were processed for the detection of human cells by immunostaining and quantitative RT-PCR, patterns of rejection, fibrosis, and angiogenesis. Two months after Tx, LV ejection fraction (LVEF) was significantly higher in the ESC and ESC + MSC groups compared with controls. There were few engrafted cells, which expressed markers of endothelial, smooth muscle, and ventricular cardiac cells, particularly in the MSC group. Hearts of all groups demonstrated a similar infiltration by CD4(+) and CD3(+) cells but MSC-Tx resulted in a greater infiltration of FoxP3 compared with the control and ESC-alone groups. No teratoma was observed. Thus, cotransplantation of ESCs and MSCs provided better functional preservation compared with single-cell treatment alone. However, there was only modest evidence for an immunosuppressive effect of coinjected MSCs and their beneficial effects seemed rather mediated by trophic effects on the host tissue.

Figures

Figure 1

Immunostaining of cryosections using an anti-human lamin antibody: (a) mesenchymal stem cell (MSC), (b) human embryonic stem cell (hESC), and (c) MSC + hESC cell-engrafted myocardium. Images were acquired in confocal microscopy (green channel 515–535 nm, ×63). Bar = 10 µm.

Figure 2

Immunostaining of cryosections using markers of differentiation: an anti-smooth muscle cells antibody in (a) mesenchymal stem cell (MSC) group, (b) an anti-CD31 antibody in MSC group, (c) and anti-myosin heavy chain antibody in MSC group. Images were acquired in confocal microscopy (green channel 515–535 nm, ×63). Bar = 10 µm.

Figure 3

Immunostaining of cryosections using markers of rejection against (a) CD3, (b) CD4, and (c) regulatory CD4CD25 FoxP3-expressing lymphocytes in each group. Images were acquired in confocal microscopy (×20). Bar = 50 µm.

Figure 4

Immunostaining of cryosections using markers of fibrosis (Sirius red): from control (a), human embryonic stem cell (hESC) (b), mesenchymal stem cell (MSC) (c), and MSC + hESC groups (d). Pictures were taken in the core of the infarct area. Images were acquired in microscopy (×5). Bar = 1 mm.

Figure 5

Immunostaining of cryosections using markers of angiogenesis (RECA): from control (a), human embryonic stem cell (hESC) (b), mesenchymal stem cell (MSC) (c), and MSC + hESC groups (d). Pictures were taken in the core of the infarct area. Images were acquired in microscopy (×10). Bar = 0.5 mm.