Researchers have found that injecting aorta-derived stem cells into the hearts of dystrophin-deficient mice prevents the onset of dilated cardiomyopathy (DCM), raising hopes of a potential new treatment approach to prevent or reverse the condition in human Duchenne muscular dystrophy.
"This is the first report of stem cell therapy yielding functional benefit in the dystrophin-deficient heart," say Suzanne Berry (University of Illinois, Urbana, USA) and team.
As reported in Stem Cells Translational Medicine, injection of wild-type aorta-derived mesoangioblasts (ADMs) containing a functional copy of the dystrophin gene, significantly improved heart function compared with deficient mice injected with saline (controls).
Echocardiography revealed no significant differences from baseline in heart wall or septum thickness or ventricular dilation in the ADM-injected mice and no decrease in heart function 5-6 weeks after injection. By contrast, significant decreases in the thickness of the left ventricular wall and an increase in the diameter of the left ventricle at both diastole and systole was observed in the control mice, as well as a large increase in end-diastolic volume, consistent with the development of dilated cardiomyopathy.
Injection of ADMs also induced generation of dystrophin-expressing cardiomyocytes, angiogenesis (as indicated by increased CD31 expression), and the proliferation of cells positive for the neurofilament protein nestin, while no such benefits were observed in the control mice.
The team also observed nestin-striated cells that expressed cardiac troponin I in the hearts of four of the five ADM-injected mice, while this was observed in only one of four saline-injected hearts.
"This is the first report of nestin+ striated cells in dystrophin-deficient heart and in response to nonischemic damage, and it indicates that they may be involved in the delay in DCM observed with ADM injection," say Berry and team.
However, the mice were only 5 weeks old at the time of transplantation, when skeletal muscle pathology and DCM would not have yet developed in the deficient mice, given that onset usually occurs 15 weeks after birth in this animal model, explains the team.
To test whether ADMs alleviate existing cardiomyopathy, the team injected the ADMs into aged (14-16 months) dystrophin-deficient mice with advanced fibrosis.
No improvement from baseline in heart function was detected on echocardiography among the aged mice 10 weeks after ADM-injection. Instead, these mice exhibited significant ventricular dilation, consistent with the development of dilated cardiomyopathy, reports the team. Furthermore, no increases in dystrophin-expressing cells, angiogenesis, or nestin-positive cells were detected in the mice.
"The cardiac microenvironment may alter the fate of donor stem cells," says the team.
"In particular, fibrosis may inhibit ADM migration and survival, and integration with the myocardium."
"Timing of ADM transplantation is critical, as these events do not occur following injection into aged dystrophin-deficient heart where pathology is present," concludes the team.
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