| Duchenne Muscular Dystrophy(DMD)is an X-linked recessive inhereditary discorder,caused by frame-disrupting mutations in the DMD gene,manisfested as body-wide progressive muscle wasting.Recently,it has been possible to treat skeletal muscles,however,no effective treatment is available for cardiomyopathy,which is the main cause accounting for the mortality of DMD patients.The clinical data indicate that DMD patients exihibit severe epicardical fibrosis and dysfunctions in the heart,whereas WT1~+cell is a type of cells primarily localized in epicardium with multiple differentiation potentials and is also involved in cardiac injury and remodeling.WT1~+cells have been shown to contribute to myocardial ischemic perfusion and other cardiovascular diseases,but their roles in DMD remain elusive.Here,we investigate the relationship between WT1~+cells and cardiac functions in DMD models.In this study,we used two different DMD mouse models including aged mdx and telomerase-knockout mdx mice and explored the correlation between WT1~+cells and cardiac functions.The results demonstrated that abnormally activated WT1~+cells contributed to the severe fibrotic conditions in mdx hearts,resulting in cardiac dysfunction.We monitored the distribution,localization and differentiation of WT1~+cells in telomerase-knockout mdx mice and the results showed that WT1~+cells co-localized with fibroblasts but not with smooth muscle cells or endothelial cells in mdx hearts.It suggests that WT1~+cells demonstrate enhanced differentiation capacities to fibroblasts.To confirm the involvement of WT1~+cells in DMD cardiac pathologies,we used Thymosin?4(T?4),a knwon activator of WT1~+cells,to stimulate the activation of WT1~+cells in mdx hearts.WT1~+cells were significantly elevated in telomerase-knockout mdx and doxorubicin-induced mdx mice after repeated intraperitoneal injections of T?4.Strikingly,T?4-treated mdx mice showed signifinantly improved cardiac funtions with reduced fibrosis.To determine the effect of T?4 on WT1~+cells in mdx hearts,we examined the co-localization of WT1~+cells with fibroblasts and smooth muscle cells.The results revealed that the co-localization of WT1~+cells with fibroblasts was significantly decreased,implying that T?4probably switches the differention potential of WT1~+cells.Similar results were consistenly obtained with in vitro tests in primary epicardium cells derived from DMD mice.In addition,it was shown that DMD hearts showed more severe DNA injuries than normal volunteers.To determine if there is any beneficial effect of T?4 on DNA damage,we measured the expression of biomarker proteins associated with DNA damage and the results indicated decreased levels of DNA damage marker proteins.Examination on peripheral muscles of T?4-treated mdx mice revelaed significantly improved pathological conditions,suggesting that T?4 not only protects hearts but also skeletal muscles in DMD conditions.Also,levels of serum T?4 significantly declined in DMD patients compared to normal controls,suggesting that T?4 can be a potential candidate drug for DMD.In summary,our study demonstrated that the abnormal activation of WT1~+cells contributes to cardiac fibrosis and resultant cardiac dysfunctions.T?4 can protect DMD hearts by promoting WT1~+cell proliferation and shifting its differentiation potential.Furthermore,consideringa suitable in-vitro model system is urgently required for DMD cardiomyopathic studies,we established a cardiosphere-derived stem cell line,derived from adult mouse cardiac explants.Systemic evaluation and characterization on its proliferation capacity,chromosome stability,and gene expression profiling and differentiation potentials in vitro proved its cardiosphere-derived stem cell properties.This cell line will provide a handy in vitro model for studies on DMD cardiomyopathy and and other heart-related diseases. |
PDF Full Text Request