| Myocardial infarction, which results from the loss of irreplaceable contractileelements, is one of the main causes of morbidity and mortality in the world. In recentyears, the emerging field of stem cell-based therapy offers promising alternatives.However, direct cellular myoplasty showed certain obvious shortcomings: Firstly, ininfarcted region, oxidatie stress and serious inflammatory effect, as well as loss ofcells after injection, cause low survival and retention rates for trsplanted cells.Secondly, less paracrine factors from stem cells result in limited early myocardialprotection. Thirdly, differentiation of stem cells is questionable, which weakens thelongterm myocardial protection.Recently, the method of gene modification was used to improve stem cell-basedtheraprutical effect for myocardial infarction. Heme Oxygenase-1(HO-1) participatesin defense mechanisms against agents that may induce oxidative injury. HO-1mightalso protect against oxidative stress by catalyzing their degradation to CO andbilirubin, which, themself, have antioxidant properties. Meanwhile, gene modificationis also involved in further research on sustaining intension of stem cells anddifferentiation potential. Multiple Fusion technology of repoter genes provides amediate panel in which several imaging methods can be implemented to evaluatereal-time and all-round tracking for the transplanted cells. It definetely holds greatapplication values.METHODS: In Part1, rabbits were treated with adipose tissue-derived stemcells (ADSCs) transduced with HO-1(Group A), treated with non-transduced ADSCs(Group B), or injected with phosphate buffered saline (Group C)14days afterexperimental MI was induced, during which autologous ADSCs were obtainedsimultaneously. Four weeks after transplantation, echocardiography and biopsy of the heart specimens were performed to evaluate the treating effect and differentiationpotential. In Part2, an optimized method was developed for efficient transduction ofADSCs with a lentiviral vector carrying a triple-fusion reporter gene that consists offirefly luciferase, monomeric red fluorescence protein and truncated thymidine kinase(fluc-mrfp-ttk). The transduced ADSCs (TF-ADSCs) cell lines were established andassessed on biological performances. In Part3, TF-ADSCs were transplanted intoinfarcted heart with fibrin scaffolds. In vivo cell retention was tracked bybioluminescence imaging (BLI) and micro PET/CT imagings. Histological assessmentwas performed for regeneration potentials.RESULTS:1) Echocardiography showed significant improvements in systolicfunctions and left ventricular dimensions of the cell-treated group. Biopsy of the heartspecimens revealed that the cells existing separately and lumen-like structureorganizations stained positive for cardiac troponin T, von Willebrand factor antigenand α-smooth muscle actin. Apart from improvement in angiogenesis and scar area,higher connexin43expression and greater cardiac sympathetic nerve sprouting wereobserved in the transduced cell-treated group.2) Lentiviral transduction didn't influence cell functions. In vitro imaginganalysis showed robust linear correlation between cell numbers and BLI signals(R2=0.99) as well as between cell numbers and radiotracer uptakes (R2=0.98).TF-ADSCs could be visualized in the heart under both BLI and PET/CT imaging,contributing to cardiomyocytes regeneration and angiogenesis in the implanted areas.Compared with BLI monitoring, PET/CT data provided precise localization for cellretention.CONCLUSIONS:With the development of gene modification on improvementand evaluation for stem cells-based therapy, a better insight to optimizing cellularcardiomyoplasty can be established. It can also provide a standard and positivemethodology by which novel treatment mechanism, differentiation potential andefficiency evaluation will be elucidated in the future.
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