Date of Award

5-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Bioengineering

Advisor

Gao, Bruce Z

Committee Member

Borg , Thomas K.

Committee Member

Dean , Delphine

Committee Member

Simionescu , Dan

Abstract

Significance
1) We have developed a hybrid TPEF-SHG imaging system with an onstage incubator for long-term living-cell imaging. Using the imaging system, the assembly of myosin filaments onto the myofibrils can be investigated without fluorescently labeling the specific proteins, which enabled us to study the dynamic process of the assembly and dedifferentiation of myofibrils in living cardiomyocytes without labeling any sarcomeric proteins for long time.
2) We observed the addition of new sarcomeres during myofibrillogenesis while neonatal cardiomyocytes were spreading on the substrate for up to 10 hours under the customized TPEF-SHG imaging system. New-sarcomere addition at both the ends and the sides of existing myofibrils and at the interstice of several separated myofibrils have been observed. Mature myofibrils were proposed to act as templates for the myofibrils forming adjacently. Our observation indicates that the assembly of myosin filaments onto a myofibril involves the initial redistribution of Z-body proteins to ultimately form mature Z-discs.
3) We dynamically investigated the dedifferentiation of cultured adult cardiomyocytes. The myofibrils were found to first shrink to shorter the sarcomere length, then the striated structure of myofibrils was wrecked from the cell ends and then to the whole cell. Results suggest that the striated patterns of different sarcomeric components were not affected simultaneously during dedifferentiation. The striated pattern of myosin filaments was wrecked first, which was followed by the wreck of the striated F-actin pattern, then alpha-actinin.
Value
1) The lateral assembly of myosin filaments onto the current mature myofibrils, and redistribution of Z-bodies while myosin filaments were assembling to the current myofibrils to cause the mature of myofibrils were first observed in our research, and which has extended the understanding on the myofibrillogenesis in cardiomyocytes.
2) Dynamic remodel of myofibrils and redistribution of sarcomeric proteins in the cultured adult cardiomyocyts under dedifferentiation may promote the understanding on the development of cardiomyopathy and provide methods to assess the developing heart diseases.

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