Previous Page  |  Table of Contents  |  Next Page

Wei-Shou Hu, Associate Fellow

Mechanistic Study of Hepatocyte Spheroid Formation

The in vitro formation of tissue-like structures from single cells is important for understanding the mechanism underlying the in vivo tissue and organ formation as well as for developing tissue engineering technologies. These researchers have developed culture systems that allow the formation of cell aggregates with enhanced functions compared to single cells and ultrastructure that resembles that of native liver tissue. These cell aggregates or spheroids are potential candidates for studies on tissue self-assembly and drug metabolism. In addition, spheroids can be used in extracorporeal liver-supporting devices. Animal trials of a bioartificial device in this laboratory have yielded promising results.

These researchers are working to construct a model concurrently with experiments. They are hoping that the results of the computations will provide some insight into the mechanism that cells utilize for tissue self-assembly. The models are based on solid and fluid mechanics and population balances, but they also incorporate principles applicable to biological systems. Two different culture systems for spheroid formation have been developed.

99/237

Spheroids can be assembled in static adherent cultures. When hepatocytes are inoculated on surfaces with certain properties, they form monolayers. Within one to two days, cells agglomerate to form cell aggregates that eventually become free-floating spheroids. The process involves the reorganization of the cytoskeleton and alterations in the force balance between cell-cell and cell-substratum interactions. In this laboratory, the capability exists to observe the formation of these tissue-like structures employing non-invasive methods. Confocal microscopy has been used to investigate the changes in cell shape and function during the aggregation of hepatocytes. Thus, an important element of this work is the visualization of cellular structures during real-time scanning of the tissue samples.

To that end, it is imperative to implement deconvolution methods. The contribution of out-of-focus light to the focal plane image is evident, especially in thick biological samples. Furthermore, other sources of image degradation, such as the microscope electronic circuits and the optical components, add artifactual information to the final image. Deconvolution methods have been widely used to improve image quality in fluorescent micrographs. Since the images are optical sections of a three-dimensional object, volume reconstruction can be used to visualize the internal and external structures of a tissue-like structure. This type of processing can lead to accurate data analysis and help to elucidate the mechanism of tissue formation and the concomitant change in cellular functions.

This information is available in alternative formats upon request by individuals with disabilities. Please send email to alt-format@msi.umn.edu or call 612-624-0528.

HOME | QUESTIONS | FEEDBACK
Employment | Events | Links | People | Programs | Publications | Support | Welcome