The research objective of this award is to use biomedical engineering tools to assess the properties and responses of biological cells to mechanical forces. In particular, the characterization of cells that are cultured in suspension, without a specific attachment surface, will be performed to assess how cells self-regulate under these conditions. Studies conducted under this award involve refining techniques for culturing and applying mechanical stimuli to cell aggregates that are maintained in suspension. Both material properties (e.g., how solid-like or fluid-like the cells are; how stiff the cells are) and molecular responses (e.g., changes in active responses by the cell) will be examined. Such characteristics will be compared and contrasted to the behavior of the cells when plated on more conventional substrates to determine the differences in these two types of culture.

If successful, these studies will contribute to the knowledge of how cells sense and respond to physical forces, and additionally provide insight into how normally adherent cells behave when they are not influenced by a substrate or scaffold. These results may additionally be useful in engineering tissue constructs with different properties compared to those constructed using specially-designed surfaces. The educational plan focuses on multiple paths, including encouraging undergraduates to become more involved in research projects, as well as public school outreach, where K-12 students will be introduced to scientific research and equipment and encouraged to performed exploratory experiments. Both outreaches will be guided by the topic of the research area of this award. These initiatives will help foster the understanding of and hopefully, the appreciation for, contemporary biomedical engineering topics and methods

Project Report

The overall scientific goal of this project was to characterize the effects of cell-cell contact on cellular properties, focusing on skin cells, called keratinocytes, and heart muscle cells, called cardiomyocytes. To achieve this goal, we cultured cells in suspension (no contact to external stiff surfaces, or substrates) as a sheet and developed a new method called "partial-lifting" whereby part of a monolayer of cells could be detached from a substrate. We found that when cell-substrate interactions are weakened or absent, cell-cell interactions become more pronounced - for example, certain proteins appear to increase their numbers at locations where cell-cell contact occurs (called cell-cell junctions). We also found that cells may remain viable in suspension so long as they maintain contact with other cells, and that even when detached from a substrate, certain cellular adaptations to mechanical stretch remain intact. The primary conclusions we can draw from our work are that (1) cell-cell junctional contacts appear capable of modulating mechanical signals, (2) cells grown in suspension retain many of their properties but alter others, such as the distribution of certain junctional proteins, and (3) cell-cell contacts form key pathways to cellular regulation that deserves further study. This study resulted in several publications and will hopefully direct some research groups to examine the potential of using cell-cell junctional approaches as a new or complementary method for developing tissue-engineered constructs, examining cell suspension processes such as tumor metastasis, and understanding basic cellular physiology. In addition to the technical work, the project also focused on various broader impacts. We were able to engage two different K-12 programs for underserved groups by developing a remote-lab presentation, whereby we would make demos and provide lectures to K-12 students using videoconferencing. While this method is promising, we learned that students prefer hands-on work, so in some cases, we supplemented the videoconference with demos by sending the groups some supplies. We were also able to support undergraduates who wanted research experience. Finally, we were able to incorporate some of what we learned during outreach into courses, such as inclusion of demonstrations during lectures and refinement of a lab course to focus on more relevant topics.

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Columbia University
New York
United States
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