Soft Matter Seminar: Characterization of Cell Cycle Heterogeneity at the Single Cell Level
Tuesday, February 26, 2013 – 11:00am
Bioengineering Department, George Mason University
A central problem in biology is to interpret the cellular responses to their complex and dynamic microenvironments and appropriately link them with their molecular profiles. Traditional biochemical approaches provide stochastic measurements as ensemble average of cell communities reflecting the biological mechanisms operating within the dominant subpopulation. However, at high enough resolution, multiscale heterogeneity is typically observed among individual cells. Microfluidics technology offers an ideal approach to offset current limitations and study such complex systems with the ability to manipulate cells on the individual basis. Interfacing the advanced microfluidic tools and assays with biology, we are investigating the heterogeneous aspect of human mammary epithelial cells (HMECs) in terms of proliferation, migration and signaling.
Despite the high degree of regulatory mechanisms involved in cell replication, abnormal cell cycles become fundamentally responsible for diseases such as cancer, alzheimer’s, aging etc. In both in vivo and in vitro models of the cell cycle analysis, the presence of multiple biochemical factors as well as physical cell-cell interactions not only obscures the origins of heterogeneity but also the functional relationships between cell cycle variations and their physiological/pathophysiological responses. We have utilized the micropatterning strategy to spatially and physiologically control cellular interactions with each other as well as with their microenvironment in desirable formats. A simplified array of cells patterned on a standard polystyrene plate with defined cell morphology, adhesion area and cell-to-cell spacing was developed to individually trigger the multitude of factors and correlate them with respective cellular responses. Through live cell imaging of the cell cycle and division (utilizing S/G2/M
phase FUCCI fluorescent reporter), we have identified temporal differences in the cell cycle progression rates of HMECs acquired as a result of 1) Attachment area of cells with the tissue culture substrate and 2) Loss of contact inhibition due to intracellular interactions. Clonal population of cells originated from a single parent cell and synchronized to trigger the onset of their cell cycle acquired marked differences in their cycles when in contact with neighboring cells. By knocking out the transmembrane adhesion protein ‘E-cadherin’ on the cell surface, we anticipate to further narrow down the factors contributing to the loss of proliferation due to contact inhibition. These findings can be directly applied as a fundamental basis to study cancer cell dormancy and the interaction dynamics of metastatic circulating tumor cells and also provide a novel perspective for understanding cancer phenotypes undergoing uncontrolled cell growth.