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Tissue cells bind to extracellular matrix (ECM), and this attachment to ECM plays an essential role in their growth, function, and even survival. Furthermore, the geometry of ECM is known to play an additional role in regulation for these cells to proliferate and differentiate so that tissues with normal morphologies can be formed or maintained. We attempted to culture fibroblast, osteoblast, and bone marrow derived cells in previously described microchannel arrays and newly created micropit arrays, both coated with ECM protein collagen, to examine usefulness of microfabricated structures for elucidating 'what is geometry?' for cells. Cells were inseminated in the well in front of a microchannel array and their movement and stretching behavior against the microchannel array including the entrance and exit terraces were observed using a microscope-TV camera-time lapse video recorder system for 24 hours. Cells entered into the entrance terrace and showed active motions including extending pseudopodia into the channels and whole cell passage through the channels, and fully stretched in the entrance terrace in 8 hours or so. Those cells, however, voluntarily detached themselves from the area in another 8 hours or so probably because of worsening condition of nutrient supply there. Micropit arrays used in the present study consist of a regular arrangement of circular or square pits of diameter or side length of 25, 50, 100, 200, 400, and 600 micrometer and depth of 10 micrometer with one size per array or chip. The total area of the pits was designed to be equal to the rest surface area. After four days of incubation of bone marrow derived cells, the total number of cells and the number of cells in the pits were counted. The former and the ratio of the latter to the former appeared to become maximal when the pits of diameter or side length of 100 and 50 micrometer were used, respectively.
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