To evaluate the degree of cellular dedifferentiation, subculture of chondrocytes was conducted on a surface coated with collagen type I at a density of 1.05 mg/cm2. In the primary culture, most of the cells were round in shape on the collagen (CL) substrate, whereas fibroblastic and partially extended cells were dominant on the polystyrene plastic (PS) substrate. Stereoscopic observation revealed that the round-shaped cells on the CL substrate were hemispherical with nebulous and punctuated F-actin filaments, whereas the fibroblastic cells on the PS substrate were flattened with fully developed stress fibers. This suggested that cell polarization was suppressed during culture on the former substrate. Although serial passages of chondrocytes through subcultures on the CL and PS substrates caused a decrease in the number of round-shaped cells, the morphological change was appreciably suppressed on the CL substrate, as compared with that on the PS substrate. It was found that only round-shaped cells formed collagen type II, which supports the view that cellular dedifferentiation can be suppressed to some extent on the CL substrate. Three-dimensional cultures in collagen gel were performed with cells isolated freshly and passaged on the CL or PS substrate. Cell density at 21 days in the culture of cells passaged on the CL substrate was comparable to that in the culture of freshly isolated cells, in spite of a significant reduction in cell density observed in the culture of cells passaged on the PS substrate. In addition, histological analysis revealed that the expression of glycosaminoglycans and collagen type II was of significance in the collagen gel with cells passaged on the CL substrate, and likewise in the gel with freshly isolated cells. This indicated that the CL substrate could offer a monolayer culture system for expanding chondrocyte cells.

Understanding the fundamental mechanisms underlying the cellular response to topographical surface features will extend our knowledge regarding the regulation of cell functions. Analyzing the cellular response to different topographical features, over multiple temporal and spatial scales, is central to understanding and guiding several biological functions. We used micropatterned substrates with convex and concave architectures to evaluate the behaviors of human epithelial cells on these substrates.