Growth curve of primary KCs.

<p>The growth curve revealed an “S” shape. The detention period, in which the proliferation speed of cells was slow, was between 2–4 days. The exponential phase of growth, meaning the cells rapidly proliferated, was 4–10 days, and the following 4 days were the platform period, when the cells achieved saturation density. The data are expressed as mean values obtained by three determinations.