This invention relates to a culture system for the growth of epidermal keratinocyte stem cells comprising, a. processing the feeder cells economically with mitomycin C and b. providing a substratum in the form of such feeder cells c. achieving better growth stimulation of epidermal keratinocyte stem cell growth than -irradiated feeder cells characterized in that the optimal concentration of mitomycin C is combined further with respect to the dose per cell to derive a range of concentration-dose permutations.
