At day-63 of hair follicle histoculture,the ND-GFP-expressing stem cell follicles had a large increase in relative fluorescence intensity and fluorescent area (p < 0.001 for both). The large increase in ND-GFP expression of the stem cells indicates their extensive proliferation and activity, as well as the very long-term viability of the follicles in Gelfoam1 histoculture. Thus ND-GFP-expressing stem cells increased over the 63-day histoculture period even though hair shaft elongation appeared to cease by day20 (Figs 2 and 3).