FOXD3 and keratoconus: By Day 7, NC cells proliferated yielding a large number of cells surrounding the KC colonies (~30‐40 × 102/104 KC seeded), in agreement with recent results from our laboratory.17 Immunostaining showed that KC had formed colonies expressing K14 (not shown), while small, spindle‐shaped cells expressed Nestin (NES)—an intermediate filament protein that is expressed in both central nervous system (CNS) progenitors and NC stem cells19, 20–as well as other NC markers such as Sox10, FoxD3, and Pax3 but were lacking K14 (Figure 1b).