Native cellular fluorescence identifies terminal squamous differentiation of normal oral epithelial cells in culture: a potential chemoprevention biomarker

Native cellular fluorescence (NCF) is being investigated as an intermediate endpoint biomarker for chemoprevention. Oral epithelial cells were cultured under three conditions to identify a spectral pattern for epithelial differentiation: cells maintained in serum-free keratinocyte growth medium were the least differentiated (KGM cells); cells switched to DMEM/F12 plus 10% FCS were intermediate in differentiation (DMEM/F12/FCS cells); DMEM/F12/FCS cells switched to serum-free DMEM/F12 plus 0.8 M NaCl to induce cornified envelopes were the most differentiated (DMEM/F12/NaCl cells). The differentiation status was characterized using immunohistochemistry and electron microscopy. NCF analysis was able to distinguish terminally differentiated epithelial cells (DMEM/F12/NaCl) from those less differentiated cells (KGM, DMEM/F12/FCS) in several emission (λ ex 340 nm, λ em 360–660 nm; λ ex 365 nm, λ em 400–700 nm; λ ex 420 nm, λ em 440–800 nm) and excitation scans (λ ex 200–360 nm; λ em 380 nm, λ ex 240–430 nm; λ em 450 nm, λ ex 250–460 nm, λ em 480 nm; λ ex 270–500 nm, λ em 520 nm). The ability to discriminate terminal differentiation in this in vitro model supports the concept of using NCF as an intermediate biomarker to monitor in vivo mucosal differentiation.