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 (λex 340 nm, λem 360–660 nm; λex 365 nm, λem 400–700 nm; λex 420 nm, λem 440–800 nm) and excitation scans (λex 200–360 nm; λem 380 nm, λex 240–430 nm; λem 450 nm, λex 250–460 nm, λem 480 nm; λex 270–500 nm, λem 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.