Proliferation and differentiation characteristics of normal human squamous mucosal cells of the upper aerodigestive tract

Normal human squamous mucosal cells of the soft palate, buccal surface, epiglottis, hypopharynx, floor of the mouth, and tongue were cultured in vitro in serum-free medium. In medium MCDB 153 containing epidermal growth factor, insulin, bovine pituitary extract, and 0.1 or 2.0 mmol/L Ca⁺⁺, squamous mucosal cells double every 24 hours. These cells then can be induced to arrest their proliferation reversibly by treatment with transforming growth factor-β or ethionine, and they can irreversibly growth-arrest during senescence or when cultured in growth factor-deficient medium containing 2 mmol/L Ca⁺⁺. The latter medium also induces differentiation, as does culture of cells in serum-containing medium. Serum-containing medium furthermore promotes extensive cell stratification and the formation of multilayered squamous mucosal tissue specimens that can be removed intact by Dispase treatment. These specimens represent potential autogenous mucosal grafts that can be used in patients who require reconstructive surgery of the oral cavity and oropharynx. Normal human squamous mucosal cells therefore closely resemble keratinocytes derived from the epidermis in the mechanisms that regulate proliferation and differentiation. This model cell system should facilitate future studies on upper aerodigestive tract squamous mucosal cell physiology and pathophysiology.