Khaw P T, Schultz G S, MacKay S L, Chegini N, Rotatori D S, Adams J L, Shimizu R W
Department of Obstetrics and Gynecology, University of Florida, Gainesville 32610-00294.
Invest Ophthalmol Vis Sci. 1992 Nov;33(12):3302-6.
Human corneal epithelial cells are normally shed from the apical surface and replaced primarily by mitosis of basal cells. Growth factors may regulate this process, but the sources for the growth factors have not been fully established. One potential source for growth factors is tear fluid, and epidermal growth factor (EGF) has been detected in the lacrimal gland and in tears. However, the hydrophilic structure and size of growth factors such as EGF may limit penetration to basal layers of intact epithelium. It is possible that turnover of basal human corneal epithelial cells might be regulated by growth factors acting by an autocrine mechanism. To determine if human corneal epithelial cells synthesize a potential autocrine growth factor, the authors analyzed human corneal epithelial cells for transforming growth factor-alpha (TGF-alpha) messenger RNA and protein, a growth factor that is structurally related to EGF and binds to the EGF receptor. Radioimmunoassay of human corneal epithelial cell cultures detected substantial levels of immunoreactive TGF-alpha (3 ng/10(6) cells). Immunohistochemical staining of human corneas also revealed the presence of immunoreactive TGF-alpha in the corneal epithelium. Northern hybridization with a 32P-labeled complementary DNA probe for TGF-alpha generated a single intense band at 4.4 kilobases, indicating the presence of TGF-alpha messenger RNA in cultured human corneal epithelial cells. These results support the hypothesis that normal turnover of corneal epithelium is controlled by the autocrine production of growth factors, such as TGF-alpha. Growth factors present in tears may function primarily as exocrine factors to stimulate healing of epithelial injuries after the epithelial barrier has been damaged.
人角膜上皮细胞通常从顶端表面脱落，主要通过基底细胞的有丝分裂来替代。生长因子可能调节这一过程，但生长因子的来源尚未完全明确。泪液是生长因子的一个潜在来源，在泪腺和泪液中已检测到表皮生长因子（EGF）。然而，诸如EGF等生长因子的亲水性结构和大小可能会限制其穿透完整上皮的基底层。人角膜基底上皮细胞的更新可能受通过自分泌机制起作用的生长因子调控。为了确定人角膜上皮细胞是否合成潜在的自分泌生长因子，作者分析了人角膜上皮细胞中转化生长因子-α（TGF-α）信使核糖核酸和蛋白质，TGF-α是一种在结构上与EGF相关且能与EGF受体结合的生长因子。对人角膜上皮细胞培养物进行放射免疫测定，检测到大量免疫反应性TGF-α（3 ng/10⁶个细胞）。人角膜的免疫组织化学染色也显示角膜上皮中存在免疫反应性TGF-α。用32P标记的TGF-α互补DNA探针进行Northern杂交，在4.4千碱基处产生一条单一的强带，表明在培养的人角膜上皮细胞中存在TGF-α信使核糖核酸。这些结果支持这样的假说，即角膜上皮的正常更新受生长因子如TGF-α的自分泌产生所控制。泪液中存在的生长因子可能主要作为外分泌因子，在上皮屏障受损后刺激上皮损伤的愈合。
