Eming S A, Snow R G, Yarmush M L, Morgan J R
Surgical Services, Massachusetts General Hospital and Shriners Burns Institute, Boston, USA.
J Invest Dermatol. 1996 Jul;107(1):113-20. doi: 10.1111/1523-1747.ep12298351.
Somatomedin C/insulin-like growth factor-I (IGF-I) is required for the proliferation of keratinocytes in vitro. In skin, the cells known to synthesize IGF-I are melanocytes and fibroblasts of the dermis. To investigate the role of IGF-I as a mediator of keratinocyte proliferation, we have used retroviral-mediated gene transfer to introduce the gene encoding human IGF-I into diploid human keratinocytes, thus causing these cells to produce a growth factor they normally do not express. Modified cells synthesized and secreted significant levels of IGF-I (560 ng/10(7) cells/24 h) in vitro. Cells expressing IGF-I were no longer dependent on exogenously added IGF-I or insulin for their sustained growth in vitro under serum-free conditions. The growth of these cells did require added epidermal growth factor (EGF) and bovine pituitary extract. The addition of an antibody that neutralizes IGF-I inhibited cell growth, suggesting that IGF-I must be secreted by the cells to promote cell proliferation. To investigate the role of IGF-I in vivo, we grafted modified keratinocytes expressing IGF-I onto athymic mice. Grafts of epithelial sheets of modified cells formed a stratified epithelium comparable to control grafts of unmodified cells. When analyzed for keratin 16 expression and by quantitative staining for the nuclear proliferation antigen Ki-67, however, modified epithelia showed an increase in these markers of proliferation when compared with grafts of unmodified cells. This study demonstrates that genetic modification can be used to modify the autocrine control of keratinocyte proliferation. The de novo synthesis of IGF-I by keratinocytes could sustain keratinocytes growth in vitro and stimulate proliferation in vivo without significantly altering epidermal differentiation. These data further support the role of IGF-I as a paracrine mediator of epidermal proliferation and as a potential signal of mesenchymal-epithelial interactions.
生长调节素C/胰岛素样生长因子-I（IGF-I）是体外培养的角质形成细胞增殖所必需的。在皮肤中，已知能合成IGF-I的细胞是真皮中的黑素细胞和成纤维细胞。为了研究IGF-I作为角质形成细胞增殖介质的作用，我们利用逆转录病毒介导的基因转移技术，将编码人IGF-I的基因导入二倍体人角质形成细胞，从而使这些细胞产生一种它们通常不表达的生长因子。修饰后的细胞在体外合成并分泌了大量的IGF-I（560 ng/10⁷细胞/24小时）。在无血清条件下，表达IGF-I的细胞在体外持续生长不再依赖于外源性添加的IGF-I或胰岛素。这些细胞的生长确实需要添加表皮生长因子（EGF）和牛垂体提取物。添加中和IGF-I的抗体可抑制细胞生长，这表明IGF-I必须由细胞分泌才能促进细胞增殖。为了研究IGF-I在体内的作用，我们将表达IGF-I的修饰角质形成细胞移植到无胸腺小鼠身上。修饰细胞的上皮片移植形成了与未修饰细胞的对照移植相似的分层上皮。然而，当分析角蛋白16的表达以及通过对核增殖抗原Ki-67进行定量染色时，与未修饰细胞的移植相比，修饰上皮显示出这些增殖标志物的增加。这项研究表明，基因修饰可用于改变角质形成细胞增殖的自分泌控制。角质形成细胞从头合成IGF-I可在体外维持角质形成细胞的生长，并在体内刺激增殖，而不会显著改变表皮分化。这些数据进一步支持了IGF-I作为表皮增殖旁分泌介质以及作为间充质-上皮相互作用潜在信号的作用。
