Maas-Szabowski N, Stark H J, Fusenig N E
Division of Differentiation and Carcinogenesis, German Cancer Research Center, Heidelberg, Germany.
J Invest Dermatol. 2000 Jun;114(6):1075-84. doi: 10.1046/j.1523-1747.2000.00987.x.
Balanced keratinocyte proliferation and differentiation resulting in regular tissue organization strictly depend on dermal support. Organotypic cultures represent biologically relevant in vitro models to study the molecular mechanism of the underlying dermal-epidermal interactions. To mimic the state of resting fibroblasts in the dermis, postmitotic (irradiated) fibroblasts were incorporated in the collagen matrix, where they typically support epidermal proliferation and tissue organization. In coculture with keratinocytes, fibroblasts exhibit an enhanced expression of keratinocyte growth factor and the interleukin-1 receptor (type I), which further increase with culture time. In cocultured keratinocytes, keratinocyte growth factor receptor as well as RNA expression and protein release of interleukin-1alpha and interleukin-1beta are upregulated. We hypothesized that the modulated cytokine expression represents a basic mechanism for keratinocyte growth regulation. The functional significance of this double paracrine pathway, i.e., induction of keratinocyte growth factor expression in fibroblasts by keratinocytes via release of interleukin-1, was confirmed by interfering with both signaling elements: (i) interleukin-1-neutralizing antibodies and interleukin-1 receptor antagonist significantly inhibited keratinocyte growth factor release, keratinocyte proliferation, and tissue formation comparable to the effect produced by keratinocyte-growth-factor-blocking antibodies; (ii) addition of keratinocyte growth factor to cocultures with inactivated interleukin-1 pathway completely reverted growth inhibition; (iii) in organotypic cocultures with subthreshold fibroblast numbers both interleukin-1 and keratinocyte growth factor restored the impaired epidermal morphogenesis. Thus, epidermal tissue regeneration in organotypic cocultures is mainly regulated by keratinocyte-derived interleukin-1 signaling, which induces keratinocyte growth factor expression in cocultured fibroblasts. This demonstrates a novel role for interleukin-1 in skin homeostasis substantiating data from wound healing studies in vivo.
角质形成细胞的增殖和分化达到平衡从而形成规则的组织结构，这严格依赖于真皮的支持。器官型培养代表了具有生物学相关性的体外模型，用于研究潜在的真皮 - 表皮相互作用的分子机制。为了模拟真皮中静止成纤维细胞的状态，将有丝分裂后（经辐射）的成纤维细胞整合到胶原基质中，在那里它们通常支持表皮增殖和组织形成。在与角质形成细胞共培养时，成纤维细胞表现出角质形成细胞生长因子和白细胞介素 -1 受体（I 型）表达增强，且随着培养时间进一步增加。在共培养的角质形成细胞中，角质形成细胞生长因子受体以及白细胞介素 -1α 和白细胞介素 -1β 的 RNA 表达和蛋白质释放均上调。我们推测，细胞因子表达的调节是角质形成细胞生长调节的一种基本机制。通过干扰两个信号元件，证实了这种双旁分泌途径的功能意义，即角质形成细胞通过释放白细胞介素 -1 诱导成纤维细胞中角质形成细胞生长因子的表达：（i）白细胞介素 -1 中和抗体和白细胞介素 -1 受体拮抗剂显著抑制角质形成细胞生长因子的释放、角质形成细胞增殖和组织形成，其效果与角质形成细胞生长因子阻断抗体产生的效果相当；（ii）将角质形成细胞生长因子添加到白细胞介素 -1 途径失活的共培养物中完全逆转了生长抑制；（iii）在成纤维细胞数量低于阈值的器官型共培养物中，白细胞介素 -1 和角质形成细胞生长因子均恢复了受损的表皮形态发生。因此，器官型共培养物中的表皮组织再生主要受角质形成细胞衍生的白细胞介素 -1 信号调节，该信号在共培养的成纤维细胞中诱导角质形成细胞生长因子的表达。这证明了白细胞介素 -1 在皮肤稳态中的新作用，证实了体内伤口愈合研究的数据。
