Mutual induction of growth factor gene expression by epidermal-dermal cell interaction

Abstract

Abstract. Epithelial-mesenchymal interactions control epidermal growth and differentiation, but little is known about the mechanisms of this interaction. We have examined the effects of human dermal microvascular endothelial cells (DMEC) and fibroblasts on keratinocytes in conventional (feeder layer) and organotypic cocultures (lifted collagen gels) and demonstrated the induction of paracrine growth factor gene expression. Clonal keratinocyte growth was similarly stimulated in cocultures with irradiated DMEC and fibroblasts as feeder cells. This effect is most probably caused by induction of growth factor expression in cocultured dermal cells. Keratinocytes stimulated mRNA levels for KGF and IL-6 in both mesenchymal cell types and GM-CSF in fibroblasts. The feeder effect could not be replaced by conditioned media or addition of isolated growth factors.In organotypic cocultures with keratinocytes growing on collagen gels (repopulated with dermal cells), a virtually normal epidermis was formed within 7 to 10 d. Keratinocyte proliferation was drastically stimulated by dermal cells (histone 3 mRNA expression and BrdU labeling) which continued to proliferate as well in the gel. Expression of all typical differentiation markers was provoked in the reconstituted epithelium, though with different localization as compared to normal epidermis. Keratins K1 and K10 appeared coexpressed but delayed, reflecting conditions in epidermal hyperplasia. Keratin localization and proliferation were normalized under in vivo conditions, i.e., in surface transplants on nude mice. From these data it is concluded that epidermal homeostasis is in part controlled by complex reciprocally induced paracrine acting factors in concert with cell-cell interactions and extracellular matrix influences.T HERE is accumulating evidence that epithelial-mesenchymal interactions regulate tissue homeostasis in surface epithelia such as epidermis (6,7,9,13,19,20,(30)(31)(32)47). In vivo, these processes are difficult to study due to many variables involved such as the different dermal cell types and superimposed influences of systemic factors of the blood circulation. Thus, in vitro model systems have been developed to mimic epidermal-dermal interactions and to study regulation of epidermal cell proliferation and differentiation (for review see reference 19). It had been shown that coculture on postmitotic fibroblastic mouse 3T3 cells (42, 54) as well as human dermal fibroblasts (30) are required to support human keratinocyte growth at clonal densities in serum containing medium. Under conventional (submerged) culture conditions keratinocyte proliferation is the predominant phenomenon whereas terminal differentiation and tissue organization are reduced or aberrant cornDr. Smola's present address is Department of Dermatology, University of Cologne, Joseph-Stelzmann-Strasse 9, 5000 Cologne, Germany.Address correspondence to Dr. N. E. Fusenig, Division of Differentiation and Carcinogenesis, DKFZ, Im Neuenheimer Feld 280, 6900 Heidelberg, Germany. pared to the ...

Liposomal gene transfer of multiple genes is more effective than gene transfer of a single gene

“…11 KGF is synthesized by several mesenchymal cells, such as fibroblasts, 12,15 For KGF to exert its effects, which is mainly in a paracrine manner, KGF needs to bind to its receptor FGFR2-IIIb, which is expressed in keratinocytes and hair follicles. 13,[22][23][24] Activating the KGF receptor leads, through phosphorylation, to proliferation of epithelial cells and is responsible for the morphogenesis of the skin and thus plays an important role during wound healing. 12 After wounding, KGF protein and mRNA concentration increases and they are mainly present in the dermal fibroblasts below the wound and at the wound edges, whereas KGF receptor transcripts and also the corresponding protein were exclusively detected in keratinocytes of the epidermis and the hair follicles.…”

Role of fibroblasts in the regulation of proinflammatory interleukin IL-1, IL-6 and IL-8 levels induced by keratinocyte-derived IL-1

“…There is increasing evidence for the existence of a com plex network of interacting cytokines mediating immune and inflammatory reactions in the skin [30,31], Fibro blasts of the mesenchymal compartment and keratino cytes of the epithelial compartment participate actively and mutually in this network [32,33]. IL-1 released from keratinocytes seems to play an important role in the initi ation of a cytokine cascade, because I L -la derived from the keratinocytes is responsible for markedly enhanced IL-6 [11] and IL-8 (this study) production in fibroblasts.…”

Tumor Progression of Skin Carcinoma Cells in Vivo Promoted by Clonal Selection, Mutagenesis, and Autocrine Growth Regulation by Granulocyte Colony-Stimulating Factor and Granulocyte-Macrophage Colony-Stimulating Factor

“…54 This difference in selective pressure for tumor progression between the in vitro and the in vivo environment is also reflected in the phenotype of in vivo progressed populations, which exhibit a decreased in vitro growth capacity, as was seen when A-5RT cells were compared to the parental A-5 cells. Although A-5RT cells, to survive in vitro, originally required growth support by feeder fibroblasts that mimic a mesenchymal compartment 55 they became independent of these feeder cells during prolonged passages in tissue culture. However, they retained a reduced in vitro growth potential compared to A-5 cells, as is evident from population doubling times and cloning experiments.…”