Growth related secretion and production of GM-CSF by epithelial cell line

Diversified Stimuli-Induced Inflammatory Pathways Cause Skin Pigmentation

The production of melanin pigments by melanocytes and their quantity, quality, and distribution play a decisive role in determining human skin, eye, and hair color, and protect the skin from adverse effects of ultraviolet radiation (UVR) and oxidative stress from various environmental pollutants. Melanocytes reside in the basal layer of the interfollicular epidermis and are compensated by melanocyte stem cells in the follicular bulge area. Various stimuli such as eczema, microbial infection, ultraviolet light exposure, mechanical injury, and aging provoke skin inflammation. These acute or chronic inflammatory responses cause inflammatory cytokine production from epidermal keratinocytes as well as dermal fibroblasts and other cells, which in turn stimulate melanocytes, often resulting in skin pigmentation. It is confirmed by some recent studies that several interleukins (ILs) and other inflammatory mediators modulate the proliferation and differentiation of human epidermal melanocytes and also promote or inhibit expression of melanogenesis-related gene expression directly or indirectly, thereby participating in regulation of skin pigmentation. Understanding of mechanisms of skin pigmentation due to inflammation helps to elucidate the relationship between inflammation and skin pigmentation regulation and can guide development of new therapeutic pathways for treating pigmented dermatosis. This review covers the mechanistic aspects of skin pigmentation caused by inflammation.

Insulin-like growth factor-binding protein contributes to the proliferation of less proliferative cells in forming skin equivalents

In this study, the effects and the mediating factors of dermal cells on the epidermal regenerative ability were investigated. Human epidermal cells were separated into rapidly adhering (RA) cells and slowly adhering (SA) cells and used for culturing skin equivalents (SEs). For dermal part, normal human fibroblasts, dermal sheath cells (DSCs), and dermal papilla cells were used. SEs produced using SA cells and DSCs showed a thicker epidermis and higher expressions of alpha(6)- and beta1-integrin than SEs using SA cells and normal fibroblasts showed. We hypothesized that DSCs may secrete specific cytokines that can influence the regenerative potential of epidermal cells, and compared cytokine secretion by DSCs and normal human fibroblasts. Using RayBio human cytokine antibody array C (series 1000), 120 cytokines were tested. Results showed that DSCs produced a much greater amount of insulin-like growth factor-binding protein (IGFBP-2), angiogenin, and BMP-6 than normal human fibroblasts produced. On the basis of the cytokine antibody array, we next investigated whether IGFBP-2, angiogenin, or BMP-6 has effects on SEs reconstruction. The addition of IGFBP-2 induced a thicker and more mature epidermis and higher expressions of alpha(6)- and beta1-integrin, whereas BMP-6 exhibited little effect. Thus, the SEs with IGFBP-2 showed almost the same morphology of the SEs using DSCs. Further, p63, a putative keratinocyte stem cell marker, was more frequently observed in the basal layer of SE with IGFBP-2. In conclusion, IGFBP-2 is a major factor from DSCs that affects epidermal regenerative capacity of skin and may play an important role for stemness maintenance in human epidermal keratinocytes.

Adrenomedullin signals through NF-kappaB in epithelial cells

Adrenomedullin is a peptide found in a variety of cells and tissues and involved in a multitude of biological processes. Recently, adrenomedullin has been identified as a host defense peptide and as such it plays a role in the inflammatory response. The transcription factor NF-kappaB is a major regulator of genes involved in the inflammatory response and the aim of this study was to determine whether NF-kappaB played a role in the inflammatory process triggered by adrenomedullin. Skin epithelial cells (HaCaTs) were used as our model in vitro. Western blot analysis from adrenomedullin-stimulated HaCaT cells revealed a rapid degradation of NF-kappaB inhibitor alpha and beta followed by the translocation of free NF-kappaB to the nucleus, where it was detected by Texas Red immunostaining after incubation with adrenomedullin for 15 min. Electromobility shift assay showed that NF-kappaB present in the nucleus was active, since it bound to a probe containing an NF-kappaB binding site. Supershift assays indicated that p50 and p65, members of the NF-kappaB family, were both part of the NF-kappaB dimmers involved in adrenomedullin cell signaling. HaCaTs secreted interleukin-6 in response to AM, which was significantly attenuated by the NF-kappaB inhibitor SN-50. Taken together, the data lend support for an immunoregulatory role for AM.

Multilineage differentiation of rhesus monkey embryonic stem cells in three-dimensional culture systems

In the course of normal embryogenesis, embryonic stem (ES) cells differentiate along different lineages in the context of complex three-dimensional (3D) tissue structures. In order to study this phenomenon in vitro under controlled conditions, 3D culture systems are necessary. Here, we studied in vitro differentiation of rhesus monkey ES cells in 3D collagen matrixes (collagen gels and porous collagen sponges). Differentiation of ES cells in these 3D systems was different from that in monolayers. ES cells differentiated in collagen matrixes into neural, epithelial, and endothelial lineages. The abilities of ES cells to form various structures in two chemically similar but topologically different matrixes were different. In particular, in collagen gels ES cells formed gland-like circular structures, whereas in collagen sponges ES cells were scattered through the matrix or formed aggregates. Soluble factors produced by feeder cells or added to the culture medium facilitated ES cell differentiation into particular lineages. Coculture with fibroblasts in collagen gel facilitated ES cell differentiation into cells of a neural lineage expressing nestin, neural cell adhesion molecule, and class III beta-tubulin. In collagen sponges, keratinocytes facilitated ES cell differentiation into cells of an endothelial lineage expressing factor VIII. Exogenous granulocyte-macrophage colony-stimulating factor further enhanced endothelial differentiation. Thus, both soluble factors and the type of extracellular matrix seem to be critical in directing differentiation of ES cells and the formation of tissue-like structures. Three-dimensional culture systems are a valuable tool for studying the mechanisms of these phenomena.

Dynamic characterization of the molecular events during in vitro epidermal wound healing

The aim of this study was to characterize some of the molecular events stimulated in vitro in response to injury within a confluent culture of normal epidermal keratinocytes as a model to understand the mechanisms of wound healing. To this end, an original device was developed specifically designed to perform calibrated injuries of great lengths within mono-stratified or pluri-stratified keratinocyte cultures. The experiments performed in this study validate this device as an appropriate tool for studying epidermal wound healing; this is because it performs mechanical injuries that stimulate the expression of multiple healing markers also known to be upregulated during wound healing in vivo (growth factors, cytokines, proteinases, extracellular matrix proteins). Using this device, it was demonstrated in human keratinocytes: mechanical injuries (i) immediately stimulate the tyrosine phosphorylation of numerous cellular proteins; (ii) induce molecular cascades leading to the activation of p21ras, mitogen-activated protein kinases, extracellular signal-regulated kinases 1/2, c-Jun NH2 terminal kinase, and p38 mitogen-activated protein kinase; and (iii) increase the phosphorylation of their respective substrates, c-jun and activator transcription factor 1. Wounding of these cells also results in increases in the DNA binding activities of several jun/fos activator protein-1 transcription factor complexes. It is important to note that the development of an appropriate wounding system was essential for performing this study, as use of a classical wounding procedure did not enable the detection of the biologic parameters reported above. In conclusion, these data indicate that using the appropriate system, it is possible to identify the signaling pathways activated in normal human keratinocyte cells after injury. In this study, it was shown that the mitogen-activated protein kinase pathways and activator protein-1 are stimulated in response to physical injury, and may be involved in regulating the expression of healing markers.

Keratinocyte-derived granulocyte-macrophage colony stimulating factor accelerates wound healing: Stimulation of keratinocyte proliferation, granulation tissue formation, and vascularization

Chronic, nonhealing wounds represent a major clinical challenge to practically all disciplines in modern medicine including dermatology, oncology, surgery, and hematology. In skin wounds, granulocyte-macrophage colony stimulating factor (GM-CSF) is secreted by keratinocytes shortly after injury and mediates epidermal cell proliferation in an autocrine manner. Many other cells involved in wound healing including macrophages, lymphocytes, fibroblasts, endothelial cells, and dendritic cells synthesize GM-CSF and/or are targets of this cytokine. Therefore, GM-CSF is a pleiotropic cytokine evoking complex processes during wound repair. Despite this complexity and the scarcity of mechanistic understanding GM-CSF has been employed in trials of clinical treatment of skin wounds with some success. In this study, we evaluated a transgenic mouse model in order to analyze the effects of an excess of keratinocyte-derived GM-CSF on excisional wound healing in the skin. Transgenic mice constitutively overexpressing GM-CSF in the basal layer of the epidermis displayed accelerated reepithelialization of full-thickness skin wounds. In the early stages of wound repair, transgenic mice exhibited significantly higher numbers of proliferating keratinocytes at the wound edges and increased formation of granulation tissue with enhanced neovascularization. As a potential mechanism of these beneficial changes, we identified the differential temporal regulation of cytokines such as transforming growth factor-beta, a known angiogenetic factor, interferon-gamma, a proinflammatory cytokine, and interleukin 6, an essential factor for reepithelialization, in transgenic mice versus controls. We propose that the beneficial effects observed in GM-CSF transgenics are due not only to direct GM-CSF action but in addition to indirect processes via the induction of secondary cytokines.