Interleukin 6 Receptors on Human Outer Root Sheath Cells and Interfollicular Epidermal Keratinocytes in vitro: Density-Induced down Regulation (DIDR) of Receptors

• Published in: In vitro cellular & developmental biology. Animal 1996-05, Vol.32 (5), p.255-258
• Main Authors: Waelti, Ernst R., Inaebnit, Sven P., Wiesmann, Ulrich, Limat, Alain, Hunziker, Thomas
• Format: Article
• Language: English
• Subjects: Antigens, CD - metabolism; Cell Count; Cell lines; Cells, Cultured; Cultured cells; Down-Regulation; Epidermal cells; Epithelial cells; Feeder cells; Fibroblast growth factors; Hair Follicle - metabolism; Humans; Interleukin-6 - metabolism; Interleukins; Keratinocytes; Keratinocytes - metabolism; Receptors; Receptors, Interleukin - metabolism; Receptors, Interleukin-6; Scientific Reports; T lymphocytes
• ISSN: 1071-2690; 1543-706X
• DOI: 10.1007/BF02723055

Interleukin 6 (IL-6) is a cytokine that mediates a wide range of inflammatory and immune responses. In the injured skin as well as in inflammatory and hyperproliferative skin diseases such as psoriasis, IL-6 expression is elevated. However, its precise role in cutaneous physiology as well as in the pathology of skin diseases is still ill-defined. In transgenic mice that overexpress IL-6 in basal epidermal cells, a thicker stratum corneum was noted with an otherwise normal program of differentiation and no enhanced epidermal proliferation. In vitro, IL-6 has been repeatedly reported to stimulate proliferation of human epidermal keratinocytes (HEK), although other studies did not disclose such an effect. IL-6 might exert its growth-promoting activity by binding to IL-6 receptors (IL-6R) expressed on those keratinocytes that are in a stage of active growth. This assumption is corroborated by the observation that IL-6R-positive cells were detected by immunohistochemical staining in the deeper layers of stratified HEK cultures, but not in the differentiated keratinocytes of the upper layers. Furthermore, high-affinity IL-6R were reported by Krueger et al. in monolayers of HEK. Recent studies have demonstrated that the expression of several growth factor receptors on the surface of cultured cells is regulated by the cell density, a phenomenon referred to as density-induced downregulation (DIDR). This in mind, we wanted to determine whether in HEK IL-6R expression, too, is modulated by cell density or by raising the Ca super(2+)-concentration in the medium to levels that promote differentiation of HEK. Expression of IL-6R was also analyzed in outer root sheath (ORS) cells of human hair follicles because these cells can substitute for interfollicular epidermal keratinocytes as, for example, in healing of superficial wounds.