Mitogenic effects of sera from normal and psoriatic subjects on human skin fibroblasts

Use of Cytokine Mix-, Imiquimod-, and Serum-Induced Monoculture and Lipopolysaccharide- and Interferon Gamma-Treated Co-Culture to Establish In Vitro Psoriasis-like Inflammation Models

Psoriasis (Ps), commonly perceived as a skin and joint disorder, has a complex basis and results from disturbances in the sophisticated network between skin and the immune system. This makes it difficult to properly depict the complete pathomechanism on an in vitro scale. Deciphering the complicated or even subtle modulation of intra- and intercellular factors, assisted by the implementation of in vitro human skin models, may provide the opportunity to dissect the disease background step by step. In addition to reconstructed artificial skin substitutes, which mimic the native physiological context, in vitro models are conducive to the broad "3 Rs" philosophy (reduce, refine, and replace) and represent important tools for basic and applied skin research. To meet the need for a more comprehensive in vitro Ps model, a set of various experimental conditions was applied in this study. The selection of in vitro treatment that mimicked the Ps phenotype was illustrated by analyses of discriminating biomarker genes involved in the pathogenesis of the disease, i.e., keratinocyte differentiation markers, antimicrobial peptides, chemokines, and proliferation markers. This resulted in a reproducible protocol for the use of the primary skin keratinocyte (pKC) monoculture treated with a cytokine cocktail (5MIX, i.e., interleukin (IL) 1 alpha (IL-1α), IL-17A, IL-22, oncostatin M (OSM), and tumour necrosis factor alpha (TNF-α)) at a calcium (Ca2+) concentration (i.e., 2 mM) in an applied medium, which best mirrored the in vitro Ps-like inflammatory model. In addition, based on waste skin material, the method has the potential for extensive experimentation, both in detailed molecular studies and preclinical tests.

Etretinate administration reduces serum propeptide of type I procollagen level in patients with psoriasis

The serum carboxyterminal propeptide of type I procollagen (PICP) level in 26 patients with psoriasis was significantly lower than in control subjects (124 +/- 47 and 224 +/- 78 ng/ml, respectively; P < 0.001). The patients were divided into two groups, those treated with etretinate and untreated patients. PICP levels in the treated group were significantly lower than those in the untreated group (P < 0.001), but there was no difference between the control and untreated groups. In addition, there was a negative correlation between PICP levels and the serum etretinate concentration in treated patients (r = -0.622, P < 0.05). There was no difference between procollagen type III aminoterminal propeptide (PIIIP) levels in patients and controls, nor was there any significant difference between etretinate-treated and untreated patients. In cell culture studies, etretinate dose-dependently (from 10(-9) to 10(-5) M) decreased the PICP concentration in the medium of fibroblasts from both healthy subjects and patients. In osteoblast cell culture, PICP levels were reduced only in a high concentration of etretinate (10(-5) M). However, no change was observed in preadipose cells. Our in vivo and in vitro observations indicated that psoriasis per se did not affect either serum PICP or PIIIP levels, but that etretinate had an inhibitory effect on collagen synthesis by fibroblasts. Hence, the administration of etretinate to psoriatic patients is, at least in part, responsible for the reduction of serum PICP levels in these patients.

Studies and perspectives of signal transduction in the skin

Tumor-promoting phorbol ester and epidermal growth factor (EGF) exert marked influences on the proliferation and differentiation of keratinocytes. These two agents bring their physiological functions into play via protein kinase C (PKC) activation (and/or down regulation) and protein tyrosine kinase, respectively. In this paper, the present situation in the studies on the signal transduction of keratinocytes centering around these two kinases is discussed. An outline of studies on signal transduction of cells other than keratinocytes in the skin is also given.

The mitogenic effects of sera from psoriatic subjects on normal dermal fibroblasts: an absence of correlation with the clinical activity of psoriasis

Serum was obtained from 21 normal and 22 psoriatic subjects, and the severity of skin disease in the psoriatic patients was recorded using the PASI score. The scores ranged from 1.8 to 51.0. The growth stimulatory effect of the sera on normal dermal fibroblasts in cell culture was assessed by measuring [3H]-thymidine uptake. Each serum was assessed at four concentrations (2,5, 10,20%). The psoriatic sera were more growth stimulatory than normal sera, but this difference was statistically significant (P less than 0.02) only at 20% serum concentration. Eleven of the 22 psoriatic serum samples had a mitogenic effect greater than the mean +/- SEM of all the normal sera; these sera were then from patients with PASI scores of 4.5-51.0. Six of these psoriatic subjects were recalled after 5 months; their PASI scores were reassessed, and the mitogenic effect of new serum samples was compared with that of the initial samples. All of these patients displayed a change in serum mitogenic effect, but this was not consistent with the change in severity of skin disease over the corresponding time period. In one subject, the severity of the psoriasis had increased marginally over the 5 months, while the mitogenic effect of her serum decreased significantly (mean counts of 43808 vs. 32660; P = 0.0029).

Increased protein kinase C activity in fibroblast membranes from psoriatic patients

The activity of phospholipid/Ca2+-dependent protein kinase (PKc) was measured in the membrane and cytosolic fractions of normal and psoriatic human fibroblasts. The psoriatic fibroblasts displayed higher membrane-associated PKc activity than normal cells. In contrast, no significant difference in PKc activities was observed in cytosolic fractions from normal and psoriatic fibroblasts. These data suggest that PKc is preferentially associated with the membrane in psoriatic fibroblasts and that such elevated PKc activity in membranes may play a role in the pathogenesis of this disease.