Topical corticosteroids delay the proliferative response to sellotape stripping.

Tape stripping of normal human skin results in a hyperproliferative response brought about by a recruitment of resting (G0) cells. The effect of diprosone and hydrocortisone on this response was studied by flow cytometric techniques. Both corticosteroids were found to delay the appearance of the cohort of recruited cells in the S-phase, the more potent antipsoriatic (diprosone) giving the greatest delay. These data indicate that corticosteroids cause a temporary block in late G1 or an inhibition of the recruitment process itself. The model may serve for the evaluation of (future) antipsoriatic drugs.

Flow cytometric analysis of the recruitment of G0 cells in human epidermis in vivo following tape stripping.

Tape stripping of human skin elicits a proliferative response of a synchronously-dividing group of cells. The progress of this cohort of cells has been monitored using two windows in the cell cycle, one located in mid-S phase and the other centred around G2 + M. The cellular DNA is measured with flow cytometry, the windows are defined by two ranges in the DNA histogram. The cohort can be described as the recruitment of cells from a pre-existing G0 compartment which consists of 76% of all proliferative cells. The duration of the S phase is calculated to be 10.2 hr and G2 + M phase 5.1 hr. The cell cycle time of 39 hr for normal human keratinocytes derived from these figures is in line with recent values obtained by different techniques.

Monoclonal antibodies for epidermal population analysis.

Three keratin antibodies (RKSE 60, Clone 77, and a rabbit polyclonal) and 2 vimentin antibodies (Vim ab and a rabbit polyclonal) were investigated using frozen sections of normal and psoriatic skin. Of these, the monoclonals RKSE 60 and Vim ab were selected for quantitative population analysis of healthy epidermis, psoriatic uninvolved epidermis, and psoriatic lesions. Suspensions of isolated cells were prepared from biopsy specimens by trypsinization, and stained with RKSE 60 or Vim ab using an indirect immunofluorescence assay. Our results showed an increase in the germinative fraction from the normal value of 30% to almost 50% in the psoriatic lesion; in absolute terms this corresponds to a 6-fold increase in the size of the germinative compartment. More interesting, the germinative psoriatic uninvolved epidermis (38%) was also significantly higher than normal. The percentage of vimentin-positive cells (Langerhans cells and melanocytes) was nearly double that of normal in both the lesion and the uninvolved psoriatic epidermis. We conclude that, in contrast to statements frequently encountered in the literature, the "uninvolved" skin of the patient is morphologically and functionally different from that of the healthy individual.

Epidermal hyperproliferation following the induction of microabscesses by leukotriene B4.

The percentage of non-diploid epidermal cells was determined by flow cytometry following application of leukotriene B4 (LTB4) to human skin. Doses in the range 35-500 ng were shown to cause a marked increase in proliferation, the non-diploid cells reaching a maximum between 72 and 96 h after LTB4 application. No difference was observed between the response of healthy controls and the uninvolved skin of psoriatic patients. We suggest, therefore, that the hyperproliferation is a consequence of the physical disruption of the stratum corneum accompanying the rupture of microabscesses.

Methotrexate inhibits the leukotriene B4 induced intraepidermal accumulation of polymorphonuclear leukocytes.

The penetration of polymorphonuclear leukocytes (PMNs) into the epidermis following topical application of leukotriene B4 was assessed in the clinically uninvolved skin of psoriatic patients treated with methotrexate and of psoriatic patients without treatment, and in normal controls. Inhibition of PMN infiltration was observed in those patients treated with methotrexate while there was no significant difference between untreated psoriatic patients and normal controls.

Fucosyl glycopeptide profiles of keratinocytes from various epithelial tissues of the rabbit in relation to differentiation in vivo and in vitro.

Keratinocytes have been isolated from rabbit cornea, esophagus, and skin by trypsinization. The freshly isolated cells differed in their morphology, growth characteristics in culture, transglutaminase activity (a marker for differentiation), and the composition of glycoprotein-derived fucopeptides. A clear relationship has been shown between the proportion of low-molecular-weight fucopeptides and the pattern of keratinization, being minimal in cornea and maximal in skin. Comparison with earlier literature suggests that this relationship may be a general feature of epithelial tissue. After several passages in culture, all differences between the three cell types disappeared. The unusual elution pattern of the fucopeptides on gel filtration suggests the possibility of a block at an early stage of glycoprotein synthesis under culture conditions.

Response of the clinically uninvolved skin of psoriatic patients to standardized injury.

Test sites on healthy controls and on the clinically uninvolved skin of psoriatic patients were stripped with tape, and eight variables were quantified at intervals during the subsequent healing process. In the control groups, the stratum corneum regenerated at a constant rate and the underlying skin showed elevations of metabolic activity peaking around days 2-4. In the psoriatic groups, we observed that (I) the response of the keratinizing zone is identical to that of the controls, (2) the proliferative response is initially normal but remains elevated rather longer than usual, and (3) the dermal capillaries (indicated by alkaline phosphatase activity) show a gross hyper-reactivity which is already apparent after 1 day and which persists for more than a week. These findings support our previous conclusion that metabolic alteration of the dermal capillary precedes epidermal hyperplasia in the pathogenesis of the psoriatic lesion.

Flow cytometry as a tool for the study of cell kinetics in skin 2. Cell kinetic data in psoriasis.

Flow cytometry was used to measure the DNA content of epidermal keratinocytes from psoriatic patients. Gross deviations were found in the lesions and minor but significant changes in the uninvolved skin. Statistical analysis revealed that the rather large variation in the DNA distribution of the lesions was due to inter-individual differences rather than to intra-individual differences. The duration of the S-phase seemed to be prolonged in the lesion, but the length of the overall cell cycle might be of the same order as that of normal skin.

Flow cytometry as a tool for the study of cell kinetics in epidermis.

Flow cytometric measurements of the DNA content were performed on a large number of skin biopsies by an automated technique. Expressed as a percentage of all viable cells in the epidermis, the figures for cells in S-phase averaged 1.8% and for G2M 0.9%. No significant differences due to sex were found. Concomitantly with age the ratio S/G2M (representing the duration of S to the duration of G2M) increased. Also seasonal effects were clear, showing higher values for S and G2M in June compared to November and December. Lastly we found small differences dependent on body-site, the ratio S/G2M being greater in legs than in arms. The present status is discussed together with future lines of development.