Cell kinetic characterization of cultured human keratinocytes from normal and psoriatic individuals

Abstract

Psoriasis is a chronic skin disease characterized by epidermal hyperproliferation, disturbed differentiation, and inflammation. It is still a matter of debate whether the pathogenesis of psoriasis is based on immunological mechanisms, on defec tive growth control mechanisms, or possibly on a combination of both. Several in vivo cell biological differences between psoriatic lesional epidermis and normal epidermis have been reported. However, it is not clear whether these changes are causal or consequential. In case that keratinocytes from psoriatic patients have genetically determined deficiencies or polymorphisms with respect to autocrine growth regulation and the response to inflammatory cytokines, we hypothesize that these differences should be maintained in culture. Here we have started a systematic comparison of first passage keratinocytes cultured from normal skin and uninvolved psoriatic skin to address the question whether there are intrinsic differences in basic cell cycle parameters. In an established, defined culture system using keratinocyte growth medium (KGM) we have determined: (i) cell cycle parameters of exponentially growing keratinocytes, (ii) induction of quies cence by transforming growth factor (Jj (TGF-p,), and (iii) restimulation from the Go-phase of the cell cycle. Bivariate analysis of lodo-deoxyuridine incorporation and relative DNA content was performed by flow cytometry. Within the limita tions of this model no gross differences were found between normal and psoriatic keratinocytes with respect to S-phase duration (Ts), total cell cycle duration (Tc), responsiveness to TGF-fi, and the kinetics for recruitment from G 0. In psoriatic keratinocytes we found a lower amount of cells in S-phase and a shorter duration of G w compared to normal keratinocytes. The methodology developed here provides us with a model for further studies on differences between normal and psoriatic keratinocytes in their response to immunological and inflammatory me diators,

In Vivo and In Vitro Models of Psoriasis

“…For example, monolayer cell cultures have helped to realize that TGF-regulates VEGF expression in psoriasis through an autocrine mechanism, leading to vascular hyperpermeability and angiogenesis (Detmar et al, 1994). In other experiments, van Ruissen et al found that psoriatic keratinocytes display a lower number of cells in S-phase and a shorter duration of G1 compared to normal keratinocytes (van Ruissen et al, 1996). Monolayer cultures are widely used and have led to many critical observations (Table 3).…”

“…? (van Ruissen, et al, 1996) De-epidermized dermis Organ culture --? - (Mils, et al, 1994) Keratinocytes + + ?…”

“…As previously shown, a number of teams have carried out in vitro monolayer and stratified keratinocyte culture studies to better understand the behaviour of cell types both in an individual way, but also to study the interactions between cells with co-culture and conditioned media techniques (Mils, et al, 1994;Saiag, et al, 1985;van Ruissen, et al, 1996). Some of these studies have shown the importance of the interaction between fibroblasts and keratinocytes in psoriatic models.…”

Modulation of TGF‐β1 production from human keratinocytes by UVB

“…Furthermore, TGF-(3 mRNA levels in mice epidermal cells have been shown to be induced in response to the tumour promoter 12tetradecanoyl-phorbol-13-acetate (TPA) (21). UVB and TGF-P 1 are both known to cause Gl growth arrest in keratinocytes (22,23). However, the time course for these two phenomena are different: UVB-mediated growth arrest is known to occur within 3 h after UVB irradiation (22), while treatment with TGF-P 1 results in growth arrest in approximately 52 h (23).…”

“…UVB and TGF-P 1 are both known to cause Gl growth arrest in keratinocytes (22,23). However, the time course for these two phenomena are different: UVB-mediated growth arrest is known to occur within 3 h after UVB irradiation (22), while treatment with TGF-P 1 results in growth arrest in approximately 52 h (23). This fact seems to eliminate the possibility that TGF-P 1 mediates UVB-induced growth arrest of keratinocytes.…”