Human Psoriatic Skin in Organ Culture: Comparison with Normal Skin Exposed to Exogenous Growth Factors and Effects of an Antibody to the EGF Receptor

Abstract

Organ cultures were established from psoriatic lesional skin of 24 different individuals and maintained for 8 days under serum-free, growth-factor-free conditions. Nonlesional skin from 14 of the same individuals and normal skin from another 12 individuals were also maintained in organ culture. At the end of the incubation period, the tissues were fixed in formalin and examined histologically. Lesional skin continued to express features of psoriatic plaque, which included irregularly shaped epithelial cells arranged in a disorganized fashion, and elongation of the rete ridges with a thickening in their lower portion. Abnormal epidermal differentiation and separation of the upper epidermal layers from the lower layers was also a consistent feature. In contrast, nonlesional skin from psoriatic patients exhibited a histological appearance which resembled that of site-matched normal skin. When normal skin was exposed to a growth-factor-enriched culture medium during the 8-day incubation period, it exhibited a histological appearance similar to that of psoriatic skin. In addition to abnormal histological features, the psoriatic skin in organ culture released higher amounts of matrix metalloproteinase-9 (MMP-9; 92-kD gelatinase B/type IV collagenase) into the culture fluid than either nonlesional skin or normal skin. Organ cultures of psoriatic lesional skin from 6 individuals were maintained for 8 days in the presence of an antibody to the human epidermal growth-factor (EGF) receptor. The abnormal histological features of the psoriatic tissue were partially ameliorated in the presence of the antibody. These data suggest that growth factors which act through the EGF receptor help to maintain the psoriatic phenotype in organ culture. They also suggest that organ culture may provide a useful tool with which to elucidate the pathophysiological mechanisms of altered keratinocyte proliferation and differentiation in psoriasis.

A Novel Benzodiazepine Selectively Inhibits Keratinocyte Proliferation and Reduces Retinoid-Induced Epidermal Hyperplasia in Organ-Cultured Human Skin

“…A number of approaches have led to the conclusion that the triggering event in psoriasis is an immune system defect (Valdimarsson et al, 1995;Austin et al, 1999). Nevertheless, the downstream events that precipitate psoriatic hyperplasia (like those in retinoid hyperplasia), involve keratinocyte growth regulation (Gottlieb et al, 1988;Elder et al, 1989;Cook et al, 1992;Piepkorn et al, 1998Piepkorn et al, , 2003Varani et al, 1998). Utility of agents that target abnormal keratinocyte proliferation for treatment of hyperplastic skin diseases will, ultimately, require formulation for topical delivery.…”

“…As a first step, we used a model of retinoidinduced epidermal hyperplasia in human skin organ culture as the test system. Past studies have demonstrated that although the etiologies are different, retinoid hyperplasia (Varani et al, 2001), like the hyperplasia in psoriasis (Gottlieb et al, 1988;Elder et al, 1989;Cook et al, 1992;Piepkorn et al, 1998Piepkorn et al, , 2003Varani et al, 1998), involves intraepidermal production of ligands for the epidermal growth factor (EGF) receptor, and autocrine or paracrine EGF receptor activation. The results presented here demonstrate significant reduction in retinoid-stimulated hyperplasia without detrimental effects on normal keratinocyte proliferation or fibroblast function.…”

Anti-CD11a Ameliorates Disease in the Human Psoriatic Skin–SCID Mouse Transplant Model: Comparison of Antibody to CD11a with Cyclosporin A and Clobetasol Propionate

“…Consistent with this theory, we previously demonstrated that the same skin that becomes hyperplastic after transplantation onto SCID mice remains histologically normal when placed in organ culture in the absence of exogenous growth factors. Hyperplasia can be induced in organ-cultured skin by treatment with exogenous growth factors (Varani et al 1994(Varani et al , 1998.…”

“…No animal disease completely mimics psoriasis (Carroll et al, 1995;Sundberg et al, 1990). Keratinocytes and fibroblasts from psoriatic skin were isolated and studied in monolayer culture (Nickoloff et al 1989;Pellegrini et al, 1992;Priestley, 1987), and psoriatic lesional skin was studied in organ culture (Caron, 1968;Kondo, 1986;Kondo et al, 1992;Mils et al, 1994;Varani et al, 1998). Although some of the phenotypic characteristics of psoriatic lesional skin are maintained under in vitro culture conditions, other characteristics are lost over time (Kondo, 1986;Mils et al, 1994;Varani et al, 1998).…”

7-Chloro-5-(4-hydroxyphenyl)-1-methyl-3-(naphthalen-2-ylmethyl)-4,5-dihydro-1H-benzo[b][1,4]diazepin-2(3H)-one (Bz-423), a Benzodiazepine, Suppresses Keratinocyte Proliferation and Has Antipsoriatic Activity in the Human Skin-Severe, Combined Immunodeficient Mouse Transplant Model

“…Given that epidermal hyperplasia in retinoid-treated skin and psoriatic epidermal hyperplasia both involve increased keratinocyte proliferation driven by aberrant signaling through the epidermal growth factor receptor (EGF) receptor pathway (Gottlieb et al, 1988;Elder et al, 1989;Cook et al, 1992;Varani et al, 1998Varani et al, , 2001Piepkorn et al, 2003;Rittié et al, 2006), it was of interest to determine whether Bz-423 would reduce psoriatic keratinocyte hyperproliferation. To begin addressing this issue, we compared the effects of a topical formulation of Bz-423 with a potent topical steroid on human psoriatic skin transplanted onto severe, combined immunodeficient (scid) mice.…”