Four techniques for dissociation of skin biopsies were compared to identify the method of choice for optimal expansion of isolated keratinocytes. Equivalent biopsies were obtained from 4 healthy human subjects and each divided into four parts. One part was minced and placed in a trypsinizing flask containing 0.05% trypsin and 0.01% ethylenediaminetetraacetic acid (EDTA). Released cells were harvested hourly. With the other parts, the epidermis was separated from the dermis after treatment with 0.5 mg/nml thermolysin, 2.5 mg/ml Dispase, or 0.17% trypsin and the epidermal portions were minced and incubated for 1 h in trypsin:EDTA. The cells were cocultivated with irradiated 3T3 fibroblasts to study the keratinocytes proliferative capacity. Freshly isolated cells were immunostained with anti-vimentin antibodies or grown in fibroblast-supportive conditions to detect the presence of human dermal fibroblasts. The mean number of cells dissociated per cm2 biopsy was higher after trypsin:EDTA digestion of a dermis-containing biopsy using a trypsinizing flask (4.0x 10(6) cells/cm2) compared to a biopsy where dermis-epidermis had been separated by thermolysin (2.8x 10(6) cells/cm2), Dispase (2.3x 10(6) cells/cm2) or trypsin (1.1 x 10(6) cells/cm2). Between 0.5% and 4% of the cells dissociated from a dermis-containing biopsy were human fibroblasts. This comprised more than twice the number of fibroblasts obtained by using epidermal/dermal split techniques. The proliferative capacity in primary and secondary culture was higher in cells isolated by trypsin:EDTA incubation in the trypsinizing flask or after epidermal-dermal separation using thermolysin, suggesting that Dispase or trypsin may have a more detrimental effect on the isolated keratinocytes. Our results show that dissociating the cells by trypsin:EDTA incubation in a trypsinizing flask or after epidermal-dermal separation using thermolysin, are preferable methods for isolating keratinocytes from human skin.

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Epithelial inflammation may play an obligatory role in the pathogenesis of a number of chronic pulmonary diseases such as asthma or bronchitis and has been implicated during the promotion phase of multistage carcinogenesis. At sites of inflammation, bioactive lipid mediators are released and activate a wide range of pathophysiological responses including bronchospasm. Previous studies suggest that one class of inflammatory mediators, the eicosanoids, can also influence cell growth. Epithelial cell proliferation and hyperplasia are common sequelae to irritation and inflammation, and because the lung has a high capacity to produce eicosanoids, we investigated the effects of a group of these compounds, the cysteinyl leukotrienes, on growth of human airway epithelial cells. Leukotrienes were found to be mitogenic in a concentration-dependent manner and exhibit a structure-activity relationship, with leukotriene C4 being more potent than its sequential metabolites leukotriene D4 and E4. The potency of leukotriene C4 is striking, stimulating colony-forming efficiency in concentrations as low as 10 fM. These findings suggest a new physiological role for leukotrienes in the lung that links inflammation with epithelial cell proliferation.

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