Effect of 1.2 mmol/l calcium, triamcinolone acetonide, and retinoids on low-calcium regulated keratinocyte differentiation

Isolation and Culture of Primary Mouse Keratinocytes from Neonatal and Adult Mouse Skin

The keratinocyte (KC) is the predominant cell type in the epidermis, the outermost layer of the skin. Epidermal KCs play a critical role in providing skin defense by forming an intact skin barrier against environmental insults, such as UVB irradiation or pathogens, and also by initiating an inflammatory response upon those insults. Here we describe methods to isolate KCs from neonatal mouse skin and from adult mouse tail skin. We also describe culturing conditions using defined growth supplements (dGS) in comparison to chelexed fetal bovine serum (cFBS). Functionally, we show that both neonatal and adult KCs are highly responsive to high calcium-induced terminal differentiation, tight junction formation and stratification. Additionally, cultured adult KCs are susceptible to UVB-triggered cell death and can release large amounts of TNF upon UVB irradiation. Together, the methods described here will be useful to researchers for the setup of in vitro models to study epidermal biology in the neonatal mouse and/or the adult mouse.

Isolation and characterization of an immortalized oral keratinocyte cell line of mouse origin

OBJECTIVE

To establish an oral epithelial cell line of mouse origin for molecular and biochemical assays.

DESIGN

Epithelial cells were isolated from the oral cavity of adult mice and established as a spontaneously immortalized cell line in culture, designated immortalized oral keratinocyte cells (IMOK cells). The cells were then characterized for growth characteristics, differentiation potential, karyotype, transfectability, susceptibility to viral infection and responses to siRNA.

RESULTS

The IMOK cells exhibit robust growth in both serum-containing and serum-free medium for at least 100 population doublings. IMOK cells have a near diploid karyotype, express keratinocyte marker proteins and can be induced to undergo differentiation by the addition of high levels of calcium to the medium. The differentiation process is characterized by morphological changes and by the induction of oral epithelium specific differentiation marker proteins such as K4 and K13. Transient transfection analyses reveal that IMOK cells are highly transfectable and that several promoters of epithelial cells are active in these cells. Moreover, upon differentiation with calcium, there is an up-regulation of differentiation-specific K4 and Elf5 promoter activity. Finally, we show that the oral keratinocytes are also amenable to infection with retroviruses and to siRNA-based knockdown of gene expression.

CONCLUSIONS

Our study is the first to establish an immortalized oral keratinocyte cell line of murine origin that can recapitulate the oral epithelium differentiation program and thus could serve as a useful tool for toxicological and molecular analyses of the oral tissue.

Increased calmodulin levels in psoriasis and low Ca++ regulated mouse epidermal keratinocyte cultures

Calcium has been shown to regulate the proliferation of epidermal keratinocytes in vitro. We became interested in the role of the calcium binding protein, calmodulin, in hyperproliferative, low calcium regulated keratinocytes in vitro and in the in vivo hyperproliferative state, psoriasis. Calmodulin levels were measured by radioimmune assay in neonatal mouse keratinocytes grown in 0.02 mM calcium (hyperproliferative) and 1.2 mM calcium (normal) media, and in cells that had been grown in low calcium medium and then switched to normal calcium. On a whole culture basis the normal cells had more calmodulin than the low calcium cells. However, when low calcium monolayers were compared to the normal basal monolayer, the low calcium hyperproliferative cells had more calmodulin. Cells that were switched from 0.02 mM calcium to 1.2 mM calcium showed increasing calmodulin levels over time. Psoriatic plaques contained 2-3 times more calmodulin than the skin of normal controls when examined on a per micrograms of DNA, per micrograms of protein, and per gram of wet weight basis. Adjacent uninvolved psoriatic skin also had significantly elevated calmodulin levels in all data bases except per microgram of protein/cm2. These data suggest that increased calmodulin levels are associated with epidermal hyperproliferation and/or with the state of differentiation.