Epithelioid and fibroblastic cell lines derived from the ileum of an adult histocompatible miniature boar (d/d haplotype) and immortalized by SV40 plasmid.

Intestinal explants were maintained for weeks in a growth medium containing collagenase for progressive digestion to derive finite cell lines from the ileum (64 lines) or from the colon (8 lines) of a boar. Two ileal cell lines retaining either a fibroblastic or an epithelioid morphology have been used to derive heteroploid cell lines (IPI-1 and IPI-2) immortalized by transfection with an SV40 plasmid (pSV3-neo). The IPI-1 cells were found of fibroblastic lineage. The IPI-2 cell line gave rise to morphologically heterogeneous colonies ranging from typical epithelial cells to colonies of more-elongated cells. A crisis occurred during subcultivation of IPI-2 leading to the isolation of the IPI-2I cell line with a 24 h doubling time and a 21% plating efficiency. Epithelial nature of IPI-2I cells was supported by ultrastructural analysis of the cell monolayers. Differentiated cells were found to express microvilli at the apical cellular membrane and desmosomes connecting adjacent cells. Stable epithelioid phenotypes were obtained only from the IPI-2I cell line by multiple subcloning. These cells were found to express characteristics of both epithelial and mesenchymal cells by positive immunostaining with monoclonal antibodies reacting either with keratin 18 filament of simple epithelia or with vimentin filament typical in vivo of mesoderm. The lack of villin expression and the absence of transepithelial resistance have to be related to a poor differentiated state of this cell line. All these immortalized cell lines were permissive to the replication of microorganisms pathogenic for pig (Salmonella chloleraesuis, Salmonella typhimurium and tissue culture-adapted strains of transmissible gastroenteritis virus). The collection of finite and continuous cell lines will help to develop in vitro methods for long-term propagation of freshly isolated epithelium or three-dimensional organ culture in pig. In addition, the IPI-2I cell line provides a new model to study the conversion from a transformed to a nontransformed phenotype as incorporation of 2% dimethyl sulfoxide in the growth medium to repress large tumor antigen expression led to the progressive disappearance of cytokeratin 18 positive cells with, over a week, the death of the surviving vimentin-positive cells.