Analysis of thymic stromal cell subpopulations grown in vitro on extracellular matrix in defined medium. I. Growth conditions and morphology of murine thymic epithelial and mesenchymal cells.

Abstract

We report here the successful selective cultivation of murine thymic mesenchymal reticular cells (MTMC) and murine thymic epithelial cells (MTEC) grown on extracellular matrix in the presence of defined medium. The selective growth of these two cell types was based on 1) conditions of tissue disruption and 2) differential growth requirements. Both cell types were dependent on transferrin, high density lipoproteins, insulin, hydrocortisone, and epidermal growth factor, whereas MTMC was dependent also on selenium and 3,5,3'-triiodothyronine. The elimination of single factors or extracellular matrix resulted in specific and different changes in the growth pattern of each cell subpopulation. Cells of both types exhibited the ultrastructural features of high metabolic activity. The epithelial nature of MTEC cultures was defined by bundles of tonofilaments and desmosomes and by positive staining to keratins and negative to vimentin. In addition MTEC were positively stained with mAb to thymic medullary epithelial cells and by Ulex europeus agglutinin, and were able to form Hassall's corpuscles, suggesting their medullary origin. MTEC were also H-2 and Ia positive. In contrast MTMC were positive for vimentin and periodic acid-Schiff, low positive for H-2, and negative for keratin and Ia. Both cells did not contain nonspecific esterase, nor did they phagocytize latex beads. With the use of all these criteria we classified MTEC as epithelial cells from the medullary compartment of the thymus and MTMC as reticular cells of mesenchymal origin.

Induction of Apoptosis and p53 Expression in Immature Thymocytes by Direct Interaction with Thymic Epithelial Cells

“…NIH-3T3 fibroblast cell lines was the kind gift of Dr Salzberg, Bar-Ilan University, Ramat-Gan, Israel. Murine PTEC were established from thymic fragments dissociated by collagenase treatment and cultured on extracellular matrix coated dishes in a defined medium, as described previously [17]. Cell line no.…”

“…Thymic epithelial cells, as well as other stromal elements, have been suggested to be intimately involved in the many facets of T-cell differentiation [14,15]. We have demonstrated that stromal cells exert their effects by both direct contact and by the secretion of soluble factors [16][17][18][19][20][21]. However, the mechanism that underlies these activities is poorly understood.…”