Tenascin-C Induction in Whitlock-Witte Culture: A Relevant Role of the Thiol Moiety in Lymphoid-Lineage Differentiation

The extracellular matrix (ECM) glycoprotein tenascin-C is expressed in a temporally and spatially restricted pattern during embryogenesis and carcinogenesis in association with stromal-epithelial interactions. First, we investigated the production of tenascin-C and other ECM glycoproteins in the established in vitro model system specific for the lymphoid-lineage hemopoiesis, i.e., the Whitlock-Witte (W-W) culture system. In murine primary long-term bone marrow cultures, tenascin-C was produced constitutively and was expressed significantly in higher amounts in this system than in the other established in vitro model system specific for the myeloid-lineage hemopoiesis, i.e., the Dexter culture system. 2-Mercaptoethanol (2-ME), a component of the W-W system, induced the secretion of tenascin-C and upregulated the expression of its mRNA. Furthermore, the reduced glutathione, which, like 2-ME, contains a thiol moiety, induced tenascin-C glycoprotein and its mRNA. By contrast, hydrocortisone (HC), a component of the Dexter system, inhibited the secretion of ECM glycoproteins. 2-ME and TGF-β1, the latter of which is known as an inducer of ECM glycoproteins, had an additive effect on the induction of tenascin-C when they were simultaneously added to the W-W system. The TGF-β receptor binding analysis demonstrated that this induction by 2-ME was not mediated by the cell-surface TGF-β receptors, suggesting that it was regulated independently of TGF-β1. Then, the role of thiol compounds in the lymphoid-lineage differentiation was examined. The omission of 2-ME from the W-W system completely eliminated its ability to support the lymphoid-lineage differentiation. Glutathione, which, unlike 2-ME, does not passively permeate through the plasma membrane, did not support the development of a lymphoid lineage. These results indicate that 2-ME, essential for the lymphoid-lineage differentiation in the W-W culture system, is a potent inducer of tenascin-C expression in vitro.