Constitutive and modulated cytokine expression in two permanent human bone marrow stromal cell lines

We present a detailed analysis of cytokine expression patterns of the two permanent human bone marrow stromal cell lines, L87/4 and L88/5. These cell lines, previously established in our laboratory, are highly radiotolerant without cell detachment and support long-term cultures of CD34⁺-enriched human cord blood cells. RT-PCR analysis of 22 different cytokines or cytokine receptor mRNAs showed an almost identical expression pattern in the two stromal cell lines compared to primary human Dexter-type stroma. Since stromal feeder lines employed in long-term cultures usually are irradiated and grown in media containing corticosteroids, we analyzed the impact of irradiation and dexamethasone on cytokine production in the two cell lines by RT-PCR, Northern blot analysis, bioassays, and RIAs. By RT-PCR analysis, constitutive mRNA expression of c-kit, G-CSF, GM-CSF, IL1β, IL-6, IL-7, IL-8, IL-11, Kit ligand (KL), LIF, M-CSF, MIP-1α, TGF-β, and TNF-α was demonstrated in both cell lines, with L87/4 a more potent cytokine producer than L88/5. Northern blot data showed an increase in mRNA levels for GM-CSF, IL-1β, and LIF by irradiation and IL-1α treatment in both cell lines. IL-1α-induced GM-CSF, IL-1β, IL-6, IL-11, and LIF mRNA levels were reduced by the addition of dexamethasone, whereas dexamethasone had no influence on the amounts of IL-1α-induced G-CSF mRNA. L87/4 and, to a lower extent, L88/5 cells showed dexamethasone-dependent increases in IL mRNA, while KL mRNA levels were not stimulated by IL-1α.