Reduced expression of stromal-derived factor 1 in autonomous thyroid adenomas and its regulation in thyroid-derived cells

Stromal-derived factor 1 (SDF-1) and CXCR4 comprise a unique chemokine/chem okine receptor pair, exhibiting important functions in morphogenesis and gr owth regulation as well as attractant properties on T lymphocytes. No data are available on SDF-1 and CXCR4 in normal or pathological thyroid tissues. SDF-1, CXCR4, and CD18 messenger ribonucleic acid (mRNA) as a marker of leu kocytic infiltration ere quantified in tissues affected by thyroid adenoma (n = 11) and Graves ' disease (GD; n 16) using competitive RT-PCR. SDF-1 mR NA levels differed significantly between autonomous adenomas and the corres ponding normal tissue, but not in GD between patients with low or high leuk ocyte infiltration, thyroid peroxidase, and TSH receptor autoantibodies, re spectively. We found a strong correlation between CXCR4 and CD18 mRNA, whic h indicates CXCR4 expression by leukocytes. To define the cellular source of SDF-1 and CXCR4 in thyroid tissue, we exam ined various thyroid-derived cells. Fibroblasts are the most potent produce rs of SDF-1, although thyrocytes also secrete SDF-1 in vitro. Leukocytes sh owed very weak SDF-1 mRNA levels and no secretion of the chemokine. Immunoh istology confirmed and extended these results; SDF-1 expression was found i n fibroblasts, but not or very weakly in CD45(+) leukocytes and thyrocytes. Only leukocytes were CXCR4(+). As examined by now cytometry, the number of CD3(+) T cells expressing CXCR4 is significantly higher in the thyroid tha n in peripheral blood. SDF-1 seems to be involved in thyroid tissue homeostasis in thyroid adenoma , but not in the maintenance of lymphocytic infiltration in GD.