Expression of 11beta-hydroxysteroid-dehydrogenase type 2 in human thymus.

ABSTRACT

11beta-hydroxysteroid-dehydrogenase type 2 (11ß-HSD2) is a high affinity dehydrogenase which rapidly inactivates physiologically-active glucocorticoids to protect key tissues. 11ß-HSD2 expression has been described in peripheral cells of the innate and the adaptive immune system as well as in murine thymus. In absence of knowledge of 11ß-HSD2 expression in human thymus, the study aimed to localize 11ß-HSD2 in human thymic tissue. Thymic tissue was taken of six healthy, non-immunologically impaired male infants below 12months of age with congenital heart defects who had to undergo correction surgery. 11ß-HSD2 protein expression was analyzed by immunohistochemistry and Western blot. Kidney tissue, peripheral blood mononuclear cells (PBMCs) and human umbilical vein endothelial cells (HUVEC) were taken as positive controls. Significant expression of 11ß-HSD2 protein was found at single cell level in thymus parenchyma, at perivascular sites of capillaries and small vessels penetrating the thymus lobuli and within Hassall's bodies. The present study demonstrates that 11ß-HSD2 is expressed in human thymus with predominant perivascular expression and also within Hassall's bodies. To our knowledge, this is the first report confirming 11ß-HSD2 expression at the protein level in human thymic tissue underlining a potential role of this enzyme in regulating glucocorticoid function at the thymic level.