Expression of type 2 11β-hydroxysteroid dehydrogenase and corticosteroid hormone receptors in early human fetal life

In adult life, the type 2 isozyme of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD2) protects the mineralocorticoid receptor (MR) from glucocorticoid by inactivating cortisol to cortisone. 11 beta HSD2 activity has been reported in human fetal tissues, where glucocorticoids may impair fetal growth yet are also required for normal fetal development. Using digoxigenin-labeled complementary ribonucleic acid (RNA) probes and an in-house 11 beta HSD2 antiserum, we have analyzed the expression of 11 beta HSD2, MR, and glucocorticoid receptor (GR) in human fetal tissues of gestational age 6-17 weeks (n = 15). 11 beta HSD2 expression was absent at gestational age 6+ weeks, but was expressed in abundance in many fetal tissues between 8-12 weeks. At this time, 11 beta HSD2 colocalized with GR messenger RNA (mRNA) expression in metanephros, gut, muscle, spinal cord and dorsal root ganglia, periderm, sex chords of testis, and adrenal. In particular within fetal kidney, intense expression of 11 beta HSD2 and GR mRNA was observed over Bowman's capsule and the vascular tufts of developing glomeruli as they migrated from the surface of the kidney to the inner cortex. Only lung and adrenal medullary rests demonstrated high levels of GR mRNA but low levels of 11 beta HSD2. 11 beta HSD2 mRNA and immunoreactivity staining patterns were similar, with the exception of the fetal adrenal, where mRNA was localized to the outer definitive zone but immunoreactivity was localized to the inner fetal zone. Colocalization of 11 beta HSD2 (and GR mRNA) with MR mRNA was observed principally within epithelial cells of collecting ducts, particularly after 16 weeks gestation when the pattern of distribution of 11 beta HSD2 became more adult in nature. High levels of MR mRNA were observed within developing bone. The data indicate that 11 beta HSD2 in fetal life principally modulates ligand access to the GR in most fetal tissues, notably glomeruli and tubules in the developing kidney, testis, and periderm, and this may be have ramifications for fetal sodium homeostasis and differentiation. The development of tissues previously shown to have a critical requirement for glucocorticoids, such as lung and adrenal medulla, is facilitated by the expression of GR mRNA, but not 11 beta HSD2. The expression of MR mRNA in high abundance in bone suggests a role for corticosteroids in human bone development, and the low/absent expression of 11 beta HSD2 at this site suggests that it is functionally acting as a GR.