Immunohistochemical localization of steroidogenic enzymes in human follicle following xenotransplantation of the human ovarian cortex into NOD-SCID mice

There have been reports of successful follicular growth following xenogenic transplantation of the human ovarian cortex into immunodeficient mice. In this study, we examined the immunohistochemical expression and localization of steroidogenic enzymes in the graft of nonpathological human ovary following xenogenic transplantation into nonobese diabetic severe combined immune deficient (NOD-SCID) mice. We studied human follicles following xenotransplantation into NOD-SCID mice using immunohistochemistry antibodies against the cell proliferation marker (Ki 67), steroidogenic enzymes P450 cholesterol side chain cleavage (P450 scc), 3β-hydroxysteroid dehydrogenase (3β-HSD), cytochrome P450 17α hydroxylase (P450 c17), cytochrome P450 aromatase (P450 arom), androgen receptor (AR), estrogen receptor (ER), and Ad4-binding protein (Ad4BP), a transcription factor for all steroidogenic P450 genes. In the pre-antral follicles of these grafts, Ki 67 and Ad4BP were detected in both the theca and granulosa cell layer. P450 scc, P450 c17, 3β-HSD, and AR were present in only the theca cell layer, observations of which were consistent with the findings of nonpathological human ovarian cortex. P450 arom and ER were not detected in these grafts, however, and these follicles did not possess any specific feature of a dominant follicle. These findings suggest that the expression of steroidogenic enzymes in human follicles following xenogenic transplantation into NOD-SCID mice is similar to that of nonpathological human ovaries. However, these follicles do not possess any features of dominant follicles, which are known to develop into the corpus luteum.