THE UNEXPECTED LINK BETWEEN IRON REGULATION AND HYPOSPERMATOGENESIS

Aileen HARRER¹, Noga GUTTMANN-RAVIV², Sudhanshu BHUSHAN¹, Esther G. MEYRON-HOLTZ², Andreas MEINHARDT¹, Niraj GHATPANDE², Tiziana GRIMALDINI¹, Daniela FIETZ³, Christiane PLEUGER¹, Monika FIJAK¹, Dankward FÖPPEL¹, Lennart RYNIO¹, Stefan A. WUDY⁴

¹Institute of Anatomy and Cell Biology, Unit of Reproductive Biology, Justus-Liebig-University of Giessen, Giessen, Germany
²Faculty of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
³Institute for Veterinary Anatomy, Histology and Embryology, Justus-Liebig-University of Giessen, Giessen, Germany
⁴Steroid Research and Mass Spectrometry Unit, Pediatric Endocrinology and Diabetology, Center of Child and Adolescent Medicine, Justus-Liebig-University of Giessen, Giessen, Germany

Imbalances in testicular iron levels have been associated with compromised sperm production and male infertility. Iron regulatory proteins (IRP) 1 and 2 plays cruicial roles in cellular in regulating the iron regulation. In the present study, we investigated the role of IRPs on archetypical testicular functions, i.e. spermatogenesis and steroidogenesis, by employing Irp1 (Irp1^-/-) and Irp2 (Irp2^-/-) defficient mice.

In Irp1^-/- testis, hypospermatogenesis was observed histologically exemplified by a clear reduction in the number of elongated spermatids and daily sperm production compared to wild-type (WT) and Irp2^-/- mice. In addition, stage 8 of spermatogenesis (sperm release) was reduced in testicular cross-sections of Irp1^-/-testis. Furthermore, flow cytometry analysis of germ cells derived from WT and Irp1^-/- showed that beside elongated spermatids all germ cell types were reduced in numbers, which was further confirmed by immunofluorescence. Notably, hypospermatogenesis worsened with age despite unchanged intratesticular iron levels. Although IRP1 was mainly localized to Sertoli cells in human biopsies and mouse testis cross-sections, Sertoli cell numbers remained similar in Irp1^-/- compared to WT testes. Levels of androgens (e.g. testosterone and corticosteron) as examined using mass spectrometry were unchanged across the investigated genotypes. Our initial results suggest impaired meiotic induction as a possible basis of hypospermatogenesis. Altogether, this study uncovers a novel role for IRP1 in maintaining germ cell survival and spermatogenesis, independent of iron regulation. These findings help to understand the complex interplay between iron regulation and critical testicular functions.