Male infertility and testicular cancer are significant health issues, and these conditions may stem from disrupted communication between testicular somatic (especially Sertoli cells) and germ cells (gonocytes) during embryogenesis. In the fetal mouse testis, the absence of activin A (Inhba KO) results in reduced Sertoli cell and increased gonocyte numbers (1). In this study we sought to clarify whether increased activin A (Inha KO) levels regulate fetal testis development, since elevated activin A is associated with complications during human pregnancy . Using indirect immunofluorescence with cell-specific markers we quantified Sertoli cell (Sox9+) and gonocyte (Ddx4+) populations, and testis cord formation, in sections of Inha and Inhba embryonic (E; E13.5 and E15.5) and newborn (0 dpp) mouse testes, comparing KO and wild type (WT) for each strain. Three sections were selected from the middle of the testis, spaced > 50 mm, from 3 - 4 animals/age/genotype. Slides were scanned (Olympus VS120® Virtual Slide Microscope System), images calibrated prior to measurements using ImageJ (2), and data collected blind.
The measured outcomes were opposite for increased and decreased activin A levels. Inha KO testes (elevated activin A) had: 1) a higher ratio of Sertoli cells to gonocytes, 2) gonocytes in the interstitium (only at E15.5), and 3) an increase in multinucleated cells at E15.5 and 0 dpp. These findings indicate that elevated activin A can result in gonocytes escaping the testis cords, and drive the phenotype of multinucleated gonocytes which is observed following exposure to endocrine disruptor chemicals and potentially linked with cryptorchidism in boys (3). The discovery that systemic activin A elevation can cause dysgenic testicular development in mice between E13.5 and birth provides evidence that pregnancy conditions which feature elevated activin A may impact male reproductive health later in life.