Oral Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

Activin A modulates the pace of murine germ cell development and promotes a niche that supports spermatogonial stem cell self-renewal (#192)

Penny Whiley 1 2 , Robin Hobbs 1 2 , Kate Loveland 1 2
  1. Centre for Reproductive Health, Hudson Institute of Medical Research, Clayton, Vic, Australia
  2. Department of Molecular and Translational Sciences, SubFaculty of Clinical and Molecular Medicine. Monash University, Clayton, VIC, Australia

Elevated circulating activin A (AA) features in pathological conditions including pre-eclampsia1, cancer cachexia2 and infections3. It has the potential to affect male fertility by influencing somatic cell proliferation, limiting steroid production, and reducing germ cell survival in fetal mouse testes4,5,6,7. This study demonstrates AA effects on spermatogonial stem cell (SSC) establishment and postnatal spermatogonial fate.

We examined spermatogonia/SSCs in neonate (P0/P3/P6) and adult InhaKO mouse testes (lacking inhibin ⍺8; unopposed AA signalling). Using immunofluorescence and whole-testis RNAseq (WT/KO, n=3-5/age/genotype), SSCs (GFRA1+/Gfra1), spermatogonia (SALL4+/Sall4), and their proliferation status (Ki67+/Mki67) were examined. Activin signalling was manipulated in E17.5 WT testis fragments cultured (72hr) with 50ng/mL AA or 10µM SB431542 (activin/TGFβ/Nodal inhibitor) (n=5-7 fragments/treatment); germ cell-number, proliferation, and location were scored. Undifferentiated spermatogonia (adult testis-derived) were cultured with 5 and 50ng/mL activin A for 6/24hr (n=4/treatment/timepoint).

Although P0 InhaKO testes had 50% fewer germ cells than WT, a higher proportion of remaining germ cells were GFRA1+/Ki67+, suggesting advanced development. This was supported by ex vivo testis cultures in which elevated AA enhanced germ cell migration before birth. At P6, when the SSC population is fully established, we observed a higher proportion of GFRA1+ cells, indicating conditions in InhaKO testes favour SSC formation. However, SSC-associated transcripts were unaltered in AA-cultured spermatogonia, indicating either an age difference or that this outcome is not a direct response to AA. SSCs were also more abundant and proliferative in adult InhaKO testes, suggesting chronic AA elevation promotes a niche that supports SSC self-renewal long-term. Importantly, in adult InhaKO testes, tubules adjacent to its somatic cell tumours were enriched in transcripts encoding growth factors that support SSCs proliferation.

These combined results suggest a heightened risk to adult male fertility may arise as a consequence of either fetal or infant testicular exposure to elevated AA.

  1. Reddy A et al. PLoS One (2009)
  2. Loumaye et al. J Clin Endocrinol Metab (2015)
  3. Hardy J et al. JCEM (2016)
  4. Mendis et al. Biol Repro (2011)
  5. Archembeault et al. PNAS (2010)
  6. Whiley et al. Endocrinology (2020)
  7. Whiley, Luu et al. Front Endocrinol (2023)
  8. Matzuk et al. Nature (1992)