Estimating the Spermatogonial Stem Cell Population in Adult Mice Based on Response to Retinoic Acid
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Date
2024-05-01
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2026-05-01
Authors
Thomas, Matthew
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Abstract
ABSTRACT – The developmental program of spermatogenesis is based on a small population of spermatogonial stem cells (SSCs). Possessing the ability to produce daughter cells that either remain as SSCs (=self-renewal) or proliferate before committing to spermatogenesis, SSCs are ultimately responsible for the maintenance of the germline. SSCs are unipotent stem cells, and their progeny are ultimately committed to become sperm. This commitment occurs as proliferating spermatogonia differentiate in response to retinoic acid (RA). When the RA signal is received by spermatogonia, they express a transcription factor termed STRA8. In contrast, SSCs and early undifferentiated spermatogonia express the co-receptor GFRA1. Therefore, SSCs are identified by their expression of GFRA1 but not STRA8. In this study, 12 mice were treated with either vehicle-only (DMSO) or RA, and their testes were harvested 6-12 hours later. Testes sections were then immunostained for a variety of protein markers, including TRA98, STRA8, RARG, and GFRA1. Immunostained sections were imaged, and male germ cells expressing each protein were quantified using an open-source software program called QuPath. Results showed that STRA8 expression increased significantly 12 hours after RA treatment. Additionally, there were large differences between numbers of GFRA1+ spermatogonia. GFRA1+/STRA8- spermatogonia accounted for 0.14%-0.23% of the total germ cell population.. Based on an estimate of 4.6 x 107 TRA98+ germ cells in the adult mouse testis, this would mean between 6.4 x 104 - 1.06 x 105 germ cells were RA-insensitive GFRA1+/STRA8- SSCs.