Fetal growth plays a role in programming of adult cardiometabolic disorders, which in men, are associated with lowered testosterone levels. Fetal growth and fetal androgen exposure can also predetermine testosterone levels in men, although how is unknown, because the adult Leydig cells (ALCs) that produce testosterone do not differentiate until puberty. To explain this conundrum, we hypothesized that stem cells for ALCs must be present in the fetal testis and might be susceptible to programming by fetal androgen exposure during masculinization. To address this hypothesis, we used ALC ablation/regeneration to identify that, in rats, ALCs derive from stem/progenitor cells that express chicken ovalbumin upstream promoter transcription factor II. These stem cells are abundant in the fetal testis of humans and rodents, and lineage tracing in mice shows that they develop into ALCs. The stem cells also express androgen receptors (ARs). Reduction in fetal androgen action through AR KO in mice or dibutyl phthalate (DBP) -induced reduction in intratesticular testosterone in rats reduced ALC stem cell number by ∼40% at birth to adulthood and induced compensated ALC failure (low/normal testosterone and elevated luteinizing hormone). In DBP-exposed males, this failure was probably explained by reduced testicular steroidogenic acute regulatory protein expression, which is associated with increased histone methylation (H3K27me3) in the proximal promoter. Accordingly, ALCs and ALC stem cells immunoexpressed increased H3K27me3, a change that was also evident in ALC stem cells in fetal testes. These studies highlight how a key component of male reproductive development can fundamentally reprogram adult hormone production (through an epigenetic change), which might affect lifetime disease risk.adult Leydig stem/progenitor cells | compensated Leydig cell failure | GATA4 | ethane dimethane sulfonate

Among pregnant women ibuprofen is one of the most frequently used pharmaceutical compounds with up to 28% reporting use. Regardless of this, it remains unknown whether ibuprofen could act as an endocrine disruptor as reported for fellow analgesics paracetamol and aspirin. To investigate this, we exposed human fetal testes (7–17 gestational weeks (GW)) to ibuprofen using ex vivo culture and xenograft systems. Ibuprofen suppressed testosterone and Leydig cell hormone INSL3 during culture of 8–9 GW fetal testes with concomitant reduction in expression of the steroidogenic enzymes CYP11A1, CYP17A1 and HSD17B3, and of INSL3. Testosterone was not suppressed in testes from fetuses younger than 8 GW, older than 10–12 GW, or in second trimester xenografted testes (14–17 GW). Ex vivo, ibuprofen also affected Sertoli cell by suppressing AMH production and mRNA expression of AMH, SOX9, DHH, and COL2A1. While PGE2 production was suppressed by ibuprofen, PGD2 production was not. Germ cell transcripts POU5F1, TFAP2C, LIN28A, ALPP and KIT were also reduced by ibuprofen. We conclude that, at concentrations relevant to human exposure and within a particular narrow ‘early window’ of sensitivity within first trimester, ibuprofen causes direct endocrine disturbances in the human fetal testis and alteration of the germ cell biology.

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