Origin and Differentiation of Androgen-Producing Cells in the Gonads

Taste receptor type 1 member 3 is required for the fertility of male mice

Male infertility is a global health concern. However, its underlying pathophysiology remains unclear. Taste receptor type 1 member 3 (TAS1R3) is highly expressed in the testes, indicating its potential involvement in male fertility. Using wild-type and Tas1r3 knockout (KO) mice, we investigated whether TAS1R3 modulates male reproductive function. Tas1r3 KO mice exhibited reduced male fertility compared to WT mice, with fewer live pups per litter and a delayed first litter. Testicular transcriptome analysis indicated suppressed PKA/CREB/StAR signaling-mediated testosterone synthesis in Tas1r3 KO mice. In silico single-cell RNA sequencing revealed considerably higher Tas1r3 expression in Leydig cells than in other testicular cell subtypes. An in vitro study validated that Tas1r3 knockdown downregulated the expression of Creb1 and steroidogenic genes in Leydig cells. Our results suggest that testicular TAS1R3 is intricately involved in male reproduction via the PKA/CREB/StAR signaling pathway, highlighting its potential as a promising target for addressing male infertility.

DNA methylation-mediated inhibition of MGARP is involved in impaired progeny testosterone synthesis in mice exposed to DBP in utero

The dibutyl phthalate (DBP) has been detected in fetuses and infants and can cause damage to the reproductive system in adulthood, but the exact mechanism remains unclear. Here, we aim to investigate the effects of intrauterine DBP exposure on offspring reproductive function and explore possible mechanisms. SPF C57BL/6 pregnant mice were given DBP (0.5, 5, 75 mg/kg/d) or corn oil from day 5 to day 19 by gavage. After weaning, the pups were fed a standard diet for 5 weeks. In addition, TM3 Leydig cell cultures were used to study the relevant mechanisms in vitro. The results showed that intrauterine DBP exposure could reduce sperm density and sperm motility, cause testicular tissue damage, down-regulate serum T and LH levels, and up-regulate serum FSH levels at 75 mg/kg/d. Western blot and methylation detection revealed intrauterine exposure to DBP down-regulated testosterone synthesis-related proteins StAR, P450scc, 3β-HSD, PKA, and PKC expression, while up-regulated the levels of methyltransferase proteins expression and DNA 5-methylcytosine (5mC) in testicular tissue of mouse offspring at 75 mg/kg/d. Further detection found in utero 75 mg/kg/d DBP exposure down-regulated MGARP protein expression, and induced incomplete methylation of the MGARP gene. An in vitro analysis showed that MGARP inhibition is involved in an impaired testosterone synthesis in TM3 cells. Cell culture results suggest that MGARP down-regulation may be involved in impaired testosterone production in monobutyl phthalate-treated cells. The present study revealed that 75 mg/kg/d DBP exposure in utero resulted in testosterone synthesis disorders and reproductive function impairment in mouse offspring, and the mechanism may be related to DNA methylation-mediated down-regulation of MGARP in the testis.

Aberrant activation of KRAS in mouse theca-interstitial cells results in female infertility

KRAS plays critical roles in regulating a range of normal cellular events as well as pathological processes in many tissues mediated through a variety of signaling pathways, including ERK1/2 and AKT signaling, in a cell-, context- and development-dependent manner. The in vivo function of KRAS and its downstream targets in gonadal steroidogenic cells for the development and homeostasis of reproductive functions remain to be determined. To understand the functions of KRAS signaling in gonadal theca and interstitial cells, we generated a Kras mutant (tKrasMT) mouse line that selectively expressed a constitutively active KrasG12D in these cells. KrasG12D expression in ovarian theca cells did not block follicle development to the preovulatory stage. However, tKrasMT females failed to ovulate and thus were infertile. The phosphorylated ERK1/2 and forkhead box O1 (FOXO1) and total FOXO1 protein levels were markedly reduced in tKrasMT theca cells. KrasG12D expression in theca cells also curtailed the phosphorylation of ERK1/2 and altered the expression of several ovulation-related genes in gonadotropin-primed granulosa cells. To uncover downstream targets of KRAS/FOXO1 signaling in theca cells, we found that the expression of bone morphogenic protein 7 (Bmp7), a theca-specific factor involved in ovulation, was significantly elevated in tKrasMT theca cells. Chromosome immunoprecipitation assays demonstrated that FOXO1 interacted with the Bmp7 promoter containing forkhead response elements and that the binding activity was attenuated in tKrasMT theca cells. Moreover, Foxo1 knockdown caused an elevation, whereas Foxo1 overexpression resulted in an inhibition of Bmp7 expression, suggesting that KRAS signaling regulates FOXO1 protein levels to control Bmp7 expression in theca cells. Thus, the anovulation phenotype observed in tKrasMT mice may be attributed to aberrant KRAS/FOXO1/BMP7 signaling in theca cells. Our work provides the first in vivo evidence that maintaining normal KRAS activity in ovarian theca cells is crucial for ovulation and female fertility.

Dhh signaling pathway regulates reconstruction of seminiferous tubule-like structure

The reconstruction of a tubule-like structure in vitro has provided a promising system to analyze factors that drive morphogenesis and the underlying mechanisms. In this study, we took advantage of the inhibitor cyclopamine and a smoothened agonist to detect the role of the Dhh signaling pathway in the reconstructed tubule-like structure. Sertoli cells did not show polarity, rounded peritubular myoid cells and scattered Leydig cells were observed, combined with less laminin and lower proliferation of Leydig, peritubular myoid, germ, and Sertoli cells. However, in the presence of SAG, elongated peritubular myoid cells gathered at the bottom of polarized Sertoli cells, and most of the Leydig cells gathered at the outer part of the elongated peritubular myoid cells. Moreover, SAG promoted the secretion of laminin, assisting in the formation of the basal membrane and promoting the proliferation of Leydig, peritubular myoid, and germ cells. The level of Gli1 was significantly downregulated when treated with cyclopamine, whereas it was significantly upregulated when treated with SAG. These results indicate that the Dhh signaling pathway regulates the reconstruction of tubule-like structures by regulating the expression of Gli1.

Atrazine impairs testicular function in BalB/c mice by affecting Leydig cells

Several studies have reported the effects of atrazine on the gonads of many experimental models. However, the short-term effects of in vivo exposure to atrazine on the testes of mice are not well clarified. Here we reported that adult BalB/c mice exposed to atrazine (50 mg kg^-1 body weight) by gavage for three consecutive days have reduced numbers of 3β-hydroxysteroid dehydrogenase positive Leydig cells (LCs), associated with increased in situ cell death fluorescence and caspase-3 immuno-expression in the testes. Consequently, immunostaining for cell cycle gene regulators showed increased expressions of p45, accompanied with increased expressions of cyclin D2 and E2. Histological observations of the gonads showed reduced number of germ cells in particular areas, sloughed seminiferous epithelium, presence of giant apoptotic cells close to the seminiferous tubule lumen and in the epididymal lumen along with low numbers of Leydig cells in the testicular interstitial areas. Similarly, LCs isolated from the testes of BalB/c mice that were exposed to atrazine (0.5, 25, 50 mg kg^-1 body weight) in the same manner as in the first experiment presented dose-dependent increased caspase-3 activity, decreased cell viability, intratesticular and serum testosterone concentrations and LCs testosterone secretion. In summary, atrazine appears to directly decrease the number of testosterone secreting LCs in mice through apoptosis.

The Insulin/IGF System in Mammalian Sexual Development and Reproduction

Persistent research over the past few decades has clearly established that the insulin-like family of growth factors, which is composed of insulin and insulin-like growth factors 1 (IGF1) and 2 (IGF2), plays essential roles in sexual development and reproduction of both males and females. Within the male and female reproductive organs, ligands of the family act in an autocrine/paracrine manner, in order to guide different aspects of gonadogenesis, sex determination, sex-specific development or reproductive performance. Although our knowledge has greatly improved over the last years, there are still several facets that remain to be deciphered. In this review, we first briefly outline the principles of sexual development and insulin/IGF signaling, and then present our current knowledge, both in rodents and humans, about the involvement of insulin/IGFs in sexual development and reproductive functions. We conclude by highlighting some interesting remarks and delineating certain unanswered questions that need to be addressed in future studies.

Effect of maternal folic acid supplementation on prostatitis risk in the rat offspring

PURPOSE

Folic acid (FA) intake has increased to high levels in many countries for the prevention of neural tube defects. However, the impact of excess FA intake, particularly before and during pregnancy, requires further investigation. Our aim was to investigate the effect of maternal folic acid supplementation on prostatitis risk in the rat offspring.

METHODS

Female SD rats were administrated with different doses of FA by oral gavage from 2 weeks prior to mating to GD14: 0 mg/kg (distilled water), 0.2 mg/kg FA and 2.0 mg/kg FA respectively. The male rat offspring from each maternal FA group were castrated on PND56 and injected different doses of 17β-estradiol (E₂) subcutaneously for 30 days to induce prostatitis: 0 mg/kg (corn oil) and 1.25 mg/kg E₂ respectively. At necropsy, the prostates were collected for histopathological analysis. Fasting blood was collected for the determination of serum E₂, T, DHT, and folic acid levels. The expression of TNF-α, COX-2, and ER-α was determined by immunohistochemistry.

RESULTS

High-dose (2.0 mg/kg) maternal folic acid supplementation significantly increased the proportion of prostatitis in FA(2.0) + E₂(1.25) group (87.5%) compared with FA(0) + E₂(1.25) group (25%). The inflammation was focal and severe, and large amounts of inflammatory cells appeared in different regions of the prostate in FA(2.0) + E₂(1.25) group. The serum T, DHT, and FA levels in FA(2.0) + E₂(1.25) group were significantly higher than those in FA(0) + E₂(1.25) group. The expression of TNF-α, COX-2, and ER-α in three 1.25 mg/kg E₂ groups presented positive, and the number and distribution of positive cells increased as FA dosage increased.

CONCLUSIONS

Our findings suggest that high-dose (2.0 mg/kg) maternal folic acid supplementation significantly increases the proportion of prostatitis and the prostatic inflammation is more obvious and severe in the rat offspring.

Persistent testicular structural and functional alterations after exposure of adult rats to atrazine

Atrazine is an endocrine disruptor affecting testicular steroidogenesis, and promoting testicular atrophy and 3β-HSD reduction. However, it remains unknown whether these effects are reversible or permanent. To address this issue was the aim of this study. Exposition of rats to 200mg/kg of atrazine resulted in transient increase in testicular weight, seminiferous tubules dilation and atrophy, and reduction in Leydig cell 3β-HSD. Testicular atrophy and 3β-HSD reduction were more pronounced after the recovery period of 75days. There was increase in aromatase expression after long-term exposure but it returned to control level after recovery. Moreover, there was increase in ED1^-/ED2⁺, ED1⁺/ED2⁺ and ED1⁺/ED2^- macrophages, in the recovery group. These macrophages were positive for 3β-HSD, thereby raising possibility of their involvement in steroidogenesis. These findings further emphasize the adverse effects of atrazine on male reproduction, highlighting that testicular damages may be irreversible even after a recovery period longer than the spermatogenic cycle.