Androgen receptor (AR) physiological roles in male and female reproductive systems: lessons learned from AR-knockout mice lacking AR in selective cells

The regulation of spermatogenesis by androgens

Testosterone is essential for maintaining spermatogenesis and male fertility. However, the molecular mechanisms by which testosterone acts have not begun to be revealed until recently. With the advances obtained from the use of transgenic mice lacking or overexpressing the androgen receptor, the cell specific targets of testosterone action as well as the genes and signaling pathways that are regulated by testosterone are being identified. In this review, the critical steps of spermatogenesis that are regulated by testosterone are discussed as well as the intracellular signaling pathways by which testosterone acts. We also review the functional information that has been obtained from the knock out of the androgen receptor from specific cell types in the testis and the genes found to be regulated after altering testosterone levels or androgen receptor expression.

Low testosterone levels in women with diminished ovarian reserve impair embryo implantation rate: a retrospective case-control study

OBJECTIVE

To investigate the association of basal testosterone (T) levels with the outcome of in vitro fertilization (IVF) in women with diminished ovarian reserve (DOR).

METHODS

Complete clinical data on the first 223 IVF cycles in women with DOR were retrospectively analyzed. The associations of basal follicle stimulating hormone, luteinizing hormone, estradiol, and T levels with ovarian response and IVF outcome were studied.

RESULTS

Basal T levels were significantly different between pregnant and non-pregnant women. However, basal T levels showed no correlation with controlled ovarian hyperstimulation parameters after adjusting for age. The association of basal T levels with pregnancy rate was significant after adjusting for other impact factors. Using receiver operating characteristic (ROC) analysis, the basal T level of 1.115 nmol/L for predicting pregnancy outcome had a sensitivity of 82.80 % and specificity of 58.09 %. The women were divided into two groups based on this value; although the clinical characteristics and ovarian stimulation parameters were similar, the clinical pregnancy (16.18 % (11/68) vs. 40.15 % (53/132), respectively, p = 0.000) and implantation rates (10.07 % (15/149) vs. 22.41 % (65/290), respectively, p = 0.002) were significantly different in the low and high T level groups.

CONCLUSION

In women with DOR, the basal T level presented a positive association with pregnancy outcome in IVF. The poor reproductive outcome observed in women with lower basal T levels may be due to the decreased implantation rate.

AR3 messenger ribonucleic acid expression and its functional implication in human primary testicular failure

AR3, a major one of androgen receptor (AR) splice variants, has been shown to play a pivotal role in concert with AR signalling in prostate cancer. The present study was undertaken to characterise the expression pattern of AR3 in normal and impaired spermatogenesis. Expression of AR3 mRNA showed significantly lower level in testicular tissues with impaired spermatogenesis when compared to normal tissues. This aberrant expression profile of AR3 in human pathological testes was further confirmed by immunoblotting analysis. Moreover, in situ hybridisation studies revealed that the transcripts of the gene were dominantly localised in the pachytene spermatocytes and round spermatids, suggesting a potential involvement of this transcriptional regulator in the auto-/paracrine regulation of meiotic and post-meiotic differentiation. This hypothesis was strengthened by the observation that AR3 mRNA expression was positively correlated to average seminiferous tubule score and was negatively correlated to serum FSH level. To the best of our knowledge, such a distinct expression profile of AR3 has not been reported previously in human testis. Overall, our data are suggestive of a novel site of action of AR3 during human spermatogenesis and should shed light on the complicated circuit composed of AR and its splice variants.