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Targeted inactivation of the androgen receptor gene in murine proximal epididymis causes epithelial hypotrophy and obstructive azoospermia.

Krutskikh A, De Gendt K, Sharp V, Verhoeven G, Poutanen M, Huhtaniemi I - Endocrinology (2010)

Bottom Line: The epithelial lining of the epididymal duct expresses the androgen receptor (Ar) along its entire length and undergoes rapid and profound degeneration when androgenic support is withdrawn.At 20-25 d of life, on the onset of Rnase10 expression, Ar became selectively inactivated in the principal cells of proximal epididymis, resulting in epithelial hypoplasia and hypotrophy.Our findings demonstrate that the development and function of the epididymal initial segment is critically dependent on direct androgen regulation.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery and Cancer, Imperial College London, London W12 0NN, United Kingdom.

ABSTRACT
The epithelial lining of the epididymal duct expresses the androgen receptor (Ar) along its entire length and undergoes rapid and profound degeneration when androgenic support is withdrawn. However, experiments involving orchidectomy with systemic testosterone replacement, and testicular efferent duct ligation, have indicated that structural and functional integrity of the initial segment cannot be maintained by circulating androgen alone, leaving the role of androgen in this epididymal zone unclear. We addressed this question in a mouse model with intact testicular output and selective Ar inactivation in the proximal epididymis by creating double-transgenic males carrying a conditional Ar(loxP) allele and expressing Cre recombinase under the promoter of Rnase10, a gene specifically expressed in proximal epididymis. At 20-25 d of life, on the onset of Rnase10 expression, Ar became selectively inactivated in the principal cells of proximal epididymis, resulting in epithelial hypoplasia and hypotrophy. Upon the subsequent onset of spermiation, epididymal obstruction ensued, with the consequent development of spermatic granulomata, back pressure-induced atrophy of the seminiferous epithelium, orchitis, and fibrosis of the testicular parenchyma. Consistent with these findings, the mice were infertile. When the effect of Ar knockout on gene expression in the proximal epididymis was compared with that of efferent duct ligation and orchidectomy, we identified genes specifically regulated by androgen, testicular efferent fluid, and both. Our findings demonstrate that the development and function of the epididymal initial segment is critically dependent on direct androgen regulation. The phenotype of the produced knockout mouse provides a novel model for obstructive azoospermia.

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A, Expression of Rnase10, Etv4, Srd5a1, Ros1, Araf, and Bcl2l15 in the IS of intact WT, ProxE-ARKO (ARKO), and EDL and OE wild-type mice. Each bar is the mean ± sem of measurements from three animals. Statistical significances: ***, P < 0.001; *, P < 0.05. NS, Not significant. The micrographs at the bottom (B) show representative views of proximal epididymis of the four experimental groups. Bar, 30 μm.
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Figure 5: A, Expression of Rnase10, Etv4, Srd5a1, Ros1, Araf, and Bcl2l15 in the IS of intact WT, ProxE-ARKO (ARKO), and EDL and OE wild-type mice. Each bar is the mean ± sem of measurements from three animals. Statistical significances: ***, P < 0.001; *, P < 0.05. NS, Not significant. The micrographs at the bottom (B) show representative views of proximal epididymis of the four experimental groups. Bar, 30 μm.

Mentions: To address the molecular consequences of Ar ablation, the transcription of six genes with predominant expression in the principal cells of the IS was measured by quantitative RT-PCR. Specific mRNA levels in the ProxE-ARKO mice were compared, besides WT controls, with those in WT mice subjected to EDL or OE (Fig. 5). EDL and OE were carried out at 20–25 dpp (shortly after the onset of Rnase10 expression and differentiation of IS), whereas gene expression was measured at 35–40 dpp, around the time of onset of spermiation and before the development of ductal occlusion in the ProxE-ARKO males. In this way we were able to discriminate the dependence of expression of the genes on endocrine androgen effect (reduced in PoxE-ARKO), lumicrine factors (reduced in EDL), or either one of the former (reduced in OE).


Targeted inactivation of the androgen receptor gene in murine proximal epididymis causes epithelial hypotrophy and obstructive azoospermia.

Krutskikh A, De Gendt K, Sharp V, Verhoeven G, Poutanen M, Huhtaniemi I - Endocrinology (2010)

A, Expression of Rnase10, Etv4, Srd5a1, Ros1, Araf, and Bcl2l15 in the IS of intact WT, ProxE-ARKO (ARKO), and EDL and OE wild-type mice. Each bar is the mean ± sem of measurements from three animals. Statistical significances: ***, P < 0.001; *, P < 0.05. NS, Not significant. The micrographs at the bottom (B) show representative views of proximal epididymis of the four experimental groups. Bar, 30 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3101806&req=5

Figure 5: A, Expression of Rnase10, Etv4, Srd5a1, Ros1, Araf, and Bcl2l15 in the IS of intact WT, ProxE-ARKO (ARKO), and EDL and OE wild-type mice. Each bar is the mean ± sem of measurements from three animals. Statistical significances: ***, P < 0.001; *, P < 0.05. NS, Not significant. The micrographs at the bottom (B) show representative views of proximal epididymis of the four experimental groups. Bar, 30 μm.
Mentions: To address the molecular consequences of Ar ablation, the transcription of six genes with predominant expression in the principal cells of the IS was measured by quantitative RT-PCR. Specific mRNA levels in the ProxE-ARKO mice were compared, besides WT controls, with those in WT mice subjected to EDL or OE (Fig. 5). EDL and OE were carried out at 20–25 dpp (shortly after the onset of Rnase10 expression and differentiation of IS), whereas gene expression was measured at 35–40 dpp, around the time of onset of spermiation and before the development of ductal occlusion in the ProxE-ARKO males. In this way we were able to discriminate the dependence of expression of the genes on endocrine androgen effect (reduced in PoxE-ARKO), lumicrine factors (reduced in EDL), or either one of the former (reduced in OE).

Bottom Line: The epithelial lining of the epididymal duct expresses the androgen receptor (Ar) along its entire length and undergoes rapid and profound degeneration when androgenic support is withdrawn.At 20-25 d of life, on the onset of Rnase10 expression, Ar became selectively inactivated in the principal cells of proximal epididymis, resulting in epithelial hypoplasia and hypotrophy.Our findings demonstrate that the development and function of the epididymal initial segment is critically dependent on direct androgen regulation.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery and Cancer, Imperial College London, London W12 0NN, United Kingdom.

ABSTRACT
The epithelial lining of the epididymal duct expresses the androgen receptor (Ar) along its entire length and undergoes rapid and profound degeneration when androgenic support is withdrawn. However, experiments involving orchidectomy with systemic testosterone replacement, and testicular efferent duct ligation, have indicated that structural and functional integrity of the initial segment cannot be maintained by circulating androgen alone, leaving the role of androgen in this epididymal zone unclear. We addressed this question in a mouse model with intact testicular output and selective Ar inactivation in the proximal epididymis by creating double-transgenic males carrying a conditional Ar(loxP) allele and expressing Cre recombinase under the promoter of Rnase10, a gene specifically expressed in proximal epididymis. At 20-25 d of life, on the onset of Rnase10 expression, Ar became selectively inactivated in the principal cells of proximal epididymis, resulting in epithelial hypoplasia and hypotrophy. Upon the subsequent onset of spermiation, epididymal obstruction ensued, with the consequent development of spermatic granulomata, back pressure-induced atrophy of the seminiferous epithelium, orchitis, and fibrosis of the testicular parenchyma. Consistent with these findings, the mice were infertile. When the effect of Ar knockout on gene expression in the proximal epididymis was compared with that of efferent duct ligation and orchidectomy, we identified genes specifically regulated by androgen, testicular efferent fluid, and both. Our findings demonstrate that the development and function of the epididymal initial segment is critically dependent on direct androgen regulation. The phenotype of the produced knockout mouse provides a novel model for obstructive azoospermia.

Show MeSH
Related in: MedlinePlus