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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androgen receptor (Ar) along its entire length and undergoes rapid and profound degeneration when androgenic support is withdrawn.At 20-25 d of life, on the onset of Rnase10 expression, Ar became selectively inactivated in the principal cells of proximal epididymis, resulting in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androgen receptor (Ar) along its entire length and undergoes rapid and profound degeneration when androgenic support is withdrawn.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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Consequences of Ar ablation in the proximal epididymis. A, ProxE-ARKO epididymis on the right shows accumulation of inspissated spermatozoa in the hypoplastic proximal part (arrow) and a spermatic granuloma in the caudal region (arrowhead); a wild-type control epididymis is shown on the left. Bar, 2 mm. B, Testicular outflow obstruction results in dilatation of seminiferous tubules and increased testis size (asterisk) in the ProxE-ARKO male (right); wild-type control is shown on the left. Bar, 3 mm. C–H, Hematoxylin and eosin. C, Control testis. Bar, 100 μm. D and E, Progressive dilated atrophy of germinal epithelium; lumen of seminiferous tubules is indicated with asterisks. Bar, 100 μm. F, Orchitis and interstitial fibrosis (crosses) in ProxE-ARKO testis; asterisks indicate seminiferous tubules, some containing intraepithelial cysts. Bar, 200 μm. G, Degenerative changes in cauda epididymidis. Bar 150 μm. H, Focus of granulomatous inflammation in distal caput epididymidis; arrow indicates spermatozoa in the center of spermatic granuloma. Bar, 150 μm.
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Figure 4: Consequences of Ar ablation in the proximal epididymis. A, ProxE-ARKO epididymis on the right shows accumulation of inspissated spermatozoa in the hypoplastic proximal part (arrow) and a spermatic granuloma in the caudal region (arrowhead); a wild-type control epididymis is shown on the left. Bar, 2 mm. B, Testicular outflow obstruction results in dilatation of seminiferous tubules and increased testis size (asterisk) in the ProxE-ARKO male (right); wild-type control is shown on the left. Bar, 3 mm. C–H, Hematoxylin and eosin. C, Control testis. Bar, 100 μm. D and E, Progressive dilated atrophy of germinal epithelium; lumen of seminiferous tubules is indicated with asterisks. Bar, 100 μm. F, Orchitis and interstitial fibrosis (crosses) in ProxE-ARKO testis; asterisks indicate seminiferous tubules, some containing intraepithelial cysts. Bar, 200 μm. G, Degenerative changes in cauda epididymidis. Bar 150 μm. H, Focus of granulomatous inflammation in distal caput epididymidis; arrow indicates spermatozoa in the center of spermatic granuloma. Bar, 150 μm.

Mentions: As a consequence of the interruption of flow of testicular fluid, severe distension developed in the efferent ducts, rete testis and seminiferous tubules. Testes examined at the age of 4 months were increased in size apparently secondary to fluid retention (Fig. 4B). The seminiferous tubules were at various stages of degeneration (Fig. 4, D and E), some with numerous mononuclear cells in the lumen. A significant proportion of the tubules had lost all cells of the germinal epithelium (Fig. 4E) and contained intraepithelial cysts (Fig. 4F), consistent with backpressure testicular atrophy; some males were found to have developed unilateral orchitis (Fig. 4F). Epididymal epithelium distal to the point of occlusion displayed signs of degeneration with the formation of intraepithelial cysts and accumulation of hyaline-like material in the lumen (Fig. 4G). Spermatic granulomata were frequently observed in obstructed epididymides (Fig. 4, A and H).


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)

Consequences of Ar ablation in the proximal epididymis. A, ProxE-ARKO epididymis on the right shows accumulation of inspissated spermatozoa in the hypoplastic proximal part (arrow) and a spermatic granuloma in the caudal region (arrowhead); a wild-type control epididymis is shown on the left. Bar, 2 mm. B, Testicular outflow obstruction results in dilatation of seminiferous tubules and increased testis size (asterisk) in the ProxE-ARKO male (right); wild-type control is shown on the left. Bar, 3 mm. C–H, Hematoxylin and eosin. C, Control testis. Bar, 100 μm. D and E, Progressive dilated atrophy of germinal epithelium; lumen of seminiferous tubules is indicated with asterisks. Bar, 100 μm. F, Orchitis and interstitial fibrosis (crosses) in ProxE-ARKO testis; asterisks indicate seminiferous tubules, some containing intraepithelial cysts. Bar, 200 μm. G, Degenerative changes in cauda epididymidis. Bar 150 μm. H, Focus of granulomatous inflammation in distal caput epididymidis; arrow indicates spermatozoa in the center of spermatic granuloma. Bar, 150 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Consequences of Ar ablation in the proximal epididymis. A, ProxE-ARKO epididymis on the right shows accumulation of inspissated spermatozoa in the hypoplastic proximal part (arrow) and a spermatic granuloma in the caudal region (arrowhead); a wild-type control epididymis is shown on the left. Bar, 2 mm. B, Testicular outflow obstruction results in dilatation of seminiferous tubules and increased testis size (asterisk) in the ProxE-ARKO male (right); wild-type control is shown on the left. Bar, 3 mm. C–H, Hematoxylin and eosin. C, Control testis. Bar, 100 μm. D and E, Progressive dilated atrophy of germinal epithelium; lumen of seminiferous tubules is indicated with asterisks. Bar, 100 μm. F, Orchitis and interstitial fibrosis (crosses) in ProxE-ARKO testis; asterisks indicate seminiferous tubules, some containing intraepithelial cysts. Bar, 200 μm. G, Degenerative changes in cauda epididymidis. Bar 150 μm. H, Focus of granulomatous inflammation in distal caput epididymidis; arrow indicates spermatozoa in the center of spermatic granuloma. Bar, 150 μm.
Mentions: As a consequence of the interruption of flow of testicular fluid, severe distension developed in the efferent ducts, rete testis and seminiferous tubules. Testes examined at the age of 4 months were increased in size apparently secondary to fluid retention (Fig. 4B). The seminiferous tubules were at various stages of degeneration (Fig. 4, D and E), some with numerous mononuclear cells in the lumen. A significant proportion of the tubules had lost all cells of the germinal epithelium (Fig. 4E) and contained intraepithelial cysts (Fig. 4F), consistent with backpressure testicular atrophy; some males were found to have developed unilateral orchitis (Fig. 4F). Epididymal epithelium distal to the point of occlusion displayed signs of degeneration with the formation of intraepithelial cysts and accumulation of hyaline-like material in the lumen (Fig. 4G). Spermatic granulomata were frequently observed in obstructed epididymides (Fig. 4, A and H).

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