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Overexpression of VEGF in testis and epididymis causes infertility in transgenic mice: evidence for nonendothelial targets for VEGF.

Korpelainen EI, Karkkainen MJ, Tenhunen A, Lakso M, Rauvala H, Vierula M, Parvinen M, Alitalo K - J. Cell Biol. (1998)

Bottom Line: Vascular endothelial growth factor (VEGF) is a key regulator of endothelial growth and permeability.The ductus epididymidis was dilated, containing areas of epithelial hyperplasia.The number of subepithelial capillaries in the epididymis was also increased and these vessels were highly permeable as judged by the detection of extravasated fibrinogen products.

View Article: PubMed Central - PubMed

Affiliation: Molecular/Cancer Biology Laboratory, Haartman Institute, Helsinki, Finland.

ABSTRACT
Vascular endothelial growth factor (VEGF) is a key regulator of endothelial growth and permeability. However, VEGF may also target nonendothelial cells, as VEGF receptors and responsiveness have been detected for example in monocytes, and high concentrations of VEGF have been reported in human semen. In this work we present evidence that overexpression of VEGF in the testis and epididymis of transgenic mice under the mouse mammary tumor virus (MMTV) LTR promoter causes infertility. The testes of the transgenic mice exhibited spermatogenic arrest and increased capillary density. The ductus epididymidis was dilated, containing areas of epithelial hyperplasia. The number of subepithelial capillaries in the epididymis was also increased and these vessels were highly permeable as judged by the detection of extravasated fibrinogen products. Intriguingly, the expression of VEGF receptor-1 (VEGFR-1) was detected in certain spermatogenic cells in addition to vascular endothelium, and both VEGFR-1 and VEGFR-2 were also found in the Leydig cells of the testis. The infertility of the MMTV-VEGF male mice could thus result from VEGF acting on both endothelial and nonendothelial cells of the male genital tract. Taken together, these findings suggest that the VEGF transgene has nonendothelial target cells in the testis and that VEGF may regulate male fertility.

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Histological comparison of epididymides of 6-mo-old MMTV-VEGF transgenic and WT control mice (A–H), and localization  of expression of the VEGF transgene and VEGFRs by in situ hybridization (I–N). The ductus epididymidis of TG mice is dilated and  devoid of spermatozoa in the caput region (A) and exhibits epithelial hyperplasia in the cauda epididymidis (C). Caput and cauda epididymidis of a WT control mouse are shown in B and D, respectively. Higher magnification of the hyperplastic epithelium in the cauda  epididymidis of the MMTV-VEGF mice (E) reveals the presence of interspersed capillaries (arrows). Immunohistochemical staining of  these capillaries for vWF is shown in F. The fibrinogen staining in the same area (G) indicates that the capillary permeability is increased in the TG mice when compared with the WT mice (H). Asterisks, lumen of the ductus epididymidis. The VEGF transgene is expressed in the ductal epithelium (arrowhead) as judged by in situ hybridization (I, antisense and J, sense hVEGF probe). In contrast, the  VEGFR-2 antisense probe localizes to the outer rim of the duct (arrowhead) and inside the hyperplastic nodules in cauda epididymidis  of MMTV-VEGF mice (K), whereas no hybridization signal is seen in the WT control mice (L). VEGFR-1 is expressed around the ductus epididymidis and inside the hyperplastic nodules (arrowhead) in TG mice (M) and it is also found in interstitial blood vessels (arrow). In WT mice (N) the mVEGFR-1 antisense probe recognizes only the interstitial blood vessels. Bars: (A–D) 500 μm; (E, F, I, J, and  K–N), 50 μm; (G and H), 10 μm.
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Figure 2: Histological comparison of epididymides of 6-mo-old MMTV-VEGF transgenic and WT control mice (A–H), and localization of expression of the VEGF transgene and VEGFRs by in situ hybridization (I–N). The ductus epididymidis of TG mice is dilated and devoid of spermatozoa in the caput region (A) and exhibits epithelial hyperplasia in the cauda epididymidis (C). Caput and cauda epididymidis of a WT control mouse are shown in B and D, respectively. Higher magnification of the hyperplastic epithelium in the cauda epididymidis of the MMTV-VEGF mice (E) reveals the presence of interspersed capillaries (arrows). Immunohistochemical staining of these capillaries for vWF is shown in F. The fibrinogen staining in the same area (G) indicates that the capillary permeability is increased in the TG mice when compared with the WT mice (H). Asterisks, lumen of the ductus epididymidis. The VEGF transgene is expressed in the ductal epithelium (arrowhead) as judged by in situ hybridization (I, antisense and J, sense hVEGF probe). In contrast, the VEGFR-2 antisense probe localizes to the outer rim of the duct (arrowhead) and inside the hyperplastic nodules in cauda epididymidis of MMTV-VEGF mice (K), whereas no hybridization signal is seen in the WT control mice (L). VEGFR-1 is expressed around the ductus epididymidis and inside the hyperplastic nodules (arrowhead) in TG mice (M) and it is also found in interstitial blood vessels (arrow). In WT mice (N) the mVEGFR-1 antisense probe recognizes only the interstitial blood vessels. Bars: (A–D) 500 μm; (E, F, I, J, and K–N), 50 μm; (G and H), 10 μm.

Mentions: Comparison of the 6-mo-old MMTV-VEGF males with their wild-type (WT) littermates indicated that their epididymides were enlarged and swollen, whereas no apparent differences in testes, prostate, seminal vesicle, or other internal organs were observed. Histological examination (Fig. 2, A–E) confirmed that the ductus epididymidis was dilated, especially in caput and corpus epididymidis. The epithelium of the caput epididymidis was reduced in height, reminiscent of that found normally in the cauda region. The connective tissue septa between the segments contained enlarged blood vessels. All transgenic animals exhibited epithelial hyperproliferation dividing the duct into multiple narrow sublumens in proximal cauda epididymidis, and in some animals hyperplasia was observed also in the caput region. These hyperplastic areas were interspersed and surrounded by an increased number of subepithelial capillaries as evidenced by the presence of red cells and the vWF staining of the endothelial cells (Fig. 2, E and F). Staining using antibodies to fibrinogen, which has been used to detect increased capillary permeability resulting in fibrin deposition in tissues (24), indicated leakage of this plasma protein in between the epithelial cells and on the luminal side of the ductal epithelium (Fig. 2, G and H). Spermatozoa could be seen only in some ductal sections preceding the hyperplastic zones.


Overexpression of VEGF in testis and epididymis causes infertility in transgenic mice: evidence for nonendothelial targets for VEGF.

Korpelainen EI, Karkkainen MJ, Tenhunen A, Lakso M, Rauvala H, Vierula M, Parvinen M, Alitalo K - J. Cell Biol. (1998)

Histological comparison of epididymides of 6-mo-old MMTV-VEGF transgenic and WT control mice (A–H), and localization  of expression of the VEGF transgene and VEGFRs by in situ hybridization (I–N). The ductus epididymidis of TG mice is dilated and  devoid of spermatozoa in the caput region (A) and exhibits epithelial hyperplasia in the cauda epididymidis (C). Caput and cauda epididymidis of a WT control mouse are shown in B and D, respectively. Higher magnification of the hyperplastic epithelium in the cauda  epididymidis of the MMTV-VEGF mice (E) reveals the presence of interspersed capillaries (arrows). Immunohistochemical staining of  these capillaries for vWF is shown in F. The fibrinogen staining in the same area (G) indicates that the capillary permeability is increased in the TG mice when compared with the WT mice (H). Asterisks, lumen of the ductus epididymidis. The VEGF transgene is expressed in the ductal epithelium (arrowhead) as judged by in situ hybridization (I, antisense and J, sense hVEGF probe). In contrast, the  VEGFR-2 antisense probe localizes to the outer rim of the duct (arrowhead) and inside the hyperplastic nodules in cauda epididymidis  of MMTV-VEGF mice (K), whereas no hybridization signal is seen in the WT control mice (L). VEGFR-1 is expressed around the ductus epididymidis and inside the hyperplastic nodules (arrowhead) in TG mice (M) and it is also found in interstitial blood vessels (arrow). In WT mice (N) the mVEGFR-1 antisense probe recognizes only the interstitial blood vessels. Bars: (A–D) 500 μm; (E, F, I, J, and  K–N), 50 μm; (G and H), 10 μm.
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Figure 2: Histological comparison of epididymides of 6-mo-old MMTV-VEGF transgenic and WT control mice (A–H), and localization of expression of the VEGF transgene and VEGFRs by in situ hybridization (I–N). The ductus epididymidis of TG mice is dilated and devoid of spermatozoa in the caput region (A) and exhibits epithelial hyperplasia in the cauda epididymidis (C). Caput and cauda epididymidis of a WT control mouse are shown in B and D, respectively. Higher magnification of the hyperplastic epithelium in the cauda epididymidis of the MMTV-VEGF mice (E) reveals the presence of interspersed capillaries (arrows). Immunohistochemical staining of these capillaries for vWF is shown in F. The fibrinogen staining in the same area (G) indicates that the capillary permeability is increased in the TG mice when compared with the WT mice (H). Asterisks, lumen of the ductus epididymidis. The VEGF transgene is expressed in the ductal epithelium (arrowhead) as judged by in situ hybridization (I, antisense and J, sense hVEGF probe). In contrast, the VEGFR-2 antisense probe localizes to the outer rim of the duct (arrowhead) and inside the hyperplastic nodules in cauda epididymidis of MMTV-VEGF mice (K), whereas no hybridization signal is seen in the WT control mice (L). VEGFR-1 is expressed around the ductus epididymidis and inside the hyperplastic nodules (arrowhead) in TG mice (M) and it is also found in interstitial blood vessels (arrow). In WT mice (N) the mVEGFR-1 antisense probe recognizes only the interstitial blood vessels. Bars: (A–D) 500 μm; (E, F, I, J, and K–N), 50 μm; (G and H), 10 μm.
Mentions: Comparison of the 6-mo-old MMTV-VEGF males with their wild-type (WT) littermates indicated that their epididymides were enlarged and swollen, whereas no apparent differences in testes, prostate, seminal vesicle, or other internal organs were observed. Histological examination (Fig. 2, A–E) confirmed that the ductus epididymidis was dilated, especially in caput and corpus epididymidis. The epithelium of the caput epididymidis was reduced in height, reminiscent of that found normally in the cauda region. The connective tissue septa between the segments contained enlarged blood vessels. All transgenic animals exhibited epithelial hyperproliferation dividing the duct into multiple narrow sublumens in proximal cauda epididymidis, and in some animals hyperplasia was observed also in the caput region. These hyperplastic areas were interspersed and surrounded by an increased number of subepithelial capillaries as evidenced by the presence of red cells and the vWF staining of the endothelial cells (Fig. 2, E and F). Staining using antibodies to fibrinogen, which has been used to detect increased capillary permeability resulting in fibrin deposition in tissues (24), indicated leakage of this plasma protein in between the epithelial cells and on the luminal side of the ductal epithelium (Fig. 2, G and H). Spermatozoa could be seen only in some ductal sections preceding the hyperplastic zones.

Bottom Line: Vascular endothelial growth factor (VEGF) is a key regulator of endothelial growth and permeability.The ductus epididymidis was dilated, containing areas of epithelial hyperplasia.The number of subepithelial capillaries in the epididymis was also increased and these vessels were highly permeable as judged by the detection of extravasated fibrinogen products.

View Article: PubMed Central - PubMed

Affiliation: Molecular/Cancer Biology Laboratory, Haartman Institute, Helsinki, Finland.

ABSTRACT
Vascular endothelial growth factor (VEGF) is a key regulator of endothelial growth and permeability. However, VEGF may also target nonendothelial cells, as VEGF receptors and responsiveness have been detected for example in monocytes, and high concentrations of VEGF have been reported in human semen. In this work we present evidence that overexpression of VEGF in the testis and epididymis of transgenic mice under the mouse mammary tumor virus (MMTV) LTR promoter causes infertility. The testes of the transgenic mice exhibited spermatogenic arrest and increased capillary density. The ductus epididymidis was dilated, containing areas of epithelial hyperplasia. The number of subepithelial capillaries in the epididymis was also increased and these vessels were highly permeable as judged by the detection of extravasated fibrinogen products. Intriguingly, the expression of VEGF receptor-1 (VEGFR-1) was detected in certain spermatogenic cells in addition to vascular endothelium, and both VEGFR-1 and VEGFR-2 were also found in the Leydig cells of the testis. The infertility of the MMTV-VEGF male mice could thus result from VEGF acting on both endothelial and nonendothelial cells of the male genital tract. Taken together, these findings suggest that the VEGF transgene has nonendothelial target cells in the testis and that VEGF may regulate male fertility.

Show MeSH
Related in: MedlinePlus