Capillaries in the lamina propria of human seminiferous tubules are partly fenestrated

Abstract

The three capillary parts of the microvasculature of the human testis, namely the arterial side inter-Leydig cell capillaries, the intramural capillaries, and the venous side inter-Leydig cell capillaries, were studied in detail by dual detection of alkaline phosphatase enzyme activity and endothelial marker immunoreactivity, and by means of light- and transmission-electron microscopy. Alkaline phosphatase enzyme activity was seen in intertubular arterioles, capillaries, and venules, and in intramural capillaries of the human testis, whereas the lamina propria of human seminiferous tubules showed no staining. Alkaline phosphatase enzyme activity and the endothelial marker detected by the Qbend 30 antibody co-existed within the endothelial cells of the microvasculature. Electron-microscopically, the endothelial cells of the arterial and venous side inter-Leydig cell capillaries, and of the intertubular capillaries free of Leydig cells were of the continuous type without fenestrations (A-1-alpha type). The intramural capillaries consisted of non-fenestrated (A-1-alpha type) and fenestrated sections (A-2-alpha type). The fenestrations faced the germinal epithelium. Capillaries with a continuous non-fenestrated endothelium contained a large number of transcytotic vesicles and channels. These were numerous in the endothelial cells of the inter-Leydig cell capillaries and the non-fenestrated part of the intramural capillaries. Capillaries partly ran in between the layers of the lamina propria and therefore represented the capillarization of the seminiferous tubules. Thus the multilayered lamina propria probably requires its own capillary supply to allow rapid exchange between the microvasculature and the epithelium of the human seminiferous tubules.

The endocrine-gland-derived VEGF homologue Bv8 promotes angiogenesis in the testis: Localization of Bv8 receptors to endothelial cells

“…In the mouse, although Bv8 and VEGF are expressed in the testis, the endothelial cells do not exhibit this phenotype (36,37), indicating that in vivo there is a greater level of complexity to regulate or determine this ultrastructural feature. In the human testis, endothelial cells within the lamina propria of the seminiferous tubule exhibit fenestrae (38). Therefore, it is tempting to speculate that EG-VEGF and VEGF expressed in the Leydig cells, along with Bv8 expressed in the tubule potentially contribute to the development of this phenotype.…”

CEA-related cell adhesion molecule-1 is involved in angiogenic switch in prostate cancer

“…These tissue pieces were embedded in Epon 812, cut in semithin sections (1 mm thick), and stained by Toluidin blue/Pyronin (Ergun et al, 1996;Kilic and Ergun 2001). Light microscopic (Leica, DM/LB) evaluation was performed to identify prostate tissue areas of normal, PIN and prostate cancer of different stages.…”

“…Afterwards, for electron microscopic studies, fine sections (80 nm) were cut from the light microscopically marked areas of epon-embedded tissue blocks and contrasted by uranyl acetate (Merk, Germany) and lead citrate (Merk, Germany). The electron microscope was a Philips EM 300 (Ergun et al, 1996;Kilic and Ergun, 2001). …”

“…In vitro endothelial tube formation assay This assay was carried out using three-dimensional type I collagen gel (Vitrogen 100, Collagen Corp., CA, USA) which were prepared in 48-well cluster tissue culture dishes (Costar, Cambridge, MA, USA) as previously described (Ergun et al, 1996;Kilic and Ergun, 2001). After polymerization of the gel at 371C, HDMECs were seeded onto the solidified gels at a concentration of 2 Â 10 4 /well in 300 ml of MV medium (Promocell, Heidelberg, Germany) containing 5% FCS.…”

Anatomical Targeting Improves Delivery of Unconjugated Nanoparticles to the Testicle

“…Reported differences include a maintained blood-testis-barrier with cryptorchidism in rats as compared to a loss of the barrier in humans, fenestration of human testicular endothelial cells as compared to unfenestrated rat endothelial cells, and differential expression of occludin in the tight junctions between Sertoli cells in rats and humans. [20][21][22][23][24][25] While most of these differences lead one to believe penetration of NPs past the blood-testis-barrier would be greater in a human patient, if the mechanism relies upon occludin, the opposite may be true. The mechanism by which NPs cross the blood-testis-barrier has not been elucidated in this study and could be of further interest.…”