A visualization system for erectile vascular dynamics

Abstract

Erection is an essential process which requires the male penis for copulation. This copulatory process depends on the vascular dynamic regulation of the penis. The corpus cavernosum (CC) in the upper (dorsal) part of the penis plays a major role in regulating blood flow inside the penis. When the CC is filled with blood, the sinusoids, including micro-vessels, dilate during erection. The CC is an androgen-dependent organ, and various genital abnormalities including erectile dysfunction (ED) are widely known. Previous studies have shown that androgen deprivation by castration results in significantly decreased smooth muscles of the CC. Experimental works in erectile biology have previously measured intracavernosal penile pressure and mechanical tension. Such reports analyze limited features without assessing the dynamic aspects of the erectile process. In the current study, we established a novel explant system enabling direct visual imaging of the sinusoidal lumen to evaluate the dynamic movement of the cavernous space. To analyze the alternation of sinusoidal spaces, micro-dissected CC explants by patent blue dye injection were incubated and examined for their structural alternations during relaxation/contraction. The dynamic process of relaxation/contraction was analyzed with various external factors administered to the CC. The system enabled the imaging of relaxation/contraction of the lumens of the sinusoids and the collagen-containing tissues. Histological analysis on the explant system also showed the relaxation/contraction. Thus, the system mimics the regulatory process of dynamic relaxation/contraction in the erectile response. The current system also enabled evaluating the erectile pathophysiology. In the current study, the lumen of sinusoids relaxed/contracted in castrated mice similarly with normal mice. These results suggested that the dynamic erectile relaxation/contraction process was similarly retained in castrated mice. However, the system also revealed decreased duration time of erection in castrated mice. The current study is expected to promote further understanding of the pathophysiology of ED, which will be useful for new treatments in the future. Hence, the current system provides unique information to investigate the novel regulations of erectile function, which can provide tools for analyzing the pathology of ED.

A review of experimental techniques for erectile function researches and development of medical technology using animal erectile dysfunction models in sexual and reproductive medicine

“…They evaluated the vascular function of the mice using time‐lapse visualization analysis and did not use a color Doppler system. 14 Isometric tension measurements are commonly used to assess the vascular endothelial function. Isometric tension measurement reproduces a NO‐guanosine 3′,5′‐cyclic monophosphate (cyclic GMP) reaction within the Magnus apparatus.…”

“…Fujimoto et al constructed a new hemodynamic evaluation system. They evaluated the vascular function of the mice using time‐lapse visualization analysis and did not use a color Doppler system 14 . Isometric tension measurements are commonly used to assess the vascular endothelial function.…”

Emerging structural and pathological analyses on the erectile organ, corpus cavernous containing sinusoids

“…Tissue explant systems have been analyzed in vitro for reproductive functional researches. 15,23 Recently, development of the explant culture system visualizing the dynamic processes of sinusoidal expansion, contraction/relaxation, of the mouse CC was performed 15,16,106 (Figure 4). Such explant system can visualize contraction/relaxation behavior and the effects of external factors for erectile functions in vitro.…”

“…In the bilateral region, well‐developed sinusoidal structures are observed which show various sizes. In addition to sinusoids, mouse CC contains the prominently developed collagen‐rich trabecular structure concentrated in the middle region (island like central area) which extends radially toward the outer region 5,16,23,24 . Thus, central CC region may offer structural and mechanical supports for the radial expansion by erection.…”

“…Such explant system can visualize contraction/relaxation behavior and the effects of external factors for erectile functions in vitro. Administration of prostaglandin E has been often utilized to treat ED patients which show resistance for PDE5 inhibitor treatment and its effectiveness has been shown by such explant culture system 16 . One of the advantages of such system is its capability to repeat contraction/relaxation processes in vitro.…”