Anti-lysyl oxidase combined with a vacuum device induces penile lengthening by remodeling the tunica albuginea

Abstract

This study aimed to explore whether and how anti-lysyl oxidase (anti-LOX) combined with a vacuum device (VD) could promote penile lengthening and to evaluate the effect on erectile function. This study was performed on four groups of adult rats: control, anti-LOX, VD (negative pressure value of -300 mmHg), and anti-LOX + VD. Penile length was measured by a modified VD method and verified on exposed length data. Intracavernous pressure (ICP) and maximum ICP/mean arterial pressure (MAP) ratio were recorded to assess erectile function. For corpus cavernosum, LOX activity and concentrations of pyridinoline, desmosine, hydroxyproline, and elastin were analyzed; transmission electron microscope and Hart's elastin staining were performed to monitor microstructural changes. Anti-LOX and VD significantly lengthened the penis by 10.8% (3.75 mm) and 8.2% (2.48 mm) compared with the control group, respectively, while anti-LOX + VD achieved the longest penile size (40.58 ± 0.40 mm) which was 17.4% longer than the control group (34.58 ± 0.54 mm). After 1-week washout, no penile retraction was observed. Meanwhile, exposed penile length data confirmed that the penis in the anti-LOX + VD group was also significantly longer. Anti-LOX inhibited LOX activity to reduce pyridinoline level, which led the penile tunica albuginea remodeling. However, it had no effect on hydroxyproline, desmosine, and elastin levels. Moreover, anti-LOX had no impact on erectile function, which was determined by ICP and ICP/MAP ratio. These results suggest that anti-LOX elongates the penis by reducing pyridinoline, which induces tunica albuginea remodeling. This lengthening effect was more obvious when combined with a VD. All procedures had no impact on erectile function.

Keywords: anti-lysyl oxidase; crosslinking; penile lengthening; tunica albuginea remodeling; vacuum device.

Figure 1

Anti-LOX combined with a VD induces penile lengthening (n = 6 per group). (a) Representative images of penile length. (b) Representative images of penile length after a 1-week washout period. For a and b, penile length was measured under unified vacuum device aspiration condition (measured at –200 mmHg for 5 min twice with a 2-min interval). (c) Exposed penile length; the length was measured from the junction of urethral bulb and corpus cavernosum (marked with yellow line), to tip of glans cartilage; the measurement errors of length data were corrected on recorded images. (d) Statistical analysis of penile length (P < 0.0001). (e) Statistical analysis of penile length after a 1-week washout period (P < 0.0001). (f) Statistical analysis for exposed penile length (P < 0.0001). Anti-LOX: intragastric administration of β-aminopropionitrile (BAPN) with a dose of 100 mg kg⁻¹ day⁻¹; VD: vacuum device aspiration with negative pressure of -300 mmHg. ^**P < 0.01, ^***P < 0.0001. LOX: lysyl oxidase.

Figure 2

LOX variation in corpus cavernosum in rats with 8, 12, 16, 24, and 48 weeks, respectively (n = 6 per group). (a) Representative image from Western blot. (b) Statistical analysis revealed that LOX expression was the highest at 8 weeks of age, which was significantly decreased with age (P < 0.0001). (c) LOX activity was the highest at 8 weeks of age; it was then significantly declined (P < 0.0001) and finally attained a relative stable level (P > 0.05). ^*P < 0.05, ^***P < 0.0001. LOX: lysyl oxidase; RFUs: relative fluorescent units.

Figure 3

Anti-LOX combined with a VD does not impact normal erectile function (n = 6 per group). (a) Representative images of ICP under cavernous nerve stimulation. (b) Representative images of arterial pressure under cavernous nerve stimulation. (c) Statistical analysis of ICP (P = 0.4512). (d) Statistical analysis of mean arterial pressure (MAP; P = 0.1017). (e) Statistical analysis of ICP/MAP ratio (P = 0.4297). Anti-LOX: intragastric administration of β-aminopropionitrile (BAPN) with a dose of 100 mg kg⁻¹ day⁻¹; VD: vacuum device aspiration with negative pressure of -300 mmHg. LOX: lysyl oxidase; ICP: intracavernous pressure.

Figure 4

Biomarker analysis for corpus cavernosum. (a) anti-LOX and anti-LOX + VD groups exhibited significantly lower lysyl oxidase (LOX) activity than control and VD groups, respectively (P = 0.0149). (b) No significant difference was found on HYP (P = 0.5440) level. (c) No significant difference was found on total elastin content (P = 0.2228). (d) Anti-LOX group showed significantly lower PYD concentration than the control group (P = 0.0449), while anti-LOX + VD revealed significant lower level than the control (P = 0.0015) and −300 mmHg (P = 0.0015) groups. (e) No significant difference was found on DES concentration (P = 0.8226). n = 6 per group. Anti-LOX: intragastric administration of β-aminopropionitrile (BAPN) with a dose of 100 mg kg⁻¹ day⁻¹. VD: vacuum device aspiration with negative pressure of -300 mmHg. ^*P < 0.05, ^***P < 0.0001. RFUs: relative fluorescent units; LOX: lysyl oxidase; HYP: hydroxyproline; PYD: pyridinoline; DES: desmosines.

Figure 5

Transmission electron microscopy in tunica albuginea of corpus cavernosum (n = 2 per group). (a) In longitudinal section, anti-LOX + VD group showed loosely arranged collagen fibers (scale bars = 1 μm). (b) In cross section, remodeled appearances of collagen bundlea were more obvious in anti-LOX, VD, and anti-LOX + VD groups, they also showed irregular arranged collagen bundles and less ground substance, compared with the control group (scale bars = 2 μm). Anti-LOX: intragastric administration of β-aminopropionitrile (BAPN) with a dose of 100 mg kg⁻¹ day⁻¹. VD: vacuum device aspiration with negative pressure of -300 mmHg. LOX: lysyl oxidase.

Figure 6

Hart's elastin staining in rat models (n = 6 per group). (a) Tunica albuginea showed blue-black to blue elastic fibers, which was abundant between Buck's fascia and tunica (at ×50 magnification, scale bars = 200 μm), representative elastic fibers on the upper left box (at ×400 magnification, scale bars = 50 μm); elastic fibers with regular shapes were tightly intertwined with collagen bundles along tunica albuginea. (b) Representative elastic fibers of corpus spongiosum at ×100 magnification (scale bars = 100 μm). Corpus spongiosum revealed substantially abundant elastic fibers with a tortuous appearance. (c) Elastic fibers of corpus spongiosum at 0 o'clock (at ×200 magnification, scale bars = 100 μm). (d) Cumulative area of elastic fibers in corpus spongiosum (0, 3, 6, and 9 o'clock at ×200 magnification), with insignificant difference found (P = 0.1865). Anti-LOX: intragastric administration of β-aminopropionitrile (BAPN) with a dose of 100 mg kg⁻¹ day⁻¹; VD: vacuum device aspiration with negative pressure of -300 mmHg. LOX: lysyl oxidase.