In most types of erectile dysfunction, particularly in advanced stages, typical pathological features observed are reduced parenchymal cells coupled with increased tissue fibrosis. However, the current treatment methods have shown limited success in reversing these pathologic changes. Recent research has revealed that changes in autophagy levels, along with alterations in apoptosis and fibrosis-related proteins, are linked to the progression of erectile dysfunction, suggesting a significant association. Autophagy, known to significantly affect cell fate and tissue fibrosis, is currently being explored as a potential treatment modality for erectile dysfunction. However, these present studies are still in their nascent stage, and there are limited experimental data available. This review analyzes erectile dysfunction from a pathological perspective. It provides an in-depth overview of how autophagy is involved in the apoptotic processes of smooth muscle and endothelial cells and its role in the fibrotic processes occurring in the cavernosum. This study aimed to develop a theoretical framework for the potential effectiveness of autophagy in preventing and treating erectile dysfunction, thus encouraging further investigation among researchers in this area.
Male ; Humans ; Autophagy/physiology* ; Apoptosis/physiology* ; Erectile Dysfunction/physiopathology* ; Fibrosis ; Penis/pathology* ; Animals ; Endothelial Cells/pathology* ; Myocytes, Smooth Muscle/pathology*

Stem cell treatment may enhance erectile dysfunction (ED) in individuals with cavernous nerve injury (CNI). Nevertheless, no investigations have directly ascertained the implications of varying amounts of human umbilical cord-derived mesenchymal stem cells (HUC-MSCs) on ED. We compare the efficacy of three various doses of HUC-MSCs as a therapeutic strategy for ED. Sprague-Dawley rats (total = 175) were randomly allocated into five groups. A total of 35 rats underwent sham surgery and 140 rats endured bilateral CNI and were treated with vehicles or doses of HUC-MSCs (1 × 10 6 cells, 5 × 10 6 cells, and 1 × 10 7 cells in 0.1 ml, respectively). Penile tissues were harvested for histological analysis on 1 day, 3 days, 7 days, 14 days, 28 days, 60 days, and 90 days postsurgery. It was found that varying dosages of HUC-MSCs enhanced the erectile function of rats with bilateral CNI and ED. Moreover, there was no significant disparity in the effectiveness of various dosages of HUC-MSCs. However, the expression of endothelial markers (rat endothelial cell antigen-1 [RECA-1] and endothelial nitric oxide synthase [eNOS]), smooth muscle markers (alpha smooth muscle actin [α-SMA] and desmin), and neural markers (neurofilament [RECA-1] and neurogenic nitric oxide synthase [nNOS]) increased significantly with prolonged treatment time. Masson's staining demonstrated an increased in the smooth muscle cell (SMC)/collagen ratio. Significant changes were detected in the microstructures of various types of cells. In vivo imaging system (IVIS) analysis showed that at the 1 st day, the HUC-MSCs implanted moved to the site of damage. Additionally, the oxidative stress levels were dramatically reduced in the penises of rats administered with HUC-MSCs.
Male ; Animals ; Erectile Dysfunction/metabolism* ; Rats, Sprague-Dawley ; Mesenchymal Stem Cell Transplantation/methods* ; Rats ; Penis/pathology* ; Humans ; Disease Models, Animal ; Umbilical Cord/cytology* ; Peripheral Nerve Injuries/complications* ; Mesenchymal Stem Cells ; Nitric Oxide Synthase Type III/metabolism* ; Actins/metabolism* ; Nitric Oxide Synthase Type I/metabolism*

Low-intensity pulsed ultrasound (LIPUS) is a non-invasive sonodynamic therapy that has been approved by the U.S. Food and Drug Administration for clinical use. Clinical trials have demonstrated that LIPUS ameliorates mild-to-moderate erectile dysfunction without adverse events. Histological analysis of the corpus cavernosum suggests that the therapeutic benefits of LIPUS may be attributed to alleviation of fibrosis, enhanced neovascularization, and promotion of innervation. Further investigations have revealed that LIPUS facilitates cavernous tissue repair through non-thermal mechanisms, including a cavitation effect, acoustic streaming, mass transfer enhancement, and direct mechanical stimulation. Mechanobiological transduction triggers molecular signaling cascades within endogenous cavernous cells, thereby stimulating cell proliferation, angiogenesis, extracellular matrix remodeling, and stem cell differentiation. Although LIPUS has the potential to induce cavernous rehabilitation in the treatment of erectile dysfunction, further investigations are necessary to elucidate the mechanisms via which LIPUS regulates each type of cavernous cell to determine the optimal parameters for this innovative therapy.
Male ; Humans ; Erectile Dysfunction/therapy* ; Ultrasonic Therapy/methods* ; Penis/pathology* ; Ultrasonic Waves

This study explored the usefulness of two-dimensional shear wave elastography (2D-SWE) in the early assessment of corpora cavernosa fibrosis (CCF). New Zealand male rabbits were randomly assigned to an experimental group or a control group. Recombinant human transforming growth factor beta 1 (TGF-β1) was injected into the dorsal penis tissue of rabbits in the experimental group. Conventional ultrasound and 2D-SWE examinations were performed before and 20 days after injection. Penile histological analysis was performed by hematoxylin-eosin staining, sirius red staining, and immunohistochemistry. Measurement of 2D-SWE examination results was performed using shear wave elastography quantitative measurement (SWQ). Histological analysis outcomes were the proportion of smooth muscle cells (SMCs), collagen fibers (CFs), collagen type I (Col I), and collagen type III (Col III), as well as the SMCs/CFs ratio, measured by sirius red staining. Other histological analysis outcomes were the positive area proportion (PAP) of TGF-β1 (PAP_T), fibronectin (PAP_F), and Col III (PAP_C), measured by immunohistochemistry. After recombinant human TGF-β1 injection, SWQ was higher in the experimental group than that in the control group (P < 0.001); however, there were no differences in conventional ultrasound results. There were significant differences in histological outcomes between the two groups (all P < 0.05). These results indicated that 2D-SWE was superior for identifying early histological changes in CCF.
Animals ; Elasticity Imaging Techniques/methods* ; Fibrosis ; Male ; Penis/pathology* ; Rabbits ; Transforming Growth Factor beta1/metabolism*

Silent information regulator 2-related enzyme 1 (SIRT1) is an aging-related protein activated with aging. Herein, we evaluated the role of SIRT1 in aging-related erectile dysfunction. The expression of SIRT1 was modulated in aged Sprague-Dawley rats following intragastric administration of resveratrol (Res; 5 mg kg^-1), niacinamide (NAM; 500 mg kg^-1) or Res (5 mg kg^-1) + tadalafil (Tad; phosphodiesterase-5 [PDE5] inhibitor; 5 mg kg^-1) for 8 weeks. Then, we determined erectile function by the ratio of intracavernosal pressure (ICP)/mean systemic arterial pressure (MAP). Cavernosal tissues were extracted to evaluate histological changes, cell apoptosis, nitric oxide (NO)/cyclic guanosine monophosphate (cGMP), the superoxide dismutase (SOD)/3,4-methylenedioxyamphetamine (MDA) level, and the expression of SIRT1, p53, and forkhead box O3 (FOXO3a) using immunohistochemistry, terminal deoxynucleotidyl transferase (TdT)-mediated 2'-deoxyuridine 5'-triphosphate (dUTP) nick-end labeling (TUNEL), enzyme-linked immunosorbent assays, and western blot analysis. Compared with the control, Res treatment significantly improved erectile function, reflected by an increased content of smooth muscle and endothelium, NO/cGMP and SOD activity, and reduced cell apoptosis and MDA levels. The effect of Res was improved by adding Tad. In addition, the protein expression of SIRT1 was increased in the Res group, accompanied by decreased p53 and FOXO3a levels. In addition, inhibition of SIRT1 by NAM treatment resulted in adverse results compared with Res treatment. SIRT1 activation ameliorated aging-related erectile dysfunction, supporting the potential of SIRT1 as a target for erectile dysfunction treatment.
Animals ; Male ; Rats ; Cyclic GMP/metabolism* ; Erectile Dysfunction/metabolism* ; Nitric Oxide/metabolism* ; Penile Erection ; Penis/pathology* ; Phosphodiesterase 5 Inhibitors/pharmacology* ; Rats, Sprague-Dawley ; Sirtuin 1/metabolism* ; Superoxide Dismutase/metabolism* ; Tumor Suppressor Protein p53/metabolism*

We wanted to determine whether shear wave elastography (SWE) could be used to evaluate the aging degree of the corpus cavernosum (CC) and to identify the histological basis of changes in SWE measurements during the aging process. We performed a cross-sectional study enrolling healthy participants of different ages. We measured the Young's modulus (YM) of the penile CCs by SWE and assessed erectile function using the International Index of Erectile Function-5 (IIEF-5). Histological investigation was performed in surgically resected penile specimens from a separate group of patients to examine the smooth muscle and collagen content of the CCs. Furthermore, we measured the YM, erectile function, smooth muscle, and collagen content of the CCs in different age groups of rats. Finally, we enrolled 210 male volunteers in this study. The YM of the CC (CCYM) was positively correlated with age (r = 0.949, P < 0.01) and negatively correlated with erectile function (r = -0.843, P < 0.01). Histological examinations showed that CCs had increased collagen content but decreased smooth muscle content with increased age. The same positive correlation between CCYM and age was also observed in the animal study. In addition, the animal study showed that older rats, with increased CCYM and decreased erectile function, had lower smooth muscle content and higher collagen content. SWE can noninvasively and quantitatively evaluate the aging degree of the CC. Increased collagen content and decreased smooth muscle content might be the histological basis for the effect of aging on the CC and the increase in its YM.
Humans ; Male ; Rats ; Animals ; Erectile Dysfunction ; Elasticity Imaging Techniques ; Cross-Sectional Studies ; Penis/pathology* ; Penile Erection/physiology* ; Aging ; Collagen

The aim of this study was to investigate the mechanism by which a diet inducing high hyperhomocysteinemia (HHcy) leads to the deterioration of erectile function in rats and whether this is inhibited by expression of the human tissue kallikrein-1 (hKLK1) gene. We established a rat model of HHcy by feeding methionine (Met)-rich diets to male Sprague-Dawley (SD) rats. Male wild-type SD rats (WTRs) and transgenic rats harboring the hKLK1 gene (TGRs) were fed a normal diet until 10 weeks of age. Then, 30 WTRs were randomly divided into three groups as follows: the control (n = 10) group, the low-dose (4% Met, n = 10) group, and the high-dose (7% Met, n = 10) group. Another 10 age-matched TGRs were fed the high-dose diet and designated as the TGR+7% Met group. After 30 days, in all four groups, erectile function was measured and penile tissues were harvested to determine oxidative stress, endothelial cell content, and penis fibrosis. Compared with the 7% Met group, the TGR+7% Met group showed diminished HHcy-induced erectile dysfunction (ED), indicating the improvement caused by hKLK1. Regarding corpus cavernosum endothelial cells, hKLK1 preserved endothelial cell-cell junctions and endothelial cell content, and activated protein kinase B/endothelial nitric oxide synthase (Akt/eNOS) signaling. Fibrosis assessment indicated that hKLK1 preserved normal penis structure by inhibiting apoptosis in the corpus cavernosum smooth muscle cells. Taken together, these findings showed that oxidative stress, impaired corpus cavernosum endothelial cells, and severe penis fibrosis were involved in the induction of ED by HHcy in rats, whereas hKLK1 preserved erectile function by inhibiting these pathophysiological changes.
Animals ; Apoptosis ; Diet ; Endothelial Cells ; Erectile Dysfunction/prevention & control* ; Fibrosis ; Humans ; Hyperhomocysteinemia/complications* ; Male ; Methionine ; Oxidative Stress ; Penis/pathology* ; Rats ; Rats, Sprague-Dawley ; Rats, Transgenic ; Signal Transduction/genetics* ; Tissue Kallikreins/genetics*

We aimed to determine whether combination of LIM-kinase 2 inhibitor (LIMK2i) and phosphodiesterase type-5 inhibitor (PDE5i) could restore erectile function through suppressing cavernous fibrosis and improving cavernous apoptosis in a rat model of cavernous nerve crush injury (CNCI). Seventy 12-week-old Sprague-Dawley rats were equally distributed into five groups as follows: (1) sham surgery (Group S), (2) CNCI (Group I), (3) CNCI treated with daily intraperitoneal administration of 10.0 mg kg^-1 LIMK2i (Group I + L), (4) daily oral administration of 20.0 mg kg^-1 udenafil, PDE5i (Group I + U), and (5) combined administration of 10.0 mg kg^-1 LIMK2i and 20.0 mg kg^-1 udenafil (Group I + L + U). Rats in Groups I + L, I + U, and I + L + U were treated with respective regimens for 2 weeks after CNCI. At 2 weeks after surgery, erectile response was assessed using electrostimulation. Penile tissues were processed for histological studies and western blot. Group I showed lower intracavernous pressure (ICP)/mean arterial pressure (MAP), lower area under the curve (AUC)/MAP, decreased immunohistochemical staining for alpha-smooth muscle (SM) actin, higher apoptotic index, lower SM/collagen ratio, increased phospho-LIMK2-positive fibroblasts, decreased protein kinase B/endothelial nitric oxide synthase (Akt/eNOS) phosphorylation, increased LIMK2/cofilin phosphorylation, and increased protein expression of fibronectin, compared to Group S. In all three treatment groups, erectile responses, protein expression of fibronectin, and SM/collagen ratio were improved. Group I + L + U showed greater improvement in erectile response than Group I + L. SM content and apoptotic index in Groups I + U and I + L + U were improved compared to those in Group I. However, Group I + L did not show a significant improvement in SM content or apoptotic index. The number of phospho-LIMK2-positive fibroblasts was normalized in Groups I + L and I + L + U, but not in Group I + U. Akt/eNOS phosphorylation was improved in Groups I + U and I + L + U, but not in Group I + L. LIMK2/cofilin phosphorylation was improved in Groups I + L and I + L + U, but not in Group I + U. Our data indicate that combined treatment of LIMK2i and PDE5i immediate after CN injury could improve erectile function by improving cavernous apoptosis or eNOS phosphorylation and suppressing cavernous fibrosis. Rectification of Akt/eNOS and LIMK2/cofilin pathways appears to be involved in their improvement.
Animals ; Apoptosis/drug effects* ; Arterial Pressure ; Electric Stimulation ; Erectile Dysfunction/pathology* ; Lim Kinases/antagonists & inhibitors* ; Male ; Nerve Crush ; Nitric Oxide Synthase Type III/metabolism* ; Penis/pathology* ; Peripheral Nerve Injuries/pathology* ; Phosphodiesterase 5 Inhibitors/therapeutic use* ; Phosphorylation ; Pyrimidines/therapeutic use* ; Rats ; Rats, Sprague-Dawley ; Sulfonamides/therapeutic use*

Vacuum erection device (VED), used to treat radical prostatectomy (RP)-associated erectile dysfunction, has attracted considerable attention. However, the optimal negative pressure remains to be determined. This investigation explored the optimal pressure for VED therapy in penile rehabilitation. Thirty-six 9-week-old male rats were randomly divided into six groups: control groups (sham group, bilateral cavernous nerve crush [BCNC] group) and VED therapy groups (-200 mmHg group, -300 mmHg group, -400 mmHg group, -500 mmHg group). BCNC group and VED therapy groups underwent BCNC surgery. Intracavernosal pressure (ICP)/mean arterial pressure (MAP) ratio was calculated to assess erectile function. Masson's trichrome (MT) staining, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, immunohistochemistry, and real-time polymerase chain reaction (RT-PCR) were performed to explore cellular and molecular changes of the penis. Compared to the BCNC group, ICP/MAP ratios in all VED treatment groups were improved significantly (all P < 0.05), but there were no statistically significant differences among VED therapy groups. With increased pressure, complications gradually emerged and increased in frequency. Expression of molecular indicators, such as endothelial nitric oxide synthase (eNOS) and alpha-smooth muscle actin (α-SMA), increased after VED therapy, and hypoxia-inducible factor 1α (HIF-1α) and transforming growth factor beta (TGF-β) decreased. In addition, VED therapy improved the outcomes of MT and TUNEL assay. This investigation demonstrated a pressure of -200 mmHg in a rat model is optimal for VED therapy for penile rehabilitation after RP. No further benefits were observed with increased pressure, despite an increase in complications.
Animals ; Disease Models, Animal ; Erectile Dysfunction/therapy* ; Male ; Penile Erection ; Penis/pathology* ; Pressure ; Prostatectomy/rehabilitation* ; Rats ; Rats, Sprague-Dawley ; Vacuum

The present study aimed to identify which mitogen-activated protein kinase (p38 or Jun amino-terminal kinase [JNK]) was involved in cavernosal apoptosis during the acute phase after cavernosal nerve crush injury (CNCI) in rats to ameliorate apoptosis of cavernosal tissue, such as smooth muscle (SM). A total of twenty 10-week-old male Sprague-Dawley rats were divided equally into two groups: sham surgery (S) and CNCI (I). The I group approximated the clinical situation of men undergoing radical prostatectomy using two 60-second compressions of both CNs with a microsurgical vascular clamp. At 2-week postinjury, erectile response was assessed using electrostimulation. Penile tissues were harvested for immunohistochemistry analysis of alpha-SM actin (α-SMA), western blot analysis, and double immunofluorescence analysis of α-SMA and phosphorylated p38 or JNK, as well as double immunofluorescent of TUNEL and phosphorylated p38 or JNK. At 2-week postinjury, the I group had a significantly lower intracavernous pressure (ICP)/mean arterial pressure (MAP) and a lower area under the curve (AUC)/MAP than the S group. The I group also exhibited decreased immunohistochemical staining of α-SMA, an increase in the number of SM cells positive for phosphorylated JNK, an increased number of apoptotic cells positive for phosphorylated JNK, and increased JNK phosphorylation compared with the S group. However, there was no significant difference in p38 phosphorylation expression or the number of SM cells positive for phosphorylated p38 between the two groups. In conclusion, our data suggest that JNK, not p38, is involved in cavernosal apoptosis during the acute phase after partial CN damage.
Animals ; Apoptosis ; Disease Models, Animal ; Electric Stimulation ; MAP Kinase Kinase 4/metabolism* ; Male ; Penile Erection ; Penis/pathology* ; Peripheral Nerve Injuries/pathology* ; Phosphorylation ; Prostatectomy ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; p38 Mitogen-Activated Protein Kinases/metabolism*