Increased Expression of the Neuroregenerative Peptide Galanin in the Major Pelvic Ganglion Following Cavernous Nerve Injury

IntroductionErectile dysfunction (ED) remains a frequent complication of radical prostatectomy due to injury to the cavernous nerves (CNs). A recent microarray showed the neuropeptide galanin to be one of the most strikingly upregulated genes in the rat major pelvic ganglion (MPG) after bilateral CN crush injury (BCNI).AimThe aim of this study is to evaluate the temporal regulation of galanin in the MPG after BCNI and its relationship to functional nerve regeneration.MethodsChanges in galanin, galanin receptor (galR), and c‐JUN mRNA expression were assessed in Sprague‐Dawley rats after sham operation (n = 10) and at 48 hours (n = 10), 7 (n = 10), 14 (n = 5), 21 (n = 5), 30 (n = 5), and 60 (n = 5) days after BCNI using quantitative PCR. Erectile function was assessed by measuring intracavernous pressure (ICP) divided by mean arterial pressure (MAP) during CN electrostimulation. Immunohistochemistry was performed on the MPG in sham‐operated animals and 5 days after BCNI.Main Outcome MeasuresICP/MAP upon CN stimulation; galanin, galR1, ‐2, ‐3, and c‐JUN mRNA expression at various time points after BCNI; and nNOS, galanin, and galR distribution in the MPG of sham‐operated rats and after BCNI.ResultsAfter BCNI, ICP/MAP values quickly deteriorate, while after 60 days, spontaneous restoration of erectile responses to CN stimulation is observed, reflecting CN regeneration. Galanin mRNA in the MPG is up to 186‐fold upregulated compared with sham‐operated rats at 48 hours and 7 days after BCNI and gradually declines with increasing time from injury, whereas galanin receptor expressions decrease and c‐JUN gradually increases. Galanin expression shows a strong inverse correlation with erectile responses to CN stimulation with time from injury. Injured MPGs show a colocalization between galanin‐ and nNOS‐positive neuronal cell population in the MPG.ConclusionsGalanin is upregulated in the MPG in the early phase after CN injury after which it gradually decreases and is present in nNOS‐positive neurons of the ganglion. We hypothesize that galanin upregulation is an important factor in the endogenous neuroregenerative response to CN injury. Weyne E, Albersen M, Hannan JL, Castiglione F, Hedlund P, Verbist G, De Ridder D, Bivalacqua TJ, and Van der Aa F. Increased expression of the neuroregenerative peptide galanin in the major pelvic ganglion following cavernous nerve injury. J Sex Med 2014;11:1685–1693.     

FK506 and Rapamycin Neuroprotect Erection and Involve Different Immunophilins in a Rat Model of Cavernous Nerve Injury

IntroductionImmunophilin ligands function by binding to receptor proteins such as FK506 binding proteins (FKBPs). FKBPs are studied for their roles in neuroprotection.AimCompare the effect of FK506 (FK) and rapamycin (RAP) on erectile function (EF) recovery and FKBP expressions in penis and major pelvic ganglion (MPG) after cavernous nerve (CN) injury.MethodsAdult male rats were divided into four groups: sham surgery (CN exposure only) + vehicle; bilateral CN injury (BCNI; bilateral crush, 3 minutes with hemostat clamp) + vehicle; BCNI + FK (5 mg/kg/day, 5 days, sc); and BCNI + RAP (2 mg/kg/day, 5 days, sc). At both 24 hours (Day 1) or 1 week (Day 7) after BCNI, EF was assessed by intracavernosal pressure measurement and FKBPs 12, 38, 52, and 65 expressions were evaluated by Western blot analysis in collected penises and MPGs.Main Outcome MeasuresEF and change in protein expressions of FKBPs in the rat penis and MPG after BCNI with and without immunophilin ligand treatment.ResultsBoth FK- and RAP-treated rats had preserved EF compared with vehicle-treated rats after BCNI. FKBPs changed variably following injury and treatment. In particular, in the penis at Day 1, FKBP 38 expression was decreased after BCNI and both FK and RAP attenuated this decrease. In MPG at Day 1, FKBP 38 expression was also decreased after BCNI and FK attenuated the decrease, while at Day 7, FKBP 38 expression was still decreased and RAP attenuated the decrease. Also, in the penis at Day 1, FKBP 65 expression decreased after BCNI and FK attenuated the decrease. In the MPG, FKBP 65 expression increased at both Days 1 and 7 with FK treatment.ConclusionsImproved EF after BCNI, as shown with RAP, further suggests a role of immunophilin ligands as a protective therapy of CN injury associated erectile dysfunction. Our findings also suggest that select FKBPs, such as FKBP 38 and FKBP 65, may mediate these effects. Lagoda G, Sezen SF, and Burnett AL. FK506 and rapamycin neuroprotect erection and involve different immunophilins in a rat model of cavernous nerve injury. J Sex Med 2009;6:1914–1923.     

Increased Level of Tumor Necrosis Factor-Alpha (TNF-α) Leads to Downregulation of Nitrergic Neurons Following Bilateral Cavernous Nerve Injury and Modulates Penile Smooth Tone

BackgroundErectile dysfunction (ED) after injury to peripheral cavernous nerve (CN) is partly a result of inflammation in pelvic ganglia, suggesting that ED may be prevented by inhibiting neuroinflammation.AimThe aim of this study is to examine temporal changes of TNF-α, after bilateral CN injury (BCNI), to evaluate effect of exogenous TNF-α on neurite outgrowth from major pelvic ganglion (MPG), and to investigate effect of TNF-α signal inhibition to evaluate effects of TNF-α on penile tone with TNF-α receptor knockout mice (TNFRKO).MethodsSeventy Sprague-Dawley rats were randomized to undergo BCNI or sham surgery. Sham rats’ MPGs were harvested after 48 hours, whereas BCNI groups’ MPGs were at 6, 12, 24, 48 hours, 7, or 14 days after surgery. qPCR was used to evaluate gene expression of markers for neuroinflammation in MPGs. Western blot was performed to evaluate TNF-α protein amount in MPGs. MPGs were harvested from healthy rats and cultured in Matrigel with TNF-α. Neurite outgrowth from MPGs was measured after 3 days, and TH and nNOS immunofluorescence was assessed. Wild type (WT) and TNFRKO mice were used to examine effect of TNF-α inhibition on smooth muscle function after BCNI. MPGs were harvested 48 hours after sham or BCNI surgery to evaluate gene expression of nNOS and TH.OutcomesGene expression of TNF-α signaling pathway, Schwann cell and macrophage markers, protein expression of TNF-α in MPGs, and penile smooth muscle function to electrical field stimulation (EFS) were evaluated.ResultsBCNI increased gene and protein expression of TNF-α in MPGs. Exogenous TNF-α inhibited MPG neurite outgrowth. MPGs cultured with TNF-α had decreased gene expression of nNOS (P < .05). MPGs cultured with TNF-α had shorter nNOS+ neurites than TH+ neurites (P < .01). Gene expression of nNOS was enhanced in TNFRKO mice compared to WT mice (P < .01). WT mice showed enhanced smooth muscle contraction of penises of WT mice was enhanced to EFS, compared to TNFKO (P < .01). Penile smooth-muscle relaxation to EFS was greater in TNFKO mice compared to WT (P < .01).Clinical TranslationTNF-α inhibition may prevent ED after prostatectomy.Strength/LimitationsTNF-α inhibition might prevent loss of nitrergic nerve apoptosis after BCNI and preserve corporal smooth muscle function but further investigation is required to evaluate protein expression of nNOS in MPGs of TNFKO mice.ConclusionsTNF-α inhibited neurite outgrowth from MPGs by downregulating gene expression of nNOS and TNFRKO mice showed enhanced gene expression of nNOS and enhanced penile smooth-muscle relaxation.Matsui H, Sopko NA, Campbell JD, et al. Increased Level of Tumor Necrosis Factor-Alpha (TNF-α) Leads to Downregulation of Nitrergic Neurons Following Bilateral Cavernous Nerve Injury and Modulates Penile Smooth Tone. J Sex Med 2021;18:1181–1190.     

GGF2 Is Neuroprotective in a Rat Model of Cavernous Nerve Injury-Induced Erectile Dysfunction

IntroductionErectile dysfunction is a major complication of radical prostatectomy, commonly associated with penile neuropathy. In animal models of peripheral nerve injury, glial growth factor-2 (GGF2), a member of the neuregulin family of growth factors, has neuroprotective and neurorestorative properties, but this potential has not been established after cavernous nerve (CN) injury.AimsThe effectiveness of GGF2 in preserving axonal integrity and recovering erectile function in a rat model of radical prostatectomy-associated CN injury.MethodsAdult male Sprague-Dawley rats underwent bilateral CN crush injury (BCNI) or sham surgery. Rats were administered GGF2 (0.5, 5, or 15 mg/kg) or vehicle subcutaneously 24 hour pre and 24-hour post-BCNI, and once weekly for 5 weeks. Erectile function was assessed in response to electrical stimulation of the CN. CN survival was assessed by fluorogold retrograde axonal tracing in major pelvic ganglia (MPG). Unmyelinated axons in the CNs were quantitated by electron microscopy.Main Outcome MeasuresErectile function recovery, CN survival, and unmyelinated CN axon preservation in response to GGF2 treatment following BCNI.ResultsErectile function was decreased (P < 0.05) after BCNI, and it was improved (P < 0.05) by all doses of GGF2. The number of fluorogold-labeled cells in the MPG was reduced (P < 0.05) by BCNI and was increased (P < 0.05) by GGF2 (0.5 and 5 mg/kg). The percentage of denervated Schwann cells in the BCNI group was higher (P < 0.05) than that in the sham-treated group and was decreased (P < 0.05) in the GGF2-treated (5 mg/kg) BCNI group. In the BCNI + GGF2 (5 mg/kg) group, the unmyelinated fiber histogram demonstrated a rightward shift, indicating an increased number of unmyelinated axons per Schwann cell compared with the BCNI group.ConclusionsGGF2 promotes erectile function recovery following CN injury in conjunction with preserving unmyelinated CN fibers. Our findings suggest the clinical opportunity to develop GGF2 as a neuroprotective therapy for radical prostatectomy. Burnett AL, Sezen SF, Hoke A, Caggiano AO, Iaci J, Lagoda G, Musicki B, and Bella AJ. GGF2 is neuroprotective in a rat model of cavernous nerve injury-induced erectile dysfunction. J Sex Med 2015;12:897–905.     

Therapeutic Effect of Adipose‐Derived Stem Cells and BDNF‐immobilized PLGA Membrane in a Rat Model of Cavernous Nerve Injury

IntroductionCavernous nerve injury is the main reason for post‐prostatectomy erectile dysfunction (ED). Stem cell and neuroprotection therapy are promising therapeutic strategy for ED.AimTo evaluate the therapeutic efficacy of adipose‐derived stem cells (ADSCs) and brain‐derived neurotrophic factor (BDNF) immobilized Poly‐Lactic‐Co‐Glycolic (PLGA) membrane on the cavernous nerve in a rat model of post‐prostatectomy ED.MethodsRats were randomly divided into five groups: normal group, bilateral cavernous nerve crush injury (BCNI) group, ADSC (BCNI group with ADSCs on cavernous nerve) group, BDNF‐membrane (BCNI group with BDNF/PLGA membrane on cavernous nerve) group, and ADSC/BDNF‐membrane (BCNI group with ADSCs covered with BDNF/PLGA membrane on cavernous nerve) group. BDNF was controlled‐released for a period of 4 weeks in a BDNF/PLGA porous membrane system.Main Outcome MeasuresFour weeks after the operation, erectile function was assessed by detecting the ratio of intra‐cavernous pressure (ICP)/mean arterial pressure (MAP). Smooth muscle and collagen content were determined by Masson's trichrome staining. Neuronal nitric oxide synthase (nNOS) expression in the dorsal penile nerve was detected by immunostaining. Phospho‐endothelial nitric oxide synthase (eNOS) protein expression and cyclic guanosine monophosphate (cGMP) level of the corpus cavernosum were quantified by Western blotting and cGMP assay, respectively.ResultsIn the ADSC/BDNF‐membrane group, erectile function was significantly elevated, compared with the BCNI and other treated groups. ADSC/BDNF‐membrane treatment significantly increased smooth muscle/collagen ratio, nNOS content, phospho‐eNOS protein expression, and cGMP level, compared with the BCNI and other treated groups.ConclusionsADSCs with BDNF‐membrane on the cavernous nerve can improve erectile function in a rat model of post‐prostatectomy ED, which may be used as a novel therapy for post‐prostatectomy ED. Piao S, Kim IG, Lee JY, Hong SH, Kim SW, Hwang T‐K., Heang S, Lee JH, Ra JC, and Lee JY. Therapeutic effect of adipose‐derived stem cells and BDNF‐immobilized PLGA membrane in a rat model of cavernous nerve injury. J Sex Med 2012;9:1968–1979.     

Galanin Administration Partially Restores Erectile Function After Cavernous Nerve Injury and Mediates Endogenous Nitrergic Nerve Outgrowth In Vitro

Background

Previously, we found that the neuropeptide galanin was strongly upregulated soon after bilateral cavernous nerve injury (BCNI) and that galanin and its receptors were expressed in nitrergic erectile innervation. Galanin has been observed to exert neuroregenerative effects in dorsal root ganglion neurons, but evidence for these effects in the major pelvic ganglion (MPG) after BCNI is lacking.

Valproic Acid Prevents Penile Fibrosis and Erectile Dysfunction in Cavernous Nerve‐Injured Rats

IntroductionBilateral cavernous nerve injury (BCNI) causes profound penile changes such as apoptosis and fibrosis leading to erectile dysfunction (ED). Histone deacetylase (HDAC) has been implicated in chronic fibrotic diseases.AimsThis study will characterize the molecular changes in penile HDAC after BCNI and determine if HDAC inhibition can prevent BCNI‐induced ED and penile fibrosis.MethodsFive groups of rats (8–10 weeks, n = 10/group) were utilized: (i) sham; (ii and iii) BCNI 14 and 30 days following injury; and (iv and v) BCNI treated with HDAC inhibitor valproic acid (VPA 250 mg/kg; 14 and 30 days). All groups underwent cavernous nerve stimulation (CNS) to determine intracavernosal pressure (ICP). Penile HDAC3, HDAC4, fibronectin, and transforming growth factor‐β1 (TGF‐β1) protein expression (Western blot) were assessed. Trichrome staining and the fractional area of fibrosis were determined in penes from each group. Cavernous smooth muscle content was assessed by immunofluorescence to alpha smooth muscle actin (α‐SMA) antibodies.Main Outcome MeasuresWe measured ICP; HDAC3, HDAC4, fibronectin, and TGF‐β1 protein expression; penile fibrosis; penile α‐SMA content.ResultsThere was a voltage‐dependent decline (P < 0.05) in ICP to CNS 14 and 30 days after BCNI. Penile HDAC3, HDAC4, and fibronectin were significantly increased (P < 0.05) 14 days after BCNI. There was a slight increase in TGF‐β1 protein expression after BCNI. Histological analysis showed increased (P < 0.05) corporal fibrosis after BCNI at both time points. VPA treatment decreased (P < 0.05) penile HDAC3, HDAC4, and fibronectin protein expression as well as corporal fibrosis. There was no change in penile α‐SMA between all groups. Furthermore, VPA‐treated BCNI rats had improved erectile responses to CNS (P < 0.05).ConclusionHDAC‐induced pathological signaling in response to BCNI contributes to penile vascular dysfunction. Pharmacological inhibition of HDAC prevents penile fibrosis, normalizes fibronectin expression, and preserves erectile function. The HDAC pathway may represent a suitable target in preventing the progression of ED occurring post‐radical prostatectomy. Hannan JL, Kutlu O, Stopak BL, Liu X, Castiglione F, Hedlund P, Burnett AL, and Bivalacqua TJ. Valproic acid prevents penile fibrosis and erectile dysfunction in cavernous nerve‐injured rats. J Sex Med 2014;11:1442–1451.     

Insulin-Like Growth Factor-1–Loaded Polymeric Poly(Lactic-Co-Glycolic) Acid Microspheres Improved Erectile Function in a Rat Model of Bilateral Cavernous Nerve Injury

Background

Previous studies have documented improvement in erectile function after bilateral cavernous nerve injury (BCNI) in rats with the use of pioglitazone. Our group determined this improvement to be mediated by the insulin-like growth factor-1 (IGF-1) pathway.

Low-Intensity Electrostimulation Enhances Neuroregeneration and Improves Erectile Function in a Rat Model of Cavernous Nerve Injury

BackgroundNeurogenic erectile dysfunction (ED) following radical prostatectomy (RP) is a frequent complication often leading to erectile tissue remodeling and permanent ED. Low-intensity electrostimulation (LIES) has been shown to enhance peripheral nerve regeneration, however, its application on cavernous nerves (CN) has never been investigated.AimsTo investigate whether LIES enhances CN regeneration, improves erectile function (EF) recovery, and prevents corpora cavernosal remodeling after CN injury, which is a principal factor for ED following RP.MethodsAdult male Sprague-Dawley rats were divided into Sham, Bilateral Cavernous Nerve Injury (BCNI), and BCNI + LIES (1V, 0.1ms, 12Hz, 1h/day). After 7days, EF was assessed (ICP measurement). Penes and CN were collected for molecular analyses of TGF-$\beta$1, Il-6, CRP, eNOS, ERK and AKT protein levels in corpus cavernosum (CC), and immunohistological analysis of DHE, total collagen and α-SMA in CC and S-100, Tub-III, DAPI, TUNEL, and nNOS in CN.OutcomesEffects of LIES on EF, erectile tissue remodeling and CN structure.ResultsEF was decreased (P < .05) 7 days after BCNI and increased (P < .05) by LIES. Intracavernosal reactive oxygen species (DHE) was increased (P < .05) after BCNI and normalized by LIES. Protein expressions of TGF-β1, IL-6, and CRP were increased in the penis (P < .05) after BCNI and normalized by LIES. The α-SMA and/or total collagen ratio was decreased (P < .05) after BCNI in the penis and normalized by LIES. Protein expression ratio of p-ERK/ERK and p-AKT/AKT did not change after BCNI but increased (P < .05) in LIES group. Myelination and number of nNOS positive cells in the CN were decreased (P < .05) after BCNI and normalized by LIES. The number of apoptotic nerve cells within the dorsal penile nerve was increased (P < .05) after BCNI and decreased (P < .05) by LIES compared to the BCNI group. There were no differences in eNOS expression in the penis between study groups.Clinical TranslationLIES may offer a potential new tool for penile rehabilitation and ED management following RP, potentially enhancing EF recovery and minimizing the side effects of this surgery.Strengths & LimitationsThis study provides evidence of the protective effect of LIES on EF and tissue remodeling following CN injury; nevertheless, this study has been conducted on animals and the translation to humans remains to be demonstrated. Further research to identify the underlying mechanisms of action is required.ConclusionThis study demonstrates that LIES of the CN after CN injury protects CN structure, enhances EF recovery, and prevents corpora cavernosal remodeling.Sturny M, Karakus S, Fraga-Silva R, et al. Low-Intensity Electrostimulation Enhances Neuroregeneration and Improves Erectile Function in a Rat Model of Cavernous Nerve Injury. J Sex Med 2022;19:686–696.     

Ex Vivo Radiation Leads to Opposing Neurite Growth in Whole Ganglia vs Dissociated Cultured Pelvic Neurons

BackgroundProstatic radiation therapy (RT) often causes erectile dysfunction (ED) and the mechanisms governing RT-induced ED are unclear with a lack of therapeutic strategies.AimTo determine the effects of ex vivo RT on major pelvic ganglion (MPG) neuron survival, and neurite growth in whole vs dissociated culture.MethodsMPGs were removed and irradiated (0 or 8 Gy) from male Sprague Dawley rats. For dissociated culture, MPG neurons were digested in collagenase/dispase and cultured on coverslips. Immunofluorescent staining for beta-tubulin III (TUBB3; neuron marker), neuronal nitric oxide synthase (nNOS; nitrergic marker), tyrosine hydroxylase (TH; sympathetic marker), and terminal deoxynucleotidyl transferase dUTP nick end labeling assessed neurite length, branching, autonomic neuron density, and apoptosis. For whole organ culture, MPGs were grown in Matrigel. Gene expression of apoptotic markers (caspase 1, 3), TUBB3, nNOS, TH, and Schwann cells (Sox10, Krox20, glial fibrillary acid protein) was measured in whole organ cultured MPGs by quantitative polymerase chain reaction.OutcomesAfter 72 hours, neurite length, branching, autonomic neuron density, and apoptosis were assessed, and gene expression was measured.ResultsRT increased apoptosis in dissociated neurons measured by terminal deoxynucleotidyl transferase dUTP nick end labeling (P < .001) and whole MPG culture via upregulation of caspase 3 gene expression (P < .05). Nitrergic neurons were markedly decreased in irradiated dissociated culture (P < .05), while nNOS gene expression was upregulated in irradiated whole organ culture (P < .05). The proportion of dissociated sympathetic neurons and whole organ TH gene expression remained unchanged after RT. Interestingly, RT dissociated neurites were 22% shorter than controls, while RT whole organ neurites were 15% longer than controls (P < .01). MPG Schwann cells markers (Sox10, Krox20) were elevated after RT in whole organ culture.Clinical TranslationProstatic RT leads to increased neuronal cell death and less erectogenic nitrergic neurons contributing to ED.Strengths & LimitationsThe advantages of dissociated neuron culture include distinct neurites which are easily measured for apoptosis, length/branching, and specific neuron types. In contrast, whole MPG culture is advantageous as it contains all the supporting cells present in vivo.ConclusionThe 2 different culture methods demonstrated opposing neurite growth after RT indicating the importance of supporting cell network to promote pelvic neuron neuritogenesis and survival following RT.Randolph JT, Pak ES, Koontz BF, et al. Ex Vivo Radiation Leads to Opposing Neurite Growth in Whole Ganglia vs Dissociated Cultured Pelvic Neurons. J Sex Med 2020;17:1423–1433.     

Intravenous Preload of Mesenchymal Stem Cells Rescues Erectile Function in a Rat Model of Cavernous Nerve Injury

IntroductionWe evaluated the potential preventive effects and mechanisms of intravenously preloaded mesenchymal stem cells (MSCs) for erectile dysfunction (ED) in a cavernous nerve (CN) injury model.MethodsMale Sprague–Dawley (SD) rats were used for this study. Rats were randomized into two groups. One group was intravenously preloaded with MSCs (1.0 × 10⁶ cells in 1 mL total fluid volume) and the other was infused with medium alone (1 mL Dulbecco's modified Eagle's medium [DMEM]) for sham control, respectively. Crushed CN injury was induced immediately after infusion. The surgeon was blind to the experimental conditions (MSC or medium).Main Outcome MeasuresTo assess erectile function, we measured the intracavernous pressure (ICP) and arterial pressure (AP) at 1 hour and 2 weeks after CN injury. After measuring the initial ICP/AP of pre‐injury (normal) male SD rats, they were randomized into the two groups and infused with MSCs or medium. PKH26‐labelled MSCs were used for tracking. To investigate the mRNA expression levels of neurotrophins in the major pelvic ganglia (MPG), we performed real‐time quantitative real‐time polymerase chain reaction.ResultsThe reduction of ICP/AP and area under the curve of ICP (ICP‐AUC) in the MSC group was significantly lower than in the DMEM group (P < 0.05; P < 0.05) at 1 hour. The ICP/AP and ICP‐AUC at 2 weeks post‐injury in the MSC group was significantly higher than in the DMEM group (P < 0.01; P < 0.05). The preloaded PKH26‐labelled MSCs were detected in the MPG and CN using confocal microscopy indicating homing of the cells to the injured nerve and ganglia. Glia cell‐derived neurotrophic factor (GDNF) and neurturin, which are important neurotrophic factors for erection, had expression levels in MPG significantly higher in the MSC group than in the DMEM group (P < 0.01, 0.05).ConclusionIntravenous preload of MSCs before a CN injury may prevent or reduce experimental ED. Takayanagi A, Sasaki M, Kataoka‐Sasaki Y, Kobayashi K, Matsuda Y, Oka S, Masumori N, Kocsis JD and Honmou O. Intravenous preload of mesenchymal stem cells rescues erectile function in a rat model of cavernous nerve injury. J Sex Med 2015;12:1713–1721.     

Effects of Intravenous Injection of Adipose‐Derived Stem Cells in a Rat Model of Radiation Therapy‐Induced Erectile Dysfunction

IntroductionRadiation therapy (RT) for prostate cancer is frequently associated with posttreatment erectile dysfunction (ED).AimTo investigate whether injection of adipose‐derived stem cells (ADSCs) can ameliorate RT‐associated ED.MethodsThirty male rats were divided into three groups. The control + phosphate‐buffered saline (PBS) group received tail‐vein injection of PBS. The radiation + PBS group received radiation over the prostate and tail‐vein injection of PBS. The radiation + ADSC group received radiation over the prostate and tail‐vein injection of ADSCs, which were labeled with 5‐ethynyl‐2‐deoxyuridine (EdU). Seventeen weeks later, erectile function was evaluated by intracavernous pressure (ICP) in response to electrostimulation of cavernous nerves (CNs). Penile tissue and major pelvic ganglia (MPG) were examined by immunofluorescence (IF) and EdU staining.Main Outcome MeasuresErectile function was measured by ICP. Protein expression was examined by IF, followed by image analysis and quantification.ResultsRadiation over the prostate caused a significant decrease in erectile function and in the expression of neuronal nitric oxide synthase (nNOS) in penis and MPG. Cavernous smooth muscle (CSM) but not endothelial content was also reduced. Injection of ADSCs significantly restored erectile function, nNOS expression, and CSM content in the irradiated rats. EdU‐positive cells were visible in MPG.ConclusionsRadiation appears to cause ED via CN injury. ADSC injection can restore erectile function via CN regeneration. Qiu X, Villalta J, Ferretti L, Fandel TM, Albersen M, Lin G, Dai Y, Lue TF, and Lin C‐S. Effects of intravenous injection of adipose‐derived stem cells in a rat model of radiation therapy‐induced erectile dysfunction. J Sex Med 2012;9:1851–1858.     

Intracavernous Delivery of Freshly Isolated Stromal Vascular Fraction Rescues Erectile Function by Enhancing Endothelial Regeneration in the Streptozotocin‐Induced Diabetic Mouse

IntroductionMen with diabetic erectile dysfunction (ED) often have severe endothelial dysfunction and respond poorly to oral phosphodiesterase‐5 inhibitors.AimTo examine whether and how freshly isolated stromal vascular fraction (SVF) promotes cavernous endothelial regeneration and restores erectile function in diabetic animals.MethodsEight‐week‐old C57BL/6J mice were used. Diabetes was induced by intraperitoneal injection of streptozotocin. SVF was isolated from epididymal adipose tissues of green fluorescence protein transgenic mice. At 8 weeks after the induction of diabetes, the animals were divided into six groups: controls, diabetic mice, and diabetic mice treated with a single intracavernous injection of phosphate‐buffered saline (PBS) or SVF (1 × 10⁴ cells, 1 × 10⁵ cells, or 2 × 10⁵ cells/20 µL, respectively).Main Outcome MeasuresTwo weeks later, erectile function was measured by cavernous nerve stimulation. The penis was stained with antibodies to CD31, CD34, phosphohistone H3, phospho‐endothelial nitric oxide synthase (eNOS), and vascular endothelial growth factor‐A (VEGF‐A). We also performed Western blot for phospho‐eNOS and eNOS, and determined cyclic guanosine monophosphate (cGMP) concentration in the corpus cavernosum tissue.ResultsSignificant improvement in erectile function was noted in diabetic mice treated with SVF at concentrations of 1 × 10⁵ and 2 × 10⁵ cells, which reached up to 82% of the control values. Local delivery of SVF significantly increased cavernous endothelial cell proliferation, eNOS phosphorylation, and cGMP expression compared with that in the untreated group and the PBS‐treated diabetic group. Intracavernous injection of SVF increased cavernous VEGF‐A expression and induced recruitment of CD34(+)CD31(?) progenitor cells. Some SVF underwent differentiation into cavernous endothelial cells. SVF‐induced promotion of cavernous angiogenesis and erectile function was abolished in the presence of VEGF‐Trap, a soluble VEGF‐A neutralizing antibody.ConclusionThe results support the concept of cavernous endothelial regeneration by use of SVF as a curative therapy for diabetic ED. Ryu J‐K, Tumurbaatar M, Jin H‐R, Kim WJ, Kwon M‐H, Piao S, Choi MJ, Yin GN, Song K‐M, Kang Y‐J, Koh YJ, Koh GY, and Suh J‐K. Intracavernous delivery of freshly isolated stromal vascular fraction rescues erectile function by enhancing endothelial regeneration in the streptozotocin‐induced diabetic mouse. J Sex Med 2012;9:3051–3065.     

Oral Administration of the p75 Neurotrophin Receptor Modulator,LM11A-31, Improves Erectile Function in a Mouse Model of Cavernous Nerve Injury

BackgroundRadical prostatectomy for prostate cancer can not only induce cavernous nerve injury (CNI), but also causes cavernous hypoxia and cavernous structural changes, which lead to a poor response to phosphodiesterase 5 inhibitors.AimTo investigate the therapeutic effect of oral administration of LM11A-31, a small molecule p75 neurotrophin receptor (p75^NTR) ligand and proNGF antagonist, in a mouse model of bilateral CNI, which mimics nerve injury–induced erectile dysfunction after radical prostatectomy.Methods8-week-old male C57BL/6 mice were divided into sham operation and CNI groups. Each group was divided into 2 subgroups: phosphate-buffered saline and LM11A-31 (50 mg/kg/day) being administered once daily starting 3 days before CNI via oral gavage. 2 weeks after CNI, we measured erectile function by electrical stimulation of the bilateral cavernous nerve. The penis was harvested for histologic examination and Western blot analysis. The major pelvic ganglia was harvested and cultured for assays of ex vivo neurite outgrowth.OutcomesIntracavernous pressure, neurovascular regeneration in the penis, in vivo or ex vivo functional evaluation, and cell survival signaling were measured.ResultsErectile function was decreased in the CNI group (44% of the sham operation group), while administration of LM11A-31 led to a significant improvement of erectile function (70% of the sham operation group) in association with increased neurovascular content, including cavernous endothelial cells, pericytes, and neuronal processes. Immunohistochemical and Western blot analyses showed significantly increased p75^NTR expression in the dorsal nerve of CNI mice, which was attenuated by LM11A-31 treatment. Protein expression of active PI3K, AKT, and endothelial nitric oxide synthase was increased, and cell death and c-Jun N-terminal kinase signaling was significantly attenuated after LM11A-31 treatment. Furthermore, LM11A-31 promoted neurite sprouting in cultured major pelvic ganglia after lipopolysaccharide exposure.Clinical ImplicationsLM11A-31 may be used as a strategy to treat erectile dysfunction after radical prostatectomy or in men with neurovascular diseases.Strengths & LimitationsUnlike biological therapeutics, such as proteins, gene therapies, or stem cells, the clinical application of LM11A-31 would likely be relatively less complex and low cost. Our study has some limitations. Future studies will assess the optimal dosing and duration of the compound. Given its plasma half-life of approximately 1 hour, it is possible that dosing more than once per day will provide added efficacy.ConclusionSpecific inhibition of the proNGF-p75^NTR degenerative signaling via oral administration of LM11A-31 represents a novel therapeutic strategy for erectile dysfunction induced by nerve injury.Yin GN, Ock J, Limanjaya A, et al. Oral Administration of the p75 Neurotrophin Receptor Modulator, LM11A-31, Improves Erectile Function in a Mouse Model of Cavernous Nerve Injury. J Sex Med 2021;18:17–28.     

Intracavernous Delivery of Stromal Vascular Fraction Restores Erectile Function Through Production of Angiogenic Factors in a Mouse Model of Cavernous Nerve Injury

IntroductionErectile dysfunction (ED) is a major complication of radical prostatectomy. Men with radical prostatectomy‐induced ED respond less positively to oral phosphodiesterase‐5 inhibitors.AimThe study aims to examine whether and how stromal vascular fraction (SVF) restores erectile function in mice with cavernous nerve injury (CNI).MethodsTwelve‐week‐old male C57BL/6J mice were used and the animals were distributed into five groups: sham operation group and CNI group receiving a single intracavernous injection of phosphate‐buffered saline (PBS) or SVF (1 × 10⁴, 1 × 10⁵, or 3 × 10⁵ cells/20 μL, respectively). SVF was isolated from epididymal adipose tissues of green fluorescence protein transgenic mice.Main Outcome MeasuresTwo weeks after injection, erectile function was measured by cavernous nerve stimulation. The penis was stained with antibodies to platelet/endothelial cell adhesion molecule‐1, phosphohistone H3, and phosphorylated endothelial nitric oxide synthase (phospho‐eNOS). We also performed Western blot for angiopoietin‐1 (Ang‐1), vascular endothelial growth factor‐A, hepatocyte growth factor, phospho‐eNOS, and eNOS in the corpus cavernosum tissue.ResultsLocal delivery of SVF restored erectile function in a dose‐dependent manner in CNI mice. The highest erectile response was noted at a dose of 3 × 10⁵ cells, for which the response was comparable with that in the sham operation group. Local delivery of SVF significantly increased the expression of angiogenic factor proteins and induced cavernous endothelial cell proliferation and eNOS phosphorylation compared with that in the PBS‐treated CNI group. SVF‐induced promotion of cavernous angiogenesis and erectile function was diminished in the presence of soluble antibody to Tie2, a receptor tyrosine kinase of Ang‐1.ConclusionSecretion of angiogenic factors from SVF is an important mechanism by which SVF induces cavernous endothelial regeneration and restores erectile function. These findings suggest that cavernous endothelial regeneration by using SVF may represent a promising treatment strategy for radical prostatectomy‐induced ED. Song K‐M, Jin H‐R, Park J‐M, Choi MJ, Kwon M‐H, Kwon K‐D, Batbold D, Yin GN, Kim WJ, Koh GY, Ryu J‐K, and Suh J‐K. Intracavernous delivery of stromal vascular fraction restores erectile function through production of angiogenic factors in a mouse model of cavernous nerve injury. J Sex Med 2014;11:1962–1973.     

A Mouse Model of Cavernous Nerve Injury-Induced Erectile Dysfunction: Functional and Morphological Characterization of the Corpus Cavernosum

IntroductionWith the advent of genetically engineered mice, it seems important to develop a mouse model of cavernous nerve injury (CNI).AimTo establish a mouse model of CNI induced either by nerve crushing or by neurectomy and to evaluate time-dependent derangements in penile hemodynamics in vivo and subsequent histologic alterations in the cavernous tissue.MethodsTwelve-week-old C57BL/6J mice were divided into 4 groups (N = 36 per group): control, sham operation, bilateral cavernous nerve crush, and bilateral cavernous neurectomy group.Main Outcome MeasuresThree days and 1, 2, 4, 8, and 12 weeks after CNI, erectile function was measured by electrical stimulation of the cavernous nerve. The penis was then harvested and TUNEL was performed. Immunohistochemical analysis was performed assaying for caspase-3, transforming growth factor-β1 (TGF-β1), phospho-Smad2, PECAM-1, factor VIII, and smooth muscle α-actin. The numbers of apoptotic cells and phospho-Smad2-immunopositive cells in endothelial cells or smooth muscle cells were counted.ResultsErectile function was significantly less in the cavernous nerve crushing and neurectomy groups than in the control or sham group. This difference was observed at the earliest time point assayed (day 3) and persisted up to 4 weeks after nerve crushing and to 12 weeks after neurectomy. The apoptotic index peaked at 1 or 2 weeks after CNI and decreased thereafter. Cavernous TGF-β1 and phospho-Smad expression was also increased after CNI. The numbers of apoptotic cells and phospho-Smad2-immunopositive cells in cavernous endothelial cells and smooth muscle cells were significantly greater in the cavernous nerve crush and cavernous neurectomy groups than in the control or sham group.ConclusionThe mouse is a useful model for studying pathophysiologic mechanisms involved in erectile dysfunction after CNI. Early intervention to prevent apoptosis in smooth muscle cells and endothelial cells or to inhibit cavernous tissue fibrosis is required to restore erectile function. Jin H-R, Chung YG, Kim WJ, Zhang LW, Piao S, Tuvshintur B, Yin GN, Shin SH, Tumurbaatar M, Han J-Y, Ryu J-K, and Suh J-K. A mouse model of cavernous nerve injury-induced erectile dysfunction: Functional and morphological characterization of the corpus cavernosum.     

Inhibition of interleukin-6 attenuates erectile dysfunction in a rat model of nerve-sparing radical prostatectomy

IntroductionThe precise mechanisms underlying erectile dysfunction (ED) occurring after cavernous nerve (CN)‐sparing surgery remain to be determined.AimTo evaluate the expression of interleukin‐6 (IL‐6) and IL‐6 receptor (IL‐6R) after CN injury, and the effect of inhibiting IL‐6 bioactivity on nerve injury‐related ED.MethodsMale Sprague‐Dawley rats were divided into three groups: sham operation; bilateral CN dissection without crushing or cutting; and bilateral CN resection. In the interventional experiment, male rats underwent bilateral CN dissection, and anti‐rat IL‐6 antibody in phosphate‐buffered saline (PBS) or vehicle alone was injected intraperitoneally immediately and 24 hours after CN dissection.Main Outcome MeasuresOne, 3, 7, 28, and 56 days after surgery, the expression of IL‐6 and IL‐6R in the major pelvic ganglion (MPG) was examined by real‐time polymerase chain reaction. In the interventional experiment, erectile function was assessed by determining intracavernous pressure divided by arterial pressure (ICP/AP) during electrical pelvic nerve stimulation at 4 weeks after surgery in the anti‐IL‐6‐injected rats and PBS‐injected rats. The degree of nerve injury was also evaluated by retrograde dye tracing with Fluorogold.ResultsThe expression levels of IL‐6 and IL‐6R were increased in the early period of CN injury, as compared with the sham group. IL‐6 expression on day 1 was particularly enhanced. Four weeks after CN dissection, the anti‐IL‐6 group had greater ICP/AP and more FG‐positive cells than the PBS group.ConclusionsExpression levels of IL‐6 in the MPG were increased in the acute phase following CN injury. Inhibition of IL‐6 bioactivity attenuated ED following CN dissection. Thus, the suppression of excess inflammatory responses in the acute phase may lead to improvements in ED occurring after nerve‐sparing radical prostatectomy. Yamashita S, Kato R, Kobayashi K, Hisasue S, Arai Y, and Tsukamoto T. Inhibition of interleukin‐6 attenuates erectile dysfunction in a rat model of nerve‐sparing radical prostatectomy. J Sex Med 2011;8:1957–1964.     

Exosome Released From Schwann Cells May Be Involved in Microenergy Acoustic Pulse–Associated Cavernous Nerve Regeneration

BackgroundNeurogenic erectile dysfunction (ED) is often refractory to treatment because of insufficient functional nerve recovery after injury or insult. Noninvasive mechano-biological intervention, such as microenergy acoustic pulse (MAP), low-intensity pulsed ultrasound, and low-intensity extracorporeal shockwave treatment, is an optimal approach to stimulate nerve regeneration.AimTo establish a new model in vitro to simulate nerve injury in neurogenic ED and to explore the mechanisms of MAP in vitro.MethodsSprague-Dawley rats were used to isolate Schwann cells (SCs), major pelvic ganglion (MPG), and cavernous nerve with MPG (CN/MPG). SCs were then treated with MAP (0.033 mJ/mm², 1 Hz, 100 pulses), and SC exosomes were isolated. The MPG and CN/MPG were treated with MAP (0.033 mJ/mm², 1 Hz) at different dosages (25, 50, 100, 200, or 300 pulses) or exosomes derived from MAP-treated SCs in vitro.OutcomesNeurite growth from the MPG fragments and CN was photographed and measured. Expression of neurotropic factors (brain-derived neurotrophic factor, nerve growth factor, and neurotrophin-3) was checked.ResultsNeurite outgrowth from MPG and CN/MPG was enhanced by MAP in a dosage response manner, peaking at 100 pulses. MAP promoted SC proliferation, neurotropic factor (brain-derived neurotrophic factor, nerve growth factor, and neurotrophin-3) expression, and exosome secretion. SC-derived exosomes significantly enhanced neurite outgrowth from MPG in vitro.Clinical ImplicationsMAP may have utility in the treatment of neurogenic ED by SC-derived exosomes.Strength & LimitationsWe confirmed that MAP enhances penile nerve regeneration through exsomes. Limitations of this study include that our study did not explore the exact mechanisms of how MAP increases SC exosome secretion nor whether MAP modulates the content of exosomes.ConclusionThis study revealed that neurite outgrowth from MPG was enhanced by MAP and by SC-derived exosomes which were isolated after MAP treatment. Our findings indicate that one mechanism by which MAP induces nerve regeneration is by stimulation of SCs to secrete exosomes.Peng D, Reed-Maldonado AB, Zhou F, et al. Exosome Released From Schwann Cells May Be Involved in Microenergy Acoustic Pulse–Associated Cavernous Nerve Regeneration. J Sex Med 2020;17:1618–1628.     

Pericyte-Derived Extracellular Vesicle–Mimetic Nanovesicles Restore Erectile Function by Enhancing Neurovascular Regeneration in a Mouse Model of Cavernous Nerve Injury

BackgroundExtracellular vesicle (EV)–mimetic nanovesicles (NVs) from embryonic stem cells have been observed to stimulate neurovascular regeneration in the streptozotocin-induced diabetic mouse. Pericytes play important roles in maintaining penile erection, yet no previous studies have explored the effects of pericyte-derived NVs (PC-NVs) in neurovascular regeneration in the context of erectile dysfunction.AimTo investigate the potential effect of PC-NVs in neurovascular regeneration.MethodsPC-NVs were isolated from mouse cavernous pericytes, and neurovascular regeneration was evaluated in an in vitro study. Twelve-week-old C57BL/6J mice were used to prepare cavernous nerve injury model. Erectile function evaluation, histologic examination of the penis, and Western blots were assessed 2 weeks after model creation and PC-NVs treatment.OutcomesThe main outcomes of this study are PC-NVs characterization, intracavernous pressure, neurovascular regeneration in the penis, and in vitro functional evaluation.ResultsThe PC-NVs were extracted and characterized by cryotransmission electron microscopy and EV-positive (Alix, TSG101, CD81) and EV-negative (GM130) markers. In the in vivo studies, PC-NVs successfully improved erectile function in cavernous nerve injury mice (∼82% of control values). Immunofluorescence staining showed significant increases in pericytes, endothelial cell, and neuronal contents. In the in vitro studies, PC-NVs significantly increased mouse cavernous endothelial cells tube formation, Schwann cell migration, and dorsal root ganglion and major pelvic ganglion neurite sprouting. Finally, Western blot analysis revealed that PC-NVs upregulated cell survival signaling (Akt and eNOS) and induced the expression of neurotrophic factors (brain-derived neurotrophic factor, neurotrophin-3, and nerve growth factor).Clinical ImplicationsPC-NVs may be used as a strategy to treat erectile dysfunction after radical prostatectomy or in men with neurovascular diseases.Strengths & LimitationsWe evaluated the effect of PC-NVs in vitro and in a mouse nerve injury model, cavernous nerve injury. Additional studies are necessary to determine the detailed mechanisms of neurovascular improvement. Further study is needed to test whether PC-NVs are also effective when given weeks or months after nerve injury.ConclusionPC-NVs significantly improved erectile function by enhancing neurovascular regeneration. Local treatment with PC-NVs may represent a promising therapeutic strategy for the treatment of neurovascular diseases.Yin GN, Park S-H, Ock J, et al. Pericyte-Derived Extracellular Vesicle–Mimetic Nanovesicles Restore Erectile Function by Enhancing Neurovascular Regeneration in a Mouse Model of Cavernous Nerve Injury. J Sex Med 2020;17:2118–2128.