Mechanisms of Disease: new insights into the cellular and molecular pathology of Peyronie's disease

Rat as an animal model for Peyronie's disease research: a review of current methods and the peer-reviewed literature

While the exact mechanism of Peyronie's disease (PD) remains an enigma, the pathophysiology of PD is considered to be multifactorial, with interactions of genetic predisposition, trauma, tissue inflammation and aberrant wound healing. A non-systematic review of the existing English language literature pertaining to the use of rodent models in the evaluation of PD was performed using the Medline database. Multiple free-text searches were performed on key words: animal models of PD, transforming growth factor β1 (TGF β1), tunical and/or corporal fibrosis, subtunical injection and penile myofibroblasts. The most frequently reported models of PD can be classified as TGF β1, fibrin and surgical trauma-induced models. In vitro studies using Peyronie's fibroblast culture media have also provided further insights into cellular mechanism of PD. At the present time, the research in PD is hampered by the lack of universally accepted animal model and this is likely attributed to the limited insight into PD mechanisms and the difficulties faced by current animal models to truly represent the complexity and complete spectrum of human disease.

A Population-Based Study of Peyronie's Disease: Prevalence and Treatment Patterns in the United States

Purpose. To estimate the US prevalence of Peyronie's disease (PD) from patient-reported data and to identify diagnosis and treatment patterns. Methods. 11,420 US males ≥18 years old completed a brief web-based survey regarding the presence of PD, past treatments, and penile symptoms (Phase 1). Phase 1 respondents with PD diagnosis, history of treatment, or PD-related symptoms then completed a disease-specific survey (Phase 2). Results. Estimated prevalence of PD ranged from 0.5% (diagnosis of PD) to 13% (diagnosis, treatment, or penile symptoms). Thirty-six percent of Phase 2 participants reported that penile symptoms interfered with sexual activities. Of participants who sought treatment for penile symptoms (n = 128), 73% initially saw a primary care physician, 74% did not receive treatment from their first doctor, and 92% were not diagnosed with PD. Conclusions. PD may be underdiagnosed/undertreated in the US. Improved awareness is needed of PD symptoms and treatment options among health care professionals.

Penile duplex ultrasonography in men with Peyronie's disease: is it veno-occlusive dysfunction or poor cavernosal arterial inflow that contributes to erectile dysfunction?

INTRODUCTION

At least 20% of men with Peyronie's disease (PD) suffer from erectile dysfunction (ED). The fundamental mechanism is thought to arise from the progression of penile fibrosis, which was initially limited to the PD plaque within the tunica albuginea. However, recent studies have highlighted the possibility of fibrosis of the cavernosal vessel media wall leading to impairment of arterial inflow.

AIM

To evaluate the penile duplex ultrasonographic findings in PD of impotent men and to determine whether early features of PD might predict clinical progression.

MAIN OUTCOME MEASURES

Patient demographic, comorbidities, International Index of Erectile Function-5 scores, surgical intervention, and physical findings were documented. Penile curvature, plaque size, and peak systolic velocity (PSV) and end-diastolic velocity (EDV) on color duplex ultrasonography (CDU) were recorded.

METHODS

We performed a retrospective review of all men presenting with penile curvature and length loss who underwent penile CDU between January 2001 and January 2010.

RESULTS

A total of 1,120 men underwent penile CDU during the 10-year period. Complete information was obtained in 810 men; 250 men complained of decreased penile rigidity, while 150 men were unable to sustain erection. Comorbidities were similar between men with PD with and without ED. Tunical thickening (65%) was the most common CDU feature, and mean cumulative calcifications was 24.2 mm(2) (1-360 mm(2) , standard deviation 76). The PSV and EDV on the right cavernosal artery were 14.2 cm/second and 3.5 cm/second, while the left cavernosal artery measurements were 15.1 cm/second and 3.2 cm/second. Multivariate logistic regression model showed strong correlation between plaque size and development of ED. Both veno-occlusive dysfunction and impaired cavernosal arterial inflow were associated with ED.

CONCLUSIONS

Veno-occlusive dysfunction and impaired cavernosal arterial inflow contributed to the development of ED, and larger plaque size is a strong predictor of surgical intervention.

Current status and new developments in Peyronie's disease: medical, minimally invasive and surgical treatment options

INTRODUCTION

Peyronie's disease (PD) is a wound-healing disorder of the tunica albuginea of the penis which affects 3-9% of adult males. Clinically, any combination of plaque formation, penile pain, angulation and erectile dysfunction may appear. This condition may progress, stabilize or, uncommonly, regress during the initial acute phase (6-18 months).

AREAS COVERED

Information regarding this review was searched in PubMed until August 2010. Vitamin E, paraaminobenzoate and colchicine are sparingly employed oral medical therapies. Intralesional injections as a minimally invasive therapy for PD includes injection with verapamil, interferon-α-2b, and collagenase. Men suffering with PD who have significant penile deformity precluding successful coitus can be appraised for surgical correction. Surgery is considered the gold standard and includes plication, incision and grafting- or penile-prosthesis-related procedures.

EXPERT OPINION

This paper provides a broad overview of the subject of PD, available nonsurgical options and surgical approaches that will aid in the routine clinical diagnosis and management of PD. Increased public and medical awareness of PD prevalence, presentation, diagnosis and treatment options will serve well the large population of men who suffer in silence with this common condition.

Reversion of penile fibrosis: Current information and a new horizon

Ageing has a detrimental effect on cavernous tissue and the tunica albuginea of the penis. Furthermore, atherosclerosis of the penile vessels that occurs with ageing causes a decrease in penile oxygen tension. A reduction in smooth muscle cells (SMCs) was shown in relation to diminution of oxygen tension. Chronic ischaemia is therefore not only associated with fibrosis but also with nitric oxide-cyclic guanosine monophosphate reduction. The sensitivity of the α-adrenoceptors on the SMCs increases with ageing. The decrease in penile elasticity and compliance are explained by the changes in the ratio of penile collagen that occur with ageing. Contradictory to the view that testosterone is only necessary for sexual desire, numerous recent studies showed that androgen deprivation produces penile tissue atrophy, alterations in dorsal nerve structure, alterations in endothelial morphology, reduction in trabecular SM content, increase in deposition of extracellular matrix and accumulation of fat-containing cells (adipocytes) in the subtunical region of corpus cavernosum. The aim of the current review is to shed some light on the underlying aetiology of corporal fibrosis especially ageing, cavernous nerve damage, androgen deprivation and tunical fibrosis. Ultimately I will address the proposed prevention of erectile dysfunction associated with penile fibrosis.

A self-reported long-term follow-up of patients operated with either shortening techniques or a TachoSil grafting procedure

The aim of this article is to analyse the long-term results of different surgical techniques for correction of penile deviations in Peyronie's disease. Patients who underwent surgery for a penile deviation in Peyronie's disease between 1997 and 2007 were included into this study. Cases were retrospectively analysed by chart review. The current situation was evaluated by a 16-item standardized questionnaire addressing penile straightness, sensation, length, sexual function and satisfaction. Ninety patients were contacted with a return rate of 75 (83%) evaluable questionnaires. Thirty-two patients were operated by shortening techniques (STs) with either Schroeder-Essed (n=16) or Nesbit (n=16). Forty-three were operated by a plaque in-/excision and defect covering by TachoSil method (TM). Both groups were similar regarding age (ST 56 years, TM 57 years), comorbidities, mean preoperative erection hardness score (EHS; 3.1 ST, 3.4 TM) and time of follow-up (total mean, 63 months). Preoperatively ST patients had significantly less plaques (P<0.05) and a lower deviation angle in comparison to TM patients (ST 56° versus TM 74°; P< 0.001). Still TM patients reported slightly better straightening results, but a significantly lower mean EHS (ST 3.3 versus TM 2.6; P<0.001) during the follow-up. Satisfaction rates were similar in both groups. In conclusion, both techniques revealed to be safe and sustainable successful in penile straightening with better functional outcome of patients operated by STs.

p53-Associated Parkin-like cytoplasmic protein (Parc) short-interfering RNA (siRNA) alters p53 location and biology of Peyronie's disease fibroblasts

OBJECTIVE • To evaluate the impact of p53-associated Parkin-like cytoplasmic protein (Parc) short-interfering RNA (siRNA) on the location of p53 as well as the biology of Peyronie's disease (PD) plaque-derived fibroblasts after Parc knockdown. PATIENTS AND METHODS • Plaque tissue was excised from men with stable PD undergoing penile reconstructive surgery and used to produce cultured PD plaque-derived fibroblasts. • Immunofluorescence (IF) and reverse transcription-polymerase chain reaction (RT-PCR) were then used to define the location of p53 and Parc before and after siRNA. • Nuclear fractionation studies were used to assess the chronology of translocation of p53 from cytoplasm to nucleus on Parc knockdown. • The terminal transferase dUTP Nick end labelling (TUNEL) assay was used to assess the apoptotic indices of the PD fibroblasts after Parc knockdown. RESULTS • IF and PCR showed high cytoplasmic levels of p53 and Parc before siRNA. On IF, there was little or no p53 present within the nucleus before Parc knockdown. • After Parc siRNA, IF showed translocation of p53 to the fibroblast nucleus, while Parc levels dropped significantly, but what Parc remained was confined to the cytoplasm with none present in the nucleus. • Nuclear fractionation studies using RT-PCR confirmed this translocation phenomenon and showed the chronology of the event. All p53 had moved from the cytoplasm to the nucleus within 16 h of Parc siRNA. • On TUNEL assay, apoptotic indices increased dramatically after Parc siRNA. CONCLUSIONS • These data prove that Parc is a cytoplasmic anchor for p53 in PD plaque-derived fibroblasts and may be the primary cause of the stabilization and defunctionalization of p53 in these cells. • These findings support Parc as a novel target for PD pharmacotherapy, perhaps using human siRNA technologies once commercially available.

The management of Peyronie's disease: evidence-based 2010 guidelines

INTRODUCTION

The field of Peyronie's disease is evolving and there is need for a state-of-the-art information in this area.

AIM

To develop an evidence-based state-of-the-art consensus report on the management of Peyronie's disease.

METHODS

To provide state-of-the-art knowledge regarding the prevalence, etiology, medical and surgical management of Peyronie's Disease, representing the opinion of leading experts developed in a consensus process over a 2-year period.

MAIN OUTCOME MEASURES

Expert opinion was based on grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.

CONCLUSIONS

The real etiology of Peyronie's disease and the mechanisms of formation of the plaque still remain obscure. Although conservative management is obtaining a progressively larger consensus among the experts, surgical correction still remains the mainstay treatment for this condition.

Pluripotency genes overexpressed in primate embryonic stem cells are localized on homologues of human chromosomes 16, 17, 19, and X

While human embryonic stem cells (hESCs) are predisposed toward chromosomal aneploidities on 12, 17, 20, and X, rendering them susceptible to transformation, the specific genes expressed are not yet known. Here, by identifying the genes overexpressed in pluripotent rhesus ESCs (nhpESCs) and comparing them both to their genetically identical differentiated progeny (teratoma fibroblasts) and to genetically related differentiated parental cells (parental skin fibroblasts from whom gametes were used for ESC derivation), we find that some of those overexpressed genes in nhpESCs cluster preferentially on rhesus chromosomes 16, 19, 20, and X, homologues of human chromosomes 17, 19, 16, and X, respectively. Differentiated parental skin fibroblasts display gene expression profiles closer to nhpESC profiles than to teratoma cells, which are genetically identical to the pluripotent nhpESCs. Twenty over- and underexpressed pluripotency modulators, some implicated in neurogenesis, have been identified. The overexpression of some of these genes discovered using pedigreed nhpESCs derived from prime embryos generated by fertile primates, which is impossible to perform with the anonymously donated clinically discarded embryos from which hESCs are derived, independently confirms the importance of chromosome 17 and X regions in pluripotency and suggests specific candidates for targeting differentiation and transformation decisions.

Differential gene expression analysis of subcutaneous fat, fascia, and skin overlying a Dupuytren's disease nodule in comparison to control tissue

Dupuytren's disease (DD) is a benign fibroproliferative tumor with an unknown etiology and high recurrence postsurgery. Several observations suggest the possible involvement of skin overlying nodule (SON) and the subcutaneous fat in the pathogenesis of DD. This study aims to (1) compare the gene expression levels of SON and subcutaneous fat in DD and normal subjects and (2) to compare transverse palmar fascia (Skoog's fibers) from DD patients as internal control tissue, with palmar fascia (transverse carpal ligament) from patients undergoing carpal tunnel release as external control. Skin, fat, and fascia were obtained from five DD patients of Caucasian origin (age = 66 +/- 14) and from five control subjects (age = 57 +/- 19) undergoing carpal tunnel release. Total ribonucleic acids was extracted from each sample and used for complementary deoxyribonucleic acid synthesis. Real-time quantitative polymerase chain reaction was used to assess the gene expression levels of six candidate genes: A disintegrin and metalloproteinase domain (ADAM12), aldehyde dehydrogenase 1 family member A1 (ALDH1A1), iroquois homeoboxprotein 6 (IRX6), periostin, osteoblast specific factor, proteoglycan 4, and tenascin C. Using independent t test, ADAM12, ALDH1A1, and IRX6 expression levels in DD fats were significantly (p < 0.05) higher than those in the controls. There is no significant difference in the gene expression levels of all six genes when comparing disease and control fascia and skin. Interestingly, ADAM12 up-regulation has also been observed in several other fibrotic and proliferative disorders. In conclusion, this study demonstrates potential roles for subcutaneous fat in DD pathogenesis as well as supports the use of transverse palmar fascia as appropriate control tissues in DD research.

Experimental models of Peyronie's disease. Implications for new therapies

INTRODUCTION

Despite its high prevalence and impact on the quality of life of patients, and that it is an excellent model for the study of fibrotic processes, Peyronie's disease (PD) is an orphan disease in biomedical research. The development of animal and cell culture models has advanced substantially the understanding of its molecular and cellular pathology and the proposal of new therapies.

AIM

To review the literature pertaining to the use of these models for the study of PD.

METHODS

PubMed search conducted from the first report of an animal model for PD.

RESULTS

This model, based on the finding that transforming growth factor beta1 (TGF beta 1) is overexpressed in the PD plaque, consists on the injection of TGF beta 1 into the tunica albuginea of the rat. This leads to a PD-like plaque retaining many of the histological and biochemical features of human PD. Another rat model, based on the hypothesis that the PD plaque arises from trauma to the penis, causing fibrinogen extravasation that initiates as fibrin a fibrotic response, consists on injection of fibrin into the tunica. The cell culture model is based on the demonstration that myofibroblasts are abundant in the human PD plaque.

CONCLUSIONS

These models have: (i) clarified the role of microtrauma, myofibroblasts, and oxidative stress in plaque development; (ii) demonstrated that this tissue is under sustained turnover by fibrotic and antifibrotic mechanisms; (iii) showed the interplay of collagenolytic and fibrinolytic systems and their inhibitors; (iv) detected an endogenous antifibrotic process consisting of the expression of inducible nitric oxide synthase that counteracts oxidative stress, collagen synthesis, and myofibroblast generation; (v) characterized the antifibrotic effects of chronic treatment with phosphodiesterase type 5 (PDE5) inhibitors; (vi) discovered the cytogenetic instability of PD cells and alterations in their gene expression; and (vii) detected stem cells in the tunica albuginea with a potential role in fibrosis and ossification.

Long-Term Continuous Treatment with Sildenafil Ameliorates Aging-Related Erectile Dysfunction and the Underlying Corporal Fibrosis in the Rat1

Aging-related erectile dysfunction is characterized by a loss of smooth muscle cells (SMCs) and fibrosis in the corpora cavernosa, and functionally by corporal veno-occlusive dysfunction (CVOD). Phosphodiesterase 5 (PDE5A) inhibitors, in part via upregulating inducible nitric oxide synthase (NOS2A), have antifibrotic properties in penile tissues. We aimed to determine whether in the aged rat the chronic long-term treatment with sildenafil ameliorates corporal SMC loss and fibrosis, stimulates NOS2A induction, and corrects the associated CVOD. Aged male rats (20 mo old) received sildenafil in their drinking water (20 mg/kg per day) or plain water for 45 days, and untreated young rats (5 mo old) served as controls (n = 8 per group). CVOD was assessed by dynamic infusion cavernosometry (DIC). Collagen:SMC (Masson trichrome) and collagen III:I (picrosirius red) ratios, SMC content (alpha-smooth muscle actin [ACTA2]), cell proliferation (proliferating nuclear antigen [PCNA]), apoptotic death (TUNEL), and NOS2A induction were measured by histochemistry and immunohistochemistry followed by quantitative image analysis. Collagen content was determined by hydroxyproline assay, and transforming growth factor beta-1 (TGFB1); xanthine oxidoreductase (XDH); ACTA2; NOS2A; and the Rho kinase inhibitor protein tyrosine phosphatase, nonreceptor type 11 (PTPN11), and activator, VAV, were measured by quantitative Western blot. In the aged rats treated with sildenafil, the erectile response by DIC was normalized, and the corporal SMC:collagen ratio and SMC number were increased. In addition, sildenafil reduced the corporal collagen content without affecting the collagen III:I ratio, increased the PCNA:apoptosis ratio, and stimulated NOS2A induction, although there was no effect on XDH, TGFB1, PTPN11, or VAV levels. These data show that long-term PDE5A treatment corrected CVOD in the aged rat and partially reversed the aging-related fibrosis and loss of SMC in the corpora cavernosa without affecting TGFB1 or PTPN11 levels, which are markers of oxidative stress. It may be speculated that similar effects may be achieved with this paradigm in men.

Increased vaginal oxidative stress, apoptosis, and inducible nitric oxide synthase in a diabetic rat model: implications for vaginal fibrosis

OBJECTIVE

To determine whether vaginal fibrosis occurs in diabetic animals and is associated with oxidative stress and cell death and with the expression of inducible nitric oxide synthase (iNOS), as a putative antifibrotic mechanism.

DESIGN

Research experimental project.

SETTING

University research laboratory.

ANIMAL(S)

Female Wistar rats.

INTERVENTION(S)

Female rats were injected with streptozotocin or saline and killed at 3 months. The vaginas were excised and processed for paraffin-embedded sections (n = 6 per group) or were frozen for biochemical and molecular biology procedures.

MAIN OUTCOME MEASURE(S)

Immunohistochemistry and quantitative image analysis were applied to tissue sections to measure alpha-smooth muscle actin, transforming growth factor beta1, plasminogen activator inhibitor, NOS isoforms, Cu/Zn superoxide dismutase, apoptotic index, and nitrotyrosine. Xanthine dehydrogenase, reactive oxygen species (ROS), and hydroxyproline were measured in fresh vaginal tissue (n = 5 per group). Reactive oxygen species also were determined in blood.

RESULT(S)

Diabetes was associated with vaginal fibrosis, as evidenced by increased collagen, transforming growth factor beta1, plasminogen activator inhibitor, and apoptosis, and by decreased alpha-smooth muscle actin. The increment of ROS and the reduction of superoxide dismutase indicated oxidative stress in diabetic tissue, accompanied by iNOS induction and increased nitric oxide-ROS reaction.

CONCLUSION(S)

Diabetes in the rat causes oxidative stress and fibrosis in the vagina, which may be compensated partially by iNOS induction to reduce ROS.

Pioglitazone prevents corporal veno-occlusive dysfunction in a rat model of type 2 diabetes mellitus

OBJECTIVE

To determine whether corporal veno-occlusive dysfunction (CVOD), corporal smooth muscle (SM) loss, fibrosis and oxidative stress occur in a rat model of type 2 diabetes, and whether these are counteracted by pioglitazone, as pioglitazone is vasculoprotective, and corporal SM is an extension of arterial SM.

MATERIALS AND METHODS

Male obese Zucker fa/fa rats were fed chow containing 0%, 0.001% or 0.02% pioglitazone for 2 or 5 months, using untreated lean Zucker and Fischer 344 rats as controls. Functional changes were determined by dynamic-infusion cavernosometry. Histological changes were assessed by histochemistry and immunohistochemistry followed by quantitative image analysis and/or quantitative Western blot.

RESULTS

CVOD was detected at 4.5 months of diabetes, accompanied by a lower corporal SM/collagen ratio, and increases in collagen, collagen III/I ratio, apoptotic index, and systemic and tissue oxidative stress. In the short-term treatment, high-dose pioglitazone normalized glycaemia and ameliorated fibrosis and oxidative stress, but induced CVOD, whereas the effects with the low dose were not significant. However, low-dose pioglitazone for 5 months corrected all alterations.

CONCLUSION

Type 2 diabetes in Zucker fa/fa rats was associated with penile corporal fibrosis, oxidative stress, and CVOD, which were ameliorated by long-term low-dose pioglitazone, suggesting that this drug might protect the SM, independently from its antidiabetic effect.