Peyronie's Disease

Urologists' Perceptions and Practice Patterns in Peyronie's Disease: A Korean Nationwide Survey Including Patient Satisfaction

PURPOSE

A nationwide survey was conducted of Korean urologists to illustrate physicians' perceptions and real practical patterns regarding Peyronie disease (PD).

MATERIALS AND METHODS

A specially designed questionnaire exploring practice characteristics and attitudes regarding PD, as well as patient satisfaction with each treatment modality, was e-mailed to 2,421 randomly selected urologists.

RESULTS

Responses were received from 385 practicing urologists (15.9%) with a median time after certification as an urologist of 12 years. Regarding the natural course, 87% of respondents believed that PD is a progressive disease, and 82% replied that spontaneous healing in PD occurred in fewer than 20% of patients. Regarding diagnosis of PD, the methods used were, in order, history taking with physical examination (98%), International Index of Erectile Function questionnaires (40%), intracavernous injection and stimulation (35%), and duplex sonography (28%). Vitamin E was most preferred as an initial medical management (80.2%), followed by phosphodiesterase-5 inhibitors (27.4%) and Potaba (aminobenzoate potassium, 20.1%). For urologists who administered intralesional injection, the injected agent was, in order, corticosteroid (72.2%), verapamil (45.1%), and interferon (3.2%). The most frequently performed surgical procedure was plication (84.1%), followed by excision and graft (42.9%) and penile prosthesis implantation (14.2%). Among the most popular treatments in each modality, the urologists' perceptions regarding the suitability of treatment and patient satisfaction were significantly different, favoring plication surgery.

CONCLUSIONS

The practice pattern of urologists depicted in this survey is in line with currently available Western guidelines, which indicates the need for development of further local guidelines based on solid clinical data.

Understanding the course of Peyronie's disease

AIMS

To correct common misconceptions about Peyronie's disease (PD) that present obstacles to early recognition and treatment.

METHODS

The prevalence, natural disease course, psychosocial effects and treatment considerations for patients with PD were reviewed.

RESULTS

Studies over the past decade have shown that the prevalence of PD may be higher (up to 20%) than previously thought. PD can lead to emotional and relationship distress. Nearly 10% of men who present with PD are younger than 40. Both younger age and comorbid vascular disease have been associated with more severe and progressive PD. In the majority of patients, symptoms will either deteriorate or remain stable. PD is often associated with erectile dysfunction (ED). Effective, minimally invasive treatments used early in the disease course include unapproved and/or investigational intralesional injection therapy with verapamil, interferon (IFN) α-2b, or collagenase clostridium histolyticum (CCH). Surgical intervention is considered in patients with ED and/or penile deformity that impairs sexual functioning; however, preoperative discussion of appropriate expectations is important.

DISCUSSION

The availability of effective minimally invasive and surgical therapies for PD suggests that active management should be considered over a 'wait-and-see' approach.

CONCLUSION

Providing early intervention and improved education/awareness of PD as a chronic and progressive disorder may result in improved physical and psychosocial outcomes for PD patients. As general practitioners are often the first contact for men with PD, they are well positioned to recognise symptoms early and promptly refer patients for further evaluation and treatment.

Clinical efficacy, safety and tolerability of collagenase clostridium histolyticum for the treatment of peyronie disease in 2 large double-blind, randomized, placebo controlled phase 3 studies

PURPOSE

IMPRESS (Investigation for Maximal Peyronie's Reduction Efficacy and Safety Studies) I and II examined the clinical efficacy and safety of collagenase Clostridium histolyticum intralesional injections in subjects with Peyronie disease. Co-primary outcomes in these identical phase 3 randomized, double-blind, placebo controlled studies included the percent change in the penile curvature abnormality and the change in the Peyronie disease questionnaire symptom bother score from baseline to 52 weeks.

MATERIALS AND METHODS

IMPRESS I and II examined collagenase C. histolyticum intralesional injections in 417 and 415 subjects, respectively, through a maximum of 4 treatment cycles, each separated by 6 weeks. Men received up to 8 injections of 0.58 mg collagenase C. histolyticum, that is 2 injections per cycle separated by approximately 24 to 72 hours with the second injection of each followed 24 to 72 hours later by penile plaque modeling. Men were stratified by baseline penile curvature (30 to 60 vs 61 to 90 degrees) and randomized to collagenase C. histolyticum or placebo 2:1 in favor of the former.

RESULTS

Post hoc meta-analysis of IMPRESS I and II data revealed that men treated with collagenase C. histolyticum showed a mean 34% improvement in penile curvature, representing a mean ± SD -17.0 ± 14.8 degree change per subject, compared with a mean 18.2% improvement in placebo treated men, representing a mean -9.3 ± 13.6 degree change per subject (p <0.0001). The mean change in Peyronie disease symptom bother score was significantly improved in treated men vs men on placebo (-2.8 ± 3.8 vs -1.8 ± 3.5, p = 0.0037). Three serious adverse events (corporeal rupture) were surgically repaired.

CONCLUSIONS

IMPRESS I and II support the clinical efficacy and safety of collagenase C. histolyticum for the physical and psychological aspects of Peyronie disease.

Current and emerging treatment options for Peyronie's disease

Peyronie’s disease (PD) is a condition of the penis, characterized by the presence of localized fibrotic plaque in the tunica albuginea. PD is not an uncommon disorder, with recent epidemiologic studies documenting a prevalence of 3–9% of adult men affected. The actual prevalence of PD may be even higher. It is often associated with penile pain, anatomical deformities in the erect penis, and difficulty with intromission. As the definitive pathophysiology of PD has not been completely elucidated, further basic research is required to make progress in the understanding of this enigmatic condition. Similarly, research on effective therapies is limited. Currently, nonsurgical treatments are used for those men who are in the acute stage of PD, whereas surgical options are reserved for men with established PD who cannot successfully penetrate. Intralesional treatments are growing in clinical popularity as a minimally invasive approach in the initial treatment of PD. A surgical approach should be considered when men with PD do not respond to conservative, medical, or minimally invasive therapies for approximately 1 year and cannot have satisfactory sexual intercourse. As scientific breakthroughs in the understanding of the mechanisms of this disease process evolve, novel treatments for the many men suffering with PD are anticipated.

Surgery for Peyronie's disease

Peyronie's disease (PD) is most simply referred to as a fibrotic wound-healing disorder of the tunica albuginea. It is both a physically and psychologically devastating disorder that causes penile deformity, curvature, hinging, narrowing and shortening, which may compromise sexual function. Although a variety of non-surgical treatments have been suggested, none to date offer a reliable and effective correction of the penile deformity. As a result, surgery remains the gold standard treatment option, offering the most rapid and reliable treatment which will be the focus of this article. We review the preoperative evaluation, surgical algorithm, graft materials and postoperative management of PD. Outcomes for tunical shortening, tunical lengthening and penile prosthesis placement for penile straightening are reviewed. Tunica albuginea plication is the preferred method of straightening for men with adequate rigidity and less severe disease defined as curvature less than 70° without narrowing/hinging. Men who have more severe, complex deformity, but maintain strong preoperative erectile function should be considered candidates for straightening with plaque incision or partial excision and grafting. Finally, for those men who have inadequate rigidity and PD, penile prosthesis placement with straightening is the best approach to address both problems.

Phase 2b study of the clinical efficacy and safety of collagenase Clostridium histolyticum in patients with Peyronie disease

PURPOSE

Collagenase Clostridium histolyticum is an investigational nonsurgical treatment for Peyronie disease. In this phase 2b, double-blind, randomized, placebo controlled study we determined the safety and efficacy of collagenase C. histolyticum and assessed a patient reported outcome questionnaire.

MATERIALS AND METHODS

A total of 147 subjects were randomized into 4 groups to receive collagenase C. histolyticum or placebo (3:1) with or without penile plaque modeling (1:1). Per treatment cycle 2 injections of collagenase C. histolyticum (0.58 mg) were given 24 to 72 hours apart. Subjects received up to 3 cycles at 6-week intervals. When designated, investigator modeling was done 24 to 72 hours after the second injection of each cycle. We evaluated penile curvature by goniometer measurement, patient reported outcomes and adverse event profiles.

RESULTS

After collagenase C. histolyticum treatment significant improvements in penile curvature (29.7% vs 11.0%, p=0.001) and patient reported outcome symptom bother scores (p=0.05) were observed compared to placebo. In modeled subjects 32.4% improvement in penile curvature was observed in those on collagenase C. histolyticum compared to 2.5% worsening of curvature in those on placebo (p<0.001). Those treated with collagenase C. histolyticum who underwent modeling also showed improved Peyronie disease symptom bother scores (p=0.004). In subjects without modeling there were minimal differences between the active and placebo cohorts. Most adverse events in the collagenase C. histolyticum group occurred at the injection site and were mild or moderate in severity. No treatment related serious adverse events were reported.

CONCLUSIONS

Collagenase C. histolyticum treatment was well tolerated. We noted significant improvement in penile curvature and patient reported outcome symptom bother scores, suggesting that this may be a safe, nonsurgical alternative for Peyronie disease.

Drugs of the future for Peyronie's disease

With the increasing awareness of Peyronie's disease (PD), the interest in new concept medications to treat the disorder is escalating. Profibrogenic factors such as transforming growth factor (TGF)-beta1, endothelin (ET-1), connective tissue growth factor (CTGF), angiotensin (Ang) II and platelet derived growth factor (PDGF), all appear to be involved in the pathogenesis of PD. β-Thymosins, pirfenidone, nitric oxide (NO) donors, phosphodiesterase (PDE)-5 inhibitors, matrix metalloproteinases (MMPs)/anti-tissue inhibitor of metalloproteinases (TIMP)-1 reduce collagen synthesis, while decorin, follistatin, and Smad 7 exert antifibrotic effects; all have been proposed for the treatment of PD. Alternative and/or novel approaches for the treatment of PD are needed in part because of the recognized multifactorial etiology of this complex disorder. A comprehensive approach for translating available experimental information into clinically effective drug trials for the treatment of PD is needed. We propose a multi-faceted approach for drug development to generate novel drug products for the treatment of PD.

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.

Human acellular matrix graft of tunica albuginea for penile reconstruction

INTRODUCTION

Penile curvature is one of the most common male conditions, affecting nearly 10% of men, and can impair sexual intercourse. Tunica albuginea (hTA) plays a key role in penile curvature, and reconstructive procedures may be necessary for its substitution. Although several grafts have been proposed for hTA repair, the ideal graft is not yet available.

AIM

The aim of this article is to evaluate a new human tunica albuginea acellular matrix (hTAAM) as potential graft for penile reconstructive procedures.

METHODS

Twelve penises were obtained during sex reassignment surgeries from male-to-female transsexual patients. After dissection, hTAs were assigned into two groups according to the decellularization methods: polyethylene glycol (PEG) 1000 method following ultraviolet-C radiation, and Triton X-100 modified method.

MAIN OUTCOME MEASURES

Structural analyses were assessed by hematoxilin and eosin, Masson's trichrome, Weigert's, and picrosirius-polarization staining methods. Total protein, total glycosaminoglycan (GAG), and nucleic acid (DNA and RNA) concentrations were assessed by specific biochemical analyses. Uniaxial strength tests were performed to evaluate biomechanical properties.

RESULTS

All hTAAMs presented no nuclear or cellular remnants. Total protein concentration was significantly higher in PEG 1000 hTAAM. Despite GAG concentration decreased significantly in hTAAM, Triton X-100 hTAAM retained the highest GAG concentration (1.0 ± 0.42 µg HexUr/mg dry tissue, P > 0.05). All decellularization methods were efficacious to remove nucleic acids. The maximal break point presented no difference between hTA and hTAAM groups (P > 0.05).

CONCLUSIONS

PEG 1000 and Triton X-100 decellularization methods provide equally successful hTAAMs, preserving original structural and biochemical properties.

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.

The relationship between androgens, regulators of collagen metabolism, and Peyronie's disease: a case control study

INTRODUCTION

Changes in collagen metabolism have been postulated to play a pivotal role in the pathogenesis of Peyronie's Disease (PD). Androgens such as dehydroepiandrosterone sulfate (DHEA-S) and testosterone influence collagen metabolism by modulating the activity of matrix metalloproteases (MMP) and tissue inhibitors of metalloproteases (TIMP).

AIM

The aim of this study was to evaluate the interrelationship between androgens (DHEA-S and testosterone), key regulators of collagen metabolism such as insulin-like growth factor (IGF) 1 and IGF Binding Protein 3 (IGF-BP3), the MMP/TIMP system, and PD.

METHODS

Age matched PD patients (14) and healthy men (10) who acted as controls were recruited. Blood samples were collected from all subjects in the early morning hours after an overnight fast.

MAIN OUTCOME MEASURES

Serum levels of testosterone, sex hormone binding globulin, DHEA-S, 3-α-androstanediol glucuronide, pro-MMP-1, MMP-1, MMP-2, TIMP-1, TIMP-2, IGF-1 and IGF-BP3 were measured in both groups. Statistical methods included univariate, bivariate, and multivariate regression models.

RESULTS

Levels of DHEA-S (114.5 vs. 169.5 µg/dL; p = 0.03), IGF-BP3 (2.96 vs. 3.79 µg/mL; p = 0.01), and TIMP-1 (173.1 vs. 195 ng/mL; p = 0.01) were significantly lower in PD patients. In contrast, the level of TIMP-2 (102 vs. 85 ng/mL; p = 0.001) was significantly lower in the control group. Using stepwise regression analysis, only TIMP-2 (p < 0.001) and DHEA-S (p = 0.04) were significantly related to PD in the final model (R(2) = 0.63). TIMP-1 and DHEA-S (r = 0.55, p < 0.05) were positively correlated in the PD group, whereas IGF-1 and testosterone (r = -0.54, p < 0.05), and IGF-BP3 and testosterone (r = -0.68, p < 0.05) were negatively correlated in PD patients.

CONCLUSIONS

Our findings suggest that decreased levels of adrenal androgens may be implicated in the pathogenesis of PD. The mechanism and clinical relevance of this observation remain to be established.

[Symptomatic approach to chronic penile pain]

OBJECTIVE

To describe the aetiologies of non-cancer chronic penile pain.

MATERIAL AND METHODS

A review of the literature was performed by searching the Medline database (National Library of Medicine). Search terms were either medical subject heading (MeSH) keywords (pain, penis, penile diseases) or terms derived from the title or abstract. Search terms were used alone or in combinations by using the "AND" operator. The literature search was conducted from 1990 to the present time.

RESULTS

Clinical interview and physical examination are essential elements of the assessment of chronic penile pain. The aetiologies of chronic penile pain include local diseases, referred pain, neuropathic pain, psychological or psychiatric disorders and penile pain syndrome. Neuropathic pain is related to compression of the dorsal nerve of the penis, derived from the pudendal nerve, at the inferior border of the pubis. This nerve compression syndrome, often associated with cycling, can also be responsible for decreased sensitivity of the glans and penis, genital paraesthesia (numbness) and sometimes erectile dysfunction. Penile pain syndrome, defined as pain located in the penis, but not due to an urethral cause, documented infection or another clinically apparent disease, is a diagnosis of exclusion.

CONCLUSION

The diagnosis of non-cancer chronic penile pain is essentially clinical. Compression of the dorsal nerve of the penis is part of the context of penile pain syndrome, corresponding to a diagnosis of exclusion.

Trans-corporal incision of Peyronie's plaques

INTRODUCTION

Patients presenting with Peyronie's disease (PD) curvature and erectile dysfunction (ED) can achieve straightening and rigidity through penile prosthesis implantation and manual modeling and, if necessary, a relaxing tunical incision with or without grafting. Unfortunately, this maneuver will not correct PD-induced shortening. In addition, incision and grafting after the prosthesis has already been implanted adds to operative time and risk, and may indicate mobilization of the neurovascular bundle and, possibly, a secondary skin incision.

AIM

This work describes trans-corporal incision (TCI), a minimally invasive endoscopic approach for plaque incision from within the corpora cavernosa, restoring straightness and length to the penis, before calibration of the corpora cavernosa, allowing implantation of a longer prosthesis in a straight penis, with neither mobilizing the neurovascular bundle nor a secondary incision.

METHODS

Sixteen patients with PD deformity and refractory ED were operated upon. Intra-operative artificial erection demonstrated the deformity. Through a penoscrotal incision, the corpora were dilated. TCI was performed to incise Peyronie's plaques at the point of maximum deformity. Artificial erection was re-induced and correction of curvature evaluated. Length was measured before and after TCI. Implantation proceeded as usual.

MAIN OUTCOME MEASURES

Penile straightness and length.

RESULTS

Following implantation, the penis was straight in all cases. Pre-TCI length of the corpora was unequal on either side. Post-TCI, both corpora were of equal length with an average increase of 2.5 cm (11.9%) on the right side and 1.9 (9.1%) on the left.

CONCLUSION

TCI; corporoscopic incision of Peyronie's plaques upon implantation of penile prosthesis is a minimally invasive approach that restores both straightness and length to patients with PD and ED, with neither mobilization of the neurovascular bundle nor plaque incision and grafting.

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.

Are sonographic characteristics associated with progression to surgery in men with Peyronie's disease?

PURPOSE

Traditionally, diagnosis and treatment plans for Peyronie's disease have been based on history and physical examination. Penile ultrasound provides rapid, anatomical information to establish disease severity, and to monitor progression and response to medical therapy. We determined the relationship between ultrasound characteristics and progression to surgical intervention in men with Peyronie's disease.

MATERIALS AND METHODS

We conducted a retrospective cohort study of 518 patients with Peyronie's disease. Patients completed a Peyronie's disease specific questionnaire detailing medical history, health related behaviors and Peyronie's disease characteristics, and underwent sonographic evaluation of the penis. Measurements of subtunical calcifications, septal fibrosis, tunical thickening (tunica thickness greater than 2 mm) and intracavernous fibrosis were made. Progression to surgery was determined from the medical record.

RESULTS

In this cohort (mean patient age 53.8 years, range 20 to 78) 31% of patients had calcifications, 50% had tunical thickening, 20% had septal fibrosis and 15% had intracavernous fibrosis. Overall 25% of the cohort progressed to surgical intervention after an average followup of 1.25 years (range 0 to 7.6). Patients who underwent surgery were more likely to have subtunical calcifications present at the first clinic visit (OR 1.75, 95% CI 1.16-2.62). No other sonographic characteristics were associated with progression to surgery. After adjustment for age, marital status, degree of curvature, additional penile deformity, difficulty with penetration, ability to have intercourse and prior treatment for Peyronie's disease, calcifications were strongly associated with progression to surgery (OR 2.75, 95% CI 1.25-3.45).

CONCLUSIONS

In a large cohort of patients with Peyronie's disease the presence of sonographically detected sub-tunical calcifications during the initial office evaluation was independently associated with subsequent surgical intervention.

[Reconstructive surgery of penile deformities and tissue deficiencies]

Penile deformities and tissue deficiencies can disturb sexual intercourse or make it impossible. The aim of the study is to summarize the different diseases according to their clinical appearance and pathological processes and to review operative methods and personal experiences. Surgical treatment of hypo- and epispadias is usually performed in childhood, but curvatures after unsuccessful operation can demand the reconstruction of urethra, skin and corpora cavernosa eventually. Peyronie's disease and curvature after penile fracture desire the reconstruction of tunica albuginea. Plaque surgery used to be performed with dermal, tunica vaginalis or venous grafts, but best results are obtained by shortening procedure on the contralateral side according to the Heinecke-Mikulitz principle. Tissue deficiencies and curvatures were observed after necrotic inflammatory processes, like Fournier's gangrene or chronic dermatitis. Skin defects were cured by flaps and grafts. Abscesses of penis, severe tissue defects and also curvatures were observed after intracavernous injection in cases of erectile dysfunction. Possibilities of reconstruction seem to be very poor. Oil granuloma of penis presents a new task for penile reconstruction. The best results of skin replacement were achieved by temporary embedding of the penis in scrotum.

Benign Diseases and Neoplasms of the Penis

This article provides comprehensive review of benign diseases and neoplastic conditions of the penis. It describes and provides representative images of clinical, key pathologic features and ancillary techniques to aid in differential diagnoses. It examines these diseases from the epidemiologic standpoint, looks at environmental and genetic factors, and outlines the new histologic entities for penile neoplasms with distinct outcomes and clinical behavior that have been proposed in recent years.

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.