Stem cells: novel players in the treatment of erectile dysfunction

Princeton IV consensus guidelines: PDE5 inhibitors and cardiac health

BACKGROUND

In 1999, 1 year after the approval of the first oral phosphodiesterase type 5 (PDE5) inhibitor for the treatment of erectile dysfunction (ED), the first Princeton Consensus Conference was held to address the clinical management of men with ED who also had cardiovascular disease. These issues were readdressed in the second and third conferences. In the 13 years since the last Princeton Consensus Conference, the experience with PDE5 inhibitors is more robust, and recent new data have emerged regarding not only safety and drug-drug interactions, but also a potential cardioprotective effect of these drugs.

AIM

In March 2023, an interdisciplinary group of scientists and practitioners met for the fourth Princeton Consensus Guidelines at the Huntington Medical Research Institutes in Pasadena, California, to readdress the cardiovascular workup of men presenting with ED as well as the approach to treatment of ED in men with known cardiovascular disease.

METHOD

A series of lectures from experts in the field followed by Delphi-type discussions were developed to reach consensus.

OUTCOMES

Consensus was reached regarding a number of issues related to erectile dysfunction and the interaction with cardiovascular health and phosphodiesterase-5 inhibitors.

RESULTS

An algorithm based on recent recommendations of the American College of Cardiology and American Heart Association, including the use of computed tomography coronary artery calcium scoring, was integrated into the evaluation of men presenting with ED. Additionally, the issue of nitrate use was further considered in an algorithm regarding the treatment of ED patients with coronary artery disease. Other topics included the psychological effect of ED and the benefits of treating it; the mechanism of action of the PDE5 inhibitors; drug-drug interactions; optimizing use of a PDE5 inhibitors; rare adverse events; potential cardiovascular benefits observed in recent retrospective studies; adulteration of dietary supplements with PDE5 inhibitors; the pros and cons of over-the-counter PDE5 inhibitors; non-PDE5 inhibitor therapy for ED including restorative therapies such as stem cells, platelet-rich plasma, and shock therapy; other non-PDE5 inhibitor therapies, including injection therapy and penile prostheses; the issue of safety and effectiveness of PDE5 inhibitors in women; and recommendations for future studies in the field of sexual dysfunction and PDE5 inhibitor use were discussed.

CLINICAL IMPLICATIONS

Algorithms and tables were developed to help guide the clinician in dealing with the interaction of ED and cardiovascular risk and disease.

STRENGTHS AND LIMITATIONS

Strengths include the expertise of the participants and consensus recommendations. Limitations included that participants were from the United States only for this particular meeting.

CONCLUSION

The issue of the intersection between cardiovascular health and sexual health remains an important topic with new studies suggesting the cardiovascular safety of PDE5 inhibitors.

Stem cell therapy for erectile dysfunction: a systematic review

INTRODUCTION

Erectile dysfunction (ED) is a common condition that negatively affects men's quality of life. It can have various causes, including psychological, vascular, and neurologic factors. Existing treatments for ED mainly focus on symptom relief rather than addressing the underlying cause. Stem cells (SCs) have shown potential as a therapeutic approach for ED due to their anti-inflammatory properties.

OBJECTIVES

This systematic review aims to assess the current status of trials and determine the potential impact of SCs on male sexual health.

METHODS

A comprehensive search strategy was employed to gather relevant articles from 6 electronic databases. The search included articles published until March 2023. The reference lists of articles were manually reviewed to identify additional studies of relevance. The eligibility criteria for inclusion in the analysis focused on clinical trials involving humans that evaluated the safety and efficacy of SC therapy for ED. Exclusion criteria encompassed case reports, case series, abstracts, reviews, and editorials, as well as studies involving animals or SC derivatives. Data extraction was performed via a standardized form with a focus on erectile outcomes.

RESULTS

A total of 2847 articles were initially identified; 18 were included in the final analysis. These studies involved 373 patients with ED and various underlying medical conditions. Multiple types of SC were utilized in the treatment of ED: mesenchymal SCs, placental matrix-derived mesenchymal SCs, mesenchymal SC-derived exosomes, adipose-derived SCs, bone marrow-derived mononuclear SCs, and umbilical cord blood SCs.

CONCLUSION

SC therapy shows promise as an innovative and safe treatment for organic ED. However, the lack of standardized techniques and controlled groups in many studies hampers the ability to evaluate and compare trials.

New Solutions for Old Problems: How Reproductive Tissue Engineering Has Been Revolutionizing Reproductive Medicine

Acquired disorders and congenital defects of the male and female reproductive systems can have profound impacts on patients, causing sexual and endocrine dysfunction and infertility, as well as psychosocial consequences that affect their self-esteem, identity, sexuality, and relationships. Reproductive tissue engineering (REPROTEN) is a promising approach to restore fertility and improve the quality of life of patients with reproductive disorders by developing, replacing, or regenerating cells, tissues, and organs from the reproductive and urinary systems. In this review, we explore the latest advancements in REPROTEN techniques and their applications for addressing degenerative conditions in male and female reproductive organs. We discuss current research and clinical outcomes and highlight the potential of 3D constructs utilizing biomaterials such as scaffolds, cells, and biologically active molecules. Our review offers a comprehensive guide for researchers and clinicians, providing insights into how to reestablish reproductive tissue structure and function using innovative surgical approaches and biomaterials. We highlight the benefits of REPROTEN for patients, including preservation of fertility and hormonal production, reconstruction of uterine and cervical structures, and restoration of sexual and urinary functions. Despite significant progress, REPROTEN still faces ethical and technical challenges that need to be addressed. Our review underscores the importance of continued research in this field to advance the development of effective and safe REPROTEN approaches for patients with reproductive disorders.

Introduction to stem cells

Stem cells have self-renewal capability and can proliferate and differentiate into a variety of functionally active cells that can serve in various tissues and organs. This review discusses the history, definition, and classification of stem cells. Human pluripotent stem cells (hPSCs) mainly include embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs). Embryonic stem cells are derived from the inner cell mass of the embryo. Induced pluripotent stem cells are derived from reprogramming somatic cells. Pluripotent stem cells have the ability to differentiate into cells derived from all three germ layers (endoderm, mesoderm, and ectoderm). Adult stem cells can be multipotent or unipotent and can produce tissue-specific terminally differentiated cells. Stem cells can be used in cell therapy to replace and regenerate damaged tissues or organs.

Stem Cell Therapy for Erectile Dysfunction: A Step towards a Future Treatment

Background: The improvement of absent or partial response in the medical treatment of erectile dysfunction (ED) has led to the development of minimally invasive new treatment modalities in the field of regenerative medicine. Methods: A literature review on stem cell therapy for the treatment of ED was performed. We searched for the terms "erectile dysfunction" and "stem cell therapy" in PubMed and Clinicaltrials.gov. Literature searching was conducted in English and included articles from 2010 to 2022. Results: New treatment modalities for ED involving stem cell therapy are not only conceived with a curative intent but also aim to avoid unnecessary adverse effects. Several sources of stem cells have been described, each with unique characteristics and potential applications, and different delivery methods have been explored. A limited number of interventional studies over the past recent years have provided evidence of a safety profile in their use and promising results for the treatment of ED, although there are not enough studies to generate an appropriate protocol, dose or cell lineage, or to determine a mechanism of action. Conclusions: Stem cell therapy is a novel treatment for ED with potential future applications. However, most urological societies agree that further research is required to conclusively prove its potential benefit.

Recent advances in stem cell therapy for erectile dysfunction: a narrative review

INTRODUCTION

While phosphodiesterase type 5 inhibitors (PDE5is) and others are used to treat Erectile dysfunction (ED), many patients are either unresponsive or resistant to it. Stem cell therapy (SCT) is a promising alternative approach. Numerous preclinical trials have demonstrated improved erectile function in animal models using SCT, although the number of clinical trials investigating SCT for men with ED is limited. Nonetheless, findings from human clinical trials suggest that SCT may be a useful treatment option.

AREAS COVERED

Biomedical literature, including PubMed, ClinicalTrials.gov, and European Union Clinical Trials Registry, were analyzed to summarize and synthesize information on stem cell therapy for ED in this narrative review. The achievements in preclinical and clinical evaluations are presented and critically analyzed.

EXPERT OPINION

SCT has demonstrated some benefits in improving erectile function, while further studies are urgently needed. Such studies would provide valuable insights into the optimal use of stem cell therapy and its potential as a therapeutic option for ED. Taking advantage of different mechanisms of action involved in various regenerative therapies, combination therapies such as SCT and low-energy shock waves or platelet-rich plasma may provide a more effective therapy and warrant further research.

Erectile Dysfunction Treatment Using Stem Cells: A Review

Erectile dysfunction (ED) is a disorder that affects the quality of life and the sexual relations of more than half of the male population aged over 40 years. The prediction regarding the incidence of ED is devastating as it is expected that this disorder will affect more than 300 million men in the next five years. Several studies have suggested the use of stem cells for the treatment of ED and showed that this type of treatment is promising in terms of damaged tissue repair as well as of clinical efficacy; however, there are several gaps in the knowledge and evidence is lacking. In order to highlight a few of them in this review, we performed a research of the literature focusing on currently available clinical studies regarding the clinical efficacy of stem cell administration for the treatment of ED. We reviewed the methods of administration, the cell types used in the performed clinical trials and the safety and efficiency of such procedures. We conclude that there are rapidly expanding and promising results from the reported clinical studies indicating that stem cells could indeed be a potential treatment for patients with ED although more studies are necessary.

Harnessing Stem Cell Potential for the Treatment of Erectile Function in Men with Diabetes Mellitus: From Preclinical/Clinical Perspectives to Penile Tissue Engineering

Background::

According to the World Health Organization, more than 150 million people are diabetic, and this number will increase twofold by the year 2025. Diabetes-related complications affect all body organ systems, including the penis. Diabetes-induced Erectile Dysfunction (ED) is caused by neuropathy of the penile nerves and vasculopathy involving the smooth muscle and endothelium of the corpus cavernosum.

Objective::

This study aims to present an overview of Stem Cell (SC) research in diabetic animal models of ED, focusing on the function, signaling, and niches that have a prominent role in the regeneration of cavernosal cells and penile tissues. We highlight common erectile pathologies caused by diabetes and review relevant preclinical trials. We also discuss paracrine mechanisms of various SC therapies involved in the repair of endothelial cells and cavernous nerves in these diabetic models.

Method::

A PubMed search was performed, with dates ranging from inception until Mar 31, 2019.

Results::

This review provides a comprehensive evaluation of the various strategies that have been investigated for improving SC delivery methods, through preclinical literature and published clinical trials regarding ED in men with diabetes. Various cell-type applications have benefited erectile function in diabetic models of ED.

Conclusion::

This review examines the progress and remaining challenges in diabetes-related SC research regarding ED. Moving forward, it is only with a combined effort of basic biology and translational work that the potential of SC-based therapies in diabetes in ED can be realized.

The Combined Use of Stem Cells and Platelet Lysate Plasma for the Treatment of Erectile Dysfunction: A Pilot Study-6 Months Results

Background: The current treatment of Erectile Dysfunction (ED) is mainly based on the use of drugs that provide erections shortly after use but they do not really treat the problem. Stem cell therapy is a novel treatment with regenerative properties that can possibly treat erectile dysfunction. Methods: Five patients with erectile disease were treated with Adipose-Derived Stem Cells (ADSCs) and Platelet Lysate Plasma (PLP). ADSCs were obtained through abdominal liposuction and PLP was prepared after obtaining blood samples from peripheral veins. Erectile function was evaluated with the International Index of Erectile Function questionnaire (IIEF-5) questionnaire, penile triplex at the 1st, 3rd, 6th and 12th month post-treatment. A CT scan of the head, thorax and abdomen was done before treatment and at the 12th month. Results: IIEF-5 scores were improved in all patients at the 6th month although not in the same pattern in all patients. Peak Systolic Velocity (PSV) also improved at the 6th month in all patients but also with different patterns in each patient, while End Diastolic Velocity (EDV) was more variable. Two patients decreased the treatment they used in order to obtain erection (from Intracavernosal injections (ICI) they used PDE-5Is), two had unassisted erections and one had an initial improvement which decreased at the 6th month. There were no side effects noted. Conclusions: Stem cell therapy in combination with PLP appears to show some improvement in erectile function and has minimal side effects in the short term.

Stem cell therapy in erectile dysfunction: science fiction or realistic treatment option?

Stem cell therapy has become a subject of great interest to researchers worldwide. One of the medical conditions being studied for possible treatment with the use of stem cells is erectile dysfunction, and particularly organic and post-radical prostatectomy erectile dysfunction. However, is stem cell therapy a viable treatment option for erectile dysfunction? The current body of literature provides a wide array of clinical trials performed on animal models simulating different types of human erectile dysfunction. Unfortunately, only a handful of studies have been performed on human patients and almost all of them were phase 1 studies limited by the small sample size. This review aims to summarize the available evidence on the use of stem cell therapy for the treatment of erectile dysfunction and also to provide an overview of upcoming and ongoing clinical trials in this field.

Low-Intensity Shockwave Therapy Improves Hemodynamic Parameters in Patients With Vasculogenic Erectile Dysfunction: A Triplex Ultrasonography-Based Sham-Controlled Trial

BACKGROUND

Although several reports have documented the subjective improvement of erectile function after low-intensity extracorporeal shockwave therapy (LI-ESWT) in patients with vasculogenic erectile dysfunction (ED), objective assessment data of penile hemodynamics are lacking.

AIM

To assess penile hemodynamics before and 3 months after LI-ESWT in a group of patients with documented vasculogenic ED.

METHODS

This was a double-blinded, randomized, sham-controlled trial. Forty-six patients with ED were randomized; 30 underwent LI-ESWT and 16 had a sham procedure in double-blinded fashion. All patients underwent penile triplex ultrasonography by the same investigator immediately before and 3 months after treatment. Patient demographics, International Index of Erectile Function erectile function domain (IIEF-ED) score, and minimal clinically important difference were assessed at baseline and 1, 3, 6, 9, and 12 months after treatment.

OUTCOMES

Changes in peak systolic velocity and resistance index as measured by triplex ultrasonography at baseline and 3 months after treatment were the main outcomes of the study. Secondary outcomes were changes in the IIEF-EF score from baseline to 1, 3, 6, 9, and 12 months after treatment and the percentage of patients reaching a minimal clinically important difference during the same period for the two groups.

RESULTS

IIEF-EF minimal clinically important differences for the active vs sham group were observed for 56.7% vs 12.5% (P = .005) at 1 month, 56.7% vs 12.5% (P = .003) at 3 months, 63.3% vs 18.8% (P = .006) at 6 months, 66.7% vs 31.3% (P = .022) at 9 months, and 75% vs 25% (P = .008) at 12 months. Mean peak systolic velocity increased by 4.5 and 0.6 cm/s in the LI-ESWT and sham groups, respectively (P < .001).

CLINICAL IMPLICATIONS

Such results offer objective and subjective documentation of the value of this novel treatment modality for men with vasculogenic ED.

STRENGTHS AND LIMITATIONS

Strengths include the prospective, randomized, sham-controlled type of study and the assessment of penile hemodynamics. Limitations include the small sample and strict inclusion criteria that do not reflect everyday clinical practice.

CONCLUSION

The present study confirms the beneficial effect of LI-ESWT on penile hemodynamics and the beneficial effect of this treatment up to 12 months. Kalyvianakis D, Hatzichristou D. Low-Intensity Shockwave Therapy Improves Hemodynamic Parameters in Patients With Vasculogenic Erectile Dysfunction: A Triplex Ultrasonography-Based Sham-Controlled Trial. J Sex Med 2017;14:891-897.

In Situ Activation of Penile Progenitor Cells With Low-Intensity Extracorporeal Shockwave Therapy

BACKGROUND

We previously reported that progenitor cells, or stem cells, exist within penile tissue. We hypothesized that acoustic wave stimulation by low-intensity extracorporeal shockwave therapy (Li-ESWT) would activate local stem or progenitor cells within the penis, producing regenerative effects.

AIMS

To study the feasibility of in situ penile progenitor cell activation by Li-ESWT.

METHODS

We performed a cohort analysis of young and middle-age male Sprague-Dawley rats treated with 5-ethynyl-2'-deoxyuridine (EdU) pulse followed by Li-ESWT. In addition, Li-ESWT was applied to cultured Schwann cells and endothelial cells to study the molecular mechanism involved in cell proliferation. Thirty minutes before Li-ESWT, each rat received an intraperitoneal injection of EdU. Li-ESWT was applied to the penis at very low (0.02 mJ/mm² at 3 Hz for 300 pulses) or low (0.057 mJ/mm² at 3 Hz for 500 pulses) energy levels. The endothelial and Schwann cells were treated with very low energy (0.02 mJ/mm² at 3 Hz for 300 pulses) in vitro.

OUTCOMES

At 48 hours or 1 week after Li-ESWT, penile tissues were harvested for histologic study to assess EdU⁺ and Ki-67⁺ cells, and cell proliferation, Ki-67 expression, Erk1/2 phosphorylation, translocation, and angiogenesis were examined in cultured Schwann and endothelial cells after Li-ESWT.

RESULTS

Li-ESWT significantly increased EdU⁺ cells within penile erectile tissues (P < .01) at 48 hours and 1 week. There were more cells activated in young animals than in middle-age animals, and the effect depended on dosage. Most activated cells were localized within subtunical spaces. In vitro studies indicated that Li-ESWT stimulated cell proliferation through increased phosphorylation of Erk1/2.

CLINICAL TRANSLATION

The present results provide a possible explanation for the clinical benefits seen with Li-ESWT.

STRENGTHS AND LIMITATIONS

The main limitation of the present project was the short period of study and the animal model used. Li-ESWT could be less effective in improving erectile function in old animals because of the decreased number and quality of penile stem or progenitor cells associated with aging.

CONCLUSION

Li-ESWT activation of local penile progenitor cells might be one of the mechanisms that contribute to the beneficial effects of shockwave treatment for erectile dysfunction, which represents a non-invasive alternative to exogenous stem cell therapy. Lin G, Reed-Maldonado AB, Wang B, et al. In Situ Activation of Penile Progenitor Cells With Low-Intensity Extracorporeal Shockwave Therapy. J Sex Med 2017;14:493-501.

The controversy surrounding penile rehabilitation after radical prostatectomy

Radical prostatectomy (RP) techniques have been refined in the last few decades. Despite nerve-sparing surgery, erectile dysfunction (ED) still seems to be affecting more than half of patients undergoing RP. Penile rehabilitation consists of understanding the mechanisms that affect erectile function (EF) and utilizing pharmacologic agents, devices or interventions to promote male sexual function before and after any insult to the penile erectile physiologic axis. There currently is a limited amount of clinical trials that assess treatments with the goal of recovering post-prostatectomy EF. The goal of this article is to assess a contemporary series of trials that study penile rehabilitation. Although the current evidence lacks to prove its irrefutable effectiveness, advancements in research and technology forecast a promising future in penile rehabilitation management.

Erectile dysfunction treatment and traditional medicine-can East and West medicine coexist?

Erectile dysfunction (ED) is a common sexual problem affecting many men irrespective of cultures, beliefs and nationalities. While medical therapy for ED has been revolutionized by the advent of oral phosphodiesterase type 5 inhibitors and intracavernosal injection of vasoactive agents, recent technological advances such stem cell therapy, low intensity shock wave and newer generation of penile prosthesis implant offer hope to men who do not respond to conventional medical therapy. In contrast, traditional and complementary medicine (TCM) focuses on the restoration and better overall bodily regulation with the use of various herbal and animal products as well as exercises to invigorate qi (energy) in vital organs. Western medicine involves an analysis of ED symptom and underlying causes that contribute to ED, while TCM emphases the concept of holism and harmonization of body organs to achieve natural sexual life. The following article reviews our current understanding regarding the philosophical approach, and evaluates the evidence surrounding various ED therapies between mainstream Western Medicine and TCM.

Stem Cells in Male Sexual Dysfunction: Are We Getting Somewhere?

INTRODUCTION

Stem cells for sexual disorders are steadily being introduced into clinical trials. Two conditions of importance are the main target for this line of treatment, especially when regarding the wide array of translational and basic science highlighting the potential advantages of regenerative therapy: erectile dysfunction (ED) and more recently Peyronie disease (PD). Cellular therapy offers a treatment modality that might reverse disease progression. It would be used in a curative setting, in contrast to other pharmaceutical agents that are currently available.

AIM

To review basic preclinical studies and recent clinical trials of stem cells on ED and PD.

METHODS

A search of the medical literature for the following terms was performed using PubMed: stem cells, cellular therapy, erectile dysfunction, Peyronie's disease, and clinical trial.

MAIN OUTCOME MEASURES

A non-systematic narrative review and critical reflection on preclinical and clinical studies administering stem cells for ED and PD in animal models and human subjects.

RESULTS

Numerous studies have confirmed the beneficial functional effects of stem cell injection in established animal models on ED and PD. Various stem cell types have been adopted, from embryonic to adult mesenchymal cell types. Each cell type offers distinctive advantages and disadvantages. Diverse administrations of stem cells were investigated, with insignificant variability in the ultimate results. Stem cells appear to have a pronounced paracrine effect, rather than the classic engraftment and differentiation hypothesis. Phase 1 clinical trials using stem cells have not reported any severe adverse events in animals. However, these results cannot be extrapolated to draw any conclusions about efficacy in human patients.

CONCLUSION

Stem cells have an established efficacy in preclinical studies and early clinical trials. Studies are currently being published demonstrating the safety of intrapenile injection of autologous bone marrow- and adipose tissue-derived stem cells. Soebadi MA, Milenkovic U, Weyne E, et al. Stem Cells in Male Sexual Dysfunction: Are We Getting Somewhere? Sex Med Rev 2017;5:222-235.

Advances in stem cell research for the treatment of male sexual dysfunctions

PURPOSE OF REVIEW

To summarize recent literature on basic stem cell research in erectile dysfunction in cavernous nerve injury, aging, diabetes, and Peyronie's disease and to provide a perspective on clinical translation of these cellular therapies.

RECENT FINDINGS

Stem cell research has been concentrated on mesenchymal stem (stromal) cells from bone marrow and adipose tissue. Application of both cell types has produced positive effects on erectile function in various animal models of erectile dysfunction. In acute animal models, such as cavernous nerve injury-induced erectile dysfunction and chemically induced Peyronie's disease, engraftment and differentiation have not been observed, and stem cells are believed to interact with the host tissue in a paracrine fashion, whereas in chronic disease models some evidence suggests both engraftment and paracrine factors may support improved function. Clinical trials are now investigating therapeutic efficacy of cellular therapy, whereas the first safety studies in humans have recently been published.

SUMMARY

Evidence from preclinical studies has established stem cells as a potential curative treatment for erectile dysfunction and early phase clinical trials are currently performed.

Innovative trends and perspectives for erectile dysfunction treatment: A systematic review

Objective

To review contemporary knowledge concerning the innovative trends and perspectives in the treatment of erectile dysfunction (ED).

Methods

Medline was reviewed for English-language journal articles between January 2000 and March 2016, using the terms ‘erectile dysfunction treatments’, ‘new trends’ and ‘perspectives’. In all, 114 original articles and 16 review articles were found to be relevant. Of the 76 cited papers that met the inclusion criteria, 51 papers had level of evidence of 1a–2b, whilst 25 had level of evidence of 3–4. Criteria included all pertinent review articles, randomised controlled trials with tight methodological design, cohort studies, and retrospective analyses. We also manually reviewed references from selected articles.

Results

Several interesting studies have addressed novel phosphodiesterase type 5 inhibitors (PDE5Is), orodispersible tablets, their recent chronic use, and combination with other agents. A few controlled studies have addressed herbal medicine as a sole or additional treatment for ED. Experimental studies and exciting review papers have addressed stem cells as novel players in the field of ED treatment. Other recent articles have revised the current status of low-intensity extracorporeal shockwave therapy in the field of ED. A few articles without long-term data have addressed new technologies that included: external penile support devices, penile vibrators, tissue engineering, nanotechnology, and endovascular tools for ED treatment.

Conclusions

The current treatment of ED is still far from ideal. We expect to see new drugs and technologies that may revolutionise ED treatment, especially in complex cases.

Stem Cell Therapy for Erectile Dysfunction: Progress and Future Directions

INTRODUCTION

Erectile dysfunction (ED) is the most common sexual disorder reported by men to their health-care providers and the most investigated male sexual dysfunction. Currently, the treatment of ED focuses on symptomatic relief of ED and therefore tends to provide temporary relief rather than providing a cure or reversing the underlying cause. Recently, stem cell-based therapies have received increasing attention regarding their potential for the recovery of erectile function. Preclinical studies have shown that these cells may reverse pathophysiological changes leading to ED rather than treating the symptom ED.

AIM

To review available evidence on the efficacy and mechanisms of action of stem cell application for the treatment of ED.

METHODS

A nonsystematic review was conducted on the available English literature between 1966 and 2013 on the search engines SciVerse-sciencedirect, SciVerse-scopus, Google Scholar, and PubMed.

RESULTS

Several preclinical studies have addressed stem cell-based therapies for the recovery of erectile function following cavernous nerve injury and in Peyronie's disease, diabetes, aging, and hyperlipidemia. Overall, these studies have shown beneficial effects of stem cell therapy, while evidence on the mechanisms of action of stem cell therapy still varies between studies. While many authors propose engraftment and differentiation of stem cells, a recent paradigm shift toward paracrine mechanisms of action is observed. One clinical study investigated stem cell therapy in diabetic patients, and two more clinical trials are currently recruiting patients.

CONCLUSIONS

The development of methods to deliver stem cells to the penis has kindled a keen interest in understanding stem cell biology as it related to restoration of normal penile vascular and neuronal homeostasis. The use of stem cells for the treatment of ED represents an exciting new field, which still requires extensive basic research and human trials in diverse ED patient populations in order to define its role in the treatment of ED. Albersen M, Weyne E, and Bivalacqua TJ. Stem cell therapy for erectile dysfunction: Progress and future directions. Sex Med Rev 2013;1:50-64.

DPP-4 inhibition improves a sexual condition?

Erectile dysfunction (ED) is a condition of persistent inability to achieve or maintain an erection sufficient for satisfactory sexual intercourse. The etiology of ED is predominantly vascular, explained by nitric oxide metabolism disturbances being in the background. Nitric oxide enhancing drugs like phosphodiesterase 5 inhibitors, which delay the breakdown of nitric oxide, are widely used, but still without complete success. Restauration of endogenous nitric oxide production focused on improving endothelial dysfunction could be a more effective way of treatment, addressing also other vessels in the body and preventing more serious cardiovascular disease. Endothelial progenitor cells are bone marrow-derived cells found also in human circulation, and may under circumstances be embedded into the vascular intima leading to improvements in nitric oxide production and thus in endothelial function in many organs, including the penis. In this article we hypothesize the potential role of DPP-4 inhibitors, a novel class of antidiabetic drugs in increasing the number of circulating endothelial progenitor cells. Speculated mechanisms include several substrates for DPP-4 inhibitors: GLP-1, SDF-1α, substance P, and PACAP. As DPP-4 inhibitors show favorable safety profiles and do not cause hypoglycemia, they seem to be an attractive treatment option, at least in diabetic patients, and could become a part of vascular regenerative pharmacotherapy, ameliorating also symptoms related to erectile dysfunction. Since erectile dysfunction may precede other cardiovascular vascular events, because the penile arteries are smaller in size and therefore more susceptible to decreased nitric oxide production, treating this condition with an agent affecting positively also other blood vessels could help in preventing other cardiovascular events, including myocardial infarction and stroke. However, caution is required, because DPP-4 inhibitors are a heterogenous class of drugs, with variations regarding strength and duration of action, as well as selectivity and cardiovascular safety profile, which may affect properties other than those important in glucocontrol.

Stem cell therapy for erectile dysfunction of cavernous nerve injury rats: a systematic review and meta-analysis

INTRODUCTION

Stem cell treatment is a novel therapeutic strategy for erectile dysfunction (ED) patients with bilateral cavernous nerve injury (CNI). The relative animal studies provide important clues to design pre-clinical studies and clinical studies further in the future.

PURPOSE

This study aims to evaluate the effects and influential factors of stem cell transplantation on ED rats with CNI.

MATERIALS AND METHODS

We searched PubMed and EBSCO databases published before April 30, 2014 for pre-clinical studies to evaluate the efficacy of stem cell transplantation in the treatment of ED rats with CNI. A systematic review and a planned subgroup analysis were performed to identify whether or not some certain influential factors could bring significant effects on stem cell treatment.

RESULTS

12 studies with 319 rats were enrolled in this meta-analysis. Pooled analysis results confirmed the efficacy of stem cell transplantation. Subgroup analysis results showed that treatment effects were not related to CNI models, follow-up time, stem cell species, stem cell sources, markers and delivery approaches in the transplantation. Uncultured stem cells were poorly effective compared with cultured stem cells. Periprostatic implantation (PPI) with acellular scaffolds could promote cavernous nerve regeneration, but was less effective for smooth muscle cell recovery. Stem cells modified by NGF or BDNF combined with udenafil/bFGF seemed to be more effective than those modified by BDNF alone.

CONCLUSION

This meta-analysis shows that stem cell therapy can be performed to recover erectile function. Future studies should focus on nerve restoration and vascular cell recovery. The synergistic actions of multiple growth factors following stem cell transplantation should also be considered as beneficial strategies to obtain preferable effects.

Expression of a Distinct Set of Chemokine Receptors in Adipose Tissue-Derived Stem Cells is Responsible for In Vitro Migration Toward Chemokines Appearing in the Major Pelvic Ganglion Following Cavernous Nerve Injury

INTRODUCTION

Adipose tissue-derived stem cells (ADSCs) herald tremendous promise for clinical application in a wide range of injuries and diseases. Several preclinical reports demonstrate their efficacy in the treatment of cavernous nerve (CN) injury-induced erectile dysfunction in rats. It was recently illustrated that these effects were established as a result of ADSC migration to the major pelvic ganglion (MPG) where these cells induced neuroregeneration in loco.

AIMS

The study aims to identify chemotactic factors in the MPG following injury and to match upregulated chemokines to their respective receptors in human ADSC on the genomic, structural, and functional levels.

METHODS

Quantitative real-time polymerase chain reaction, fluorescence-activated cell sorting (FACS), intracellular FACS, immunofluorescence microscopy, migration assays, and calcium imaging were used in this study.

MAIN OUTCOME MEASURES

The main outcomes are chemokine expression in the MPG following CN injury, and the functional and structural presence of chemokine receptors in ADSC.

RESULTS

CCR4, CX3CR1, and XCR1 are functionally and structurally present in human ADSC, and are activated by the chemokines CCL2, CX3CL1, and XCL1 respectively, which are upregulated in the MPG following CN injury. CXCR4 and its ligand CXCL12 (SDF1) are likely no major homing factors for ADSC. Expression of chemokine receptor mRNA in ADSC did not necessarily translate into receptor presence at the cell surface and/or functional activation of these receptors. Most of the expressed chemokine receptors were detected in the intracellular compartment of these cells.

CONCLUSIONS

We identified the ligand/chemokine receptor pairs CCL2/CCR4, CX3CL1/CX3CR1, and XCL1/XCR1 as potentially responsible for ADSC homing toward the MPG following CN injury. The intracellular localization of various chemokine receptors likely indicates redirecting of chemokine receptors to the cell surface under specific cellular conditions. Furthermore, modification of expression of these receptors at the genomic level may potentially lead to improved migration toward injury sites and thus enhancement of treatment efficacy. Albersen M, Berkers J, Dekoninck P, Deprest J, Lue TF, Hedlund P, Lin C-S, Bivalacqua TJ, Van Poppel H, De Ridder D, and Van der Aa F. Expression of a distinct set of chemokine receptors in adipose tissue-derived stem cells is responsible for in vitro migration toward chemokines appearing in the major pelvic ganglion following cavernous nerve injury. Sex Med 2013;1:3-15.

Comparison between subcutaneous injection of basic fibroblast growth factor-hydrogel and intracavernous injection of adipose-derived stem cells in a rat model of cavernous nerve injury

OBJECTIVE

To compare the effects of subcutaneous penile injection of basic fibroblast growth factor (bFGF)-hydrogel and intracavernous injection of human adipose-derived stem cells (h-ADSCs) on improving erectile function in a rat model of cavernous nerve injury.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were randomly divided into 5 groups (n = 10 per group): age-matched control (normal group), bilateral cavernous nerve injury (BCNI group), penile subcutaneous injection of hydrogel after BCNI (hydrogel group), penile subcutaneous injection of bFGF-hydrogel after BCNI (bFGF-hydrogel group) and intracavernous injection of h-ADSCs after BCNI (ADSC group). Four weeks after the treatment, all rats underwent an erectile function test. Then, penile tissue was harvested for immunohistological analysis of bFGF, phalloidin, and cluster of differentiation (CD) 31. The cyclic guanosine monophosphate (cGMP) level of the corpus cavernosum was quantified by cGMP assay.

RESULTS

From the functional test and immunohistological result, we observed that bFGF-hydrogel and h-ADSCs injection significantly elevated intracavernous pressure. The evaluation of filamentous actin content, CD31 expression, and cGMP concentration in the corpus cavernosum were meaningfully increased in the bFGF-hydrogel and ADSC groups compared with BCNI group. The bFGF released from bFGF-hydrogel prevented smooth muscle atrophy. Moreover, bFGF expression was significantly increased in bFGF-hydrogel group.

CONCLUSION

The subcutaneous injection of bFGF-hydrogel prevented smooth muscle atrophy, increased the intracavernous pressure, and improved erectile function like an intracavernous injection of h-ADSCs.

Low-intensity shock wave therapy and its application to erectile dysfunction

Although phosphodiesterase type 5 inhibitors (PDE5Is) are a revolution in the treatment of erectile dysfunction (ED) and have been marketed since 1998, they cannot restore pathological changes in the penis. Low-energy shock wave therapy (LESWT) has been developed for treating ED, and clinical studies have shown that LESWT has the potential to affect PDE5I non-responders with ED with few adverse effects. Animal studies have shown that LESWT significantly improves penile hemodynamics and restores pathological changes in the penis of diabetic ED animal models. Although the mechanisms remain to be investigated, recent studies have reported that LESWT could partially restore corpus cavernosum fibromuscular pathological changes, endothelial dysfunction, and peripheral neuropathy. LESWT could be a novel modality for treating ED, and particularly PDE5I non-responders with organic ED, in the near future. However, further extensive evidence-based basic and clinical studies are needed. This review intends to summarize the scientific background underlying the effect of LESWT on ED.

Treatment of erectile dysfunction: new targets and strategies from recent research

In recent years, research on penile erection has increasingly been centered on the molecular mechanisms involved. Major progress has been made in the field and at present a whole number of neurotransmitters, chemical effectors, growth factors, second-messenger molecules, ions, intercellular proteins, and hormones have been characterized as components of the complex process of erection. This knowledge has led to the discovery of several new therapeutic targets and multiple medical approaches for the treatment of erectile dysfunction (ED). This review focuses on the progress made in this field within the last few years.

Stem-cell therapy for erectile dysfunction

INTRODUCTION

Erectile dysfunction (ED) is the most common sexual disorder that men report to healthcare providers, and is the male sexual dysfunction that has been most investigated. Current treatments for ED focus on relieving the symptoms of ED and therefore tend to provide a temporary solution rather than a cure or reversing the cause. Recently, therapies based on stem cells (SCs) have had an increasing attention for their potential to restore erectile function. Preclinical studies showed that these cells might reverse the pathophysiological changes leading to ED, rather than treating the symptoms of ED. This review is intended to provide an overview of contemporary reports on the use of SCs to treat ED.

METHODS

We made an extensive search for reports on SC-based therapy for the management of ED, published in English between 1966 and 2013, using the search engines SciVerse-sciencedirect, SciVerse-scopus, Google Scholar and Pubmed, with the search terms 'erectile dysfunction', 'stem cells', 'multipotent stromal cells', 'adipose (tissue) derived stem cells', 'bone-marrow derived stem cells', 'animal model', 'diabetes', 'ageing', 'Peyronie's Disease' and 'cavernous nerve injury'.

RESULTS

Fifty-four papers were identified and contributed, either as an original research report or review thereof, to this review. Several preclinical studies addressed SC-based therapies for the recovery of erectile function caused by a variety of both chronic and acute conditions. Overall, these studies showed beneficial effects of SC therapy, while evidence on the mechanisms of action of SC therapy varied between studies. One clinical trial investigated the short-term effects of SC therapy in diabetic patients with ED. Two more clinical trials are currently recruiting patients.

CONCLUSIONS

The rapidly expanding and highly promising body of preclinical work on SC-based medicine providing a potential cure for ED, rather than merely symptom relief, is indicative of the increasing interest in regenerative options for sexual medicine over the past decade. Clinical trials are currently recruiting patients to test the preclinical results in men with ED.

Both immediate and delayed intracavernous injection of autologous adipose-derived stromal vascular fraction enhances recovery of erectile function in a rat model of cavernous nerve injury

BACKGROUND

Intracavernous injection of cultured adipose-derived stem cells (ADSCs) effectively restores erectile function in cavernous nerve (CN)-injured rats when administered at the time of injury. However, culturing exposes ADSCs to the risk of contamination and dedifferentiation.

OBJECTIVE

Explore the effect of uncultured autologous adipose-derived stromal vascular fraction (SVF) on improving erectile function in a rat model of CN injury when administered at the time of injury or 4 wk after injury.

DESIGN, SETTING, AND PARTICIPANTS

Eighty-nine male Sprague Dawley rats were randomly divided into four groups. CN injury or sham surgery was performed at the start of the study, and rats were treated with either SVF or vehicle. Functional testing and histologic analysis were performed 12 wk after CN crush or sham surgery.

INTERVENTION

We used intracavernous injection of saline immediately after CN crush (n=23), intracavernous injection of SVF immediately after CN crush (n=17), intracavernous injection of SVF 4 wk after CN crush (n=23), or sham surgery (n=26).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We studied intracavernous pressure (ICP) response to CN electrostimulation and performed histologic examination of midpenile cross-sections. Data were analyzed using one-way analysis of variance followed by the Tukey-Kramer test.

RESULTS AND LIMITATIONS

Both immediate and delayed treatment with SVF resulted in a significantly increased ICP-to-mean arterial pressure ratio compared with the vehicle-treated group. Both immediate and delayed treatment with SVF significantly increased expression of neuronal nitric oxide synthase and neurofilament in dorsal penile nerves compared to the vehicle group. Furthermore, the smooth muscle-to-collagen ratio within the corpus cavernosum was significantly improved in both of the SVF groups compared to vehicle-treated rats. The main limitation of the study is the lack of determination of the SVF components.

CONCLUSIONS

Uncultured autologous SVF injected immediately or 4 wk after CN crush improved erectile function, promoted nerve regeneration, and prevented fibrosis of the corpus cavernosum following CN injury.