The effect of intracavernous injection of adipose tissue-derived stem cells on hyperlipidemia-associated erectile dysfunction in a rat model

Magnetic mesoporous silica nanoparticles loaded with peptides for the targeted repair of cavernous nerve injury underlying erectile dysfunction

Erectile dysfunction (ED) is a common male sexual disorder characterized by repeated or persistent difficulty in achieving or maintaining an erection. It can arise from various factors, with cavernous nerve injury (CNI) from radical prostatectomy being a predominant cause of iatrogenic ED, posing significant clinical concerns. The complexity of cavernous tissue damage in CNI-induced ED (CNIED) often results in poor efficacy and resistance to conventional vascular ED treatments. To address CNI-induced ED, this study developed a system of magnetic mesoporous silica nanoparticles (MSNs) loaded with peptides for targeted treatment. Core-shell Fe3O4-coated MSNs were used as drug carriers and loaded with RADA16-I/RAD-RGI peptides (PD) to create a neurotrophic microenvironment to treat peripheral nerve defects. Furthermore, the neuro-targeting peptide HLNILSTLWKYR (PT) was grafted onto MSNs. The in vivo therapeutic effect was evaluated using a rat bilateral cavernous nerve injury (BCNI) model. The results showed that the neuro-targeted Fe3O4@SiO2-PT-PD nanoparticles significantly promoted regeneration of the cavernous nerve and restored erectile function. This promising strategy offers significant clinical potential for treating CNI-induced ED. Nanomedicine technology has the potential to not only improve treatment outcomes but also reduce side effects in healthy cells, paving the way for more accurate targeted repair of cavernous nerve damage.

Oxidative Stress and Erectile Dysfunction: Pathophysiology, Impacts, and Potential Treatments

Erectile dysfunction (ED) is a prevalent condition affecting men's sexual health, with oxidative stress (OS) having recently been identified as a significant contributing causative factor. This narrative review aims to elucidate the role of OS in the pathophysiology of ED, focusing on impact, mechanisms, and potential therapeutic interventions. Key findings indicate that OS disrupts endothelial function and nitric oxide (NO) signaling, crucial for erectile function. Various sources of reactive oxygen species (ROS) and their detrimental effects on penile tissue are discussed, including aging, diabetes mellitus, hypertension, hyperlipidemia, smoking, obesity, alcohol consumption, psychological stress, hyperhomocysteinemia, chronic kidney disease, and sickle cell disease. Major sources of ROS, such as NADPH oxidase, xanthine oxidase, uncoupled endothelial NO synthase (eNOS), and mitochondrial electron transport, are identified. NO is scavenged by these ROS, leading to endothelial dysfunction characterized by reduced NO availability, impaired vasodilation, increased vascular tone, and inflammation. This ultimately results in ED due to decreased blood flow to penile tissue and the inability to achieve or maintain an erection. Furthermore, ROS impact the transmission of nitrergic neurotransmitters by causing the death of nitrergic neurons and reducing the signaling of neuronal NO synthase (nNOS), exacerbating ED. Therapeutic approaches targeting OS, including antioxidants and lifestyle modifications, show promise in ameliorating ED symptoms. The review underscores the need for further research to develop effective treatments, emphasizing the interplay between OS and vascular health in ED. Integrating pharmacological and non-pharmacological strategies could enhance clinical outcomes for ED patients, advocating for OS management in ED treatment protocols to improve patient quality of life.

Research Advances in Stem Cell Therapy for Erectile Dysfunction

Erectile dysfunction (ED) is a common clinical condition that mainly affects men aged over 40 years. Various causes contribute to the progression of ED, including pelvic nerve injury, diabetes, metabolic syndrome, age, Peyronie's disease, smoking, and psychological disorders. Current treatments for ED are limited to symptom relief and do not address the root cause. Stem cells, with their powerful ability to proliferate and differentiate, are a promising approach for the treatment of male ED and are gradually gaining widespread attention. Current uses for treating ED have been studied primarily in experimental animals, with most studies observing improvements in erectile quality as well as improvements in erectile tissue. However, research on stem cell therapy for human ED is still limited. This article summarizes the recent literature on basic stem cell research on ED, including cavernous nerve injury, aging, diabetes, and sclerosing penile disease, and describes mechanisms of action and therapeutic effects of various stem cell therapies in experimental animals. Stem cells are also believed to interact with host tissue in a paracrine manner, and improved function can be supported through both implantation and paracrine factors. To date, stem cells have shown some preliminary promising results in animal and human models of ED.

Bibliometric and Visualization Analysis of Stem Cell Therapy for Erectile Dysfunction

Purpose

As a common male disease, erectile dysfunction (ED) seriously affects the physical and mental health of patients. In recent years, studies have continued to point out the great potential of stem cell therapy (SCT) in the treatment of ED. The purpose of this study is to comprehensively analyze the research of SCT for ED and understand the development trends and research frontiers in this field.

Methods

Publications regarding SCT and ED were retrieved and collected from the Web of Science Core Collection. CiteSpace and VOSviewer software were then utilized for bibliometric and visualization analysis.

Results

A total of 524 publications were eventually included in this study. The annual number of publications in this field was increasing year by year. China and the USA were the two most productive countries. Lin GT, Lue TF and Lin CS, and the University of California San Francisco where they worked were the most productive research group and institution, respectively. The journal with the largest number of publications was The Journal of Sexual Medicine, and the following were mostly professional journals of urology and andrology. Diabetes mellitus-induced ED and cavernous nerve injury-related ED were the two most commonly constructed models of ED in studies. Concerning the types of stem cells, mesenchymal stem cells derived from adipose and bone marrow were most frequently used. Moreover, future research would mainly focus on exosomes, tissue engineering technology, extracorporeal shockwave therapy, and clinical translation.

Conclusion

The research of SCT for ED will receive increasing global attention in the future. Our study provided bibliometric and visualization analysis of published literature, helping researchers understand the global landscape and frontiers in this field. More preclinical and clinical studies should be conducted to more deeply explore the underlying mechanisms of treatment and promote clinical translation.

The Impact and Implications of Regenerative Medicine in Urology

Urology focuses on the treatment of genitourinary disorders through therapies ranging from lifestyle changes to advanced surgeries; the field has recently incorporated robotic and minimally invasive technologies that have improved patient outcomes and reduced hospital stays and complications. However, these methods still have certain limitations. Regenerative medicine, focusing on natural repair abilities, can be an effective and safer alternative. This review aims to examine the impact of regenerative medicine in urology. We adopted a systematic review design by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. An exhaustive online literature search involving the databases PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), and Google Scholar was conducted spanning the period between January 2010 and October 2023. Data were extracted from studies on regenerative medicine in urology with a special focus on efficacy and safety. Data from 16 studies were analyzed, which showed that cell therapy, biological materials, and tissue engineering are generally used in the field of urinary diseases. The main applications include the regeneration of urinary tissue, the correction of urinary incontinence, the treatment of erectile dysfunction, the reconstruction of ureteric defects, and the formation of bladder tissue. The study findings generally lack definitive conclusions on effectiveness and safety. While our results indicate that regenerative medicine is successful on a subjective level, more clinical trials are needed to establish its effectiveness and safety.

Feasibility of minimally invasive, same-day injection of autologous adipose-derived stem cells in the treatment of erectile dysfunction

OBJECTIVE

To investigate feasibility and safety of a new minimally invasive same-day method of autologous adipose derived stem cell (ADSC) transplantation in men suffering from ED.

MATERIALS AND METHODS

Prospective case series of 10 men with an IIEF-EF domain score <17. The IIEF questionnaire was filled out at baseline and 1, 2 and 3 months after treatment. Side effects were assessed by investigations and interviews until 6 months after treatment. The myStem® X2 kit was used for preparation of ADSC: Adipose tissue was harvested from the patient himself under local anesthesia and immediately prepared and injected into the penis. Primary endpoints were feasibility and safety. Secondary outcomes included effects on ED and changes in the remaining IIEF domains.

RESULTS

Ten men were included. Only one adverse event in the form of minor blue discoloration at the fat harvest site was registered. There were statistically significant improvements in IIEF-EF at one, two and three months after treatment compared to baseline with the median score increasing from 5.5 to 10.5, 10.5 and 10, respectively. Considering the individual patients, 3/10 men achieved an improvement equal to or greater than the minimal clinically important difference according to their baseline IIEF-EF score.

CONCLUSIONS

Our study confirms the feasibility and safety of this minimally invasive, same-day delivery of ADSC. Due to the design and size on the study, conclusions should not be drawn regarding efficacy, but the method seems worthy of further study.

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.

Management of male erectile dysfunction: From the past to the future

Erectile dysfunction is a common disease of the male reproductive system, which seriously affects the life quality of patients and their partners. At present, erectile dysfunction is considered as a social-psychological-physiological disease with complex etiology and various treatment methods. Oral PDE5I is the first-line treatment for erectile dysfunction with the advantages of high safety, good effect and non-invasiveness. But intracavernosal injection, hormonal replacement therapy, vacuum erection device, penile prosthesis implantation can also be alternative treatments for patients have organic erectile dysfunction or tolerance to PDE5I. With the rapid development of technologies, some new methods, such as low-intensity extracorporeal shock wave and stem cell injection therapy can even repair the organic damage of the corpora cavernosa. These are important directions for the treatment of male erectile dysfunction in the future. In this mini-review, we will introduce these therapies in detail.

Co-overexpression of VEGF and Smad7 improved the therapeutic effects of adipose-derived stem cells on neurogenic erectile dysfunction in the rat model

Cavernous nerve injury is the main cause of erectile dysfunction (ED) after radical prostatectomy (RP). In our previous study, injection of adipose-derived stem cells (ADSCs) into the cavernosum can repair damaged cavernosum nerves and ED can be restored to a certain extent. In order to improve these therapeutic effects, we evaluated the efficacy of ADSCs co-modified with VEGF and Smad7 in a rat model. SD rats were randomly divided into six groups: a sham surgery group, and the five bilateral cavernous nerve injury (BCNI) groups were injected with ADSC or ADSCs genetically modified by VEGF (ADSC-V), Smad7 (ADSC-S), or VEGF&Smad7 (ADSC-V&S) or phosphate-buffered saline (PBS). The results indicated that the erectile function of the ADSC-V, ADSC-S, and ADSC-V&S groups was significantly recovered, and the erectile function of the ADSC-V&S group was more distinctly recovered as compared to the other groups. The same results are shown in the expression of neuronal nitric oxide synthase and the smooth muscle/collagen ratio of penile tissue comparing the ADSC-V&S group to the ADSC-V and ADSC-S group. These experimental data suggest that ADSCs co-overexpressed with VEGF and Smad7 can significantly improve erectile function after BCNI. This study provides new therapeutic thoughts for ED following RP.

Cavernous Nerve Injury Resulted Erectile Dysfunction and Regeneration

Erectile dysfunction (ED) is an important cause of reduced quality of life for men and their partners. Recent studies have found that cavernous nerve injury (CNI) during prostate cancer surgery and other pelvic surgery results in medically induced CNIED in more than 80% of patients. The efficacy of first- and second-line treatment options for ED is poor. A great deal of research has been devoted to exploring new methods of neuroprotection and nerve regeneration to save erectile function in patients with CNIED, especially in patients with cavernous nerve injury after prostate cancer surgery. In addition, such as neuromodulatory proteins, proimmune ligands, gene therapy, stem cell therapy, and the current cutting-edge low-energy shock wave therapy have shown advantages in basic research and limited clinical studies. In the context of today's modern medicine, these new therapeutic techniques are expected to be new tools in the treatment of cavernous nerve injury erectile dysfunction. This article presents the main causes, mechanisms, and treatment of cavernous nerve injury erectile dysfunction and combines them with new treatment strategies.

Intracavernous Injection of Autologous Platelet-Rich Plasma Ameliorates Hyperlipidemia-Associated Erectile Dysfunction in a Rat Model

Introduction

Hyperlipidemia is associated with an increased risk of erectile dysfunction (ED) mediated by endothelial damage. Platelet-rich plasma (PRP) contains numerous angiogenic growth factors. Currently, evidence supporting the use of PRP for ED treatment is limited.

Aim

We investigated PRP in a rat model of hyperlipidemia-associated ED.

Methods

Thirty 2-month-old male Sprague–Dawley rats were randomly divided into 3 groups. 20 rats were fed a high-fat diet for 5 months and were randomly divided into 2 groups: (i) rats in the H group received supernatant injection into the corpus cavernosum weekly for 4 weeks; (ii) rats in the H + PRP group received PRP injection into the corpus cavernosum weekly for 4 weeks. 10 rats were fed a standard diet for 5 months and received supernatant injection into the corpus cavernosum weekly for 4 weeks (N group). 7 days after the 4th injection, all rats underwent erectile function testing and then euthanasia.

Main outcome measures

Erectile function was evaluated by measuring intracavernous pressure (ICP) and mean arterial pressure (MAP). Serum and penile tissue were collected for metabolic variable assessment and histochemical examination, respectively.

Results

Intracavernous pressure/MAP and area under the curve/MAP ratios were significantly higher in the N and H + PRP groups than in the H group. Insulin-like growth factor-1, brain-derived neurotrophic factor, and vascular endothelial growth factor levels were significantly higher in the H + PRP group than in the N and H groups. Corporal neuronal nitric oxide synthase, endothelial nitric oxide synthase, and endothelial cells were weakly expressed in the H group compared with the N and H + PRP groups. Intracorporal oxidative stress and apoptotic index were significantly higher in the H group than in the N and H + PRP groups.

Conclusions

This preclinical evidence suggests that clinical trials of PRP in men with ED should be considered. PRP may play a role in ED management.

Huang YC, Wu CT, Chen MF, et al. Intracavernous Injection of Autologous Platelet-Rich Plasma Ameliorates Hyperlipidemia-Associated Erectile Dysfunction in a Rat Model. Sex Med 2021;9:100317.

Reviewing the evidence for shockwave- and cell-based regenerative therapies in the treatment of erectile dysfunction

Erectile dysfunction (ED) is both a common and complex disease process. Existing ED treatments do not always achieve adequate results. There is clinical interest in employing regenerative therapies, including low-intensity extracorporeal shockwave therapy (Li-ESWT), platelet rich plasma (PRP), and stem cell therapy (SCT), in the treatment of ED as adjunct or alternative treatments. Here, we present evidence for emerging shockwave- and cell-based regenerative therapies for the treatment of ED following a thorough review of the existing PubMed literature pertaining to Li-ESWT, PRP, and SCT in relation to the treatment of ED. Li-ESWT causes microtrauma in tissue that hypothetically upregulates angiogenesis and recruits stem cells. Several large-scale systematic reviews and meta-analyses have reported that Li-ESWT improved ED in humans. Additionally, evidence has commenced to show that Li-ESWT may be effective against two recognized and complex etiologies of ED: diabetic and neurogenic. PRP delivers an autologous sample rich in growth factors to damaged tissue. Animal model studies have demonstrated improved erectile function recovery as well as preservation of cavernous nerve axons. Studies with PRP in humans are limited. SCT utilizes the regenerative potential of stem cells for healing of damaged tissue. In the treatment of ED, SCT has been used in the setting of diabetic and post-prostatectomy ED. Results of human studies are varied, although SCT treatments did result in increased erectile rigidity with some patients recovering the ability to achieve penetration. While these regenerative therapies show potential to augment the current treatment regimen for ED, there is a paucity of evidence to support the safety and efficacy of these treatments. Further research is necessary to define the role of these alternative therapies in the treatment of ED.

The influence of smoking exposure and cessation on penile hemodynamics and corporal tissue in a rat model

Background

While epidemiological studies have clearly documented that smoking cessation significantly enhances sexual health, the underlying mechanism remains largely unknown. Thus, we wished to explore possible mechanisms by using a rat model of smoking-associated erectile dysfunction (ED).

Methods

Forty 8-week old male Sprague-Dawley rats were divided into 4 groups. Ten rats were exposed only to room air (N group). The remaining 30 rats were passively exposed to cigarette smoke over a 12-week period. At the end of 12 weeks, the smoking (S, n=10) group underwent immediate erectile function testing and were sacrificed. The remaining 20 rats were exposed to room air only for 4 (Q4W, n=10) or 8 (Q8W, n=10) weeks and then underwent erectile function testing and sacrifice. Erectile function was evaluated by measuring intracavernous pressure (ICP) and mean arterial pressure (MAP). After blood collection for serum testosterone determination, rats were sacrificed to obtain corporal tissue for immunohistochemistry.

Results

Mean ICP/MAP ratio was significantly lower in the S group compared to the N and Q8W groups (0.52±0.11, 0.94±0.05, and 0.94±0.12, respectively, P=0.0189). Smooth muscle/collagen ratio was also significantly lower in the S group compared to the N and Q8W groups (11.8±0.94, 17.5±1.82, and 16.4±0.60, respectively, P=0.0008). Oxidative stress and apoptotic indices were significantly higher in the S group compared to the N and Q8W groups. Neuronal and endothelial nitric oxide synthases were significantly less expressed in the S group compared to the N and Q8W groups.

Conclusions

Smoking cessation is associated with partial recovery of penile hemodynamics in a rat model of smoking associated ED.

Non-conventional therapies for Peyronie's disease: what is the evidence for efficacy?

Background

In recent years, there has been a surge in non-conventional therapies for Peyronie’s disease (PD). With increasing interest in these novel therapies, we conducted a narrative review to explore the efficacy and safety of these treatments to provide clarity for patients and providers.

Methods

A literature search was conducted to find studies describing non-conventional treatments of PD. These treatments were defined as those within the standard of care, including intralesional therapies and surgical options.

Results

A total of 14 studies were found. Non-conventional therapies included platelet-rich plasma (PRP), hyaluronic acid (HA), combination therapy of PRP and HA, extracorporeal shockwave therapy (ESWT), stem cell therapy (SCT), mycophenolate mofetil (MMF), and H-100. Most studies were limited to animal models and reported modest improvements in angulation and erectile function. Complication rates and cost of each treatment were infrequently reported.

Conclusions

There is limited evidence supporting non-conventional therapies for PD. As such, they are currently not recommended in clinical guidelines.

Advances in stem cell therapy for erectile dysfunction

INTRODUCTION

Stem cell (SC) application is a promising area of research in regenerative medicine, with the potential to treat, prevent, and cure disease. In recent years, the number of studies focusing on SCs for the treatment of erectile dysfunction (ED) and other sexual dysfunctions has increased significantly.

AREAS COVERED

This review includes critical ED targets and preclinical studies, including the use of SCs and animal models in diabetes, aging, cavernous nerve injury, and Peyronie's disease. A literature search was performed on PubMed for English articles.

EXPERT OPINION

Combination treatment offers better results than monotherapy to improve pathological changes in diabetic ED. Regenerative medicine is a promising approach for the maintenance of sexual health and erectile function later in life. Cavernous nerve regeneration and vascular recovery employing SC treatment may be focused on radical prostatectomy-induced ED. Notwithstanding, there are a number of hurdles to overcome before SC-based therapies for ED are considered in clinical settings. Paracrine action, not cellular differentiation, appears to be the principal mechanism of action underlying SC treatment of ED. Intracavernosal injection of a single SC type should be the choice protocol for future clinical trials.

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.

Update on the mechanisms of homing of adipose tissue-derived stem cells

Adipose tissue-derived stem cells (ADSCs), which resemble bone marrow mesenchymal stromal cells (BMSCs), have shown great advantages and promise in the field of regenerative medicine. They can be readily harvested in large numbers with low donor-site morbidity. To date, a great number of preclinical and clinical studies have shown ADSCs' safety and efficacy in regenerative medicine. However, a better understanding of the mechanisms of homing of ADSCs is needed to advance the clinical utility of this therapy. In this review, the reports of the homing of ADSCs were searched using Pubmed and Google Scholar to update our knowledge. ADSCs were proved to interact with endothelial cells by expressing the similar integrins with BMSCs. In addition, ADSCs do not possess the dominant ligand for P-selectin, just like BMSCs. Stromal derived factor-1 (SDF-1)/CXCR4 and CXC ligand-5 (CXCL5)/CXCR2 interactions are the two main axes governing ADSCs extravasation from bone marrow vessels. Some more signaling pathways involved in migration of ADSCs have been investigated, including LPA/LPA1 signaling pathway, MAPK/Erk1/2 signaling pathway, RhoA/Rock signaling pathway and PDGF-BB/PDGFR-β signaling pathway. Status quo of a lack of intensive studies on the details of homing of ADSCs should be improved in the near future before clinical application.

A comparative assessment of adipose-derived stem cells from subcutaneous and visceral fat as a potential cell source for knee osteoarthritis treatment

The intra‐articular injection of adipose‐derived stem cells (ASCs) is a novel potential therapy for patients with osteoarthritis (OA). However, the efficacy of ASCs from different regions of the body remains unknown. This study investigated whether ASCs from subcutaneous or visceral adipose tissue provide the same improvement of OA. Mouse and human subcutaneous and visceral adipose tissue were excised for ASC isolation. Morphology, proliferation, surface markers and adipocyte differentiation of subcutaneous ASCs (S‐ASCs) and visceral ASCs (V‐ASCs) were analysed. A surgically induced rat model of OA was established, and 4 weeks after the operation, S‐ASCs, V‐ASCs or phosphate‐buffered saline (PBS, control) were injected into the articular cavity. Histology, immunohistochemistry and gene expression analyses were performed 6 weeks after ASC injection. The ability of ASCs to differentiate into chondrocytes was assessed by in vitro chondrogenesis, and the immunosuppressive activity of ASCs was evaluated by co‐culturing with macrophages. The proliferation of V‐ASCs was significantly greater than that of S‐ASCs, but S‐ASCs had the greater adipogenic capacity than V‐ASCs. In addition, the infracted cartilage treated with S‐ASCs showed significantly greater improvement than cartilage treated with PBS or V‐ASCs. Moreover, S‐ASCs showed better chondrogenic potential and immunosuppression in vitro. Subcutaneous adipose tissue is an effective cell source for cell therapy of OA as it promotes stem cell differentiation into chondrocytes and inhibits immunological reactions.

Efficient generation of functional Schwann cells from adipose-derived stem cells in defined conditions

Schwann cells (SCs) are hitherto regarded as the most promising candidates for viable cell-based therapy to peripheral nervous system (PNS) injuries or degenerative diseases. However, the extreme drawbacks of transplanting autologous SCs for clinical applications still represent a significant bottleneck in neural regenerative medicine, mainly owing to the need of sacrificing a functional nerve to generate autologous SCs and the nature of slow expansion of the SCs. Thus, it is of great importance to establish an alternative cell system for the generation of sufficient SCs. Here, we demonstrated that adipose-derived stem cells (ADSCs) of rat robustly give rise to morphological, phenotypic and functional SCs using an optimized protocol. After undergoing a 3-week in vitro differentiation, almost all of treated ADSCs exhibited spindle shaped morphology similar to genuine SCs and expressed SC markers GFAP and S100. Most importantly, apart from acquisition of SC antigenic and biochemical features, the ADSC-derived SCs were functionally identical to native SCs as they possess a potential ability to form myelin, and secret nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and glia-derived neurotrophic factor (GDNF). The current study may provide an ideal strategy for harvesting sufficient SCs for cell-based treatment of various peripheral nerve injuries or disorders.

The Current Status of Stem-Cell Therapy in Erectile Dysfunction: A Review

Stem cells are undifferentiated cells that are capable of renewal and repair of tissue due to their capacity for division and differentiation. The purpose of this review is to describe recent advances in the use of stem cell (SC) therapy for male erectile dysfunction (ED). We performed a MEDLINE database search of all relevant articles regarding the use of SCs for ED. We present a concise summary of the scientific principles behind the usage of SC for ED. We discuss the different types of SCs, delivery methods, current pre-clinical literature, and published clinical trials. Four clinical trials employing SC for ED have been published. These articles are summarized in this review. All four report improvements in ED after SC therapy. SC therapy remains under investigation for the treatment of ED. It is reassuring that clinical trials thus far have reported positive effects on erectile function and few adverse events. Safety and methodical concerns about SC acquisition, preparation and delivery remain and require continued investigation prior to wide-spread application of these methods.

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.

The Effects of Adipose-Derived Stem Cells in a Rat Model of Tobacco-Associated Erectile Dysfunction

Tobacco use is associated with erectile dysfunction (ED) via a number of mechanisms including vascular injury and oxidative stress in corporal tissue. Adipose derived stem cells (ADSC) have been shown to ameliorate vascular/corporal injury and oxidative stress by releasing cytokines, growth factors and antioxidants. We assessed the therapeutic effects of intracavernous injection of ADSC in a rat model of tobacco-associated ED. Thirty male rats were used in this study. Ten rats exposed to room air only served as negative controls. The remaining 20 rats were passively exposed to cigarette smoke (CS) for 12 weeks. At the 12-week time point, ADSC were isolated from paragonadal fat in all rats. Amongst the 20 CS exposed rats, 10 each were assigned to one of the two following conditions: (i) injection of phosphate buffered saline (PBS) into the corpora cavernosa (CS+PBS); or (ii) injection of autologous ADSC in PBS into the corpora cavernosa (CS+ADSC). Negative control animals received PBS injection into the corpora cavernosa (normal rats [NR] + PBS). After injections all rats were returned to their previous air versus CS exposure state. Twenty-eight days after injection, all rats were placed in a metabolic cage for 24-hour urine collection to be testing for markers of oxidative stress. After 24-hour urine collection all 30 rats also underwent erectile function testing via intracavernous pressure (ICP) testing and were then sacrificed. Corporal tissues were obtained for histological assessment and Western blotting. Mean body weight was significantly lower in CS-exposed rats than in control animals. Mean ICP, ICP /mean arterial pressure ratio, serum nitric oxide level were significantly lower in the CS+PBS group compared to the NR+PBS and CS+ADSC groups. Urine markers for oxidative stress were significantly higher in the CS+PBS group compared to the NR+PBS and CS+ADSC groups. Mean expression of corporal nNOS and histological markers for endothelial and smooth muscle cells was significantly lower, and tissue apoptotic index significantly higher, in the CS+PBS group compared to the NR+PBS and CS+ADSC groups. Our findings confirm that chronic tobacco exposure causes ultrastructural damage to the corporal tissue and increases systemic oxidative stress states. Treatment with ADSC ameliorates these adverse effects and holds promise as a potential therapy for tobacco-related ED.

Mesenchymal stem cell-based gene therapy for erectile dysfunction

Despite the overwhelming success of PDE5 inhibitor (PDE5I), the demand for novel pharmacotherapeutic and surgical options for ED continues to rise owing to the increased proportion of elderly individuals in the population, in addition to the growing percentage of ED patients who do not respond to PDE5I. Surgical treatment of ED is associated with many complications, thus warranting the need for nonsurgical therapies. Moreover, none of the above-mentioned treatments essentially corrects, cures or prevents ED. Although gene therapy is a promising option, many challenges and obstacles such as local inflammatory response and random transgene expression, in addition to other safety issues, limit its use at the clinical level. The use of stem cell therapy alone also has many shortcomings. To overcome these inadequacies, many scientists and clinicians are investigating new gene and stem cell therapies.

Intracavernous delivery of clonal mesenchymal stem cells rescues erectile function in the streptozotocin-induced diabetic mouse

The major hurdle for the clinical application of stem cell therapy is the heterogeneous nature of the isolated cells, which may cause different treatment outcomes. The aim of this study was to examine the effectiveness of mouse clonal bone marrow-derived stem cells (BMSCs) obtained from a single colony by using subfractionation culturing method for erectile function in diabetic animals. Twelve-week-old C57BL/6J mice were divided into four groups: controls, diabetic mice, and diabetic mice treated with a single intracavernous injection of PBS (20 μL) or clonal BMSCs (3 × 10(5) cells/20 μL). Clonal BMSCs were isolated from 5-week-old C3H mice. Two weeks after treatment, erectile function was measured by electrical stimulation of the cavernous nerve. The penis was stained with antibodies to PECAM-1, smooth muscle α-actin, neuronal nitric oxide synthase (nNOS), neurofilament, and phosphorylated endothelial NOS (phospho-eNOS). We also performed Western blot for phospho-eNOS, and eNOS in the corpus cavernosum tissue. Local delivery of clonal BMSCs significantly restored cavernous endothelial and smooth muscle cell contents, and penile nNOS and neurofilament contents, and induced eNOS phosphorylation (Ser1177) in diabetic mice. Intracavernous injection of clonal BMSCs induced significant recovery of erectile function, which reached 80-90% of the control values. Clonal BMSCs successfully restored erectile function through dual angiogenic and neurotrophic effects in diabetic mice. The homogenous nature of clonal mesenchymal stem cells may allow their clinical applications and open a new avenue through which to treat diabetic erectile dysfunction.

Chronic Cigarette Smoking Impairs Erectile Function through Increased Oxidative Stress and Apoptosis, Decreased nNOS, Endothelial and Smooth Muscle Contents in a Rat Model

Cigarette use is an independent risk factor for the development of erectile dysfunction (ED). While the association between chronic smoking and ED is well established, the fundamental mechanism(s) of cigarette-related ED are incompletely understood, partly due to no reliable animal model of smoking-induced ED. The present study was designed to validate an in vivo rat model of chronic cigarette-induced ED. Forty 12-week old male Sprague-Dawley rats were divided into 4 groups. Ten rats served as control group and were exposed only to room air. The remaining 30 rats were passively exposed to cigarette smoke (CS) for 4 weeks (n = 10), 12 weeks (n = 10), and 24 weeks (n = 10). At the 24-week time point all rats were assessed with intracavernous pressure (ICP) during cavernous nerve electrostimulation. Blood and urine were collected to measure serum testosterone and oxidative stress, respectively. Corporal tissue was assessed by Western blot for neuronal nitric oxide synthase (nNOS). Penile tissues were subjected to immunohistochemistry for endothelial, smooth muscle, and apoptotic content. Mean arterial pressure (MAP) was significantly higher in 24-week cigarette exposed animals compared to the control animals. Mean ICP/MAP ratio and cavernosal smooth muscle/endothelial contents were significantly lower in the 12- and 24-week rats compared to control animals. Oxidative stress was significantly higher in the 24-week cigarette exposed group compared to control animals. Mean nNOS expression was significantly lower, and apoptotic index significantly higher, in CS-exposed animals compared to control animals. These findings indicate that the rat model exposure to CS increases apoptosis and oxidative stress and decreases nNOS, endothelial and smooth muscle contents, and ICP in a dose dependent fashion. The rat model is a useful tool for further study of the molecular and cellular mechanisms of CS-related ED.

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.

Animal models of erectile dysfunction

Erectile dysfunction (ED) is a prevalent male sexual dysfunction with profound adverse effects on the physical and the psychosocial health of men and, subsequently, on their partners. The expanded use of various types of rodent models has produced some advances in the study of ED, and neurophysiological studies using various animal models have provided important insights into human sexual dysfunction. At present, animal models play a key role in exploring and screening novel drugs designed to treat ED.

Senescent Cells Impair Erectile Function through Induction of Endothelial Dysfunction and Nerve Injury in Mice

Erectile dysfunction (ED) is a major health problem, particularly in the elderly population, which is rapidly increasing. It is necessary to elucidate the mechanism by which ED occurs in the elderly. Cellular senescence is commonly detected in old tissues, and it is well known that senescent cells not only withdraw from the cell cycle but also remain viable and actively produce a variety of cytokines. We examined the effect of senescent cells on erectile function after injection of senescent cells into the penises of mice. Human umbilical vein endothelial cells were infected with an adenovirus expressing a constitutively active mutant of Ras to induce senescence, and were injected into the penises of nude mice. These senescent cells expressed proinflammatory cytokines such as interleukin-1β (IL-1β). Injection of senescent cells impaired erectile function, as assessed by the measurement of intracavernous pressure. Although the structure of the cavernous body did not remarkably change, expression of the catalytically active form of endothelial nitric oxide synthase and that of total neural nitric oxide synthase significantly decreased after injection. The penises injected with the senescent cells expressed human IL-1β and subsequently endogenous proinflammatory cytokines such as mouse IL-1β and tumor necrosis factor-α. These results suggested that senescent cells impaired erectile function through induction of endothelial dysfunction and nerve injury. These effects may be mediated by proinflammatory cytokines produced by senescent cells.

Prospects of stem cell treatment in benign urological diseases

Stem cells (SCs) are undifferentiated cells that are capable of self-renewal and differentiation and that therefore contribute to the renewal and repair of tissues. Their capacity for division, differentiation, and tissue regeneration is highly dependent on the surrounding environment. Several preclinical and clinical studies have utilized SCs in urological disorders. In this article, we review the current status of SC use in benign urological diseases (erectile dysfunction, Peyronie disease, infertility, and urinary incontinence), and we summarize the results of the preclinical and clinical trials that have been conducted.

Stem cell treatment of erectile dysfunction

Erectile Dysfunction (ED) is a common disease that typically affects older men. While oral type-5 phosphodieserase inhibitors (PDE5Is) represent a successful first-line therapy, many patients do not respond to this treatment leading researchers to look for alternative treatment modalities. Stem cell (SC) therapy is a promising new frontier for the treatment of those patients and many studies demonstrated its therapeutic effects. In this article, using a Medline database search of all relevant articles, we present a summary of the scientific principles behind SCs and their use for treatment of ED. We discuss specifically the different types of SCs used in ED, the methods of delivery tested, and the methods attempted to enhance SC therapy effect. In addition, we review the current preclinical literature on SC therapy for ED and present a summary of its findings in addition to the single clinical trial published.

Stem cell therapy for erectile dysfunction

Erectile dysfunction (ED) is an important health problem that has commonly been clinically treated using phosphodiesterase type 5 inhibitors (PDE5Is). However, PDE5Is are less effective when the structure of the cavernous body has been severely injured, and thus regeneration is required. Stem cell therapy has been investigated as a possible means for regenerating the injured cavernous body. Stem cells are classified into embryonic stem cells and adult stem cells (ASCs), and the intracavernous injection of ASCs has been explored as a therapy in animal ED models. Bone marrow-derived mesenchymal stem cells and adipose tissue-derived stem cells are major sources of ASCs used for the treatment of ED, and accumulated evidence now suggests that ASCs are useful in the restoration of erectile function and the regeneration of the cavernous body. However, the mechanisms by which ASCs recover erectile function remain controversial. Some studies indicated that ASCs were differentiated into the vascular endothelial cells, vascular smooth muscle cells, and nerve cells that originally resided in the cavernous body, whereas other studies have suggested that ASCs improved erectile function via the secretion of anti-apoptotic and/or proangiogenic cytokines rather than differentiation into other cell types. In this paper, we reviewed the characteristics of stem cells used for the treatment of ED, and the possible mechanisms by which these cells exert their effects. We also discussed the problems to be solved before implementation in the clinical setting.

Urine-derived stem cells: A novel and versatile progenitor source for cell-based therapy and regenerative medicine

Engineered functional organs or tissues, created with autologous somatic cells and seeded on biodegradable or hydrogel scaffolds, have been developed for use in individuals with tissue damage suffered from congenital disorders, infection, irradiation, or cancer. However, in those patients, abnormal cells obtained by biopsy from the compromised tissue could potentially contaminate the engineered tissues. Thus, an alternative cell source for construction of the neo-organ or functional recovery of the injured or diseased tissues would be useful. Recently, we have found stem cells existing in the urine. These cells are highly expandable, and have self-renewal capacity, paracrine properties, and multi-differentiation potential. As a novel cell source, urine-derived stem cells (USCs) provide advantages for cell therapy and tissue engineering applications in regeneration of various tissues, particularly in the genitourinary tract, because they originate from the urinary tract system. Importantly, USCs can be obtained via a non-invasive, simple, and low-cost approach and induced with high efficiency to differentiate into three dermal cell lineages.

A novel method to establish a rat ED model using internal iliac artery ligation combined with hyperlipidemia

Objective

To investigate a novel method, namely using bilateral internal iliac artery ligation combined with a high-fat diet (BCH), for establishing a rat model of erectile dysfunction (ED) that, compared to classical approaches, more closely mimics the chronic pathophysiology of human ED after acute ischemic insult.

Materials and Methods

Forty 4-month-old male Sprague Dawley rats were randomly placed into five groups (n = 8 per group): normal control (NC), bilateral internal iliac artery ligation (BIIAL), high-fat diet (HFD), BCH, and mock surgery (MS). All rats were induced for 12 weeks. Copulatory behavior, intracavernosal pressure (ICP), ICP/mean arterial pressure, hematoxylin-eosin staining, Masson's trichrome staining, serum lipid levels, and endothelial and neuronal nitric oxide synthase immunohistochemical staining of the cavernous smooth muscle and endothelium were assessed. Data were analyzed by SAS 8.0 for Windows.

Results

Serum total cholesterol and triglyceride levels were significantly higher in the HFD and BCH groups than the NC and MS groups. High density lipoprotein levels were significantly lower in the HFD and BCH groups than the NC and MS groups. The ICP values and mount and intromission numbers were significantly lower in the BIIAL, HFD, and BCH groups than in the NC and MS groups. ICP was significantly lower in the BCH group than in the BIIAL and HFD groups. Cavernous smooth muscle and endothelial damage increased in the HFD and BCH groups. Cavernous smooth muscle to collagen ratio, nNOS and eNOS staining decreased significantly in the BIIAL, HFD, and BCH groups compared to the NC and MS groups.

Conclusions

The novel BCH model mimics the chronic pathophysiology of ED in humans and avoids the drawbacks of traditional ED models.

Combined effects of brain-derived neurotrophic factor immobilized poly-lactic-co-glycolic acid membrane with human adipose-derived stem cells and basic fibroblast growth factor hydrogel on recovery of erectile dysfunction

Erectile dysfunction (ED) is the most frequent long-term problem after radical prostatectomy. We aimed to evaluate whether the use of combination therapy with basic fibroblast growth factor (bFGF)-hydrogel on corpus cavernosum and with adipose-derived stem cells (ADSCs) and brain-derived neurotrophic factor (BDNF)-immobilized poly-lactic-co-glycolic acid (PLGA) membrane on the cavernous nerve (CN) could improve erectile function in a rat model of bilateral cavernous nerve crush injury (BCNI). Rats were randomly divided into five groups (n=15 per group): a normal group (N group), a group receiving saline application after bilateral cavernous nerve crush injury (BCNI), a group undergoing bFGF-hydrogel injection in the corpus cavernosum after BCNI (bFGF), a group receiving ADSC application covered with BDNF-membrane after BCNI (ADSC/BDNF), and a group undergoing coadministration of bFGF-hydrogel injection and BDNF-membrane with ADSCs after BDNF (bFGF+ADSC/BDNF). Four weeks postoperatively, the erectile function was assessed by detecting the ratio of intracavernous pressure (ICP) to mean arterial pressure (MAP). Smooth muscle and collagen contents were measured using Masson's trichrome staining. Neuronal nitric oxide synthase (nNOS) expression in the dorsal penile nerve was detected by immunostaining. The protein expression of the α-smooth muscle actin (α-SMA) and the cyclic guanosine monophosphate (cGMP) level of the corpus cavernosum were quantified by western blot and cGMP assay, respectively. In the bFGF+ADSC/BDNF group, the erectile function was significantly elevated compared with the BCNI and other treated groups and showed a significantly increased smooth muscle/collagen ratio, nNOS content, α-SMA expression, and cGMP level. In particular, there were no statistical differences in the ICP/MAP ratio, smooth muscle/collagen ratio, and α-SMA and cGMP levels between the bFGF+ADSC/BDNF group and normal group. Application of the BDNF-immobilized PLGA membrane with human ADSC into the CN and bFGF-incorporated hydrogel into the corpus carvernosum improved nearly normal erectile function in a rat model of postprostatectomy ED. This result suggests that a combined application of bFGF+ADSC/BDNF might be a promising treatment for postprostatectomy ED.

Treatment of bladder dysfunction using stem cell or tissue engineering technique

Tissue engineering and stem cell transplantation are two important options that may help overcome limitations in the current treatment strategy for bladder dysfunction. Stem cell therapy holds great promise for treating pathophysiology, as well as for urological tissue engineering and regeneration. To date, stem cell therapy in urology has mainly focused on oncology and erectile dysfunction. The therapeutic potency of stem cells (SCs) was originally thought to derive from their ability to differentiate into various cell types including smooth muscle. The main mechanisms of SCs in reconstituting or restoring bladder function are migration, differentiation, and paracrine effects. Nowadays, paracrine effects of stem cells are thought to be more prominent because of their stimulating effects on stem cells and adjacent cells. Studies of stem cell therapy for bladder dysfunction have been limited to experimental models and have been less focused on tissue engineering for bladder regeneration. Bladder outlet obstruction is a representative model. Adipose-derived stem cells, bone marrow stem cells (BMSCs), and skeletal muscle-derived stem cells or muscle precursor cells are used for transplantation to treat bladder dysfunction. The aim of this study is to review stem cell therapy and updated tissue regeneration as treatments for bladder dysfunction and to provide the current status of stem cell therapy and tissue engineering for bladder dysfunction including its mechanisms and limitations.

Advances in Stem Cell Therapy for Erectile Dysfunction

Stem cell (SC) therapy for erectile dysfunction (ED) has been investigated in 35 published studies, with one being a small-scale clinical trial. Out of these 35 studies, 19 are concerned with cavernous nerve (CN) injury-associated ED while 10 with diabetes mellitus- (DM-) associated ED. Adipose-derived SCs (ADSCs) were employed in 18 studies while bone marrow SCs (BMSCs) in 9. Transplantation of SCs was done mostly by intracavernous (IC) injection, as seen in 25 studies. Allogeneic and xenogeneic transplantations have increasingly been performed but their immune-incompatibility issues were rarely discussed. More recent studies also tend to use combinatory therapies by modifying or supplementing SCs with angiogenic or neurotrophic genes or proteins. All studies reported better erectile function with SC transplantation, and the majority also reported improved muscle, endothelium, and/or nerve in the erectile tissue. However, differentiation or engraftment of transplanted SCs has rarely been observed; thus, paracrine action is generally believed to be responsible for SC’s therapeutic effects. But still, few studies actually investigated and none proved paracrine action as a therapeutic mechanism. Thus, based exclusively on functional outcome data shown in preclinical studies, two clinical trials are currently recruiting patients for treatment with IC injection of ADSC and BMSC, respectively.

Regenerative repair of damaged meniscus with autologous adipose tissue-derived stem cells

Mesenchymal stem cells (MSCs) are defined as pluripotent cells found in numerous human tissues, including bone marrow and adipose tissue. Such MSCs, isolated from bone marrow and adipose tissue, have been shown to differentiate into bone and cartilage, along with other types of tissues. Therefore, MSCs represent a promising new therapy in regenerative medicine. The initial treatment of meniscus tear of the knee is managed conservatively with nonsteroidal anti-inflammatory drugs and physical therapy. When such conservative treatment fails, an arthroscopic resection of the meniscus is necessary. However, the major drawback of the meniscectomy is an early onset of osteoarthritis. Therefore, an effective and noninvasive treatment for patients with continuous knee pain due to damaged meniscus has been sought. Here, we present a review, highlighting the possible regenerative mechanisms of damaged meniscus with MSCs (especially adipose tissue-derived stem cells (ASCs)), along with a case of successful repair of torn meniscus with significant reduction of knee pain by percutaneous injection of autologous ASCs into an adult human knee.

Isolation and passage of muscle-derived stem cells from the rat penile corpora cavernosa and induction of differentiation into smooth muscle cells

This study treated the isolation and passage of muscle-derived stem cells (MDSCs) from rat penile corpora cavernosa, detection of stem cell marker expression, observation of their self-renewal and continuous proliferation, and demonstration of their potential to differentiate into smooth muscle cells in co-culture. Muscle-derived stem cells from the rat penile corpora cavernosa were isolated and purified. The expression of stem cell markers Sca-1 and desmin was detected in PP6 cells, thus confirming that the main components of PP6 cells are MDSCs. The expression of Sca-1 and desmin occurred both in PP6 cells and cells at passages 3, 6, and 8, and there was no significant decrease in the expression level with increasing passage number. The growth curves indicated that the cell doubling time was approximately 48 h. The cells entered the stationary phase after approximately 7 days of culture. The proliferative activity of the cells at passage 8 remained unchanged. After 2 days of co-culture with smooth muscle cells, the DAPI-labeled MDSCs tended to exhibit smooth muscle cell morphology and expression of α-SMA was detected. MDSCs exist in the rat penile corpora cavernosa and possess the potential to differentiate into smooth muscle cells. This discovery serves as the basis in view of the potential use of endogenous stem cells for the treatment of erectile dysfunction (ED).

Stem-cell therapy for erectile dysfunction

INTRODUCTION

Stem cells (SCs) have been investigated for the treatment of erectile dysfunction (ED).

AREAS COVERED

This review covers key disease targets and all 33 preclinical studies, including their use of SC types, animal models, transplantation routes, and outcome assessment methods.

EXPERT OPINION

In the past one and half years there have been more stem-cell-for-erectile-dysfunction studies than the prior 8 years combined. These new studies tend to use combinatory treatment approaches by modifying or supplementing SCs with angiogenic or neurotrophic genes or proteins. However, when considering all risks and benefits, these combinatory approaches do not seem more advantageous than single-SC approaches. Another trend is the choice of transplantation routes other than the standard intracavernous (IC) injection. However, with the exception of intravenous injection, these new transplantation approaches are more cumbersome than IC injection and yet offer no evidence of producing better outcomes. In contrast to these variations, a consensus among these studies is the suggestion that paracrine action, as opposed to cellular differentiation, is the principal therapeutic mechanism. In conclusion, IC injection of a single SC type should be the choice protocol for initial clinical trials, and this is clearly the case with two clinical trials that are currently recruiting patients.

Stem cell therapy in bladder dysfunction: where are we? And where do we have to go?

To date, stem cell therapy for the bladder has been conducted mainly on an experimental basis in the areas of bladder dysfunction. The therapeutic efficacy of stem cells was originally thought to be derived from their ability to differentiate into various cell types. Studies about stem cell therapy for bladder dysfunction have been limited to an experimental basis and have been less focused than bladder regeneration. Bladder dysfunction was listed in MESH as "urinary bladder neck obstruction", "urinary bladder, overactive", and "urinary bladder, neurogenic". Using those keywords, several articles were searched and studied. The bladder dysfunction model includes bladder outlet obstruction, cryoinjured, diabetes, ischemia, and spinal cord injury. Adipose derived stem cells (ADSCs), bone marrow stem cells (BMSCs), and skeletal muscle derived stem cells (SkMSCs) are used for transplantation to treat bladder dysfunction. The main mechanisms of stem cells to reconstitute or restore bladder dysfunction are migration, differentiation, and paracrine effects. The aim of this study is to review the stem cell therapy for bladder dysfunction and to provide the status of stem cell therapy for bladder dysfunction.

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.

Intracavernous administration of bone marrow mononuclear cells: a new method of treating erectile dysfunction?

While PDE5 inhibitors have revolutionized treatment of ED, approximately 30% of patients are non-responsive. A significant cause of this is vascular and smooth muscle dysfunction, as well as nerve atrophy. Autologous administration of bone marrow mononuclear cells (BMMC) has been performed in over 2000 cardiac patients without adverse effects, for stimulation of angiogenesis/regeneration. Despite its ease of access, and dependence on effective vasculature for function, comparatively little has been perform in terms of BMMC therapy for ED. Here we outline the rationale for use of autologous BMMC in patients with ED, as well as provide early safety data on the first use of this procedure clinically.

Panax notoginseng saponins improve the erectile dysfunction in diabetic rats by protecting the endothelial function of the penile corpus cavernosum

Diabetes mellitus (DM)-associated ED is predominantly due to neurovascular dysfunction mediated by nitric oxide (NO) suppression. Panax notoginseng saponins (PNS) are widely used for treating cardiovascular disease in China. The aim of this study was to evaluate the effects of PNS on penile erection and corpus cavernosum tissues in rats with diabetes-associated ED. Four weeks after PNS treatment, erectile function was assessed by intracavernous pressure (ICP) and mean arterial pressure (MAP) measurements. The level of NO, cyclic guanosine monophosphate (cGMP) and advanced glycation end products (AGEs) in cavernous tissue were assessed. Immunohistochemical staining and TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) were performed for detecting endothelial NO synthase (eNOS) and apoptosis, respectively. The results show that ICP/MAP ratio was significantly increased in high-dose (150 mg kg(-1) per day) PNS-treated group compared with the diabetic ED untreated group (DM group). Compared with the untreated group, the expression of eNOS and the levels of NO and cGMP were increased in the PNS-treated groups. Moreover, apoptosis was markedly decreased in the group that received 150 mg kg(-1) per day of PNS. These results suggest that PNS may be used for improving the ED in diabetic rats via the NO/cGMP pathway and restores the function of endothelium in corpus cavernosum.

Erectile dysfunction in heart failure patients: a critical reappraisal

Heart failure (HF) is a complex clinical syndrome with a constantly increasing incidence and prevalence in western countries. Total absence of sexual activity is registered in 30% of HF patients. Moreover, HF-induced reduction in exercise tolerance, side effects of HF medications and the coexistence of shared risk factors between HF and sexual dysfunction may further aggravate the sexual health of HF patients. The purpose of this review is to examine the pathophysiological mechanisms behind the association of erectile dysfunction (ED) and HF, the potential therapeutic approaches and the eventual indications for sexual activity in HF patients. Medline and Cochrane Library search was performed from January 1970 through October 2012 to retrieve relevant papers outlining the association between ED and HF. Many evidences have outlined a tight association between ED and HF pathophysiological standpoint. Shared risk factors, common pathogenic traits and epidemiologic association represent some of the links between these conditions. Erectile dysfunction has been recognized as an earlier predictor of cardiovascular events; moreover, HF itself may cause and/or worsen ED because of its particular feature and co-morbidities. Furthermore, some cardiovascular drugs may contribute to impaired erectile function. In stable patients with stable HF, sexual activity is generally not contraindicated but it should be encouraged, as a form of moderate-intensity physical exertion. An effective treatment of ED in HF patients should be founded on the correction of reversible risk factors, on the choice of cardiovascular drugs with the lowest effect upon patient's erectile function, and on the use of phosphodiesterase-5-inhibitors. Physicians should be aware of the close relation between HF and ED and of the related clinical and therapeutic implications, in order to improve patients quality of life and clinical outcome.