Gene Therapy For Erectile Dysfunction Research Articles

Advances in Gene Therapy for Erectile Dysfunction: Promises and Challenges.

Erectile Dysfunction (ED) is one of the most common conditions affecting middle-aged and older men. Over the past few decades, oral phosphodiesterase type 5 inhibitors have been used to treat ED. However, these oral medications require on-demand access and are not effective in some hard-totreat populations. Moreover, there are no effective alternative treatments for ED. Based on results from preclinical models designed to provide long-term improvement of ED and other related conditions, gene therapy has shown great potential as a novel therapy for clinical management of ED. Gene therapy refers to the use of viral and non-viral vectors to deliver therapeutic genes to tissues via direct or transduced cell-mediated approaches. With the growing knowledge on the molecular mechanisms involved in the pathophysiology of ED, a number of therapeutic gene strategies have been extensively tested and proven to be effective in many animal models. However, only a few of them have been evaluated in clinical trials. This is due to safety concerns that need to be addressed before the clinical application can be considered. In this review, we summarize the key advancements in gene therapy for ED treatment, with an emphasis on the emerging stem cell-based approaches as well as other combinational strategies. The challenges facing the clinical application of gene therapy for ED treatment are also discussed.

Maintenance of the contractile phenotype in corpus cavernosum smooth muscle cells by Myocardin gene therapy ameliorates erectile dysfunction in bilateral cavernous nerve injury rats.

The pathophysiology of erectile dysfunction post radical prostatectomy is not clearly clarified, and the low efficacy of traditional PDE5i treatment remains a major complaint in contemporary practice. This study aimed to demonstrate phenotypic modulation in bilateral cavernous nerve injury (BCNI) rats within 7days, and subsequently validate gene therapy with Myocardin (Mycod) by maintaining a contractile phenotype in corpus cavernosum smooth muscle cells. Initially, 36 male rats were randomly divided into BCNI and negative control (NC) groups for histological and phenotypic molecular measurements at 3, 5, and 7days. Afterwards, an additional 30 rats received a single intra-cavernous injection of 50μL PBS, Ad-Myocd (1×1011 pfu/ml) or Ad-vector for 10 animals each, namely the NC+PBS, BCNI+Ad-Myocd, and BCNI+Ad-vector groups. Finally, the validity and mechanism of Myocd transfection was explored at 21days invivo and 48h invitro. Western blotting showed canonical declines in Myocd, α-SMA, and Calponin expression, as well as elevated Osteopontin (OPN) expression, before corporeal morphological and SM-to-collagen ratio changes at day 5 after injury. Overexpression of Myocd maintained the contractile phenotype of corpus cavernosum smooth muscle cells, ameliorated bilateral cavernous nerve injury rat erectile dysfunction, as well as promoted cell contractility and suppressed proliferative capacity. Simultaneously, confocal imaging revealed up-regulation and co-localization of serum response factor in gene-transferred cells. In conclusion, our study is the first to investigate corpus cavernosum smooth muscle cells phenotypes in the early stages of cavernous injury model rats, and Myocd reversed phenotypic modulation by activating serum response factor. The experimental results demonstrated the validity of gene therapy for erectile dysfunction.

AB028. Current status of pharmacotherapy for erectile dysfunction

The advent of phosphodiesterase type 5 (PDE5) inhibition as oral therapy has significantly revolutionized both clinical and basic research in the area of erectile dysfunction (ED). Much of this progress is due to a better understanding in the last three decades of the various pathophysiological and cellular mechanisms contributing to ED. Apart from the three available PDE5 inhibitors viz., sildenafil, tadalafil and vardenafil globally at the turn of this century, four other PDE inhibitors have joined the armament in recent time; these include avanafil, lodenafil, mirodenafil and udenafil. All seven PDE inhibitors are effective therapies for the treatment of ED in men. There is no significant difference among them with respect to efficacy, safety profile and tolerability. As such, good safety profiles have widened the horizon in patient choice, selectivity and efficacy. With the ease of oral administration and better patient compliance, other measures of the past, including intracavernosal injections and non-pharmacological treatments have been relegated to second-line therapy for most patients with ED. But, PDE inhibitors as first-line oral therapies are effective in about 75% of male patients diagnosed with ED. Intracavernous injection (IC) therapy with PGE1 (alprostadil) for about 10% patient-usage in general is a well-known effective and well tolerated treatment for men with ED. It is also recommended as a second line therapy for ED along with urethral and topical PGE1. Transurethral PGE1 is less effective compared to IC PGE1. Also the transurethral dosage options are 125 to 1,000 µg, while the IC dosage options are 5 to 40 µg. The topical PGE1 (300 µg in 100 mg of the cream) is also less effective compared to IC PGE1. Topical cream is not approved in many countries as yet. Other existing vasoactive agents such as papaverine, and alpha adrenergic blockers and their combinations and the ever increasing number of other agents in the pipeline including nitric oxide donors, guanylate cyclase activators, potassium channel openers and Rho-kinase inhibitors with the potential to overcome some limitations of the existing measures offer significant promise of clinical application in refractory and resistant cases. The TriMix preparations usually contain PGE1, papaverine and phentolamine in formulation compounded in pharmacies. Several clinical studies have also tested the efficacy of yohimbine, L-arginine, cyclic adenosine monophosphate activators, melanocortin-stimulating hormone analogs, endothelin antagonists in addition to vasoactive intestinal polypeptide and calcitonin gene related peptide with variable success rates. Trazodone, a serotonin antagonist and reuptake inhibitor was shown to improve premature ejaculation and erectile function in psychogenic cases of ED. Cloning of inducible nitric oxide synthase has opened a new era in the use of gene therapy for ED and the day for stem cells therapy and autologous penile tissue implants is not too far. Thus, ongoing research worldwide will continue to define new roles for various modalities targeted at specific sites in the erectile pathway and these advances will ultimately enable the clinicians to make the most appropriate therapeutic or other selections for individual patients including possible permanent reversal of organic 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.

AB045. Novel gene therapy for erectile dysfunction

ObjectiveErectile dysfunction (ED) is a major health problem that affects millions of men all around the world. Since a significant number of ED patients have a poor response to the first line oral phosphodiesterase 5 inhibitors, underlying treatment like gene therapy is needed to evolve as a promising solution.MethodsBasic and clinical researches regarding the application of gene therapy for ED over this few decades were reviewed. Then we summarize the state-of-the-art development of therapeutic targets, transfection methods, model systems and their efficacy in this field.ResultsAll gene therapy studies are still in preclinical phase except one clinical trial using the target of Ca2+-activated, large-conductance K+ channel. In basic researches, animal models of ED induced by aging, diabetes, cavernous nerve injury, hypertension, hypercholesterolemia have been utilized to evaluate the capacities and mechanisms of therapeutic targets to improve ED. In addition to the classic transfection methods like naked plasmid DNA, liposome and virus, new gene therapy vectors such as stem cells come into stage and present specific advantages. Besides, novel systems are invented to optimize the process of transfection. These researches demonstrate that current selected targets are widely involved in multiple erection related signaling pathways and all of them present exciting results. Although it is still in the stage of phase I, the clinical trial also reveals promising efficacy and primary safety.ConclusionsMore clinical trials are needed for potential targets to confirm their effects on ED patients. Although there is a long way to go before clinical application, gene therapy is an inspiring future treatment option for ED.

SaRNA Guided iNOS Up-Regulation Improves Erectile Function of Diabetic Rats

Promoter targeted saRNAs mediate sequence specific up-regulation of gene expression. We explored the therapeutic effect of RNA activation mediated iNOS gene activation on improving erectile function in a rat model of diabetes mellitus. An optimal saRNA sequence specific for iNOS promoter was cloned into an adenoviral vector, resulting in AdU6/shiNOS and AdU6/shControl. The corresponding viruses were used to transduce cultured rat cavernous smooth muscle cells. Streptozotocin induced diabetes models were established in rats and used to test the effects of intracavernous delivery of iNOS saRNA viruses on erectile function. iNOS expression in the cavernous smooth muscle cells or penile tissue of treated rats was assessed by reverse transcriptase-polymerase chain reaction and Western blot. Cyclic guanosine monophosphate was analyzed by enzyme-linked immunosorbent assay. Intracavernous pressure in response to cavernous nerve stimulation was measured using a data acquisition system on post-injection days 1, 3, 5, 7, 10 and 14. Adenovirus mediated expression of iNOS saRNA caused sustained up-regulation of iNOS in cavernous smooth muscle cells. Intracavernous injection of AdU6/shiNOS activated iNOS expression in vivo and significantly increased peak intracavernous pressure in streptozotocin induced diabetic rats via nitric oxide/intracellular cyclic guanosine monophosphate activation. Results show that saRNA mediated iNOS over expression in the penis can restore erectile function in streptozocin diabetic rats via the nitric oxide-cyclic guanosine monophosphate pathway.

Gene Therapy for Erectile Dysfunction: What Is the Future?

Gene transfer for the treatment of erectile dysfunction has completed phase 1 safety testing and has shown the necessary safety to proceed to the next level of clinical trial. This review focuses on the background of the components of that have led to US Food and Drug Administration acceptance of human gene transfer trials for nonlethal disease.

The inhibitive effect of shRNA on the phosphodiesterase type 5 in smooth muscle cells of rat corpus cavernosum

Objective To down-regulate the expression of phosphodiesterase type 5 (PDE5) gene by short hairpin RNA (shRNA) in smooth muscle cells of rat corpus cavernosum,and investigate the feasibility of gene therapy for erectile dysfunction (ED). Methods A recombinant adenovirus, rAd-rP-DE5-shRNA, targeting the PDE5 gene of rats was constructed. The rAd-rPDE5-shRNA was transfected into the smooth muscle cells of rat corpus cavernosum. The efficiency of transfection was evaluated by cell counting of EGFP expressed cells under fluorescence microscopy, and the expression of PDE5 gene was de-tected by RT-PCR and Western blot at the 48th h post-transfection. Results rAd-rPDES-shRNA was i-dentified and transfected at a MOI of 30 pfu per call for 48 h. The expression of PDE5 in the smooth mus-cle cells of rat corpus cavernosum was inhibited by (80.78±2.30)% at mRNA level, and (67.39± 3.33)% at protein level. Conclusion The shRNA delivered by the recombinant adenovirus can stably and effectively inhibit the expression of PDE5 in smooth muscle cells of rat corpus cavernosum. Key words: RNAi; Cavernous body of penis; Smooth muscle cells; PDE; Gene expression

A New Strategy, SuperEnzyme Gene Therapy in Penile Rehabilitation

Erectile dysfunction (ED) after radical prostatectomy (RP) is a very common condition. Prostacyclin (PGI(2)) is a prostaglandin with properties of vasodilation and anti-platelet aggregation. SuperEnzyme is a newly engineered protein with PGI(2) synthase activity that converts arachidonic acid directly to PGI(2). Transfection of SuperEnzyme into the penis to generate high levels of PGI(2) may increase penile blood inflow, alleviate hypoxia, and prevent apoptosis and fibrosis with potential use for ED after RP. The pathophysiology of ED after RP and the prostaglandin regulation was reviewed, and the possibly relevant mechanism of SuperEnzyme as a therapy for ED after RP was proposed. The rationale for SuperEnzyme as a possible therapy for ED after RP is analyzed. We reviewed the publications on the proposed pathophysiology of ED after RP, the molecular regulation of prostaglandin and methods of SuperEnzyme engineering and transfection. ED after RP is involved in hypoxia, apoptosis and fibrosis, mainly due to the cavernosal nerve injury. Transfection of SuperEnzyme into the penis of an animal model to produce PGI(2) is feasible. Animal studies with the use of SuperEnzyme gene therapy are needed to provide new insight into metabolic and signaling pathways of PGI(2) in the penis and the role of PGI(2) signaling in the recovery of erectile function after RP. SuperEnzyme may be a potential candidate as a gene therapy for ED after RP.

Gene therapy for the treatment of erectile dysfunction

Although oral phosphodiesterase 5 inhibitors have substantially improved the treatment of erectile dysfunction, unmet needs among men with erectile dysfunction still exist. This article considers the possibility of gene therapy for these patients, and discusses results from early clinical studies of gene therapy for erectile dysfunction.

Pathways to relaxation of corporal smooth muscle

Despite the development of effective oral phosphodiesterase type 5 (PDE5) inhibitors for treatment of erectile dysfunction (ED), millions of men remain refractory to this class of drug. Clearly, novel molecular targets in the corpus cavernosum smooth muscle (CCSM) need to be identified and evaluated for the potential in development of additional oral agents or gene therapy for ED. This review examines intracellular molecular mechanisms known to promote CCSM relaxation. In addition, this paper reviews CCSM contractile pathways, which when inhibited promote CCSM relaxation, along with the effects of various pathologies on the molecular components of these pathways. The data reviewed in this manuscript suggest that in addition to PDE5, there are numerous other “targetable” molecules in both the CCSM relaxation and contraction pathways that have the potential to lead to effective new therapeutic agents to treat ED in the near future.

Erectile Dysfunction in the Aging Man: Current Options for Treatment

Erectile dysfunction is more prevalent in aging males, and its occurrence is increased in the presence of associated cardiovascular comorbidities. Available treatments include a wide range of options to regain erectile function and thereby improve patients’ quality of life. Oral phosphodiesterase 5 inhibitors are considered to be the first line of therapy for the majority of causes of erectile dysfunction, due to their high efficacy, ease of use and acceptable safety profile. Second-line therapies include vacuum tumescence devices, intraurethral suppository or intracavernosal injections with various vasoactive agents. Penile prosthesis implantation has the highest rate of success but is reserved as a final treatment option due to cost, invasiveness and irreversibility. Gene therapy for erectile dysfunction is in the early stages of investigation and will require further basic clinical studies before being considered as a viable option. Overall, available treatment options for erectile dysfunction can successfully restore sexual function in most men. Future therapies will offer new categories of drugs that exploit novel mechanisms of action with even greater efficacy.

1417: Mesenchymal Stem Cells Alone or Modified with ENOS Restore Erectile Function in the Aged Rat: Cell-Based Gene Therapy for Erectile Dysfunction

You have accessJournal of UrologyDiscussed Poster, Tuesday, May 11, 2004, 8:00 am - 12:00 pm1 Apr 20041417: Mesenchymal Stem Cells Alone or Modified with ENOS Restore Erectile Function in the Aged Rat: Cell-Based Gene Therapy for Erectile Dysfunction Trinity J. Bivalacqua, Mustafa F. Usta, Hunter C. Champion, Weiwen Deng, Philip J. Kadowitz, and Wayne J.G. Hellstrom Trinity J. BivalacquaTrinity J. Bivalacqua More articles by this author , Mustafa F. UstaMustafa F. Usta More articles by this author , Hunter C. ChampionHunter C. Champion More articles by this author , Weiwen DengWeiwen Deng More articles by this author , Philip J. KadowitzPhilip J. Kadowitz More articles by this author , and Wayne J.G. HellstromWayne J.G. Hellstrom More articles by this author View All Author Informationhttps://doi.org/10.1016/S0022-5347(18)38642-7AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail "1417: Mesenchymal Stem Cells Alone or Modified with ENOS Restore Erectile Function in the Aged Rat: Cell-Based Gene Therapy for Erectile Dysfunction." The Journal of Urology, 171(4S), p. 373 © 2016 by American Urological AssociationFiguresReferencesRelatedDetails Volume 171Issue 4SApril 2004Page: 373 Advertisement Copyright & Permissions© 2016 by American Urological AssociationMetricsAuthor Information Trinity J. Bivalacqua More articles by this author Mustafa F. Usta More articles by this author Hunter C. Champion More articles by this author Weiwen Deng More articles by this author Philip J. Kadowitz More articles by this author Wayne J.G. Hellstrom More articles by this author Expand All Advertisement PDF DownloadLoading ...

Frontiers in gene therapy for erectile dysfunction.

Complete sequencing of the human genome has made possible a new age of molecular medicine. The utilization of sophisticated genomic technologies has important implications to the understanding, diagnosis and treatment of erectile dysfunction. This report will review one aspect of the impact of the genomic revolution on urology, to wit, the preclinical evidence emerging from several laboratories indicating that gene therapy for erectile dysfunction may well provide the first safe and effective application of gene therapy to the treatment of human smooth muscle disease. The molecular targets explored thus far have concentrated largely on manipulating various aspects of the nitric oxide/guanylate cyclase/cGMP system, although genetic modulation of growth factors, calcium sensitization mechanisms and potassium channel expression have also been explored. Cell-based gene therapy techniques are also being explored. The apparent preclinical success of virtually all of these gene-based strategies reflects the multifactorial nature of erectile disease as well as the numerous regulatory mechanisms available for restoring erectile capacity. While technical hurdles remain with respect to the choice of delivery vectors, molecular target validation and duration of efficacy, 'proof-of-concept' has clearly been documented. The ultimate goal of gene therapy is to provide a safe, effective and specific means for altering intracavernous pressure 'on demand', while simultaneously eliminating the necessity for other forms of therapy, and moreover, without altering resting penile function, or the physiology of other organ systems. It is in these arenas that the groundbreaking potential of gene transfer technology to the treatment of erectile dysfunction will be fully tested. In fact, the potential benefits of the application of gene transfer techniques to this important medical problem is just now beginning to be appreciated/recognized.

Gene therapy for erectile dysfunction: where is it going?

This review will summarize the most recent preclinical data from the leading US laboratories regarding the application of gene therapy to the treatment of erectile dysfunction. The implications of these findings in the field of gene therapy in general, and more specifically to the treatment of non-life threatening disorders such as erectile dysfunction, will be outlined. The preclinical work of several laboratories has clearly documented 'proof-of-concept' for the utility of gene therapy for the treatment of erectile dysfunction. A variety of vectors and several distinct molecular targets have been successfully leveraged. Such observations suggest that numerous potential strategies may exist for gene-based treatments of erectile dysfunction. The apparent preclinical success of most, if not all, gene-based strategies for the treatment of erectile dysfunction is consistent with the multifactorial regulatory mechanisms governing the erectile process. The bottleneck in the gene therapy clinical development process therefore apparently will not lie in the ability to identify relevant molecular targets that are amenable to gene therapy for erectile dysfunction, but rather in the safety, specificity and longevity of those targets. That is, the next technical hurdle is to find the strategy(ies) that has the best safety profile, the greatest specificity for altering (increasing) intracavernous pressure 'on demand' and, furthermore, the most appropriate (longest?) half-life. While these criteria may correspond to intuition, finding molecular targets that clear these clinical hurdles may place restrictions on the molecular choices for gene transfer.

Gene therapy: future therapy for erectile dysfunction.

Advances in molecular biological techniques, completion of the Human Genome Project, and the ensuing age of molecular medicine, in conjuction with the sum of a decades-long accumulation of knowledge of the physiology of erection and the pathophysiology of erectile dysfunction have converged to make gene therapy for erectile dysfunction a distinct possibility. In short, both the intrinsic complexities of mechanisms responsible for ensuring normal erection and the multifactorial nature of erectile dysfunction ensure that there is a relatively vast number of physiologically relevant molecular targets for gene therapy. As such, perhaps it is not surprising that virtually every preclinical gene therapy strategy/target examined thus far has been largely successful in ameliorating conditions associated with compromised erectile function in vivo and/or in vitro. This report highlights the goals and strategies of gene therapy for erectile dysfunction and reviews the strategies that initially have been employed. In short, the preclinical data, while still quite preliminary in many regards, are nonetheless quite impressive and encouraging. If similar success is obtained in clinical trials, gene therapy for erectile dysfunction may provide the first concrete "proof of concept" for using gene therapy in the treatment of human smooth muscle disorders.

Nitric oxide synthase gene therapy for erectile dysfunction: comparison of plasmid, adenovirus, and adenovirus-transduced myoblast vectors.

Nitric oxide (NO) has been recognized as an important transmitter for genitourinary tract function. This transmitter mediates smooth muscle relaxation and is essential for erection. The objective of our research was to determine whether overexpression of nitric oxide synthase (NOS) in the corpus cavernosum of the penis would correct erectile dysfunction. We introduced the inducible form of the enzyme NOS (iNOS) into the corpus cavernosum of adult (250-300 g) male Sprague-Dawley rats by injecting a solution of plasmid, adenovirus, or adenovirus-transduced myoblast cells (adeno-myoblast) (N = 3-5 each group). We also injected plasmid, adenovirus, and adeno-myoblast encoding the expression of the beta-gatactosidase reporter gene. We noted expression of beta-galactosidase throughout the corpora cavernosum after injection of each of the three solutions. Staining was greatest for adeno-myoblast followed by adenovirus and then plasmid. The basal intracavernous pressure (ICP) of iNOS-treated animals (adenovirus and adenovirus-transduced myoblast) increased to 55 +/- 23 cm H(2)O v 5 +/- 6 H(2)O in naive animals (P = 0.001). Stimulation of the cavernous nerve (15 Hz, 1.5 msec, 10-40 V, 1 min) resulted in a twofold increase in ICP (adenovirus and adeno-myoblast) from the basal level of the iNOS-treated animals. Direct in situ measurement of NO demonstrated release of 1 to 1.3 microM NO in the adeno-myoblast-treated penis. Myoblast-mediated gene therapy was more successful in delivering iNOS into the corpus cavernosum than were the direct adenovirus or plasmid transfection methods. Gene therapy of NOS may open new avenues of treatment for erectile dysfunction. Control of NOS expression would be necessary to prevent priapism.

ENDOTHELIAL CELL TRANSPLANTATION INTO THE CORPUS CAVERNOSUM: MOVING TOWARDS CELL-BASED GENE THERAPY

As a first step toward a cell based gene therapy for erectile dysfunction, we transplanted fluorescently labeled autologous microvessel endothelial cells (MVEC) into the rat corpus cavernosum. MVEC were isolated from the epididymal fat pad, labeled with the membrane intercalating dye PKH 26, and injected into the corpus cavernosum. Two to 15 days after transplantation the penises were removed, cryosectioned, and examined under epifluorescent and phase contrast microscopy. In 7 consecutive animals transplanted fluorescent cells were identified in the corpora cavernosa. Bilateral distribution was noted in each animal, and staining with ED1 determined that the fluorescence was not due to engulfment of the MVEC by phagocytic cells. Transplanted endothelial cells adhere and persist in the corporal sinusoids and provide a rationale for cell-based gene therapy in the penis.