Preliminary results of myoblast injection into the urethra and bladder wall: a possible method for the treatment of stress urinary incontinence and impaired detrusor contractility

Beyond collagen: injectable therapies for the treatment of female stress urinary incontinence in the new millennium

Previous experience with GAX-collagen has shown that the endoscopic correction of female SUI is both possible and effective. It is clear, however, that durability remains a primary concern when implementing this approach to treatment. The availability of recently developed and newly emerging materials, carefully designed using the tenets and techniques of biotechnology and materials science, may provide solutions to some of the difficulties beleaguering this treatment option. Results with currently available injectables are summarized in Table 1. Careful review and critical analysis of new bulking agents will soon reveal which materials approach the therapeutic ideal. It is likely that the ultimate choice of a particular substance, synthetic or biologic, may best be determined by the clinical circumstances involving the individual patient.

Review of the available urethral bulking agents

PURPOSE OF REVIEW

Newer tissue bulking agents used to treat stress urinary incontinence and vesicoureteral reflux provide for similar rates of success as older agents, but with greater safety and hopefully with greater durability. We review the new studies on the development and on the current trials of bulking agents.

RECENT FINDINGS

Recent reports suggest that periurethral bulking agents are as effective for genuine stress urinary continence as for intrinsic sphincter deficiency, expanding the indications for injectable agents to include patients desiring less invasive procedures due to personal preference or as a result of medical necessity. Newer bulking agents, Durasphere and Macroplastique, appear safe and as efficacious as older agents in early trials. Durability remains a question for these agents. Injectable tissue matrices and autologous cells may prove useful in the future.

SUMMARY

If durable and safe, these minimally invasive bulking agents may prove useful for all types of stress urinary incontinence. The price of minimal invasiveness may be lower efficacy, but their use does not compromise further therapy, should it be needed.

Gene therapy and tissue engineering for urologic dysfunction: status and prospects

This article reviews the recent advances in gene therapy and tissue engineering for urologic dysfunction. Although the number of gene therapy-based clinical trials has increased dramatically in the field of urologic oncology, such trials are still few within the neurourologic field. Recently, new biologic approaches employing growth factors have been utilized to treat various pathological conditions. Among them, transfer of genes such as those encoding growth factors represents a promising way to deliver therapeutic proteins to malfunctioning tissues, which leads to the improvement of organ function. Tissue engineering, which may eventually be combined with gene therapy, also offers the potential to create new functional genitourinary tissue for regeneration and replacement of tissue lost as a consequence of disease. Thus, both tissue engineering and gene therapy may hold promising new solutions in the urologic field.

Autologous primary muscle-derived cells transfer into the lower urinary tract

The goal of these experiments was to establish the basic methodology for future clinical applications of muscle-derived cells (MDC) tissue engineering and gene transfer for the treatment of urological dysfunction. Primary MDC isolated via preplating techniques from adult female SD rats were transduced with retrovirus encoding the expression of beta-galactosidase reporter gene. The MDC were injected into the right and left lateral walls of the bladder and proximal urethra of the autologous animals (n = 6) with a 10 microl Hamilton micro syringe. The amount of injected MDC ranged from 1 to 2 x 10(6) cells. The injected tissue was harvested after 7, 14, and 28 days, sectioned and examined histologically for beta-galactosidase and immunohistochemically for fast myosin heavy chain specific to skeletal muscle. The tissues were also stained for anti-CD4 and anti-CD8 antibodies to assess for cellular immune reaction. We have detected a large number of autologous MDC expressing beta-galactosidase and positively stained for fast myosin heavy chain in the bladder and urethral wall. Many injected myoblasts and myotubes were also seen in the bladder and urethral wall at each time point. Staining of lymphocytes with anti-CD4 and anti-CD8 antibodies was negative after MDC injection at each time point. We have demonstrated the long-term survival of autologous MDC and MDC mediated gene transfer into the bladder and urethral wall. Autologous MDC and MDC mediated gene transfer may be a promising treatment to augment bladder and urethral sphincter function.

Gene therapy strategies for urological dysfunction

Novel molecular techniques such as conventional and ex vivo gene therapy, and tissue engineering have only recently been introduced to the field of urology. The lower urinary tract is ideally suited for minimally invasive therapy, and also ex vivo approaches would limit the risk of systemic side effects. Muscle-derived stem cells have been used successfully to treat stress incontinence, and rats with diabetic bladder dysfunction benefited from nerve growth factor (NGF)-based gene therapy. Nitric oxide synthase and capase-7 might provide suitable gene therapy targets for erectile dysfunction and benign prostatic hyperplasia, respectively.

Pubovaginal slings: a review of the technical variables

The pubovaginal sling, reintroduced in the late 1970s by Maguire and Blaivas, has become the gold standard for managing anatomic incontinence. Newer technology, materials, surgical techniques and even new theories on the mechanism of action are evolving to further reduce the morbidity of these procedures and improve patient satisfaction. In the following review, we will highlight some of the exciting advances we have witnessed over the last year and try to put them into perspective for the reader.

Basic science research on the urinary bladder and interstitial cystitis: new genetic approaches

This article summarizes recent genetic research that promises to advance understanding of the functioning of the urinary bladder and further our knowledge about interstitial cystitis. Results reported at the Tenth International Research Symposium on Interstitial Cystitis and Bladder Research and in the current literature are presented. Three specific areas of genetic research are summarized: gene expression via DNA arrays, development of new animal models through transgenic or gene knockout approaches, and gene therapy. Advances in genetic research (specifically in gene therapy; development of new, genetically engineered mouse models; and study of gene expression using DNA array assays) will contribute to further understanding the functioning of the urinary bladder in health and disease.

Persistence and survival of autologous muscle derived cells versus bovine collagen as potential treatment of stress urinary incontinence

PURPOSE

We explored the use of autologous muscle derived cells as a method of treating stress urinary incontinence. We determined whether urethral muscle derived cell injection is feasible and compared it with bovine collagen injection.

MATERIALS AND METHODS

Muscle derived cells isolated from female Sprague-Dawley rats were first transduced with retrovirus carrying the transgene for beta-galactosidase. We injected approximately 1 to 1.5 x 106 cells into the bladder wall and proximal urethra of 6 autologous animals. Tissue was harvested after 3 and 30 days, sectioned, stained for fast myosin heavy chain and assayed for beta-galactosidase. To compare muscle derived cell and bovine collagen injections 100 microl. of commercially available bovine collagen were also injected in Sprague-Dawley female rats. Tissue was harvested in 3 animals each after 3 and 30 days, sectioned and stained for trichrome. Subsequently, 3 adult SCID mice were used to compare the level of transgene expression at each time point after injecting 1.5 x 106 cells per injection, which were transduced with adenovirus carrying the transgene for beta-galactosidase.

RESULTS

A large number of cells expressing beta-galactosidase were observed in the bladder and urethral wall 3 and 30 days after autologous cell injection in Sprague-Dawley rats. The persistence of primary muscle derived cells at 3 days was similar to that of collagen. However, at 30 days there was significant cell persistence while only a minimal amount of injected bovine collagen was detectable. Approximately 88% of the beta-galactosidase expression at day 3 remained at day 30 in SCID mice.

CONCLUSIONS

We present 2 new findings important for the emerging field of urological tissue engineering, including the feasibility of injecting autologous skeletal muscle derived cells into the lower urinary tract and the greater persistence of such injected cells versus injected bovine collagen. Therefore, autologous muscle derived cell injection may be an attractive alternative treatment option for stress urinary incontinence.

Lower urinary tract physiology and pharmacology

This review focuses on what we consider to be the most important findings of the last year relating to the smooth muscle of the lower urogenital system and the different levels of regulation that control its contraction and relaxation. One level is through modulation of the smooth muscle itself or its environment. Recent findings examining myosin isoform composition and collagen content as well as mechanisms that appear to be involved in inducing hyperplasia/hypertrophy of smooth muscle are described. Another method of regulation is via calcium-dependent phosphorylation of the regulatory light chain of myosin, which increases its activity. Interesting results indicating an uncoupling of force from calcium in the bladder are discussed. A third level of regulation is pharmacologic. Thus, the most recent findings related to receptor subtypes, including muscarinic, endothelin, alpha-adrenergic and nicotinic receptors, are presented. In addition, the effects of diabetes, incontinence, and partial bladder outlet obstruction on these modes of contractile regulation are also discussed.

Detection of a progesterone-dependent secretory protein synthesized by cat endometrium

Uterine flushings and culture media from endometrial explants incubated in the presence of radiolabeled amino acids were analyzed using one-(1-D) and two-dimensional (2-D) gel electrophoresis to identify proteins synthesized by the endometrium and subsequently released into the uterine lumen. 1-D and 2-D analyses of uterine flushings and culture media of endometrial explants obtained from 7- to 11-day pregnant cats (pre-implantation) showed a Mr 30,000 protein that appeared on 2-D gels as a family of macromolecules with isoelectric points between 6.5 and 7.0. This family of macromolecules was also present in the culture media of implantation-site tissue obtained from 12- to 16-day pregnant cats and of nonimplantation-site endometrium obtained form 12- to 28-day pregnant cats. The Mr 30,000 protein was absent in uterine flushings and culture media from estrous and 3- to 5-day-pregnant cats. In ovariectomized, steroid-treated animals, the Mr 30,000 protein was only detected in flushings and media from those animals treated with progesterone, regardless of the presence or absence of estradiol-priming and/or simultaneous estradiol treatment. In daily flushings obtained from ovariectomized, steroid-treated cats equipped with an indwelling uterine catheter, the Mr 30,000 protein was absent during the 14 days of estradiol treatment and was first detected 3-4 days after the onset of estradiol plus progesterone treatment. This protein was not detected in serum from estrous, 9-day pregnant, ovariectomized, and ovariectomized, steroid-treated animals. This study shows that 1) a progesterone-dependent protein, with an approximate molecular weight of 30,000 and an isoelectric point of 6.5-7.0, first appears within the uterine lumen soon after the arrival of the blastocyst and continues to be present during implantation; 2) the synthesis and release of the Mr 30,000 protein is dependent on progesterone regardless of the presence or absence of estradiol; and 3) the onset of secretion of the Mr 30,000 protein requires 3-4 days of continuous progesterone treatment in the estradiol-primed cat.