Purinergic Signaling and its Role in the Stem Cell Differentiation

Purinergic signaling is a mechanism in which extracellular purines and pyrimidines interact with specialized cell surface receptors known as purinergic receptors. These receptors are divided into two families of P1 and P2 receptors, each responding to different nucleosides and nucleotides. P1 receptors are activated by adenosine, while P2 receptors are activated by pyrimidine and purines. P2X receptors are ligand-gated ion channels, including seven subunits (P2X1-7). However, P2Y receptors are the G-protein coupled receptors comprising eight subtypes (P2Y1/2/4/6/11/12/13/14). The disorder in purinergic signaling leads to various health-related issues and diseases. In various aspects, it influences the activity of non-neuronal cells and neurons. The molecular mechanism of purinergic signaling provides insight into treating various human diseases. On the contrary, stem cells have been investigated for therapeutic applications. Purinergic signaling has shown promising effect in stem cell engraftment. The immune system promotes the autocrine and paracrine mechanisms and releases the significant factors essential for successful stem cell therapy. Each subtype of purinergic receptor exerts a beneficial effect on the damaged tissue. The most common effect caused by purinergic signaling is the proliferation and differentiation that treat different health-related conditions.

Tissue Engineering and Stem Cell Therapy in Neurogenic Bladder Dysfunction: Current and Future Perspectives

Tissue engineering (TE) is a rapidly evolving biomedical discipline that can play an important role in treating neurogenic bladder dysfunction and compensating for current conventional options' shortcomings. This review aims to analyze the current status of preclinical and clinical trials and discuss what could be expected in the future based on the current state of the art. Although most preclinical studies provide promising results on the effectiveness of TE and stem cell therapies, the main limitations are mainly the very slow translation of preclinical trials to clinical trials, lack of quality research on neurogenic preconditions of neurogenic bladder dysfunction outside of the spinal cord injury and varying therapeutic methods of the existing research that lacks a standardized approach.

Therapeutic effect of adipose-derived regenerative cells on bladder function in rats with underactive bladder

We examined the effect of adipose-derived regenerative cells (ADRC) on bladder functions in a rat model of detrusor underactivity (DU) induced by bladder over-distention. Adult female Sprague Dawley rats were divided into 3 groups: sham group (control); over-distention group; and over-distention with ADRC treatment group. Bladder was over-distended with saline (2.7mL) on day 1, 8, 15 and 22 of the study. ADRCs, which were harvested from male F344 rats, expanded via culture, were injected into the bladder wall at day 15. Cystometry and in vitro organ bath functional studies were performed on day 28. Moreover, histological assessment of the bladder was performed. In cystometry, significant prolongation of the inter-contraction interval (ICI) and decrease of voiding efficiency (VE) were observed in the over-distention group, compared to that in the control group. Significant improvement in ICI and VE was seen in the ADRC treatment group in comparison with the over-distention group. The over-distention group showed significantly weaker bladder contractile responses to carbachol and electrical field stimulation than the control group, while bladder contractile responses were significantly stronger in the ADRC treatment group than that in the over-distention group. The over-distention group showed substantial fibrosis of the bladder compared to the control group, whereas bladder fibrosis was alleviated in the ADRC treatment group. In conclusion, the injection of ADRC into bladder wall improved bladder dysfunction and histological changes induced by bladder over-distention. ADRCs-based regenerative therapy could be novel treatment for DU.

Detrusor Underactivity and the Underactive Bladder: A Systematic Review of Preclinical and Clinical Studies

CONTEXT

Detrusor underactivity (DUA) is a common but relatively under-researched bladder dysfunction. Underactive bladder (UAB) is the symptom-based correlate of DUA. Recently, there has been renewed interest in this topic.

OBJECTIVE

To systematically review and summarise the most recent literature and discuss this in the context of what is already known.

EVIDENCE ACQUISITION

A systematic review of the literature was performed in December 2017 using Medline and Scopus databases. Separate searches of each database used a complex search strategy including "free text" protocols. Search terms included "underactive bladder", "detrusor underactivity", "acontractile bladder", "detrusor failure", "detrusor areflexia", "atonic bladder", "chronic retention", and "impaired bladder contractility".

EVIDENCE SYNTHESIS

The initial search retrieved a total of 1690 studies; of these 44 were included in the final analyses.

CONCLUSIONS

Although there has been an expansion in the literature concerning all aspects of DUA and UAB, knowledge on its epidemiology and aetiopathogenesis is still lacking; there remains a need to develop accurate reproducible diagnostic criteria and effective treatments, in particular drug therapies.

PATIENT SUMMARY

Recently, there has been renewed interest in underactive bladder with expanding research in this area. The lack of simple, reproducible, noninvasive diagnostic criteria has precluded an accurate estimation of the magnitude of the problem. Recent studies have highlighted the potential role of impaired bladder blood supply in causing bladder underactivity.

Effect of TRPV4 activation in a rat model of detrusor underactivity induced by bilateral pelvic nerve crush injury

AIMS

To produce an animal model of peripheral neurogenic detrusor underactivity (DU) and to evaluate the effect of TRPV4 receptor activation in this DU model.

METHODS

In female Sprague-Dawley rats, bilateral pelvic nerve crush (PNC) was performed by using sharp forceps. After 10 days, awake cystometrograms (CMG) were recorded in sham and PNC rats. A TRPV4 agonist (GSK 1016790A) with or without a TRPV4 antagonist (RN1734) were administered intravesically and CMG parameters were compared before and after drug administration in each group. The TRPV4 transcript level in the bladder mucosa and histological changes were also evaluated.

RESULTS

In CMG, PNC rats showed significant increases in intercontraction intervals (ICI), number of non-voiding contractions (NVCs), baseline pressure, threshold pressure, bladder capacity, voided volumes, and post-void residual (PVR) compared to sham rats. Contraction amplitude and voiding efficiency were significantly decreased in PNC rats. In PNC rats, intravesical application of GSK1016790A (1.5 μM) significantly decreased ICI, bladder capacity, voided volume, and PVR without increasing NVCs, and these effects were blocked by RN1734 (5.0 μM). In contrast, 1.5 μM GSK1016790A had no significant effects on CMG parameters in normal rats. TRPV4 expression within the bladder mucosa of PNC rats was increased in association with urothelial thickening.

CONCLUSIONS

Rats with bilateral PNC showed characteristics of DU, and this model seems appropriate for further evaluation of peripheral neurogenic mechanisms of DU. Also, TRPV4 receptors, the activation of which reduced bladder capacity and PVR, could be a target for DU treatment.

Stem cell in urology-are we at the cusp of a new era?

Stem cell therapy can potentially disrupt conventional medicine as we practice it today. Stem cells can self-renew and differentiate and by this, repair and in certain conditions regenerate damaged tissue. In the past two decades, there has been significant research into its value in several chronic urological conditions for which conventional therapy is unsatisfactory. Stem cell therapy has been tried on animal models of bladder dysfunction, stress urinary incontinence (SUI), erectile dysfunction and urethral injury and certain preclinical studies have had very encouraging results. Yet despite this explosion of knowledge about the nature and value of stem cells, translation of research into the clinical domain has been slow. In addition, lack of regulation of stem cell therapy has resulted in indiscriminate, unscientific administration of stem cell therapy to patients. This review looks into the advances in the use of stem cells in urological practice, the recent regulatory guidelines that have been introduced and what the future holds for this exciting branch.

Current concepts of the acontractile bladder

The acontractile bladder (AcB) is a urodynamic-based diagnosis wherein the bladder is unable to demonstrate any contraction during a pressure flow study. Although it is often grouped with underactive bladder, it is a unique phenomenon and should be investigated independently. The purpose of the present review was to examine the current literature on AcB regarding its pathology, diagnosis, current management guidelines, and future developments. We performed a review of the PubMed database, classifying the evidence for AcB pathology, diagnosis, treatment, and potential future treatments. Over the 67 years covered in our review period, 42 studies were identified that met our criteria. Studies were largely poor quality and mainly consisted of retrospective review or animal models. The underlying pathology of AcB is variable with both neurological and myogenic aetiologies. Treatment is largely tailored for renal preservation and reduction of infection. Although future developments may allow more functional restorative treatments, current treatments mainly focus on bladder drainage. AcB is a unique and understudied bladder phenomenon. Treatment is largely based on symptoms and presentation. While cellular therapy and neuromodulation may hold promise, further research is needed into the underlying neuro-urological pathophysiology of this disease so that we may better develop future treatments.

Suppression of Oxidative Stress of Modified Gongjin-Dan (WSY-1075) in Detrusor Underactivity Rat Model Bladder Outlet Induced by Obstruction

OBJECTIVE

To investigate the anti-oxidative stress and preventive effect of modified Gongjin-dan (WSY-1075) in a detrusor underactivity rat model.

METHODS

Rats were randomly allocated to three groups: shamoperated (control), bladder outlet obstruction-induced detrusor underactivity (BOO-DU), and BOO-DU with WSY-1075 (WSY) groups. WSY-1075 was orally administrated to rats 200 mg daily for 2 weeks prior to the operation and 4 weeks after the operation. Bladder outlet obstruction was surgically induced in rats by ligation around the urethra avoiding total obstruction. Cystometrography was conducted on rats in each group for examination of bladders.

RESULTS

Compared with the control group, bladder outlet obstruction led to a significant increase in oxidative stress with consequent changes to molecular composition, and decrease in maximal detrusor pressure (P<0.05). WSY-1075 treatment significantly suppressed oxidative stress and prevented degenerative and dysfunctional changes in bladder, as compared with BOO-DU group (P<0.05).

CONCLUSION

WSY-1075 had beneficial effect on prevention of BOO-DU.

Can bladder fibrosis in congenital urinary tract obstruction be reversed?

A variety of conditions exists in adults and children in which functional or anatomical urinary tract obstructions cause bladder fibrosis, which reduces the bladder's ability to store and empty urine. Current surgical procedures include removal of the obstructions to facilitate bladder emptying or prompt prenatal or postnatal spinal closure to prevent further neurogenic damage. Bladder fibrosis may occur, and it can get worse if a flow hindrance persists or deteriorates. Anti-fibrotic therapeutic strategies that target a variety of factors have been developed in animal models, but currently there are no anti-fibrotic therapies available for clinical use. This review examines the pathogenesis of bladder fibrosis that is caused by congenital obstructions of the lower urinary tract, and it focuses on the principal signalling factors and potential treatment modalities.

Effects of an EP2 and EP3 Receptor Dual Agonist, ONO-8055, on a Radical Hysterectomy-Induced Underactive Bladder Model in Monkeys

OBJECTIVES

The objective was to develop an underactive bladder (UAB) model in primates and to evaluate the potential of prostanoid EP2 and EP3 receptor dual agonist ONO-8055 to become a therapeutic agent for UAB.

METHODS

A surgical procedure resembling radical hysterectomy was performed on female cynomolgus monkeys. Subsequently, in vitro muscle strip studies were performed using bladder muscle strips from normal monkeys and monkeys that underwent surgery. In addition, uroflowmetric data were obtained at specified days after the surgery. To evaluate the effects of ONO-8055 and distigmine (DIS) on voiding function in the UAB monkey model, uroflowmetry was performed approximately 1 week after the surgery, before and after the cumulative intravenous administration of the compounds at 2 h intervals.

RESULTS

In the bladder muscle strip studies, the responses to potassium chloride at 2 months, and carbachol and electrical field stimulation from 2 weeks decreased significantly. Voided volume (VV), maximum flow rate (Qmax), and average flow rate (Qave) decreased after surgery, while voiding time (VT) increased. In this model, ONO-8055 and DIS significantly increased VV and Qmax. DIS prolonged VT, while ONO-8055 had no effect. The results also showed that ONO-8055 increased Qave.

CONCLUSIONS

We developed a neurogenic UAB model in primates. As ONO-8055 improved voiding function in this model to at least the same degree as DIS, this EP2 and EP3 receptor dual agonist has the potential to be a candidate for neurogenic UAB pharmacotherapy.

Bone marrow mesenchymal stem cell therapy for voiding dysfunction

Lower urinary tract symptoms can significantly impact quality of life. Current standard treatments are not always effective and are associated with complications and side effects. The discovery of stem cells led to research into cell-based therapies for treatment of disorders of voiding dysfunction. Bone marrow mesenchymal stem cells are particularly promising given their ability to differentiate into a variety of cell types. Recent studies have investigated bone marrow stem cells to treat a number of functional voiding pathologies including bladder outlet obstruction, neurogenic bladder, and stress urinary incontinence. Experiments in tissue regeneration have also attempted to create artificial bladders and urethras. The purpose of this article is to critically review the literature regarding the use of bone marrow mesenchymal stem cells in treatment of voiding dysfunction.

Translational approaches to the treatment of benign urologic conditions in elderly women

PURPOSE OF REVIEW

Stress urinary incontinence, overactive bladder, interstitial cystitis/painful bladder syndrome, and underactive bladder are highly prevalent among elderly women, and have significant impact on quality of life; however, existing treatments are limited and are not always successful for all patients. Researchers are investigating a multitude of new therapies to treat these conditions. This review will summarize the recent literature on investigative therapies for these conditions.

RECENT FINDINGS

Multiple new treatments are being developed for lower urinary tract dysfunction. Some of these treatments, including balloon therapy and muscle-derived stem cells for stress urinary incontinence, could provide alternatives to existing therapies. Others require further research before being used in patients, such as pudendal nerve stimulation for overactive bladder and intravesical liposomes for drug delivery in interstitial cystitis/painful bladder syndrome.

SUMMARY

Multiple new therapies are being investigated that could provide clinicians with additional tools to treat lower urinary tract disorders in millions of elderly women.

Potential of stem cell treatment in detrusor dysfunction

The current treatments of bladder dysfunctions, such as bladder overactivity and impaired ability to empty, have limitations, and new treatment alternatives are needed. Stem cell transplantation and tissue engineering have shown promising results in preclinical studies. Stem cells were originally thought to act by differentiating into various cell types, thereby replacing damaged cells and restoring functional deficits. Even if such a mechanism cannot be excluded, the current belief is that a main action is exerted by the stem cells secreting bioactive factors that direct other stem cells to the target organ. In addition, stem cells may exert a number of other effects that can improve bladder dysfunction, since they may have antiapoptotic, antifibrotic, and immunomodulatory properties, and can induce neovascularization. Tissue engineering for bladder replacement, which has had varying success in different animal species, has reached the proof-of-concept state in humans, but recent research suggests that the present approaches may not be optimal. Further studies on new approaches, using animal models with translational predictability, seem necessary for further progress.

Application of Nanoscaffolds in Mesenchymal Stem Cell-Based Therapy

Regenerative medicine is an alternative solution for organ transplantation. Stem cells and nanoscaffolds are two essential components in regenerative medicine. Mesenchymal stem cells (MSCs) are considered as primary adult stem cells with high proliferation capacity, wide differentiation potential, and immunosuppression properties which make them unique for regenerative medicine and cell therapy. Scaffolds are engineered nanofibers that provide suitable microenvironment for cell signalling which has a great influence on cell proliferation, differentiation, and biology. Recently, application of scaffolds and MSCs is being utilized in obtaining more homogenous population of MSCs with higher cell proliferation rate and greater differentiation potential, which are crucial factors in regenerative medicine. In this review, the definition, biology, source, characterization, and isolation of MSCs and current report of application of nanofibers in regenerative medicine in different lesions are discussed.

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.

[Stem cell therapy and tissue engineering in regenerative urology]

BACKGROUND

So far there is no clinically established, effective tissue engineering therapy for dysfunction or defects of the lower urinary tract. The concentration of experimental data, initial clinical studies and individual case reports underlines that stem cell treatment for bladder storage and voiding problems, erectile dysfunction and other urothelial defects of the lower urinary tract could close the gap between individualized therapy and potential biomedical applications.

RESULTS

As a result of fundamental research work over the last decade a characterization of various stem cell populations and evaluation of different urological therapy options could be performed. Thereby, aspects of optimal administration, migration, secretion of bioactive factors and stage of differentiation of stem cells with respect to an improved efficiency of treatment were investigated. Because successful tissue regeneration depends on angiogenesis and innervation, particular attention was paid to these important factors.

CONCLUSIONS

Various clinical indications for stem cell treatment and tissue reconstruction that may be required after radical prostatectomy, such as stress urinary incontinence, urethral reconstruction and erectile dysfunction have materialized and are currently being verified in preclinical studies and phase I trials.

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.

Urine is a highly cytotoxic agent: does it influence stem cell therapies in urology?

The state of art of stem cell therapies in urologic regenerative medicine is still under development. There are still many issues before advances in tissue engineering can be introduced for clinical application. The essential question is whether stem cells should be seeded on the urinary tract lumen side. The present experiment, using Real-Time Cell Analyzer (RTCA) DP (Dual Plate) of the xCellligence system (Roche Applied Science, Mannheim, Germany), allowed us to monitor cellular events in real time. In this study we examined the influence of urine on bone marrow-derived mesenchymal stem cells (MSC). Cells were exposed to medium mixed with urine (1:1), medium mix with PBS (Phosphate Buffered Saline) (1:1), only urine, and whole medium without cells as background. The cell number was significantly lower in all groups exposed on medium mixed with urine and urine alone. The results showed that urine is a highly cytotoxic agent whose role in urologic regenerative medicine is underestimated.

Tissue engineering for the oncologic urinary bladder

Urinary diversion after radical cystectomy in patients with bladder cancer normally takes the form of an ileal conduit or neobladder. However, such diversions are associated with a number of complications including increased risk of infection. A plausible alternative is the construction of a neobladder (or bladder tissue) in vitro using autologous cells harvested from the patient. Biomaterials can be used as a scaffold for naturally occurring regenerative stem cells to latch onto to regrow the bladder smooth muscle and epithelium. Such engineered tissues show great promise in urologic tissue regeneration, but are faced with a number of challenges. For example, the differentiation mesenchymal stem cells from various sources can be difficult and the smooth muscle cells formed do not precisely mimic the natural cells.

Stem cell therapy for voiding and erectile dysfunction

Voiding dysfunction comprises a variety of disorders, including stress urinary incontinence and overactive bladder, and affects millions of men and women worldwide. Erectile dysfunction (ED) also decreases quality of life for millions of men, as well as for their partners. Advanced age and diabetes are common comorbidities that can exacerbate and negatively impact upon the development of these disorders. Therapies that target the pathophysiology of these conditions to halt progression are not currently available. However, stem cell therapy could fill this therapeutic void. Stem cells can reduce inflammation, prevent fibrosis, promote angiogenesis, recruit endogenous progenitor cells, and differentiate to replace damaged cells. Adult multipotent stem cell therapy, in particular, has shown promise in case reports and preclinical animal studies. Stem cells also have a role in urological tissue engineering for ex vivo construction of bladder wall and urethral tissue (using a patient's own cells) prior to transplantation. More recent studies have focused on bioactive factor secretion and homing of stem cells. In the future, clinicians are likely to utilize allogeneic stem cell sources, intravenous systemic delivery, and ex vivo cell enhancement to treat voiding dysfunction and ED.

Perspectives of purinergic signaling in stem cell differentiation and tissue regeneration

Replacement of lost or dysfunctional tissues by stem cells has recently raised many investigations on therapeutic applications. Purinergic signaling has been shown to regulate proliferation, differentiation, cell death, and successful engraftment of stem cells originated from diverse origins. Adenosine triphosphate release occurs in a controlled way by exocytosis, transporters, and lysosomes or in large amounts from damaged cells, which is then subsequently degraded into adenosine. Paracrine and autocrine mechanisms induced by immune responses present critical factors for the success of stem cell therapy. While P1 receptors generally exert beneficial effects including anti-inflammatory activity, P2 receptor-mediated actions depend on the subtype of stimulated receptors and localization of tissue repair. Pro-inflammatory actions and excitatory tissue damages mainly result from P2X7 receptor activation, while other purinergic receptor subtypes participate in proliferation and differentiation, thereby providing adequate niches for stem cell engraftment and novel mechanisms for cell therapy and endogenous tissue repair. Therapeutic applications based on regulation of purinergic signaling are foreseen for kidney and heart muscle regeneration, Clara-like cell replacement for pulmonary and bronchial epithelial cells as well as for induction of neurogenesis in case of neurodegenerative diseases.

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.