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.


Introduction And Background
Urology is a medical field that specializes in treating genitourinary disorders, ranging from simple lifestyle changes to more invasive and advanced surgical procedures.In recent decades, this field has witnessed significant technological advancements through the introduction of cutting-edge robotics and minimally invasive surgeries, significantly improving patient outcomes and prognosis, and reducing overall hospital stay and postoperative complications.However, the literature continues to show certain limitations, especially in terms of traditional management options.These options may require extended use of medications, associated with temporary relief or a high risk of side effects [1,2].
Regenerative medicine is an innovative and rapidly developing treatment strategy in various medical disciplines [3].It emphasizes enhancing the body's natural ability to heal and regenerate injured tissues and organs, as well as promoting tissue repair and functional recovery [4].These strategies include stem cell therapy, tissue engineering, and the delivery of growth factors [5].Currently, urology is undergoing a significant transformation in terms of the formulation of therapies related to regenerative medicine.The integration of this approach could revolutionize disease management, reducing safety concerns and increasing efficiency.Recent studies have shown that bladders grown in laboratories can be successfully transplanted and that urological tissues can be rebuilt [6].The evidence of its efficacy and clinical applications has mushroomed, highlighting the transformative potential of regenerative medicine in urology.
Given the rapid increase in interest in the applications of regenerative medicine in the field of urology and the huge uptick in research activities, it is necessary to comprehensively assess the current state of the evidence.This systematic review aims to review the current state and progress of research in regenerative medicine and assess its significance and impact on urology.

Study Selection
A total of 1603 studies were identified from online database searches (PubMed: 980, Google Scholar: 413, and CENTRAL: 210).Duplicates and automated filters removed 77 studies, leaving 1,526 for screening.Title and abstract screening eliminated 1115, leaving 411.Full-text screening removed 364, while 47 studies advanced to methodological screening and further full-text screening.After excluding 31 studies, this systematic review ultimately included only 16 that met the inclusion criteria.Figure 1

Study Characteristics
Table 1 provides a summary of the characteristics of the included studies.

Discussion
Tissue engineering involves the utilization of bioengineering principles and biomaterials to create a viable biological transplant for normal tissue and its associated functionality [23].Using autologous tissues for reconstructive surgeries may carry an additional risk of graft rejection, and sequelae of postoperative immunosuppressive therapy [24].On the other hand, clinical follow-ups have shown delayed healing of the area of the donor's body from where the tissue was removed [25].Tissue engineering offers a promising alternative for the restoration of damaged tissues and organs associated with the field of urology.Over the last two decades, there has been a notable increase in scientific interest in stem cells and their capacity for regeneration and differentiation.

Biomaterials and Tissue Engineering
Biomaterials provide physical adhesion to the extracellular matrix (ECM).In regeneration, biomaterials regulate cell differentiation, migration, proliferation, and gene expression [26].Morgante et al. investigated whether decellularized tissue matrices could recreate urological tissue's physiologic and biochemical functions.Ideally, biomaterials facilitate tissue growth with minimal adverse effects.The paper also proposed biomaterials such as urethral grafts for tissue integration and cellularization.All porcine survived surgery and 2.5 years of postoperative surveillance without any issues.The implantation of decellularized tissue matrices in large animal surgery models is well-tolerated and non-inflammatory [7].
Orabi et al. documented novel biomaterials for urethral repair in biocompatible tubularized tissue constructs.Traditionally, tissues from the buccal mucosa, bladder mucosa, or genital flaps were used to repair defects such as strictures and increased urethral caliber.Orabi et al. introduced cell-seeded tubularized scaffolds for wider caliber urethras.Within 12 months, the cellular organization increased, an epithelial cell layer formed, and muscle fiber bundles formed in collagen scaffolds.Seeded cells labeled with a fluorescent marker were monitored for three months.Urothelial and smooth muscle cells survived, proliferated, and contributed to the multilayered tissue structure, confirming the tissue-engineering potential of cell-seeded biomaterials [8].
Seeding autologous cells promotes tissue integration and minimizes inflammation.This is supported by Horst et al., who used hybrid PEU scaffolds to form acellular bladder matrices and encourage the formation of bladder tissue with a low inflammatory response.The researchers investigated a property of biomaterials used in regenerative modalities.Implanted biomaterials mimic target tissue properties for similar regenerated tissues.Horst et al. used high-elasticity PEU hybrid scaffolds, similar to a urinary bladder, to transmit mechanical forces to regenerate smooth muscle cells [19].
To mimic the bladder's neuronal network, Adamowicz et al. added graphene to an amniotic membrane biocomposite to increase electrical conductivity.A biocompatible graphene layer increased electrical conductivity, resembling a bladder wall, without cytotoxicity for smooth muscle cells [27].Graphene-based scaffolds may help tissue engineering restore organ function [28].The literature endorses the use of graphene-layered biomaterials for muscle differentiation and proliferation [29,30], which warrants preclinical in vivo trials.
They have a wide range of applications in tissue engineering, regenerative medicine, and cell therapy, particularly as autologous stem cells derived from an individual's body.For instance, adult mesenchymal stem cells (MSCs) offer therapeutic potential through differentiation and lifelong organ regeneration [13,32].
Adipose tissue-derived stem cells (ADSCs) are effective in the treatment of several medical conditions, and their immunosuppressive properties have been acknowledged by An et al [32].According to the Association for the Advancement of Blood and Biotherapies, transplanted cells can heal spinal cord injuries, joint cartilage, neurologic disorders, and the immune system.Silverman et al. modified patient or donor cells to overcome diseases and medical conditions, with advances like chimeric antigen receptor therapy for blood cancers [33].However, safety, tumorigenicity, and high manufacturing costs make cell-based therapies difficult to implement.Despite these barriers, cell-based therapies offer unique advantages, as cells can naturally migrate, localize, and proliferate in specific tissues or compartments [34].
Garcia-Arranz et al. demonstrated the safety of autologous MSCs from liposuction.Patients were evaluated every three months for one year after endoscopic intraurethral injection.This alternative therapy aimed to treat urinary incontinence, with lower associated risks compared to traditional treatments [10].The small sample size limits conclusive effectiveness assessment, building on earlier studies like Huang et al. [10,15].In vitro, multipotent ADSCs from adipose tissue can differentiate into neuron-like, endothelial, and smooth muscle cells.Huang et al. autologously injected cultured ADSCs into the corpus cavernosum of 18 rats to increase smooth muscle content promise for erectile dysfunction treatment [15].Das et al. reproduced similar results in male mice, with stem and stromal cells from human breast adipose tissue-derived stromal vascular fraction (SVF).Stem cells differentiated to increase cavernous endothelial and smooth muscle cell content, restoring erectile function significantly [16].Bone marrow-derived MSCs secrete neurotrophic factors that induce neural regeneration, as seen in VEGF, brain-derived neurotrophic factors, and nerve growth factors [35].
ADSCs and human SVF cells were found in small amounts in the corpus cavernosum 14 days after implantation [15,16].Other investigators observed rapid stem cell disappearance at around four weeks, suggesting migration and death rather than differentiation [36].Current evidence suggests that stem cells migrate to the bone marrow due to their nature [37][38][39].Cell-based therapies rely on various cell types for seeding therapeutic scaffolds to induce tissue regeneration.ADSCs, human SVF cells, and urine-derived stem cells (USCs) have been studied for tissue-engineered organs.In vitro, Bodin et al. used bacterial cellulose (BC) scaffolds seeded with USC to regenerate urinary diversion conduits with multilayers of smooth muscle and urothelial cells over two weeks [18].In athymic mice requiring cystoplasty, differentiation into smooth muscle cells and urothelial markers was observed in vivo [18].Multiple in vitro regeneration and in vivo implantation attempts have shown that dynamic cultures promote cell growth and muscle and urothelial layer formation [19,22,40].Bodin et al. also noted an increased cellular infiltration into the bacterial cellulose matrix in dynamic cultures compared to static cultures [18,40].Koch et al. crosslinked scaffolds with various agents and incubated them for two weeks before implanting them to reconstruct the urinary bladder [18,27] or the ureters [21,22].This showed constructive remodeling and integration of the scaffold into the surrounding tissue.

Clinical Outcomes and Safety
All studies in this review explored regenerative therapies for urologic conditions, including urethral tissue regeneration [21], urinary incontinence correction [11,12], erectile dysfunction treatment [14,17], ureteric defect reconstruction, and bladder tissue formation [22].Overall, these 16 studies suggest that regenerative medicine effectively builds new tissues to address the target condition.Some studies even replicated the neurological network of the rebuilt tissues, indicating the reliability of regenerative medicine [14][15][16].Tissue innervation is crucial for replicating the original tissue's properties in the regenerated tissues, particularly in addressing conditions like erectile dysfunction [16].However, assessing the effectiveness of regenerative medicine has certain limitations.Current literature uses small sample sizes, in vitro experiments, and non-human subjects, making it difficult to assess its efficacy [10].According to Ławkowska et al., advanced reconstructive urology techniques outperform regenerative techniques in clinical settings, casting doubt on the widespread use of regenerative medicine in urology [41].The primary issue involves the inability to accurately replicate the complex native tissue environment.On reviewing the evidence, regenerative medicine appears to be most successful in treating urinary incontinence [10][11][12], but the clinical trials that arise from this evidence show short-term success compared to placebo treatments [42,43].

Safety concerns in regenerative medicine
have not yet raised significant alarms on a small scale.Koch et al. found no cytotoxic effect with the implants and Yamamoto et al. reported safe peri-urethral injection of regenerative cells [12,22].However, the discourse on the safety of regenerative medicine is multifaceted and dependent on therapy, cell source, tissue type, and administration method.For instance, Zhou et al. noted a potential link between VEGF, which promotes cell regeneration, and cancer development [43], indicating that long-term carcinogenic risk may exist within biomaterials [41,44].Current safety evidence is highly subjective to individual studies, which necessitates further large-sample clinical trials and comprehensive meta-analyses.

Conclusions
This review examined the current state of regenerative medicine, with a focus on its uses in urology.
Regenerative medicine is a cutting-edge field that combines biology, medicine, and engineering, with the main objective of repairing, replacing, or regenerating human cells, tissues, or organs.This technique has the potential to greatly improve the treatment of diseases of the urinary and reproductive systems in urology.Our findings illustrate the great advances that regenerative medicine has brought to the field of urology.These studies showcase a variety of cutting-edge methods, such as tissue engineering for urethral reconstruction, gene editing for the treatment of prostate cancer, and stem cell therapy for bladder dysfunctions, which could usher in a paradigm shift in urological care, away from traditional symptomatic therapy and toward treating the underlying causes of illnesses.
Regenerative medicine holds promise for treating renal problems, incontinence, and erectile dysfunction in urology.Instead of only treating symptoms, these therapies try to return the body to its normal state.However, there are often unanticipated side effects that emerge during clinical studies, making the transition from research to therapeutic use difficult; these highlight the need to comprehend the long-term effects and interactions with the reproductive and urinary systems.Despite these drawbacks, regenerative therapy in urology holds great promise.It might completely change the way many urological illnesses are treated by providing more potent and possibly even curative treatments.However, to fully exploit this promise, comprehensive and carefully monitored clinical trials are required to determine the safety and efficacy of these novel medicines, which would shed on light the complexities of regenerative treatments within the urological setting and guarantee compliance with strict regulatory requirements.
In urology, regenerative medicine is still in a phase of development; therefore, it is critical to maintain a balance between innovation and safety and ethical issues.Along with overcoming scientific and medical obstacles, the industry also needs to deal with accessibility, ethical, and legal concerns.Regenerative medicine in urology has a bright future ahead of it, with potentially ground-breaking therapies that could improve patient outcomes and quality of life.
below shows the PRISMA flow diagram depicting the study selection process.

FIGURE 1 :
FIGURE 1: PRISMA flowchart depicting the selection of studies PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses Stem and stromal cells Treating ED Human SVF treatment significantly increased cavernous endothelial and smooth muscle cell contents, induced eNOS phosphorylation, and restored penile nNOSpositive nerve fibers.Erectile function significantly improved in diabetic mice treated with human SVF and SVF lysate Ryu et al., endothelial cell proliferation, eNOS phosphorylation, and cGMP expression.SVF promotion of cavernous angiogenesis and erectile function was abolished with VEGF-Trap, a VEGFenable 3D USC growth, forming a multilayered urothelium and cell-matrix infiltration.Cell-seeded BC scaffolds hold promise for tissueengineered urinary conduits in urinary reconstruction Horst et al., scaffolds promote bladder tissue formation with excellent integration and low inflammation.PEU is a promising biomaterial for tissue layer significantly increased biocomposite electrical conductivity.The graphene layer efficiently stimulated SMC with a strong cell-to-biomaterial interface Zhao et al., 2020 [21] Differentiated human-USCs Ureter reconstruction Ultimately, a layered ureter structure with multilayered urothelium over organized smooth muscle tissue.Tissue-engineered graft formed multilayered urothelium and organized smooth muscle tissue after ureteral reconstruction Koch et al., vitro: CDI and genipin GP scaffolds had more ingrown 3T3 and rat SMCs than untreated scaffolds.In vivo: implants were mainly infiltrated by fibroblasts and M2 anti-inflammatory macrophages.CDI was the most beneficial for crosslinking ECM scaffolds.Results aid in developing a biocompatible ureteral xenograft

Study Type of regenerative medicine Urological application Conclusion
scaffolds for reconstructing long urethral defects.Bladder-derived acellular collagen matrix with autologous cells led to 2024 Abuharb et al.Cureus 16(1): e52264.DOI 10.7759/cureus.522643 of 9Morgante et al., 2021 [7] Biomaterials Urethra to treat hypospadias Evidence that implanted non-crosslinked acellular matrices readily incorporate to support surgical repair.Acellular matrix onlay grafts enhance repair quality and reduce complications Orabi et al., 2013 [8] Biomaterials Urethral reconstruction Preclinical evidence of cell-seeded tubularized Erectile function significantly improved with ADSC treatment.PD animals' fibrosis and elastosis areas were prevented by ADSC treatment.ADSC injection prevents fibrosis and elastosis in the TA and corpus cavernosum Huang et al., 2010 [15] ADSCs Treatment of ED ADSC ameliorates nerve and endothelial abnormalities, promising a potential therapy for ED Das et al., 2014 [16]