Letter to the Editor: Extracellular vesicles in diabetic bladder dysfunction - a promising cell-free therapeutic avenue from amniotic fluid stem cells

Abstract

In this letter, we comment on the article by Liang et al for their innovative study demonstrating the therapeutic potential of human amniotic fluid stem cell-derived extracellular vesicles (EVs) in improving bladder dysfunction in a rat model of diabetic atherosclerosis. The work highlights the ability of human amniotic fluid stem cell-derived EVs to restore urodynamic parameters, reduce systemic metabolic disturbances and arterial wall thickness, and modulate key inflammatory and fibrotic pathways, such as tumor necrosis factor-α, interleukin-6, and the transforming growth factor-β/Smad axis. In clinical urology, the relevance of this cell-free approach is emphasized, which offers a promising alternative to traditional stem cell therapies by mitigating the risks of tumorigenicity and immunogenicity. Although further validation of the mechanisms and optimization of dosing regimens are required, this study represents a considerable step toward developing regenerative strategies for diabetic bladder dysfunction and encourages translational research into EVs-based therapies for urological applications.

Key Words: Extracellular vesicles; Diabetic bladder dysfunction; Amniotic fluid stem cells; Regenerative therapy; Urology

Core Tip: This letter examines the transformative potential of stem cell-derived extracellular vesicles as a novel cell-free regenerative strategy for diabetic bladder dysfunction. This underscores their unique capacity to simultaneously modulate urodynamic function, systemic metabolism, and local inflammatory-fibrotic pathways, thereby addressing the multifactorial pathogenesis of the condition. Representing a shift from symptomatic management to disease modification, extracellular vesicles offer a favorable safety profile and enhanced translational feasibility compared with whole-cell therapies. This discussion further outlines the critical steps for clinical integration, including cargo optimization, manufacturing standardization, and combination with postoperative rehabilitation.

TO THE EDITOR

The burgeoning field of regenerative medicine offers new hope for patients with conditions traditionally managed with palliative care. In urology, diabetic bladder dysfunction (DBD) is an essential example of an unmet clinical need for disease-modifying therapies, which are desperately required[1]. The pioneering study by Liang et al[2] on human amniotic fluid stem cell (hAFSC)-derived extracellular vesicles (EVs) is not merely an incremental advance, but a signal of a potential paradigm shift. Success will hinge on a trinity of advances, such as optimizing EVs biology, integrating multimodal clinical management, and establishing robust healthcare system protocols.

In this letter, we comment on an article by Liang et al[2] titled “Extracellular vesicles derived from human amniotic fluid stem cells improve bladder dysfunction in rat model of diabetic atherosclerosis” recently published in the World Journal of Stem Cells. As urologists are dedicated to advancing therapeutic strategies for lower urinary tract symptoms, particularly those rooted in metabolic disorders, we consider this investigation to be exceptionally timely and conceptually innovative[3]. The authors demonstrated a promising therapeutic avenue and illuminated a path toward addressing the fundamental pathophysiological complexities of DBD, which remains a clinical challenge with limited effective management options[4].

The global diabetes epidemic has resulted in increased urological complications, with diabetic cystopathy affecting a substantial proportion of patients. Its clinical presentation is heterogeneous and encompasses phenotypes such as detrusor overactivity, impaired contractility, and mixed patterns, all of which culminate in significant morbidity and diminished quality of life[5]. The current pharmacotherapeutic armamentarium, including antimuscarinics and β3-adrenergic agonists, primarily offers palliative relief of storage symptoms but fails to halt or reverse disease progression characterized by neural degeneration, smooth muscle dysfunction, microvascular compromise, and tissue remodeling. Liang et al[2] introduced hAFSC-EVs as potential disease-modifying agents. Their compelling evidence showed that a single systemic administration of hAFSC-EVs ameliorated bladder dysfunction, improved glycemic control, attenuated atherosclerotic vascular changes, and downregulated a cascade of inflammatory and profibrotic mediators in a rat model of diabetes and arterial injury. Functional urology seeks this multifaceted efficacy.

BEYOND SYMPTOM CONTROL: TARGETING THE DIABETIC BLADDER MILIEU

The novelty of this study lies in its demonstration of the ability of hAFSC-EVs to modify the pathological milieu of diabetic bladders. The authors reported statistically significant reductions in bladder weight (P < 0.05), a surrogate for hypertrophy and remodeling, along with marked improvements in functional parameters such as voided volume and intercontraction interval (both P < 0.05)[2]. This suggests a meaningful impact on the structural-functional relationship of the bladder wall. More importantly, molecular analysis revealed the coordinated downregulation of key mediators across interconnected pathological pathways.

Inflammatory axis (tumor necrosis factor-α and interleukin-6)

Chronic low-grade inflammation is the cornerstone of diabetic complications. Tumor necrosis factor and interleukin-6 are potent pro-inflammatory cytokines that can impair detrusor smooth muscle contractility, promote apoptosis of neuronal and muscular elements, and induce endothelial dysfunction in the bladder microvasculature[6]. By suppressing these cytokines, hAFSC-EVs may help restore a homeostatic tissue environment and preserve cellular integrity and function.

Profibrotic axis (transforming growth factor-β1, Smad3, and connective tissue growth factor)

This provided some of the most compelling mechanistic insights. Transforming growth factor (TGF)-β1 is a master regulator of fibrosis, and its activation in diabetes is well documented. Downstream signaling through Smad2/3 phosphorylation drives the transcriptional upregulation of extracellular matrix proteins such as fibronectin and collagen, along with intermediary effectors such as connective tissue growth factor (CTGF). CTGF synergizes with TGF-β to perpetuate fibroblast activation and extracellular matrix deposition[7]. Bladder fibrosis leads to reduced compliance, impaired filling sensation, and, ultimately, poor emptying. The suppression of TGF-β1, Smad3, and CTGF mRNA by hAFSC-EVs indicates a potent anti-fibrotic action, potentially preventing or slowing the irreversible fibrotic transformation of the bladder - an essential therapeutic target currently lacking effective pharmacologic options[8].

Metabolic-vascular intersection

Improvements in glycemic control and a reduction in iliac artery intimal thickness underscore the systemic effects of hAFSC-EVs. Bladder ischemia, resulting from macrovascular atherosclerosis and microvascular capillary rarefaction, is a key driver of DBD[9]. By mitigating hyperglycemia and vascular injury, hAFSC-EVs may improve perfusion and oxygen delivery to the bladder, thereby addressing the root causes of cellular stress and dysfunction.

Potential functional cargo of hAFSC-EVs

The multimodal therapeutic effects of hAFSC-EVs are mediated by their specific molecular cargo that targets key pathological axes of DBD. Research on hAFSC-EVs suggests that they are enriched in specific microRNAs and proteins crucial for regeneration[10]. Among them, miR-29b directly suppresses collagen synthesis and TGF-β/Smad signaling, constituting a precise anti-fibrotic program. miR-146a inhibits nuclear factor kappa B activation, attenuating the downstream production of pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin-6. Concurrently, superoxide dismutase mitigates hyperglycemia- and ischemia-induced oxidative stress, while tissue inhibitor of metalloproteinase-1 helps to restore extracellular matrix homeostasis[11]. This composite payload enables hAFSC-EVs to function as an integrated nanotherapeutic agent, simultaneously disrupting the inflammatory, fibrotic, and metabolic-vascular cascades that drive disease progression.

STRATEGIC ADVANTAGE OF EVS IN UROLOGICAL APPLICATIONS

The authors highlight the practical and safety benefits of EVs-based approaches over whole-cell therapies. These advantages are of critical importance for urologists in clinical translation.

Safety profile

The risks of tumorigenicity, immunogenic rejection, and vascular occlusion associated with viable cell transplantation are substantially reduced compared to those associated with viable cell transplantation[12].

Delivery logistics

EVs offer flexibility in their administration routes. Although Liang et al[2] used intravenous injections, future urological applications should explore minimally invasive intravesical instillations, potentially enabling high local concentrations with minimal systemic exposure. Their nanoscale dimensions facilitate tissue penetration[13].

Challenges and considerations in clinical manufacturing and standardization

For hAFSC-EVs to advance toward “off-the-shelf” therapeutics, several translational challenges common to EV-based platforms must be systematically addressed. First, manufacturing requires scalable serum-free culture systems to ensure batch-to-batch consistency and safety. Subsequently, quality control must extend beyond standard characterizations (e.g., nanoparticle tracking analysis for size and western blotting for markers) to include techniques such as high-resolution flow cytometry to assess purity and exclude non-EV contaminants. A pivotal unresolved challenge is the lack of standardized potency assays[14]. Defining the relevant potency, for instance, by quantifying key functional cargo (e.g., miR-29b) or establishing functional in vitro readouts (e.g., inhibition of the fibroblast-to-myofibroblast transition), is essential for regulatory evaluation and reliable dosing. Finally, long-term storage stability (e.g., via optimized lyophilization protocols) remains an area that requires further optimization.

FUTURE DIRECTIONS FOR MECHANISTIC AND TRANSLATIONAL EXPLORATION

While deepening fundamental mechanistic research, it is essential to recognize that the ultimate value of any novel therapy must be demonstrated through clinical applications. Therefore, future translational research should extend beyond the biological mechanisms and integrate critical human factors into clinical practice.

Clinical integration of mechanistic studies

While determining the optimal dosage, administration routes, and mechanisms of action of EVs, simultaneous consideration should be given to their integration with existing bladder training and behavioral therapies. For example, research should focus on identifying the optimal therapeutic window following EVs treatment to improve bladder sensitivity and capacity, thereby determining the most appropriate timing for implementing behavioral interventions such as pelvic floor muscle training and scheduled voiding[15]. This approach aims to achieve synergistic effects between biological and behavioral rehabilitation.

Mechanisms of lifestyle synergy

Although preclinical evidence directly linking lifestyle interventions to enhanced efficacy of EV therapy in DBD remains limited, this represents a compelling avenue for future research. Preliminary studies in related fields suggest that metabolic improvements, such as enhanced glycemic control and reduced systemic inflammation, may favorably alter the host microenvironment, potentially influencing the pharmacokinetics, biodistribution, and cellular responsiveness to administered EVs[16]. Future investigations should systematically evaluate whether structured lifestyle modifications (e.g., dietary regimens and exercise protocols) can potentiate the therapeutic effects of hAFSC-EVs in relevant disease models.

Research on healthcare system integration

Translational research should explore integration at the healthcare system level and support the design of multidisciplinary collaborative diagnostic and treatment models capable of combining EVs therapy, metabolic management, rehabilitation training, and long-term follow-up. Concurrently, it is essential to develop objective monitoring indicators suitable for clinical use, such as ultrasound-based assessments of bladder morphology and urinary biomarker panels, and establish standardized efficacy evaluations and long-term safety monitoring systems[17]. Research incorporating these clinical practice elements will help ensure that EVs therapy progresses from laboratory validation to an operable and scalable clinical solution capable of improving patients’ quality of life.

CONCLUSION

Liang et al[2] provided a compelling preclinical proof-of-concept positioning hAFSC-EVs at the forefront of next-generation therapies for DBD. By demonstrating efficacy across metabolic, vascular, inflammatory, and fibrotic domains, they advance beyond symptomatic management toward true disease modification[2]. This study bridges cutting-edge regenerative biology with the pressing clinical needs in urology. We anticipate the next steps in this research trajectory, from detailed mechanistic elucidation to early-phase clinical studies, which hold the promise of transforming the care for millions of patients living with this serious complication of diabetes.

ACKNOWLEDGEMENTS

We thank WeChat official account “previsiont” and Guo-Kai Xie for their suggestions on health management.