Zhina Sadeghi, MD, was one of the recipients of the 2024 Urology Care Foundation™ Research Scholar Awards. These awards provide $40,000 annually for mentored research training for clinical and postdoctoral fellows or early-career faculty. The Society of Urodynamics, Female Pelvic Medicine and Urogenital Reconstruction sponsored Dr Sadeghi’s award.

Urinary incontinence (UI) is a common condition affecting up to 60% of women, with its prevalence increasing as women age. This condition not only imposes a substantial economic burden, with annual costs nearing $10 billion, but also significantly diminishes the quality of life for those affected. Current treatment options, primarily focused on bladder muscle dysfunction in urgency UI and urethral support in stress UI, have reached a plateau in effectiveness. As a result, up to 57% of treated women continue to suffer from persistent, recurrent, or new-onset UI, highlighting the critical need for a deeper understanding of the underlying mechanisms to develop more effective therapies.

Urethral failure is recognized as a leading cause of stress UI and a contributing factor to urgency UI. However, despite the urethra’s critical role in maintaining continence, current UI treatments largely neglect this aspect. Research shows that urethral function declines by approximately 15% per decade with aging, likely due to decreased muscle mass and increased connective tissue. However, the exact mechanisms driving this decline remain poorly understood.

To explore this issue, we conducted a pilot study investigating the impact of aging on urethral function using a mouse model. We compared the functional, morphometric, and transcriptomic profiles of urethral tissues between young and old female mice. Our findings revealed significant age-related changes that closely resemble those observed in female humans.

Functionally, we found that aged female mice exhibited a 26.55% lower bladder leak point pressure compared with younger mice, indicating a reduced capacity to maintain continence. Morphometric analysis using vectorized scale-invariant pattern recognition technology showed that the midurethra of older mice had less striated muscle, more extracellular matrix/fibrosis, and a decreased ratio of elastin fibers compared with younger mice.

Gene expression profiling (bulk RNA sequencing) of the entire urethra further revealed notable differences between the 2 age groups, as shown in part A of the Figure. In aged mice, we identified a higher number of downregulated genes relative to younger mice. Pathways related to immune response and muscle function (including both striated and smooth muscle) were predominantly enriched in aged tissues. In contrast, pathways involved in keratinization, skin development, and cell differentiation were significantly downregulated in the aged urethra.

Further validating the RNA sequencing data, reverse transcription quantification PCR showed an upregulation of specific genes in the aged mouse group, such as Ctgf, Tgf-β, etc, suggesting that genes associated with the extracellular matrix may play a critical role in the pathogenesis of the aging urethra. Additionally, our transcriptomic data indicate that many of these upregulated extracellular matrix–related genes are linked to fibro-adipogenic progenitor (FAP) cells—mesenchymal-like stem cells within skeletal muscle, as shown in part B of the Figure. Our observations suggest that FAP cells may be critical contributors to the reduction in striated muscle mass and the increase in fibrotic extracellular matrix in aged urethral tissues, resulting in the decline in urethral function with age.

Our preliminary results highlight the need for further investigation into the cellular mechanisms leading to decreased urethral muscle mass and increased fibrotic connective tissue with aging. With the support of the recently awarded AUA Research Scholar Award to Dr Zhina Sadeghi, our team will focus on examining the changes in FAP cell populations and their gene expression activities to understand how these cells result in disrupting urethral muscle homeostasis and promoting fibrosis in aging, ultimately leading to urethral dysfunction.

Our goal is to use single-cell RNA sequencing to identify differential gene expression in FAP cells from young, middle-aged, and geriatric mouse urethras. We will also apply pseudotime inference from single-cell RNA sequencing data to explore how FAP cell transcriptomes change with aging. These insights will be crucial for understanding the molecular mechanisms behind striated muscle loss during aging. Additionally, we will use RNAScope to gain a comprehensive view of FAP cell localization, communication, and their microenvironment as they age, providing valuable spatial context.

The outcomes of this work will significantly expand our understanding of the fundamental changes leading to urethral dysfunction, providing essential information that could drive the development of new pharmacological targets, cell transplantation strategies, or other innovative approaches to delay urethral dysfunction or restore healthy urethral function.