The role of calpain-calpastatin system in the development of stress urinary incontinence

Advances in the molecular pathogenesis and cell therapy of stress urinary incontinence

Stress urinary incontinence (SUI) is very common in women. It affects patients' mental and physical health, and imposed huge socioeconomic pressure. The therapeutic effect of conservative treatment is limited, and depends heavily on patient persistence and compliance. Surgical treatment often brings procedure-related adverse complications and higher costs for patients. Therefore, it is necessary to better understand the potential molecular mechanisms underlying stress urinary incontinence and develop new treatment methods. Although some progress has been made in the basic research in recent years, the specific molecular pathogenic mechanisms of SUI are still unclear. Here, we reviewed the published studies on the molecular mechanisms associated with nerves, urethral muscles, periurethral connective tissue and hormones in the pathogenesis of SUI. In addition, we provide an update on the recent progresses in research on the use of cell therapy for treating SUI, including research on stem cells therapy, exosome differentiation and gene regulation.

Molecular Processes in Stress Urinary Incontinence: A Systematic Review of Human and Animal Studies

Stress urinary incontinence (SUI) is a common and burdensome condition. Because of the large knowledge gap around the molecular processes involved in its pathophysiology, the aim of this review was to provide a systematic overview of genetic variants, gene and protein expression changes related to SUI in human and animal studies. On 5 January 2021, a systematic search was performed in Pubmed, Embase, Web of Science, and the Cochrane library. The screening process and quality assessment were performed in duplicate, using predefined inclusion criteria and different quality assessment tools for human and animal studies respectively. The extracted data were grouped in themes per outcome measure, according to their functions in cellular processes, and synthesized in a narrative review. Finally, 107 studies were included, of which 35 used animal models (rats and mice). Resulting from the most examined processes, the evidence suggests that SUI is associated with altered extracellular matrix metabolism, estrogen receptors, oxidative stress, apoptosis, inflammation, neurodegenerative processes, and muscle cell differentiation and contractility. Due to heterogeneity in the studies (e.g., in examined tissues), the precise contribution of the associated genes and proteins in relation to SUI pathophysiology remained unclear. Future research should focus on possible contributors to these alterations.

Biomarkers Implicated in Lower Urinary Tract Symptoms: Systematic Review and Pathway Analyses

PURPOSE

Lower urinary tract symptoms are prevalent and burdensome, yet methods to enhance diagnosis and appropriately guide therapies are lacking. We systematically reviewed the literature for human studies of biomarkers associated with lower urinary tract symptoms.

MATERIALS AND METHODS

PubMed®, EMBASE® and Web of Science® were searched from inception to February 13, 2018. Articles were included if they were in English, performed in benign urological populations without neurological disorders or interstitial cystitis/bladder pain syndrome, and assessed a biomarker's association with or ability to predict specific lower urinary tract symptoms or urological conditions. Bioinformatic pathway analyses were conducted to determine whether individual biomarkers associated with symptoms are present in unifying pathways.

RESULTS

Of 6,150 citations identified 125 met the inclusion criteria. Most studies (93.6%) assessed biomarkers at 1 time point and were cross-sectional in nature. Few studies adjusted for potentially confounding clinical variables or assessed biomarkers in an individual over time. No individual biomarkers are currently validated as diagnostic tools for lower urinary tract symptoms. Compared to controls, pathway analyses identified multiple immune response pathways that were enriched in overactive bladder syndrome and cell migration/cytoskeleton remodeling pathways that were enriched in female stress incontinence.

CONCLUSIONS

Major deficiencies in the existing biomarker literature include poor reproducibility of laboratory data, unclear classification of patients with lower urinary tract symptoms and lack of adjustment for clinical covariates. Despite these limitations we identified multiple putative pathways in which panels of biological markers need further research.

miR-93‑mediated collagen expression in stress urinary incontinence via calpain-2

The aim of the present study was to investigate the expression and mechanism of microRNA (miR)‑93 in collagen expression in stress urinary incontinence (SUI). Vaginal tissue, primary fibroblasts and SUI primary fibroblasts were obtained to detect the expression of miR‑93, interstitial collagenase (MMP1), collagen I and calpain‑2. Reverse transcription‑quantitative polymerase chain reaction analysis was performed to detect the levels of miR‑93 and MMP1. Western blotting was used to evaluate the protein levels of calpain‑2, MMP1 and collagen I. MMP1 and hydroxyproline levels in the supernatant were measured by ELISA. The association between miR‑93 and calpain‑2 was investigated by luciferase reporter assays. The expression of miR‑93 and collagen I was significantly downregulated in the SUI group, while the expression of calpain‑2 and MMP1 was significantly upregulated. ELISA analysis demonstrated that the MMP1 level increased and the hydroxyproline level decreased in the SUI group. Additionally, calpain‑2 was identified to be a target of miR‑93, and miR‑93 was able to negatively regulate the expression of calpain‑2. Restoration of calpain‑2 in miR‑93‑overexpresseing SUI primary fibroblasts reversed the alteration in hydroxyproline expression, indicating that calpain‑2 was negatively associated with collagen expression. The results of the present study suggested that miR‑93 regulated MMP1 and collagen I expression in fibroblasts via calpain‑2. miR‑93 mediated collagen expression in stress urinary incontinence via calpain‑2.

Three low molecular weight cysteine proteinase inhibitors of human seminal fluid: purification and enzyme kinetic properties

The cystatins form a superfamily of structurally related proteins with highly conserved structural folds. They are all potent, reversible, competitive inhibitors of cysteine proteinases (CPs). Proteins from this group present differences in proteinase inhibition despite their high level of structural similarities. In this study, three cysteine proteinase inhibitors (CPIs) of low molecular weight were isolated from human seminal fluid (HSF) by affinity chromatography on carboxymethyl (CM)-papain-Sepharose column, purified using various chromatographic procedures and checked for purity on sodium-dodecyl PAGE (SDS-PAGE). Matrix-assisted laser desorption-ionization-time-of flight-mass spectrometry (MALDI-TOF-MS) identified these proteins as cystatin 9, cystatin SN, and SAP-1 (an N-terminal truncated form of cystatin S). All three CPIs suppressed the activity of papain potentially and showed remarkable heat stability. Interestingly SAP-1 also inhibits the activity of trypsin, chymotrypsin, pepsin, and PSA (prostate specific antigen) and acts as a cross-class protease inhibitor in in vitro studies. Using Surface Plasmon Resonance, we have also observed that SAP-1 shows a significant binding with all these proteases. These studies suggest that SAP-1 is a cross-class inhibitor that may regulate activity of various classes of proteases within the reproductive systems. To our knowledge, this is the first report about purification of CPIs from HSF; the identification of such proteins could provide better insights into the physiological processes and offer intimation for further research.

The role of the ERK1/2 signalling pathway in the pathogenesis of female stress urinary incontinence

Objective:

To investigate the role of extracellular-regulated protein kinase (ERK)1/2 and phosphorylated (p)-ERK1/2 in the pathogenesis of female stress urinary incontinence (SUI).

Methods:

Anterior vaginal wall tissue was collected from women with SUI and control subjects. Immunohistochemistry and Western blotting were performed for p-ERK1/2. Primary vaginal fibroblast cultures were incubated in the presence or absence of PD98059 (an inhibitor of ERK kinase) and levels of collagen I and III mRNA and protein were examined by quantitative reverse transcription–polymerase chain reaction and Western blot, respectively.

Results:

Levels of p-ERK1/2 were significantly lower in vaginal wall tissue from patients with SUI ( n = 10) compared with controls ( n = 10). PD98059 treatment significantly reduced levels of collagen I and III mRNA and protein.

Conclusions:

Female SUI is associated with reduced levels of p-ERK1/2 compared with controls, and inhibition of the ERK1/2 signalling pathway inhibits collagen type I and III synthesis in vaginal wall fibroblasts.

The calpain system as a potential target for pelvic muscle reinforcement

The fascial and muscular components within the pelvic floor create a support mechanism that facilitates storage and voiding of urine. Their constituents are mainly fibrillar collagens I and III, which are responsible for maintaining tensile strength. Stretching and recoiling is enabled by the elastic fibers consisting of elastin on a scaffold of microfibrils, fibrillin-1 and -2. Calpains are intracellular Ca2+ -dependent cysteine proteases found in almost all eukaryotes and some bacteria. Calpains display limited proteolytic activity at neutral pH, proteolyzing substrates to transform and modulate their structures and activities, and are therefore called “modulator proteases”. By making selective limited proteolytic cleavages, they modulate the activity of enzymes, including key signaling molecules, and induce specific cytoskeletal rearrangements, accounting for their roles in signal transduction and structural stabilization. Understanding these mechanisms should provide avenues for novel therapeutic strategies to treat pathological processes such as urinary incontinence and pelvic prolapse.