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The Homeodomain Transcription Factor NKX3.1 Modulates Bladder Outlet Obstruction Induced Fibrosis in Mice
Mehul S Patel1, Diana K Bowen1,2, Nicholas M Tassone2
1Department of Urology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States.
Insights
Fibrosis in children
Area of Science:
- Urology
- Pediatric Pathology
- Molecular Biology
Background:
- Fibrosis, characterized by collagen deposition and tissue stiffening, is a significant cause of organ dysfunction in children.
- Current understanding of fibrotic mechanisms and effective treatments for pediatric fibrosis remains limited.
- Previous studies indicated castration reduces bladder fibrosis in male mice with partial outlet obstruction.
Purpose of the Study:
- To investigate the role of androgen response genes in bladder fibrosis following partial bladder outlet obstruction (PO) in mice.
- To determine if Nkx3.1, an androgen response gene, influences bladder remodeling and fibrosis after PO.
Main Methods:
- Quantitative PCR (QPCR) microarray and QRTPCR were used to assess gene expression changes in mouse bladders after PO.
- Immunofluorescent antibody localization was employed to detect NKX3.1 protein.
- Histological analysis and gene expression profiling were performed on wild-type and Nkx3.1 knockout mice after PO.
Main Results:
- Partial bladder outlet obstruction (PO) significantly increased the expression of the androgen response gene Nkx3.1 and its protein in mouse bladders.
- Genetic deletion of Nkx3.1 in mice resulted in reduced bladder remodeling, smaller bladder size, and decreased bladder wall thickness after PO.
- Loss of Nkx3.1 specifically ameliorated histological fibrosis, reduced the collagen to muscle ratio, and altered gene expression related to collagen and smooth muscle.
Conclusions:
- Nkx3.1 is induced in the bladder after PO and plays a critical role in mediating pathways that lead to tissue fibrosis.
- The findings suggest Nkx3.1 mediates fibrosis in male mice, potentially explaining the sexual dimorphism observed in bladder fibrosis.
- Targeting Nkx3.1 may offer a therapeutic strategy for pediatric bladder fibrosis.
Abstract:
Fibrosis is an irreversible remodeling process characterized by the deposition of collagen in the extracellular matrix of various organs through a variety of pathologies in children, leading to the stiffening of healthy tissues and organ dysfunction. Despite the prevalence of fibrotic disease in children, large gaps exist in our understanding of the mechanisms that lead to fibrosis, and there are currently no therapies to treat or reverse it. We previously observed that castration significantly reduces fibrosis in the bladders of male mice that have been partially obstructed. Here, we investigated if the expression of androgen response genes were altered in mouse bladders after partial bladder outlet obstruction (PO). Using a QPCR microarray and QRTPCR we found that PO was sufficient to increase expression of the androgen response gene Nkx3.1. Consistent with this was an increase in the expression of NKX3.1 protein. Immunofluorescent antibody localization demonstrated nuclear NKX3.1 in most bladder cells after PO. We tested if genetic deletion of Nkx3.1 alters remodeling of the bladder wall after PO. After PO, Nkx3.1 bladders underwent remodeling, demonstrating smaller bladder area, thickness, and bladder: body weight ratios than obstructed, wild type controls. Remarkably, Nkx3.1 specifically affected histological parameters of fibrosis, including reduced collagen to muscle ratio. Loss of Nkx3.1 altered collagen and smooth muscle cytoskeletal gene expression following PO which supported our histologic findings. Together these findings indicated that after PO, Nkx3.1 expression is induced in the bladder and that it mediates important pathways that lead to tissue fibrosis. As Nkx3.1 is an androgen response gene, our data suggest a possible mechanism by which fibrosis is mediated in male mice and opens the possibility of a molecular pathway mediated by NKX3.1 that could explain sexual dimorphism in bladder fibrosis.
