Antifibrosis treatment by inhibition of VEGF, FGF, and PDGF receptors improves bladder wall remodeling and detrusor overactivity in association with modulation of C‐fiber afferent activity in mice with spinal cord injury

Abstract

Aims: Spinal cord injury (SCI) above the sacral level causes bladder dysfunction and remodeling with fibrosis. This study examined the antifibrotic effects using nintedanib, an inhibitor of vascular endothelial growth factor, fibroblast growth factor, and platelet-derived growth factor receptors, on detrusor overactivity (DO) and bladder fibrosis, as well as the modulation mechanisms of C-fiber afferent pathways. Methods: Thirty female C57BL/6 mice were divided into group A (spinal intact), group B (SCI with vehicle), and group C (SCI with nintedanib). At 2 weeks after SCI, vehicle or 50 mg/kg nintedanib was administered subcutaneously for 2 weeks. Then, cystometry was conducted, followed by RT-PCR measurements of fibrosis-related molecules, muscarinic, β-adrenergic, TRP and purinergic receptors in the bladder or L6-S1 dorsal root ganglia (DRG). Trichrome stain and Western blot analysis of transforming growth factor-beta and fibronectin were performed in the bladder. TRPV1 expression in L6 DRG was measured by immunohistochemistry. Results: In cystometry, intercontraction intervals, nonvoiding contractions, voided volume, and voiding efficiency were significantly improved in group C versus group B. RT-PCR, Western blotting, and trichrome staining revealed the fibrotic changes in the bladder of group B, which was improved in group C. Increased messenger RNA levels of TRPV1, TRPA1, P2X 2 , and P2X 3 in DRG of group B were significantly decreased in group C. TRPV1 immunoreactivity in DRG was increased in group B, but decreased in group C. Conclusions:Nintedanib improves storage and voiding dysfunctions and bladder fibrosis in SCI mice. Also, nintedanib-induced improvement of DO is associated with reduced expression of C-fiber afferent markers, suggesting the modulation of bladder C-fiber afferent activity.

Current Knowledge and Novel Frontiers in Lower Urinary Tract Dysfunction after Spinal Cord Injury

“…[ 117 – 119 ] Transcripts of type 3 collagen, hypoxia-inducing factor-1α, transforming growth factor (TGF)-β1, and fibroblast growth factor (FGF) are increased in the bladder of SCI rats. [ 120 , 121 ] Inefficient voiding due to DSD induces bladder distention, which evokes bladder ischemia, followed by bladder fibrosis. [ 119 ] Bladder fibrosis with dense extracellular matrix deposition further deteriorates voiding dysfunction with reduced detrusor contractility, making the bladder stiffer, and less compliant.…”

“…[ 122 ] Our recent study reported that subcutaneous nintedanib treatment improves both storage and voiding dysfunctions, evident as increased voided volume per micturition and voiding efficiency in SCI mice. [ 121 ] Nintedanib administration into SCI mice downregulates fibrosis-related molecules in the bladder including TGF-β1 and collagen type 1 and 3. [ 121 ] Increased mRNA levels of TRPV1, TRPA1, P2X2, and P2X3 in lumbosacral DRG (C-fiber related) in SCI mice are significantly decreased, and the collagen deposition (trichrome staining) in the bladder is decreased after nintedanib treatment.…”

Continuous administration of mirabegron has advantages in inhibition of central sensitization compared with short‐term treatment cessation in a mouse model of overactive bladder

“…Also, β2‐ and β3‐adrenergic receptors are known to modulate smooth muscle relaxation in the bladder; however, in this study, they were increased in OAB mice. In our previous study, β2 and β3 receptors were increased in SCI‐induced DO mice but normalized when DO disappeared 19 . Therefore, it is assumed that upregulated β receptors would be a compensatory mechanism to counteract bladder overactivity in OAB mice.…”

“…Although M2 and M3 receptors were not reduced significantly in the CON group compared to the OAB group, β2 and β3 receptors were reduced significantly in this study. Considering that β receptors in OAB mice were increased by a compensatory mechanism, 19 these results could be explained by decreased bladder overactivity after mirabegron treatment. Moreover, the P2X purinergic receptor, a marker related to bladder afferent hyperexcitability, was decreased in the CON group, suggesting that continuous administration of mirabegron can inhibit afferent hyperexcitability at the bladder level.…”

“…However, the role of these receptors in urothelial and suburothelial layers through the inhibition of afferent pathways also has been emphasized, given that the OAB medication, including mirabegron, does not affect the bladder contractility in most OAB patients, suggesting that OAB medications, including mirabegron, may have its additional effects on bladder afferent pathways 18 . In a previous study, the increased expressions in mucosal M2 and M3 receptor subtypes were associated with detrusor overactivity (DO) in spinal cord injured (SCI) mice, and they were reduced when DO was improved 19 . Also, β2‐ and β3‐adrenergic receptors are known to modulate smooth muscle relaxation in the bladder; however, in this study, they were increased in OAB mice.…”