Mir-29 Repression in Bladder Outlet Obstruction Contributes to Matrix Remodeling and Altered Stiffness

Abstract

Recent work has uncovered a role of the microRNA (miRNA) miR-29 in remodeling of the extracellular matrix. Partial bladder outlet obstruction is a prevalent condition in older men with prostate enlargement that leads to matrix synthesis in the lower urinary tract and increases bladder stiffness. Here we tested the hypothesis that miR-29 is repressed in the bladder in outlet obstruction and that this has an impact on protein synthesis and matrix remodeling leading to increased bladder stiffness. c-Myc, NF-κB and SMAD3, all of which repress miR-29, were activated in the rat detrusor following partial bladder outlet obstruction but at different times. c-Myc and NF-κB activation occurred early after obstruction, and SMAD3 phosphorylation increased later, with a significant elevation at 6 weeks. c-Myc, NF-κB and SMAD3 activation, respectively, correlated with repression of miR-29b and miR-29c at 10 days of obstruction and with repression of miR-29c at 6 weeks. An mRNA microarray analysis showed that the reduction of miR-29 following outlet obstruction was associated with increased levels of miR-29 target mRNAs, including mRNAs for tropoelastin, the matricellular protein Sparc and collagen IV. Outlet obstruction increased protein levels of eight out of eight examined miR-29 targets, including tropoelastin and Sparc. Transfection of human bladder smooth muscle cells with antimiR-29c and miR-29c mimic caused reciprocal changes in target protein levels in vitro. Tamoxifen inducible and smooth muscle-specific deletion of Dicer in mice reduced miR-29 expression and increased tropoelastin and the thickness of the basal lamina surrounding smooth muscle cells in the bladder. It also increased detrusor stiffness independent of outlet obstruction. Taken together, our study supports a model where the combined repressive influences of c-Myc, NF-κB and SMAD3 reduce miR-29 in bladder outlet obstruction, and where the resulting drop in miR-29 contributes to matrix remodeling and altered passive mechanical properties of the detrusor.

Characterization of miRNA-regulated networks, hubs of signaling, and biomarkers in obstruction-induced bladder dysfunction

“…We identified JUND, BDNF, and CCND1 among hubs of signaling activity targeted by miR-1 in human BOO patients. A recent expression profile in a rat pBOO model showed a decrease of miR-29b and miR29c concomitant with an upregulation of c-Myc, NFkB, and SMAD3 (16). Our results confirm these findings in human patients with BOO.…”

“…Reliable markers of bladder function are urgently needed in order not to surpass the "point of no return," leading to bladder decompensation and failure. The studies of individual cellular signaling pathways conducted in animal models (5-7) identified some of the regulated genes typical for a specific symptomatic state; similarly, a number of regulatory miRNAs have been implicated in bladder pathologies (8)(9)(10)(11)(12) and function (13). Increasing evidence indicates that miRNAs may play a role in the regulation of urothelial permeability (14) and bladder contractility (15,16).…”

Induction of angiotensin-converting enzyme after miR-143/145 deletion is critical for impaired smooth muscle contractility

“…We reported 1) increased matrix area between smooth muscle cells, 2) reduced depolarization-induced contraction, and 3) a pronounced impairment of the cholinergic component of neurogenic bladder activation. We have subsequently attributed the increased matrix area in the dicer KO bladder to miR-29 (14), which targets multiple extracellular matrix proteins, but the miRNAs responsible for the reduction of depolarization-induced contraction and impaired neurogenic activation have not been identified. We show here that depolarization-induced contraction and neurogenic activation is maintained in miR-143/145 KO bladders, arguing that miRNAs other than miR-143/145 must be responsible for reduced depolarization-induced contraction and neurogenic activation in dicer KO bladders.…”

Increased susceptibility of estrogen-induced bladder outlet obstruction in a novel mouse model

“…To our knowledge, this is the first time to report bladder-neck fibrosis associated with BOO. The bladder-body detrusor fibrosis has been reported in rodents with surgical obstruction of urethra, [36][37][38] aromatase-overexpressing mice 6 and T þ E2-treated mice. 12 The abnormal deposition of collagen in the bladder neck and body, as a consequence of urinary obstruction, may further increase the stiffness and matrix rigidity of LUT leading to the decompensated stage of BOO.…”