The inflammatory cytokine IL-1β is involved in bladder remodeling after bladder outlet obstruction in mice

We investigated the relationship between IL-1β and morphological and functional changes following partial bladder outlet obstruction (pBOO).

Female wild-type C57/BL6 mice (WT) and IL-1β-/- mice (KO) were used. Animals were sacrificed either 1 or 3 weeks after pBOO or sham surgery, and their bladders were harvested to determine bladder weight, for RT-PCR to measure interleukin-1β (IL-1β), insulin growth factor-1 (IGF-1), and transforming growth factor-β (TGF-β) levels, and for histological analysis with Hematoxylin-Eosin (HE) staining. Cystometry was performed on conscious animals 3 weeks after surgery to evaluate urodynamic parameters. IGF-1 was also administered intraperitoneally to KO with pBOO, and bladder weight was then investigated.

IL-1β-mRNA levels were significantly higher in WT-pBOO than in WT-sham. IGF-1-mRNA and TGF-β-mRNA levels were also significantly higher in WT-pBOO than in WT-sham; however, these increases were smaller in KO-pBOO than in WT-pBOO. Bladder weight was significantly higher in WT-pBOO than in WT-sham, while increases in bladder weight were significantly suppressed in KO-pBOO. HE staining revealed the thickened bladder wall in WT-pBOO, and this phenomenon was less in KO-pBOO than in WT-pBOO. Regarding the urodynamic parameters examined, micturition pressure and bladder capacity were significantly higher in WT-pBOO than in WT-sham, but remained unchanged in KO-pBOO. The administration of IGF-1 to KO-pBOO led to similar increases in bladder weight and the thickened bladder wall as those observed in WT-pBOO.

IL-1β has the potential to induce bladder remodeling and deteriorate urodynamic parameters in pBOO.