Urothelial Inhibition of Transforming Growth Factor-β in a Bladder Tissue Recombination Model

Division of Pediatric Urology, Department of Urologic Surgery, Vanderbilt Children's Hospital, Nashville, Tennessee 37232-2765, USA.
The Journal of Urology (Impact Factor: 4.47). 11/2007; 178(4 Pt 2):1643-9. DOI: 10.1016/j.juro.2007.03.163
Source: PubMed


We examined the role of transforming growth factor-beta in urothelial and bladder development. Transforming growth factor-beta signaling was attenuated in the urothelial compartment and the subsequent effects were examined in a tissue recombination model.
Urothelium was cultured from adult rat bladders and transfected with control vector C7Delta or mutant DNIIR (dominant negative transforming growth factor-beta receptor II). Grafts were created by recombining transfected urothelium plus embryonic day 18 bladder mesenchyma and placed beneath the renal capsule of athymic mouse hosts. Grafts were harvested at 21 and 42 days. Final tissues were evaluated with staining and immunohistochemistry using hematoxylin and eosin, Gomori's trichrome strain, broad-spectrum uroplakin, smooth muscle actin-alpha, phosphorylated SMAD2 and Ki67 antigen. Bladder structures were defined as having smooth muscle, suburothelial connective tissue and mature urothelium expressing uroplakin. Urothelial compartment diameters were measured and subcategorized as small--0.10 to 0.40, medium--0.41 to 1.0 and large--greater than 1.1 mm.
At 21 days 14 C7Delta control and 15 DNIIR grafts were evaluated. No bladder tissue was seen in the C7Delta grafts vs 49 in DNIIR tissue, including 30 small, 9 medium and 10 large tissues. At 42 days 14 C7Delta and 12 DNIIR grafts were evaluated. Six bladder structures (5 small and 1 medium) were seen in the C7Delta cohort vs 27 (14 small, 7 medium and 6 large) in the DNIIR group. Immunohistochemical detection of phosphorylated-SMAD2 was significantly attenuated in DNIIR tissue. In addition, Ki67 proliferative indexes were 4.0-fold higher in the DNIIR cohort compared to those in C7Delta tissues.
We successfully observed that primary urothelium cultures can be genetically manipulated and recombined with undifferentiated mesenchyma to grow bladder tissue. By attenuating transforming growth factor-beta signaling in the urothelium superior bladder tissue growth occurred, suggesting that transforming growth factor-beta is a growth inhibitor in this organ system.

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    ABSTRACT: To compare the effects of various recombinant growth factors on bladder regeneration and angiogenesis for tissue engineering of bladder in patients with neurogenic bladder through in vitro cellular biological methods. Human bladder smooth muscle cells (HBSMCs) and human bladder urothelial cells (HBUCs) were cultured from patients with neurogenic bladder and used for comparative evaluations of various growth factors. Human umbilical vein endothelial cells (HUVECs) were also used. Eight potential growth factors, platelet-derived growth factor BB (PDGF-BB), platelet-derived growth factor CC (PDGF-CC), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), insulin-like growth factor 1 (IGF-1), hepatocyte growth factor (HGF), and transforming growth factor beta 1 (TGF-β1), were selected and their effects on the proliferation, migration, and wound healing of HBSMCs, HBUCs, and HUVECs were compared. PDGF-BB, PDGF-CC, bFGF, VEGF, IGF-1, or HGF enhanced the proliferation, migration, and wound healing of HBSMCs, whereas TGF-β1 inhibited their proliferation. Proliferation, migration, and wound healing of HBUCs and HUVECs were enhanced by bFGF, VEGF, EGF, IGF-1, or HGF, whereas inhibited by TGF-β1. PDGF-BB failed to enhance cell activity of HUVECs, whereas PDGF-CC could enhance their migration and wound healing. PDGF-BB, EGF, and VEGF were the most potent factors for stimulating the activities of HBSMCs, HBUCs, and HUVECs, respectively. Our findings suggest the potential use of a combination of PDGF-BB, EGF, and VEGF for bladder regeneration and angiogenesis. The synergetic effects of the three growth factors on cell activities in a three-dimensional scaffold and an animal model with neurogenic bladder need to be further evaluated.
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