Article

Urothelium-derived Sonic hedgehog promotes mesenchymal proliferation and induces bladder smooth muscle differentiation.

Department of Urology, University of California, San Francisco, Frank Hinman Jr. Urological Research Laboratory, 513 Parnassus Avenue, HSW 1434, San Francisco, CA, USA. <>
Differentiation (Impact Factor: 2.84). 03/2010; 79(4-5):244-50. DOI: 10.1016/j.diff.2010.02.002
Source: PubMed

ABSTRACT Induction of smooth muscle differentiation from bladder mesenchyme depends on signals that originate from the urothelium. We hypothesize Sonic hedgehog (Shh) is the urothelial signal that promotes bladder mesenchymal proliferation and induces bladder smooth muscle differentiation. Pregnant FVB mice were euthanized on embryonic day (E) 12.5 and fetal bladders were harvested. Two experimental protocols were utilized: Specimens were sized by serial sectioning. Cell counts were performed after trypsin digestion. Immunohistochemistry was performed to detect smooth muscle-specific protein expression. alpha-Actin expression was quantified using Western blot. All specimens were viable at 72h. BLM cultured without Shh survived but did not grow or undergo smooth muscle differentiation. IB cultured without Shh and BLM cultured with Shh grew and expressed smooth muscle proteins at 72h. IB cultured with Shh were larger and contained more cells than IB cultured without Shh (all p<0.05). Increasing Shh concentration from 48 to 480nM did not change bladder size, cell counts, or the level of alpha-actin expression. Prior to culture, IB did not express alpha-actin. After culture of IB in Shh-deficient media, alpha-actin was detected throughout the mesenchyme except in the submucosal layer. The IB submucosa was thinner after culture with 48nM Shh and smooth muscle completely obliterated the submucosa after culture with 480nM Shh. In fetal mouse bladders, urothelium-derived Shh is necessary for mesenchymal proliferation and smooth muscle differentiation. Shh concentration affects mesenchymal proliferation and patterning of bladder smooth muscle.

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    • "Tissue recombination experiments indicate that bladder urothelium is required to induce bladder mesenchyme to differentiate into smooth muscle via a diffusible signaling molecule [3], [7], [9]. Of particular interest, Sonic Hedgehog (Shh) and it's downstream signaling molecules have been shown to be involved in many epithelial-mesenchymal interactions during development, including proper bladder development and differentiation [10]–[16]. Shh is a secreted signaling molecule that interacts with the transmembrane receptor Patched (Ptch) resulting in repression of Ptch, and activation of Gli transcription factors in the target cell. Work by numerous labs indicates that this canonical Shh signaling pathway is involved in multiple processes, including cell fate determination, morphogenesis, differentiation, and apoptosis [13], [17]. "
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    ABSTRACT: In this study, we examined the expression of Sonic Hedgehog, Patched, Gli1, Gli2, Gli3 and Myocardin in the developing bladders of male and female normal and megabladder (mgb-/-) mutant mice at embryonic days 12 through 16 by in situ hybridization. This analysis indicated that each member of the Sonic Hedgehog signaling pathway as well as Myocardin displayed distinct temporal and spatial patterns of expression during normal bladder development. In contrast, mgb-/- bladders showed both temporal and spatial changes in the expression of Patched, Gli1 and Gli3 as well as a complete lack of Myocardin expression. These changes occurred primarily in the outer mesenchyme of developing mgb-/- bladders consistent with the development of an amuscular bladder phenotype in these animals. These results provide the first comprehensive analysis of the Sonic Hedgehog signaling pathway during normal bladder development and provide strong evidence that this key signaling cascade is critical in establishing radial patterning in the developing bladder. In addition, the lack of detrusor smooth muscle development observed in mgb-/- mice is associated with bladder-specific temporospatial changes in Sonic Hedgehog signaling coupled with a lack of Myocardin expression that appears to result in altered patterning of the outer mesenchyme and poor initiation and differentiation of smooth muscle cells within this region of the developing bladder.
    PLoS ONE 01/2013; 8(1):e53675. DOI:10.1371/journal.pone.0053675 · 3.23 Impact Factor
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    • "Furthermore, Cao et al. highlighted the importance of Shh signaling to mesenchymal-epithelial interactions during proper bladder development in mice with higher concentrations of Shh increasing both the number of cells and bladder size at 12-days gestation. However the presence of Shh without adjacent urothelium did not give rise to appropriate bladder development.[54] The abundance of Shh observed after STC, along with the importance of mesenchymal-epithelial interactions as described by Baskin and colleagues suggests that the Shh pathway may be responsible, at least in part, for aspects of functional bladder regeneration.[41], "
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