Genetic Disorders – Development

Kidney International (2005) 67, 420–431; doi:10.1111/j.1523-1755.2005.67098.x

Exogenous BMP-4 amplifies asymmetric ureteric branching in the developing mouse kidney in vitro

JASON E CAIN, THIBAULD NION, DOMINIQUE JEULIN and JOHN F BERTRAM

Department of Anatomy and Cell Biology, School of Biomedical Sciences, Monash University, Victoria, Australia; Centre de Morphologie Mathématique, Ecole des Mines de Paris, Fontainebleau, France

Correspondence: Professor John Bertram, Ph.D., Department of Anatomy and Cell Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria, Australia 3800. E-mail:john.bertam@med.monash.edu.au

Received 13 July 2004; Revised 30 July 2004; Accepted 18 August 2004.

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Abstract

Exogenous BMP-4 amplifies asymmetric ureteric branching in the developing mouse kidney in vitro.

Background

 

Exogenous bone morphogenetic protein 4 (BMP-4) has been reported to inhibit ureteric branching morphogenesis and regulate the anterior-posterior axis of the developing kidney in vitro. We examined the role of BMP-4 on ureteric branching in vitro using three-dimensional image analysis software and statistical models. Additionally, in vivo ureteric branching was analyzed and the effect of reduced levels of BMP-4 in vivo on nephron number was examined.

Methods

 

Embryonic day 12.5 (E12.5) Balb/c mouse metanephroi cultured for 48 hours with or without 260 ng/mL recombinant human BMP-4 (rhBMP-4) were immunostained to identify the ureteric epithelium which was quantified in three dimensions. In vivo ureteric branching morphogenesis in Hoxb7/GFP mice was also analyzed. The effect of reduced in vivo levels of BMP-4 on nephron number was examined in BMP-4+/- and wild-type mice using an unbiased stereologic method.

Results

 

Qualitative and quantitative studies identified a decrease in total ureteric length and branch number in wild-type mouse metanephroi cultured in the presence of BMP-4. A marked anterior-posterior asymmetry in both ureteric length and branch number was observed in BMP-4-treated metanephroi. A similar asymmetry was revealed in control metanephroi, both in vitro and in vivo. This asymmetry is the result of reduced ureteric branching morphogenesis in the posterior region of the kidney and appears to be due to slower growth rather than the adoption of an alternate branching pattern. Reduction of endogenous BMP-4 in BMP-4+/- mice resulted in no change in total nephron number in macroscopically normal kidneys.

Conclusion

 

These results suggest that BMP-4 plays an important role in the regulation of ureteric branching morphogenesis, and that excess BMP-4 in vitro can amplify the existing asymmetry of the normal mouse kidney.

Keywords:

BMP-4, kidney; ureteric branching, development, asymmetry, stereology

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