Microarray analysis of bladder smooth muscle from patients with myelomeningocele

To examine whether gene profiles can provide a molecular evaluation of the quality and therapeutic potential in patients with myelomeningocele (MM), by comparing genetic profiles of smooth muscle cells (SMCs) from healthy bladders and bladders from patients, to identify genes that are over- and under-expressed in MM bladder SMCs.

Bladder SM biopsies were obtained from 'healthy' subjects undergoing bladder surgery for vesico-ureteric reflux and from patients with a neurogenic bladder secondary to MM. Bladder SMCs were expanded in vitro and total RNA was isolated and hybridized to gene chips to evaluate the differential expression levels of 22 283 genes. Differentially expressed genes were identified by two methods. In the first analysis, we directly compared raw data sets of healthy SMCs to those derived from patients with MM. In the second analysis, we indirectly compared healthy SMCs and MM SMCs to a reference file, to create a genetic signature of genes that are over- and under-expressed in MM SMCs.

The direct analysis identified 240 genes that were over-expressed and 104 that were under-expressed in MM SMCs. Gene ontology classifications were used to identify biological themes and pathways. Genes that were over-expressed in MM SMCs were involved in development: mesenchyme homeobox 2 (-fold change, 9.3); bone morphogenic protein 6 (4.0); fibroblast growth factor 2 (4.8); inhibin A (4.2), cartilage oliogomeric matrix protein (9.97); collagen 11A (6); collagen 5A2 (3) and collagen 1A1 (2.18). The indirect analysis identified 665 genes that were over-expressed and 1343 that were under-expressed in MM SMCs. Pathway-based analysis of these genetic signatures showed an over-expression of genes involved in muscle development and focal adhesion/extracellular matrix interactions. Genes that were under-expressed in MM SMCs were mapped to muscle contraction, transmission of nerve impulses, and cell-cell adhesion pathways.

Our results are consistent with previous studies showing that MM bladders have an excess of extracellular matrix deposition, improper contraction, and are developmentally immature relatively to healthy SMCs. The clinical implication of microarray analysis of MM SMCs is that it provides potential targets that could induce muscle differentiation and inhibit extracellular matrix production.