Fig. 1.

Genome-wide expression profile of mRNA in internal anal sphincter (IAS) smooth muscle (SM) from younger and older rats. A: hierarchical clustering. Heat map shows differentially (↑ for increase, and ↓ for decrease) expressed mRNA detected in the IAS SM cells (SMCs) from 26-mo-old vs. 6-mo-old and 18-mo-old rats. The dendrogram illustrates the clustering tree resulting from hierarchical clustering of gene expression values (involved in SM phenotype and in contractile biomechanics). B: qPCR data for the selected transcripts validating downregulation of important SM markers (initially observed in the mRNA microarray profile) in aging IAS. These data reveal significant decreases in the expression levels in 26- vs. 6-mo-old group (*P < 0.05; n = 4; Student's t-test) but not in 18-mo-old vs. 6-mo-old group (P > 0.05).