Gene Expression Changes Associated with Respiratory Muscle Hypertrophy after Intermittent Transient Tracheal Occlusions

The effect of intermittent transient tracheal occlusion (ITTO) on gene expression was compared in the diaphragm and parasternal intercostals. We hypothesized that genes responsible for protein metabolism, myogenic activation, neuromuscular transmission, and inflammatory modulation would be altered in animals exposed to this rodent model of respiratory load compensation rehabilitation. Eight adult male Sprague-Dawley rats underwent placement of a tracheal occluder cuff and were divided into ITTO (n=4) or SHAM (n=4) treatment groups. Animals received 10 days of their assigned treatments. The day following the last treatment session, the animals were euthanized and the diaphragm and parasternals extracted. Messenger RNA was profiled with microarray analysis (Amadid: 028279, Agilent Technologies, Palo Alto, CA). Results were further analyzed with immunofluorescent examination of cross-sectional area and with quantitative reverse transcriptase polymerase chain reaction on a subset of genes exhibiting differential expression. The cross-sectional area of type IIx/b fibers was larger in the muscles of ITTO-trained animals. Microarray analysis identified 650 genes in the diaphragm and 1,181 genes in the intercostals that were differentially expressed between the groups (p<.01). In both muscles, biological processes for cell adhesion and chemical stimulus for the detection of olfaction biological processes were over-expressed. Additionally, we found significant differential expression of the g-protein signaling pathway and protein-amino acid phosphorylation in the intercostals. The results provide insight into neuromuscular plasticity associated with respiratory load compensation rehabilitation. Four experimental animals that received tracheal occlusions and four surgical control animals were used. Intercostal and diaphragm muscles were excised and analyzed separately.