Differential expression of genes related to purinergic signaling in smooth muscle cells, PDGFRα-positive cells, and interstitial cells of Cajal in the murine colon

Background Purinergic signaling provides regulation of colonic motility. Smooth muscle cells (SMC), interstitial cells of Cajal (ICC), and platelet-derived growth factor receptor a-positive (PDGFR alpha(+)) cells are electrically coupled and form a functional (SIP) syncytium that constitutes the receptive field for motor neurotransmitters in the tunica muscularis. Each cell type in the SIP syncytium has specialized functions in mediating motor neurotransmission. We compared gene transcripts for purinergic receptors and membrane-bound enzymes for purine degradation expressed by each cell type of the SIP syncytium. Methods Fluorescence-activated cell sorting (FACS) was used to purify SMC, ICC, and PDGFR alpha(+) cells from mixed cell populations of colonic muscles dispersed from reporter strains of mice with constitutive expression of green fluorescent proteins. Differential expression of functional groups of genes related to purinergic signaling was determined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Key Results We detected marked phenotypic differences among SMC, ICC, and PDGFR alpha(+) cells. Substantial numbers of genes of importance in purinergic neurotransmission were enriched in PDGFR alpha(+) cells in relation to SMC and ICC. Notably, genes related to mediating effects and extracellular biotransformation of enteric purinergic inhibitory neurotransmitters were strongly expressed by PDGFR alpha(+) cells. Conclusions & Inferences Our results demonstrate differential expression of genes for proteins involved in purinergic signaling in the SIP syncytium. These results may further clarify the specific functions of each cell type, identify novel biomarkers for postjunctional cells, and provide hypotheses for further studies to understand the physiological roles of cells of the SIP syncytium.