A functional role for the 'fibroblast-like cells' in gastrointestinal smooth muscles.

Smooth muscles, as in the gastrointestinal tract, are composed of several types of cells. Gastrointestinal muscles contain smooth muscle cells, enteric neurons, glial cells, immune cells, and various classes of interstitial cells. One type of interstitial cell, referred to as 'fibroblast-like cells' by morphologists, are common, but their function is unknown. These cells are found near the terminals of enteric motor neurons, suggesting they could have a role in generating neural responses that help control gastrointestinal movements. We used a novel mouse with bright green fluorescent protein expressed specifically in the fibroblast-like cells to help us identify these cells in the mixture of cells obtained when whole muscles are dispersed with enzymes. We isolated these cells and found they respond to a major class of inhibitory neurotransmitters - purines. We characterized these responses, and our results provide a new hypothesis about the role of fibroblast-like cells in smooth muscle tissues.