Abstract
The main function of the stomach is to digest ingested food. Gastric antrum muscular contractions mix ingested food with digestive enzymes and stomach acid and propel the chyme through the pyloric sphincter at a rate in which the small intestine can process the chyme for optimal nutrient absorption. Mfge8 binding to α8β1 integrins helps regulate gastric emptying by reducing the force of antral smooth muscle contractions. The source of Mfge8 within gastric muscles is unclear. Since Mfge8 is a secreted protein, Mfge8 could be delivered via the circulation, or be locally secreted by cells within the muscle layers. In this study, we identify a source of Mfge8 within human gastric antrum muscles using spatial transcriptomic analysis. We show that Mfge8 is expressed in subpopulations of Mef2c(+) perivascular cells within the submucosa layer of the gastric antrum. Mef2c is expressed in subpopulations of NG2(+) and PDGFRB(+) pericytes. Mfge8 is expressed in NG2(+)/Mef2c(+) pericytes, but not in NG2(+)/Mef2c(-), PDGFRB(+)/Mef2c(-), or PDGFRB(+)/Mef2c(+) pericytes. Mfge8 is absent from CD34(+) endothelial cells but is expressed in a small population of perivascular ACTA2(+) cells. We also show that α8 integrin is not expressed by interstitial cells of Cajal (ICC), supporting the findings that Mfge8 attenuates gastric antrum smooth muscle contractions by binding to α8β1 integrins on enteric smooth muscle cells. These findings suggest a novel, supplementary mechanism of regulation of gastric antrum motility by cellular regulators of capillary blood flow, in addition to the regulation of gastric antrum motility by the enteric nervous system and the SMC, ICC, and PDGFRα(+) cell (SIP) syncytium.