Macroautophagy/autophagy defects are a risk factor for inflamatory bowel disease (IBD), but the mechanism remains unclear. We previously demonstrated that conditional whole-body deletion of the essential Atg7 (autophagy related 7) gene in adult mice (atg7Δ/Δ) causes specific tissue damage and shortens lifespan to three months primarily due to neurodegeneration with surprisingly no disturbing effects on the intestine. In contrast, we recently found that conditional whole-body deletion of other essential autophagy genes, Atg5 or Rb1cc1/Fip200 (atg5Δ/Δ or rb1cc1Δ/Δ), cause death within five days due to rapid inhibition of autophagy, elimination of intestinal stem cells, and loss of barrier function in the ileum. atg5Δ/Δ mice lose PDGFRA/PDGFRα+ mesenchymal cells (PMCs) and WNT signaling essential for stem cell renewal. Depletion of aspartate and nucleotides in atg5Δ/Δ ileum was revealed by novel mass-spectrometry imaging (MALDI-MSI), consistent with metabolic insufficiency underlying PMCs loss. The difference in the autophagy gene knockout phenotypes is likely due to distinct kinetics of autophagy loss because gradual whole-body atg5 deletion extends lifespan, phenocopying deletion of Atg7 or Atg12. Therefore, we established that autophagy is required for ileum PMC metabolism, stem cell maintenance and mammalian survival. PMC loss caused by autophagy deficiency may therefore contribute to IBD.
Keywords: Autophagy; IBD; Pdgfrα+ mesenchymal cells; WNT signaling; intestinal stem cells.