Paneth cells and their multiple functions

The small intestine mucosa is lined by specialized cells that form the crypt-villus axis, which expands its surface. Among the six intestinal epithelial cell types, the Paneth cell is located at the base of the crypt, and it contains numerous granules in its cytoplasm, composed of antimicrobial peptides, such as defensins and lysozyme, and growth factors, such as epidermal growth factor, transforming growth factor-α, and Wnt ligands. Together, these elements act in the defense against microorganisms, regulation of intestinal microbiota, maintenance, and regulation of stem cell identity. Pathologies that target Paneth cells can disturb such defense activity, but they also affect the maintenance of the stem cell niche. In that way, Crohn's disease, necrotizing enterocolitis, and graft-versus-host disease promote a reduction of Paneth cell population, and, consequently, secretion of their products into the lumen of the crypts, making the affected organism predisposed to infections and dysbiosis. Additionally, the emergence of new intestinal cells is also decreased. This review aims to address the main characteristics of Paneth cells, highlighting their multiple functions and the importance of their preservation to ensure bowel homeostasis.