Fibrocytes, Inflammation, and Fibrosis in Crohn's Disease: Another Piece of the Puzzle.

In the gut and in other organs, tissue repair following damage results from the complex interplay of chemokines, cytokines and growth factors that recruits and activates cells into the site of injury. During the initial inflammatory phase, monocytes and neutrophils remove the damaged tissue, secreting substances that activate acquired immunity, promoting tissue repair. Fibroblast activation and recruitment (as well as angiogenesis) occur at this time, mostly in response to increasing concentrations of growth factors and proinflammatory cytokines such as IL-1, IL-6, and TNF-a. Subsequently, re-epithelization accompanied by collagen/extracellular matrix (ECM) deposition and remodeling take place until specialized cells with contractile capability such as fibroblast-derived myofibroblasts restore original tissue integrity.