Distinctive role of inflammation in tissue repair and regeneration.

Inflammation is an essential host defense mechanism in response to microbial infection and tissue injury. In addition to its well-established role in infection, inflammation is actively involved in the repair of damaged tissues and restoration of homeostatic conditions after tissue injury. The intensity of the inflammatory response and types of cells involved in inflammation have a significant impact on the quality of tissue repair. Numerous immune cell subtypes participate in tissue repair and regeneration. In particular, immune cell-derived secretants, including cytokines and growth factors, can actively modulate the proliferation of resident stem cells or progenitor cells to facilitate tissue regeneration. These findings highlight the importance of inflammation during tissue repair and regeneration; however, the precise role of immune cells in tissue regeneration remains unclear. In this review, we summarize the current knowledge on the contribution of specific immune cell types to tissue repair and regeneration. We also discuss how inflammation affects the final outcome of tissue regeneration.