Cell phenotypic conversion and fate change during the host defense response, tissue injury and repair.

In the process of host response to insults of serious injury/intense stressor, many types of somatic cells can undergo phenotypic conversion and fate change. The typical feature of cell conversion in this circumstance is to acquire the status of upstream precursors, which commonly accompanies transcriptional alteration to enhance cell proliferation and increase the plasticity of differentiation toward the lineage(s) needed in urgency for defending host against injury as well as maintaining/restoring the integrity of organ tissue function. The extent of cell conversion varies dependent on cell types and insult properties. Pattern ligands derived from pathogens and damaged tissues as well as the dynamic changes in systemic neurohumoral environment and local niche cue mediate cell conversion. Distinctive signaling interplays are involved in regulating various types of cell conversion. Better understanding the phenomena of cell conversion and their underlying regulatory mechanisms is critical for advancing regenerative medicine and developing novel therapeutic strategies to promote host defense as well as optimal repair of organ tissue injury. This article reviews recent progress in investigation on cell conversion and state change in different organ tissue environments with focus on bone marrow, vascular endothelium, lung, liver, and intestine. Discussion on delineating the signaling mechanisms is extended. Efforts in exploring the correlated therapeutic approaches are addressed to highlight the substantial potential in clinical application for this field of regenerative medicine.