Imaging haematopoietic cells recruitment to an acute wound in vivo identifies a role for c-Met signalling.

We have used a direct in vivo imaging strategy to investigate the role of c-Met signalling and kinase activity during the immune response to wounding. Our assay utilizes the optical translucent properties of the zebrafish embryo and demonstrates the versatility of microscopy-based approach to the screening of compounds for inhibition of the wounding response. We have focussed on the c-Met pathway as little is known about the influence of c-Met signalling in immune responses, although it has been suggested that the c-Met tyrosine kinase receptor signalling pathway may be involved in cytokine secretion and directional migration in immune cells. Using both imaging of fixed zebrafish embryos in combination with digital time lapse microscopy of neutrophils recruited to a wound site, we find that pharmacological inhibition of c-Met, using a specific inhibitor, modulates the immune response in zebrafish embryos. We have found that inhibition of c-Met does not prevent the inflammatory response but does appear to limit recruitment and retention of immune cells at the wound site. This work demonstrates the versatility of using direct imaging assays for inhibitor studies and suggests that the HGF/c-Met signalling cascade plays an important role in the migration of haematopoietic cells in vivo.