Cell Stem Cell http://doi.org/bbm3 (2015)

On muscle injury, resident stem cells and their descendant myogenic progenitor cells orchestrate a regenerative response. Yet how muscle stem and progenitor cell populations become organized in vivo to replace degenerated muscle fibres and thus repair muscle tissue is poorly understood. By using three-dimensional, time-lapse intravital imaging in live mice, Chen-Ming Fan and colleagues now find that post-injury degenerated fibres in the basal lamina govern the division and migration of myogenic progenitor cells, with migration occurring primarily along the long axis of the fibres. They also show that artificial rotation of the remnant degenerated fibres negatively affects the migration and division behaviour of the progenitor cells. The researchers conclude that post-injury degenerated fibres provide a necessary scaffold for the proper alignment of progenitor cells and for the fusion of their differentiated descendants, which are critical stages for the proportional regeneration of muscle tissue (that is, with pre-injury organization and dimensions).