Body-wall muscle restoration dynamics are different in dorsal and ventral blastemas during planarian anterior regeneration

Planarians are simple, acoelomate, triploblastic organisms with a remarkable capacity of regeneration. In the last years, several specific cellular and molecular markers have been used to study this biological problem in these organisms. Here, we monitor body-wall musculature restoration during anterior regeneration through confocal microscopy and using a monoclonal antibody called TMUS-13, which recognizes the myosin heavy-chain of muscle cells. We have found differences in the dynamics of muscle pattern restoration between dorsal and ventral surfaces of the growing blastemas, especially during the first days of regeneration. Blastema contains old longitudinal fibers coming from the postblastema throughout all the regenerative process. These fibers could have a role in supporting the growing blastema and/or guiding the entry of different cell types from the postblastema region. New longitudinal fibers within the blastema seem to appear from outgrowing processes of the existing longitudinal fibers. On the other hand, new circular fibers appear de novo within the regenerative blastema. Finally, the original muscle pattern seems to be restored through intercalation of new muscle fibers throughout an initial muscle scaffold.