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

Planarians are simple, acoelomate, triploblastic organisms with a remarkabl e capacity of regeneration. In the last years, several specific cellular an d molecular markers have been used to study this biological problem in thes e organisms. Here, we monitor body-wall musculature restoration during ante rior regeneration through confocal microscopy and using a monoclonal antibo dy called TMUS-13, which recognizes the myosin heavy-chain of muscle cells. We have found differences in the dynamics of muscle pattern restoration be tween dorsal and ventral surfaces of the growing blastemas, especially duri ng the first days of regeneration. Blastema contains old longitudinal fiber s coming from the postblastema throughout all the regenerative process. The se fibers could have a role in supporting the growing blastema and/or guidi ng the entry of different cell types from the postblastema region. New long itudinal fibers within the blastema seem to appear from outgrowing processe s of the existing longitudinal fibers. On the other hand, new circular fibe rs appear de novo within the regenerative blastema. Finally, the original m uscle pattern seems to be restored through intercalation of new muscle fibe rs throughout an initial muscle scaffold.