Reinnervation of motor endplate-containing and motor endplate-less muscle grafts☆

摘要

Damagedmusclefibersdegenerateandarephagocytosed,buttheirconnectivetissuesheathsandmyogeniccellssurvive.Newmyofibersregeneratewithintheconnectivetissuesheathandfunctionalreinnervationisrestored.Thepresentstudycomparedregeneratingmyofibersandtheirreinnervationinmusclegraftswheretheoriginalmotorendplateswereremovedandwhentheywerepresent.Inregeneratingmuscles,wheretheendplateswerepresent,axonsmadeneuromuscularconnectionswiththemyofibers.HighlevelsofCATactivity,characteristicofcholinergicinnervation,werereachedandmaintainedinthesemuscles.Also,motorendplate-containinggraftsdevelopedcharacteristicmusclefibertypesandnerve-evokedmusclecontractionwasobserved.Inpreparationslackingtheoriginalendplateregion,CATactivityinitiallyrosetohighlevels,butwithtimediminishedto17%ofcontrol,andmusclefibertypesdidnotdevelop.Musclecontractionafternervestimulationwasnotobservedinthesegrafts.Itwasconcludedthat,althoughasmallnumberofmotorendplatesareformedingraftsdevoidoforiginalmotorendplates,thepresenceofthemotorendplateregioninregeneratingmuscleiscriticalfordevelopmentandmaintenanceofmyofibersandtheaxonsthatcontactthem.