AGING NORMAL AND DYSTROPHIC MOUSE MUSCLE - ANALYSIS OF MYOGENICITY INCULTURES OF LIVING SINGLE FIBERS

In the early stages of Duchenne muscular dystrophy, chronic muscle deg eneration is counterbalanced by regeneration whose progressive failure beyond the fifth year is attributed to an accelerated senescence asso ciated with excessive myogenic cell division, This idea was tested by counting the numbers of myogenic cells accumulating over 90 h around i ndividual living fibers isolated from muscles of dystrophic (mdx) and normal mice, 14-550 days of age, In cultures of normal muscle fibers, the number of myogenic cells per fiber decreased with increasing age o f the animal. Cultures from young mdx mice exhibited an age-related in crease in myogenic cell number, attaining at 50 days three times the n umber in control cultures. Thereafter, myogenic cell number progressiv ely declined with animal age to control values, Thus, there is no evid ence that extensive myoblast proliferation in young dystrophic mice-an d, by association, in Duchenne muscular dystrophy patients-depletes th eir myogenic responsiveness in later life when they become weak and wa sted. (C) 1998 John Wiley & Sons, Inc.