title: Absence of desmin slightly prolongs myoblast proliferation and delays fusion in vivo in regenerating grafts of skeletal muscle.
abstract: The expression of desmin, a muscle-specific intermediate filament protein, is upregulated during skeletal myogenesis, but its role in the myogenic process is unclear. Postnatal skeletal muscle regeneration occurs to completion in desmin null (-/-) mice, however, only late time points (i.e., days 7 and 21) in the myogenic process have been examined. This study observes the early events in skeletal muscle regeneration (i.e., from 3 days) in desmin (-/-) mice. Whole muscle autografts were performed in desmin (-/-) and control normal (Balb/c) mice. Muscle samples were taken on days 3, 5, 6, 7, 8, 9 and 11 after transplantation, and regeneration was assessed by graft morphology, patterns of cell proliferation and quantitation of myotube numbers. At day 5 myotube formation was delayed in the desmin (-/-) grafts compared to the normal controls. Immunohistochemical analysis of proliferating cell nuclear antigen demonstrated a very high proportion of proliferating cells in the periphery of desmin (-/-) whole muscle grafts at day 5 compared to the controls, where mitosis in this area was negligible. This strongly indicates t hat myoblast proliferation is prolonged during postnatal myogenesis in the absence of desmin. By day 6 there was no marked morphological difference between desmin (-/-) and normal control whole muscle grafts, although the zonal pattern of myoblast replication was slightly delayed in the desmin (-/-) mice until day 8. These results indicate a slightly extended phase of myoblast proliferation with delayed fusion in vivo in mature regenerating desmin (-/-) skeletal muscle.
authors.affiliation: Department of Anatomy and Human Biology, The University of Western Australia, Nedlands, Perth.
authors.forename: G M
authors.initials: GM
authors.lastname: Smythe
authors.forename: M J
authors.initials: MJ
authors.lastname: Davies
authors.forename: D
authors.initials: D
authors.lastname: Paulin
authors.forename: M D
authors.initials: MD
authors.lastname: Grounds
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002455:Cell Division; D002459:Cell Fusion; D003433:Crosses, Genetic; D003893:Desmin / Q000378:metabolism / Q000502:physiology*; D007150:Immunohistochemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008815:Mice, Inbred Strains; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000637:transplantation*; D009218:Myosins / Q000276:immunology*; D018809:Proliferating Cell Nuclear Antigen / Q000276:immunology; D012038:Regeneration / Q000502:physiology*; D013045:Species Specificity; D013997:Time Factors; D014182:Transplantation, Autologous; D015854:Up-Regulation
chemical_list: D003893:Desmin; D018809:Proliferating Cell Nuclear Antigen; D009218:Myosins