Osteopontin and skeletal muscle myoblasts: association with muscle regeneration and regulation of myoblast function in vitro.
Osteopontin is a secreted glycoprotein expressed by many cell types including osteoblasts and lymphocytes; it is a constituent of the extracellular matrix (ECM) in bone, and a mitogen for lymphocytes. To investigate the role of osteopontin in muscle repair and development, expression of osteopontin by muscle cells in vivo and in vitro, and the effects of osteopontin on myoblast function in vitro were investigated. Osteopontin staining was weak in sections of muscle from normal mice, but associated with desmin-positive cells in areas of regeneration in muscles from mdx mice. In immunocytochemical, PCR and ELISA studies, cultured myoblasts were found to express osteopontin and secrete it into medium. Treatment of myoblast cultures with fibroblast growth factor-2, transforming growth factor beta1, interleukin-1beta or thrombin significantly increased osteopontin expression. Osteopontin-coated substrata promoted adhesion and fusion, but not proliferation or migration, of myoblasts. The effect of osteopontin on myoblast adhesion was RGD-dependent. In solution, osteopontin significantly increased proliferation and decreased fusion and migration of myoblasts. These results suggest that myoblasts are an important source of osteopontin in damaged muscle and that osteopontin released by myoblasts may assist in controlling both the myogenic and inflammatory processes during the early stages of muscle regeneration.
Uaesoontrachoon
Kitipong
K
School of Veterinary Science, University of Melbourne, Parkville, Victoria 3010, Australia.
Yoo
Hyun-Jin
HJ
Tudor
Elizabeth M
EM
Pike
Robert N
RN
Mackie
Eleanor J
EJ
Pagel
Charles N
CN
D000818:Animals; D002448:Cell Adhesion; D002454:Cell Differentiation; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D006614:Hindlimb / Q000473:pathology; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D018482:Muscle, Skeletal / Q000166:cytology* / Q000502:physiology*; D009137:Muscular Dystrophy, Animal; D032448:Myoblasts, Skeletal / Q000166:cytology*; D053495:Osteopontin / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D012038:Regeneration; D012995:Solubility
D053495:Osteopontin