Microfilament modification by dihydrocytochalasin B causes retinoic acid-modulated chondrocytes to reexpress the differentiated collagen phenotype without a change in shape.
Primary monolayers of rabbit articular chondrocytes synthesize high levels of type II collagen and proteoglycan. This capacity was used as a marker for the expression of the differentiated phenotype. Such cells were treated with 1 microgram/ml retinoic acid (RA) for 10 d to produce a modulated collagen phenotype devoid of type II and consisting of predominantly type I trimer and type III collagen. After transfer to secondary culture in the presence of RA, the stability of the RA-modulated phenotype was investigated by culture in the absence of RA. Little reexpression of type II collagen synthesis occurred in this period unless cultures were treated with 3 X 10(-6) M dihydrocytochalasin B to modify microfilament structures. Reexpression of the differentiated phenotype began between days 6-8 and was essentially complete by day 14. Substantial reexpression occurred by day 8 without a detectable increase in cell rounding. Colony formation, characteristic of primary chondrocytes, was infrequent even after reexpression was complete. These data suggest that the integrity of microfilament cytoskeletal structures can be a source of regulatory signals that mechanistically appear to be more proximal to phenotypic change than the overt changes in cell shape that accompany reexpression of subculture-modulated chondrocytes in agarose culture.
Benya
P D
PD
Department of Orthopedics, Orthopedic Hospital, University of Southern California, Los Angeles 90007-2697.
Brown
P D
PD
Padilla
S R
SR
D008841:Actin Cytoskeleton / Q000187:drug effects* / Q000648:ultrastructure; D000818:Animals; D001769:Blood; D002356:Cartilage / Q000166:cytology*; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D003094:Collagen / Q000502:physiology*; D003470:Culture Media; D003488:Cyanogen Bromide; D003571:Cytochalasin B / Q000031:analogs & derivatives* / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects*; D005455:Fluorescent Antibody Technique; D010449:Peptide Mapping; D011509:Proteoglycans / Q000096:biosynthesis; D011817:Rabbits; D014212:Tretinoin / Q000494:pharmacology*
D003470:Culture Media; D011509:Proteoglycans; C024794:dihydrocytochalasin B; D003571:Cytochalasin B; D014212:Tretinoin; D003094:Collagen; D003488:Cyanogen Bromide