Heparin induces alpha-smooth muscle actin expression in cultured fibroblasts and in granulation tissue myofibroblasts.
BACKGROUND
Heparin increases alpha-smooth muscle actin expression in smooth muscle cells in vivo and in vitro. It has been recently suggested that alpha-smooth muscle actin expression in fibroblasts is a marker of myofibroblastic differentiation. We have examined the effect of heparin and of four nonanticoagulant heparin derivatives on alpha-smooth muscle actin expression by fibroblasts in vitro and in vivo.


METHODS
For in vitro experiments, heparin was added for 7 days to different fibroblastic cultures. We studied cell proliferation and alpha-smooth muscle actin protein and mRNA expression. For in vivo studies, osmotic minipumps filled with NaCl or tumor necrosis factor-alpha without or with nonanticoagulant heparin were implanted subcutaneously. After 14 days, newly accumulated connective tissues around the pumps were processed for immunofluorescence and electron microscopic and biochemical studies.


RESULTS
In vitro, heparin inhibited proliferation and increased the expression of alpha-smooth muscle actin protein and mRNA. Analysis of [3H]thymidine incorporation in synchronized cells suggested that heparin produces a selection of alpha-smooth muscle actin expressing cells. In vivo, the local application of tumor necrosis factor-alpha resulted in formation of a typical granulation tissue: immunofluorescence showed that accumulated fibroblastic cells express alpha-smooth muscle actin only in the presence of heparin derivatives. In tumor necrosis factor-alpha treated animals, electron microscopic examination established the presence of myofibroblasts, but alpha-smooth muscle actin was expressed in microfilament bundles only in the presence of heparin derivatives.


CONCLUSIONS
These results show that heparin and its nonanticoagulant derivatives influence the expression of alpha-smooth muscle actin in fibroblastic cells both in vitro and in vivo and that this effect is probably related to the selection of a particular cell subpopulation. They suggest a possible role for heparin during the formation and evolution of granulation tissue.
Desmoulière
A
A
Department of Pathology, University of Geneva, Centre Médical Universitaire, Switzerland.
Rubbia-Brandt
L
L
Grau
G
G
Gabbiani
G
G
D000199:Actins / Q000032:analysis / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D015415:Biomarkers; D002454:Cell Differentiation; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006097:Granulation Tissue / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D015151:Immunoblotting; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D014409:Tumor Necrosis Factor-alpha
D000199:Actins; D015415:Biomarkers; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D006493:Heparin