Platelet-derived growth factor-B induces transformation of fibrocytes into spindle-shaped myofibroblasts in vivo.
Platelet-derived growth factor (PDGF) has a targeted activity on mesenchymal cells, but the in vivo effects of PDGF are not well understood. We have applied about 3 microg of PDGF-A and PDGF-B on the differentiated chorioallantoic membrane (CAM) of 13-day-old chick embryos. After 1-3 days, specimens were evaluated macroscopically, histologically with semi- and ultrathin sections, and immunohistologically with antibodies against smooth muscle alpha-actin (alphaSMA), desmin, and fibronectin (FN). Proliferation studies were performed according to the 5-bromo-2-deoxyuridine (BrdU)/anti-BrdU method. We did not observe effects of PDGF-A. PDGF-B induced proliferation of fibrocytes and their transformation into myofibroblasts. Bundles of spindle-shaped myofibroblasts accumulated beneath the chorionic epithelium. These cells were strongly positive for alphaSMA and FN, but negative for desmin. They possessed a well developed rough endoplasmic reticulum and bundles of microfilaments anchoring in the cell membrane. Our results suggest that PDGF-B is a "transforming" growth factor with important functions during formation of granulation tissue which are closely comparable to the effects of the PDGF-B-like protein of simian sarcoma virus. PDGF-B also induced vascular alterations in the CAM, which, however, appeared to be a secondary effect. While the intra-chorionic capillaries were lost, an accumulation of small vessels positive for alphaSMA was observed. This indicates a function for PDGF-B during segregation of main vessels from a primary vascular plexus.
Oh
S J
SJ
Anatomisches Institut II, Albert-Ludwigs-Universität Freiburg, Germany.
Kurz
H
H
Christ
B
B
Wilting
J
J
D000199:Actins / Q000032:analysis; D000818:Animals; D000077214:Becaplermin; D002454:Cell Differentiation; D002642:Chick Embryo; D003893:Desmin / Q000032:analysis; D005347:Fibroblasts / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects*; D005353:Fibronectins / Q000032:analysis; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins / Q000494:pharmacology*
D000199:Actins; D003893:Desmin; D005353:Fibronectins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins; C075278:platelet-derived growth factor A; D000077214:Becaplermin