Biomedical Engineering Reference
In-Depth Information
Figure 6
Diagram modified from Ref. 64 showing some of the known features of
the interrelationships between stem cells, fibroblasts, myofibroblasts, and activated
myofibroblasts. The stellate myofibroblast can be found in the alveolar wall intersti-
tial space and are in a position to provide directional information to migrating leu-
kocytes. A variety of growth factors (indicated in the diagram) act with other
mediators that are not shown to stimulate the myofibroblast to secrete matrix
proteins. (From Refs. 75, 76.)
myofibroblasts. Although many cytokines and growth factors have been
incriminated in the activation process TGF-b1 appears to have the major
role in stimulating both the fibroblast and stellate myofibroblast to differ-
entiate to an activated myofibroblast phenotype capable of collagen secre-
tion (64,79-82). Tumor growth factor-b1 also has an indirect role in
initiating myofibroblast proliferation by upregulating PDGF receptors
and stimulating the production of CTGF (64,83). Other growth factors
including TGF-a a member of the epidermal growth factor (EGF) family,
as well as EGF itself GM-CSF, both acidic and basic FGF (aFGF and
