ARTIFICIAL BINDING GROWTH FACTORS - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 345

toheal.TG-P-NGFwasdesignedtobereleased“whencellsdemand.”
The activity of the fusion protein is approximately 40% that of
native NGF, when assayed by neurite extension in PC12 cells. Unlike
collagen-binding growth factors, this fusion protein binds to fibrin
covalently. This may relate to the reduced activity observed in an in
vitro assay.
The same or similar construct designs were applied to BMP2
(TG-pI-BMP-2), 31 KGF (P-KGF), 32 VEGF ( 2-PI1-8-VEGF121), 33 , 34

and ephrinB2. 35 The TG-pI-BMP-2-mediated elevation of alkaline
phosphatase activity in C3H10T1/2 cells was comparable with that
observed for native BMP2, while its retention in a fibrin gel was
higher than that of the native protein (60% vs. 25% of added
amount). The KGF fusion protein (P-KGF) binds to fibrin gel and
promotes the growth of epithelial cells after release from the gel.
VEGF121 is a VEGF isoform that lacks the fibrin-binding sequence
found in the major isoform (VEGF165). 36 Fusion with the α 2-pI
sequence enabled the incorporation of VEGF121 into a fibrin gel.
In addition, the fusion protein ( α 2-PI1-8-VEGF121) stimulated the
growth of endothelial cells on the gelin a dose-dependent manner.
Another fibrin-binding growth factor was reported recently 37 :a
chimericproteinofthefibronectinfibrin-bindingdomain(FBD)and
EGF. This fusion protein (FBD-EGF) binds to fibrin in the absence of
thecross-linkingenzyme(FXIIIa)andmaybesuitablefortheprepa-
rationoffibrin-basedscaffoldswithEGFactivity.Thewound-healing
potential of FBD-EGF was examined using an in vitro culture model
of keratinocyte sheets; repair of the injured sheet was enhanced by
fibrin-boundFBD-EGF butnotbyEGF alone.

α

17.3.3 Cell-Binding Fusion Proteins
Cell-binding growth factors were developed in the early 1990s by
employing the fibronectin cell-binding domain ( ∼ 30 kDa, including
the RGD sequence). The EGF fusion protein (C-EGF) 38 promotes the
proliferation of rat kidney fibroblasts. The bFGF fusion protein (FN-
FGF) 39 stimulatesthegrowthofendothelialcells(HUVEC);however,
its e cacy as compared with native bFGF was not clearly shown
in the same conditions. There are not many reports of attempts
at constructing cell-binding growth factors. This can probably be