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Abstract
Growth factors are biologically active mediators that bind to specific receptors on
target cells and regulate genes involved in cell growth, wound healing and regeneration.
The expression of these receptors is thus of fundamental importance for the response
of the cells to the factors. The aim here was to examine, using immunohistochemistry
and flow cytometry, the expression of growth factor receptors in normal gingiva, periodontal
ligament and in cells derived from these tissues, and also in regenerated tissues
following guided tissue regeneration (GTR). By immunocytochemistry platelet-derived
growth factor receptor-alpha (PDGF-Ralpha) was not detected in any of the tissues,
whereas the PDGF-Rbeta and transforming growth factor-beta receptor types I and II
(TGF-beta RI, RII) appeared to be upregulated in regenerated tissues compared with
gingival and periodontal ligament tissues. Epidermal growth factor receptor (EGF-R)
was also notably elevated in the regenerated tissue and was strongly expressed in
the gingival epithelium but not in the periodontal ligament. Neither were fibroblast
growth factor receptor-I (FGF-RI) or insulin-like growth factor receptor (IGF-R) detected
in the periodontal ligament, nor in the gingiva, but they sometimes stained weakly
in the regenerated tissues. Flow cytometry (FCM) showed that all the cells derived
from the normal gingiva and the periodontal ligament expressed the PDGF-Rbeta, whereas
the TGF-beta RI and RII, FGF-RI and IGF-R were detected in only a proportion of the
total cells. In contrast, none of the cells expressed the PDGF-Ralpha or the EGF-R.
These observations show that the growth factor receptors are differentially expressed
by the periodontal tissues and cells and suggest that the corresponding factors may
also be differentially involved in periodontal wound healing and regeneration.