Epidermal growth factor(EGF), a single chain polypeptide of 53 amino acids with a molecular weight of 6,045 Da, was first isolated from the male mouse submandibular glands. EGF stimulates cellular proliferation and differentiation in several tissues and accelerates the rate of wound healing. EGF is bound to the specific receptor(EGFR) on the cell membrane of its target cell. EGFR is a transmembrane glycoprotein with a molecular weight of 170,000 Da and is detectable on a large variety of cell types and tissues.
The authors investigated the expression of EGFR in the normal and inflamed human gingival epithelium to study the role of EGFR in the inflammation of the gingival epithelium, and the expression of EGFR in the dental follicle by using in situ mRNA hybridization and immunohistochenistry. The results weree as follows
1. The expression of EGFR mRNA in the normal gingival epithelium on in situ rnRNA hybridization was mainly localized on the basal cell layer, and the spinous layer was weakly positive The granular and cornified layers were negative
2. The expression of EGFR protein in the normal gingival epithelium on inmu nohistochenustry was localized on the cornified and granular layers, and the spinous layer was weakly positive. The basal cell layer was completely negative
3. The expression of EGFR mRNA in the inflamed gingival epithelium on in situ mRNA hybridization was evenly and homogeneously distributed in the whole layers of the gingival epithelium except the eornifaed layer. The staining intensity appeared to increase progressively from the basal cell layer to the comified layer.
4. The expression of EGFR protein in the inflamed gingival epithelium on immunohistochemistry was evenly and homogeneously distributed in the whole layers of the gingival epithelium. The staining intensity appeared to increase progressively from the cornified layer to the basal cell layer.
5. Strong positive reaction was seen in the epithelial cell rests of Malassez, whereas only background staining was seen in other cells of the dental follicle.
In conclusion, the up-regulation of EGFR in the inflamed gingival epithelium and the high amounts of EGFR in the epthelial cell rests of Malassez in the dental follicle can be regarded as responses to the possible damages to the oral environment to maintain the homeostatic conditions.
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