Establish a novel phenytoin-induced gingival overgrowth (PIGO) mouse model by continuous administration of phenytoin to mice. Evaluate gingival changes macroscopically and microscopically in the context of epithelial to mesenchymal transition (EMT).
Method:
8-Week old BALB/cByJ mice were recruited and devided into a control group recieving phosphate buffer saline (N=6) and a treatment group (PHE) receiving phenytoin (0.6 mg/day/20 g mouse,N=6). Drugs were delivered by utilizing Alzet-miniosmotic pumps implanted subcutaneously and replaced every 2 weeks for 10 weeks. At week 12, mice were sacrified, gross gingival images were taken and maxillary anterior gingival tissues were processed for histology. Histomorphometric analysis was performed by analyzing epithelial thickness and epithelial area labially and palatally. Immunohistochemical (IHC) analysis was performed to determine the expression levels of selected EMT markers: E-cadherin, Connective Tissue Growth Factor (CTGF), collagen type IV (Col-IV), alternatively spliced fibronectin EIIIa (FN-EDA), TGF-β1 and lysyl oxidase like-2 (LOXL-2).
Result:
Gross morphology data showed a trend toward increasing the size of the maxillary anterior interdental papilla in PHE. Histomorphometric analysis of PHE mice revealed labial and palatal thickening (p<0.02, p<0.001), and enlarged labial epithelia (p<0.00001). Qualitative IHC analysis showed lower E-cadherin expression toward the basal epithelium in PHE mice. Collagen-IV expression was thinner in PHE mice. CTGF and LOXL-2 were each expressed in the epithelium and in the connective tissue of both groups. FN-EDA and TGF-β1 expression will be further investigated.
Conclusion:
Results indicate that we have developed a novel PIGO mouse model in which drug administeration is continuous. Other forms of drug induced gingival overgrowth (DIGO) in-vivo models may be developed following the same study design. These models will provide tools to monitor the temporal cellular and molecular relationships in DIGO in-vivo and will permit evaluation of novel therapeutic approaches.