EXPRESSION OF KERATINOCYTE GROWTH-FACTOR IN PERIAPICAL LESIONS

The epithelial proliferation associated with inflammatory periapical l esions and with periapical cyst formation represents an interesting bu t poorly understood pathological change. Keratinocyte growth factor (K GF) is a recently identified growth factor that is produced by stromal fibroblasts and acts specifically to stimulate epithelial growth and differentiation. To investigate its possible role in the activation of the normally quiescent rests of Malassez, we examined the expression of KGF by in situ hybridization of sections of normal periodontal liga ment (PDL) and of 12 periapical granulomas or cysts. Normal PDL and pe riapical granulomas with scant inflammatory infiltration showed few ce lls expressing message for KGF. However, KGF-expressing cells were fou nd in the connective tissue stroma close to dense foci of inflammatory cells and to proliferating epithelial elements and cystic epithelial linings. Examination of tissues by the reverse-transcription polymeras e chain reaction (RT-PCR) showed KGF expression in 4 specimens of peri apical lesions but low or undetectable levels in normal PDL. These obs ervations suggest that the induction of KGF expression in the stromal cells of periapical lesions may play an important role in stimulating the epithelial proliferation associated with cyst formation.