Keratinocytes modify fibroblast metabolism in hereditary gingival fibromatosis

Hereditary gingival fibromatosis (HGF) is a rare benign disorder characterized by progressive fibrous overgrowth of the gingiva. The proliferation and expression of growth factors of HGF keratinocytes are abnormal. However, the exact role of keratinocytes in HGF pathogenesis is still unknown. The present study aimed to clarify the interactions between HGF keratinocytes and underlying fibroblasts in the pathogenesis of HGF.

Gingival tissues, fibroblasts and keratinocytes from three Chinese HGF patients and three healthy subjects were collected. Histological analyses were performed by histochemical and immunohistochemical staining (Ki-67). Gingival fibroblasts were cocultured with gingival keratinocytes in an in vitro coculture system. The mRNA levels of type I collagen, MMP-1, MMP-3, and TIMP-1 were analysed in the cocultured gingival fibroblasts by reverse-transcription polymerase chain reaction (RT-PCR). The production of type I collagen and TIMP-1 was examined by ELISA.

The number of Ki-67-positive keratinocytes in tissue sections from patients was higher than in those from controls. HGF fibroblasts cocultured with HGF keratinocytes showed an increased expression of type I collagen and TIMP-1. Transmission electron microscopy showed increased rough endoplasmic reticulum and ribosomes in cocultured HGF fibroblasts.

These results suggest that HGF keratinocytes have an important role in HGF pathogenesis by inducing extracellular matrix (ECM) accumulation by fibroblasts.