The effect of enamel matrix protein derivative on follicle cells in vitro

Background: It is thought that during development of the periodontium, dent al follicle cells, when appropriately triggered, have the ability to differ entiate into periodontal ligament fibroblasts, cementoblasts, and osteoblas ts. However, the exact mechanisms/factors responsible for initiating cell d ifferentiation are not defined. The purpose of this in vitro study was to f urther characterize follicle cells and to determine the effects of an ename l matrix-derived protein (EMD) on these cells. Methods: Murine follicle cells, transformed with simian virus 40 (SV 40) T antigen-containing virus (SVF cells), were used. SVF cells were cultured in Dulbecco's modified Eagle's medium (DMEM) plus 2% fetal bovine serum (FBS) or 2% FBS plus EMD (100 mug/ml), with and without ascorbic acid (50 mug/ml ). For proliferation assays, cells were plated at 500 cells/cm(2) in 24-wel l plates and counted on days 3, 4, and 5. For Northern analysis, total RNA was isolated on days 8, 12, and 18. Induction of mineral nodules by SVF cel ls was determined by von Kossa staining. Results: EMD had a significant proliferative effect on SVF cells, when comp ared with 2% FBS control. Based on investigations in situ, follicle cells a t the time point used here do not express key mineral-associated markers, e .g., osteocalcin (OCN) or bone sialoprotein (BSP). Significantly, by day 12 in culture, Northern analysis indicated that the follicle cells expressed transcripts for BSP, OCN, and osteopontin (OPN). EMD increased OPN mRNA and decreased OCN mRNA expression. SVF cells were capable of inducing minerali zation on day 18, but EMD blocked this activity. Conclusions: These results suggest the follicle cells have the capacity to act as cementoblasts or osteoblasts. Furthermore, EMD can regulate follicle cell activity, thus suggesting that epithelial-mesenchymal interactions ma y be important during development of periodontal tissues.