Development and Characterization of a Transformed Human Periodontal Ligament Cell Line

PERIODONTAL LIGAMENT (PDL) CELLS ARE THOUGHT to be important for establishing and maintaining a stable interface between bone and teeth. In addition, PDL cells are thought to play critical roles in both the pathogenesis of periodontal disease and the regeneration of periodontal ligament tissues. The purpose of this study was to develop a continuous or stable human PDL cell line as an in vitro model for the investigation of cellular mechanisms involved in periodontal regeneration and destruction. Human PDL cells, derived from a primary cell culture, were transfected with simian virus 40 (SV40) T antigen-containing virus with a neomycin resistance gene. The transformed cells expressed the SV40 T antigen mRNA as assayed by reverse transcription polymerase chain reaction (RT-PCR). This cell line was also characterized for morphological changes and growth characteristics compared to primary PDL cell cultures. The transformed cells were shown to form a multilayer pattern and distinct colonies on tissue culture surfaces. However, no colony formation was found in soft agar. The transformed PDL cell line was found to have a greater rate of proliferation in 10% fetal bovine serum than primary culture, and continued to proliferate in low serum concentrations capable of producing quiescence in primary cells. Interleukin-1β (IL-1β) was shown to produce a 7-fold elevation in collagenase (MMP-1) mRNA levels, consistent with primary PDL cells. In addition, IL-1β was shown to produce a decrease in alkaline phosphatase activity in a concentration-dependent manner. The transformed cell line has been maintained for over 30 generations of cell culture. In conclusion, a stable human PDL cell line has been established to serve as a model for future in vitro investigations into periodontal pathogenic mechanisms and to evaluate therapies directed at the regeneration of periodontal ligament.