Effects of growth/differentiation factor-5 on human periodontal ligament cells

Growth/differentiation factor-5 (GDF-5), a member of the transforming growth factor-beta superfamily, shows a close structural relationship to bone morphogenetic proteins and plays crucial roles in skeletal, tendon, and ligament morphogenesis. The mRNA encoding GDF-5 is also expressed during odontogenesis, especially in dental follicle tissue. While this suggests that GDF-5 participates in the formation of alveolar bone and the periodontal ligament, cementum, and dental root, the physiologic role of GDF-5 in these tissues in adulthood remains unclear. We therefore investigated GDF-5 effects upon cultures of human periodontal ligament (HPDL) cells.

HPDL cells were obtained from healthy periodontal ligaments of individuals. Tetrazolium reduction assay was carried out for cell proliferation assay. Alkaline phosphatase (ALP) activity was estimated by measuring light absorbance at 405 nm. Reverse transcription-polymerase chain reaction (RT-PCR) and northern analysis were performed for gene expression in cultured HPDL cells. Sulfated glycosaminoglycan (sGAG) synthesis was evaluated by histochemical staining and a quantitative dye-binding method.

Expression of GDF-5 and its receptor was demonstrated in HPDL cells by RT-PCR. ALP activity in HPDL cells was significantly decreased by addition of rhGDF-5 at 10-1000 ng/ml (p < 0.05). Although northern analysis showed little change in gene expression for collagen alpha2(I) in rhGDF-5-stimulated HPDL cells, rhGDF-5 dose-dependently enhanced cell proliferation. This proliferative effect persisted for 16 d. Alcian blue staining and dye-binding assays indicated that sGAG synthesis was enhanced by rhGDF-5.

rhGDF-5 may provide an environment fostering periodontal healing or regeneration by affecting extracellular matrix metabolism.