Role of HMGB1 in proliferation and migration of human gingival and periodontal ligament fibroblasts

High mobility group box 1 (HMGB1) was originally defined as a nuclear protein. However, later studies showed that HMGB1 was released from damaged cells into the extracellular milieu and functioned as a danger signaling molecule. HMGB1 has also been shown to exert proliferative and chemoattractant effects on many cell types. In this study, we investigated the in vitro effect of human recombinant HMGB1 on the proliferation and migration of human gingival fibroblasts (HGF) and human periodontal ligament fibroblasts (HPDLF). For the proliferation assay, HGF and HPDLF were cultured in the presence of 5, 10, and 50 ng/mL HMGB1. After a period of 6 days, cell proliferation was determined by MTT assay. The migration assay was performed by culturing the two cell types in Transwells with HMGB1 in the lower chamber as a chemoattractant. Cell migration during 16 h was determined by crystal violet staining of the cells that migrated across the membrane. The results showed that HMGB1, at 50 ng/mL, was able to significantly induce proliferation of HGF by up to 171.4 +/- 17.1%. No such proliferation induction was seen for HPDLF. In the migration assay, however, 100 ng/mL HMGB1 induced migration of both cell types. The counts of cells that migrated across the membrane, as compared with the control, were increased to 273 +/- 24.1% and 410.3 +/- 158% for HGF and HPDLF, respectively. Since proliferation and migration are basic abilities of cells required for proper tissue repair, these data suggest that HMGB1 plays an important role in these functions of periodontal cells.