Migration inhibitory factor related protein-8 (MRP-8) is an autocrine chemotactic factor for periodontal ligament cells

Previous studies have suggested that human periodontal ligament (PDL) cells secrete a chemotactic factor which stimulates motility in an autocrine man ner. Here we report the partial amino acid sequence of a purified factor wh ich shows 100% homology with human migration inhibitory factor related prot ein-8 (MRP-8). In addition, reverse-transcription polymerase chain-reaction (RT-PCR) analysis revealed that mRNA encoding MRP-8 was expressed in cultu red human PDL cells. To confirm that MRP-8 is chemotactic for PDL cells, we synthesized 25 mer peptides overlapped by 5 amino acids covering the entir e MRP-8 protein and tested them for their chemotactic activities. The data indicated that amino acid residues 21-45 showed chemotactic activity for cu ltured human PDL cells. The maximum chemotactic response was observed at th e concentration of 10(-15) mol/mL for human PDL cells. The chemotactic acti vity was estimated to be approximately 1000-fold higher than that of platel et-derived growth factor (PDGF), insulin-like growth factors-I and -II (IGF -I, -II), and epidermal growth factor (EGF) when compared on a molar basis. Since MRP-8 is reported to be produced mainly by neutrophils and monocytes , the result of the current study may suggest another important role of MRP -8 in human PDL cells.