Roles of Gingipains in Periodontal Bone Loss

Gingipains are cysteine proteases produced by Porphyromonas gingivalis, one of the major pathogens of periodontitis. They are classified into lysine-specific gingipain (Kgp) and arginine-specific gingipains (Rgps) by the specificity of the proteolytic cutting sites. Gingipains are known to play a major role in the progression of periodontitis by inducing inflammation and tissue destruction in the periodontium, including alveolar bone loss by osteoclasts ; however, the roles of gingipains in osteoclastic bone resorption have not been elucidated yet. Recently, we reported that Kgp but not Rgps and active vitamin D3 or microbial components such as lipopolysaccharide (LPS) synergistically induced osteoclast formation and activation in a setting where both osteoblasts and osteoclast precursor cells co-exist. While LPS has been regarded as one of the major factors for osteoclastogenesis and alveolar bone loss in periodontitis, our findings revealed that not only LPS but also Kgp plays a pivotal role in alveolar bone loss in periodontitis.