Role of PIN1 on in vivo periodontal tissue and in vitro cells

Background: Although expression of peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (PIN1) was reported in bone tissue, the precise role of PIN1 in periodontal tissue and cells remain unclear. Material & Methods: To elucidate the roles of PIN1 in periodontal tissue, its expression in periodontal tissue and cells, and effects on in vitro 4 osteoblast differentiation and the underlying signaling mechanisms were evaluated. Results: PIN1 was expressed in mouse periodontal tissues including periodontal ligament cells (PDLCs), cementoblasts and osteoblasts at the developing root formation stage (postnatal, PN14) and functional stage of tooth (PN28). Treatment of PIN1 inhibitor juglone, and gene silencing by RNA interference promoted osteoblast differentiation in PDLCs and cementoblasts, whereas the overexpression of PIN1 inhibited. Moreover, osteogenic medium-induced activation of AMPK, mTOR, Akt, ERK, p38 and NF-jB pathways were enhanced by PIN1 siRNA, but attenuated by PIN1 overexpression. Runx2 expressions were induced by PIN1 siRNA, but downregulated by PIN1 overexpression. Conclusion: In summary, this study is the first to demonstrate that PIN1 is expressed in developing periodontal tissue, and in vitro PDLCs and cementoblasts. PIN1 inhibition stimulates osteoblast differentiation, and thus may play an important role in periodontal regeneration.