EFFECT OF LIPOPOLYSACCHARIDE ON PROLIFERATION AND OSTEOGENIC DIFFERENTIATION OF STEM CELLS FROM APICAL PAPILLA WITH DIFFERENT AMOUNT OF CD24 EXPRESSING CELLS

Abstract

Stem cells from apical papilla (SCAPs) were believed the source of regenerative endodontic procedure (REP) that is performed in infected immature tooth. However, the new hard tissues were reported to be bone or cementum-like structure. It was possible that root canal infection might alter SCAPs to generate bone or cementum-like structure rather than dentin. This might due to the effects of lipopolysaccharide (LPS) in infected root canal. In addition, the percentages of CD24 expressing SCAPs varied among the studies. CD24 involved many cellular activities such as cell proliferation, differentiation and self-renewal of stem cells. Therefore, CD24 might affect to REP, as well. In this thesis, the variation of CD24 expression was confirmed. To facilitate the investigation of amount of CD24, SCAPs were classified into two groups, High and Low-CD24. The mesenchymal stem cell markers and cell proliferation were not different between two groups. However, High-CD24 demonstrated lower self-renewal than Low-CD24 but higher multi-differentiation capacity than Low-CD24. High-CD24 associated with early root formation while Low-CD24 related to later stage of root formation. After exposure with 0.001-5µg/ml of LPS, cell proliferation and migration of all experimental groups were not different from their control groups of both High and Low-CD24. However, High-CD24 significantly increased mineralization activity when exposed to 1 and 5 µg/ml of LPS. Moreover, bone sialopreotein (BSP) gene expression that extensively expressed in bone and cementum, significantly increased when exposed to 1 and 5 µg/ml of LPS. Low-CD24 did not alter mineralization activity when compared with non-exposure LPS group. However, the BSP gene expression increased only when compared with 5 µg/ml exposure. Dentin sialophosphoprotein (DSPP) gene expression was not different between LPS pre-exposure and control group of both High and Low-CD24. The results from this study may explain why the bone or cementum-like structure was formed by SCAPs after performing REP.