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Objective To investigate the role of ceramide in radiation induced bystander effect (RIBE) in vivo by irradiating Caenorhabditis elegans with proton microbeam.Methods The posterior pharynx of wide-type N2 and genetically mutated L4-staged worms was irradiated with 2 000 particles,then germ cell apoptosis and gene expression were analyzed.Results Point-fixed radiation to posterior pharynx of N2 worms significantly increased the number of apoptotic germ cells (t =9.007,P＜0.05),but not in the worms with deletion mutants of ceramide synthase (CerS) genes (hyl-1 and lagr-1) (P＞0.05).Realtime quantitative PCR assay indicated that in both N2 and lagr-1 (gk327);hyl-1 (ok976) worms,the genes of egl-1 and ced-13 in core apoptosis pathway were up-regulated after radiation to posterior pharynx,without statistical significance between these two strains (P＞0.05).The gene expression levels of hyl-1 and lagr-1 were increased in both N2 and hus-1 (op241) worms after radiation with no statistical significant difference between two strains (P＞0.05).Furthermore,radiation-induced germ cell apoptosis was increased in abl-1 (ok171) worms (t=13.241,P＜0.05),rather than in lagr-1(gk327);hyl-1(ok976);abl-1(ok171) worms (t=13.462,P＜0.05).Conclusions Ceramide is required for RIBE on germ cell apoptosis in C.elegans,and it might play function together with egl-1 and ced-13 in core apoptosis pathway and HUS-1 in DNA damage response pathway.But ceramide had antagonistic relationship with anti-apoptotic protein abl-1 in germ cell apoptosis.
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BACKGROUND:Periodontal ligament stem cels are one of the ideal seed cels in periodontal tissue regeneration. Sources, biological characteristics and influential factors of periodontal ligament stem cels have been an issue of concern. OBJECTIVE:To review the biological characteristics and functional factors of periodontal ligament stem cels as wel as relevant research status and progress in regenerative medicine, and to discuss the relevant application prospect and existing problems, thereby providing theoretical and experimental basis. METHODS:PubMed and Wanfang databases were searched by the first author for articles related to differentiation and proliferation of periodontal ligament stem cels published from 2002 to 2015. The key words were “periodontal ligament stem cel, periodontal tissue, proliferation, differentiation” in English and Chinese, respectively. Finaly, 47 articles were included in result analysis. RESULTS AND CONCLUSION:Periodontal ligament stem cels have the ability of differentiating into fibroblasts, adipocytes, chondrocytes and cementum. Cel growth factors play an important role in the proliferation and differentiation of periodontal ligament stem cels. Fibroblast growth factor, vascular endothelial growth factor and insulin-like growth factor can promote the proliferation of periodontal ligament stem cels. Application of stem cel biofilm as a carrier material can effectively guide periodontal tissue regeneration. Isolation, culture and influential factors of periodontal ligament stem cels should be further improved. Combined application of stem cels, biofilms and growth factors is expected to achieve the desired periodontal tissue regeneration, which is the focus of future research.