Lipopolysaccharide differentially affects osteogenesis of healthy and inflammatory periodontium

Abstract

Objectives: The aim of this study was to compare the proliferation and osteogenic capacities of human periodontal ligament stem cells (PDLSC) from healthy and inflammatory periodontal tissues, and to investigate the influence of P. gingivalis lipopolysaccharide (LPS) on them. Methods: Human PDL stem cells (PDLSC) were isolated from root-attached healthy (PDLSC-h), and inflammatory (PDLSC-i) periodontal tissue from healthy orthodontic (n=4), and ongoing periodontitis (n=4) patients. The PDLSCs were characterized by flow cytometry, and then challenged by P. gingivalis LPS (0.1, 1, 10 μg/ml). Their proliferative potentials and osteogenic differentiation capacities were evaluated and compared. Results: Both groups of PDLSCs exhibited similar mesenchymal stem cell surface markers. The proliferative rates of PDLSC-h were higher than PDLSC-i, both of which were not affected by LPS challenge. Upon 7 days of LPS challenge, there were increasing trends in expression levels of osteogenic markers (ALP, COL1, RUNX2 and OCN): the PDLSC-h peaked at 1 μg/ml LPS challenge, while PDLSC-i peaked at 0.1 μg/ml. However, after 14 days of LPS challenge, decreased expressions of osteogenic markers were detected upon 10 μg/ml LPS challenge in both groups of PDLSCs, with no significant difference among 0, 0.1 and 1 μg/ml LPS challenge. Generally, the osteogenic capacity of PDLSC-i was lower than PDLSC-h, with less expression of osteogenic markers and decreased Alizarin Red S staining. Conclusions: The osteogenic differentiation potential was lower in inflammatory periodontal tissue, and PDLSCs from healthy and periodontitis donors respond to LPS in different manners.