Effect of lipopolysaccharide on cell proliferation and vascular endothelial growth factor secretion of periodontal ligament stem cells

Abstract

Purpose: Periodontal ligament stem cells (PDLSCs) have considerable potential for use as a means of achieving periodontal regeneration due to their noteworthy proliferative properties and secretory functions. In particular, PDLSCs secrete vascular endothelial growth factor (VEGF) which enhances angiogenesis and osteogenesis. The resulting repair and development of blood vessels and hard tissues which would occur in the presence of these cells could be central to an effective periodontal regeneration procedure.The bacterial biofilm of tooth surface related to the periodontium might provide either an inhibition or a stimulus to different factors involved in a regenerative process. Cell culture experiments have been investigated in vitro by adding lipopolysaccharide (LPS) to the culture medium but the effect of various concentration of LPS in these circumstances has not been investigated. Therefore, this study aimed to investigate the effect of LPS concentrations on proliferation of PDLSCs in vitro and on their secretion of VEGF.

Materials and methods: PDLSCs were treated with 0, 5, 10 and 20 µg/mL of Escherichia coli LPS. At 48 and 96 h, total cell numbers of control and LPS treated PDLSCs were counted by haemocytometer under a microscope. The VEGF concentration in the conditioned media of the PDLSCs was measured by ELISA.

Results: Rate of cell proliferation of PDLSCs decreased significantly in all LPS treated groups at both 48 h and 96 h except for the group treated with 5 µg/mL of LPS at 48 h. At both 48 and 96 h, VEGF secretion from PDLSCs was reduced significantly at all three LPS concentrations. There was no statistically significant difference in cell proliferation and the amount of VEGF secretion of PDLSCs among the groups treated with different LPS concentrations. No statistically significant change was found in cell proliferation of LPS treated PDLSCs over time, whereas VEGF secretion of PDLSCs was found to have increased significantly with time despite the LPS treatment.

Conclusions: LPS reduced cell proliferation and VEGF secretion of PDLSCs, suggesting that periodontal pathogens might reduce the capability of PDLSCs in periodontal regeneration. Yet, LPS treated PDLSCs remained viable and VEGF secretion increased significantly over time. Further research is needed to study the potential use of PDLSCs in periodontal regeneration and the relationship of biofilm LPS accumulations.

Keywords: Lipopolysaccharides; Periodontal ligament; Stem cells; Vascular endothelial growth factor.

Fig. 1

Microscopic pictures of PDLSCs treated with different LPS concentration at 48 and 96 h. Magnification ×10. All groups of LPS treated PDLSCs retained the capacity to form fibroblast spindle-shape. (a, e) PDLSCs without LPS treatment at 48 and 96 h. (b, f) PDLSCs treated with 5 µg/mL of LPS at 48 and 96 h. (c, g) PDLSCs treated with 10 µg/mL of LPS at 48 and 96 h. (d, h) PDLSCs treated with 20 µg/mL of LPS at 48 and 96 h.