Lipopolysaccharide’s Cytotoxicity on Human Umbilical Cord Mesenchymal Stem Cells

Effect of Lipopolysaccharide-Induced Apical Periodontitis in Diabetes Mellitus Rats on Periapical Inflammation

OBJECTIVES

 To evaluate periapical inflammation through immunohistochemical analysis of interleukin 6 (IL-6) and tumor necrosis factor α (TNF-a) expression resulting from lipopolysaccharide (LPS)-induced apical periodontitis in diabetes mellitus rats, observed at 14, 28, and 42 days.

MATERIALS AND METHODS

 Diabetes model on rats was induced by streptozotocin (STZ). Fifteen rats were injected with low-dose STZ for 5 days and waited for 5 days until the blood glucose level was stable and measured above 300 mg/dL confirmed by a digital glucometer. LPS was used to induce apical periodontitis. After performing access cavity, pulpal and root canal extirpation was done on the right mandibular first molar's root canal space of rats, under anesthesia. LPS of 1 mg/mL dose was induced in the pulpal and root canal space. Apical periodontitis was expected 14 days afterward and then, the rats were randomly allocated to three groups. The first group was terminated 14 days after induction and used as control. The second group was observed 28 days after induction, and the third group was observed 42 days after induction. IL-6 and TNF-a expression was analyzed by immunohistochemistry on macrophages in the periapical area.

STATISTICAL ANALYSIS

 Data were analyzed using one-way ANOVA and continued with the post hoc Tukey HSD test. Significance was considered if p < 0.05.

RESULTS

 LPS induced apical periodontitis in diabetes mellitus rats at control (14 days), 28 and 42 days observation showed a significant increase in the expression of IL-6 and TNF-a. There were significant differences between the control and observed groups (p < 0.05). The expression of IL-6 in the apical area was not significant at 14 and 28 days (p > 0.05) but increased significantly at 42 days (p < 0.05). The expression of TNF-a in the apical area was significantly increased after 14 days (p < 0.05) and remained stable at 28 and 42 days (p > 0.05).

CONCLUSIONS

 The periapical inflammation of LPS-induced apical periodontitis in diabetes mellitus rats increased macrophages' expression of IL-6 at 42 days and TNF-a at 28 days.

Calcium Hydroxide Increases Human Umbilical Cord Mesenchymal Stem Cells Expressions of Apoptotic Protease-Activating Factor-1, Caspase-3 and Caspase-9

Purpose

Calcium hydroxide is a gold standard dental material generally used for pulpal and periapical therapy including regenerative endodontic procedures because of its positive properties. However, evaluation about this material on stem cells is limited. Human umbilical cord mesenchymal stem cells (HUCMSCs) are potential to be used in regenerative therapy. Regenerative therapy needs a sustainable cell supply to maintain its regenerative capacity. The aim of this study was to ascertain the apoptosis result of calcium hydroxide on HUCMSCs through the expression of apoptotic protease-activating factor-1 (APAF-1), caspase-3, and caspase-9.

Materials and Methods

This study used a thawed frozen stock of passage 5 HUCMSCs, grown in minimum essential medium (MEM) alpha containing calcium hydroxide at concentration of 0.1 microgram/mL for 1, 3 and 7 days. Polyclonal antibody with fluorescence isothiocyanate (FITC) label was used to evaluate the expressions. APAF-1, caspase-3, and caspase-9 expressions were recorded and compared on every observation day using fluorescence microscope. Analysis of variance was performed to analyze the significance among the results of treatment groups. The results were concluded significant if p<0.05.

Results

The addition of calcium hydroxide in MEM alpha medium increases HUCMSCs expression of APAF-1, caspase-3 and caspase-9 significantly, compared to the control group without calcium hydroxide (p<0.05) in all the times. Day 1 showed the lowest increase followed by higher expressions on day 3 and day 7.

Conclusion

HUCMSCs express increased APAF-1, caspase-3 and caspase-9 after in-vitro calcium hydroxide exposure. This should be considered when using calcium hydroxide on HUCMSCs for regenerative procedures with regard to other positive properties.