Supervisors info:
Μιχαήλ Κουτσιλιέρης, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Αναστάσιος Φιλίππου, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ιωάννης Καρούσης, Αναπληρωτής Καθηγητής, Οδοντιατρική Σχολή, ΕΚΠΑ
Summary:
The substantial increase of patients bearing implants, the past two decades, brings the clinician before the prevention and treatment of peri-implant pathology, as well as the long-term maintenance of the therapeutic outcome. The past years, the research interest has been turned towards free titanium particles, that are the product of corrosive events or the mechanical debridement of the implant surface, during the surgical therapy of periimplantitis or during the maintenance care program with several types of instruments. The question is whether these particles are capable of inducing or worsen an already established inflammatory reaction that will certainly not improve the condition, despite the good will of the clinician.
Aim
The aim of the present study is to investigate the effect of titanium particles, on the same or maybe greater degree than P. gingivalis lipopolysaccharide, on the gene expression of two major pro-inflammatory cytokines, interleukin-6 and interleukin-8, as well as gene expression of collagen type I of human gingival fibroblasts. The possibility of a synergistical activity between titanium particles and LPS is also examined.
Materials and Methods
Human gingival fibroblasts were cultured on sand blasted and acid-etched (SLA) titanium and TCP surfaces for 7 days. 24 hours after the culture of cells on both surfaces, the cells were treated with either LPS, particles or LPS and particles combined. At 24, 48 and 72 hours after treatment, MTT assay was performed to assess cell proliferation. FDA/PI staining has also been performed for the same time periods, in order to evaluate cell viability/apoptosis. At 5 and 7 days after the treatment, cell RNA was isolated and PCR was performed to assess gene expressions of IL-6, IL-8 and COL1A1. SEM microscopy was also performed five and seven days after the treatment for all groups on SLA surfaces.
Results
hGFs have shown a statistically significant difference in proliferation rates on SLA surfaces, compared to TCP, in favor of the latter. However, all groups, independently of the treatment kind, had a significant increase of their population between the time periods of examination. As far as the expression of interleukin levels is concerned, the combination of LPS and particles significantly increases the levels of interleukin-8 expression, compared to LPS or particles alone. On SLA surfaces, treatment with LPS and particles, induced a significant increase of interleukin-6 and collagen. FDA/PI microscopy has shown increased cell apoptosis for all treatment groups, as well as differences on cell morphology. SEM microscopy has revealed stressed cells with zones of no cells and a disrupted adhesion on SLA surfaces.
Conclusions
Rough titanium surfaces significantly affect the proliferation and morphology of human gingival fibroblasts, which contact such surfaces after bone resorption and pocket formation induced by inflammation. Moreover, the combination of titanium particles and LPS increase, in a statistically significant manner, the expression of IL-6, IL-8 and collagen. Taking into account the immunoregulatory role of fibroblasts in the connective tissue of the peri-implant mucosa, it appears that particles arouse a similar cellular reaction as the bacterial endotoxin, while synergistically intensifying this reaction. Finally, since these cells are also responsible for collagen synthesis and extracellular matrix production, the increase in collagen expression, indicates an increased activity of cells towards the production of reactive tissue.
Keywords:
Titanium implants, Titanium corrosion, Experimental in vitro study, Peri-implantitis, Human gingival fibroblasts
