, Volume 328, Issue 3, pp 537-548
Date: 06 Mar 2007

Elevated expression of genes assigned to NF-κB and apoptotic pathways in human periodontal ligament fibroblasts following mechanical stretch

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There is growing evidence that apoptosis involves the nuclear transcription factor NF-κB in conjunction with related genes. However, in the context of mechanical orthodontic forces, force-sensing target genes assigned to pathways of NF-κB and apoptosis have not been fully characterised. To contribute to the identification of putative target genes, we used cDNA arrays specific for NF-κB and apoptotic pathways and analysed elevated gene expression in primary human periodontal ligament fibroblasts (PDL-F) after a 6 h application of mechanical force. Among several identified genes (including several caspases), interleukin-1β (IL-1β) and NF-κB displayed significantly higher expression on the NF-κB array, whereas higher expression was obtained for BCL2-antagonist of cell death (BAD), member 6 of the TNF-receptor superfamily (FAS) and CASP2 and RIPK1 domain-containing adaptor with death domain (CRADD) on the apoptosis array. Based on a defined cut-off level of a more than 1.5-fold higher expression, this significance in elevated gene expression was corroborated by reverse transcription/polymerase chain reaction (RT-PCR). Here, semi-quantitative (sq) PCR revealed a more pronounced elevation of mRNA gene expression in PDL-F after 6 h of stretch, when compared with 12 h. Moreover, the elevation after 6 h as observed by sq-PCR was convergent with quantitative PCR (q-PCR). q-PCR yielded levels of 5.8-fold higher relative gene expression for IL-1β and 1.7-fold for NF-κB, whereas that computed for BAD indicated a 5.2-fold, for CRADD a 2.1-fold and for FAS a 2.0-fold higher expression. The data obtained from the expression analysis thus indicate a stretch-induced transcriptional elevation of genes assigned to the NF-κB and apoptotic pathways. This elevation may render them target candidates for being addressed by mechanical orthodontic forces.

Nina Ritter and Eva Mussig contributed equally to the manuscript.
This work was supported by grants from the German Orthodontic Society/DGKFO to Eva Mussig (Science fund project no. 32, 2005) and from the DFG to Pascal Tomakidi (P.T. TO 195/6-1).
This article is dedicated to Professor Dr. Gerda Komposch due to her leadership of the Orthodontics Department for 28 years.