A new albumin-depletion strategy improves proteomic research of gingival crevicular fluid from periodontitis patients

Abstract

Objectives: Gingival crevicular fluid (GCF), the inflammatory infiltrate within the crevicular sulcus, is of great importance for diverse processes in the oral cavity and has a high impact in oral sciences. It is assumed to serve as a source of biomarkers for systemic or periodontal diseases and mediators of orthodontic tooth movement. In order to characterize the protein content of the GCF in an unbiased and complete approach, we employed mass spectrometry (MS), which allows not only the identification, but also the quantification of these proteins. In samples obtained from patients suffering from periodontitis, this method is often limited due to the presence of highly abundant serum albumin deriving from serum. The aim of this investigation was to employ a protein precipitation procedure for the efficient depletion of serum albumin from GCF samples.

Materials and methods: GFC samples collected from five adult periodontitis patients were fractionated by trichloroacetic acid/acetone precipitation and the resulting soluble and pelleted fractions were analyzed by SDS-PAGE and high-resolution mass spectrometry.

Results: Trichloroacetic acid/acetone precipitation was successfully employed as a protein precipitation procedure for the efficient depletion of serum albumin from GCF samples. Careful analysis revealed that the precipitation step reduced the serum albumin content efficiently, and increased subsequent protein identifications by 32%. Three hundred seventeen proteins could only be identified with this new approach.

Conclusion: The increased coverage of the GCF proteome will help improve our understanding of molecular mechanisms in the periodontium during pathogenesis of periodontitis.

Clinical relevance: Our new albumin depletion strategy combined with high-resolution mass spectrometry can be used to effectively monitor the molecular signals of the periodontium.

Keywords: Gingival crevicular fluid; Mass spectrometry; Orthodontic tooth movement; Periodontitis; Serum albumin.