Gingival proteomic profiling revealed differentially expressed proteins between moderate and severe periodontitis - A pilot study

Background: The molecular basis of periodontitis remains unclear with no pre-diagnostic markers or therapeutic targets. Proteomic profiling reports in gingival/periodontal pocket tissue samples is sparse. The current study is designed to compare the proteome pattern in gingival tissue between periodontally healthy, moderate and severe periodontitis participants, in order to spot differentially expressed proteins that may indicate disease severity. Objectives: To perform comparative proteomic profiling of periodontal pocket tissue, in generalised periodontitis patients, with varying degrees of periodontal disease severity using high resolution mass spectrometry. Methodology: Thirty participants were grouped into periodontally healthy, moderate periodontitis and severe periodontitis with n = 10 in each. Pocket tissue samples were collected, pooled and processed for 2D gel electrophoresis coupled with LC-MS/MS analysis with experimental triplicates. Results: The study identified 12 differentially regulated proteins in both moderate and severe periodontitis samples compared to healthy control tissues of which the majority were cytoskeleton and carrier proteins. Heat shock protein (HSP) A8, Tropomyosin1 (TPM1), Annexin3 (ANX3) and KRT9 (Type1keratin cytoskeletal9) are reported for the first time in gingival tissue samples. Significant downregulation (p <= 0.05) of cytoskeletal proteins such as KRT9, VIM (vimentin), TPM1 and TPM4, carrier/ signaling proteins such as APOA1(apolipoprotein) and FABP5 (Fatty acid binding protein) and upregulation of immune response proteins HSPB1, Caspase1, and Interleukin-18 in moderate and severe periodontitis with fold change of >= 2 was observed. HSPA8 & TPM1 uniquely were upregulated in moderate and downregulated in severe compared to healthy controls. In addition, STRING analysis revealed direct interaction of vimentin and albumin with cytoskeletal and immune response proteins. Conclusion: A definite downregulation of cytoskeletal, carrier proteins and upregulation of immune response proteins with increasing severity of periodontal disease in the present study, emphasizes the need to look into cytoskeletal/carrier proteins as potential modulators of immune response underlying pathogenesis of periodontitis.