New Sjogren's study: Epigenetically quantified immune cells in salivary glands of Sjögren’s syndrome patients

Sofie L.M. Blokland, Fréderique M. van Vliet-Moret, Maarten R. Hillen, Aridaman Pandit, Roel Goldschmeding, Aike A. Kruize, Gerben Bouma, André van Maurik, Sven Olek, Ulrich Hoffmueller, Joel A.G. van Roon, Timothy R.D.J. Radstake, Epigenetically quantified immune cells in salivary glands of Sjögren’s syndrome patients: a novel tool that detects robust correlations of T follicular helper cells with immunopathology, Rheumatology, July 2019  https://doi.org/10.1093/rheumatology/kez268

My Understanding of this Study

In this study, researchers tested epigenetic cell counting (ECC).

ECC is a way of measuring inflammation that may help in diagnosing people with Sjogren's syndrome (SS). It could also help with monitoring symptoms of the disease.

The main benefits of epigenetic cell counting are that:

• samples can be stored for longer than other biological molecules.
• smaller samples are needed.
• a large amount of cell specific biomarkers can be identified
  
  The researchers did ECC on salivary biopsy samples of 57 people with dry mouth including those with primary Sjögren’s syndrome, secondary Sjögren’s syndrome, and some with undiagnosed SS.
  
  Using computer algorithms, researchers created patient groups based on the information collected from these salivary cells. This clearly showed the identified types and subsets, some of which were:
• people with severe disease who had high amounts of T follicular helper cells
• undiagnosed SS samples showing fewer B- and T-cells
• patients with SS who had many kindsof cells
  
  The study was small and further larger studies are needed to confirm these results and define the best markers that ECC can measure.
  
  The researchers suggested that ECC could be used, on its own or in combination with other methods, to “aid in diagnostics, prognostics and monitoring of therapy responses in clinical trials in the future.”  

Abstract of Study

Objective

To investigate whether epigenetic cell counting represents a novel method to quantify immune cells in salivary glands of patients with different forms of Sjögren’s and sicca syndrome and to capture immunopathology and potentially aid in diagnosis.

Methods

DNA from frozen salivary gland tissue sections of sicca patients was used for bisulphite conversion of demethylated DNA cytosine residues, followed by cell-specific quantitative PCR to calculate cell percentages in relation to total tissue cell numbers as quantified by housekeeping gene demethylation. The percentages of epigenetically quantified cells were correlated to RNA expression of matched salivary gland tissue and histological and clinical parameters.

Results

The percentages of epigenetically quantified CD3, CD4, CD8, T follicular helper (Tfh) cells, FoxP3⁺ regulatory T cells and B cells were significantly increased in the salivary glands of patients with SS. Unsupervised clustering using these percentages identified patient subsets with an increased lymphocytic focus score and local B cell hyperactivity and classifies patients different from conventional classification criteria. In particular, Tfh cells were shown to strongly correlate with the expression of CXCL13, lymphocytic focus scores, local B cell hyperactivity and anti-SSA positivity.

Conclusion

Epigenetic cell counting is a promising novel tool to objectively and easily quantify immune cells in the labial salivary gland of sicca patients, with a relatively small amount of tissue needed. In view of the potential of this technique to include a huge number of (cell-specific) biomarkers, this opens up new standardized ways of salivary gland analysis with high relevance for patient classification, understanding of immunopathology and monitoring of drug responses in clinical trials.