Putative blood biomarkers of Reversible Cerebral Vasoconstriction Syndrome

Background/Purpose

The pathophysiology and molecular mechanisms of Reversible Cerebral Vasoconstriction Syndrome (RCVS) are unknown. Objective of the study was to identify putative biomarker proteins for RCVS.

Methods

Patients were recruited from our institution’s prospective RCVS registry. Plasma samples were collected from 6 patients with RCVS during the acute cerebral vasoconstrictive phase, 2 patients at 6-month follow-up after resolution of vasoconstriction, and 4 patients with CNS vasculitis.

Plasma samples were immune-depleted for the most abundant plasma proteins, precipitated, and then digested overnight with trypsin and analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). These LC-MS/MS experiments were carried out on a high resolution Orbitrap-Elite FT-MS system that allows the relative quantity of the proteins in these samples to be determined by a label free quantitative method. The quantitation is performed by searching the data with the programs Mascot and Sequest.  These search results were then uploaded into the program Scaffold. The quantitation was performed by comparing the normalized spectral counts (SC) for the samples. The data was filtered based on several parameters including two matching peptides, a FDR of 1.0%, a protein threshold of 95%, and identified in at least 3 of the samples.  The relative quantity of these proteins was determined by using the spectral counting method that has been described previously   In order for a protein to be considered as a putative biomarker, the relative abundance needs to be at least two fold different with the T-test derived p-value less than 0.05

Results
A total of 228 proteins were identified. Three, 5 and 4 proteins were found to be of higher abundance in a) follow-up samples of RCVS compared to baseline, b) CNS vasculitis samples compared to baseline RCVS, and c) baseline RCVS samples compared to CNS vasculitis respectively (Table 1)

Conclusion

This is a preliminary study looking at proteomic analysis of RCVS plasma samples. Results of this study show proteins that might be potential biomarkers for RCVS and   which could help differentiate RCVS from its mimic CNS vasculitis. Further studies with larger number of patients are needed to assess reproducibility.  The function and the pathways of these differentially expressed proteins should be further explored.