Background: The field of biomarkers study in DMD has seen potential candidates for diagnosis, prognosis, and use as outcome measures in clinical trials. Gelsolin is a key protein involved in the regulation of actin dynamics, and it has been reported by us and others to decrease in DMD relative to healthy controls. To gain an insight into the possible role of gelsolin in DMD, we performed analysis using longitudinal sera samples collected from DMD naïve patients to see if there is any correlation with disease progression. Also, we carried out extensive studies on the tissue samples collected from DMD patients and mdx mice models for DMD. Lastly, we tested the association of the protein with disease severity by comparing samples from age-matched DMD and BMD patients.
Objective: To define gelsolin as a reliable biomarker for disease pathogenesis and progression in DMD patients.
Approach: Sera samples from DMD patients and healthy controls (n=7) were analyzed with ELISA and mass spectrometry using stable-isotope spiking strategy. Next, we examined the trajectory of gelsolin in longitudinal sera samples collected from DMD naïve patients using ELISA and targeted mass spectrometry with stable-isotope spiking strategy. Further, ELISA and western blot were used to determine levels of gelsolin in serum samples collected from DMD patients, BMD patients, and age-matched healthy controls (n= 12) and tissue samples derived from DMD patients and mdx mice respectively.
Results: Previous studies have shown gelsolin decreasing in DMD versus control, we were able to confirm this with multiple approaches. Gelsolin was found to be decreased by 2 fold in DMD relative to controls. Using age-matched DMD, BMD and control subjects (age: 6-30 years), we established that gelsolin is clinically associated with disease severity (p-value < 0.05). Also, we detected a decline in the level of the protein as the disease progresses in our Somascan data, while the ELISA and mass spec results show the opposite. We hypothesize this discrepancy between Somascan data and the two other orthogonal assays is caused by the actin bound to gelsolin that hindered the epitope detected by the aptamer in Somascan but not in ELISA or mass spectrometry assays. Further analysis of muscle samples from DMD patients and mdx mouse models showed an elevated level of gelsolin, which is the exact opposite of what was seen in the serum. This suggests that it may play a role in muscle pathogenesis in dystrophic muscles.
Conclusion: Gelsolin may be a useful biomarker to measure disease severity and progression in DMD. Also, this protein may be involved in activities related to DMD pathogenesis.