Objective Amyotrophic lateral sclerosis (ALS) is a complex disease with numerous pathological mechanisms resulting in a heterogeneous patient population. Using biomarkers for particular disease mechanisms may enrich a homogeneous subset of patients. In this study, we quantified chitotriosidase (Chit-1) and chitinase-3-like protein 1 (CHI3L1), markers of glial activation, in cerebrospinal fluid (CSF) and plasma and determined the cell types that express CHI3L1 in ALS.
Methods Immunoassays were used to quantify Chit-1, CHI3L1 and phosphorylated neurofilament heavy chain levels in longitudinal CSF and matching plasma samples from 118 patients with ALS, 17 disease controls (DCs), and 24 healthy controls (HCs). Immunostaining was performed to identify and quantify CHI3L1-positive cells in tissue sections from ALS, DCs and non-neurological DCs.
Results CSF Chit-1 exhibited increased levels in ALS as compared with DCs and HCs. CSF CHI3L1 levels were increased in ALS and DCs compared with HCs. No quantitative differences were noted in plasma for either chitinase. Patients with ALS with fast-progressing disease exhibited higher levels of CSF Chit-1 and CHI3L1 than patients with slow-progressing disease. Increased numbers of CHI3L1-positive cells were observed in postmortem ALS motor cortex as compared with controls, and these cells were identified as a subset of activated astrocytes located predominately in the white matter of the motor cortex and the spinal cord.
Conclusions CSF Chit-1 and CHI3L1 are significantly increased in ALS, and CSF Chit-1 and CHI3L1 levels correlate to the rate of disease progression. CHI3L1 is expressed by a subset of activated astrocytes predominately located in white matter.
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Contributors LV, JA and RB contributed to the conception and design of this study. LV and JA contributed to the design of the ELISAs and measurements of biomarkers. LV and TK performed the immunostaining of the postmortem tissues. TG and LP contributed cerebrospinal fluid samples to this study. LV and RB contributed to the analysis of the data, drafting of the manuscript and preparation of the figures. All authors reviewed and revised the manuscript.
Funding Funding for this study was provided by grants from the Muscular Dystrophy Association (MDA603370, RB) and Barrow Neurological Institute (RB and LV).
Competing interests RB is founder of Iron Horse Diagnostics, Inc, a company commercialising assays for ALS and other neurological diseases.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. All data relevant to the study are included in the article or uploaded as supplementary information.
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