David C Schorling1, Heike Kölbel2, Andreas Hentschel3, Astrid Pechmann1, Nancy Meyer2, Brunhilde Wirth4, Roman Rombo4, Albert Sickmann3, Janbernd Kirschner1,5, Ulrike Schara-Schmidt2, Hanns Lochmüller1,6,7, Andreas Roos2,3,8. 1. Department of Neuropediatrics and Muscle Disorders, Medical Center, University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany. 2. Department of Pediatric Neurology, Developmental Neurology, and Social Pediatrics, Center for Neuromuscular Disorders in Children and Adolescents, University of Duisburg-Essen, Essen, Germany. 3. Leibniz Institute of Analytical Sciences, ISAS, Dortmund, Germany. 4. Center for Molecular Medicine Cologne, Institute of Human Genetics, Institute of Genetics, and Center for Rare Disorders, University of Cologne, Cologne, Germany. 5. Department of Neuropediatrics, Faculty of Medicine, University Hospital Bonn, Bonn, Germany. 6. Division of Neurology, Department of Medicine, Children's Hospital of Eastern Ontario Research Institute, Ottawa Hospital and Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada. 7. National Center for Genomic Analysis, Center for Genomic Regulation, Barcelona Institute of Science and Technology, Barcelona, Spain. 8. Department of Neurology, Heimer Institute for Muscle Research, University Hospital Bergmannsheil, Ruhr University Bochum, Bochum, Germany.
Abstract
BACKGROUND AND PURPOSE: The therapeutic landscape of spinal muscular atrophy (SMA) has changed dramatically during the past 4 years, but treatment responses differ remarkably between individuals, and therapeutic decision-making remains challenging, underlining the persistent need for validated biomarkers. METHODS: We applied untargeted proteomic analyses to determine biomarkers in cerebrospinal fluid (CSF) samples of SMA patients under treatment with nusinersen. Identified candidate proteins were validated in CSF samples of SMA patients by Western blot and enzyme-linked immunosorbent assay. Furthermore, levels of peripheral neurofilament heavy and light chain were determined. RESULTS: Untargeted proteomic analysis of CSF samples of three SMA type 1 patients revealed the lysosomal protease cathepsin D as a candidate biomarker. Subsequent validation analysis in a larger cohort of 31 pediatric SMA patients (type 1, n = 12; type 2, n = 9; type 3, n = 6; presymptomatically treated, n = 4; age = 0-16 years) revealed a significant decline of cathepsin D levels in SMA patients aged ≥2 months at the start of treatment. Although evident in all older age categories, this decline was only significant in the group of patients who showed a positive motor response. Moreover, downregulation of cathepsin D was evident in muscle biopsies of SMA patients. CONCLUSIONS: We identified a decline of cathepsin D levels in CSF samples of SMA patients under nusinersen treatment that was more pronounced in the group of "treatment responders" than in "nonresponders." We believe that our results indicate a suitability of cathepsin D levels as a possible biomarker in SMA also in older patients, in combination with analysis of peripheral neurofilament light chain in adolescents or alone in adult patients.
BACKGROUND AND PURPOSE: The therapeutic landscape of spinal muscular atrophy (SMA) has changed dramatically during the past 4 years, but treatment responses differ remarkably between individuals, and therapeutic decision-making remains challenging, underlining the persistent need for validated biomarkers. METHODS: We applied untargeted proteomic analyses to determine biomarkers in cerebrospinal fluid (CSF) samples of SMA patients under treatment with nusinersen. Identified candidate proteins were validated in CSF samples of SMA patients by Western blot and enzyme-linked immunosorbent assay. Furthermore, levels of peripheral neurofilament heavy and light chain were determined. RESULTS: Untargeted proteomic analysis of CSF samples of three SMA type 1 patients revealed the lysosomal protease cathepsin D as a candidate biomarker. Subsequent validation analysis in a larger cohort of 31 pediatric SMA patients (type 1, n = 12; type 2, n = 9; type 3, n = 6; presymptomatically treated, n = 4; age = 0-16 years) revealed a significant decline of cathepsin D levels in SMA patients aged ≥2 months at the start of treatment. Although evident in all older age categories, this decline was only significant in the group of patients who showed a positive motor response. Moreover, downregulation of cathepsin D was evident in muscle biopsies of SMA patients. CONCLUSIONS: We identified a decline of cathepsin D levels in CSF samples of SMA patients under nusinersen treatment that was more pronounced in the group of "treatment responders" than in "nonresponders." We believe that our results indicate a suitability of cathepsin D levels as a possible biomarker in SMA also in older patients, in combination with analysis of peripheral neurofilament light chain in adolescents or alone in adult patients.