Advances in mucopolysaccharidosis research: the impact of mass spectrometry-based approaches

Glycosaminoglycans (GAGs) are linear polysaccharide chains that are usually linked to proteins to create proteoglycans and play an essential role in the extracellular matrix (ECM). Mucopolysaccharidoses (MPS) are a group of rare disorders that arise due to impairment in the breakdown of glycosaminoglycans (GAGs). Key technological advances in mass spectrometry (MS) have had a significant impact on the study and diagnosis of MPS, as well as its clinical management. This review summarizes the current applications of mass spectrometry-based approaches in MPS, emphasizing its role in the understanding of pathophysiological disease mechanisms, and towards improved patient care. Mass spectrometry-based proteomics and metabolomics have identified novel biomarkers and metabolic perturbations related to the pathophysiology of MPS. In addition, mass spectrometry-based glycomics analyses have been employed for the structural characterization of GAGs to reveal their heterogeneity. The sensitivity and specificity of liquid chromatography tandem mass spectrometry (LC-MS/MS) as compared to conventional methods for the quantitation of GAGs have revolutionized diagnostics. High-resolution mass spectrometers such as Orbitrap and Fourier transform ion cyclotron resonance, permit more accurate GAG characterization. Mass spectrometry has also proven valuable in monitoring patients undergoing treatment, thereby allowing the sensitive monitoring of the therapeutic efficacy of both enzyme replacement and gene therapies. Mass spectrometry has enabled improved newborn screening and multiplex assays for screening multiple MPS types. Despite the important contributions of mass spectrometry to enhance MPS research and clinical management, there still remain challenges related to long and complex sample preparation processes, lack of standardization and lack of accessibility in routine clinical settings. We envision that future initiatives will incorporate multiple omics technologies to obtain a more holistic view of the pathophysiology of MPS. Fortunately, mass spectrometry technologies and methods continue to evolve rapidly, promising further advancements in MPS diagnosis, monitoring of patients on therapy and research that should ultimately lead to improved patient outcomes and quality of life.