Lysosomal dysfunctionin human iPSC-derived models of MPSIII

Katharina Günther, Frank Edenhofer The goal of this project is to establish an authentic human disease model of the lysosomal storage disease (LSD) Mucopolysaccharidosis IIIB (MPS IIIB), often referred to as Sanfilippo Syndrome. Using a method called cellular reprogramming, we aim to better understand the cellular dysfunction as well as to develop novel therapeutic approaches for MPS IIIB. LSDs are a group of inheritable metabolic disorders characterized by defects in the lysosomal degradation (cellular trash bin) pathway resulting in the undesired accumulation of metabolites that result in cell dysfunction or even cell death. LSDs typically affect the central nervous system (CNS) and represent the most frequent form of neurodegeneration in early life. Usually, initial MPS IIIB symptoms such as sight decline, developmental delay, sleeping troubles, and behavioral problems occur with high load of storage material at the age of 2 to 6 years. During the following years, destructive and aggressive behavior worsens. Further, it is accompanied by continuous loss of motor and mental function, which ultimately result in dementia. We will investigate the contribution of lysosomal pathway dysfunction to neurodegeneration by applying models of the brain and eye using patient-derived reprogrammed cells. Through reprogramming, skin-derived cells from patients and healthy control individuals are converted into induced pluripotent stem cells which have an unlimited self-renewal potential and can give rise to any cell type of the body. By applying specific protocols, we will generate and analyze patient-specific adherent neuronal networks, retinal cells and floating organoid structures resembling parts of the human brain (human brain in a petri dish). The application of state-of-the-art analytic methods will allow us to assess to which extent the disease is recapitulated in a petri dish and consequently enhance the understanding of the molecular hallmarks and disease mechanisms of MPS IIIB. We expect this knowledge to contribute to pave the way for effective cure in a personalized manner. Thanks to our collaboration with the clinicians from the Martin Zeitz Center for Rare Diseases in Hamburg, we are able to use samples from MPS IIIB patients that are active participants in a clinical study. This will enable us a direct patient-specific assessment and eventually the prediction of therapy efficacy. In conclusion, by combining stem cell research and personalized precision medicine, we anticipate major advances in MPS IIIB disease understanding in particular and rare neurological diseases in general to facilitate clinical translation to novel therapeutic cures.

The goal of this project was to establish an authentic human disease model of the lysosomal storage disease (LSD) Mucopolysaccharidosis IIIB (MPS IIIB), also known as Sanfilippo Syndrome. Using a method called cellular reprogramming, we aimed to better understand the cellular dysfunction associated with MPS IIIB and to develop novel therapeutic approaches. LSDs are a group of inheritable metabolic disorders characterized by defects in the lysosomal degradation pathway (the cellular trash bin), resulting in the undesired accumulation of metabolites that cause cell dysfunction or even cell death. LSDs typically affect the central nervous system (CNS) and are the most frequent form of neurodegeneration in early life. Initial MPS IIIB symptoms, such as vision decline, developmental delay, sleep disturbances, and behavioral problems, usually occur between the ages of 2 and 6 years, when there is a high load of storage material. As the disease progresses, destructive and aggressive behaviors worsen, accompanied by a continuous loss of motor and mental function, ultimately resulting in dementia. In this project, we investigated the contribution of lysosomal pathway dysfunction to neurodegeneration by using models of the brain and eye derived from patient-reprogrammed cells. Through reprogramming, skin-derived cells from patients and healthy controls were converted into induced pluripotent stem cells, which have unlimited self-renewal potential and can differentiate into any cell type of the body. By applying specific protocols, we generated and analyzed patient-specific adherent neural stem cells, neuronal networks, and floating organoid structures that resemble parts of the human brain (a "human brain in a petri dish"). Using state-of-the-art cell biological and molecular methods, we demonstrated that we could recapitulate key disease hallmarks, such as enlarged lysosomes and the accumulation of glycosaminoglycans, in a petri dish. Importantly, these features were reversed following the replacement of the malfunctioning protein. Additionally, patient-derived brain organoids exhibited reduced growth and altered cell composition compared to healthy controls. Furthermore, we used CRISPR/Cas technology to correct the pathogenic mutation in the NAGLU gene, leading to a reduction in disease-associated features. In summary, we report a 2D/3D disease model of MPS IIIB that recapitulates important disease features and enables the assessment of underlying neurodegenerative mechanisms. By combining stem cell research with personalized precision medicine, we anticipate major advances in understanding MPS IIIB and other rare neurological diseases, facilitating the clinical translation of novel therapeutic cures.