Increasingβ-hexosaminidase A activity using genetically modified mesenchymal stem cells

GM2 gangliosidoses are a group of autosomal-recessive lysosomal storage disorde rs.These diseases result from a deficiency of lysosomal enzymeβ-hexosaminidase A(HexA),which is responsible for GM2 ganglioside degradation.HexA deficiency causes the accumulation of GM2-gangliosides mainly in the nervous system cells,leading to severe progressive neurodegeneration and neuroinflammation.To date,there is no treatment for these diseases.Cell-mediated gene therapy is considered a promising treatment for GM2 gangliosidoses.This study aimed to evaluate the ability of genetically modified mesenchymal stem cells(MSCs-HEXA-HEXB)to restore HexA deficiency in Tay-Sachs disease patient cells,as well as to analyze the functionality and biodistribution of MSCs in vivo.The effectiveness of HexA deficiency cross-correction was shown in mutant MSCs upon intera ction with MSCs-HEXA-HEXB.The results also showed that the MSCs-HEXA-HEXB express the functionally active HexA enzyme,detectable in vivo,and intravenous injection of the cells does not cause an immune response in animals.These data suggest that genetically modified mesenchymal stem cells have the potentials to treat GM2 gangliosidoses.

Extracellular vesicles in the diagnosis and treatment of central nervous system diseases

Extracellular vesicles,including exosomes and microvesicles,play a fundamental role in the activity of the nervous system,participating in signal transmission between neurons and providing the interaction of central nervous system with all body systems.In many neurodegenerative diseases,neurons pack toxic substances into vesicles and release them into the extracellular space,which leads to the spread of misfolded neurotoxic proteins.The contents of neuron-derived extracellular vesicles may indicate pathological changes in the central nervous system,and the analysis of extracellular vesicle molecular content contributes to the development of non-invasive methods for the diagnosis of many central nervous system diseases.Extracellular vesicles of neuronal origin can be isolated from various biological fluids due to their ability to cross the blood-brain barrier.Today,the diagnostic potential of almost all toxic proteins involved in nervous system disease pathogenesis,specificallyα-synuclein,tau protein,superoxide dismutase 1,FUS,leucine-rich repeat kinase 2,as well as some synaptic proteins,has been well evidenced.Special attention is paid to extracellular RNAs mostly associated with extracellular vesicles,which are important in the onset and development of many neurodegenerative diseases.Depending on parental cell type,extracellular vesicles may have different therapeutic properties,including neuroprotective,regenerative,and anti-inflammatory.Due to nano size,biosafety,ability to cross the blood-brain barrier,possibility of targeted delivery and the lack of an immune response,extracellular vesicles are a promising vehicle for the delivery of therapeutic substances for the treatment of neurodegenerative diseases and drug delivery to the brain.This review describes modern approaches of diagnosis and treatment of central nervous system diseases using extracellular vesicles.

Functionality of a bicistronic construction containing HEXA and HEXB genes encoding β-hexosaminidase A for cell-mediated therapy of GM2 gangliosidoses

Tay-Sachs disease and Sandhoff disease are severe hereditary neurodegenerative disorders caused by a deficiency ofβ-hexosaminidase A(HexA)enzyme,which results in the accumulation of GM2 gangliosides in the nervous system cells.In this work,we analyzed the efficacy and safety of cell-mediated gene therapy for Sandhoff disease and Sandhoff disease using a bicistronic lentiviral vector encoding cDNA of HexAα-andβ-subunit genes separated by the nucleotide sequence of a P2A peptide(HEXA-HEXB).The functionality of the bicistronic construct containing the HEXA-HEXB genetic cassette was analyzed in a culture of HEK293T cells and human umbilical cord blood mononuclear cells(hUCBMCs).Our results showed that the enzymatic activity of HexA in the conditioned medium harvested from genetically modified HEK293T-HEXA-HEXB and hUCBMCs-HEXA-HEXB was increased by 23 and 8 times,respectively,compared with the conditioned medium of native cells.Western blot analysis showed that hUCBMCs-HEXA-HEXB secreted both completely separated HEXA and HEXB proteins,and an uncleaved protein containing HEXA+HEXB linked by the P2A peptide.Intravenous injection of genetically modified hUCBMCs-HEXA-HEXB to laboratory Wistar rats was carried out,and the HexA enzymatic activity in the blood plasma of experimental animals,as well as the number of live cells of immune system organs(spleen,thymus,bone marrow,lymph nodes)were determined.A significant increase in the enzymatic activity of HexA in the blood plasma of laboratory rats on days 6 and 9(by 2.5 and 3 times,respectively)after the administration of hUCBMCsHEXA-HEXB was shown.At the same time,the number of live cells in the studied organs remained unchanged.Thus,the functionality of the bicistronic genetic construct encoding cDNA of the HEXA and HEXB genes separated by the nucleotide sequence of the P2A peptide was shown in vitro and in vivo.We hypothesize that due to the natural ability of hUCBMCs to overcome biological barriers,such a strategy can restore the activity of the missing enzyme in the central nervous system of patients with GM2 gangliosidoses.Based on the obtained data,it can be concluded that intravenous administration of hUCBMCs with HexA overexpression is a promising method of the therapy for GM2 gangliosidoses.The animal protocol was approved by the Animal Ethics Committee of the Kazan Federal University(No.23)on June 30,2020.