Hematopoietic stem cell gene therapy for mucopolysaccharidosis type IIIC

Molecular Genetics and Metabolism · 2026-02-01

Treating mucopolysaccharidosis type IIIC with small molecule therapy that stabilizes lysosomal function and reduces inflammation

Molecular Genetics and Metabolism · 2026-02-01

Comprehensive Ocular Characteristics in Cystinosis after Hematopoietic Stem-Cell Gene Therapy Over 24 Months

American Journal of Ophthalmology · 2026-02-09

Hematopoietic Stem-Cell Gene Therapy for Cystinosis

New England Journal of Medicine · 2026-02-18 · 3 citations

BACKGROUND: , the gene encoding cystinosin, a lysosomal transmembrane cystine transporter. In patients with cystinosis, cystine accumulates within lysosomes in all organs. The cystine-depleting agent cysteamine delays but does not prevent disease progression. METHODS: complementary DNA, in patients with cystinosis. The primary end points were the safety and the side-effect profiles of CTNS-RD-04. Secondary end points were measures of efficacy, including white-cell cystine levels and cystine storage depletion. Oral cysteamine was withdrawn before CTNS-RD-04 infusion, and cysteamine eyedrops were withdrawn 1 month after myeloablation. RESULTS: CD34+ cells per kilogram of body weight, and vector copy numbers ranged from 0.59 to 2.91 copies per diploid genome. All the patients had sustained and highly polyclonal hematopoietic reconstitution; vector copy numbers at 24 months ranged from 0.51 to 2.67 copies per diploid genome. A total of 217 adverse events occurred, most of which were mild or moderate in severity and largely consistent with the procedures and underlying disease. No evidence of monoclonal expansion was noted. White-cell cystine levels decreased from baseline except in Patient 4, who had the lowest vector copy number. CONCLUSIONS: In this small study, CTNS-RD-04, an ex vivo gene therapy for cystinosis, had adverse effects that were largely consistent with the myeloablative regimen and underlying disease profile. White-cell cystine levels decreased after therapy. (Funded by the California Institute for Regenerative Medicine and others; ClinicalTrials.gov number, NCT03897361.).

Transplantation of Wild-Type Hematopoietic Stem and Progenitor Cells Improves Disease Phenotypes in a Mucopolysaccharidosis IIIC Mouse Model

Cell Transplantation · 2025-03-24 · 2 citations

Mucopolysaccharidosis type IIIC (MPS IIIC) is a severe neurodegenerative lysosomal storage disease caused by the loss-of-function of the lysosomal transmembrane protein acetyl-CoA: heparan-α-glucosamine N -acetyltransferase. MPS IIIC is characterized by the accumulation of the glycosaminoglycan (GAG) heparan sulfate. There is no treatment for this disease. We generated a new MPS IIIC mouse model and confirmed disease phenotypes such as GAG accumulation, splenomegaly, neurological defects, and presence of disease-specific non-reducing end carbohydrates. To explore a new therapeutic strategy for this condition, we transplanted wild-type (WT) hematopoietic stem and progenitor cells (HSPCs) into lethally irradiated 2-month-old Hgsnat −/− mice and analyzed the resulting impact 6 months later. Transplanted HSPCs differentiated into macrophages in tissues and microglia-like cells in the brain. This resulted in a partial restoration of Hgsnat expression and enzymatic activity along with a significant reduction of the MPS IIIC-specific non-reducing end carbohydrate in the treated Hgsnat −/− mice compared to untreated Hgsnat −/− mice or Hgsnat −/− mice transplanted with Hgsnat −/− HPSCs. In addition, WT HSPC transplant resulted in improved neurological defects, reduction in splenomegaly, and urine retention in the Hgsnat −/− mice. Furthermore, presence of glomerular hyaline bodies with focal fibrosis and sclerosis was observed in the kidney of the disease controls, whereas these abnormalities were improved in the Hgsnat −/− mice treated with WT HSPCs. These data support that HSPC transplantation presents a promising therapeutic avenue for MPS IIIC and represents the first step toward the clinical translation of an HSPC-mediated therapy strategy for MPS IIIC.

Microgliopathy as a primary mediator of neuronal death in models of Friedreich’s Ataxia

Nature Communications · 2025-11-29 · 1 citations

Friedreich's ataxia (FRDA) is an incurable neurodegenerative disorder caused by a GAA repeat expansion in the frataxin (FXN) gene, leading to a severe reduction of the mitochondrial FXN protein, crucial for iron metabolism. While microglial inflammation is observed in FRDA, it remains unclear whether immune dysfunction is a primary disease mediator or a secondary reactionary phenotype. Utilizing patient-derived induced pluripotent stem cells (iPSCs), we report an intrinsic microglial phenotype of stark mitochondrial defects, iron overload, lipid peroxidation, and lysosomal abnormalities. These factors drive a pro-inflammatory state that contributes to neuronal death in co-culture systems. In a murine xenograft model, transplanted human FRDA microglia accumulate in white matter and the Purkinje cell layer, resulting in Purkinje neuron loss in otherwise healthy brains. Notably, CRISPR/Cas9-mediated correction of the GAA repeat reverses microglial defects and mitigates neurodegeneration. Here, we suggest that microglial dysfunction serve as a disease driver and a promising therapeutic target in FRDA.

Cystinosin is involved in Na+/H+ Exchanger 3 trafficking in the proximal tubular cells: new insights in the renal Fanconi syndrome in cystinosis

bioRxiv (Cold Spring Harbor Laboratory) · 2025-02-12 · 2 citations

Cystinosis is a systemic lysosomal storage disease resulting from a defective CTNS gene, leading to the accumulation of cystine in all organs. Despite the ubiquitous expression of cystinosin, the renal Fanconi syndrome (FS) is the first manifestation of cystinosis that presents early in life of the patients while other complications appear years later. Additionally, the cystine reduction therapy, cysteamine, does not prevent the FS. While the matter is still unresolved, it is apparent that specific function(s) of cystinosin in the proximal tubular cells (PTCs) beyond cystine transport explain the early tubular defects in cystinosis. Here, we report a novel interaction of cystinosin with the sodium/hydrogen (Na+/H+) exchanger proteins in the endosomes in both yeast and mammalian cells. One isoform of Na+/H+ exchanger, NHE3, is a major absorptive sodium transporter at the apical membrane of the proximal tubules. Cystinosin was found to play a significant role in NHE3 subcellular localization, trafficking, and resulting sodium uptake in PTCs. Interestingly, introduction of CTNS successfully rescued these defects in CTNS-deficient PTCs, whereas CTNS-LKG, the lysosomal and plasma membrane isoform of cystinosin, did not. NHE3 mislocalization was confirmed in Ctns-/- mice and cystinosis patient kidney. Interestingly, transplantation of wild-type hematopoietic stem and progenitor cells in Ctns-/- mice restored NHE3 expression at the brush border membrane. This study uncovers a new role of cystinosin in the trafficking of NHE3 in the PTCs that is evolutionary conserved, offering new insights in the pathogenesis of the renal FS in cystinosis and potential new therapeutic avenue for this pathology.

Gene editing improves endoplasmic reticulum-mitochondrial contacts and unfolded protein response in Friedreich’s ataxia iPSC-derived neurons

Frontiers in Pharmacology · 2024-02-14 · 13 citations

Friedreich ataxia (FRDA) is a multisystemic, autosomal recessive disorder caused by homozygous GAA expansion mutation in the first intron of frataxin ( FXN ) gene. FXN is a mitochondrial protein critical for iron-sulfur cluster biosynthesis and deficiency impairs mitochondrial electron transport chain functions and iron homeostasis within the organelle. Currently, there is no effective treatment for FRDA. We have previously demonstrated that single infusion of wild-type hematopoietic stem and progenitor cells (HSPCs) resulted in prevention of neurologic and cardiac complications of FRDA in YG8R mice, and rescue was mediated by FXN transfer from tissue engrafted, HSPC-derived microglia/macrophages to diseased neurons/myocytes. For a future clinical translation, we developed an autologous stem cell transplantation approach using CRISPR/Cas9 for the excision of the GAA repeats in FRDA patients’ CD34 + HSPCs; this strategy leading to increased FXN expression and improved mitochondrial functions. The aim of the current study is to validate the efficiency and safety of our gene editing approach in a disease-relevant model. We generated a cohort of FRDA patient-derived iPSCs and isogenic lines that were gene edited with our CRISPR/Cas9 approach. iPSC derived FRDA neurons displayed characteristic apoptotic and mitochondrial phenotype of the disease, such as non-homogenous microtubule staining in neurites, increased caspase-3 expression, mitochondrial superoxide levels, mitochondrial fragmentation, and partial degradation of the cristae compared to healthy controls. These defects were fully prevented in the gene edited neurons. RNASeq analysis of FRDA and gene edited neurons demonstrated striking improvement in gene clusters associated with endoplasmic reticulum (ER) stress in the isogenic lines. Gene edited neurons demonstrated improved ER-calcium release, normalization of ER stress response gene, XBP-1, and significantly increased ER-mitochondrial contacts that are critical for functional homeostasis of both organelles, as compared to FRDA neurons. Ultrastructural analysis for these contact sites displayed severe ER structural damage in FRDA neurons, that was undetected in gene edited neurons. Taken together, these results represent a novel finding for disease pathogenesis showing dramatic ER structural damage in FRDA, validate the efficacy profile of our FXN gene editing approach in a disease relevant model, and support our approach as an effective strategy for therapeutic intervention for Friedreich’s ataxia.

Reconstitution of Rab11-FIP4 Expression Rescues Cellular Homeostasis in Cystinosis

Molecular and Cellular Biology · 2024-10-22 · 2 citations

fibroblasts re-established normal autophagosome levels and decreased LC3B-II expression in cystinotic cells. Furthermore, Rab11-FIP4 reconstitution increased the localization of the chaperone-mediated autophagy receptor LAMP2A at the lysosomal membrane. Treatment with genistein, a phytoestrogen that upregulates macroautophagy, or the CMA activator QX77 (CA77) restored Rab11-FIP4 expression levels in cystinotic cells supporting a cross-regulation between two independent autophagic mechanisms, lysosomal function and Rab11-FIP4. Improved cellular homeostasis in cystinotic cells rescued by Rab11-FIP4 expression correlated with decreased endoplasmic reticulum stress, an effect that was potentiated by Rab11 and partially blocked by expression of a dominant negative Rab11. Restoring Rab11-FIP4 expression in cystinotic proximal tubule cells increased the localization of the endocytic receptor megalin at the plasma membrane, suggesting that Rab11-FIP4 reconstitution has the potential to improve cellular homeostasis and function in cystinosis.

Transplantation of Wild-Type Hematopoietic Stem and Progenitor Cells Improves Disease Phenotypes in Novel Mucopolysaccharidosis Iiic Mouse Model

SSRN Electronic Journal · 2024-01-01