Abstract Body (Do not enter title and authors here): Background: Danon disease is a fatal X-linked lysosomal storage disorder caused by loss of lysosome-associated membrane protein 2 (LAMP2), leading to severe cardiomyopathy and intellectual disability. Without advanced therapies, most patients progress to end-stage heart failure or early death. Prior studies suggest intercellular transfer of lysosomes from macrophages to cardiomyocytes, supporting the potential of hematopoietic stem cell transplantation as a therapeutic strategy.
Aims: We evaluated whether ex vivo gene-modified hematopoietic stem and progenitor cells (HSPCs) could deliver LAMP2B to affected tissues and improve outcomes in a murine model of Danon disease. We hypothesized that transplantation of HSPCs transduced with a lentiviral vector encoding human LAMP2B (pALD-LAMP2B) would restore LAMP2B expression and ameliorate disease features.
Methods: Sca-1 positive HSPCs were isolated from Lamp2 KO mice and transduced with pALD-LAMP2B (n=5) or left unmodified (n=6). Cells were transplanted into busulfan-conditioned 12–15-week-old Lamp2 KO recipients. Age-matched wild-type (WT, n=7) and untreated KO mice (n=3) served as controls. Six months post-transplant, invasive hemodynamics, immunofluorescence, and neurobehavioral testing were performed.
Results: Immunofluorescence confirmed human LAMP2B expression in hearts of KO mice receiving gene-corrected HSPCs. These mice exhibited improved cardiac function compared to those receiving unmodified KO HSPCs (End diastolic pressure: p=0.005; Tau: p=0.06; Max dP/dt: p=0.28; Min dP/dt: p=0.30). In open field tests, KO mice had impaired locomotor activity versus WT, with reduced walking distance and speed. Mice treated with gene-corrected HSPCs showed improvement in these parameters toward WT levels, with favorable trends in immobility time, thigmotaxis, and exploratory behavior.
Conclusions: Transplantation of gene-modified HSPCs restored LAMP2B expression in the heart and improved both cardiac and neurobehavioral outcomes in a Danon disease mouse model. This study provides the first evidence supporting cardiac-targeted HSPC-based gene therapy for a monogenic disease. Larger studies are warranted to confirm therapeutic efficacy and assess long-term outcomes.