Mitochondrial transplantation using encapsulated donor mitochondria shows strong potential to treat mitochondrial diseases such as thymidine kinase 2 deficiency (TK2d), according to a study published recently in Cell.
The experimental therapy restored mitochondrial function in cells and improved disease features in multiple animal models, suggesting a possible future treatment option for patients who currently have limited therapies.
“We developed a highly efficient method for delivering mitochondria into cells or tissues, offering potential treatments for mitochondrial diseases,” said the study’s authors.
The approach involves packaging healthy mitochondria inside vesicles made from red blood cell membranes, creating “mitochondrial capsules” that can efficiently enter cells. Encapsulation efficiency ranged from 22.67% to 35.76% using mouse membranes and 18.26% to 27.37% using human membranes. These capsules showed higher energy activity than free mitochondria, with increased membrane potential and ATP production, indicating stronger cellular energy output.
Once delivered, donor mitochondria successfully entered about 80% of recipient cells and integrated with the cells’ existing mitochondrial network within 48 hours. Importantly, the transplanted mitochondria avoided breakdown inside cellular compartments and remained functional.
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Donor mitochondrial DNA levels reached approximately 71% within two days and persisted for at least seven days, demonstrating sustained genetic correction. For conditions such as TK2d, where mitochondrial DNA is depleted, this type of restoration is particularly relevant.
In laboratory models using patient-derived cells with mitochondrial disease, the therapy reduced harmful mitochondrial DNA mutations and improved cellular energy production. For example, mutation rates dropped from 14.4% to 2.67% in one model and from 92.6% to 73.3% in another. Oxygen consumption, ATP production and overall cell survival all improved, suggesting that the treatment not only corrects genetic defects but also restores function.
Animal studies further supported these findings. In mouse models of mitochondrial DNA depletion syndrome, a condition closely related to TK2d, treatment increased body weight, improved liver function and restored mitochondrial DNA levels. In a model of Leigh syndrome, median survival increased from 48.5 days to 74 days with mitochondrial capsules. The therapy also improved mobility and physical performance, indicating meaningful functional recovery.
The treatment showed promise beyond genetic mitochondrial disorders. In a Parkinson’s disease mouse model, mitochondrial transplantation prevented neuron loss, restored motor function and improved brain mitochondrial activity for at least three months. These findings suggest broader applications for diseases driven by mitochondrial dysfunction.
For patients with TK2d, this research signals a potential future shift in care. Instead of only managing symptoms, future therapies could directly replace damaged mitochondria and restore cellular energy production. While the work is still experimental and not available clinically, it offers hope for a disease that currently has few treatment options.
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