Scientists in China have developed a "capsule" delivery system to transplant healthy mitochondria into diseased cells, a breakthrough that could lead to new treatments for Parkinson's disease, rare genetic disorders and the general effects of aging.

The study, published recently in the journal Cell, offers a potential solution to a long-standing hurdle in regenerative medicine: how to replace the failing "power plants" of a cell without damaging them in the process.

Mitochondria are organelles — tiny, specialized structures inside nearly every human cell — that act as miniature power stations. They convert nutrients from food into the energy required to sustain life and manage the body's metabolism.

Unlike other parts of the cell, mitochondria carry their own unique DNA. When that genetic code is disrupted or mutated, cells lose their ability to function. These defects affect approximately one in 5,000 people globally and contribute to the steady decline of health as people age.

"For a long time, doctors have only been able to treat symptoms of such diseases temporarily rather than fundamentally repairing defective mitochondria," said Liu Xingguo, lead researcher at the Chinese Academy of Sciences' Guangzhou Institutes of Biomedicine and Health.

The primary challenge in mitochondrial therapy is fragility. Mitochondria are easily destroyed when researchers try to inject them into a patient's tissue. To solve this, Liu's team-working with the Guangzhou Medical University and other institutions — created a delivery vehicle using membranes from red blood cells.

The researchers used these membranes as shells to encapsulate healthy mitochondria, creating capsules just 1 micrometer in diameter, or one-thousandth of a millimeter. This shell acts as a "protective suit" for the mitochondria and serves as a biological bypass. It allows the capsule to slip through a cell's natural defenses and fuse with the interior, where the healthy mitochondria can begin working alongside the cell's original structures.

The team tested the technique on mice with various conditions caused by mitochondrial failure. In studies related to Parkinson's disease, the capsules prevented the death of neurons in the brain, restored normal energy functions and improved the mice's motor skills to near-normal levels.

In models of mitochondrial DNA depletion syndrome — a condition where the body cannot maintain enough mitochondrial DNA — the treatment significantly extended the lifespan of the mice and saved multiple organs from failing. The research suggests that by "recharging" cells with fresh mitochondria, aging organs could potentially be rejuvenated.

Researchers said the breakthrough marks a milestone in a burgeoning field called organelle therapy. Rather than using traditional chemicals or complex gene editing, the treatment uses the cell's own machinery as a form of medicine.

"Healthy organelles such as mitochondria may potentially be used as a form of medicine to be directly delivered into patients to restore the functions of diseased tissues and organs," Liu said. While the results in mice are a significant step forward, further clinical trials will be required to determine if the "capsule" method is equally safe and effective for human patients.

zhengcaixiong@chinadaily.com.cn