As you age you naturally lose neurons and muscle mass and experience a decline in fertility and wound healing ability. Previous research in animals has offered several potential techniques for turning back the biological clock in specific tissues, including exercise and calorie restriction. However, age reversal of blood cells or at whole organism level has so far been elusive.

From fertilization to around 18 months, planarians, like mammals, show signs of decline, notes Guo, including the loss of neurons, muscle and diminished fertility. One of their more obvious signs of age is abnormal changes in their eyes over time. When the older planarians’ heads were removed, however, they generated new heads with normal eyes.

Further studies found that worms that had undergone regeneration also saw improved fertility as well as renewed physiological performance when compared to older planarians.

Source:

Regeneration leads to global tissue rejuvenation in aging sexual planarians

https://www.nature.com/articles/s43587-025-00847-9