University of Tokyo researchers identify non-lethal "zombie" pathway driving blood stem cell aging and immune decline

New research reveals how the MLKL protein damages mitochondria to drive stem cell aging, offering a new target to preserve immune health during aging and treatment.

By: AXL Media

Published: Apr 16, 2026, 8:01 AM EDT

Source: Information for this report was sourced from The Institute of Medical Science, The University of Tokyo

A Shift in Understanding Stem Cell Deterioration

Scientists from The University of Tokyo and St. Jude Children’s Research Hospital have uncovered a mechanism that explains how age-related stresses lead to the functional decline of hematopoietic stem cells (HSCs). These cells are responsible for the continuous production of all blood types, but as they age, they lose their effectiveness, leading to a weakened immune system and a bias toward producing myeloid cells over lymphoid cells. While factors like chronic inflammation and DNA damage were previously known to play a role, the precise pathway that integrates these stresses has remained elusive. The new study identifies a non-lethal role for the MLKL signaling axis, a pathway historically associated only with necroptosis, or programmed cell death.

The Non-Lethal Role of Death Proteins

The investigation was sparked by an unexpected observation in mice deficient in MLKL. Researchers noted that when these mice were subjected to repeated chemical stress, their stem cells showed significantly fewer signs of aging compared to normal mice, despite no measurable difference in cell death rates. This prompted Dr. Masayuki Yamashita and his team to explore whether MLKL could alter cell function without actually killing the cell. Published in Nature Communications, the findings indicate that MLKL can be activated by stress in a transient manner, acting as a functional regulator rather than a "kill switch" for the stem cell.

Mitochondrial Damage as a Driver of Aging

Using advanced biosensors and high-resolution microscopy, the team discovered that activated MLKL localizes specifically to the mitochondria within stem cells. Once there, it causes direct structural damage and reduces the membrane potential, which is essential for energy production. This mitochondrial dysfunction forces the HSCs to adopt the hallmark traits of aging: they struggle to self-renew and fail to produce a balanced variety of blood cells. Crucially, this process occurs at the organelle level and through post-transcriptional mechanisms, meaning the damage happens directly to the cell’s internal machinery rather than through changes in gene activity or inflammation.