Neural stem cells produce new nerve cells in the mammalian brain throughout their life. However, aging greatly reduces the potential of this regenerative ability. Scientists at the University of Zurich have now identified a unique mechanism that allows neural stem cells to remain relatively free from age-induced damage. The novel method is a diffusion barrier that regulates the categorization of damaged proteins through cell division.
Defining The Diffusion Barrier
It was previously known that aging factors are asymmetrically distributed among parent and daughter cells during every subsequent cell division. This facilitates the rejuvenation and entire life span of the daughter cell irrespective of the age of the parent cell. This is partially possible due to the existence of a diffusion barrier that restricts the movement of molecules from one side to the other as a cell divides.
Researchers led by Sebastian Jessberger of the Brain Research Institute have now demonstrated this phenomenon in stem cells of adult mice. The diffusion barrier lies in the endoplasmic reticulum (an organelle within the cell that forms channels for synthesis and transport of protein). This barrier prevents damaged proteins from being stored inside daughter stem cells, keeping them fairly clean.
Young Forever: Barrier Weakens With Advancing Age
Moreover, the new study published in Science observed that the vigor of this barrier weakens as the neural stem cells age. This leads to a decrease in the asymmetry of categorization of damaged protein. This might be among the mechanisms involved in the reduced regeneration capacity of aged brains, since stem cells that preserve greater amounts of unwanted proteins take a longer time to initiate a subsequent cell division.
“This is an exciting new mechanism involved in stem cell division and aging”, Jessberger stated. “But presently we are simply beginning to understand the molecular constituents and the actual meaning of this barrier for stem cell division in the brain”.
An important question that remains to be answered is whether this barrier exists in all somatic stem cells throughout the body. Uncovering this aspect could open new avenues for age-dependent modifications of stem cells to treat human diseases.