The Brain Is Often Called The Commander Of The Whole Body. In Order To Protect This Important Organ From Microbial Infection Or Other Toxic Substances, Abundant Blood Vessels Form A Barrier Between Brain Parenchyma And Blood. The Blood-brain Barrier, Mainly Composed Of Vascular Cells, Strictly Filters The Substances Entering The Brain From The Blood, So As To Ensure That The Brain Is In A Relatively Stable And Safe Environment.
At The Same Time, Microglia Stationed In Brain Tissue, As Innate Immune Cells, "monitor" The Environment Of Brain Parenchyma, Recognize And Devour Pathogens, And Build A Defense Line To Protect The Brain.
Another Important New Member Of The Immune Defense Line That Protects The Brain Has Only Recently Been Known. Their Research On The Formation Of The Brain Barrier, Published For The First Time By Researchers From The University Of Freiburg And Other Leading Journals In Germany, Reveals Another Important Process Of Brain Cell Enhancement.
The Researchers Pointed Out That A Detailed Analysis Of These Special Immune Cells Is Expected To Clarify The Mechanism Of Brain Development, As Well As The Pathogenesis And Treatment Direction Of Various Brain Diseases.
The Immune Cells Concerned In This Study Belong To Macrophages Like Microglia. However, Unlike Microglia, Which Are Distributed In The Brain Parenchyma, These Macrophages Are Located In The Meninges And Around Blood Vessels Surrounding The Brain.
With The Help Of Cutting-edge Single-cell Analysis Technology, Cell Fate Tracking Technology And The Constructed Cell Specific Transgenic Mouse Model, The Researchers Marked Different Types Of Brain Macrophages And Their Progenitor Cells In This Study, And Confirmed That These Special Macrophages And Microglia Distributed In The Meninges, Blood Vessels And Other Parts Have Common Progenitor Cells In The Embryonic Stage.
▲ Microscopic Image Showing Macrophages In Different Tissues Of Mouse Brain (image Source: Reference [2 ]; Credit: Medical Center - University Of Freiburg / Dr. Lukas Amann)
However, Although Precursor Cells Are In Place Early In The Brain, These Special Macrophages Mature Later Than Expected. By Examining The Genetic Activity Of Individual Cells, The Researchers Confirmed Their Maturity.
"We Found That These Immune Cells Migrate From The Meninges To The Cerebral Vessels Shortly Before Birth And Mature There. The Process Can Be Completed About A Few Weeks After Birth." Professor Marco Prinz, Co-author Of The Study, Said, "the Brain Is Fragile At The Beginning Of Life, And I Think That's Part Of The Reason."
Further Research Shows That The Reason Why These Special Brain Macrophages Do Not Mature Until After Birth Depends On The Important Signals Provided By Vascular Smooth Muscle Cells.
"In Addition To The Blood-brain Barrier, These Immune Cells We Studied Also Control What Can Reach Brain Cells From The Blood. They Swallow Pathogens And Prevent Excessive Inflammation. They Are Also Involved In The Development Of Cancer, Alzheimer's Disease And Multiple Sclerosis." Professor Prinz Added.
The Researchers Believe That With The Deepening Understanding Of These Brain Immune Cells, There Will Be A New Understanding Of The Pathogenesis Of These Diseases, And There Will Be An Opportunity To Develop New Cell-specific Therapies On This Basis.
Reference Material:
[1] Takahiro Masuda et al。， Specification of CNS macrophage subsets occurs postnatally in defined niches。 (2022) Nature https://doi.org/10.1038/s41586-022-04596-2
[2] New discoveries about the origin of the brain‘s immune system。 Retrieved Apr。 24， 2022 from https://medicalxpress.com/news/2022-04-discoveries-brain-immune.html