In a fascinating study published in Nature, researchers found that the A1 astrocytes formed following injury may not be helpful, but actually quite harmful. In a healthy brain, astrocytes assist with developing a vast network of connected neurons. Upon injury these same cells act as cleaners, seeking out damaged connections for removal. Unfortunately, removal of dead and damaged debris may contribute to impaired functioning. Moheb Constandi of ScientificAmerican.com summarized this:
To determine whether A1 astrocytes retain either the building or repair functions, Liddelow and his colleagues grew retinal ganglion cells, which form the optic nerve, together with either A1 astrocytes or nonactivated astrocytes. Petri dishes with A1 astrocytes added to them contained approximately 50 percent fewer synaptic connections compared with those holding nonactivated ones. And the remaining synapses were significantly weaker, producing smaller and less frequent signals than those in the dishes containing nonactivated astrocytes.
Together with removal of damaged debris, suppression of oligodendrocytes was also observed. Oligodendrocytes are known to assist with the myelin sheath layer. It is that layer that insulates electrical signals passing through axons. Failing of this layer are observed in conditions like multiple sclerosis and are understood to contribute to headaches and migraines.