This research will tell you how sleep helps in reviving and augmenting brain cells that play a role in boosting response to injuries, repair and growth.

Researchers from the University of Wisconsin, Adison, evaluated gene activity in specific cell types, oligodendrocytes, during experiments on mice that slept and some that were awake.
Study showed that during sleep, the genes that boosted the formation of myelin were turned on. Alarmingly, the genes connected to death of cells were active during wake up time.
This led researchers to also guess that chronic sleep deprivation could even aggravate some symptoms of multiple sclerosis (MS), a disease that damages myelin.
Source-Medindia