Telomerase induction in astrocytes of Sprague-Dawley rat after ischemic brain injury.

Telomerase, a reverse transcriptase, consists of an RNA template and protein polymerase. This ribonucleoprotein protects the linearized chromosomal end region and elongates the telomere during chromosomal replication. Telomerase is not expressed in adult somatic cells but it shows high activity in most cells during embryonic development. We report, by RT-PCR and immunohistochemical results, that the induction of telomerase protein catalytic subunit (TERT) in transient middle cerebral artery occlusion induced brain injury. TERT mRNA emerged 24 h after ischemia. We examined which brain cell expressed TERT in the penumbra region of injured brain. The expression of TERT began from 24 h and remained until 5 days after ischemia. We identified that TERT was co-localized with the astrocyte marker, GFAP, at 3 days after ischemia. This is strong evidence that TERT is induced in astrocytes when the brain is damaged by ischemia, and that this enzyme may play an important role in ischemic brain injury.