B. Castillo et al., RETINAL GANGLION-CELL SURVIVAL IS PROMOTED BY GENETICALLY-MODIFIED ASTROCYTES DESIGNED TO SECRETE BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF), Brain research, 647(1), 1994, pp. 30-36
Genetically engineered cells carrying genes for neurotrophic factors h
ave potential application for treatment of neurodegenerative diseases
and injuries to the nervous system. Brain-derived neurotrophic factor
(BDNF) promotes the survival of specific neurons, including retinal ga
nglion cells (RGC). To determine whether genetically engineered astroc
ytes might be used for delivering bioactive BDNF, we infected primary
type 1 rat astrocytes with a retrovirus harboring a human prepro-BDNF
cDNA and assayed the medium conditioned by these astrocytes for effect
s on survival of rat RGCs in vitro. High levels of BDNF mRNA were expr
essed by infected astrocytes, but not by control astrocytes as determi
ned by RNase protection assay using a BDNF specific probe. To test for
secretion of bioactive BDNF from the transgenic astrocytes, embryonic
day 17 rat retinas were dissociated and grown in medium conditioned (
CM) for 24 h by astrocytes infected with a replication deficient retro
virus carrying BDNF, NGF, or alkaline phosphatase (AP) cDNA. After 3 d
ays, the number of Thy-1 immunoreactive RGCs was counted. BDNF astrocy
te CM significantly enhanced RGC survival by 15-fold compared to the A
P control. NGF astrocyte CM had no significant effect. The rate of BDN
F secretion was estimated at 83-166 pg/10(5) cells/h. This study demon
strates that astrocytes can be genetically engineered to synthesize an
d secrete bioactive BDNF. These techniques may be applicable to rescui
ng neurons from degenerative processes and also for enhancing their su
rvival following transplantation.