Abstract
Abstract: :
Purpose: Age–related gene expression changes play a major role in increased susceptibility for age–related diseases. However, human donor samples are highly variable due to idiopathic pre–mortem and post–mortem conditions. Old world monkeys are extensively utilized for aging research, to reduce the intrinsic variability seen with human tissue. We have generated a large collection of young and old monkey retinal tissue. We utilized real time polymerase chain reaction (PCR) to compare the relative gene expression similarities and differences between human and rhesus monkey. We used a common retina–expressed internal standard to evaluate intrinsic human–: rhesus assay variation, and age–related gene expression differences. Methods: Human cyclophilin B and rhodopsin primers were used. DNAse–1 treated total RNA was isolated from human and rhesus retina. cDNAs were generated using the reverse transcription reaction with 1ug of total RNA and random hexamer. Real–time PCR was performed using Sybr green as a fluorescent dye. Statistic analysis was performed using the cycle threshold number. External standardization was performed with known substrate concentrations. Results: 8 young and 12 old individuals in human group, and 18 young and old individuals in monkey groups were used in the study. Cyclophin B showed the least variable, 25.95cycles +/– SD1.07 in young monkey vs 26.19+/– SD1.39 in old monkeys, and 27.24 +/– SD 4.90 in young and 23.77+/– SD 1.09 in old human. There was a difference between the total cycle number needed to reach threshold between the two groups in humans, but not monkeys; monkeys showed the least difference between the two age groups. Cyclophilin B showed the least variation in the young monkey group, followed by old human and old monkey, and finally young human. RQ–PCR using human rhodopsin primers on the same samples revealed that rhodopsin mRNA levels remained relatively constant in all samples. Conclusions: Monkey retinal tissue shows less intrinsic variability than human donor tissue. Cyclophin B is a suitable internal standard for studying relative gene expression in retina in both species. The overall concentration of cyclophin B mRNA in both humans and monkey retina are similar. Rhesus monkeys have age related diseases similar to humans and relatively similar retinal mRNA expression patterns, therefore they are an excellent model for studying age related retinal diseases.
Keywords: aging • gene/expression • retina