Genetic analysis of the human hair roots as a tool for spaceflight experiments

Abstract

The use of hair roots as experimental samples has been a research focus for understanding the effects of spaceflight on astronauts, because it has many advan-tages, one of which is the fact that hair matrix cells actively divide in a hair follicle and sensitively reflect the physical conditions of the human body. In 2009, a research program focusing on the analysis of astro-nauts' hairs was initiated to examine the effects of long-term spaceflight on the gene expression and mi-neral metabolism in the human body. Since the num-ber of samples per astronaut is limited to 5 strands of hairs at each sampling point, due to the ethical view-point of astronauts or limited resources in space, it is important to develop an effective method for the mo-lecular analysis of small amounts of hair roots. In this study, mRNA successfully extracted from 1, 5, and 10 hair follicles was amplified and subjected to the DNA microarray analysis to compare the gene expression within subjects. The results indicated that (1) it was possible to perform the genetic analysis on hair sam-ples stored at −80˚C, even without a fixation buffer and (2) the newly modified method of mRNA extrac-tion and analysis was effective in detecting differen-tial gene expression in samples containing only 5 hairs. In conclusion, RNA was efficiently extracted from 5 hair roots, which is the same number of hair roots us-ed in the space experiment; therefore, this method can be applied to genetically analyze astronauts' hair amples. s