Epigenetics and aging: status, challenges, and needs for the future.

The interest in exploring the role of epigenetics in the aging process has grown tremendously in recent years as demonstrated, in part, by the steadily increasing number of papers that have been published in the area. In addition, there has been and continues to be rapid improvement in the technologies needed to do the work. However, significant challenges remain, not the least of which is inherent to the aging process itself, that is, that even given a uniform genetic background and external environment, aging is a "heterogeneous" phenomenon with variation in the expression of the aging phenotype evident both between and within individuals. Thus, there is a pressing need to find experimental approaches that recognize this reality and deal with it effectively whether it is in the choice of animal model, cell, or tissue sampling or the use of techniques capable of analyzing small samples, ideally in situ and in a longitudinal fashion. Undoubtedly, because of the complexity of the situation and what are likely to be very large data sets, bioinformatics and systems biology are also going to be needed, something discussed in detail elsewhere in the report of the meeting.