Review Lectures on Senescence - II. Heterochronic transplantation in the study of ageing

Abstract

Tissues and organs from animals of one age can be transplanted to animals of other ages to form age-chimaeras. Such ‘heterochronic’ preparations have been used to study whether the changes which particular components of the body undergo with increasing age depend on differing programmes of change built into the individual organs or upon a single central control, acting generally and provided by the environment—young or old—in which the tissue finds itself. The results and limitations of such transplantation techniques in analyzing functional changes in ageing animals are exemplified in four different experimental situations. 1. Transplantation of a whole organ—ovarian grafts in an analysis of the factors involved in declining reproduction function. 2. Transplantation of a special unit within an organ—ovum transfer in the same analysis. 3. Transplantation of a sample of an organ—skin grafts used to determine ( а ) the potential lifespan of skin and the viability of old skin grafts. ( b ) the capacity of old animals to mount and to sustain the immunological process of homograft rejection. 4. Transplantation of a sample of a population of cells with specialized functions—the behaviour of suspensions of immunologically competent cells from mice of different ages in the graft-versus-host reaction.