Comparison of haemopoiesis in young and old mice.

Haemopoietic status and functions have been compared in young (2-3-month-old) and old (2-2.5-year-old) BDF1 mice. The parameters measured include total marrow cellularity, CFU-S, CFU-mix, GM-CFC, BFU-E and CFU-F. In all cases the numbers of these cells in the femoral marrow of the old mice was equal to or greater than those in the femoral marrow of young mice. In addition to these parameters we have compared the ability of marrow from young and old mice to repopulate the marrow of recipient mice whose marrow had been eliminated by radiation; to grow in long-term bone marrow cultures; to produce ectopic grafts of marrow beneath the renal capsule of normal recipients; and to supply inhibitor and stimulator of stem cell proliferation in the marrow and to resynthesise these substances. We could detect no differences in any of these functions with the exception of that of resynthesis of the stem cell regulator substances, which appears to be somewhat slower in the old mice. This, however, does not impose any limitation upon the ability of the marrow to function either under normal conditions or in conditions requiring rapid proliferation. Therefore we can find no evidence whatsoever to suggest that aging of the haemopoietic system plays any part in aging of the individual or influencing the life-span.