Regeneration of Marrow Tissue

The regenerative potential of chronically iron-deficient rat marrow was studied in extramedullary marrow autotransplants and intramedullary cavity after ablation. Subcutaneous implantation of normal marrow results consistently in establishment of a marrow nodule with a mean weight ratio of 3O.7#{176}/o of the implanted tissue. In iron deficiency, the mean weight ratio was 7.1#{176}/o, and the take was 11#{176}/o. After ablation of femoral marrow, the regenerative process proceeds distally from the uninjured marrow at the femoral head. The process of regeneration reached the midshaft after 11 days in iron-deficient animals but took only 5 days for normal animals. Iron repletion accelerated the process toward normal. These results are consistent with biochemical data from iron-deficient marrow (low nucleic acid content, decreased incorporation of 3H-thymidine into DNA, and decreased utilization of 59Fe and ‘4C-glycine for heme synthesis) and suggest that the reported hypercellularity of the marrow in iron deficiency may reflect sequestration of erythroid precursors, rather than the compensatory mechanism of increased cell proliferation.