Origin and Recovery of Colony-forming Units in Locally Curetted Bone Marrow of Mice

Histologic study of locally curetted bone marrow showed a sequence of blood clot formation, displacement of the clot by a primitive reticular tissue, and hematopoietic regeneration. Histologic regeneration of sinusoidal vessels, and recovery was incomplete 12 wk later with increased fat, residual trabecular bone, and cystic areas. Recovery of colony-forming units (CFU) paralleled hematopoietic cellular recovery and did not exceed levels of 70% of normal by 12 wk postcurettage. Transplantation of cureted and irradiated mice with T₆T₆ marker chromosomes demonstrated that cells with marker chromosomes migrated readily into irradiated marrow but were excluded from the curetted marrow for 2 wk after curettage. Three weeks after, curettage marker cells gained ready access to curetted marrow. The early exclusion but later appearance of transplanted marker cells was correlated with the early absence and later regeneration of sinusoidal vessels. The histologic and cytogenetic studies support the concept of a dependence of hematopoiesis upon a sinusoidal system with an appropriate marrow microenvironment. These studies support the concept of a local origin of marrow regeneration within curetted cavities but do not indicate whether the hematopoietic tissue originates from small numbers of residual CFU surviving curettage or from multipotential reticular cells. There was no evidence of a stimulatory effect upon uncuretted marrow by the action of curettage.