The regional distribution of fibroblastoid progenitors in murine femoral marrow revisited.

The distribution of fibroblastoid colony-forming units (CFU-F) in mouse femoral marrow was investigated. Mechanically dispersed marginal and axial marrow fractions had the same CFU-F frequency. Metaphyseal marrow had a high CFU-F frequency in young (6 week) mice. Trypsinization of bone marrow fractions before mechanical dispersion resulted in an increased CFU-F plating efficiency and a higher incidence of CFU-F in marginal marrow (156 +/- 41%) than in axial marrow. The femoral marrow CFU-F distribution correlates with that expected on the basis of their role in both bone and marrow stroma formation.