Modification of strain-specific femoral bone density by bone marrow chimerism in mice: a study on the spontaneously osteoporotic mouse (SAM-P/6).

The role of marrow-derived cells in determining strain differences in femoral bone density in mice was investigated by inducing marrow chimerism in a newly developed, osteoporotic strain of mouse: SAM-P/6. As a normative study prior to the chimeric experiment, bone density of F1 hybrids between SAM-P/6 and SAM-P/2 (strain with a high bone density) was assessed. Microdensitometrically, the F1(P2P6F1) exhibited a significantly higher bone density than did the SAM-P/6. P2P6F1 marrow cells, injected into SAM-P/6 neonates, increased the bone density at age 60 days while the syngeneic cells were without effect. The successful induction and maintenance of chimerism was confirmed by flow cytometry in which a donor-specific H-2K haplotype was used as the marker. This study shows that, at least in certain combinations of strains of mice, strain-specific bone density can be modified by bone marrow chimerism. Also, it suggests that the low bone density observed in the SAM-P/6 might reflect functional characteristics of the marrow-derived cells.