MODIFICATION OF STRAIN-SPECIFIC FEMORAL BONE-DENSITY BY BONE-MARROW-DERIVED FACTORS ADMINISTERED NEONATALLY - A STUDY ON THE SPONTANEOUSLY OSTEOPOROTIC MOUSE, SAMP6

SAMP6 is a recently developed strain of osteoporotic mice, and SAMP2 i s a control for SAMP6 and has a higher peak bone mass. The bone mass o f SAMP6 was increased until 2 months of age when a lysate of cells der ived from the bone marrow of SAMP2 was injected at 1 or 4 days of age, but it was not increased when the lysate was injected at 21 days of a ge. No effect on bone mass was observed when lysates of other cells, b ovine serum albumin or heat-inactivated lysate of bone marrow-derived cells of SAMP2, were injected. The ability to increase bone mass was n ot in the supernatant but in the pellet obtained by ultracentrifugatio n (105 000 g) of the lysate of bone marrow-derived cells of SAMP2. The lysate did not change the osteoclast surface but changed the appositi onal bone formation. In conclusion, the lysate of cells derived from t he bone marrow of SAMP2 contains factors which can increase the bone m ass of SAMP6, and these factors are present in the pellet obtained by ultracentrifugation.