The late-stage foetal liver microenvironment is essential for later sensitivity of B-lymphopoiesis to suppression by oestrogens.

B-lymphopoiesis in FL differs notably from that of adult B-lymphopoiesis in being resistant to suppression by oestrogens due to the lack of expression of oestrogen receptors in B-cell progenitors and precursors. We have transplanted middle-stage FL cells (E14.5) to adult male mice and demonstrated that B-lymphopoiesis derived from FL cells remained resistant to suppression by exogenous oestrogen for several months compared to adult BM cells. This significant difference strongly suggests that the latestage FL environment exerts an inductive action on the haematopoietic stem cells and is mandatory for later sensitivity of B-lymphopoiesis to suppression by oestrogens. The results also provide the first in vivo functional confirmation of a differential responsiveness of FL- and adult BM-derived B-lymphopoiesis to suppression by oestrogens.

Risedronate has no adverse effects on mouse haematopoiesis.

Bisphosphonates are commonly used for treatment of osteoporosis. They inhibit osteoclast activity and thus bone resorption. It was shown that they also affect some other cell types including tumour and endothelial cells. The effects of risedronate on bone marrow microenvironment were not studied yet. As endothelial cells are integral part of bone marrow microenvironment, it is important to know whether prolonged administration of bisphosphonates does not affect haematopoietic stem cells and bone marrow haematopoiesis. We fed mice two weeks with risedronate. We found no effect of risedronate treatment on bone marrow stem cells using the method of congenic bone marrow repopulation. Risedronate administration in the dose which is considered to be comparable to a dose of risedronate used for treatment of osteoporosis in women seems to be safe in terms of effects on mouse haematopoiesis.