Blood-forming stem cells may not enter this world alone. They may have birthing partners -- cells that live in bone marrow -- with whom they interact. The research, reported in two papers in Nature (Vol. 425, No. 6960, 23 October 2003, pp. 836-841 and 841-846), highlights the crucial relationship between stem cells and their local habitat. The research may yield practical methods for manipulating stem cells and provide a model for the impact of local environment on cell physiology.
As the number of bone-forming osteoblast cells increases, so too does the number of blood-forming haematopoietic stem cells (HSCs), say the researchers. The former are known to secrete the calcified bone matrix, but so far their relationship with stem cells has been unclear.
Linheng Li and colleagues have shown that mice lacking a key cellular receptor develop bone abnormalities. Closer inspection has revealed that the animals have twice the normal number of HSCs and osteoblasts — cell types that are physically close to each other.
In a second paper, D. T. Scadden and colleagues describe a similar effect in a different mutant mouse. They show how cultured bone marrow cells from these animals are better able to support HSCs than are similar cells taken from normal animals.
"The authors demonstrate that osteoblasts have a crucial role in HSC regulation," say Ihor Lemischka and Kateri A. Moore in an accompanying News and Views article. The study shows how alterations in the local environment can affect HSC numbers.
Stowers Institute for Medical Research
Kansas City, MO, USA
Tel: +1 816 926 4081
David T. Scadden
Harvard Medical School
Boston, MA, USA
Tel: +1 617 726 5615
Princeton, NJ, USA
Tel: +1 609 258 2838
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