Inhibition of osteoclast function reduces hematopoietic stem cell numbers in vivo

Stefania Lymperi, Adel Ersek, Francesca Ferraro, Francesco Dazzi, Nicole J. Horwood

Research output: Contribution to journalArticlepeer-review

107 Scopus citations


Osteoblasts play a crucial role in the hematopoietic stem cell (HSC) niche; however, an overall increase in their number does not necessarily promote hematopoiesis. Because the activity of osteoblasts and osteoclasts is coordinately regulated, we hypothesized that active bone-resorbing osteoclasts would participate in HSC niche maintenance. Mice treated with bisphosphonates exhibited a decrease in proportion and absolute number of Lin -cKit+Sca1+ Flk2- (LKS Flk2 -) and long-term culture-initiating cells in bone marrow (BM). In competitive transplantation assays, the engraftment of treated BM cells was inferior to that of controls, confirming a decrease in HSC numbers. Accordingly, bisphosphonates abolished the HSC increment produced by parathyroid hormone. In contrast, the number of colony-forming-unit cells in BM was increased. Because a larger fraction of LKS in the BM of treated mice was found in the S/M phase of the cell cycle, osteoclast impairment makes a proportion of HSCs enter the cell cycle and differentiate. To prove that HSC impairment was a consequence of niche manipulation, a group of mice was treated with bisphosphonates and then subjected to BM transplantation from untreated donors. Treated recipient mice experienced a delayed hematopoietic recovery compared with untreated controls. Our findings demonstrate that osteoclast function is fundamental in the HSC niche.

Original languageEnglish
Pages (from-to)1540-1549
Number of pages10
Issue number5
StatePublished - Feb 3 2011


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