 Finally, osteoclast inhibition by the bisphosphonate alendronate has correlated with decreased HSCs and bone marrow engraftment.Taken together, these results suggest that the high calcium ion concentration found in the endosteal niche due to osteoclast activity acts as a homing signal to HSCs for engraftment into the bone marrow via the CaSR.Thirdly, the shearing forces experienced by HSCs from circulating cells has been suggested to play a role in hematopoietic activation.