Anatomic localization of stem cell niches and reversibility of the microenvironmental changes after transplantation. (A) Sections of a metaphysis obtained 48 hours (left and center) or 10 days (right) after TBI and donor (GFP⁺) BM transplantation (BMT), stained with hematoxylin and eosin (top) or immunostained for N-cadherin (red; bottom). An increased number of osteoblasts () and the persistence of megakaryocytes in their proximity (; top left panel) are apparent at 48 hours after BMT. The engrafted cells appear as discrete clusters of small round cells close to the endosteum (center panels are the insets indicated in left panels). Scale bar (left and right panels) represents 50 μm; scale bar (center panels) represents 10 μm. (B) Sections obtained 48 hours (left) or 10 days (center) after donor (GFP⁺) BMT immunostained for GFP. The previously observed cells appear as donor derived clusters (≤ 6/femur) located in the metaphysis and epiphysis of recipients. At 10 days after transplantation, the marrow cellularity increased (center), megakaryocytes (⇑) were frequently found close to vessels (V) and bone lining cells returned to a single tier (). Isotype control is shown for comparison (right). Scale bar: 50 μm.