CsA stimulates megakaryopoiesis in vivo. (A) Bone marrow cytospins from wild-type mice treated with the calcineurin inhibitor CsA or vehicle for 6 weeks were immunostained for NFATc1 (red) and Dapi (blue) to examine steady-state NFATc1 subcellular localization. Arrows indicate megakaryocytes. Bar represents 50 μM. (B) Representative histogram of CD41-positive bone marrow and spleen megakaryocytes by flow cytometry from wild-type mice treated for 6 weeks with either vehicle alone or CsA. (C) Hematoxylin and eosin images of bone marrow and spleen sections from CsA-treated mice demonstrate increased numbers of megakaryocytes as compared with vehicle-treated mice as evidenced by hematoxylin and eosin. Arrows denote megakaryocytes. Bar represents 25 μM. (D) Quantification of megakaryocytes in bone marrow (BM) and spleen sections counted in 5 low power fields. Values are mean ± S.D. **P < .03; *P < .05. (E) Circulating platelet counts after vehicle or CsA treatment of wild-type mice for 6 weeks; n = 10; *P < .05.