Background: Although the principal adverse reactions of Cyclosporine-A (CSA) are renal, hepatic dysfunction, and neurotoxicity, it can rarely cause bone marrow
depression. But, it was recently reported that CSA can elicit leukopenia in the recipient of renal transplantation. Thus the authors have studied the effect of CSA on the ultrastructural changes of bone marrow cells of mouse.
Method : Totals of 60 healthy male ICR strain mice were used as experimental animals, of which 50 mice were treated with 50mg of CSA per kg of body weight intraperitoneally once a day for 2 weeks, and the another 10 mice were treated with normal saline as a control group. At 12, 24, 48 hours and 5 and 7 days after the last
administration of CSA or normal saline, bone marrow cells were examined with electron microscope.
Results: In the eosinophilic myelocytes, metamyelocytes, and segmented eosinophils of 12, 24, and 48 hours after the last administration of CSA, the cisternal of rough
endoplasmic reticulum were dilated or fragmented and decreased in number. The number and electron density of mitochondria were decreased, and occasionally mitochondrial
cristae were disappeared. The crystalloid core in specific granules was disorganized into irregular and dense particles, and some granules were destroyed. But these changes were eventually back to normal in bone marrow 5 and 7 days after the last administration of CSA.
Conclusion: We suggest that CSA can cause transient alteration of bone marrow function, because it can change the ultrastructures of bone marrow cells.

Keywords: Cyclosporine-A, Bone marrow,