One-year follow-up after bone marrow stromal cell treatment in middle-aged female rats with stroke

Background and Purpose - We sought to evaluate the long-term effects of bone marrow stromal cell (BMSC) treatment on retired breeder rats with stroke. Methods - Female retired breeder rats were subjected to 2-hour middle cerebral artery occlusion (MCAO) followed by an injection of 2 X 10(6) male BMSCs (n=8) or phosphate-buffered saline (n=11) into the ipsilateral internal carotid artery at 1 day after stroke. The rats were humanely killed 1 year later. Functional tests, in situ hybridization, and histochemical and immunohistochemical staining were performed. Results - Significant recovery of neurological deficits was found in BMSC-treated rats beginning 2 weeks after cell injection compared with control animals. The beneficial effects of cell transplantation persisted for at least 1 year (P < 0.01). In situ hybridization for the Y chromosome showed that donor cells survived in the brains of recipient rats, among which 22.3 +/- 1.95% of cells expressed the astrocyte marker glial fibrillary acidic protein, 16.8 +/- 2.13% expressed the neuronal marker microtubule-associated protein 2, and 5.5 +/- 0.42% and < 1% of cells colocalized with the microglial marker IB4 and the endothelial cell marker von Willebrand factor, respectively. Only very few BMSCs, however, were found in peripheral organs such as the heart, lung, liver, spleen, and kidney in recipient rats. BMSCs significantly reduced axonal loss (P < 0.01), the thickness of the lesion scar wall (P < 0.01), and the number of Nogo-A-positive cells (P < 0.05) along the scar border; meanwhile, synaptophysin expression (P < 0.05) was significantly increased in BMSC-treated ischemic brains compared with control untreated brains. Conclusions - The beneficial effects of BMSCs on ischemic brain tissue persisted for at least 1 year. Most surviving BMSCs were present in the ischemic brain, but very few were found in other organs. The long-term improvement in functional outcome may be related to the structural and molecular changes induced by BMSCs.