Effects of inflammation after spinal cord injury on the survival and immigration of bone marrow mesenchymal stem cells injected intravenously

Abstract

Objective To determine the optimal time for intravenous injection of bone marrow mesenchymal stem cells(BMSCs)by observing the effects of inflammation after spinal cord injury on the survival and immigration of BMSCs injected intravenously.Methods Forty SD rats were randomized into 1 non-injury group and 7 spinal cord injury(SCI)groups in which the injured spinal cords were harvested at 0 h, 6 h, 12 h, 24 h, 3d, 5 d, and 7 d respectively.Hematoxylin and eosin(HE)staining was used to e-valuate the histopathologic changes.Myoleperoxidase(MPO)activity was measured to study the duration of polymorphonuclear leukocyte(PMNL)infiltration in the spinal cord after injury.Another 40 SD rats were also randomly divided into 1 non-injury group and 7 transplantation groups in which intravenous injection of BMSCs was performed at 0 h, 6 h, 12 h, 24 h, 3d, 5 d, and 7 d after SCI.The survival counts and immigration distance of BMSCs in the spinal cord in all the groups were measured.Results The PMNL infiltration into the injured spinal cord and the MPO activity started from 6 h after SCI.There were a large number of infiltrating PMNL in the spinal cord and the MPO activity reached its peak value at 24 h.The infiltrating PMNL in the injured spinal cord began to decrease and the MPO activity began to weaken from 3 d.Proliferation of glial cells and formation of empty holes in the spinal cord started from 5 d.The survival counts of BMSCs were smaller but the immigration distance of BMSCs was longer in the 0 h, 6 h, 12 h, and 24 h transplantation groups.The survival counts of BMSCs were larger and the immigration distance of BMSCs was longer in the 3 d transplantation group.The survival counts of BMSCs were smaller but the immigration distance of BMSCs was shorter in the 5 d and 7 d transplantation groups.Conclusion The optimal time for intravenous injection of BMSCs may be 3 days after SCI. Key words: Spinal cord injury; Bone marrow transplantation; Cell survival; Cell immigration; Rats