[Transferrin receptor expression of human mesenchymal stem cells and in vitro tracking by autoradiography after transplantation in spinal cord].
OBJECTIVE
To determine transferrin receptor (TfR) expression of human mesenchymal stem cells (MSCs) in vitro and after transplantation in rabbit spinal cord,and to detect implanted MSCs by in vitro autoradiography.


METHODS
Human mesenchymal stem cells (hMSCs) were isolated from fetal blood. Flow cytometry assay, immuno-fluorescent staining and receptor binding assay were used to determine TfR expression of hMSCs. Radioiodinated transferrin saturated with iron [(125)I-Tf(Fe)(2)] was used as tracer. The hMSCs transplanted in rabbit spinal cord was tracked by in vitro autoradiography. Diffusion of (125)I-Tf(Fe)(2) in spinal cord was examined with autoradiography.


RESULTS
TfR expression of MSCs was demonstrated by flow cytometry assay, immuno-fluorescent staining and receptor binding assay in vitro. (125)I-Tf(Fe)(2) bound to hMSCs with a equilibrium dissociation constant (KD) of (0.98+/-0.12) nmol/L and a maximal density of binding sites (B(max)) of (107 702+/-6 226) sites per cell. Immuno-fluorescent staining showed that TfRs were expressed on hMSCs on the 2nd day but not be expressed on the 10th day post transplantation. Autoradiography showed distinct accumulation of (125)I-Tf(Fe)(2) but not (125)I-HSA at hMSCs implantation sites of spinal cord sections on the 2nd day post transplantation. (125)I-Tf(Fe)(2) had diffused into spinal cord 16 hours after incubation.


CONCLUSIONS
Implanted hMSCs could be detected by in vitro autoradiography with (125)I-Tf(Fe)(2) on the 2nd day after being transplanted in spinal cord. To track implanted hMSCs with radionuclide imaging techniques in vivo, TfR was a suitable target for imaging and radioiodinated Tf(Fe)(2) was a feasible tracer.
Bai
Jin-zhu
JZ
Department of Orthopedics, Peking University Third Hospital, Beijing 100083, China.
Ding
Wei-min
WM
Liu
Zhong-jun
ZJ
Yu
Min-jun
MJ
Tian
Jia-he
JH
Wang
Fan
F
Du
Jin
J
Zhang
Xiao-yan
XY
Li
Ling-song
LS
Shen
Li
L
D000818:Animals; D001345:Autoradiography; D002454:Cell Differentiation; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000737:chemistry*; D011817:Rabbits; D011990:Receptors, Transferrin / Q000032:analysis*
D007457:Iodine Radioisotopes; D011990:Receptors, Transferrin