Purpose. Postneonatal neovascularization is thought to result exclusively f
rom the proliferation, migration, and remodeling of fully differentiated en
dothelial cells (ECs). Recently, it has been reported that bone marrow cont
ains cells which can differentiate into ECs and contribute to neoangiogenes
is in adult species. In this study, we tried to establish conditionally imm
ortalized endothelial cell lines (TR-BME) derived from rat bone marrow.
Methods. Mononuclear cells were isolated and differentiated into ECs at 37
degreesC from the bone marrow of a transgenic rat harboring temperature-sen
sitive SV40 large T-antigen (ts T-Ag) gene. Then, the cells were transferre
d and incubated at 33 degreesC, a permissive temperature for ts T-Ag. Expre
ssion of vascular endothelial growth factor (VEGF) receptor (VEGFR)-1, 2, T
ie-1, 2 and von Willebrand factor (VWF) were assayed by reverse transcripta
se-mediated polymerase chain reaction (RT-PCR).
Results. We have established three cell lines incorporating 1,1'-dioctadecy
l-3,3,3',3-tetramethylindo-carbocyanine perchlorate (DiI-Ac-LDL) with a spi
ndle shape. One of these, clone 2, strongly ex pressed VEGFR-2, and weakly
expressed VEGFR-1 and VWF. In contrast, clone 8 showed strong expression of
Tie-1, 2, and VWF, and weak expression of VEGFR-1,2. All markers were expr
essed strongly in clone 3.
Conclusions. These data confirm that the above three TR-BME cells are novel
ECs derived from bone marrow progenitors.