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Fig. 4. Clonal analysis of the vascular endothelial lineage and culture of
purified endothelial cells. (A) SNV-based, non-replicative
retroviral vectors. 5' and 3' long terminal repeats (LTR) are
shown as open boxes. An arrow indicates the direction of transcription from
the promoter in the left-hand LTR. Bold lines between LTRs denote SNV
sequences. Encapsidation sequences required for the packaging of virions are
indicated as
. Provirus sizes and putative translations of the reporter
genes are indicated below the viral structure. (B) Six-day-old embryo
inoculated at E4 with a mix of lacZ- and PLAP-carrying vectors. Double
histochemistry to reveal the reporter genes and double immunofluorescence with
anti-MEP21 (orange) and anti-
SMA (blue) mAbs. Cross-section through the
aorta. lacZ (black arrowhead) or PLAP (white arrowhead) infections
are restricted to the endothelium. (Inset) Two infected cells expressing PLAP
framed in B. Scale bars: 50 µm and 20 µm in inset. (C) FACS
analysis after AcLDL-DiI and CD45 immunostaining. The frame points to the
AcLDL-DiI+/CD45- cell population, i.e. the endothelial
cells, selected for culture. (D) Cultures of purified endothelial cells
without growth factors (left column), supplemented with VEGF (middle column)
or TGFß (right column) at two different time points. Upper line, second
day of culture; lower line, fifth day of culture. Triple staining with MEP21
(red)/
SMA (green)/DAPI (blue). Two days of culture: purified
endothelial cells uniformly express MEP21, although cell sizes in the
different culture conditions may vary. Five days of culture: MEP21 expression
has decreased and
SMA becomes expressed. Disappearance of MEP21 is
total in the control medium without growth factors. The VEGF supplementation
produces numerous cells co-expressing MEP21 and
SMA. With TGFß
supplementation, most of the cells have lost MEP21 expression. Some cells,
however, retain a MEP21 signal and thus express both markers. Scale bar: 25
µm.