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Fig. 8. SMCs in the adult descending aorta originate from the somites.
(A-F) Descending aorta from adult Meox1-cre/R26 reporter mice
was stained for lacZ activity at different anterior-posterior levels
(levels are indicated in A). SMCs stained positive for the reporter gene at
all investigated levels, also in the posterior part of the aorta. (G)
Double staining against lacZ and Acta2 confirmed reporter gene
expression in SMCs. (H-M) SMCs in the major branches of the descending
aorta were investigated in Meox1-cre/R26 reporter mice at P2 to
determine the distal borders of somite contribution. Whole-mount staining of
internal organs with attached aorta showed lack of reporter expression in the
coeliac artery (arrowheads in H) and superior mesenteric artery (arrows in H
and I). The renal arteries were homogenously stained (arrows in J). The aorta
was displaced to expose the branch points. X-gal staining of cryosections
confirmed lack of somite contribution to the coeliac and superior mesenteric
arteries (K,L). The transition from lacZ-positive to negative SMCs
occurred at the branch points (thin arrows in K and L), but not in a strict
manner. Asterisk in L indicates somite-derived SMCs that extended into the
superior mesenteric artery (sm). Arrowheads in K and L indicate the walls of
the coeliac artery and superior mesenteric artery, respectively. The renal
artery was entirely occupied by somite-derived SMCs (M). Boxed area in M shows
renal arterial wall at higher magnification. Arrows in M indicate
lacZ-positive SMCs, arrowheads indicate lacZ-negative
endothelial cells. al, aortic lumen; ao, aorta; ca, coeliac artery; dm, dorsal
mesentery; ia, iliac artery; in, intestines; m, tunica media; ra, renal
artery; sm, superior mesenteric artery; asterisks, endogenous X-gal activity.
Scale bars: 25 µm in B-G; 50 µm in K-M.
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