Endoglin is required in Pax3-derived cells for embryonic blood vessel formation.

Mutations in endoglin, a TGFß/BMP coreceptor, are causal for hereditary hemorrhagic telangiectasia (HHT). Endoglin-null (Eng-/-) mouse embryos die at embryonic day (E)10.5-11.5 due to defects in angiogenesis. In part, this is due to an absence of vascular smooth muscle cell differentiation and vessel investment. Prior studies from our lab and others have shown the importance of endoglin expression in embryonic development in both endothelial cells and neural crest stem cells. These studies support the hypothesis that endoglin may play cell-autonomous roles in endothelial and vascular smooth muscle cell precursors. However, the requirement for endoglin in vascular cell precursors remains poorly defined. Our objective was to specifically delete endoglin in neural crest- and somite-derived Pax3-positive vascular precursors to understand the impact on somite progenitor cell contribution to embryonic vascular development. Pax3Cre mice were crossed with Eng+/- mice to obtain compound mutant Pax3(Cre/+);Eng+/- mice. These mice were then crossed with homozygous endoglin LoxP-mutated (Eng(LoxP/LoxP)) mice to conditionally delete the endoglin gene in specific lineages that contribute to endothelial and smooth muscle constituents of developing embryonic vessels. Pax3(Cre/+);Eng(LoxP/)(-) mice showed a variety of vascular defects at E10.5, and none of these mice survived past E12.5. Embryos analyzed at E10.5 showed malformations suggestive of misdirection of the intersomitic vessels. The dorsal aorta showed significant dilation with associated vascular smooth muscle cells exhibiting disorganization and enhanced expression of smooth muscle differentiation proteins, including smooth muscle actin. These results demonstrate a requirement for endoglin in descendants of Pax3-expressing vascular cell precursors, and thus provides new insight into the cellular basis underlying adult vascular diseases such as HHT.

Temporal changes in renal endoglin and TGF-alfa1 expression following ureteral obstruction in rats

Chronic renal disease is characterized by the accumulation of extracellular matrixproteins in the kidney and a loss of renal function. Tubulointerstitial fibrosis hasbeen reported to play an important role in the progression of chronic renal diseases.Transforming growth factor-beta1 (TGF-alpha1) is a profibrotic cytokine playing amajor contribution to fibrotic kidney disease. Endoglin is a membrane glycoproteinof the TGF-alpha1 receptor system. The aim of this work was to determine the timecourseexpression of renal type I and IV collagens, endoglin and TGF-alpha1 in a ratmodel of induced tubulointerstitial fibrosis at 1, 3, 10 and 17 days after unilateralureteral obstruction (UUO). In 17 days-ligated (L)-renal samples, a marked interstitialfibrosis was detected by Masson’s trichromic and Sirius red staining, accompaniedby an increase in type I collagen expression as shown by immunohistochemicalanalysis. Northern blot studies revealed a progressive increase in collagen alpha2(I),TGF-alpha1 and endoglin mRNA expression in L kidneys when compared with the correspondingnon-ligated (NL) kidneys from the animals subjected to left UUO. Seventeendays after UUO, significant increases in collagen alpha2(I), collagen alpha1(IV),TGF-alpha1 and endoglin mRNA levels were detected in L kidneys vs NL kidneys. Significantlyhigher levels of the protein endoglin were found in L kidneys than in NLkidneys 10 and 17 days following obstruction. A marked increase expression forendoglin and TGF-alpha1 was localized in renal interstitium by immunohistochemical studies 17 days after obstruction. In conclusion, this work reports the upregulationof endoglin coincident to that of its ligand TGF-alpha1 in the kidneys of rats with progressivetubulointerstitial fibrosis induced by UUO (AU)

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