Notochord anomalies in the adriamycin rat model: A morphologic and molecular basis for the VACTERL association.
OBJECTIVE
The Adriamycin rat model (ARM) is a reliable model of the VACTERL association. The notochord is structurally abnormal in the region of the foregut, midgut, and hindgut in the ARM. The authors hypothesised that notochord anomalies allow ectopic expression of molecular signals in the developing embryo and thus lead to VACTERL malformations. This study was designed to investigate this hypothesis.


METHODS
Adriamycin (1.75 mg/kg) was administered intraperitoneally to pregnant rats on days 7, 8, and 9 of gestation. Control animals were given saline. Embryos were recovered on gestational days 10.5 to 14 at (1/2)-day intervals and at full term. The first group of embryos were embedded in resin, and sagittal sections stained with Toluidine blue were studied for morphologic abnormalities. The second group of embryos were examined using in situ hybridization for the expression of Sonic Hedgehog (Shh), a patterning gene implicated in the etiology of the VACTERL association.


RESULTS
Twenty-seven of the 28 (96.4%) full-term embryos showed VACTERL anomalies. Forty-five of the 50 (90%) experimental embryos (gestational days 10.5 to 14) showed notochord abnormalities. Abnormal ventral branches from the notochord toward the gut were a commonly observed abnormality. These were seen to impinge on the developing foregut, midgut, dorsal aorta, and kidney. In situ hybridization for Shh showed that these branches from the notochord expressed Shh in 66.6% of experimental embryos. This abnormal Shh expression was not seen in the control embryos.


CONCLUSIONS
Adriamycin diffusely induces altered notochord morphology in the rat embryo. The abnormal notochord morphology may allow ectopic expression of Sonic Hedgehog, and, thus, contribute to the malformations found in the VACTERL association.
Gillick
J
J
Children's Research Centre, Our Lady's Hospital for Sick Children and University College Dublin, Dublin, Ireland.
Mooney
E
E
Giles
S
S
Bannigan
J
J
Puri
P
P
D000014:Abnormalities, Drug-Induced / Q000209:etiology / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000015:Abnormalities, Multiple / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D004195:Disease Models, Animal; D004317:Doxorubicin / Q000633:toxicity*; D004933:Esophageal Atresia / Q000139:chemically induced / Q000196:embryology / Q000235:genetics*; D005260:Female; D005326:Fetal Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D005865:Gestational Age; D053823:Hedgehog Proteins; D007422:Intestines / Q000196:embryology; D009024:Morphogenesis / Q000187:drug effects; D009672:Notochord / Q000002:abnormalities* / Q000187:drug effects; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D014138:Tracheoesophageal Fistula / Q000139:chemically induced / Q000196:embryology / Q000235:genetics*; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
D005326:Fetal Proteins; D053823:Hedgehog Proteins; C465570:Shh protein, mouse; D015534:Trans-Activators; D004317:Doxorubicin