Re-closure Capacity of Surgically Induced Open Neural Tube Defect in Chick Embryos

ABSTRACT

OBJECTIVE: To determine whether there is a re-closure capacity of the open neural tube defect(ONTD) and to characterize its re-closing process, the morphological changes and the re-closure rate of a surgically induced ONTD are examined chronologically in early chick embryos. METHODS: Embryos of Hamburger and Hamilton stage 18-19 were used. The posterior roof of the central canal in the closed neural tube was incised longitudinally at the wing bud level. The incision was 3 somites long, which was equivalent to approximately 0.8mm. Following surgery, the embryos were re-incubated in ovo for three or five days. The area of the incision was observed with a stereomicroscope. Some of them were examined histologically with the transverse section of the wing bud area. They were divided into two groups(POD 3 and POD 5) according to the re-incubation period at the time of sacrifice and then into two subgroups(re-closure and defect group) according to the presence of ONTD at the operative site. RESULTS: The results showed : 1) Re-closure of ONTD occurred in 58%(23/40) of POD 3 embryos and 46%(22/48) of POD 5 embryos. The difference of re-closure was not statistically significant. 2) Most of the re-closed neural tubes revealed no significant difference from the controls in the histological examination. 3) In POD 3 and 5 groups, there was a tendency of zipper-like fusion in both re-closure and defect groups. CONCLUSION: The results of study showed that the neural tube of the early chick embryo has a re-closure capacity after being surgically reopened. Seemingly, re-closure occurs mainly before POD 3 and progresses from the ventral to the dorsal part of the neural tube. The mechanism of re-closure needs to be investigated further.