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Analysis of Spinal Cord Regeneration of the Tail of Lizard (Mabouya Multifasciata Kuhl)
Abstract:
Tail regeneration in lizards is dependent upon the presence of spinal cord and angiogenesis. During regeneration, the lizard also regenerates the tail spinal cord, although the regenerated spinal cord is imperfect. The structure of the regenerated spinal cord, the origin of the axons in the regenerated spinal cord, and the ability of the spinal cord to stimulate angiogenesis were not known.
The main goals of this study were to (1) describe the morphologic structure of the regenerated spinal cord of lizard’s tail, (2) identify the origin of the axons in the regenerated spinal cord, and (3) observe the ability of the lizard’s tail spinal cord to promote angiogenesis. The regenerated and the original spinal cord have supraspinal and intraspinal origin and the spinal cord was able to stimulate angiogenesis.
The structure of the regenerated spinal cord was examined by light and electron microscopy. The neurons from which the axons originated in the regenerated spinal cord were detected by axonal retrograde transport techniques. Angiogenesis response was observed in vitro by implanting the spinal cord tissue of proximal to tail regenerate of all regeneration phases on the chorioallantoic membrane (CAM) of eight-day chick embryos. SDS-PAGE techniques were used to analyze protein profile of the spinal cord.
Results showed that the ependymal cells of the original spinal cord appeared to be cuboidal to low columnar, without the basal process. The ependymal cells of the regenerated spinal cord were high columnar with the ependymal processes extending from the basal portion of the cells toward the piameter. Numerous mitochondria, Golgi complex, and free ribosome were present in the cytoplasm of ependymal cells of either the original or regenerated spinal cord, and limited rough endoplasmic reticulum were shown close to the nucleus. The majority of the regenerated axons were non-myelinated and were located between the basal processes of the adjacent ependymal cells. This study demonstrated that only a small number of supraspinal neurons extend axons into the regenerated spinal cord. However, the majority of the axons in the regenerated spinal cord were local spinal (intraspinal) origin. As the spinal cords were implanted on the CAM, new blood vessels were converging toward the implant. The most active of angiogenesis occurred in the CAM implanted with spinal cords proximal to the regeneration of wound healing and differentiation phase (Score 2+); and these spinal cords had similar protein profiles. However, a protein profile of 39 kD and 43 kD of spinal cord proximal to the regeneration of wound healing and differentiation phase resulted to thicker band than those found in other phases of regeneration.
It was concluded that the regenerated and the original spinal cords have different structures. The axons in the regenerated spinal cord have intraspinal origin. The spinal cord proximal to the regeneration of wound healing and differentiation phase was able to stimulate angiogenesis and they have higher concentration of protein (39 kD and 43 kD) than the same protein of spinal cord proximal to the regenerate of other regeneration phases. This study suggested that the protein of 39 kD and 43 kD in the lizard spinal cord represented angiogenesis factor, which plays role in the regeneration processes.