Age-Dependent Histomorphometrical Values of the Sciatic Nerve Regeneration in Rats after Cutting and Microsurgical Suturing

The effect of ageing on the morphofunctional features of nerves and the process of their posttraumatic regeneration has been studied in details. However, it is not known, whether there are differences of the neuroregeneration potential in the young, adult and mature experimental animals.The aim of the study was to evaluate histomorphometrical parameters of the rat sciatic nerve regeneration after cutting and microsurgical suturing depending on their age.Materials and Methods. The study included 15 white laboratory Wistar rats aged 5–6 (young), 8–10 (adult) and 12 months (mature). The sciatic nerve was transected at the level of the middle third of the thigh with microsurgical scissors and sutured with six epi-perineural stitches in the animals. In 4 months the animals were euthanized. Sections of sciatic nerves distal to the levels of sutures were put into araldite, semi-thin slices (0.5–1.0 mkm) were obtained for histomorphometric analysis. Thirteen intact animals were selected as control. Statistical processing was performed using nonparametric methods.Results. The numerical density of endoneural vessels in nerves of operated rats was higher than that in the intact ones, but in mature animals it was significantly lower than in young and adult ones (p<0.001). The numerical density of endoneural cells nuclei in young experimental animals did not differ from that of the intact ones, but in animals from the adult and mature groups it was more than four times higher than in animals from the young group (p<0.001). The numerical density of regenerating myelinated nerve fibers in animals of the young and adult groups did not differ from that of the intact nerve, in animals of the mature group it increased in 2.5 times (p<0.001). The numerical density of degenerating myelinated fibers in the operated animals of experimental groups was higher than in the intact group (two times, six times and 11 times higher, respectively). The diameter distribution of the regenerating myelinated fibers in animals of all groups differed from that of the intact control animals.Conclusions. The data obtained demonstrate a significant decrease in the regenerative potential of Schwann cells and neurons in adult and mature animals compared with the young ones.

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STEREOLOGY OF NEURONAL CONNECTIONS (MYELINATED FIBERS OF WHITE MATTER AND SYNAPSES OF NEOCORTEX) IN HUMAN BRAIN

Image Analysis & Stereology ◽

10.5566/ias.v22.p171-182 ◽

2011 ◽

Vol 22 (1) ◽

pp. 171 ◽

Cited By ~ 8

Author(s):

Yong Tang ◽

Jens R Nyengaard ◽

Bente Pakkenberg ◽

Hans Jørgen G Gundersen

Keyword(s):

White Matter ◽

Volume Density ◽

Nerve Fibers ◽

Diameter Distribution ◽

Numerical Density ◽

Myelinated Nerve ◽

Myelinated Nerve Fibers ◽

Myelinated Fibers ◽

Total Length ◽

Human Autopsy

Unbiased stereological sampling and counting techniques for estimating the total length, total volume and diameter distribution of myelinated nerve fibers in white matter and the total number of synapses in neocortex of human autopsy brains were described. Uniform random sampling of tissues from entire hemisphere was performed. The total volume and total length of myelinated fibers in white matter were estimated from the product of the volume of white matter obtained with the Cavalieri principle and the volume density and length density of myelinated fibers in white matter, respectively. The volume density of myelinated nerve fibers in white a matter was estimated with a point counting method. The length density of myelinated fibers in white matter was estimated from the isotropic, uniform random sections that were ensured by the sector. The diameter of myelinated fibers was derived by measuring the profile diameterperpendicular to its longest axis. The ethanolic phosphotungstic acid staining technique was modified for staining synapses in human autopsy brains. The total number of synapses in each neocortical region was estimated as the product of the volume of each neocortical region and the numerical density of synapses in each region. The numerical density of synapses in each neocortical region was obtained with the disector at the electron microscopical level. The presented methods will be useful for quantitative studies of the changes of myelinated nerve fibers and synapses in various distinct regions of the central nervous system due to development, aging and diseases.

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