Transplantation of human embryonal nervous tissue into the spinal cord of adult rats

Abstract

human embryos, containing an anlage of the neocortex can be used as the initial material for transplantation [3, 4]. It has been placed into the cerebral cortex of adult rats, and the taking of the graft has been observed [5]. The time course of the proliferative processes and the differentiation of the cellular elements have been studied in this model, and it has been demonslrated that the prolonged existence, for six months and longer, of the trap. splant without signs of a cellular immune reaction is possible in a number of instances. The purpose of the present investigation was the elucidation of the characteristics of the development of a transplant of human embryonal nervous tissue in the rat spinal cord. Taking the great potentials for growth of segments of the telencephalic vesicles of human embryos, and data regarding the fact that they take well in homografts of the spinal cord of mammals [3, 4, 8, 7], into account, this division of the embryonal brain was specifically selected as the initial material for transplantation. Material and Methods. The investigation was carried out on 68 adult Wistar rats, weighing 200-250 g. Laminectomy of the VI thoracic vertebra was carried out in the animals under anesthesia (Calypsol in a dose of 200 mg/kg in combination with the inhalation of ether vapors). With monitoring by means of an operative microscope, the dura mater was opened, and a segment of donor brain measuring 2 mm 3 was introduced by a means of a glass cannula with an internal diameter of 0.5 mm into the spinal cord. Segments of the wall of the telencephalic vesicle of human embryos at the 8-10 week period of development, obtained after artificial interruption of pregnancy, were transplanted. The initial material for the transplantation was kept for several hours in Hanks' solution at t ~ = 4~ After the operation the animals were maintained in the usual vivarium conditions. Morphological investigation using light and electron microscopic methods was carried out 2, 3, 4, 8, and 12 weeks later. For light microscopy the material was fixed in Bouin's fluid. Paraffin sections, 5-7 Inn were stained with hematoxylin-eosin and toluidine blue after Nissl. For the electron microscopy, fixation of the brain was carried Out by perfusion of a 2.5% solution of glutaraldehyde in a 0.01 M phosphate buffer at pH 7.3-7.4, with subsequent treatment with a 2% solution of OsO4 in a 0.05 M cacodylate buffer, The material dehydrated in a series of alcohols of increasing concentration and in propylene oxide, and mounted in Epon. After the semithin sections were studied, collimated trimming of the blocks was carried out. The ultrathin sections, 50 nm in thickness, were obtained on an LKB ultratome, and studied under a JEM 100-B electron microscope. Results and Discussion. The wall of the telencephalic vesicle of the donor embryo at the 8-10 week period of development consists of cells of various degrees of maturity. Undifferentiated neuroepithelial cells, capable of mitotic division, are located in the ventricular zone. They are the forerunners of both nerve and glial cells. These cells, which are capable of migration, have an elongated form when stained with hematoxylin-eosin. A large number of mitotically dividing cells are observed particularly in the ventricular zone. The anlage of the ncocortex, the primary gray matter of the cortex, properly appears in embryogenesis from the eighth week of intrauterine development as a result of the migration of cells from the ventricular zone [1, 6]. It consists of cells of a high degree of maturity. As the formation of the primary gray matter of the cortex and the increase in the number of cells