Unlike the adult mammalian central nervous system (CNS) that has limited capacity for regeneration, the immature mammalian CNS shows a unique ability to successfully regenerate after injury. Although regeneration studies have provided significant insight into the basic molecular mechanisms underlying CNS regeneration, the key differences between the organisms that can and cannot regenerate are still unknown. Monodelphis domestica, commonly known as the gray short-tailed opossum, is a unique preparation that offers an exceptional opportunity to study mammalian CNS regeneration, without a need for intrauterine surgery. Opossums are marsupials born at highly immature developmental stage, with the possibility to regenerate spinal cord after injury in the first two weeks of their lives. The aim of this thesis was to prepare and characterize two different preparations: CNS primary cultures and fresh-fixed spinal cord tissue from the opossums of different age, which can and cannot regenerate after injury. Characterization was performed using immunofluorescence to reveal differences in the cellular content and expression of markers related to regeneration with a focus on stem cells. Also, we tested two different plating mediums to examine the impact of the medium composition on cell growth and differentiation. Firstly, we confirmed that the expression of TUJ1, a neuron-specific marker and the stem/glial progenitor SOX9 is mutually exclusive. Secondly, we confirmed that SOX2 is a powerful tool for characterizing stem/progenitor cells through the CNS. Thirdly, we showed that the medium composition indeed affects cell growth and differentiation. Finally, in spinal cord intact tissue, we confirmed the localization of cells that co-express SOX2 and SOX9. In younger tissue, these cells are present along the central canal, while in older animal cells are scattered. The results of this study will help to develop the tools to study and characterize CNS stem cells that could be used in novel strategies to cure spinal cord injury.