The transplantation of primary Schwann cells (SC) has been shown to improve nerve regeneration. However, to monitor the survival of transplanted cells within the host, a stable labelling method is required. The in vitro characteristics of green fluorescent protein labelled SC (GFP SC) and their effects in an in vivo peripheral nerve injury model were investigated.   The GFP-SC were readily visualised ex vivo and stimulated significantly better axonal regeneration compared to controls. Clinical use of autologous SC for the treatment of nerve injuries is of limited use due to difficulty in obtaining clinically useful numbers. However, bone marrow mesenchymal stem cells (MSC) can trans-differentiate into SC like cells (dMSC). The in vitro and in vivo differentiation of MSC was explored, and the study extended to include the easily-accessible adipose stem cells (ASC).  In vitro, glial growth factor stimulated MSC express S100, a SC marker, and its expression is maintained following in vivo transplantation.  Similarly, untreated MSC transplanted in vivo also expressed S100, which indicates glial differentiation in response to local cytokines and growth factors. Using an in vitro model, comprising dMSC or dASC co-cultured with adult dorsal root ganglia (DRG) neurons, the capacity of the dMSC and SC like differentiated ASC (dASC) to promote axon myelination was verified: both cell types expressed transcripts for protein zero, peripheral myelin protein-22 and myelin basic protein. The potential of stem cells in nerve repair may be limited by innate cellular senescence or donor age affecting cell functionality thus it was essential to determine the effects of donor age on morphology and functionality of stem cells.  The proliferation rates, expression of senescence markers (p38 and p53) and the stimulation of neurite outgrowth from DRG neurons by stem cells isolated from neonatal, young or old rats were very similar. However, the distribution and ultrastructure of mitochondria in dMSC and dASC from young and old rats were quite different, and seem to indicate physiological senescence of the aged cells.  Given the wide-ranging influence of Notch signalling in cell differentiation, including the neural crest to a glial cell type switch, and self-renewal in mammals, its role in the differentiation of stem cells to SC was investigated. The mRNA for notch-1 and -2 receptors were expressed in the dASC, blockage of notch signaling did not affect the neurotrophic and myelination potential of dASC.  In conclusion, these findings show that GFP labelling has no deleterious effect on SC survival and function. MSC and ASC differentiated into glial-type cells acquire SC morphology, and express characteristic SC markers, and the differentiation process was independent of the Notch signaling pathway. Also, following transplantation into a nerve gap injury dMSC improve regeneration. This study established that following co-culture with DRG neurons, dMSC and dASC were able to express peripheral myelin proteins.  Also, the functional bioactivity of these cells is independent of the donor animal age. Finally, although the glial lineage differentiated aged cells characterized in this study expressed markers typical of senescence they retained the potential to support axon regeneration.

Des cellules souches dérivées des crêtes neurales ont été trouvées dans divers tissus adultes comme le ganglion de la racine dorsale (GRD). Ce projet de thèse vise à identifier et caractériser la cellule souche de ce tissu. Premièrement, nous avons étudié le potentiel souche de l’ensemble des cellules du GRD. In vitro, certaines sont capables de proliférer pour former des sphères multipotentes qui génèrent des neurones, des glies et des myofibroblastes. In vivo, selon le contexte dans lequel les cellules issues des sphères sont transplantées, elles génèreront différent types cellulaires. Dans le funiculus dorsal démyélinisé de la souris Nude, elles se différencient en cellule de Schwann alors que dans un cerveau de souris nouveau-né Shiverer, elles produisent des péricytes qui s’intègrent aux capillaires sanguins. Bien que le GRD possède une population cellulaire au potentiel souche, son identité et son rôle restent à découvrir. Afin d’identifier cette cellule, nous avons combiné plusieurs techniques et souris transgéniques pour éliminer les diverses cellules candidates. Nous avons découvert plusieurs cellules avec une plasticité intéressante. Deux progéniteurs unipotents ayant la morphologie et la signature moléculaire de péricyte et de fibroblaste de l’endonèvre ont été trouvés dans le nerf sciatique et le GRD adulte. Enfin la cellule souche du GRD correspond de par sa morphologie à une cellule satellite (SGC). Elle prolifère et est bi-potente in vitro. Elle génère, in vivo, des SGC mais également des neurones en condition pathologique. Mieux comprendre ses mécanismes de régulations pourrait ouvrir la voie à de nouvelles stratégies thérapeutiques pour les maladies du SNP. / Neural crest-derived stem cells have been identified in various adult tissues including the dorsal root ganglia (DRG). This thesis project aims to identify and characterize the putative adult DRG stem cell. First, we studied the stemness potential of global DRG cell populations. In vitro, within the adult DRG, some cells were able to form multipotent spheres that gave rise to neurons, glia and myofibroblasts. The graft of the DRG cell forming spheres proved their differentiation plasticity in vivo. Depending upon their graft environment; they generate different cell types. In the demyelinating dorsal funiculus of adult Nude mice, they formed myelinating Schwann cells while in the brain of new born Shiverer mice, they produced pericytes integrated within capillaries. Although, the DRG cells seemed to have an interesting stemness potential, their identity and their physiopathological role remain unknown. In order to characterize this stem cell and study its fate within the DRG, we combined several technics with transgenic mouse lines to exclude the diverse DRG candidate cells. We discovered different cells with interesting plasticity. Two types of unipotent progenitors that have the morphology and molecular characteristics of pericyte and endoneurial fibroblast in the adult sciatic nerve and DRG. But most of all, we found that the DRG stem cell has the phenotype of the satellite glial cell (SGC). They proliferate and are bipotente in vitro. In vivo these stem cells generate SGC under normal condition and produce glia more neurons when necessary in pathological condition. Understanding these regulation mechanisms could open the way to new therapeutic strategies for PNS diseases.

Stem cell research offers hope to many people suffering from incurable diseases such as Alzheimer's disease, diabetes, heart disease and spinal back injuries. However this poses a moral dilemma because embryos are destroyed during embryonic stem cell research. To determine whether embryonic stem cell research is morally justifiable, two views in respect of a human being were considered: i. a human has a dualistic nature in which his body and soul are two separate entities or ii. his body and soul forms a unity which can not be separated. If a human has a dualistic nature, it means that the embryo is not a human, it does not have a soul because the soul is added later to form a human. The implication of this is that it will be morally justifiable to kill an embryo during embryonic stem cell research. However if body and soul forms a unity which can not be separated, the embryo is a human which is already developing into a full grown human with several stages of development. It will thus not be morally justifiable to kill an embryo as this will violate the sixth commandment, i.e. “Thou shalt not kill.” To determine whether a human’s body and soul is an inseparable unity or whether they are two separate entities, the Pauline letters' view on the human being was investigated. The research method employed was to do a comparative literary study to highlight the different aspects of stem cell research and then exegesis was done in respect of body (σoμα / sōma); soul (ψυχὴ / psychē) and spirit (πνεῦμα / pneuma) in the Pauline letters according to the grammatical-historical method. An electronic Bible Concordance was used to determine the texts in which the above concepts appear. A semantic word analysis was also done to analyse these concepts. Then authoritative commentaries were used to check the findings. The analysis indicated that Paul refers to a human as unity in which body and soul can not be separated. The implication of this finding is that embryonic stem cell research should be dismissed because it will result in the destruction of embryos. Humans will thus be killed in violation of the sixth commandment. On the other hand adult stem cell research should be encouraged because it has the potential to cure diseases which has up to now been incurable. / Thesis (MTh (Ethics))--North-West University, Potchefstroom Campus, 2013.

Stem cell research offers hope to many people suffering from incurable diseases such as Alzheimer's disease, diabetes, heart disease and spinal back injuries. However this poses a moral dilemma because embryos are destroyed during embryonic stem cell research. To determine whether embryonic stem cell research is morally justifiable, two views in respect of a human being were considered: i. a human has a dualistic nature in which his body and soul are two separate entities or ii. his body and soul forms a unity which can not be separated. If a human has a dualistic nature, it means that the embryo is not a human, it does not have a soul because the soul is added later to form a human. The implication of this is that it will be morally justifiable to kill an embryo during embryonic stem cell research. However if body and soul forms a unity which can not be separated, the embryo is a human which is already developing into a full grown human with several stages of development. It will thus not be morally justifiable to kill an embryo as this will violate the sixth commandment, i.e. “Thou shalt not kill.” To determine whether a human’s body and soul is an inseparable unity or whether they are two separate entities, the Pauline letters' view on the human being was investigated. The research method employed was to do a comparative literary study to highlight the different aspects of stem cell research and then exegesis was done in respect of body (σoμα / sōma); soul (ψυχὴ / psychē) and spirit (πνεῦμα / pneuma) in the Pauline letters according to the grammatical-historical method. An electronic Bible Concordance was used to determine the texts in which the above concepts appear. A semantic word analysis was also done to analyse these concepts. Then authoritative commentaries were used to check the findings. The analysis indicated that Paul refers to a human as unity in which body and soul can not be separated. The implication of this finding is that embryonic stem cell research should be dismissed because it will result in the destruction of embryos. Humans will thus be killed in violation of the sixth commandment. On the other hand adult stem cell research should be encouraged because it has the potential to cure diseases which has up to now been incurable. / Thesis (MTh (Ethics))--North-West University, Potchefstroom Campus, 2013.