A proteomic investigation of multi-lineage differentiated adult adipose-derived stem cells

Regenerative medicine and stem cell therapies has rapidly come into vogue and remained in the public and research spotlight for the last decade due to the bountiful applications it promises. A large number of clinical applications now exist for a wide variety of injuries or disease states, ranging from skin damage in burn victims to degenerative joints in aged patients and, in a limited capacity, the repair of neuronal tissue. Notwithstanding these advances, there is an insufficiency in the knowledge base regarding a stem cell’s fate and characterisation of the extent of differentiation. This thesis presents the first investigation of its type, a broad proteomic investigation of differentiated stem cells derived from both rat and human adipose tissue. The breadth of this body of work investigated the cellular and secreted proteome changes of homogenous ADSC cultures directed toward various phenotypic lineages by means of induction media. These differentiated lineages included osteocytes, chondrocytes, myocytes, adipocytes and neuronal phenotypes. For a marked comparison, primary derived cells from the relevant mature tissue were used as a benchmark measure for the extent of differentiation in the majority of the differentiation experiments. These comparisons aimed to expand our current knowledge about the depth of change occurring during each ADSC differentiation with respect to the mature primary derived cells. Furthermore this study queried the validity of currently employed markers and the possible alternative proteins identified which could be considered for future work. The core chapters focused on the extent of neurogenic differentiation with various chemical inducers. The initial chemical investigated, the previously published β-mercaptoethanol which acted as an inducer, was found to have an overall toxic effect on cells, indicated by the up-regulation of stress proteins, if in contact for up to 24 hours. However the chemical initiated a morphological change that mimicked neuronal cells which furthermore expressed key neuronal protective and restructuring proteins. Nonetheless the cell’s proteome indicated that β-mercaptoethanol induced an overall cellular distress. Novel to this study was the investigation of a naturally occurring chemical alternative; cyclic ketamine class chemicals that was theorised to have a less toxic effect. The cyclic ketamines investigated proved to be a superior induction chemical producing a higher population of cells that exhibited neuronal morphological properties as well as a wide variety of neuronally related proteins. These differentiations proved to be far gentler with a marked decrease in expression of stress related proteins compared to the β-mercaptoethanol treated cells. Due to the novel application and findings of the cyclic ketamine based neuronal induction a patent was filed around the method for the future development into a clinical and pharmaceutical application.