Characterising the heterogeneity of human mid-trimester amniotic fluid stem cells

Amniotic fluid stem cells (AFSCs) are a highly promising potential source of cells for regenerative medicine as they are easily obtainable and avoid ethical concerns. Originally described as having an intermediate phenotype between embryonic stem cells (ESCs) and mesenchymal stem cells (MSCs), AFSCs have been shown to exhibit similarities with ESCs in that they express pluripotency markers which would prohibit their use in the clinic. There are various additional issues which need to be addressed before progress can be made towards the use of AFSCs in translational medicine. Firstly, the heterogeneity of AFSCs must be addressed. Recent reports suggested the existence of two distinct populations of cells, RS AFSCs and SS AFSCs. However, an in-depth characterisation of the immunophenotype and differentiation capacity is yet to be performed. Next, reports that AFSC express pluripotency markers are of concern and threaten the potential clinical utility of these cells. This thesis provides a robust investigation of the expression of OCT4A in AFSCs and demonstrates how OCT4A expression should be assessed in order to exclude false positive results and misleading data. Neither subpopulations of cells express the pluripotency marker OCT4A. This evidence therefore greatly supports AFSC as a potential cellular source for regenerative medicine. Finally, investigation of the two AFSCs subpopulations with regards to their transcriptome, secretome and exosome cargo remains to be performed. I have found that SS AFSCs express mesenchymal markers and comply with the MSC criteria, therefore I suggested that they are of MSCs origin. To compare, RS AFSCs does not comply with the criteria, but they express renal progenitor markers. The transcriptome confirmed the above findings and revealed the differences in gene expression of both subtypes. SS AFSCs secretome showed secretion of MSCs factors such as VEGF, CXCL12, while RS AFSCs secreted factors like MCP-1 and TIMP1