Exploring tissue regeneration potential of multipotent mesenchymal cells from human placenta. Mimicking hyperglycaemia in vitro affects cell proliferation and differentiation properties

The recent interest that has aroused about the discovery and functional characterization of stem cells is based on the firm belief that they can offer new therapeutic possibilities for the cure of degenerative and genetic pathologies. Regenerative medicine, tissue engineering and gene therapy display an urgent need to isolate cells that can lead to regeneration of a healthy tissue, in order to counterbalance disease-induced cellular death and tissue damage. Stem cells show two peculiar features that make them particularly suitable for regenerative medicine applications: high proliferative capacity and differentiation potential. These terms are generally comprised in the concept of plasticity. Adult stem cells have been isolated from several different tissues (nervous system, peripheral blood, bone marrow, epidermis). Unfortunately, the origin from an adult organism reduces plasticity of stem cells, limiting their possible exploitation by therapeutic field. In this case, embryonic stem cells display optimal potential; anyway, their isolation raises ethic and moral controversies that prevent their use in many countries all over the world, included Italy. During the research of alternative sources of stem cells, we focused on human placenta, given that it is an easily available organ in which the presence of cells with stemness features has been well-documented. This doctoral thesis demonstrated that term human placenta is an organ endowed with stem elements of different origin and nature. We established an experimental protocol to allow an easy and effective isolation of such elements from foetal region of placenta, with particular regard to cell originated from mesenchymal lineage. Both placentas from healthy donors and diabetic patients were collected and their cells isolated. These cells were expanded in culture as a plastic adherent homogeneous population of CD34neg fibroblast-like cells displaying high proliferative potential and clonal properties. Both cells from healthy and diabetic donor expressed a unique pattern of mesenchymal and multipotency antigens which excluded contamination from other undifferentiated or mature cell types (hematopoietic stem and endothelial cells) and contributed to define them as human Chorionic Mesenchymal Stem Cells (hCMSC). Multipotency properties and differentiation potential were demonstrated through in vitro induction of adipogenic, osteogenic and chondrogenic commitment. Given the intrinsic plasticity showed, mesenchymal multipotent placenta-derived cells could be employed for regeneration of hard tissues. Mesenchymal multipotent cells from human placenta also displayed reduced immunogenicity and immunomodulatory properties if compared to well-characterized mesenchymal stem cells from bone marrow. This study also evaluated the effects of sustained hyperglycaemia in vitro on proliferation and differentiation properties of mesenchymal multipotent cells from human placenta. In particular, we focused on commitment towards endothelial lineage. We provided proofs for the impairment of cells proliferation potential caused by prolonged exposure to hyperglycaemia and demonstrated that these events created a microenvironment able to increase cell responsiveness to treatment with endothelial-specific growth factors. In fact, placental cells incubated with high glucose (25mM), VEGF and FGF2 committed towards endothelial lineage until they reached an intermediate differentiation status. Thus, we concluded that hyperglycaemia in vitro might not be a barrier for the effective functional improvement of placental cells transplantation, but, on the contrary, it could function by supporting cells metabolic needs during differentiation and enhancing growth factor action.