Dissection of the Human Multipotent Adult Progenitor Cell (MAPC) Secretome by Proteomic Analysis

Digitalitzat per Artypla

Crosstalk with Inflammatory Macrophages Shapes the Regulatory Properties of Multipotent Adult Progenitor Cells

Macrophages and microglia are key effector cells in immune-mediated neuroinflammatory disorders. Driving myeloid cells towards an anti-inflammatory, tissue repair-promoting phenotype is considered a promising strategy to halt neuroinflammation and promote central nervous system (CNS) repair. In this study, we defined the impact of multipotent adult progenitor cells (MAPC), a stem cell population sharing common mesodermal origin with mesenchymal stem cells (MSCs), on the phenotype of macrophages and the reciprocal interactions between these two cell types. We show that MAPC suppress the secretion of tumor necrosis factor alpha (TNF-α) by inflammatory macrophages partially through a cyclooxygenase 2- (COX-2-) dependent mechanism. In turn, we demonstrate that inflammatory macrophages trigger the immunomodulatory properties of MAPC, including an increased expression of immunomodulatory mediators (e.g., inducible nitric oxide synthase (iNOS) and COX-2), chemokines, and chemokine receptors. Macrophage-primed MAPC secrete soluble factors that suppress TNF-α release by macrophages. Moreover, the MAPC secretome suppresses the antigen-specific proliferation of autoreactive T cells and the T cell stimulatory capacity of macrophages. Finally, MAPC increase their motility towards secreted factors of activated macrophages. Collectively, these in vitro findings reveal intimate reciprocal interactions between MAPC and inflammatory macrophages, which are of importance in the design of MAPC-based therapeutic strategies for neuroinflammatory disorders in which myeloid cells play a crucial role

The insulin-like growth factor system and adenocarcinoma of the colon

The insulin-like growth factor (IGF) system is important in normal growth and development. However, it is also known to be involved with malignant transformation and cellular proliferation. IGF binding proteins modulate the biological activity of IGF-I, either potentiating or inhibiting its activity, as well as determining how much enters the circulation at any one time. IGF binding protein-4 (IGFBP-4), for example is believed to be inhibitory to the effects of IGF-I. This thesis shows that the colon cancer cell lines Colo 205, HT29 and WiDR proliferate in response to IGF-I, and that IGFBP-4 at high concentrations inhibits their growth. However, it was found that with lower concentrationsof IGFBP-4, proliferation in HT29 and WiDR cells increased. Nevertheless in two cell lines, IGFBP-4 partially negated the proliferative effects of IGF-I. An antibody against IGFBP-4 was used to show that endogenous IGFBP-4 plays an important role in modifying cell growth. In order to start in vivo experiments which required considerable quantities of IGFBP-4, this protein was produced in an expression system and purified using an immunoaffinity column method. The rhIGFBP-4 thus produced was shown to be functional and to inhibit colorectal cancer cell growth in vitro. A nude mouse model of colon cancer was produced and the expression of components of the IGF system in this model determined using PCR. Experiments were performed using conditioned medium from Colo 205 cells to investigate IGFBP-4 protease activity. This thesis shows that manipulation of the IGF system is a potential target for further research into treatment for adenocarcinoma of the colon