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Study of mesenchymal stem cells and lymphocytes interaction in graft versus host disease model

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Marília Normanton
Total Authors: 1
Document type: Master's Dissertation
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
Defense date:
Examining board members:
Luciana Cavalheiro Marti; José Eduardo Levi; Karina Inácio Ladislau de Carvalho Salmazi
Advisor: Luciana Cavalheiro Marti

A major complication after hematopoietic stem cell transplantation is the graft versus host disease (GVHD), which is an immunological response of transplanted donor T cells against the recipient tissues; this outline is responsible for 15-30% of deaths that can occur after allogeneic hematopoietic stem cells transplant. Despite recent advances in reducing GVHD incidence by alternating prophylactic regimens, thus reducing the intensity of conditioning, there are few effective treatments. Recently, the immune modulatory potential of mesenchymal stem cells has become the focus of several studies. Some authors described the role of these cells in reducing immune response by inhibiting T cell proliferation, representing a potential new therapy for GVHD. Through this knowledge, we investigated the mesenchymal stem cells role into T lymphocytes proliferation, apoptosis and cytokine production. Our results showed that the presence of mesenchymal stem cells into the cultures downregulates the proliferation of stimulated lymphocytes independent of contact and apoptosis of stimulated lymphocytes in partially contact-dependent manner. We also observed during naive T lymphocytes differentiation into Th17 cells, that the mesenchymal stem cell presence reduces the lymphocyte ability in producing the GVHD major effectors cytokines, interferon gamma (IFN-y) and interleukin-17A (IL-17A). We investigated whether prostaglandin E2 (PGE2) was involved in the reduction of T lymphocytes proliferation, when cultured with mesenchymal stem cells, by tryptophan depletion. Indomethacin (IDT), an anti-inflammatory drug blocker of cyclooxygenase (COX 1 and 2) and therefore PGE2 pathway, was used. However, we observed that, according to IDT dose, blocking this pathway further inhibited lymphocyte proliferation. With this result we conclude that if lymphocyte proliferation is inhibited by tryptophan depletion, it does not occur via PGE2. However, we still cannot say whether this pathway is activated by other molecules, or if this pathway is actually responsible for T lymphocytes proliferation inhibition. Regarding the apoptosis inhibition in T lymphocytes, we show that the IL-7 receptor alpha chain (CD127) is increased on the surface of T lymphocytes when in the presence of mesenchymal stem cells. We found that IL-7 blockage in the cultures increases apoptosis in T lymphocytes, as well as their addition causes apoptosis decrease. We also identified the intracellular production of IL-7 on mesenchymal stem cells, linking these cells and IL-7 directly with apoptosis inhibition in T lymphocytes under these conditions This work has generated data that allowed the understanding of some possible mechanisms by which MSCs can act on activated and/or alloreactive T lymphocytes; mechanisms that can be used as a basis for future research in the elucidation and prevention of GVHD (AU)

FAPESP's process: 12/02197-3 - Study of mesenchymal stem cell and lymphocytes interactions using the graft vesus host desease model.
Grantee:Marilia Normanton
Support Opportunities: Scholarships in Brazil - Master