Células tronco imaturas de polpa dentária humana: uma nova estratégia terapêutica para o tratamento da aplasia de medula óssea em modelo animal.

GONZAGA, F. V. Immature stem cells from human dental pulp: a new therapeutic strategy for the treatment of bone marrow suppression in an animal model. 2016. 149 p. Dissertation (Master in Biotechnology) – Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, 2016. Aplastic anemia (AA) is the most frequent bone marrow (BM) failure syndrome, which may be caused by the exposure of high doses of radiation or drugs. AA is characterized by peripheral pancytopenia and bone marrow hypoplasia, which can lead to death. In severe cases of AA, treatments are limited to allogeneic BM transplant and/or immunosuppressants administration. For this purpose, the donor blood must be typed to identify their HLA, which should be compatible with recipient blood. Although the number of BM donors registered in Brazil grows every year, due to the ethnic diversity became more difficult to match compatible donors. Thus, the development of stem cell-based therapeutic strategy that employs allogeneic cells of low immunogenicity may be a promising tool for AA treatment. Thereby, mesenchymal stem cells (MSCs) are appropriate candidates for therapeutic use, because they present low immunogenicity and provide immunomodulation effect in tissue repair. Furthermore, MSCs comprise the BM stromal niche and have important role in supporting hematopoiesis. Therefore, we proposed human dental pulp stem cells (hDPSC), which is a type of MSC, to be tested as an experimental treatment in AA experimental model. AA was induced using chemical drug (cyclophosphamide) (n = 10) and 6Gy ionizing radiation (n = 40). Radiation exposure caused BM ablation in mice while cyclosphosphamide did not provide sufficient ablation, thus ionizing radiation of AA model was selected. After radiation, the mice received three equal doses of hDPSC each 15-day via intraperitoneal injection. Clinical response was monitored by body mass, blood cells counting and histopathology of BM. The influence of hDPSC infusion on hematopoiesis and engraftment capacity of this cell was investigated. Additionally, we verified the ability of BM derived cells to form colonies using unity colony formation (CFU-f) assay before and after cell transplantation. Our data show the hDPSC transplantation in irradiated mice improves clinical and laboratory conditions demonstrating high survival rate (no death); body mass gain; improvement values of erythrocytes, hematocrit and leukocytes. Although transplant intraperitoneal showed low hDPSC grafting in BM, the recovery of medullary components was significantly. Moreover, the transplantation of hIDPSC contributed with the recovery of medullary components since it was demonstrated an increase of expression of n murine hematopoietic stem cell (HSCs) and stem cell progenitors (Sca1, c-kit, CD34, CD44 and CD45), endothelial cells (nestin and CD105) and stromal (CD90) markers when compared to untreated group. Furthermore, mice treated with hDPSC present lower number of apoptotic cells compared to the untreated group. The results indicate that hDPSC transplantation is a potential tool for AA cell-based therapeutics, thus opening new perspectives in the application of hIDPSC in regenerative medicine.