Different strategies of mixed chimerism induction may determine stem/progenitor cell populations in recipient mice

Mixed chimerism and transplant tolerance are not effectively induced in C3a-deficient mice

Mixed chimerism, a phenomenon involved in the development of specific alloantigen tolerance, could be achieved through the transplantation of hematopoietic stem cells into properly prepared recipients. Because the C3a complement component modulates hematopoietic cell trafficking after transplantation, in the present study, we investigated the influence of the C3a deficiency on mixed chimerism and alloantigen tolerance induction. To induce mixed chimerism, C57BL/6J (wild-type strain; H-2K(b); I-E(-)) and B6.129S4-C3(tm1Crr)/J (C3a-deficient) mice were exposed to 3 G total body irradiation (day -1). Subsequently, these mice were treated with CD8-blocking (day -2) and CD40L-blocking (days 0 and 4) antibodies, followed by transplantation with 20 × 10(6) Balb/c (H-2K(d); I-E(+)) bone marrow cells (day 0). The degree of mixed chimerism in peripheral blood leukocytes was measured several times during the 20-week experiment. The tolerance to Balb/c mouse antigens was assessed based on the number of lymphocytes expressing Vβ5 and Vβ11 T-cell receptor and on skin-graft (day 0) acceptance. Applying our experimental model, mixed chimerism and alloantigen tolerance were effectively induced in C57BL/6J (wild-type) mice, but not in C3a(-/-) animals. The present study is, to our knowledge, the first to demonstrate that C3a is vital for achieving stable mixed chimerism and related to this induction of transplant tolerance.

Bone marrow cell mobilization by the systemic use of granulocyte colony-stimulating factor (GCSF) improves wound bed preparation

Innovative approaches are needed to accelerate the healing of human chronic wounds not responding to conventional therapies. An evolving and promising treatment is the use of stem cells. Our group has previously described the use of expanded (in vitro) autologous stem cells aspirated from human bone marrow and applied topically in a fibrin spray to human acute and chronic wounds. More recently, we have sought ways to mobilize stem cells directly from the bone marrow, without in vitro expansion. In this report, we show that systemic injections of granulocyte colony-stimulating factor (GCSF) can mobilize stem cells from bone marrow into the peripheral blood and then to the wound site. Our objectives were to optimize parameters for this method by using mouse models and proof of principle in a human chronic wound situation. Mice were injected for 5 days with 2 different formulations of GCSF and compared to control saline. To monitor stem cell mobilization, flow cytometric measurements of Sca-1 and c-Kit and colony-forming cell assays were performed. Full-thickness tail wounds in mice were created and monitored for healing, and polyvinyl alcohol sponges were implanted dorsally to assess collagen accumulation. To determine bone marrow stem cell homing to the wound site, chimeric mice transplanted with Green Fluorescent Protein bone marrow cells were scanned by live imaging. Additionally, as proof of principle, we tested the systemic GCSF approach in a patient with a nonhealing venous ulcer. Our findings lay the ground work and indicate that the systemic administration of GCSF is effective in mobilizing bone marrow stem cells into the peripheral blood and to the wound site. These findings are associated with an increased accumulation of collagen and promising results in terms of wound bed preparation and healing.

Mixed chimerism induction influences cytokine release from chimeric mice cells

Interest in mixed chimerism has evolved from its role in the induction of alloantigen tolerance. However, its precise impact on the host organism remains to be elucidated. In the present work, we analyzed cytokine secretion from chimeric mice cells to assess the influence of different mixed chimerism induction protocols on immune system function in recipient mice. To our knowledge, there have been no reports on using this parameter for the optimization of the mixed chimerism induction method. B6.SJL-PtprcaPep3b or C57BL/6J mice were used as recipients and Balb/c as donors. We utilized four protocols which consisted of: 3Gy total body irradiation (day -1), the injection of 20-30×10(6) bone marrow cells (day 0), and a combination of CD40L (days 0 and 4), CD8 (day -2), and NK1.1 (day -3) blocking antibodies and cyclophosphamide (175mg/kg - day 2). The concentrations of cytokines (IFN-γ, IL-2, IL-4, IL-6, IL-10, IL-17A, and TNF) were evaluated in the supernatants of unstimulated or phytohemagglutinin-stimulated chimeric spleen, bone marrow and peripheral blood cells in the 8th week of experiment. The induction of tolerance to Balb/c mouse antigens was initially tested in chimeric mice by assessing the presence of Vβ5 and Vβ11 TCR-expressing lymphocytes. The cytokine production was considerably increased, especially in chimeric mice treated by cyclophosphamide. Also the mixed chimerism itself seems to affect IFN-γ, IL-2, IL-4, IL-6, IL-17A, and TNF secretion. Using the optimized induction protocol, we established that chimeric mice cells secreted lower IFN-γ, IL-2, IL-4 and higher IL-6, IL-17A, and TNF levels as compared to control animals. We found that both donor and recipient cells markedly participated in the cytokine production. In conclusion, our optimization study based on cytokine assessment contributes to establishing an effective protocol of mixed chimerism induction with no cyclophosphamide use and better understanding of the influence of this phenomenon on the recipient organism.