Induced Hematopoietic Stem Cells: Unlocking Restrictions in Lineage Potential and Self-renewal

Learning from Mother Nature: Innovative Tools to Boost Endogenous Repair of Critical or Difficult-to-Heal Large Tissue Defects

For repair of chronic or difficult-to-heal tissue lesions and defects, major constraints exist to a broad application of cell therapy and tissue engineering approaches, i.e., transplantation of “ex vivo” expanded autologous stem/progenitor cells, alone or associated with carrier biomaterials. To enable a large number of patients to benefit, new strategies should be considered. One of the main goals of contemporary regenerative medicine is to develop new regenerative therapies, inspired from Mother Nature. In all injured tissues, when platelets are activated by tissue contact, their released factors promote innate immune cell migration to the wound site. Platelet-derived factors and factors secreted by migrating immune cells create an inflammatory microenvironment, in turn, causing the activation of angiogenesis and vasculogenesis processes. Eventually, repair or regeneration of the injured tissue occurs via paracrine signals activating, mobilizing or recruiting to the wound site cells with healing potential, such as stem cells, progenitors, or undifferentiated cells derived from the reprogramming of tissue differentiated cells. This review, largely based on our studies, discusses the identification of new tools, inspired by cellular and molecular mechanisms overseeing physiological tissue healing, that could reactivate dormant endogenous regeneration mechanisms lost during evolution and ontogenesis.

Meis1 is critical to the maintenance of human acute myeloid leukemia cells independent of MLL rearrangements

Although the outcome of patients with acute myeloid leukemia (AML) has improved by optimized chemotherapy regimens and bone marrow transplantation, leukemia relapse remains one of the most challenging problems during therapy. Sustained existence of AML blasts is a fundamental determinant for the development of leukemia and resistance to therapy. Recent evidences suggest that Meis1 is tightly associated with the self-renewal capacity of normal hematopoietic stem cells. Meis1 was also found to be essential for the development of mixed lineage leukemia (MLL)-rearranged leukemia. Whether Meis1 functions independently of MLL abnormality in the context of leukemia is unclear. Herein, we identified a distinct expression pattern of Meis1 in patients with newly diagnosed AML without MLL abnormality. High levels of Meis1 expression were found in 64 of 95 (67.4%) AML patients; whereas, 31 of 95 (32.6%) patients showed dramatically lower levels of Meis1, compared with the median level of Meis1 in healthy donors. The whole cohort and subgroup analyses further demonstrated that high Meis1 expression levels were associated with a resistance to conventional chemotherapy, compared with the group with low Meis1 levels (P = 0.014 and P = 0.029, respectively). In vitro knockdown experiments highlighted a role of Meis1 in regulating maintenance and survival of human AML cells. These results implicate that Meis1 functions as an important regulator during the progression of human AML and could be a prognostic factor independent of MLL abnormality.