Project description:There are no described quality assurance mechanisms for newly formed stem cells. We observed intimate interactions between macrophages and blood stem cells in zebrafish embryos. Stressed stem cells were marked by surface Calreticulin, which stimulates macrophage interaction as an eat me signal. Macrophage-stem cell interactions either lead to removal of cytoplasmic material and stem cell proliferation or resulted in complete stem cell engulfment. Calreticulin knock down or embryonic macrophage depletion reduced the number of stem cell clones into adulthood. Our work supports a model in which embryonic macrophages determine hematopoietic clonality by monitoring stem cell quality.
Project description:This clinical trial studies fludarabine phosphate, low-dose total-body irradiation, and donor stem cell transplant followed by cyclosporine, mycophenolate mofetil, and donor lymphocyte infusion in treating patients with hematopoietic cancer. Giving low doses of chemotherapy, such as fludarabine phosphate, and total body irradiation (TBI) before a donor peripheral blood stem cell transplant helps stop the growth of cancer cells. It may also keep the patient’s immune response from rejecting the donor’s stem cells. The donated stem cells may replace the patient’s immune cells and help destroy any remaining cancer cells (graft-versus-tumor effect). Giving an infusion of the donor’s T cells (donor lymphocyte infusion) after the transplant may help increase this effect. Sometimes the transplanted cells from a donor can also make an immune response against the body’s normal cells. Giving cyclosporine and mycophenolate mofetil after the transplant may stop this from happening.
Project description:Activation of mostly quiescent hematopoietic stem cells (HSC) is a prerequisite for life-long blood production1, 2. This process requires major molecular adaptations to meet the regulatory and metabolic requirements for cell division3-8. The mechanisms governing cellular reprograming upon stem cell activation and their subsequent return to quiescence are still not fully characterized. Here, we describe a role for chaperone-mediated autophagy (CMA)9, a selective form of lysosomal protein degradation, in sustaining adult HSC function. CMA is required for stem cell protein quality control and upregulation of fatty acid metabolism upon HSC activation. We identify that CMA activity decreases with age in HSC and show that genetic or pharmacological activation of CMA can restore functionality of old HSC. Together, our findings provide mechanistic insights into a new role for CMA in sustaining quality control, appropriate energetics and overall long-term hematopoietic stem cell function. Our work supports that CMA may be a promising therapeutic target to enhance hematopoietic stem cell function in conditions such as aging or stem cell transplantation.