Project description:Stem cells reside in specialized microenvironments, termed niches, at several different locations within tissues1-3. The differential functions of heterogeneous stem cells and niches are important given increasing clinical applications of stem cell transplantation and immunotherapy. It remains unknown whether hierarchical structures amongst stem cells at distinct niches exist, and further control aspects of immune tolerance. Here, we propose novel hierarchical arrangements within hematopoietic stem cells (HSCs) and bone marrow (BM) niches, that dictate both regenerative potential and immune privilege. High level nitric oxide-generating (NOHi) HSCs are refractory to immune attack and exhibit "delayed" albeit robust long-term reconstitution. Such highly immune privileged, primitive NOHi HSCs colocalize with distinctive capillaries, characterized by primary ciliated endothelium and high levels of the immune checkpoint molecule CD200. These capillaries regulate the regenerative functions of NOHi HSCs through ciliary protein IFT20/CD200/eNOS/autophagy signals, further mediating immune protection. Notably, previously described niche constituents, sinusoidal cells and Type H vessels2-10, co-localize with less immune privileged and less potent NOLow HSCs. Therefore, we have identified highly immune privileged, "late-rising" primitive HSCs and characterized their immunoprotective niches constituted of specialized vascular domains. Our studies suggest the niche may orchestrate hierarchy in stem cells and immune tolerance, delineating future immunotherapeutic targets.
Project description:The hematopoietic niches in bone marrow (BM) are specialized compartments working in harmony to regulate all the steps of the hematopoiesis cascade. Little is known about how BM niches in healthy humans. Therefore, we investigated the presence of different niches in healthy human BM using comparative omic technologies (Metabolomic and transcriptomic). We sequenced and comparative analyzed mRNA samples of human bone marrow mesenchymal stem cells (MSCs) to generate the gene expression profiles of these cells which obtained from two anatomically different BM regions (R1 and R2).
Project description:The medial prefrontal cortex (mPFC) is known as a hub of social hierarchy determination in the brain, Using high throughput single cell transcriptomic analysis and projection-specific genetic manipulation, we discovered that the expression level of Pou3f1 in mPFC-VTA neurons controls social hierarchy.
Project description:We have previously shown that skull bone marrow derived myeloid cells are different from their blood derived counterparts. Whether or not cues from the CNS microenvironment differentially shape the skull bone marrow niche relative to peripheral bone marrow niches is unknown. To test this, we performed scRNAseq of skull and peripheral bone marrow niches.
Project description:Genetic and epigenetic lesions within hematopoietic cell populations drive diverse hematological malignancies. Myelodysplastic syndromes (MDS) are a group of myeloid neoplasms affecting the hematopoietic stem cells characterized by recurrent genetic abnormalities, myelodysplasia (a pathological definition of abnormal bone marrow structure), ineffective hematopoiesis resulting in blood cytopenia, and a propensity to evolve into acute myelogenous leukemia. Although there is evidence that the accumulation of a set of genetic mutations is an essential event in MDS, there is an increased appreciation of the contribution of specific microenvironments, niches, in the pathogenesis of MDS and response to treatment. In physiologic hematopoiesis, niches are critical functional units that maintain hematopoietic stem and progenitor cells and regulate their maturation into mature blood cells. In MDS and other hematological malignancies, altered bone marrow niches can promote the survival and expansion of mutant hematopoietic clones and provide a shield from therapy. In this review, we focus on our understanding of the composition and function of hematopoietic niches and their role in the evolution of myeloid malignancies, with an emphasis on MDS.
Project description:In acute lymphoblastic leukemia (ALL) the bone marrow microenvironment provides growth and survival signals that may confer resistance to chemotherapy. Granulocyte colony-stimulating factor (G-CSF) potently inhibits lymphopoiesis by targeting stromal cells that comprise the lymphoid niche in the bone marrow. To determine whether lymphoid niche disruption by G-CSF sensitizes ALL cells to chemotherapy, we conducted a pilot study of G-CSF in combination with chemotherapy in patients with relapsed or refractory ALL. Thirteen patients were treated on study; three patients achieved a complete remission (CR/CRi) for an overall response rate of 23%. In the healthy volunteers, G-CSF treatment disrupted the lymphoid niche, as evidenced by reduced expression of CXCL12, interleukin-7, and osteocalcin. However, in most patients with relapsed/refractory ALL expression of these genes was markedly suppressed at baseline. Thus, although G-CSF treatment was associated with ALL cell mobilization into the blood, and increased apoptosis of bone marrow resident ALL cells, alterations in the bone marrow microenvironment were modest and highly variable. These data suggest that disruption of lymphoid niches by G-CSF to sensitize ALL cells to chemotherapy may be best accomplished in the consolidation where the bone marrow microenvironment is more likely to be normal.