Interleukin-12 supports in vitro self-renewal of long-term hematopoietic stem cells

E3 ubiquitin ligase on the biological properties of hematopoietic stem cell

Hematopoietic stem cells are a group of heterogeneity cells with the potential to differentiate into various types of mature blood cells. Their basic biological properties include quiescence, self-renewal, multilineage differentiation, and homing ability, with the homing of exogenous hematopoietic stem cells after transplantation becoming a new focus, while the first three properties share some similarity in mechanism due to connectivity. In various complex mechanisms, the role of E3 ubiquitin ligases in hematopoietic homeostasis and malignant transformation is receiving increasing attention. As a unique part, E3 ubiquitin ligases play an important role in physiological regulation mechanism of posttranslational modification. In this review, we focus on the recent progress of the crucial role of E3 ubiquitin ligases that target specific proteins for ubiquitination to regulate biological properties of hematopoietic stem cells. Additionally, this paper deals with E3 ubiquitin ligases that affect the biological properties through aging and summarizes the relevant applications of targeting E3 ligases in hematopoietic malignancies. We present some ideas on the clinical application of E3 ubiquitin ligase to regulate hematopoietic stem cells and also believe that it is meaningful to study the upstream signal of these E3 ubiquitin ligases because hematopoietic stem cell dysfunction is caused by deficiency of some E3 ligases.

Isolation, Maintenance and Expansion of Adult Hematopoietic Stem/Progenitor Cells and Leukemic Stem Cells

Hematopoietic stem cells (HSCs) are rare, self-renewing cells that perch on top of the hematopoietic tree. The HSCs ensure the constant supply of mature blood cells in a tightly regulated process producing peripheral blood cells. Intense efforts are ongoing to optimize HSC engraftment as therapeutic strategy to treat patients suffering from hematopoietic diseases. Preclinical research paves the way by developing methods to maintain, manipulate and expand HSCs ex vivo to understand their regulation and molecular make-up. The generation of a sufficient number of transplantable HSCs is the Holy Grail for clinical therapy. Leukemia stem cells (LSCs) are characterized by their acquired stem cell characteristics and are responsible for disease initiation, progression, and relapse. We summarize efforts, that have been undertaken to increase the number of long-term (LT)-HSCs and to prevent differentiation towards committed progenitors in ex vivo culture. We provide an overview and compare methods currently available to isolate, maintain and enrich HSC subsets, progenitors and LSCs and discuss their individual advantages and drawbacks.

Gene knockout in highly purified mouse hematopoietic stem cells by CRISPR/Cas9 technology

The CRISPR/Cas9 system has been used for genome editing of human and mouse cells. In this study, we established a protocol for gene knockout (KO) in mouse hematopoietic stem cells (HSCs). HSCs were highly purified from the bone marrow of tamoxifen-treated Cas9-EGFP/Cre-ER transgenic mice, maintained in serum-free polyvinyl alcohol culture with cytokines, lentivirally transduced with sgRNA-Crimson, and transplanted into lethally irradiated mice with competitor cells. Previous studies of Pax5 KO mice have shown B cell differentiation block. To verify our KO HSC strategy, we deleted Pax5 gene in 600 CD201+CD150+CD48-c-Kit+Sca-1+Lin- cells (HSC1 cells), highly enriched in myeloid-biased HSCs, and CD201+CD150-CD48- c-Kit+Sca-1+Lin- cells (HSC2 cells), highly enriched in lymphoid-biased HSCs. As predicted, both Pax5 KO HSC1 and HSC2 cells showed few B cells in the peripheral blood and the accumulation of pro-B cells in the bone marrow of recipient mice. Our data suggesetd that myeloid-biased and lymphoid-biased HSCs share a common B cell differentiation pathway. This population-specific KO strategy will find its applications for gene editing in a varity of somatic cells, particuarly rare stem and progenitor cells from different tissues.

Erratum: IL-12 supports in vitro self-renewal of LT HSC

[This corrects the article DOI: 10.1097/BS9.0000000000000002.].

Inflammation, Aging and Hematopoiesis: A Complex Relationship

All vertebrate blood cells descend from multipotent hematopoietic stem cells (HSCs), whose activity and differentiation depend on a complex and incompletely understood relationship with inflammatory signals. Although homeostatic levels of inflammatory signaling play an intricate role in HSC maintenance, activation, proliferation, and differentiation, acute or chronic exposure to inflammation can have deleterious effects on HSC function and self-renewal capacity, and bias their differentiation program. Increased levels of inflammatory signaling are observed during aging, affecting HSCs either directly or indirectly via the bone marrow niche and contributing to their loss of self-renewal capacity, diminished overall functionality, and myeloid differentiation skewing. These changes can have significant pathological consequences. Here, we provide an overview of the current literature on the complex interplay between HSCs and inflammatory signaling, and how this relationship contributes to age-related phenotypes. Understanding the mechanisms and outcomes of this interaction during different life stages will have significant implications in the modulation and restoration of the hematopoietic system in human disease, recovery from cancer and chemotherapeutic treatments, stem cell transplantation, and aging.

Successful ex vivo expansion of mouse hematopoietic stem cells

Ex vivo expansion of hematopoietic stem cells (HSCs) is considered the holy grail in stem cell biology and therapy, as it has long been difficult to make this procedure possible. Yamazaki's research team has established new, polyvinyl alcohol-based culture conditions and shown a significant expansion of mouse HSCs from a small number of cells after a month of culture. Surprisingly, expanded HSCs were able to reconstitute unconditioned normal mice. There is generally a technical concern in limiting dilution assay to estimate a fold-expansion of HSCs. But, this work paves the way toward expansion of human HSCs useful for transplantation medicine.