Strategic priorities for hematopoietic stem cell transplantation in the EMRO region

The World Health Organization-designated Eastern Mediterranean region (EMRO) consists of 22 countries in North Africa and Western Asia with a collective population of over 679 million. The area comprises some of the wealthiest countries per capita income and some of the poorest. The population structure is also unique and contrasts with western countries, with a much younger population. The region sits in the heart of the thalassemia belt. Many countries have a significant prevalence of sickle cell disease, and cancer is on the rise in the region. Therefore, the strategic priorities for the growth and development of hematopoietic stem cell transplantation (HSCT) differ from country to country based on resources, healthcare challenges, and prevalent infrastructure. Thirty-one reporting teams to the Eastern Mediterranean Blood and Marrow Transplantation Group have active HSCT programs in 12 countries; allogeneic transplants outnumber autologous transplants, and the proportion of allotransplants for non-malignant conditions is higher in the EMRO region than in Western Europe and North America. The vast majority (99%) of allotransplants are from matched related donors. Matched unrelated donors and other alternate donor transplants are underutilized. The chance of finding a matched related donor for allografts is higher, with a significant chance of finding matched donors among non-sibling related donors. Reasons for relatively lower rates of transplants compared with other countries are multifactorial. Capacity building, development of newer centers, innovative funding, and better utilization of information technology are required to make transplantation as an accessible modality to more patients. Cost-effectiveness and cost-containment, regulation, and ensuring quality will all be priorities in planning HSCT development in the region.

Worldwide Network for Blood and Marrow Transplantation (WBMT) Recommendations Regarding Essential Medications Required To Establish An Early Stage Hematopoietic Cell Transplantation Program

Establishing a hematopoietic cell transplantation (HCT) program is complex. Planning is essential while establishing such a program to overcome the expected challenges. Authorities involved in HCT program establishment will need to coordinate the efforts between the different departments required to start up the program. One essential department is pharmacy and the medications required. To help facilitate this, the Worldwide Network for Blood and Marrow Transplantation organized a structured survey to address the essential medications required to start up an HCT program. A group of senior physicians and pharmacists prepared a list of the medications used at the different phases of transplantation. These drugs were then rated by a questionnaire using a scale of necessity based on the stage of development of the transplant program. The questionnaire was sent to 30 physicians, in different parts of the world, who have between 5 and 40 years of experience in autologous and/or allogeneic transplantation. This group of experts scored each medication on a 7-point scale, ranging from an absolute requirement (score of 1) to not required (score of 7). The results are presented here to help guide the prioritization of required medications.

Contribution of PDGFRα lineage cells in adult mouse hematopoiesis

Platelet-derived growth factor receptor alpha (PDGFRα) is a dominant marker of mesodermal mesenchymal cells in mice. Previous studies demonstrated that PDGFRα-positive (PDGFRα+) mesodermal cells develop not only into mesenchymal cells but also into a subset of total hematopoietic cells (HCs) in the limited period during mouse embryogenesis. However, the precise characteristics of the PDGFRα lineage positive (PDGFRα Lin+) HCs in adult mouse hematopoiesis are largely unknown. In this study, we systematically evaluated the characteristics of PDGFRα Lin+ HCs in the bone marrow and peripheral blood using PDGFRα-CRE; ROSA^tdTomato mice. Flow cytometry analysis revealed that PDGFRα Lin+ HCs accounted for approximately 20% of total HCs in both the bone marrow and peripheral blood in adult mice. Compositions of myeloid and lymphoid subpopulations among CD45+ mononuclear cells were almost identical in both PDGFRα Lin+ and PDGFRα Lin- cells. Single-cell RNA-sequencing analysis also demonstrated that the transcriptomic signatures of the PDGFRα Lin+ HCs in the peripheral blood largely overlapped with those of the PDGFRα Lin- HCs, suggesting equivalent functions of the PDGFRα Lin+ and PDGFRα Lin- HCs. Although pathophysiological activities of the PDGFRα Lin + HCs were not evaluated, our data clearly demonstrate a significant role of the PDGFRα Lin + HCs in physiological hematopoiesis in adult mice.

Mitochondrial dysfunction and oxidative stress in bone marrow stromal cells induced by daunorubicin leads to DNA damage in hematopoietic cells

Cytotoxic chemotherapies could cause the dysregulation of hematopoiesis and even put patients at increased risk of hematopoietic malignancy. Therapy-related leukemia is mainly caused by cytotoxic chemotherapy-induced genetic mutations in hematopoietic stem/progenitor cells (HSPCs). In addition to the intrinsic mechanism, some extrinsic events occurring in the bone marrow (BM) microenvironment are also possible mechanisms involved in genetic alteration. In the present study, we investigated the damage to BM stromal cells induced by a chemotherapy drug, daunorubicin (DNR) and further identified the DNA damage in hematopoietic cells caused by drug-treated stromal cells. It was found that treatment with DNR in mice caused a temporary reduction in cell number in each BM stromal cell subpopulation and the impairment of clonal growth potential in BM stromal cells. DNR treatment led to a tendency of senescence, generation of intracellular reactive oxygen species, production of cytokines and chemokines, and dysfunction of mitochondrial in stromal cells. Transcriptome microarray data and gene ontology (GO) or gene set enrichment analysis (GSEA) showed that differentially expressed genes that were down-regulated in response to DNR treatment were significantly enriched in mitochondrion function, and negative regulators of reactive oxygen species. Surprisingly, it was found that DNR-treated stromal cells secreted high levels of H₂O₂ into the culture supernatant. Furthermore, coculture of hematopoietic cells with DNR-treated stromal cells led to the accumulation of DNA damage as determined by the levels of histone H2AX phosphorylation and 8-oxo-2'-deoxyguanosine in hematopoietic cells. Overall, our results suggest that DNR-induced BM stromal cell damage can lead to genomic instability in hematopoietic cells.

MicroRNA-101a regulates microglial morphology and inflammation

BACKGROUND

Microglia, as well as other tissue-resident macrophages, arise from yolk sac progenitors. Thus, it is likely that the central nervous system environment is critical for the acquisition of a distinct microglial phenotype. Several microRNAs that are enriched in the brain play crucial roles in brain development and may also play a role in the differentiation of microglia.

METHODS

To track the differentiation of hematopoietic cells into microglia, lineage-negative bone marrow cells were co-cultured with astrocytes in the absence or presence of microRNAs or their inhibitors. Microglia-like cells were identified as small, round cells that were immunopositive for CD11b, Iba1, CX3CR1, and triggering receptor expressed on myeloid cells (TREM)-2.

RESULTS

Five microRNAs (miR-101a, miR-139-3p, miR-214^*, miR-218, and miR-1186) were identified as modifiers of the differentiation of bone marrow-derived microglia-like cells. Among them, miR-101a facilitated the differentiation of bone marrow cells into microglia-like cells most potently. Small, round cells expressing CD11b, Iba1, CX3CR1, and TREM-2 were predominant in cells treated by miR-101a. miR-101a was abundantly expressed in non-microglial brain cells. Transfection of miR-101a into microglia significantly increased the production of IL-6 in response to LPS. Finally, miR-101a downregulated the expression of MAPK phosphatase-1.

CONCLUSIONS

miR-101a, which is enriched in the brain, promotes the differentiation of bone marrow cells into microglia-like cells.

Cooperative interaction of Etv2 and Gata2 regulates the development of endothelial and hematopoietic lineages

Regulatory mechanisms that govern lineage specification of the mesodermal progenitors to become endothelial and hematopoietic cells remain an area of intense interest. Both Ets and Gata factors have been shown to have important roles in the transcriptional regulation in endothelial and hematopoietic cells. We previously reported Etv2 as an essential regulator of vasculogenesis and hematopoiesis. In the present study, we demonstrate that Gata2 is co-expressed and interacts with Etv2 in the endothelial and hematopoietic cells in the early stages of embryogenesis. Our studies reveal that Etv2 interacts with Gata2 in vitro and in vivo. The protein-protein interaction between Etv2 and Gata2 is mediated by the Ets and Gata domains. Using the embryoid body differentiation system, we demonstrate that co-expression of Gata2 augments the activity of Etv2 in promoting endothelial and hematopoietic lineage differentiation. We also identify Spi1 as a common downstream target gene of Etv2 and Gata2. We provide evidence that Etv2 and Gata2 bind to the Spi1 promoter in vitro and in vivo. In summary, we propose that Gata2 functions as a cofactor of Etv2 in the transcriptional regulation of mesodermal progenitors during embryogenesis.

Covalent immobilization of stem cell factor and stromal derived factor 1α for in vitro culture of hematopoietic progenitor cells

Hematopoietic stem cells (HSCs) are currently utilized in the treatment of blood diseases, but widespread application of HSC therapeutics has been hindered by the limited availability of HSCs. With a better understanding of the HSC microenvironment and the ability to precisely recapitulate its components, we may be able to gain control of HSC behavior. In this work we developed a novel, biomimetic PEG hydrogel material as a substrate for this purpose and tested its potential with an anchorage-independent hematopoietic cell line, 32D clone 3 cells. We immobilized a fibronectin-derived adhesive peptide sequence, RGDS; a cytokine critical in HSC self-renewal, stem cell factor (SCF); and a chemokine important in HSC homing and lodging, stromal derived factor 1α (SDF1α), onto the surfaces of poly(ethylene glycol) (PEG) hydrogels. To evaluate the system's capabilities, we observed the effects of the biomolecules on 32D cell adhesion and morphology. We demonstrated that the incorporation of RGDS onto the surfaces promotes 32D cell adhesion in a dose-dependent fashion. We also observed an additive response in adhesion on surfaces with RGDS in combination with either SCF or SDF1α. In addition, the average cell area increased and circularity decreased on gel surfaces containing immobilized SCF or SDF1α, indicating enhanced cell spreading. By recapitulating aspects of the HSC microenvironment using a PEG hydrogel scaffold, we have shown the ability to control the adhesion and spreading of the 32D cells and demonstrated the potential of the system for the culture of primary hematopoietic cell populations.