Mitochondrial DNA aberrations of bone marrow cells from patients with aplastic anemia

Acquired and hereditary bone marrow failure: A mitochondrial perspective

The disorders known as bone marrow failure syndromes (BMFS) are life-threatening disorders characterized by absence of one or more hematopoietic lineages in the peripheral blood. Myelodysplastic syndromes (MDS) are now considered BMF disorders with associated cellular dysplasia. BMFs and MDS are caused by decreased fitness of hematopoietic stem cells (HSC) and poor hematopoiesis. BMF and MDS can occur de novo or secondary to hematopoietic stress, including following bone marrow transplantation or myeloablative therapy. De novo BMF and MDS are usually associated with specific genetic mutations. Genes that are commonly mutated in BMF/MDS are in DNA repair pathways, epigenetic regulators, heme synthesis. Despite known and common gene mutations, BMF and MDS are very heterogenous in nature and non-genetic factors contribute to disease phenotype. Inflammation is commonly found in BMF and MDS, and contribute to ineffective hematopoiesis. Another common feature of BMF and MDS, albeit less known, is abnormal mitochondrial functions. Mitochondria are the power house of the cells. Beyond energy producing machinery, mitochondrial communicate with the rest of the cells via triggering stress signaling pathways and by releasing numerous metabolite intermediates. As a result, mitochondria play significant roles in chromatin regulation and innate immune signaling pathways. The main goal of this review is to investigate BMF processes, with a focus mitochondria-mediated signaling in acquired and inherited BMF.

Angelica sinensis polysaccharide prevents mitochondrial apoptosis by regulating the Treg/Th17 ratio in aplastic anemia

Background

Angelica sinensis polysaccharide (ASP) is an effective medicine for aplastic anemia (AA). The present study aims to investigate whether mitochondrial apoptosis in aplastic anemia could be corrected by ASP by adjusting an abnormal level of regulatory T cell (Treg)/ IL-17 secreting CD4 T cell (Th17) ratio.

Methods

BALB/c mice were treated with 5.0 Gy Co60 γ -radiation. Then 2 × 10⁶ lymph node cells from DBA/2 donor mice were transplanted within 4 h after radiation. The mice in the various groups were fed saline or ASP for 2 weeks. For the in vitro experiment, bone marrow nucleated cells (BMNCs) and Treg cells were sorted from the mice on the 2nd day of modeling, and then cultured with or without ASP.

Results

The mice treated with the medium dose of ASP for 14 days showed increased white blood cell (WBC), red blood cell (RBC), platelet (PLT), BMNC counts and Lin–Sca-1 + c-Kit+ (LSK) populations viability compared with the mice in the AA group mice. The data showed that ASP decreased damage to the mitochondrial outer membrane, improved the stabilization of the mitochondrial membrane, and corrected the abnormal levels of ROS and mitochondrial-associated apoptosis proteins, including the Bcl-2/Bax ratio and caspase-3 and caspase-9 expression, in BMNCs which were sorted from the bone marrow cells of AA mice. The changes to the p-P38/P38 and Treg/Th17 ratios induced by AA were also reversed by the medium dose of ASP. The same ASP effect including the Bcl-2/Bax and p-P38/P38 ratio, caspase-3 and caspase-9 expression of BMNCs were observed in vivo. The viability of Treg cells were increased by treatment of ASP in vivo.

Conclusions

ASP might prevent mitochondrial apoptosis to restore the function of hematopoietic stem cells by suppressing abnormal T-cell immunity in AA.

Atad3a suppresses Pink1-dependent mitophagy to maintain homeostasis of hematopoietic progenitor cells

Although deletion of certain autophagy-related genes has been associated with defects in hematopoiesis, it remains unclear whether hyperactivated mitophagy affects the maintenance and differentiation of hematopoietic stem cells (HSCs) and committed progenitor cells. Here we report that targeted deletion of the gene encoding the AAA+-ATPase Atad3a hyperactivated mitophagy in mouse hematopoietic cells. Affected mice showed reduced survival, severely decreased bone-marrow cellularity, erythroid anemia and B cell lymphopenia. Those phenotypes were associated with skewed differentiation of stem and progenitor cells and an enlarged HSC pool. Mechanistically, Atad3a interacted with the mitochondrial channel components Tom40 and Tim23 and served as a bridging factor to facilitate appropriate transportation and processing of the mitophagy protein Pink1. Loss of Atad3a caused accumulation of Pink1 and activated mitophagy. Notably, deletion of Pink1 in Atad3a-deficient mice significantly 'rescued' the mitophagy defect, which resulted in restoration of the progenitor and HSC pools. Our data indicate that Atad3a suppresses Pink1-dependent mitophagy and thereby serves a key role in hematopoietic homeostasis.

Nutritional support contributes to recuperation in a rat model of aplastic anemia by enhancing mitochondrial function

OBJECTIVES

Acquired aplastic anemia (AA) is a hematopoietic stem cell disease that leads to hematopoietic disorder and peripheral blood pancytopenia. We investigated whether nutritional support is helpful to AA recovery.

METHODS

We established a rat model with AA. A nutrient mixture was administered to rats with AA through different dose gavage once per day for 55 d. Animals in this study were assigned to one of five groups: normal control (NC; group includes normal rats); AA (rats with AA); high dose (AA + nutritional mixture, 2266.95 mg/kg/d); medium dose (1511.3 mg/kg/d); and low dose (1057.91 mg/kg/d). The effects of nutrition administration on general status and mitochondrial function of rats with AA were evaluated.

RESULTS

The nutrient mixture with which the rats were supplemented significantly improved weight, peripheral blood parameters, and histologic parameters of rats with AA in a dose-dependent manner. Furthermore, we observed that the number of mitochondria in the liver, spleen, kidney, and brain was increased after supplementation by transmission electron microscopy analysis. Nutrient administration also improved mitochondrial DNA content, adenosine triphosphate content, and membrane potential but inhibited oxidative stress, thus, repairing the mitochondrial dysfunction of the rats with AA.

CONCLUSIONS

Taken together, nutrition supplements may contribute to the improvement of mitochondrial function and play an important role in the recuperation of rats with AA.

Direct confirmation of quiescence of CD34+CD38- leukemia stem cell populations using single cell culture, their molecular signature and clinicopathological implications

Background

The proliferating activity of a single leukemia stem cell and the molecular mechanisms for their quiescent property remain unknown, and also their prognostic value remains a matter of debate. Therefore, this study aimed to demonstrate the quiescence property and molecular signature of leukemia stem cell and their clinicopathological implications.

Methods

Single cell sorting and culture were performed in the various sets of hematopoietic stem cells including CD34+CD38- acute myeloid leukemia (AML) cell population (ASCs) from a total of 60 patients with AML, and 11 healthy controls. Their quiescence related-molecular signatures and clinicopathological parameters were evaluated in AML patients.

Results

Single cell plating efficiency of ASCs was significantly lower (8.6%) than those of normal hematopoietic stem cells i.e.: cord blood, 79.0%; peripheral blood, 45.3%; and bone marrow stem cell, 31.1%. Members of the TGFβ super-family signaling pathway were most significantly decreased; as well as members of the Wnt, Notch, pluripotency maintenance and hedgehog pathways, compared with non ASC populations. mtDNA copy number of ASCs was significantly lower than that of corresponding other cell populations. However, our data couldn’t support the prognostic value of the ASCs in AML.

Conclusions

ASCs showed remarkable lower plating efficiency and slower dividing properties at the single cell level. This quiescence is represented as a marked decrease in the mtDNA copy number and also linked with down-regulation of genes in various molecular pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1233-x) contains supplementary material, which is available to authorized users.

Mitochondrial DNA aberrations and pathophysiological implications in hematopoietic diseases, chronic inflammatory diseases, and cancers

Mitochondria are important intracellular organelles that produce energy for cellular development, differentiation, and growth. Mitochondrial DNA (mtDNA) presents a 10- to 20-fold higher susceptibility to genetic mutations owing to the lack of introns and histone proteins. The mtDNA repair system is relatively inefficient, rendering it vulnerable to reactive oxygen species (ROS) produced during ATP synthesis within the mitochondria, which can then target the mtDNA. Under conditions of chronic inflammation and excess stress, increased ROS production can overwhelm the antioxidant system, resulting in mtDNA damage. This paper reviews recent literature describing the pathophysiological implications of oxidative stress, mitochondrial dysfunction, and mitochondrial genome aberrations in aging hematopoietic stem cells, bone marrow failure syndromes, hematological malignancies, solid organ cancers, chronic inflammatory diseases, and other diseases caused by exposure to environmental hazards.

Adverse effects of antimicrobials via predictable or idiosyncratic inhibition of host mitochondrial components

This minireview explores mitochondria as a site for antibiotic-host interactions that lead to pathophysiologic responses manifested as nonantibacterial side effects. Mitochondrion-based side effects are possibly related to the notion that these organelles are archaic bacterial ancestors or commandeered remnants that have co-evolved in eukaryotic cells; thus, this minireview focuses on mitochondrial damage that may be analogous to the antibacterial effects of the drugs. Special attention is devoted to aminoglycosides, chloramphenicol, and fluoroquinolones and their respective single side effects related to mitochondrial disturbances. Linezolid/oxazolidinone multisystemic toxicity is also discussed. Aminoglycosides and oxazolidinones are inhibitors of bacterial ribosomes, and some of their side effects appear to be based on direct inhibition of mitochondrial ribosomes. Chloramphenicol and fluoroquinolones target bacterial ribosomes and gyrases/topoisomerases, respectively, both of which are present in mitochondria. However, the side effects of chloramphenicol and the fluoroquinolones appear to be based on idiosyncratic damage to host mitochondria. Nonetheless, it appears that mitochondrion-associated side effects are a potential aspect of antibiotics whose targets are shared by prokaryotes and mitochondria-an important consideration for future drug design.

Exploring the application of high-throughput genomics technologies in the field of maternal-embryo communication

Deciphering the complex molecular dialogue between the maternal tract and embryo is crucial to increasing our understanding of pregnancy failure, infertility problems and in the modulation of embryo development, which has consequences through adulthood. High-throughput genomic technologies have been applied to look for a holistic view of the molecular interactions occurring during this dialogue. Among these technologies, microarrays have been widely used, being one of the most popular tools in maternal-embryo communication. Today, next generation sequencing technologies are dwarfing the capabilities of microarrays. The application of these new technologies has broadened to almost all areas of genomics research, because of their massive sequencing capacity. We review the current status of high-throughput genomic technologies and their application to maternal-embryo communication research. We also survey next generation technologies and their huge potential in many research areas. Given the diversity of unanswered questions in the field of maternal-embryo communication and the wide range of possibilities that these technologies offer, here we discuss future perspectives on the use of these technologies to enhance maternal-embryo research.

Nutritional rehabilitation of mitochondrial aberrations in aplastic anaemia

Aplastic anaemia (AA) is a disease characterised by bone marrow hypocellularity and peripheral blood pancytopenia. AA is also associated with mitochondrial aberrations. The present study was undertaken primarily to test the hypothesis that a nutrient mixture could affect the nutritional rehabilitation of mitochondrial aberrations in AA mice. BALB/c AA mice were induced by a combination of hypodermic injections of acetylphenylhydrazine (100 mg/kg), X-rays (2·0 Gy) and intraperitoneal injections of cyclophosphamide (80 mg/kg). We treated these mice with nutrient mixture-supplemented diets in a dose-dependent manner (1445·55, 963·7, 674·59 mg/kg per d), and the effects of the nutrient mixture for mitochondrial rehabilitation were analysed in AA mice. Transmission electron microscopy showed that mitochondrial ultrastructural abnormalities in bone marrow cells, splenocytes and hepatocytes of the nutrient mixture groups were restored markedly, compared with the AA group. Mitochondrial membrane potentials of the nutrient mixture groups were increased remarkably. Western blot analysis also revealed that the nutrient mixture significantly inhibited cytochromecrelease of mitochondria in the AA group. Furthermore, the mitochondrial DNA content of the nutrient mixture groups was also increased. Our data suggest that the nutrient mixture may promote the rehabilitation of mitochondrial aberrations, and consequently protects against mitochondrial dysfunction in AA mice.