Do bone marrow fat cells or their precursors have a pathogenic role in idiopathic aplastic anaemia?

Differentiation of cancer cells upregulates HLA‑G and PD‑L1

A tumor contains special types of cells that have characteristics similar to stem cells that aid in tumor initiation, evasion and proliferation and are often resistant to chemotherapy. These cancer stem cells can be differentiated to eradicate their stemness and proliferative capacity by differentiating agents. This study investigated the effect of differentiation on the expression of two immune checkpoint inhibitors, human leukocyte antigen‑G (HLA‑G) and programmed death ligand‑1 (PD‑L1). Two cancer cell lines (OVCAR‑3‑NIH and KATO‑III) were treated with adipocyte and neurocyte differentiation media for 14 days. Bone‑marrow derived mesenchymal stem cells (BM‑MSCs) were used as control healthy stem cells. We found that the cancer cell lines (OVCAR‑3‑NIH and KATO‑III) when subjected to differentiation lost their proliferation ability. BM‑MSC proliferation was not halted but was decreased in the adipocyte differentiation media. There was no decrease in the CD90 stem cell marker in the BM‑MSCs; however, both cancer cell lines showed decreased CD90 stem cell marker. A significant increase in HLA‑G was noted for both the cancer cell lines following adipocyte differentiation. No effect was found for BM‑MSCs. Moreover, an increase in PD‑L1 in cancer cell lines was found following neurocyte differentiation. Moreover, we found that differentiation resulted in decreased PD‑L1 expression in BM‑MSCs. Differentiation therapy of cancer stem cells may result in increased immunosuppression ability, hence causing hindrance in the removal of cancer cells. Moreover, the differentiation of healthy stem cells can result in increased immunogenic reactivity owing to a decrease in PD‑L1 expression.

The Phenotype and Functional Activity of Mesenchymal Stromal Cells in Pediatric Patients with Non-Malignant Hematological Diseases

As the biology of mesenchymal stromal cells (MSCs) in patients with non-malignant hematological diseases (NMHD) is poorly understood, in the current study we performed a basic characterization of the phenotype and functional activity of NMHD-MSCs. Bone marrow (BM) of patients with thalassemia major (TM) possessed a significantly higher number of nucleated cells (BM-MNCs)/mL BM than healthy donors (P < 0.0001), which however did not result in a higher number of colony forming units-fibroblast (CFU-F) per milliliter BM. In contrast, from 1 × 10⁶ BM-MNCs of patients with sickle cell disease (SCD) were generated significantly more CFU-Fs than from TM-BM-MNCs (P < 0.013) and control group (P < 0.02). In addition, NMHD-MSCs expressed significantly lower levels of CD146 molecule, demonstrated an equal proliferation potential and differentiated along three lineages (osteoblasts, chondrocytes and adipocytes) as healthy donors’ MSCs, with exception of TM-MSCs which differentiated weakly in adipocytes. In contrast to other NMHD-MSCs and healthy donors’ MSCs, TM-MSCs demonstrated an impaired in vitro immunosuppressive potential, either. Noteworthy, the majority of the immunosuppressive effect of NMHD-MSCs was mediated through prostaglandin-E2 (PGE2), because indomethacin (an inhibitor of PGE2 synthesis) was able to significantly reverse this effect. Our results indicate therefore that NMHD-MSCs, except TM-MSCs, may be used as an autologous cell-based therapy for post-transplant complications such as graft failure, graft-versus-host disease (GvHD) and osteonecrosis.

Determinants of bone marrow adiposity: the modulation of peroxisome proliferator-activated receptor-γ2 activity as a central mechanism

Although the presence of adipocytes in the bone marrow is a normal physiological phenomenon, the role of these cells in bone homeostasis and during pathological states has not yet been fully delineated. As osteoblasts and adipocytes originate from a common progenitor, with an inverse relationship existing between osteoblastogenesis and adipogenesis, bone marrow adiposity often negatively correlates with osteoblast number and bone mineral density. Bone adiposity can be affected by several physiological and pathophysiological factors, with abnormal, elevated marrow fat resulting in a pathological state. This review focuses on the regulation of bone adiposity by physiological factors, including aging, mechanical loading and growth factor expression, as well as the pathophysiological factors, including diseases such as anorexia nervosa and dyslipidemia, and pharmacological agents such as thiazolidinediones and statins. Although these factors regulate bone marrow adiposity via a plethora of different intracellular signaling pathways, these diverse pathways often converge on the modulation of the expression and/or activity of the pro-adipogenic transcription factor peroxisome proliferator-activated receptor (PPAR)-γ2, suggesting that any factor that affects PPAR-γ2 may have an impact on the fat content of bone.

The relationship between adipose tissue and bone metabolism

OBJECTIVES

The authors have set out to evaluate the literature relevant to the dynamic regulation of adipogenesis and osteogenesis.

DESIGN AND METHODS

A detailed search of the past and recent literature was conducted on Pubmed using a combination of keywords including: adipogenesis, bone marrow, hematopoiesis, mesenchymal stromal/stem cell, and osteogenesis.

RESULTS

Throughout one's lifespan, the bone marrow microenvironment provides a unique niche for mesenchymal stromal/stem cells (BMSCs) and hematopoietic stem cells (HSCs). The marrow changes as a function of biological age and pathophysiology. Historically, clinical biochemistry has observed these changes from an HSC and hematological perspective. Nevertheless, these changes also reflect the balance between BMSC adipogenic and osteogenic processes which can display an inverse or reciprocal relationship. Multiple hormonal factors and nuclear hormone receptor ligands and drugs are responsible for BMSC lineage selection. Data from a number of laboratories now implicates endocrine feedback loops between extramedullary adipose depots and the central nervous system.

CONCLUSIONS

This concise review provides a perspective on the mechanisms regulating BMSC differentiation in the context of biological aging, obesity, and osteoporosis.

Abnormal immunity and stem/progenitor cells in acquired aplastic anemia

Acquired aplastic anemia (AA) is considered as an immune-mediated bone marrow failure syndrome, characterized by hypoplasia and pancytopenia with fatty bone marrow. Abnormal immunity is the major factor mediating the pathogenesis of acquired AA. Activated DCs might promote the polarization to Th1 cells, and activate CD8(+) T cells. A variety of immune molecules including IFN-gamma, TNF-alpha, MIP-1alpha and IL-2, 8, 12, 15, 17, 23, produced by them and stromal cells, compose a cytokine network to destruct stem/progenitor cells as well as hematopoietic stem/progenitor cells, mesenchymal stem cells (MSCs) and angioblasts/endothelial progenitor cells. Inversely, deficient MSCs, CD4(+)CD25(+) T cells, NK cells, NKT cells and early hematopoietic growth factors diminish the capacity of immune regulation and the support of hematopoiesis. As a result, stem/progenitor cells are significantly impaired to be disabled cells with markedly deficient proliferation, differentiation, induced apoptosis and dysfunctional response to growth factor stimuli, together with rare normal ones. Although some patients can be ameliorated by stem-cell transplantation or immunosuppressive therapy, more effective and convenient therapies such as patient-specific pluripotent iPS cells based on definite pathogenesis are expected.

Anemia of immobility: caused by adipocyte accumulation in bone marrow

Anemia of chronic disease has long been used to classify a non-regenerative, low-grade, chronic, normocytic, normochromic anemia that presents with no obvious etiology. Within this group, some patients have a chronic inflammatory condition that limits erythrocyte generation or access to iron stores. This specific type of anemia has been termed anemia of chronic inflammation. However, a substantial remainder of patients diagnosed with anemia of chronic disease present with no active inflammation. These include many clinical populations with reduced limb loading, such as spinal cord injured patients, astronauts, elderly people with limited mobility and experimental bed-rest subjects. In some populations with decreased mobility, accumulation of fat in the bone marrow has been demonstrated. We hypothesize that adipocyte accumulation in bone marrow both passively and actively impairs erythropoiesis and thus defines a new type of anemia called anemia of immobility. The non-specific umbrella term anemia of chronic disease thus becomes obsolete in favour of either the diagnosis of anemia of immobility or anemia of chronic inflammation according to the distinct mechanism involved.

Aging and carcinogenesis--insufficient metabolic cell repair as the common link

BACKGROUND

The mechanisms of the development of cancer in old age and also the mechanisms of aging are not well understood. This paper tries to interpret consequences of malignant tissue transformation from the viewpoint of aging, or in other words, from an insufficient cell adaptation to the needs of repair and proliferation.

SUBJECT

A hypothesis is presented that a unified but quite opposite at different stages of ontogenesis mechanism is the basis of atypical growth and embryonic development. In the beginning of a malignant dedifferentiation is an insufficiency of an effective self-renovation and disturbed preservation of its adaptation capability. The suppression of regenerating cell proliferation is the primary event of the development of a dedifferentiated tissue growth. The transformation of normal cells into tumor cells is an adaptive reaction in reply to a shortage of self-regeneration capability and repair. Allowing for the process of rebirth, i.e. the complete restoration of tissues leading to the restrain of senescence proceeds by the type of embryonic growth of tissues, the possibility to use the potential of transformed cells for restraining senescence is proposed. The latter will permit to direct the process of transformation to an integrated growth channel, to prevent the clinical phenomenon of malignancy, and use the potential of transformed cells for realization of the self-renovation program and program of unlimited life duration of the whole organism.

CONCLUSION

By a stimulation or compensation of the age-induced shortage of cell metabolism, two effects can be expected: prevention of cancer and retardation of aging.

Adipogenesis in a murine bone marrow stromal cell line capable of supporting B lineage lymphocyte growth and proliferation: biochemical and molecular characterization

Recent advances in long-term bone marrow (BM) culture techniques have allowed investigators to dissect cellular components responsible for lympho hematopoiesis. Consequently, a number of "stromal" cell clones have been developed which are capable of supporting B lineage lymphocyte growth and proliferation in vitro by direct cell-cell interactions and the release of cytokines. While much work has focused on the support function of these cells, questions remain regarding their own differentiation potential. We have examined adipogenesis in the cloned BM stromal cell, BMS2. The presence of hydrocortisone, methylisobutylxanthine, or 30% fetal calf serum each accelerated adipocyte differentiation. This process was accompanied by the accumulation of triglycerides and cholesterol esters along with the induction of adipocyte-specific enzymes. Likewise, the steady-state level of mRNA transcripts increased for genes related to lipid metabolism. However, the pattern of mRNA expression in BMS2 adipocytes differed from that of a well-established, pre-adipocyte cell line, 3T3-L1, with respect to the following genes: glycerol phosphate dehydrogenase, CAAT/enhancer binding protein and angiotensinogen. Adipocyte BMS2 cells retailed the ability to support stromal cell-dependent B lineage lymphocytes in methylcellulose assays. The adipocytes continued to express macrophage-colony-stimulating factor mRNA constitutively and interleukin 6 mRNA in an inducible manner, similar to the BMS2 pre-adipocytes. Together, these data document a close developmental relationship between a specialized fibroblasts and adipocytes in the BM and suggest that adipocyte stromal cells may play an active role in lympho-hematopoiesis.