Increased Bone Marrow Research Articles

Postmenopausal Osteoporosis and Osteopenia Management with a Combination of Once-Monthly Oral Ibandronate and Cholecalciferol—A Systematic Review

Postmenopausal osteoporosis and osteopenia are chronic and uncurable conditions that invariably lead to an increased risk of vertebral, hip, and femoral neck fracture if left untreated. Clinical guidelines establish, in general, pharmacological combinations allied to lifestyle changes as the mainstay of their management, and also increasing bone marrow density, lowering fracture risk, and improving quality of life are their main therapeutic goals. The objective of this systematic review was to analyze the available data in the scientific medical literature regarding the role of the ibandronate and cholecalciferol combination in postmenopausal osteoporosis and osteopenia management. Based on our results, we concluded that the above combination is safe and feasible for the clinical control of both conditions.

Adipocytes control hematopoiesis and inflammation through CD40 signaling.

The co-stimulatory CD40-CD40L dyad plays an important role in chronic inflammatory diseases associated with aging. Although CD40 is mainly expressed by immune cells, CD40 is also present on adipocytes. We aimed to delineate the role of adipocyte CD40 in the aging hematopoietic system and evaluated the effects of adipocyte CD40 deficiency on cardiometabolic diseases. Adult adipocyte CD40-deficient mice (AdiCD40KO) mice had a decrease in bone marrow hematopoietic stem cells (Lin-Sca+cKit+, LSK) and common lymphoid progenitors, which was associated with increased bone marrow adiposity and T-cell activation, along with elevated plasma corticosterone levels, a phenotype that became more pronounced with age. Atherosclerotic AdiCD40koApoE-/- (CD40AKO) mice also displayed changes in the LSK population, showing increased myeloid and lymphoid multipotent progenitors, and augmented corticosterone levels. Increased T-cell activation could be observed in bone marrow, spleen, and adipose tissue, while the numbers of B cells were decreased. Although atherosclerosis was reduced in CD40AKO mice, plaques contained more activated T cells and larger necrotic cores. Analysis of peripheral adipose tissue in a diet-induced model of obesity revealed that obese AdiCD40KO mice had increased T-cell activation in adipose tissue and lymphoid organs, but decreased weight gain and improved insulin sensitivity, along with increased fat oxidation. In conclusion, adipocyte CD40 plays an important role in maintaining immune cell homeostasis in bone marrow during aging and chronic inflammatory diseases, particularly of the lymphoid populations. Although adipocyte CD40 deficiency reduces atherosclerosis burden and ameliorates diet-induced obesity, the accompanying T-cell activation may eventually aggravate cardiometabolic diseases.

Disrupted Lipid Homeostasis and Loss of IRF4 Impairs B-Cell and Plasma Cell Development in a Murine Model of Accelerated Aging

The aging immune system is characterized by increased bone marrow (BM) adiposity, myeloid skewing, impaired lymphocyte maturation, and loss of hematopoietic stem and progenitor cell (HSPC) regenerative capacity. Human systemic aging studies have found alterations in lipid and fatty acid metabolism, such as increased saturated fatty acid accumulation and decays in n-3 polyunsaturated fatty acid (PUFA) species leading to cellular membrane rigidity. However, the extent to which impaired fatty acid metabolism contributes to immune system aging and HSPC development is largely unexplored. In this study, we performed multi-omics studies to characterize BM aging phenotypes in a recently described mouse model that exhibits signs of accelerating aging in brain and eye tissues. This robust aging model expresses a mutant inactive form of the very long chain (VLC) PUFA elongation enzyme, Elongation of very long chain fatty acids protein 2 (ELOVL2), which is responsible for the elongation of 22-carbon PUFAs to 24-carbon PUFAs. These VLC-PUFAs are synthesized in vivo and are not readily available through dietary means. Previous studies using this mouse model demonstrated that Elovl2 DNA methylation-dependent and mutation-associated loss of function is a key driver of age-related defects in eye and brain tissues, however the hematopoietic system has not been characterized to date in this model. To investigate the extent to which impaired VLC-PUFA production in the setting of ELOVL2 enzymatic deficiency might also accelerate blood stem cell aging phenotypes, multi-omics studies were performed in murine BM samples from young (3 months old) and aged (18 months old) wild-type mice, compared with age-matched Elovl2 mutant mice. Total BM samples were subjected to lipidomics analyses, whole transcriptome RNA-sequencing (RNA-seq), and ATAC-seq analyses. Lipidomic profiling showed an almost complete depletion of direct and secondary products of ELOVL2 in BM isolated from mutant animals, suggesting significant changes in the biophysical properties of membranes in the cells. Gene set enrichment analyses (Reactome) of RNA-seq data revealed that pathways involving B cell receptor (BCR) signalling and immunoregulatory interactions between lymphoid and non-lymphoid cells were among the most differentially regulated in Elovl2 mutant mouse BM compared to age-matched controls. Key lymphoid lineage maturation markers (Cd19, Cd22, and Slamf7, among others) were downregulated in the BM of aged wild-type mice, and to a greater extent in Elovl2 mutant animals. This was accompanied by a significant downregulation of the lymphoid and plasma cell transcription factor, interferon-regulatory factor-4 (Irf4), in aged and Elovl2 mutant groups compared with young mice. In addition, phenotypic analyses of B cell lineage marker protein expression were performed by flow cytometry to confirm depletion of lymphoid cell populations and Irf4 expression in this model. Finally, ATAC-seq data revealed changes in DNA accessibility related to Elovl2 mutation, suggesting significant epigenetic changes in nuclear programs. These findings suggest that Elovl2 loss of function in a murine model of accelerated aging promotes diverse lipidomic, transcriptomic and chromatin alterations targeting lymphoid populations in murine BM, which may be mechanistically driven by a downregulation of Irf4. Together, these results provide insights into a functional link between disrupted lipid homeostasis and aging-related defects in lymphocyte maturation typified by loss of B-cell and plasma cell populations. Together, modulation of lipid catabolism pathways may provide a novel avenue for reversing a variety of age-related immune deficits including enhanced susceptibility to infection.

Disease Progression and Leukemic Transformation in Patients With Lower-Risk Myelofibrosis (MF): An Analysis from MOST

Background: Progressive disease (PD) in MF is associated with increased bone marrow fibrosis, worsening anemia, and an increase in circulating blasts and can result in leukemic transformation (LT). LT is a rare (~11% incidence) but fatal complication of MF with a mortality rate of 97% and a median survival of 3.6 months. Real-world data regarding PD and LT in lower-risk MF are limited. This analysis from the Myelofibrosis and Essential Thrombocythemia Observational Study (MOST; NCT02953704) describes the incidence of PD, including LT, in patients with lower-risk MF and compares the baseline characteristics of patients who progressed vs those who did not. Methods: MOST is a longitudinal, noninterventional, prospective, observational study of patients with clinical diagnoses of MF or essential thrombocythemia enrolled at clinical practices in the US. Patients included in this analysis (≥18 years) had low-risk or intermediate-1 (INT-1)-risk MF (by age >65 years alone) stratified by the Dynamic International Prognostic Scoring System (Blood. 2010;115:1703) at enrollment and were followed for at least 3 years. Baseline data were collected as previously described (Gerds A. Clin Lymphoma Myeloma Leuk. 2022;22:e532-e540). PD was defined as physician-reported PD, LT, and/or death by reason of progression. Results: Of the 232 patients with MF enrolled in MOST, 204 patients (low-risk: n=84, 41.2%; INT-1-risk: n=120, 58.8%) were included in this analysis (data cutoff: July 5, 2022). The median (range) time from MF diagnosis to enrollment was 1.8 (0-38) years and the median (range) enrollment duration was 4.2 (3.3-5.4) years. Of 193 patients with available data on disease progression, 46 patients (23.8%) had physician-reported PD; of these, 18 (22.0%) were low-risk and 28 (25.2%) were INT-1-risk. The most commonly reported indicator was change in hematologic parameters (n=27 [58.7%]), followed by change in spleen size (n=19 [41.3%]), MF-related symptoms (n=16 [34.8%]), and blast counts (n=8 [17.4%]). LT was reported in 15 patients (7.8%); of these 4 (4.9%) were low-risk and 11 (9.9%) were INT-1-risk. Death by any cause was reported in 30 patients (14.7%; PD, n=16, without PD, n=9; unknown PD, n=5). Patient baseline characteristics are shown in Table 1. Patients who had PD were older than patients without (median [range] age: PD, 70.0 [35-88] vs without PD, 66.5 [35-88] years). Bone marrow biopsy/aspiration and mutation tests at diagnosis were reported in 98.3% and 80.7% of patients with PD and in 91.8% and 82.8% of patients without PD, respectively. Significant differences in the symptomatology of patients with PD vs without PD were not detected at time of enrollment. More than half of patients with PD and without PD were receiving MF-directed monotherapy at enrollment (59.3% vs 55.2%). The most common monotherapies received in patients with PD vs without PD were hydroxyurea (15.3% vs 28.4%) and ruxolitinib (37.3% vs 17.9%). Six patients (PD, n=3; without PD, n=3) received >1 MF-directed therapy. Conclusion: This real-world analysis of data from patients enrolled in MOST describes the disease evolution of patients with lower-risk MF. After ~3 years of follow-up, a relatively high proportion of patients in this population had physician-reported PD or LT (23.8% and 7.8%, respectively). Baseline characteristics and symptoms did not differ between those who progressed and those who did not; however, further analysis of molecular and post-baseline data may provide insight into risk factors for disease progression in this lower-risk population. Identification of patients with higher risk of PD is likely to improve disease management and outcomes for patients with lower-risk MF. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The Long Non-Coding RNA MALAT1 Is Necessary for Hematopoietic Stem and Progenitor Cell Expansion and Preleukemic Myeloproliferation in TET2 Deficient Myeloid Neoplasms

Ten Eleven Translocation 2 (TET2) is a dioxygenase which regulates gene expression by oxidizing 5-methylcytosine to 5-hydroxymethylcytosine. Loss of function mutations in TET2 occur in up to 58% and 30% of myeloid malignancies and clonal hematopoiesis respectively. Loss of TET2 function also occurs with isocitrate dehydrogenase 2 (IDH2) mutations in Acute Myeloid Leukemia (AML) via 2-hydroxyglutarate (2-HG). Genetically engineered murine models (GEMM) of Tet2 deficiency produce a Chronic Myelomonocytic Leukemia (CMML)-like phenotype with splenomegaly, granulomonocytic expansion and increased bone marrow hematopoietic stem and progenitors (LSK). Further, bone marrow mononuclear cell (BMNC) transplant models of Tet2-/- clonal hematopoiesis suggest that this myeloid expansion leads to enhanced inflammation and increased cardiovascular disease risk. However, the downstream effects of TET2 loss of function leading to this phenotype are unknown. Here we show that TET2-deficient granulomonocytic expansion and inflammation are mediated via MALAT1, a long non-coding RNA overexpressed in several malignancies. MALAT1 expression was increased in BMNCs from IDH2 mutated AML patients (n=152 WT n=17 mutant IDH2, p=0.04). Increased MALAT1 expression was also seen in human and murine models of TET2 deficiency including isogenic IDH2 mutated TF-1 cells (5 biological replicates p=0.005), 2-HG treated leukemia cell lines (2 biological replicates p<0.0001) and BMNCs from Tet2f/f mice (n= 7/grp p=0.005). To evaluate the impact of Malat1 on normal and Tet2 deficient hematopoiesis we utilized the Malat1tg overexpression and Tet2-/-Malat1-/-GEMM models. Similar to Tet2-/- mice, bone marrow (n=4/grp p=0.02) and spleen (n=8/grp p=0.004) LSK numbers were increased in Malat1tg mice compared to control. However, unlike Tet2-/-LSKs, MALAT1tgLSKs did not show increased self-renewal in serial in vivo competitive transplants. Further, depleting Malat1 in Tet2-/- mice did not rescue the increased self-renewal capacity seen in Tet2-/- LSKs. Collectively, these data suggest that Malat1 overexpression is sufficient for LSK expansion but does not impact LSK function. Splenomegaly, myeloproliferation and extramedullary hematopoiesis is a phenotype termed Preleukemic Myeloproliferation (PMP) and is predictive of myeloid neoplasm development in Tet2-/- models (Meisel M et al, Nature 2018). Consistent with a role of Malat1 in PMP (Fig A), Malat1 overexpression recapitulated PMP at 8 (n=10/grp p<0.0001) and 20 (n=10/grp p=0.0005) weeks. Malat1 overexpression was also associated with an increase in classical monocytes in the peripheral blood- a hallmark of CMML (8 weeks n= 7/grp p<0.0001, 20 weeks n=10/grp p=0.0007). This was recapitulated in Tet2-/-mice (n=3/grp p=0.001) and CMML patients with TET2 mutations (n=27 mutant TET2 v 109 WT, odds ratio 5.6 p= 0.001). Finally, depleting Malat1 in a Tet2-deficient GEMM rescued PMP (n=4 Tet2-/-Malat1-/-v 5 Tet2-/-p=0.01) and classical monocytosis (n=2/grp p=0.002) suggesting that Malat1 overexpression is both sufficient and necessary for PMP in Tet2 deficient leukemia. This impact was also observed in recipients in BMNC competitive transplant experiments (Fig B). Initial insights into the molecular mechanism underlying the role of Malat1 in PMP were derived from analyzing competitor and host cells during in vivo competitive transplants. Interestingly, transplant recipients with Malat1tg LSK demonstrated myeloid and granulomonocytic expansion in both donor and non-donor cells suggesting that the effects of Malat1 overexpression are, in part, cell extrinsic. Consistent with this hypothesis and the impact of NF-kB on inflammatory cytokine secretion and Tet2-/- PMP, we show that MALAT1 deletion in human leukemia attenuates NF-kB activity by enhancing the phosphatase activity of PP2A. Further, Interleukin 6 (IL-6), a major downstream target of NF-kB and potent activator of myelopoiesis in response to inflammatory stimuli, was increased in the plasma of MALAT1tg mice (n=8/grp p=0.01) suggesting a possible cell-extrinsic mechanism for Malat1 dependent PMP. Ongoing studies are focused on demonstrating that IL-6 is necessary for Malat1 dependent PMP. Our current data provides hitherto unknown insights establishing MALAT1 as a major effector of TET2 loss of function which may lead to novel therapeutic options in TET2 deficient myeloid neoplasms. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Bone Sialoprotein Is Critical for Alveolar Bone Healing in Mice

Bone sialoprotein (BSP) is an extracellular matrix (ECM) protein associated with mineralized tissues, particularly bone and cementum. BSP includes functional domains implicated in collagen binding, hydroxyapatite nucleation, and cell signaling, although its function(s) in osteoblast and osteoclast differentiation and function remain incompletely understood. Genetic ablation of BSP in Ibsp knockout (Ibsp–/–) mice results in developmental bone mineralization and remodeling defects, with alveolar bone more severely affected than the femurs and tibias of the postcranial skeleton. The role of BSP in alveolar bone healing has not been studied. We hypothesized that BSP ablation would cause defective alveolar bone healing. We employed a maxillary first molar extraction socket healing model in 42-d postnatalIbsp–/– and wild-type (WT) control mice. Tissues were collected at 0, 7, 14, 21, and 56 d postprocedure (dpp) for analysis by micro–computed tomography (microCT), histology, in situ hybridization (ISH), immunohistochemistry (IHC), and quantitative polymerase chain reaction (qPCR) array. As expected, alveolar bone healing progressed in WT mice with increasing bone volume fraction (BV/TV), bone mineral density (BMD), and tissue mineral density (TMD), transitioning from woven to mature bone from 7 to 56 dpp. Ibsp messenger RNA (mRNA) and BSP protein were strongly expressed during alveolar bone healing in parallel with other osteogenic markers. Compared to WT, Ibsp–/– mice exhibited 50% to 70% reduced BV/TV and BMD at all time points, 7% reduced TMD at 21 dpp, abnormally increased Col1a1 and Alpl mRNA expression, and persistent presence of woven bone and increased bone marrow in healing sockets. qPCR revealed substantially dysregulated gene expression in alveolar bone of Ibsp–/– versus WT mice, with significantly disrupted expression of 45% of tested genes in functional groups, including markers for osteoblasts, osteoclasts, mineralization, ECM, cell signaling, and inflammation. We conclude that BSP is a critical and nonredundant factor for alveolar bone healing, and its absence disrupts multiple major pathways involved in appropriate healing.

Assessing organ-level immunoreactivity in a rat model of sepsis using TSPO PET imaging.

There is current need for new approaches to assess/measure organ-level immunoreactivity and ensuing dysfunction in systemic inflammatory response syndrome (SIRS) and sepsis, in order to protect or recover organ function. Using a rat model of systemic sterile inflammatory shock (intravenous LPS administration), we performed PET imaging with a translocator protein (TSPO) tracer, [18F]DPA-714, as a biomarker for reactive immunoreactive changes in the brain and peripheral organs. In vivo dynamic PET/CT scans showed increased [18F]DPA-714 binding in the brain, lungs, liver and bone marrow, 4 hours after LPS injection. Post-LPS mean standard uptake values (SUVmean) at equilibrium were significantly higher in those organs compared to baseline. Changes in spleen [18F]DPA-714 binding were variable but generally decreased after LPS. SUVmean values in all organs, except the spleen, positively correlated with several serum cytokines/chemokines. In vitro measures of TSPO expression and immunofluorescent staining validated the imaging results. Noninvasive molecular imaging with [18F]DPA-714 PET in a rat model of systemic sterile inflammatory shock, along with in vitro measures of TSPO expression, showed brain, liver and lung inflammation, spleen monocytic efflux/lymphocytic activation and suggested increased bone marrow hematopoiesis. TSPO PET imaging can potentially be used to quantify SIRS and sepsis-associated organ-level immunoreactivity and assess the effectiveness of therapeutic and preventative approaches for associated organ failures, in vivo.

Ipilimumab plus decitabine for patients with MDS or AML in posttransplant or transplant-naïve settings

Two articles in this week’s issue focus on the use of ipilimumab and decitabine for patients with myelodysplasia (MDS) and acute myeloid leukemia (AML) before and after hematopoietic stem cell transplantation (HSCT) for high-risk disease. In the first article, Garcia et al report on the results of a phase 1 trial of the combination in 54 patients, demonstrating overall response rate of 52% in patients who are HSCT-naïve and 20% in patients post-HSCT; responses are usually short-lived. In the second article, Penter and colleagues characterize gene expression responses to therapy and conclude that decitabine acts directly to clear leukemic cells while ipilimumab acts on infiltrating lymphocytes in marrow and extramedullary sites. Responses are determined by leukemic cell burden and by the frequency and phenotype of infiltrating lymphocytes. Increasing bone marrow regulatory T cells is identified as a potential contributor to checkpoint inhibitor escape.

A novel use of CT attenuation value: increased bone marrow density in patients with acute myeloid leukemia.

Acute myeloid leukemia (AML) is the most common type of acute leukemia in adults. Bone marrow computed tomography (CT) attenuation may increase in patients with myeloproliferative disorders; however, the actual threshold CT attenuation value predictive of myeloproliferative has not been reported. To determine whether the unenhanced CT attenuation value of the bone marrow may be useful for predicting AML. We retrospectively analyzed patients with AML (n = 56) who underwent unenhanced CT before treatment, and age- and sex-matched controls without any hematologic disease. For each patient, the CT attenuation value (HU) of the iliac bone was measured and compared between the two groups. Receiver operating characteristic (ROC) curve analysis was used to define the cutoff value for predicting AML on all patients, and only on late elderly patients (aged ≥75 years). Patients with AML showed higher bone marrow CT attenuation value (131.4 ± 58.3 vs. 53.9 ± 67.2 HU; P < 0.001), compared to the controls. The sensitivity and specificity for the diagnosis of AML in all patients were 78.6% and 80.4%, respectively, at a threshold value of 90 HU, whereas they were 83.3% and 91.7%, respectively, at 40 HU in late elderly patients. The iliac bone CT attenuation value was elevated in patients with AML and may be useful for predicting AML.

Administration of nitro-oleic acid mitigates radiation-induced hematopoietic injury in mice

AimsLimited number of agents that provide protection against hematopoietic acute radiation syndrome led us to the evaluation of nitro-oleic acid (NO2OA) as a potential protector/mitigator against radiation-induced hematopoietic injury in C57/BL6 mice. Materials and methodsNO2OA was administered before and after sub-lethal total body irradiation (TBI) and hematological parameters were evaluated 3 or 7 days after TBI. Key findingsOur results show that NO2OA significantly increase bone marrow cellularity including the granulocyte-macrophage colony-forming cells and erythroid progenitors on the 3rd day after TBI. In addition, NO2OA enhanced recovery of white blood cells (lymphocytes, neutrophils, and monocytes) in peripheral blood 7 days after irradiation. These effects may be in part attributed to NO2OA-induced granulocyte colony-stimulating factor production after TBI. On the other hand, radiation-induced impairment of peripheral red blood cells, hemoglobin, and platelets were not affected with NO2OA treatment up to 7 days post TBI. SignificanceIn conclusion, our data show that NO2OA significantly protects hematopoiesis after irradiation, and thus showed a high potential to act as an agent for medical radiation countermeasure.

Nanoparticles of naturally occurring PPAR-γ inhibitor betulinic acid ameliorates bone marrow adiposity and pathological bone loss in ovariectomized rats via Wnt/β-catenin pathway

AimsPostmenopausal osteoporosis is one of the world's biggest yet unnoticed health issues. After ovariectomy, declined estrogen level significantly contributes to the elevation of bone marrow adiposity and bone loss leading to osteoporosis. Therapeutics to prevent osteoporosis addressing various aspects are now in short supply. In this study we made an approach to synthesize nanoparticles of naturally occurring PPAR-γ inhibitor, betulinic acid (BA/NPs) and tested the same in altered bone metabolisms developed after ovariectomy. Main methodsThe osteogenic efficacy of BA/NPs was established in human and rat primary osteoblast cells using qRT-PCR and immunoblot analysis. Furthermore, lineage allocations of multipotent bone marrow stromal cells were evaluated. Various aspects of altered bone metabolism after ovariectomy such as bone marrow adiposity and pathological bone loss were evaluated using μCT and histological assessments. Key findingsBA/NPs exert potential osteogenic efficacy by modulating key osteogenic markers such as RUNX2 and BMP2. Mechanistically BA/NPs regulate osteoblastogenesis through Wnt/β-catenin signaling. Further, BA/NPs showed the potential to inhibit the differentiation of multipotent BMSCs towards adipogenesis while favouring the osteogenic lineage via Wnt/β-catenin pathway. In the in vivo study, increased bone marrow adiposity was reduced in ovariectomized rats after BA/NPs treatment as assessed by histology and μCT analysis. Loss of bone mineral density as a hallmark of pathological bone loss was also abrogated by BA/NPs. Furthermore, increased obesity after OVX was also prevented in BA/NPs treated animals. SignificanceOur findings imply that BA/NPs could be used further as a viable drug lead to counteract various pathophysiological challenges after menopause.

Diagnostic value of delta neutrophil index in determining axillary metastases in breast cancer

Aim: The delta neutrophil index (DNI), which shows the percentage of immature granulocytes (IG) in peripheral blood in inflammatory conditions, is an indicator of increased bone marrow activation. Its ability to predict prognosis has been demonstrated in many cancer studies. This study aims to investigate the value of DNI in predicting axillary metastases in breast cancer.&#x0D; Material and Method: Patients diagnosed with breast cancer and operated on axillary lymph node dissection were screened and 127 patients were included in the study. The patient’s age, gender, operation time, length of hospital stay, immature granulocyte (IG) percentages (IG#), and axillary lymph node pathology results were retrospectively scanned from the archive system.&#x0D; Results: DNI and IG were statistically higher in the group with lymph node metastasis. When examined for IG#, the mean of the group with reactive lymph nodes was 0.02±0.02, while the mean of the metastatic group was 0.04±0.05. This statistically significant difference was high (p

The pathophysiology of osteoporosis in obesity and type 2 diabetes in aging women and men: The mechanisms and roles of increased bone marrow adiposity.

Osteoporosis is defined as a systemic skeletal disease characterized by decreased bone mass and micro-architectural deterioration leading to increased fracture risk. Osteoporosis incidence increases with age in both post-menopausal women and aging men. Among other important contributing factors to bone fragility observed in osteoporosis, that also affect the elderly population, are metabolic disturbances observed in obesity and Type 2 Diabetes (T2D). These metabolic complications are associated with impaired bone homeostasis and a higher fracture risk. Expansion of the Bone Marrow Adipose Tissue (BMAT), at the expense of decreased bone formation, is thought to be one of the key pathogenic mechanisms underlying osteoporosis and bone fragility in obesity and T2D. Our review provides a summary of mechanisms behind increased Bone Marrow Adiposity (BMA) during aging and highlights the pre-clinical and clinical studies connecting obesity and T2D, to BMA and bone fragility in aging osteoporotic women and men.

Knockdown of CDC20 promotes adipogenesis of bone marrow-derived stem cells by modulating β-catenin

BackgroundBone is a rigid organ that provides physical protection and support to vital organs of the body. Bone loss disorders are commonly associated with increased bone marrow adipose tissue. Bone marrow mesenchymal stromal/stem cells (BMSCs) are multipotent progenitors that can differentiate into osteoblasts, adipocytes, and chondrocytes. Cell division cycle 20 (CDC20) is a co-activator of anaphase promoting complex/cyclosome (APC/C), and is required for ubiquitin ligase activity. Our previous study showed that CDC20 promoted the osteogenic commitment of BMSCs and Cdc20 conditional knockout mice suggested a decline in bone mass. In this study, we found that knockdown of CDC20 promoted adipogenic differentiation of BMSCs by modulating β-catenin, which suggested a link between adipogenesis and osteogenesis.MethodsLentivirus containing a CDC20 shRNA was used for CDC20 knockdown in human BMSCs (hBMSCs). Primary mouse BMSCs (mBMSCs) were isolated from Cdc20f/f and Sp7-Cre;Cdc20f/f mice. Adipogenesis was examined using quantitative real-time reverse transcription PCR (qRT-PCR) and western blotting analysis of adipogenic regulators, Oil Red O staining, and transplantation into nude mice. CDC20 knockout efficiency was determined through immunochemistry, qRT-PCR, and western blotting of bone marrow. Accumulation of adiposity was measured through histology and staining of bone sections. Exploration of the molecular mechanism was determined through western blotting, Oil Red O staining, and qRT-PCR.ResultsCDC20 expression in hBMSCs was significantly decreased during adipogenic differentiation. CDC20 knockdown enhanced hBMSC adipogenic differentiation in vitro. CDC20-knockdown hBMSCs showed more adipose tissue-like constructs upon hematoxylin and eosin (H&E) and Oil Red O staining. Sp7-Cre;Cdc20f/f mice presented increased adipocytes in their bone marrow compared with the control mice. mBMSCs from Sp7-Cre;Cdc20f/f mice showed upregulated adipogenic differentiation. Knockdown of CDC20 led to decreased β-catenin levels, and a β-catenin pathway activator (lithium chloride) abolished the role of CDC20 in BMSC adipogenic differentiation.ConclusionsOur findings showed that CDC20 knockdown enhanced adipogenesis of hBMSC and mBMSCs adipogenesis in vitro and in vivo. CDC20 regulates both adipogenesis and osteogenesis of BMSCs, and might lead to the development of new therapeutic targets for “fatty bone” and osteoporosis.

Bone marrow adiposity in pediatric Crohn's disease.

Patients with Crohn's disease often have low bone mineral density and an increased risk of osteoporosis. Although decreased bone formation can be seen at diagnosis, the underlying pathophysiology of suboptimal bone accrual remains poorly understood. We sought to evaluate a novel mechanism affecting osteogenesis in patients with Crohn's disease. In this case series, we evaluated bone marrow composition at the distal femur and proximal tibia of the left knee measured via magnetic resonance (MR) spectroscopy and relaxometry in five adolescents with the diagnosis of Crohn's disease. The subjects were enrolled prospectively between 2011 and 2013 at Boston Children's Hospital. Additional clinical information, including DXA scans to evaluate bone mineral density and body composition, and Crohn's disease history, such as glucocorticoid use and disease duration, were assessed. Healthy adolescents have persistent hematopoietic marrow with only 40 to 50% fat in the long bone metaphyses. The current participants with Crohn's disease had increased marrow adiposity, with a mean fat fraction of 67.8%. There appeared to be a trend towards higher fat fraction with shorter disease duration, while participants with the longest disease duration had the lowest fat fraction. Participants also had decreased bone density, increased fat mass, and lower lean mass, as assessed by DXA and compared to pediatric reference data. Our MRI results demonstrate increased marrow adiposity in children with Crohn's disease, especially early in the course of the disease. DXA may better demonstrate longer-term effects on bone. Additional studies are needed to evaluate bone marrow composition in these patients and to elucidate further the inverse relationship between marrow adipocytes and osteogenesis, as well as the relationship between bone marrow adiposity and body composition.

Effects of Extracellular Vesicles from Osteogenic Differentiated Human BMSCs on Osteogenic and Adipogenic Differentiation Capacity of Naïve Human BMSCs.

Osteoporosis, or steroid-induced osteonecrosis of the hip, is accompanied by increased bone marrow adipogenesis. Such a disorder of adipogenic/osteogenic differentiation, affecting bone-marrow-derived mesenchymal stem cells (BMSCs), contributes to bone loss during aging. Here, we investigated the effects of extracellular vesicles (EVs) isolated from human (h)BMSCs during different stages of osteogenic differentiation on the osteogenic and adipogenic differentiation capacity of naïve (undifferentiated) hBMSCs. We observed that all EV groups increased viability and proliferation capacity and suppressed the apoptosis of naïve hBMSCs. In particular, EVs derived from hBMSCs at late-stage osteogenic differentiation promoted the osteogenic potential of naïve hBMSCs more effectively than EVs derived from naïve hBMSCs (naïve EVs), as indicated by the increased gene expression of COL1A1 and OPN. In contrast, the adipogenic differentiation capacity of naïve hBMSCs was inhibited by treatment with EVs from osteogenic differentiated hBMSCs. Proteomic analysis revealed that osteogenic EVs and naïve EVs contained distinct protein profiles, with pro-osteogenic and anti-adipogenic proteins encapsulated in osteogenic EVs. We speculate that osteogenic EVs could serve as an intercellular communication system between bone- and bone-marrow adipose tissue, for transporting osteogenic factors and thus favoring pro-osteogenic processes. Our data may support the theory of an endocrine circuit with the skeleton functioning as a ductless gland.

MicroRNA-148a-3p is a candidate mediator of increased bone marrow adiposity and bone loss following spinal cord injury.

Spinal cord injury is often followed by osteoporosis characterized by rapid and severe bone loss. This leads to an increased risk of osteoporotic fracture in people with spinal cord injury, resulting in increased healthcare costs, morbidity, and mortality. Though it is common, the mechanisms underlying this osteoporosis are not completely understood and treatment options are limited. No biomarkers have been identified for predicting fracture risk. In this study, we sought to investigate microRNA mediated mechanisms relating to osteoporosis following spinal cord injury. We studied subjects with acute SCI (n=12), chronic SCI (n=18), and controls with no SCI (n=23). Plasma samples from all subjects underwent transcriptomic analysis to quantify microRNA expression, after which miR-148a-3p was selected for further study. We performed CT scans of the knee on all subjects with SCI and analyzed these scans to quantify bone marrow adipose tissue volume. MiR-148a-3p was upregulated in subjects with acute SCI vs chronic SCI, as well as in acute SCI vs no SCI. Subjects with chronic SCI had greater levels of marrow adiposity in the distal femoral diaphysis compared to subjects with acute SCI. MiR-148a-3p levels were negatively associated with distal femoral diaphysis marrow adiposity. A multivariable model showed that miR-148a-3p and BMI explained 24% of variation in marrow adiposity. A literature search revealed that miR-148a-3p has multiple bone and fat metabolism related targets. Our findings suggest that miR-148a-3p is a mediator of osteoporosis following spinal cord injury and a potential future therapeutic target.

Adipocyte-Cancer Cell Interactions in the Bone Microenvironment.

When compared to adipocytes in other anatomical sites, the interaction of bone marrow resident adipocytes with the other cells in their microenvironment is less well understood. Bone marrow adipocytes originate from a resident, self-renewing population of multipotent bone marrow stromal cells which can also give rise to other lineages such as osteoblasts. The differentiation fate of these mesenchymal progenitors can be influenced to favour adipogenesis by several factors, including the administration of thiazolidinediones and increased age. Experimental data suggests that increases in bone marrow adipose tissue volume may make bone both more attractive to metastasis and conducive to cancer cell growth. Bone marrow adipocytes are known to secrete a variety of lipids, cytokines and bioactive signaling molecules known as adipokines, which have been implicated as mediators of the interaction between adipocytes and cancer cells. Recent studies have provided new insight into the impact of bone marrow adipose tissue volume expansion in regard to supporting and exacerbating the effects of bone metastasis from solid tumors, focusing on prostate, breast and lung cancer and blood cancers, focusing on multiple myeloma. In this mini-review, recent research developments pertaining to the role of factors which increase bone marrow adipose tissue volume, as well as the role of adipocyte secreted factors, in the progression of bone metastatic prostate and breast cancer are assessed. In particular, recent findings regarding the complex cross-talk between adipocytes and metastatic cells of both lung and prostate cancer are highlighted.

Zfp687 knock-in mouse model of Paget’s disease of bone exhibits increased bone marrow adiposity preceding bone remodelling alteration

Zfp687 knock-in mouse model of Paget’s disease of bone exhibits increased bone marrow adiposity preceding bone remodelling alteration

ApoA1 Deficiency Reshapes the Phenotypic and Molecular Characteristics of Bone Marrow Adipocytes in Mice.

In the present study, we studied the effect of apolipoprotein A-1 (APOA1) on the spatial and molecular characteristics of bone marrow adipocytes, using well-characterized ApoA1 knockout mice. APOA1 is a central regulator of high-density lipoprotein cholesterol (HDL-C) metabolism, and thus HDL; our recent work showed that deficiency of APOA1 increases bone marrow adiposity in mice. We found that ApoA1 deficient mice have greatly elevated adipocytes within their bone marrow compared to wild type counterparts. Morphologically, the increased adipocytes were similar to white adipocytes, and displayed proximal tibial-end localization. Marrow adipocytes from wild type mice were significantly fewer and did not display a bone-end distribution pattern. The mRNA levels of the brown/beige adipocyte-specific markers Ucp1, Dio2, Pat2, and Pgc1a; and the expression of leptin were greatly reduced in the ApoA1 knock-out in comparison to the wild-type mice. In the knock-out mice, adiponectin was remarkably elevated. In keeping with the close ties of hematopoietic stem cells and marrow adipocytes, using flow cytometry we found that the elevated adiposity in the ApoA1 knockout mice is associated with a significant reduction in the compartments of hematopoietic stem cells and common myeloid, but not of the common lymphoid, progenitors. Moreover, the ‘beiging’-related marker osteopontin and the angiogenic factor VEGF were also reduced in the ApoA1 knock-out mice, further supporting the notion that APOA1—and most probably HDL-C—regulate bone marrow microenvironment, favoring beige/brown adipocyte characteristics.