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PUMA-induced apoptosis drives bone marrow failure and genomic instability in telomerase-deficient mice.

Bone marrow failure is a severe complication of human telomere biology disorders and predisposes individuals to secondary leukemia. A deeper understanding of this process could offer significant clinical benefits. Using a preclinical mouse model deficient in the RNA component of the telomerase (mTerc), we demonstrate that bone marrow failure results from excessive apoptosis, predominantly mediated by the pro-apoptotic p53 target PUMA. Genetic ablation of Puma alleviates hematological phenotypes and reduces the risk of lethal bone marrow failure while preserving genomic stability. Mechanistically, PUMA deficiency decreases the sensitivity of hematopoietic cells to lethal stressors, including critically short telomeres. As a consequence, reduced compensatory turnover of hematopoietic progenitors slows down telomere shortening at the population level, delays stem cell exhaustion, and diminishes the acquisition of somatic mutations - ultimately preventing neoplastic transformation. Elevated expression of both p53 and PUMA is also observed in the bone marrow from patients with telomere biology disorders. While apoptosis resistance is traditionally associated with malignant transformation, our findings provide evidence that selective inhibition of PUMA-mediated apoptosis may represent a viable therapeutic strategy to prevent or delay leukemic transformation in this patient population.

Animals

Clinical implications of bone marrow adiposity identified by phenome-wide association and Mendelian randomization in the UK Biobank.

Bone marrow adiposity changes in diverse diseases, but the full scope of these, and whether they are directly influenced by marrow adiposity, remains unknown. To address this, we previously measured the bone marrow fat fraction of the femoral head, total hip, femoral diaphysis, and spine of over 48,000 UK Biobank participants. Here, we first use these data for PheWAS to identify diseases associated with marrow adiposity at each site. This reveals associations with 47 incident diseases across 12 disease categories, including osteoporosis, fracture, type 2 diabetes, cardiovascular diseases, cancers, and other conditions that burden public health worldwide. Intriguingly, type 2 diabetes associates positively with spine bone marrow adiposity but negatively with marrow adiposity at femoral sites. We then establish PRSs based on bone-marrow-fat-fraction-associated SNPs and use PRS-PheWAS and Mendelian randomization to explore causal associations between marrow adiposity and disease. PRS-PheWAS reveals that genetic predisposition to increased marrow adiposity is positively associated with osteoporosis and fractures. Mendelian randomization further suggests that increased marrow adiposity at the diaphysis and total hip is causally associated with osteoporosis. Our findings substantially advance understanding of how marrow adiposity impacts human health and highlight its potential as a biomarker and/or therapeutic target for diverse human diseases.

Humans

Bone-marrow-homing lipid nanoparticles for genome editing in diseased and malignant haematopoietic stem cells.

Therapeutic genome editing of haematopoietic stem cells (HSCs) would provide long-lasting treatments for multiple diseases. However, the in vivo delivery of genetic medicines to HSCs remains challenging, especially in diseased and malignant settings. Here we report on a series of bone-marrow-homing lipid nanoparticles that deliver mRNA to a broad group of at least 14 unique cell types in the bone marrow, including healthy and diseased HSCs, leukaemic stem cells, B cells, T cells, macrophages and leukaemia cells. CRISPR/Cas and base editing is achieved in a mouse model expressing human sickle cell disease phenotypes for potential foetal haemoglobin reactivation and conversion from sickle to non-sickle alleles. Bone-marrow-homing lipid nanoparticles were also able to achieve Cre-recombinase-mediated genetic deletion in bone-marrow-engrafted leukaemic stem cells and leukaemia cells. We show evidence that diverse cell types in the bone marrow niche can be edited using bone-marrow-homing lipid nanoparticles.

Animals

Spatially Distinct Bone Marrow Sites Are Asymmetrically Impacted by Inflammatory Cardiovascular Disease.

Cardiovascular disease, a leading cause of mortality globally, is increasingly recognized to involve complex bone marrow-driven inflammatory mechanisms, yet the impact on spatially distinct bone marrow sites and comorbidities remains poorly understood. To address this, we developed MarrowMet, a methodology for whole-body, site-specific quantification of bone marrow activity. The approach involves intravenously injecting the metabolic tracer 18F-fluorodeoxyglucose (18F-FDG) in mice, followed by bone excision to quantify site-specific bone marrow activity, with values then superimposed on a whole-body mouse atlas. After establishing that 18F-FDG bone marrow uptake strongly correlated with inflammatory activity, we applied MarrowMet to map site-specific activation patterns across diverse cardiovascular pathologies, including mouse models of inflammatory atherosclerosis, acute ischemic events, acute respiratory distress syndrome, metabolic syndrome, and aging. MarrowMet guided the selection of bone marrow regions of interest for in-depth mass cytometric analyses, with the skull and sternum emerging as critical sites exhibiting distinct immune and metabolic profiles in cardiovascular disease. These results challenge the prevailing view that femoral marrow represents systemic activity. Together, this work lays a foundation for whole-body exploration of bone marrow heterogeneity, yielding critical insights into cardiovascular disease and associated inflammatory responses, and MarrowMet can be readily adopted to profile other immune mechanisms in a variety of pathologies, including cancer and autoimmune diseases.

(18)F-FDG

Volumetric bone marrow cellularity (VBMC) assessment from routinely processed trephines using three-dimensional x-ray histology and gaussian peak modelling.

Objective.Bone marrow cellularity is routinely estimated from a small number of two-dimensional histology sections, making assessment sensitive to section representativeness, processing artefacts and observer interpretation. Three-dimensional (3D) x-ray histology (XRH), using x-ray computed microtomography (µCT), enables non-destructive whole-block imaging of trephine biopsies. This study evaluated whether XRH combined with Gaussian peak modelling could provide a pragmatic whole-block volumetric bone marrow cellularity (VBMC) estimate from formalin-fixed paraffin-embedded (FFPE) trephine biopsy blocks.Approach.Six routinely processed FFPE bone marrow trephine blocks were imaged using µCT-based XRH at ∼15 µm spatial resolution. VBMC was defined as the red-marrow (RM) fraction of the marrow soft-tissue compartment, RM/(RM + intra-biopsy wax), with wax serving as the volumetric proxy for adipocyte/yellow marrow space. Whole-volume greyscale histograms were modelled using a three-peak Gaussian approach representing intra-biopsy wax, RM and demineralised trabecular matrix. Peak-height and area-under-the-curve metrics were compared with whole-volume 3D segmentation and clinical two-dimensional (2D) cellularity estimates.Main Results.Gaussian peak modelling successfully approximated the segmented tissue-phase distributions. The peak-height-derived VBMC metric showed the closest agreement with whole-volume 3D segmentation, with an average absolute percentage difference of 9.3%, compared with 18.6% for clinical expert 2D cellularity estimates. The area-under-the-curve metric followed similar trends but consistently overestimated VBMC. Clinical 2D cellularity broadly followed whole-biopsy trends but showed one discordant case not explained by slice-position sampling alone. XRH also enabled unrestricted virtual reslicing and visualisation of sectioning-associated artefacts prior to further microtomy.Significance.Pre-sectioning XRH combined with Gaussian peak modelling provides a rapid, segmentation-free route to volumetric cellularity estimation from intact clinical FFPE trephine blocks. The approach supports objective whole-biopsy assessment while remaining compatible with routine histopathology workflows, reflecting the expected limitations of section-based visual estimation despite its role as the current clinical standard. In the near term, it could provide a non-disruptive adjunct to conventional 2D cellularity reporting, pending larger validation studies.

Imaging, Three-Dimensional

Analysis of HLA Allelic and Haplotypic Frequencies in a Cohort of Bone Marrow Donors in Catalonia: Impact of Next-Generation Sequencing on Donor Registry Quality.

In haematopoietic stem cell transplantation (HSCT), the volunteer unrelated donor (VUD) has become the most common strategy in Europe, as improved outcomes are achieved through HLA compatibility at allelic-level resolution. In this context, the implementation of next-generation sequencing (NGS) in histocompatibility typing laboratories has significantly enhanced the quality of bone marrow registries, enabling a high level of resolution at a lower cost and improved performance. In this study, we analyse a large cohort of 21,787 bone marrow donors in Catalonia and present the observed HLA allelic and haplotypic frequencies, along with their linkage disequilibria. HLA-A, -B, -C, -E and -G were genotyped at full resolution, while -DRB1, -DQB1, -DQA1, -DPA1 and -DPB1 were genotyped at high resolution. We identified 236 new officially named HLA alleles, both coding and non-coding regions. This study highlights that the implementation of high-throughput HLA typing has led to an increase in the number of registered donors and an improvement in quality, which has been reflected in a rise in the number of effective donors.

Humans

Single cell mutational analysis of PIK3CA in circulating tumor cells and metastases in breast cancer reveals heterogeneity, discordance, and mutation persistence in cultured disseminated tumor cells from bone marrow.

BACKGROUND: Therapeutic decisions in cancer are generally guided by molecular biomarkers or, for some newer therapeutics, primary tumor genotype. However, because biomarkers or genotypes may change as new metastases emerge, circulating tumor cells (CTCs) from blood are being investigated for a role in guiding real-time drug selection during disease progression, expecting that CTCs will comprehensively represent the full spectrum of genomic changes in metastases. However, information is limited regarding mutational heterogeneity among CTCs and metastases in breast cancer as discerned by single cell analysis. The presence of disseminated tumor cells (DTCs) in bone marrow also carry prognostic significance in breast cancer, but with variability between CTC and DTC detection. Here we analyze a series of single tumor cells, CTCs, and DTCs for PIK3CA mutations and report CTC and corresponding metastatic genotypes. METHODS: We used the MagSweeper, an immunomagnetic separation device, to capture live single tumor cells from breast cancer patients' primary and metastatic tissues, blood, and bone marrow. Single cells were screened for mutations in exons 9 and 20 of the PIK3CA gene. Captured DTCs grown in cell culture were also sequenced for PIK3CA mutations. RESULTS: Among 242 individual tumor cells isolated from 17 patients and tested for mutations, 48 mutated tumor cells were identified in three patients. Single cell analyses revealed mutational heterogeneity among CTCs and tumor cells in tissues. In a patient followed serially, there was mutational discordance between CTCs, DTCs, and metastases, and among CTCs isolated at different time points. DTCs from this patient propagated in vitro contained a PIK3CA mutation, which was maintained despite morphological changes during 21 days of cell culture. CONCLUSIONS: Single cell analysis of CTCs can demonstrate genotypic heterogeneity, changes over time, and discordance from DTCs and distant metastases. We present a cautionary case showing that CTCs from any single blood draw do not always reflect metastatic genotype, and that CTC and DTC analyses may provide independent clinical information. Isolated DTCs remain viable and can be propagated in culture while maintaining their original mutational status, potentially serving as a future resource for investigating new drug therapies.

Bone Marrow

A Novel Long Noncoding RNA-LNC000133 Associated With Steroid-Induced Osteonecrosis of the Femoral Head Promotes Osteoblast Differentiation Through Bone Marrow Mesenchymal Stem Cells-Derived Exosomes Pathway: A Bioinformatics Validation and Detailed Mechanistic Study.

Steroid-induced osteonecrosis of the femoral head (SONFH) is a debilitating disease caused by glucocorticoid abuse, characterized by complex pathogenesis and unclear molecular mechanisms. Dysfunction of bone marrow mesenchymal stem cells (BMSCs) and their exosome-mediated signalling is a key contributor to SONFH, although the precise mechanisms remain to be elucidated. In this study, the differential expression profiles of long noncoding RNAs (lncRNAs), microRNAs (miRNAs) and messenger RNAs (mRNAs) in exosomes derived from human BMSCs (hBMSCs) obtained from patients with SONFH compared to controls with femoral neck fractures were identified. Through next-generation sequencing, a novel lncRNA, LNC000133, associated with SONFH was discovered. Using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and competing endogenous RNA (ceRNA) network construction, the LNC000133/miR-362-5p/TGF-β3/SMAD3/BMP2 signalling axis was established. The definitive expression, localization and full-length sequence of LNC000133 in BMSCs were subsequently validated by Northern blot, quantitative real-time polymerase chain reaction (qRT-PCR), fluorescence in situ hybridization (FISH) and rapid amplification of cDNA ends (RACE). Most notably, mechanistic studies demonstrated that LNC000133-modified BMSCs-derived exosomes were efficiently taken up by osteoblasts, which promoted proliferation and osteogenic differentiation by targeting the miR-362-5p/TGF-β3/SMAD3/BMP2 signalling pathway.

Humans

Generation of TWO iPSC lines (CRICKi025-A and CRICKi026-A) from healthy donor bone marrow mesenchymal stromal cells.

Mesenchymal stromal cells (MSCs) are key components of the bone marrow (BM), providing structural support and paracrine signals that regulate haematopoietic stem cell maintenance, self-renewal and differentiation. However, primary BM MSCs are rare, heterogeneous, and subject to donor variability and have limited ex-vivo expansion capacity, restricting their utility. Here, we describe two human induced pluripotent stem cells lines, CRICKi0025-A and CRICKi0026-A, reprogrammed from adult BM-derived MSCs using non-integrating Sendai virus vectors. Both lines showcase grade-A morphology, are genomically stable, upregulate essential pluripotent markers and can differentiate into the three germ layers. These lines are a well-characterised resource for generating MSCs.

Journal Article

Genomic and computational analysis of variants in telomere regulatory genes in subjects with bone marrow failure.

Telomere Biology Disorders (TBDs) are a genetically heterogeneous and often under-recognized cause of Bone Marrow Failure Syndromes (BMFS), driven by defective telomere maintenance and progressive telomere attrition. We performed an integrated genomic, telomeric and computational analysis in 118 subjects presenting clinical features of BMFS to delineate the contribution of Telomere Regulatory Genes (TRGs) variants to disease pathogenesis. Whole exome sequencing (WES) identified pathogenic (18.18%), likely pathogenic (27.27%) and rare variants of uncertain significance (54.54%) in 27 subjects (22.9%) across five TRGs: RTEL1, TERT, TINF2, NOP10, and WRAP53. Telomere Length (TL) assessment revealed significant telomere shortening in TRG variant-positive subjects compared with age-matched controls, with the most profound attrition observed in individuals harboring de novo TINF2 gene variants. RTEL1 emerged as the most frequently affected gene, with recurrent clustering of variants within its C-terminal regulatory region. A familial NOP10 variant, Asp12His, segregated with cutaneous pigmentation and hematological abnormalities consistent with the established role of NOP10 in dyskeratosis congenita, further broadening the known mutational spectrum of the gene. Structure-guided in-silico analyses predicted that both novel and recurrent variants disrupt protein stability, telomerase assembly or trafficking and shelterin complex integrity. Reduced TERT expression and a significant inverse correlation between telomere length and clinical severity further underscored the functional impact of TRG defects. Collectively, this study provides the first comprehensive characterization of TRG variants in the Indian BMFS cohort and highlights the utility of integrating genomic sequencing, telomere length measurement and computational modeling to improve diagnostic precision, variant interpretation and clinical stratification in TBDs.

Journal Article

Clinical characteristic of isolated thrombocytopenia in patients with bone marrow failure-related germline variants: a retrospective study from a single centre.

BACKGROUND: Immune thrombocytopenia (ITP) comprises the majority of thrombocytopenia. Some patients respond poorly to first-line ITP therapy or develop pancytopenia years later. Recent studies link heterozygous germline variants in acquired aplastic anemia (AA), yet their role in isolated thrombocytopenia carrying bone marrow failure-related germline variants (ITGV-BMFs) remains unclear. While whole-exome sequencing (WES) detects these variants, its cost limits routine use. This study compares prognosis and clinical features of isolated thrombocytopenia in patients with ITGV-BMFsand those with classic ITP. METHODS: The clinical data of patients diagnosed with ITGV-BMFs were retrospectively analyzed and compared with those of patients with classic ITP from August 2018 to February 2024. The baseline characteristics, genomic systematically background, previous treatment response as well as their follow-up outcomes were compared. RESULTS: Patients with ITGV-BMFs demonstrated earlier onset age (p&#x2009;<&#x2009;0.001), lower bleeding scores and CD34%, along with elevated mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and reticulocyte (RET) counts (p&#x2009;<&#x2009;0.001). Multivariate logistic regression analysis showed that the patients with ITGV-BMFs may possess distinct characteristics, including an earlier age at onset (p&#x2009;=&#x2009;0.014) and lower bleeding score (p&#x2009;=&#x2009;0.048). Notably, MCV and RET showed promising performance in receiver operating characteristic (ROC) curve analysis. During the follow-up period, 57.69% (15/26) ITGV-BMFs patients were further confirmed as aplastic anemia (AA, n&#x2009;=&#x2009;13) or myelodysplastic syndrome (MDS, n&#x2009;=&#x2009;2), with a median progression-free survival (PFS) of 7.25&#x2009;years (p&#x2009;<&#x2009;0.0001). CONCLUSION: ITGV-BMFs may be diagnosed early using elevated MCV and reticulocyte counts, a diagnostic approach that may lead to earlier intervention and improved prognosis.

Humans