Young minds, deeper insights: a recap of the BMAS Summer School 2023, ranging from basic research to clinical implications of bone marrow adipose tissue

Bone marrow adiposity (BMA) is a rapidly growing yet very young research field that is receiving worldwide attention based on its intimate relationship with skeletal and metabolic diseases, as well as hematology and cancer. Moreover, increasing numbers of young scientists and students are currently and actively working on BMA within their research projects. These developments led to the foundation of the International Bone Marrow Adiposity Society (BMAS), with the goal to promote BMA knowledge worldwide, and to train new generations of researchers interested in studying this field. Among the many initiatives supported by BMAS, there is the BMAS Summer School, inaugurated in 2021 and now at its second edition. The aim of the BMAS Summer School 2023 was to educate and train students by disseminating the latest advancement on BMA. Moreover, Summer School 2023 provided suggestions on how to write grants, deal with negative results in science, and start a laboratory, along with illustrations of alternative paths to academia. The event was animated by constructive and interactive discussions between early-career researchers and more senior scientists. In this report, we highlight key moments and lessons learned from the event.

Omega-3 PUFAs prevent bone impairment and bone marrow adiposity in mouse model of obesity

Obesity adversely affects bone and fat metabolism in mice and humans. Omega-3 polyunsaturated fatty acids (omega-3 PUFAs) have been shown to improve glucose metabolism and bone homeostasis in obesity. However, the impact of omega-3 PUFAs on bone marrow adipose tissue (BMAT) and bone marrow stromal cell (BMSC) metabolism has not been intensively studied yet. In the present study we demonstrated that omega-3 PUFA supplementation in high fat diet (HFD + F) improved bone parameters, mechanical properties along with decreased BMAT in obese mice when compared to the HFD group. Primary BMSCs isolated from HFD + F mice showed decreased adipocyte and higher osteoblast differentiation with lower senescent phenotype along with decreased osteoclast formation suggesting improved bone marrow microenvironment promoting bone formation in mice. Thus, our study highlights the beneficial effects of omega-3 PUFA-enriched diet on bone and cellular metabolism and its potential use in the treatment of metabolic bone diseases.

Human bone marrow stromal cells: the impact of anticoagulants on stem cell properties

Background: Bone marrow stromal cells (BMSCs) are the source of multipotent stem cells, which are important for regenerative medicine and diagnostic purposes. The isolation of human BMSCs from the bone marrow (BM) cavity using BM aspiration applies the method with collection into tubes containing anticoagulants. Interactions with anticoagulants may affect the characteristics and composition of isolated BMSCs in the culture. Thus, we investigated how anticoagulants in isolation procedures and cultivation affect BMSC molecular characteristics. Methods: BM donors (age: 48-85 years) were recruited from the hematology clinic. BM aspirates were obtained from the iliac crest and divided into tubes coated with ethylenediaminetetraacetic acid (EDTA) or heparin anticoagulants. Isolated BMSCs were analyzed by flow cytometry and RNA-seq analysis. Further cellular and molecular characterizations of BMSCs including CFU, proliferation and differentiation assays, cytometry, bioenergetic assays, metabolomics, immunostaining, and RT-qPCR were performed. Results: The paired samples of isolated BMSCs obtained from the same patient showed increased cellular yield in heparin vs. EDTA samples, accompanied by the increased number of CFU colonies. However, no significant changes in molecular characteristics were found between heparin- and EDTA-isolated BMSCs. On the other hand, RNA-seq analysis revealed an increased expression of genes involved in nucleotide metabolism and cellular metabolism in cultivated vs. non-cultivated BMSCs regardless of the anticoagulant, while genes involved in inflammation and chromatin remodeling were decreased in cultivated vs. non-cultivated BMSCs. Conclusion: The type of anticoagulant in BMSC isolation did not have a significant impact on molecular characteristics and cellular composition, while in vitro cultivation caused the major change in the transcriptomics of BMSCs, which is important for future protocols using BMSCs in regenerative medicine and clinics.

Novel thiazolidinedione analog reduces a negative impact on bone and mesenchymal stem cell properties in obese mice compared to classical thiazolidinediones

Objective

The use of thiazolidinediones (TZDs) as insulin sensitizers has been shown to have side effects including increased accumulation of bone marrow adipocytes (BMAds) associated with a higher fracture risk and bone loss. A novel TZD analog MSDC-0602K with low affinity to PPARγ has been developed to reduce adverse effects of TZD therapy. However, the effect of MSDC-0602K on bone phenotype and bone marrow mesenchymal stem cells (BM-MSCs) in relation to obesity has not been intensively studied yet.

Methods

Here, we investigated whether 8-week treatment with MSDC-0602K has a less detrimental effect on bone loss and BM-MSC properties in obese mice in comparison to first generation of TZDs, pioglitazone. Bone parameters (bone microstructure, bone marrow adiposity, bone strength) were examined by μCT and 3-point bending test. Primary BM-MSCs were isolated and measured for osteoblast and adipocyte differentiation. Cellular senescence, bioenergetic profiling, nutrient consumption and insulin signaling were also determined.

Results

The findings demonstrate that MSDC-0602K improved bone parameters along with increased proportion of smaller BMAds in tibia of obese mice when compared to pioglitazone. Further, primary BM-MSCs isolated from treated mice and human BM-MSCs revealed decreased adipocyte and higher osteoblast differentiation accompanied with less inflammatory and senescent phenotype induced by MSDC-0602K vs. pioglitazone. These changes were further reflected by increased glycolytic activity differently affecting glutamine and glucose cellular metabolism in MSDC-0602K-treated cells compared to pioglitazone, associated with higher osteogenesis.

Conclusion

Our study provides novel insights into the action of MSDC-0602K in obese mice, characterized by the absence of detrimental effects on bone quality and BM-MSC metabolism when compared to classical TZDs and thus suggesting a potential therapeutical use of MSDC-0602K in both metabolic and bone diseases.

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MSDC-0602K improves bone quality and increases proportion of smaller BMAds in obese mice.

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MSDC-0602K-treated mice show lower adipogenic differentiation with less senescent phenotype in primary BM-MSCs.

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MSDC-0602K induces higher glycolytic activity in BM-MSCs compared to pioglitazone.

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MSDC-0602-treated BM-MSCs prefer glutamine over glucose uptake in comparison to AT-MSCs.

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Beneficial effect of MSDC-06002K in BM-MSCs manifests by absence of MPC inhibition.

Obesity-Induced Changes in Bone Marrow Homeostasis

Obesity is characterized by low-grade inflammation, which is accompanied by increased accumulation of immune cells in peripheral tissues including adipose tissue (AT), skeletal muscle, liver and pancreas, thereby impairing their primary metabolic functions in the regulation of glucose homeostasis. Obesity has also shown to have a detrimental effect on bone homeostasis by altering bone marrow and hematopoietic stem cell differentiation and thus impairing bone integrity and immune cell properties. The origin of immune cells arises in the bone marrow, which has been shown to be affected with the obesogenic condition via increased cellularity and shifting differentiation and function of hematopoietic and bone marrow mesenchymal stem cells in favor of myeloid progenitors and increased bone marrow adiposity. These obesity-induced changes in the bone marrow microenvironment lead to dramatic bone marrow remodeling and compromising immune cell functions, which in turn affect systemic inflammatory conditions and regulation of whole-body metabolism. However, there is limited information on the inflammatory secretory factors creating the bone marrow microenvironment and how these factors changed during metabolic complications. This review summarizes recent findings on inflammatory and cellular changes in the bone marrow in relation to obesity and further discuss whether dietary intervention or physical activity may have beneficial effects on the bone marrow microenvironment and whole-body metabolism.

[Effect of fiberoptic bronchoscopy (FOB) with bronchoalveolar lavage (BAL) on gas exgange in patients after cardiac surgery]

Fiberoptic bronchoscopy (FOB) has become a commonplace procedure in ICUs in patients after operation. We studied the outcomes of 35 FOBs performed in 26 patients (18 male and 8 female) during their stay in the ICU of "St. Ekaterina" University Hospital in Sofia after cardiac surgery with Cardiopulmonary Bypass. 33 (95%) of our patients were receiving mechanical ventilation at the time of the FOB. Bronchoalveolar lavage (BAL) was added to all procedures. 21 (60%) patients demonstrated an improvement after FOB. We defined improvement as either an increase of PaO2 with 10 or more mmHg in 6 hours after the procedure or better aeration on the follow-up chest radiograph (CXR). In 19 (54%) FOBs a great amount of secretions, plugging up bronchial lumens was seen. 14 (73%) of these patients were improved after the FOB. From the rest 16 patients, in whom such increased amount of secretions was not seen on FOB, only 7 (43%) demonstrated an improvement after the FOB. 16 procedures were performed on indications of atelectasis. 9 (56%) of them showed an improvement after the FOB. When atelectasis was not present on the CXR, an improvement was found in 12 (63%) cases.

CONCLUSIONS

1. FOB is most effective in removing retained secretions. 2. Although not so effective in resolving atelectasis that is not caused by central plugging, FOB should not be neglected because of the additional benefit of BAL for clearing more distal airways.

[Isotope nephrography in patients with obesity]

131I-hippuran nephrography conducted in 80 patients aged 26-53 with I and II degree obesity has revealed changes in the excretory phase (36.9 per cent of the patients with I degree obesity) and secretory and excretory and some vascular and metabolic abnormalities were registered in 79.4 per cent of those with II degree obesity. Weight gain had an adverse effect on the condition of such patients. Isotope nephrography enables one to study risk factors (arterial hypertension, atherosclerosis, diabetes mellitus).

[Complex radioisotope diagnosis of thyroid gland diseases in vivo and in vitro]

A variety of in vivo and in vitro methods: radioactive iodine accumulation, thyroid suppression and stimulation test, a scintigraphic study and a radioimmunoassay to determine triiodothyronine-binding capacity (free T3), thyroxine (T4) concentration and the effective thyroxine ratio (ETR), was used for diagnostic specification and accurate planning of therapy of patients with thyroid diseases. The suppression test combined with the results of the in vitro analysis (free T3, T4 and ETR) was decisive for establishing diagnosis.