Navigating the bone marrow niche: translational insights and cancer-driven dysfunction

ECM-mimicking hydrogel models of human adipose tissue identify deregulated lipid metabolism in the prostate cancer-adipocyte crosstalk under antiandrogen therapy

Antiandrogen therapies are effectively used to treat advanced prostate cancer, but eventually cancer adaptation drives unresolved metastatic castration-resistant prostate cancer (mCRPC). Adipose tissue influences metabolic reprogramming in cancer and was proposed as a contributor to therapy resistance. Using extracellular matrix (ECM)-mimicking hydrogel coculture models of human adipocytes and prostate cancer cells, we show that adipocytes from subcutaneous or bone marrow fat have dissimilar responses under the antiandrogen Enzalutamide. We demonstrate that androgen receptor (AR)-dependent cancer cells (LNCaP) are more influenced by human adipocytes than AR-independent cells (C4-2B), with altered lipid metabolism and adipokine secretion. This response changes under Enzalutamide, with increased AR expression and adipogenic and lipogenic genes in cancer cells and decreased lipid content and gene dysregulation associated with insulin resistance in adipocytes. This is in line with the metabolic syndrome that men with mCRPC under Enzalutamide experience. The all-human, all-3D, models presented here provide a significant advance to dissect the role of fat in therapy response for mCRPC.

Co-delivery of protopanaxatriol/icariin into niche cells restores bone marrow niches to rejuvenate HSCs for chemotherapy-induced myelosuppression

BACKGROUND

Up to 80 % of chemotherapeutic drugs induce myelosuppression in patients. Chemotherapy not only impairs of hematopoietic stem cells (HSCs) but also damages bone marrow niches (vascular and endosteal). Current treatments for myelosuppression overlook these chemotherapy-induced damages to bone marrow niches and the critical role of niche restoration on hematopoietic regeneration. Ginsenoside protopanaxatriol (PPT) protects vascular endothelium from injury, while icariin (ICA) promotes osteogenic differentiation. The combination of PPT and ICA aims to restore damaged vascular and endosteal niches, thus rejuvenating HSCs for treating myelosuppression.

PURPOSE

This study aims to develop effective, bone marrow niche-directed PPT/ICA therapies for treating chemotherapy-induced myelosuppression.

METHODS

3D cell spheroids were used to investigate the effects of PPT/ICA on cell-cell interactions in vascular niches, osteogenesis, and extracellular matrix (ECM) secretion in endosteal niches. In vitro mimic niche models were designed to access the drug combination's efficacy in rejuvenating and mobilizing in HSCs within bone marrow niches. The delivery capability of PPT/ICA to key niche cell types (mesenchymal stromal cells (MSCs), endothelial cells (ECs), and osteoblasts (OBs)) via nanocarriers has been determined. DSS6 peptide-modified nanoparticles (DSS6-NPs) were prepared for specific co-delivery of PPT/ICA into key niche cell populations in vivo.

RESULTS

PPT can prevent vascular niche injury by restoring vascular EC cell-cell adhesion and the intercellular interactions between ECs and MSCs in 5-fluorouracil (5-FU)-damaged cell spheroids. ICA repaired 5-FU-damaged endosteal niches by promoting osteogenesis and ECM secretion. The combination of PPT and ICA restores key HSC niche factor gene expressions, normalizing HSC differentiation and mobilization. The in vitro cellular uptake efficiency of nanocarriers in a mimic niche is positively correlated with their in vivo delivery into bone marrow niche cells. DSS6-NPs greatly enhance the delivery of PPT/ICA into MSCs and OBs within bone marrow niches. Co-loading of PPT/ICA into DSS6-NPs effectively repairs damaged bone marrow niches and promotes HSC rejuvenation in vivo.

CONCLUSION

The combination of PPT and ICA effectively prevents injury to the vascular and endosteal niches, thereby promoting hematopoietic regeneration in the bone marrow. This study provides novel niche-directed PPT/ICA therapies for managing chemotherapy-induced myelosuppression.

Cells and signals of the leukemic microenvironment that support progression of T-cell acute lymphoblastic leukemia (T-ALL)

Current intensified chemotherapy regimens have significantly increased survival rates for pediatric patients with T-cell acute lymphoblastic leukemia (T-ALL), but these treatments can result in serious adverse effects; furthermore, patients who are resistant to chemotherapy or who relapse have inferior outcomes, together highlighting the need for improved therapeutic strategies. Despite recent advances in stratifying T-ALL into molecular subtypes with distinct driver mutations, efforts to target the tumor-intrinsic genomic alterations critical for T-ALL progression have yet to translate into more effective and less toxic therapies. Ample evidence now indicates that extrinsic factors in the leukemic microenvironment are critical for T-ALL growth, infiltration, and therapeutic resistance. Considering the diversity of organs infiltrated by T-ALL cells and the unique cellular components of the microenvironment encountered at each site, it is likely that there are both shared features of tumor-supportive niches across multiple organs and site-specific features that are key to leukemia cell survival. Therefore, elucidating the distinct microenvironmental cues supporting T-ALL in different anatomic locations could reveal novel therapeutic targets to improve therapies. This review summarizes the current understanding of the intricate interplay between leukemia cells and the diverse cells they encounter within their tumor microenvironments (TMEs), as well as opportunities to therapeutically target the leukemic microenvironment.

RNA-loaded nanoparticles for the treatment of hematological cancers

Hematological cancers encompass a diverse group of malignancies affecting the blood, bone marrow, lymph nodes, and spleen. These disorders present unique challenges due to their complex etiology and varied clinical manifestations. Despite significant advancements in understanding and treating hematological malignancies, innovative therapeutic approaches are continually sought to enhance patient outcomes. This review highlights the application of RNA nanoparticles (RNA-NPs) in the treatment of hematological cancers. We delve into detailed discussions on in vitro and preclinical studies involving RNA-NPs for adult patients, as well as the application of RNA-NPs in pediatric hematological cancer. The review also addresses ongoing clinical trials involving RNA-NPs and explores the emerging field of CAR-T therapy engineered by RNA-NPs. Finally, we discuss the challenges still faced in translating RNA-NP research to clinics.

Myeloid-derived suppressor cells: Implication in myeloid malignancies and immunotherapy

Myeloid malignancies stem from a modified hematopoietic stem cell and predominantly include acute myeloid leukemia, myelodysplastic neoplasms, myeloproliferative malignancies, and chronic myelomonocytic leukemia. Myeloid-derived suppressor cells (MDSCs) exhibit immunoregulatory properties by governing the innate and adaptive immune systems, creating a permissive and supportive environment for neoplasm growth. This review examines the key characteristics of MDSCs in myeloid malignancies, highlighting that an increased MDSC count corresponds to heightened immunosuppressive capabilities, fostering an immune-tolerant neoplasm microenvironment. Also, this review analyzes and describes the potential of combined cancer therapies, focusing on targeting MDSC generation, expansion, and their inherent immunosuppressive activities to enhance the efficacy of current cancer immunotherapies. A comprehensive understanding of the implications of myeloid malignancies may enhance the exploration of immunotherapeutic strategies for their potential application.

Running on empty: Exploring stem cell exhaustion in geriatric musculoskeletal disease

Ageing populations globally are associated with increased musculoskeletal disease, including osteoporosis and sarcopenia. These conditions place a significant burden of disease on the individual, society and the economy. To address this, we need to understand the underpinning biological changes, including stem cell exhaustion, which plays a key role in the ageing of the musculoskeletal system. This review of the recent evidence provides an overview of the associated biological processes. The review utilised the PubMed/Medline, Science Direct, and Google Scholar databases. Mechanisms of ageing identified involve a reaction to the chronic inflammation and oxidative stress associated with ageing, resulting in progenitor cell senescence and adipogenic differentiation, leading to decreased mass and quality of both bone and muscle tissue. Although the mechanisms underpinning stem cell exhaustion are unclear, it remains a promising avenue through which to identify new strategies for prevention, detection and management.

Advances in Drug Delivery Systems for the Treatment of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a common and catastrophic hematological neoplasm with high mortality rates. Conventional therapies, including chemotherapy, hematopoietic stem cell transplantation (HSCT), immune therapy, and targeted agents, have unsatisfactory outcomes for AML patients due to drug toxicity, off-target effects, drug resistance, drug side effects, and AML relapse and refractoriness. These intrinsic limitations of current treatments have promoted the development and application of nanomedicine for more effective and safer leukemia therapy. In this review, the classification of nanoparticles applied in AML therapy, including liposomes, polymersomes, micelles, dendrimers, and inorganic nanoparticles, is reviewed. In addition, various strategies for enhancing therapeutic targetability in nanomedicine, including the use of conjugating ligands, biomimetic-nanotechnology, and bone marrow targeting, which indicates the potential to reverse drug resistance, are discussed. The application of nanomedicine for assisting immunotherapy is also involved. Finally, the advantages and possible challenges of nanomedicine for the transition from the preclinical phase to the clinical phase are discussed.

Hematopoietic stem and progenitor cell membrane-coated vesicles for bone marrow-targeted leukaemia drug delivery

Leukemia is a kind of hematological malignancy originating from bone marrow, which provides essential signals for initiation, progression, and recurrence of leukemia. However, how to specifically deliver drugs to the bone marrow remains elusive. Here, we develop biomimetic vesicles by infusing hematopoietic stem and progenitor cell (HSPC) membrane with liposomes (HSPC liposomes), which migrate to the bone marrow of leukemic mice via hyaluronic acid-CD44 axis. Moreover, the biomimetic vesicles exhibit superior binding affinity to leukemia cells through intercellular cell adhesion molecule-1 (ICAM-1)/integrin β2 (ITGB2) interaction. Further experiments validate that the vesicles carrying chemotherapy drug cytarabine (Ara-C@HSPC-Lipo) markedly inhibit proliferation, induce apoptosis and differentiation of leukemia cells, and decrease number of leukemia stem cells. Mechanically, RNA-seq reveals that Ara-C@HSPC-Lipo treatment induces apoptosis and differentiation and inhibits the oncogenic pathways. Finally, we verify that HSPC liposomes are safe in mice. This study provides a method for targeting bone marrow and treating leukemia.

Mesenchymal stromal cells in myeloid malignancies: Immunotherapeutic opportunities

Myeloid malignancies are clonal disorders of the progenitor cells or hematopoietic stem cells, including acute myeloid leukemia, myelodysplastic syndromes, myeloproliferative malignancies, and chronic myelomonocytic leukemia. Myeloid neoplastic cells affect the proliferation and differentiation of other hematopoietic lineages in the bone marrow and peripheral blood, leading to severe and life-threatening complications. Mesenchymal stromal cells (MSCs) residing in the bone marrow exert immunosuppressive functions by suppressing innate and adaptive immune systems, thus creating a supportive and tolerant microenvironment for myeloid malignancy progression. This review summarizes the significant features of MSCs in myeloid malignancies, including their role in regulating cell growth, cell death, and antineoplastic resistance, in addition to their immunosuppressive contributions. Understanding the implications of MSCs in myeloid malignancies could pave the path for potential use in immunotherapy.

An overview of multiple myeloma: A monoclonal plasma cell malignancy's diagnosis, management, and treatment modalities

Multiple Myeloma (MM) is a plasma cell cancer with high mortality and morbidity rates. Its incidence rate has increased by 143% since 1975. Adipokines, cytokines, chemokines, and genetic variations influence the development and progression of MM. Chromosomal translocations cause mutations associated with MM. The pathogenesis of MM is complicated by novel issues like miRNAs, RANKL, Wnt/DKK1, Wnt, and OPG. Conventional diagnosis methods include bone marrow biopsy, sPEP or uPEP, sIFE and uIFE, and sFLC assay, along with advanced techniques such as FISH, SNPA, and gene expression technologies. A novel therapeutic strategy has been developed recently. Chemotherapy, hematopoietic stem cell transplantation, and a variety of drug classes in combination are used to treat patients with high-risk diseases. Alkylating agents, PIs, and IMiDs have all been developed as effective treatment options for MM in recent years. This review overviews the current recommendations for managing MGUS, SMM, MM, SP and NSMM and discusses practices in diagnosing and treating MM.

Contribution of the TIME in BCP-ALL: the basis for novel approaches therapeutics

The bone marrow (BM) niche is a microenvironment where both immune and non-immune cells functionally interact with hematopoietic stem cells (HSC) and more differentiated progenitors, contributing to the regulation of hematopoiesis. It is regulated by various signaling molecules such as cytokines, chemokines, and adhesion molecules in its microenvironment. However, despite the strict regulation of BM signals to maintain their steady state, accumulating evidence in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) indicates that leukemic cells can disrupt the physiological hematopoietic niche in the BM, creating a new leukemia-supportive microenvironment. This environment favors immunological evasion mechanisms and the interaction of these cells with the development and progression of BCP-ALL. With a growing understanding of the tumor immune microenvironment (TIME) in the development and progression of BCP-ALL, current strategies focused on "re-editing" TIME to promote antitumor immunity have been developed. In this review, we summarize how TIME cells are disrupted by the presence of leukemic cells, evading immunosurveillance mechanisms in the BCP-ALL model. We also explore the crosstalk between TIME and leukemic cells that leads to treatment resistance, along with the most promising immuno-therapy strategies. Understanding and further research into the role of the BM microenvironment in leukemia progression and relapse are crucial for developing more effective treatments and reducing patient mortality.

Consequences of Aging on Bone

With the aging of the global population, the incidence of musculoskeletal diseases has been increasing, seriously affecting people's health. As people age, the microenvironment within skeleton favors bone resorption and inhibits bone formation, accompanied by bone marrow fat accumulation and multiple cellular senescence. Specifically, skeletal stem/stromal cells (SSCs) during aging tend to undergo adipogenesis rather than osteogenesis. Meanwhile, osteoblasts, as well as osteocytes, showed increased apoptosis, decreased quantity, and multiple functional limitations including impaired mechanical sensing, intercellular modulation, and exosome secretion. Also, the bone resorption function of macrophage-lineage cells (including osteoclasts and preosteoclasts) was significantly enhanced, as well as impaired vascularization and innervation. In this study, we systematically reviewed the effect of aging on bone and the within microenvironment (including skeletal cells as well as their intracellular structure variations, vascular structures, innervation, marrow fat distribution, and lymphatic system) caused by aging, and mechanisms of osteoimmune regulation of the bone environment in the aging state, and the causal relationship with multiple musculoskeletal diseases in addition with their potential therapeutic strategy.

Immunomodulatory properties of CD38 antibodies and their effect on anticancer efficacy in multiple myeloma

BACKGROUND

CD38 has been established as an important therapeutic target for multiple myeloma (MM), for which two CD38 antibodies are currently approved-daratumumab and isatuximab. CD38 is an ectoenzyme that degrades NAD and its precursors and is involved in the production of adenosine and other metabolites.

AIM

Among the various mechanisms by which CD38 antibodies can induce MM cell death is immunomodulation, including multiple pathways for CD38-mediated T-cell activation. Patients who respond to anti-CD38 targeting treatment experience more marked changes in T-cell expansion, activity, and clonality than nonresponders.

IMPLICATIONS

Resistance mechanisms that undermine the immunomodulatory effects of CD38-targeting therapies can be tumor intrinsic, such as the downregulation of CD38 surface expression and expression of complement inhibitor proteins, and immune microenvironment-related, such as changes to the natural killer (NK) cell numbers and function in the bone marrow niche. There are numerous strategies to overcome this resistance, which include identifying and targeting other therapeutic targets involved in, for example, adenosine production, the activation of NK cells or monocytes through immunomodulatory drugs and their combination with elotuzumab, or with bispecific T-cell engagers.

Stromal-induced epithelial-mesenchymal transition induces targetable drug resistance in acute lymphoblastic leukemia

The bone marrow microenvironment (BME) drives drug resistance in acute lymphoblastic leukemia (ALL) through leukemic cell interactions with bone marrow (BM) niches, but the underlying mechanisms remain unclear. Here, we show that the interaction between ALL and mesenchymal stem cells (MSCs) through integrin β1 induces an epithelial-mesenchymal transition (EMT)-like program in MSC-adherent ALL cells, resulting in drug resistance and enhanced survival. Moreover, single-cell RNA sequencing analysis of ALL-MSC co-culture identifies a hybrid cluster of MSC-adherent ALL cells expressing both B-ALL and MSC signature genes, orchestrated by a WNT/β-catenin-mediated EMT-like program. Blockade of interaction between β-catenin and CREB binding protein impairs the survival and drug resistance of MSC-adherent ALL cells in vitro and results in a reduction in leukemic burden in vivo. Targeting of this WNT/β-catenin-mediated EMT-like program is a potential therapeutic approach to overcome cell extrinsically acquired drug resistance in ALL.

Development and application of nanomaterials, nanotechnology and nanomedicine for treating hematological malignancies

Hematologic malignancies (HMs) pose a serious threat to patients' health and life, and the five-year overall survival of HMs remains low. The lack of understanding of the pathogenesis and the complex clinical symptoms brings immense challenges to the diagnosis and treatment of HMs. Traditional therapeutic strategies for HMs include radiotherapy, chemotherapy, targeted therapy and hematopoietic stem cell transplantation. Although immunotherapy and cell therapy have made considerable progress in the last decade, nearly half of patients still relapse or suffer from drug resistance. Recently, studies have emerged that nanomaterials, nanotechnology and nanomedicine show great promise in cancer therapy by enhancing drug targeting, reducing toxicity and side effects and boosting the immune response to promote durable immunological memory. In this review, we summarized the strategies of recently developed nanomaterials, nanotechnology and nanomedicines against HMs and then proposed emerging strategies for the future designment of nanomedicines to treat HMs based on urgent clinical needs and technological progress.

Targeting the stem cell niche micro-environment as therapeutic strategies in aging

Adult stem cells (ASCs) reside throughout the body and support various tissue. Owing to their self-renewal capacity and differentiation potential, ASCs have the potential to be used in regenerative medicine. Their survival, quiescence, and activation are influenced by specific signals within their microenvironment or niche. In better words, the stem cell function is significantly influenced by various extrinsic signals derived from the niche. The stem cell niche is a complex and dynamic network surrounding stem cells that plays a crucial role in maintaining stemness. Studies on stem cell niche have suggested that aged niche contributes to the decline in stem cell function. Notably, functional loss of stem cells is highly associated with aging and age-related disorders. The stem cell niche is comprised of complex interactions between multiple cell types. Over the years, essential aspects of the stem cell niche have been revealed, including cell-cell contact, extracellular matrix interaction, soluble signaling factors, and biochemical and biophysical signals. Any alteration in the stem cell niche causes cell damage and affects the regenerative properties of the stem cells. A pristine stem cell niche might be essential for the proper functioning of stem cells and the maintenance of tissue homeostasis. In this regard, niche-targeted interventions may alleviate problems associated with aging in stem cell behavior. The purpose of this perspective is to discuss recent findings in the field of stem cell aging, heterogeneity of stem cell niches, and impact of age-related changes on stem cell behavior. We further focused on how the niche affects stem cells in homeostasis, aging, and the progression of malignant diseases. Finally, we detail the therapeutic strategies for tissue repair, with a particular emphasis on aging.

Construction of Bone Hypoxic Microenvironment Based on Bone-on-a-Chip Platforms

The normal physiological activities and functions of bone cells cannot be separated from the balance of the oxygenation level, and the physiological activities of bone cells are different under different oxygenation levels. At present, in vitro cell cultures are generally performed in a normoxic environment, and the partial pressure of oxygen of a conventional incubator is generally set at 141 mmHg (18.6%, close to the 20.1% oxygen in ambient air). This value is higher than the mean value of the oxygen partial pressure in human bone tissue. Additionally, the further away from the endosteal sinusoids, the lower the oxygen content. It follows that the construction of a hypoxic microenvironment is the key point of in vitro experimental investigation. However, current methods of cellular research cannot realize precise control of oxygenation levels at the microscale, and the development of microfluidic platforms can overcome the inherent limitations of these methods. In addition to discussing the characteristics of the hypoxic microenvironment in bone tissue, this review will discuss various methods of constructing oxygen gradients in vitro and measuring oxygen tension from the microscale based on microfluidic technology. This integration of advantages and disadvantages to perfect the experimental study will help us to study the physiological responses of cells under more physiological-relevant conditions and provide a new strategy for future research on various in vitro cell biomedicines.

Bone Marrow Adipose Tissue: Regulation of Osteoblastic Niche, Hematopoiesis and Hematological Malignancies

Bone marrow adipose tissue (BMAT) creates a specific microniche within multifunctional bone marrow (BM) ecosystem which imposes changes in surrounding cells and at systemic level. Moreover, BMAT contributes to spatial and temporal separation and metabolic compartmentalization of BM, thus regulating BM homeostasis and diseases. Recent findings have identified novel progenitor subsets of bone marrow adipocytes (BMAd)s recruited during the BM adipogenesis within different skeletal and hematopoietic stem cell niches. Potential of certain mesenchymal BM cells to differentiate into both osteogenic and adipogenic lineages, contributes to the complex interplay of BMAT with endosteal (osteoblastic) niche compartments as an important cellular player in bone tissue homeostasis. Targeting and ablation of BMAT cells at certain states might be an optional and promising strategy for improvement of bone health. Additionally, recent findings demonstrated spatial distribution of BMAds related to hematopoietic cells and pointed out important functional roles in the vital processes such as long-term hematopoiesis. BM adipogenesis appears to be an emergency phenomenon that follows the production of hematopoietic stem and progenitor cell niche factors, thus regulating physiological, stressed, and malignant hematopoiesis. Lipolytic and secretory activity of BMAds can influence survival and proliferation of hematopoietic cells at different maturation stages. Due to their different lipid status, constitutive and regulated BMAds are important determinants of normal and malignant hematopoietic cells. Further elucidation of cellular and molecular players involved in BMAT expansion and crosstalk with malignant cells is of paramount importance for conceiving the new therapies for improvement of BM health.

Current progress of mesenchymal stem cell membrane-camouflaged nanoparticles for targeted therapy

Nanodrug delivery systems have been widely used in disease treatment. However, weak drug targeting, easy to be cleared by the immune system, and low biocompatibility are great obstacles for drug delivery. As an important part of cell information transmission and behavior regulation, cell membrane can be used as drug coating material which represents a promising strategy and can overcome these limitations. Mesenchymal stem cell (MSC) membrane, as a new carrier, has the characteristics of active targeting and immune escape of MSC, and has broad application potential in tumor treatment, inflammatory disease, tissue regeneration and other fields. Here, we review recent progress on the use of MSC membrane-coated nanoparticles for therapy and drug delivery, aiming to provide guidance for the design and clinical application of membrane carrier in the future.

Continuous Indexing of Fibrosis (CIF): improving the assessment and classification of MPN patients

The grading of fibrosis in myeloproliferative neoplasms (MPN) is an important component of disease classification, prognostication and monitoring. However, current fibrosis grading systems are only semi-quantitative and fail to fully capture sample heterogeneity. To improve the quantitation of reticulin fibrosis, we developed a machine learning approach using bone marrow trephine (BMT) samples (n = 107) from patients diagnosed with MPN or a reactive marrow. The resulting Continuous Indexing of Fibrosis (CIF) enhances the detection and monitoring of fibrosis within BMTs, and aids MPN subtyping. When combined with megakaryocyte feature analysis, CIF discriminates between the frequently challenging differential diagnosis of essential thrombocythemia (ET) and pre-fibrotic myelofibrosis with high predictive accuracy [area under the curve = 0.94]. CIF also shows promise in the identification of MPN patients at risk of disease progression; analysis of samples from 35 patients diagnosed with ET and enrolled in the Primary Thrombocythemia-1 trial identified features predictive of post-ET myelofibrosis (area under the curve = 0.77). In addition to these clinical applications, automated analysis of fibrosis has clear potential to further refine disease classification boundaries and inform future studies of the micro-environmental factors driving disease initiation and progression in MPN and other stem cell disorders.

A potential area of use for immune checkpoint inhibitors: Targeting bone marrow microenvironment in acute myeloid leukemia

Acute myeloid leukemia (AML) arises from the cells of myeloid lineage and is the most frequent leukemia type in adulthood accounting for about 80% of all cases. The most common treatment strategy for the treatment of AML includes chemotherapy, in rare cases radiotherapy and stem cell and bone marrow transplantation are considered. Immune checkpoint proteins involve in the negative regulation of immune cells, leading to an escape from immune surveillance, in turn, causing failure of tumor cell elimination. Immune checkpoint inhibitors (ICIs) target the negative regulation of the immune cells and support the immune system in terms of anti-tumor immunity. Bone marrow microenvironment (BMM) bears various blood cell lineages and the interactions between these lineages and the noncellular components of BMM are considered important for AML development and progression. Administration of ICIs for the AML treatment may be a promising option by regulating BMM. In this review, we summarize the current treatment options in AML treatment and discuss the possible application of ICIs in AML treatment from the perspective of the regulation of BMM.

Serum sclerostin and sympathetic skin response: relationship with myeloma bone disease

Background

Myeloma bone disease (MBD) is a common complication that significantly contributes to morbidity and mortality in multiple myeloma (MM). Serum sclerostin level and sympathetic activity can affect MBD. The purpose of this study is evaluation of serum sclerostin level and sympathetic activity (using sympathetic skin response “SSR”) in MM patients, and studying the relationship between both of them as well as their relationship with MBD. 35 smoldering myeloma patients (group I) and 35 newly diagnosed MM (group II) and 35 controls (group III) were included in the study. All the participants were subjected to complete history taking, and clinical examination. Assessment of serum sclerostin level, SSR, MM stages [by the international staging system (ISS)], MBD grading (according to the Durie–Salmon staging system) were done for all patients within 7 days from the diagnosis.

Results

Undetectable and decreased SSR amplitude are significantly more detected in group I and II (compared with group III). Autonomic manifestations, and loss of SSR is significantly more detected in group II than group I. Autonomic manifestations were absent in group III. SSR amplitude of median and tibial nerves is significantly decreased in group II than group I and III. MBD was detected in all patients of group II. Serum sclerostin and LDH were significantly increased in group II than group I. Group I and II had significantly higher levels of sclerostin when compared with group III. Group II had significantly higher levels of sclerostin and lower levels of ALP in comparison with group I. Serum sclerostin level was correlated positively with LDH and negatively with ALP and SSR amplitude. MBD was significantly affected by ISS stage III, LDH level, SSR affection and serum sclerostin level ≥ 0.40 ng/ml. SSR response affection was the most significant risk factor for advanced MBD followed by increased sclerostin level.

Conclusions

Serum sclerostin level was significantly increased and sympathetic activity was significantly decreased in MBD. Loss of the SSR response was the most significant risk factor for advanced MBD followed by increased sclerostin level.

Recommendations

Potentially validating the use of bone-turnover markers in larger studies, in addition to electrophysiological examination of SSR to stratify patients who are at high-risk for progressive MBD, as the use of newer agents with anabolic effects such as anti-sclerostin antibodies have shown potential in repair of MBD. These newer agents could potentially change the treatment landscape in patients with MBD.

The role of the bone microenvironment in regulating myeloma residual disease and treatment

Multiple myeloma is an incurable haematological cancer. The increase in targeted therapies has improved the number of myeloma patients achieving a complete response and improved progression-free survival following therapy. However, a low level of disease or minimal residual disease (MRD) still persists which contributes to the inevitable relapse in myeloma patients. MRD has been attributed to the presence of dormant myeloma cells and their subsequent reactivation, which is controlled by the microenvironment and specialised niches within the bone marrow. This contributes to the evasion of the immune system and chemotherapy, eventually leading to relapse. The growth of myeloma tumours are heavily dependent on environmental stimuli from the bone marrow microenvironment, and this plays a key role in myeloma progression. The bone microenvironment also plays a critical role in myeloma bone disease and the development of skeletal-related events. This review focuses on the bone marrow microenvironment in relation to myeloma pathogenesis and cancer dormancy. Moreover, it reviews the current therapies targeting the bone microenvironment to treat myeloma and myeloma bone disease. Lastly, it identifies novel therapeutic targets for myeloma treatment and the associated bone disease.

Associations Between Vertebral Marrow Proton Density Fat Fraction and Risk of Prostate Cancer

Bone marrow adipocytes may be responsible for cancer progression. Although marrow adipogenesis is suspected to be involved in prostate carcinogenesis, an association between marrow adiposity and prostate cancer risk has not been clearly established in vivo. This work included 115 newly diagnosed cases of histologically confirmed prostate cancer (range, 48-79 years) and 87 age-matched healthy controls. Marrow proton density fat fraction (PDFF) was measured by 3.0-T MR spectroscopy at the spine lumbar. Associations between marrow PDFF and risk of prostate cancer by stage of disease and grade sub-types were performed using multivariable polytomous logistic regression. There were no significant group differences in the vertebral marrow PDFF, despite prostate cancer patients having 6.6% higher marrow PDFF compared to the healthy controls (61.7 ± 9.8% vs. 57.9 ± 6.5%; t = 1.429, p = 0.161). After adjusting for various clinical and demographic characteristics, we found that elevated marrow PDFF was related to an increased risk of high-grade prostate cancer [odds ratios (OR) = 1.31; 95% confidence interval (CI), 1.08-1.57; p = 0.003]. Likewise, increased marrow PDFF had a significantly positive correlation with aggressive prostate cancer risk (OR = 1.54; 95% CI, 1.13-1.92; p <0.001). There were no associations between marrow PDFF and low-grade (p = 0.314) or non-aggressive (p = 0.435) prostate cancer risk. The data support the hypothesis that marrow adiposity was correlated with increased risk of aggressive prostate cancer, supporting a link between adipogenesis and prostate cancer risk.

Immunometabolism modulation, a new trick of edible and medicinal plants in cancer treatment

The edible and medicinal plants (EMPs) are becoming an abundant source for cancer prevention and treatment since the natural and healthy trend for modern human beings. Currently, there are more than one hundred species of EMPs widely used and listed by the national health commission of China, and most of them indicate immune or metabolic regulation potential in cancer treatment with numerous studies over the past two decades. In the present review, we focused on the metabolic influence in immunocytes and tumor microenvironment, including immune response, immunosuppressive factors and cancer cells, discussing the immunometabolic potential of EMPs in cancer treatment. There are more than five hundred references collected and analyzed through retrieving pharmacological studies deposited in PubMed by medical subject headings and the corresponding names derived from pharmacopoeia of China as a sole criterion. Finally, the immunometabolism modulation of EMPs was sketch out implying an immunometabolic control in cancer treatment.

The Bone Marrow Microenvironment Mechanisms in Acute Myeloid Leukemia

Bone marrow (BM) is a highly complex tissue that provides important regulatory signals to orchestrate hematopoiesis. Resident and transient cells occupy and interact with some well characterized niches to produce molecular and cellular mechanisms that interfere with differentiation, migration, survival, and proliferation in this microenvironment. The acute myeloid leukemia (AML), the most common and severe hematological neoplasm in adults, arises and develop in the BM. The osteoblastic, vascular, and reticular niches provide surface co-receptors, soluble factors, cytokines, and chemokines that mediate important functions on hematopoietic cells and leukemic blasts. There are some evidences of how AML modify the architecture and function of these three BM niches, but it has been still unclear how essential those modifications are to maintain AML development. Basic studies and clinical trials have been suggesting that disturbing specific cells and molecules into the BM niches might be able to impair leukemia competencies. Either through niche-specific molecule inhibition alone or in combination with more traditional drugs, the bone marrow microenvironment is currently considered the potential target for new strategies to treat AML patients. This review describes the cellular and molecular constitution of the BM niches under healthy and AML conditions, presenting this anatomical compartment by a new perspective: as a prospective target for current and next generation therapies.

Aging, Bone Marrow and Next-Generation Sequencing (NGS): Recent Advances and Future Perspectives

The aging of bone marrow (BM) remains a very imperative and alluring subject, with an ever-increasing interest among fellow scientists. A considerable amount of progress has been made in this field with the established ‘hallmarks of aging’ and continued efforts to investigate the age-related changes observed within the BM. Inflammaging is considered as a low-grade state of inflammation associated with aging, and whilst the possible mechanisms by which aging occurs are now largely understood, the processes leading to the underlying changes within aged BM remain elusive. The ability to identify these changes and detect such alterations at the genetic level are key to broadening the knowledgebase of aging BM. Next-generation sequencing (NGS) is an important molecular-level application presenting the ability to not only determine genomic base changes but provide transcriptional profiling (RNA-seq), as well as a high-throughput analysis of DNA–protein interactions (ChIP-seq). Utilising NGS to explore the genetic alterations occurring over the aging process within alterative cell types facilitates the comprehension of the molecular and cellular changes influencing the dynamics of aging BM. Thus, this review prospects the current landscape of BM aging and explores how NGS technology is currently being applied within this ever-expanding field of research.

The Relationship Between Mesenchymal Stem Cells and Tumor Dormancy

Tumor dormancy, a state of tumor, is clinically undetectable and the outgrowth of dormant tumor cells into overt metastases is responsible for cancer-associated deaths. However, the dormancy-related molecular mechanism has not been clearly described. Some researchers have proposed that cancer stem cells (CSCs) and disseminated tumor cells (DTCs) can be seen as progenitor cells of tumor dormancy, both of which can remain dormant in a non-permissive soil/niche. Nowadays, research interest in the cancer biology field is skyrocketing as mesenchymal stem cells (MSCs) are capable of regulating tumor dormancy, which will provide a unique therapeutic window to cure cancer. Although the influence of MSCs on tumor dormancy has been investigated in previous studies, there is no thorough review on the relationship between MSCs and tumor dormancy. In this paper, the root of tumor dormancy is analyzed and dormancy-related molecular mechanisms are summarized. With an emphasis on the role of the MSCs during tumor dormancy, new therapeutic strategies to prevent metastatic disease are proposed, whose clinical application potentials are discussed, and some challenges and prospects of the studies of tumor dormancy are also described.

Bone marrow MSC from pediatric patients with B-ALL highly immunosuppress T-cell responses but do not compromise CD19-CAR T-cell activity

Background

Although adoptive transfer of CD19-directed chimeric antigen receptor (CAR) T-cells (CD19-CAR T-cells) achieves high rates of complete response in patients with B-cell acute lymphoblastic leukemia (B-ALL), relapse is common. Bone marrow (BM) mesenchymal stem/stromal cells (BM-MSC) are key components of the hematopoietic niche and are implicated in B-ALL pathogenesis and therapy resistance. MSC exert an immunosuppressive effect on T-cells; however, their impact on CD19-CAR T-cell activity is understudied.

Methods

We performed a detailed characterization of BM-MSC from pediatric patients with B-ALL (B-ALL BM-MSC), evaluated their immunomodulatory properties and their impact on CD19-CAR T-cell activity in vitro using microscopy, qRT-PCR, ELISA, flow cytometry analysis and in vivo using a preclinical model of severe colitis and a B-ALL xenograft model.

Results

While B-ALL BM-MSC were less proliferative than those from age-matched healthy donors (HD), the morphology, immunophenotype, differentiation potential and chemoprotection was very similar. Likewise, both BM-MSC populations were equally immunosuppressive in vitro and anti-inflammatory in an in vivo model of severe colitis. Interestingly, BM-MSC failed to impair CD19-CAR T-cell cytotoxicity or cytokine production in vitro using B-ALL cell lines and primary B-ALL cells. Finally, the growth of NALM6 cells was controlled in vivo by CD19-CAR T-cells irrespective of the absence/presence of BM-MSC.

Conclusions

Collectively, our data demonstrate that pediatric B-ALL and HD BM-MSC equally immunosuppress T-cell responses but do not compromise CD19-CAR T-cell activity.

Primary Cilia Enhance Osteogenic Response of Jaw Mesenchymal Stem Cells to Hypoxia and Bisphosphonate

PURPOSE

Primary cilia play a significant role in mesenchymal stem cell (MSC) lineage commitment, skeletal development, and bone homeostasis. MSC responsiveness to metabolic stress is associated with radiation and drug-induced jaw osteonecrosis. Therefore, we hypothesize that orofacial MSCs (OFMSCs) osteogenic commitment in response to cellular stressors hypoxia and bisphosphonates is a survival response coupled to primary cilia biogenesis.

MATERIALS AND METHODS

Human OFMSCs were subjected to cellular stress using severe hypoxia, nitrogen-containing bisphosphonate (pamidronate) and low serum starvation. OFMSC primary cilia formation, as well as cell survival and proliferation, were detected using immunofluorescence, CellTitre-Glo, and WST-1 assays respectively. OFMSC differentiation was tested using Alizarin Red S staining. OFMSCs survival and osteogenic markers were assessed by western blotting relative to primary cilia number and associated acetylated tubulin levels.

RESULTS

Baseline OFMSC proliferation was stable under short-term severe hypoxia and pamidronate treatments whether combined with or without serum starvation. Hypoxia and pamidronate decreased the number of OFMSCs positive for primary cilia that was consistent with increased HIF-1α and caspase 3 but decreased cyclin D1. Combined effects of hypoxia and pamidronate on OFMSCs significantly reduced ciliation but did not completely abrogate it. Combination of serum deprivation, hypoxia, and pamidronate promoted OFMSCs osteogenic differentiation that was consistent with upregulated HIF-1α levels.

CONCLUSIONS

Partial rather than complete loss of OFMSC ciliation and enhanced osteogenic commitment represent adaptive survival response of OFMSCs to severe hypoxia and pamidronate-induced metabolic stress. Hypoxia and drug-induced OFMSC stress may be significant events governing the pathogenesis and clinical outcomes of jaw osteonecrosis.

Tumor-on-chip modeling of organ-specific cancer and metastasis

Every year, cancer claims millions of lives around the globe. Unfortunately, model systems that accurately mimic human oncology - a requirement for the development of more effective therapies for these patients - remain elusive. Tumor development is an organ-specific process that involves modification of existing tissue features, recruitment of other cell types, and eventual metastasis to distant organs. Recently, tissue engineered microfluidic devices have emerged as a powerful in vitro tool to model human physiology and pathology with organ-specificity. These organ-on-chip platforms consist of cells cultured in 3D hydrogels and offer precise control over geometry, biological components, and physiochemical properties. Here, we review progress towards organ-specific microfluidic models of the primary and metastatic tumor microenvironments. Despite the field's infancy, these tumor-on-chip models have enabled discoveries about cancer immunobiology and response to therapy. Future work should focus on the development of autologous or multi-organ systems and inclusion of the immune system.

Myeloid-Derived Suppressor Cells and Mesenchymal Stem/Stromal Cells in Myeloid Malignancies

Myeloid malignancies arise from an altered hematopoietic stem cell and mainly comprise acute myeloid leukemia, myelodysplastic syndromes, myeloproliferative malignancies, and chronic myelomonocytic leukemia. Myeloid neoplastic leukemic cells may influence the growth and differentiation of other hematopoietic cell lineages in peripheral blood and bone marrow. Myeloid-derived suppressor cells (MDSCs) and mesenchymal stromal cells (MSCs) display immunoregulatory properties by controlling the innate and adaptive immune systems that may induce a tolerant and supportive microenvironment for neoplasm development. This review analyzes the main features of MDSCs and MSCs in myeloid malignancies. The number of MDSCs is elevated in myeloid malignancies exhibiting high immunosuppressive capacities, whereas MSCs, in addition to their immunosuppression contribution, regulate myeloid leukemia cell proliferation, apoptosis, and chemotherapy resistance. Moreover, MSCs may promote MDSC expansion, which may mutually contribute to the creation of an immuno-tolerant neoplasm microenvironment. Understanding the implication of MDSCs and MSCs in myeloid malignancies may favor their potential use in immunotherapeutic strategies.

Myeloid-Derived Suppressor Cells and Mesenchymal Stem/Stromal Cells in Myeloid Malignancies

Myeloid malignancies arise from an altered hematopoietic stem cell and mainly comprise acute myeloid leukemia, myelodysplastic syndromes, myeloproliferative malignancies, and chronic myelomonocytic leukemia. Myeloid neoplastic leukemic cells may influence the growth and differentiation of other hematopoietic cell lineages in peripheral blood and bone marrow. Myeloid-derived suppressor cells (MDSCs) and mesenchymal stromal cells (MSCs) display immunoregulatory properties by controlling the innate and adaptive immune systems that may induce a tolerant and supportive microenvironment for neoplasm development. This review analyzes the main features of MDSCs and MSCs in myeloid malignancies. The number of MDSCs is elevated in myeloid malignancies exhibiting high immunosuppressive capacities, whereas MSCs, in addition to their immunosuppression contribution, regulate myeloid leukemia cell proliferation, apoptosis, and chemotherapy resistance. Moreover, MSCs may promote MDSC expansion, which may mutually contribute to the creation of an immuno-tolerant neoplasm microenvironment. Understanding the implication of MDSCs and MSCs in myeloid malignancies may favor their potential use in immunotherapeutic strategies.

Importance of the origin of mesenchymal (stem) stromal cells in cancer biology: "alliance" or "war" in intercellular signals

Mesenchymal stem cells (MSCs) play a central role in the intercellular signaling within the tumor microenvironment (TME), exchanging signals with cancer cells and tumor stromal cells, such as cancer-associated fibroblasts and inflammatory mononuclear cells. Research attributes both pro-tumor and anti-tumor actions to MSCs; however, evidence indicates that MSCs specific effect on the tumor depends on the source of the MSCs and the type of tumor. There are consistent data proving that MSCs from reproductive tissues, such as the uterus, umbilical cord or placenta, have potent anti-tumor effects and tropism towards tumor tissues. More interestingly, products derived from MSCs, such as secretome or extracellular vesicles, seem to reproduce the effects of their parental cells, showing a potential advantage for clinical treatments by avoiding the drawbacks associated with cell therapy. Given these perspectives, it appears necessary new research to optimize the production, safety and antitumor potency of the products derived from the MSCs suitable for oncological therapies.

METTL3 mediates bone marrow mesenchymal stem cell adipogenesis to promote chemoresistance in acute myeloid leukaemia

Adipogenesis of bone marrow mesenchymal stem cells (MSCs) promotes chemoresistance of acute myeloid leukaemia (AML) cells. MSCs from AML patients (AML‐MSCs) display enhanced adipogenesis compared with bone marrow MSCs from healthy donors. However, the precise molecular mechanism by which adipogenesis of MSCs from AML marrow differs from normal counterparts remains obscure. We found that METTL3 significantly inhibits MSC adipogenesis. Here, we aimed to identify the molecular mechanism linking METTL3 and MSC adipogenesis. Analysis of m⁶A epigenetic changes in MSCs determined via RIP‐qPCR and MeRIP‐qPCR indicated that METTL3 affects AKT protein expression in MSCs by mediating m⁶A modification of AKT1‐mRNA. Downregulated METTL3 expression in AML‐MSCs induced an increase in AKT protein, resulting in enhanced MSC adipogenesis, thereby contributing to chemoresistance in AML cells. Therefore, targeting AKT regulation by mRNA modification in MSC adipogenesis might provide a novel therapeutic strategy to overcome AML chemoresistance.

The Role of Marrow Microenvironment in the Growth and Development of Malignant Plasma Cells in Multiple Myeloma

The development and effectiveness of novel therapies in multiple myeloma have been established in large clinical trials. However, multiple myeloma remains an incurable malignancy despite significant therapeutic advances. Accumulating data have elucidated our understanding of the genetic background of the malignant plasma cells along with the role of the bone marrow microenvironment. Currently, the interaction among myeloma cells and the components of the microenvironment are considered crucial in multiple myeloma pathogenesis. Adhesion molecules, cytokines and the extracellular matrix play a critical role in the interplay among genetically transformed clonal plasma cells and stromal cells, leading to the proliferation, progression and survival of myeloma cells. In this review, we provide an overview of the multifaceted role of the bone marrow microenvironment in the growth and development of malignant plasma cells in multiple myeloma.

Therapeutic Potential of Niche-Specific Mesenchymal Stromal Cells for Spinal Cord Injury Repair

The use of mesenchymal stem/stromal cells (MSCs) for transplant-mediated repair represents an important and promising therapeutic strategy after spinal cord injury (SCI). The appeal of MSCs has been fuelled by their ease of isolation, immunosuppressive properties, and low immunogenicity, alongside the large variety of available tissue sources. However, despite reported similarities in vitro, MSCs sourced from distinct tissues may not have comparable biological properties in vivo. There is accumulating evidence that stemness, plasticity, immunogenicity, and adaptability of stem cells is largely controlled by tissue niche. The extrinsic impact of cellular niche for MSC repair potential is therefore important, not least because of its impact on ex vivo expansion for therapeutic purposes. It is likely certain niche-targeted MSCs are more suited for SCI transplant-mediated repair due to their intrinsic capabilities, such as inherent neurogenic properties. In addition, the various MSC anatomical locations means that differences in harvest and culture procedures can make cross-comparison of pre-clinical data difficult. Since a clinical grade MSC product is inextricably linked with its manufacture, it is imperative that cells can be made relatively easily using appropriate materials. We discuss these issues and highlight the importance of identifying the appropriate niche-specific MSC type for SCI repair.

Liver X receptors and skeleton: Current state-of-knowledge

The liver X receptors (LXR) is a nuclear receptor that acts as a prominent regulator of lipid homeostasis and inflammatory response. Its therapeutic effectiveness against various diseases like Alzheimer's disease and atherosclerosis has been investigated in detail. Emerging pieces of evidence now reveal that LXR is also a crucial modulator of bone remodeling. However, the molecular mechanisms underlying the pharmacological actions of LXR on the skeleton and its role in osteoporosis are poorly understood. Therefore, in the current review, we highlight LXR and its actions through different molecular pathways modulating skeletal homeostasis. The studies described in this review propound that LXR in association with estrogen, PTH, PPARγ, RXR hedgehog, and canonical Wnt signaling regulates osteoclastogenesis and bone resorption. It regulates RANKL-induced expression of c-Fos, NFATc1, and NF-κB involved in osteoclast differentiation. Additionally, several studies suggest suppression of RANKL-induced osteoclast differentiation by synthetic LXR ligands. Given the significance of modulation of LXR in various physiological and pathological settings, our findings indicate that therapeutic targeting of LXR might potentially prevent or treat osteoporosis and improve bone quality.

The Potential of Mesenchymal Stromal Cells in Neuroblastoma Therapy for Delivery of Anti-Cancer Agents and Hematopoietic Recovery

Neuroblastoma is one of the most common pediatric cancers and a major cause of cancer-related death in infancy. Conventional therapies including high-dose chemotherapy, stem cell transplantation, and immunotherapy approach a limit in the treatment of high-risk neuroblastoma and prevention of relapse. In the last two decades, research unraveled a potential use of mesenchymal stromal cells in tumor therapy, as tumor-selective delivery vehicles for therapeutic compounds and oncolytic viruses and by means of supporting hematopoietic stem cell transplantation. Based on pre-clinical and clinical advances in neuroblastoma and other malignancies, we assess both the strong potential and the associated risks of using mesenchymal stromal cells in the therapy for neuroblastoma. Furthermore, we examine feasibility and safety aspects and discuss future directions for harnessing the advantageous properties of mesenchymal stromal cells for the advancement of therapy success.

Remodeling of Bone Marrow Niches and Roles of Exosomes in Leukemia

Leukemia is a hematological malignancy that originates from hematopoietic stem cells in the bone marrow. Significant progress has made in understanding its pathogensis and in establishing chemotherapy and hematopoietic stem cell transplantation therapy (HSCT). However, while the successive development of new therapies, such as molecular-targeted therapy and immunotherapy, have resulted in remarkable advances, the fact remains that some patients still cannot be saved, and resistance to treatment and relapse are still problems that need to be solved in leukemia patients. The bone marrow (BM) niche is a microenvironment that includes hematopoietic stem cells and their supporting cells. Leukemia cells interact with bone marrow niches and modulate them, not only inducing molecular and functional changes but also switching to niches favored by leukemia cells. The latter are closely associated with leukemia progression, suppression of normal hematopoiesis, and chemotherapy resistance, which is precisely the area of ongoing study. Exosomes play an important role in cell-to-cell communication, not only with cells in close proximity but also with those more distant due to the nature of exosomal circulation via body fluids. In leukemia, exosomes play important roles in leukemogenesis, disease progression, and organ invasion, and their usefulness in the diagnosis and treatment of leukemia has recently been reported. The interaction between leukemia cell-derived exosomes and the BM microenvironment has received particular attention. Their interaction is believed to play a very important role; in addition to their diagnostic value, exosomes could serve as a marker for monitoring treatment efficacy and as an aid in overcoming drug resistance, among the many problems in leukemia patients that have yet to be overcome. In this paper, we will review bone marrow niches in leukemia, findings on leukemia-derived exosomes, and exosome-induced changes in bone marrow niches.

Mesenchymal stem cells as a double-edged sword in tumor growth: focusing on MSC-derived cytokines

Mesenchymal stem cells (MSCs) show homing capacity towards tumor sites. Numerous reports indicate that they are involved in multiple tumor-promoting processes through several mechanisms, including immunosuppression; stimulation of angiogenesis; transition to cancer-associated fibroblasts; inhibition of cancer cell apoptosis; induction of epithelial-mesenchymal transition (EMT); and increase metastasis and chemoresistance. However, other studies have shown that MSCs suppress tumor growth by suppressing angiogenesis, incrementing inflammatory infiltration, apoptosis and cell cycle arrest, and inhibiting the AKT and Wnt signaling pathways. In this review, we discuss the supportive and suppressive impacts of MSCs on tumor progression and metastasis. We also discuss MSC-based therapeutic strategies for cancer based on their potential for homing to tumor sites.

Transcriptome analysis identifies the differentially expressed genes related to the stemness of limbal stem cells in mice

Limbal stem cells (LSCs) reside in the basal layer of limbal epithelial cells (LECs). They are crucial for maintenance of corneal epithelium homeostasis and corneal wound healing. Their stemness is determined by their gene expression pattern. Despite of several positive identifiers have been reported, the unique biomarker for LSCs still remain elusive. Differentially expressed genes (DEGs) between stem cells and differentiated cells affect the fate of stem cells via specific signaling pathway. In order to understand the DEGs in the LSCs, RNA-seq was firstly conducted using a mouse model. A total of 1907 up-regulated DEGs and 395 down-regulated DEGs were identified in the limbus (L) compared to central cornea (CC) and conjunctiva (Cj). Reliability of the expression of genes from RNA-seq analysis was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and immunofluorescence staining. The expression pattern of putative biomarkers was considered to be age-related. In up-regulated DEGs GO analysis, 570 gene ontology (GO) terms were significantly enriched. Five groups of genes related with biological processes from these significantly enriched GO terms comprised ionic transport, regulation of tissue development, muscle contraction, visual perception, and cell adhesion, which were clustered as a weighted similar network. Whereas, in down-regulated DEGs GO analysis, 61 GO terms were significantly enriched and only one group of ATP biosynthesis and metabolic process were clustered. Furthermore, we identified 55 signaling pathways by the Kyoto Encyclopedia of Genes and Genomes (KEGG) database based on up-regulated genes and 14 KEGG pathways based on down-regulated genes. In this study, we provide a landscape of the expression of putative LSCs biomarkers and stemness-related signaling pathways in a mouse model. Our findings could aid in the identification of LSC niche factors that may be related to the stemness of the LSCs.

Association of Bone Mineral Density to Cerebral Small Vessel Disease Burden

OBJECTIVE

To test the hypothesis that bone mineral loss is mechanistically related to cerebral small vessel disease (SVD), we investigated the relationship between bone mineral density and the prevalence and intensity of SVD among patients with stroke.

METHODS

We analyzed data of 1,190 consecutive patients with stroke who were >50 years of age and underwent both brain MRI and dual-energy x-ray absorptiometry from the stroke registry of Chung-Ang University Hospital in Seoul, Korea. The patients were categorized into 3 groups according to their bone mineral density (normal, osteopenia, and osteoporosis). White matter hyperintensities, silent lacunes, cerebral microbleeds, and extensive perivascular space were assessed from brain MRI. Multinomial logistic regression model was used to examine the association between osteoporosis and total SVD score. We also recruited 70 patients with stroke to study serum bone turnover markers and microRNAs related to both cerebral atherosclerosis and bone metabolism to understand bone and brain interaction.

RESULTS

Osteoporosis was determined among 284 patients (23.9%), and 450 patients (37.8%) had osteopenia. As bone mineral density decreased, total SVD score and the incidence of every SVD phenotype increased except strictly lobar cerebral microbleeds. Multinomial logistic regression analysis showed that osteoporosis was independently associated with severe SVD burden. The levels of microRNA-378f were significantly increased among the patients with osteoporosis and maximal total SVD score and positively correlated with parathyroid hormone and osteocalcin.

CONCLUSIONS

These findings suggest a pathophysiologic link between bone mineral loss and hypertensive cerebral arteriolar degeneration, possibly mediated by circulating microRNA.

Sclerostin-Neutralizing Antibody Treatment Rescues Negative Effects of Rosiglitazone on Mouse Bone Parameters

Obesity, a growing pandemic, is a risk factor for many cancers and causes increased bone marrow adipose tissue (BMAT). in vitro studies and obese animal models suggest that BMAT contributes to cancer progression, but there is a lack of preclinical models to directly test BMAT's role in cancer. Overactivation of peroxisome-proliferator-activated receptor-γ (PPARγ) can skew bone formation and resorption rates, resulting in increased BMAT and trabecular bone loss. Thiazolidinediones (eg, rosiglitazone) are anti-diabetic therapies that promote adipogenesis through PPARγ activation. We investigated if rosiglitazone increases BMAT in an immunocompromised model, commonly used in cancer research, and if these effects could be reversed by co-administering a bone anabolic agent (sclerostin-neutralizing antibody [Scl-Ab]), which has been shown to inhibit adipogenesis, using DXA, μCT, OsO4 μCT, and dynamic histomorphometry. Four weeks of rosiglitazone in female SCID Beige mice (cohort 1) significantly decreased trabecular bone volume (BV/TV) by about one-half, through increased osteoclast and suppressed osteoblast activity, and significantly increased BMAT. In cohort 2, mice were administered rosiglitazone ± Scl-Ab for 4 weeks, and then rosiglitazone was discontinued and Scl-Ab or vehicle were continued for 6 weeks. Scl-Ab significantly increased bone parameters (eg, BV/TV, N.Ob/B.Pm, and MS/BS) in both groups. Scl-Ab also overcame many negative effects of rosiglitazone (eg, effects on trabecular bone parameters, increased mineralization lag time [MLT], and decreased bone formation rate [BFR]). Interestingly, Scl-Ab significantly decreased rosiglitazone-induced BMAT in the femur, mostly due to a reduction in adipocyte size, but had a much weaker effect on tibial BMAT. These data suggest targeting sclerostin can prevent rosiglitazone-induced bone loss and reduce BM adiposity, in some, but not all BMAT locations. Collectively, our data demonstrate that rosiglitazone increases BMAT in SCID Beige mice, but concomitant changes in bone may confound its use to specifically determine BMAT's role in tumor models. © 2020 American Society for Bone and Mineral Research (ASBMR).

Bone metastasis: mechanisms, therapies, and biomarkers

Skeletal metastases are frequent complications of many cancers, causing bone complications (fractures, bone pain, disability) that negatively affect the patient's quality of life. Here, we first discuss the burden of skeletal complications in cancer bone metastasis. We then describe the pathophysiology of bone metastasis. Bone metastasis is a multistage process: long before the development of clinically detectable metastases, circulating tumor cells settle and enter a dormant state in normal vascular and endosteal niches present in the bone marrow, which provide immediate attachment and shelter, and only become active years later as they proliferate and alter the functions of bone-resorbing (osteoclasts) and bone-forming (osteoblasts) cells, promoting skeletal destruction. The molecular mechanisms involved in mediating each of these steps are described, and we also explain how tumor cells interact with a myriad of interconnected cell populations in the bone marrow, including a rich vascular network, immune cells, adipocytes, and nerves. We discuss metabolic programs that tumor cells could engage with to specifically grow in bone. We also describe the progress and future directions of existing bone-targeted agents and report emerging therapies that have arisen from recent advances in our understanding of the pathophysiology of bone metastases. Finally, we discuss the value of bone turnover biomarkers in detection and monitoring of progression and therapeutic effects in patients with bone metastasis.

Cadherins, Selectins, and Integrins in CAM-DR in Leukemia

The interaction between leukemia cells and the bone microenvironment is known to provide drug resistance in leukemia cells. This phenomenon, called cell adhesion-mediated drug resistance (CAM-DR), has been demonstrated in many subsets of leukemia including B- and T-acute lymphoblastic leukemia (B- and T-ALL) and acute myeloid leukemia (AML). Cell adhesion molecules (CAMs) are surface molecules that allow cell-cell or cell-extracellular matrix (ECM) adhesion. CAMs not only recognize ligands for binding but also initiate the intracellular signaling pathways that are associated with cell proliferation, survival, and drug resistance upon binding to their ligands. Cadherins, selectins, and integrins are well-known cell adhesion molecules that allow binding to neighboring cells, ECM proteins, and soluble factors. The expression of cadherin, selectin, and integrin correlates with the increased drug resistance of leukemia cells. This paper will review the role of cadherins, selectins, and integrins in CAM-DR and the results of clinical trials targeting these molecules.

The extracellular matrix: A key player in the pathogenesis of hematologic malignancies

Hematopoietic stem and progenitor cells located in the bone marrow lay the foundation for multiple lineages of mature hematologic cells. Bone marrow niches are architecturally complex with specific cellular, physiochemical, and biomechanical factors. Increasing evidence suggests that the bone marrow microenvironment contributes to the pathogenesis of hematological neoplasms. Numerous studies have deciphered the role of genetic mutations and chromosomal translocations in the development hematologic malignancies. Significant progress has also been made in understanding how the cellular components and cytokine interactions within the bone marrow microenvironment promote the evolution of hematologic cancers. Although the extracellular matrix is known to be a key player in the pathogenesis of various diseases, it's role in the progression of hematologic malignancies is less understood. In this review, we discuss the interactions between the extracellular matrix and malignant cells, and provide an overview of the role of extracellular matrix remodeling in sustaining hematologic malignancies.

The Metastatic Bone Marrow Niche in Neuroblastoma: Altered Phenotype and Function of Mesenchymal Stromal Cells

Background: The bone marrow (BM) is the main site of metastases and relapse in patients with neuroblastoma (NB). BM-residing mesenchymal stromal cells (MSCs) were shown to promote tumor cell survival and chemoresistance. Here we characterize the MSC compartment of the metastatic NB BM niche. Methods: Fresh BM of 62 NB patients (all stages), and control fetal and adult BM were studied by flow cytometry using well-established MSC-markers (CD34-, CD45-, CD90+, CD105+), and CD146 and CD271 subtype-markers. FACS-sorted BM MSCs and tumor cells were validated by qPCR. Moreover, isolated MSCs were tested for multilineage differentiation and Colony-forming-unit-fibroblasts (CFU-Fs) capacity. Results: Metastatic BM contains a higher number of MSCs (p < 0.05) with increased differentiation capacity towards the osteoblast lineage. Diagnostic BM contains a MSC-subtype (CD146+CD271-), only detected in BM of patients with metastatic-NB, determined by flow cytometry. FACS-sorting clearly discriminated MSC(-subtypes) and NB fractions, validated by mRNA and DNA qPCR. Overall, the CD146+CD271- subtype decreased during therapy and was detected again in the majority of patients at relapse. Conclusions: We demonstrate that the neuroblastoma BM-MSC compartment is different in quantity and functionality and contains a metastatic-niche-specific MSC-subtype. Ultimately, the MSCs contribution to tumor progression could provide targets with potential for eradicating resistant metastatic disease.

Adipocytes in hematopoiesis and acute leukemia: friends, enemies, or innocent bystanders?

The bone marrow is home to well-balanced normal hematopoiesis, but also the stage of leukemia's crime. Marrow adipose tissue (MAT) is a unique and versatile component of the bone marrow niche. While the importance of MAT for bone health has long been recognized, its complex role in hematopoiesis has only recently gained attention. In this review article we summarize recent conceptual advances in the field of MAT research and how these developments impact our understanding of MAT regulation of hematopoiesis. Elucidating routes of interaction and regulation between MAT and cells of the hematopoietic system are essential to pinpoint vulnerable processes resulting in malignant transformation. The concept of white adipose tissue contributing to cancer development and progression on the cellular, metabolic, and systemic level is generally accepted. The role of MAT in malignant hematopoiesis, however, is controversial. MAT is very sensitive to changes in the patient's metabolic status hampering a clear definition of its role in different clinical situations. Here, we discuss future directions for leukemia research in the context of metabolism-induced modifications of MAT and other adipose tissues and how this might impact on leukemia cell survival, proliferation, and antileukemic therapy.