Atorvastatin enhances bone marrow endothelial cell function in corticosteroid-resistant immune thrombocytopenia patients

Activation of PPARδ in bone marrow endothelial progenitor cells improves their hematopoiesis-supporting ability after myelosuppressive injury

Dysfunctional bone marrow (BM) endothelial progenitor cells (EPCs) with high levels of reactive oxygen species (ROS) are responsible for defective hematopoiesis in poor graft function (PGF) patients with acute leukemia or myelodysplastic neoplasms post-allotransplant. However, the underlying mechanism by which BM EPCs regulate their intracellular ROS levels and the capacity to support hematopoiesis have not been well clarified. Herein, we demonstrated decreased levels of peroxisome proliferator-activated receptor delta (PPARδ), a lipid-activated nuclear receptor, in BM EPCs of PGF patients compared with those with good graft function (GGF). In vitro assays further identified that PPARδ knockdown contributed to reduced and dysfunctional BM EPCs, characterized by the impaired ability to support hematopoiesis, which were restored by PPARδ overexpression. Moreover, GW501516, an agonist of PPARδ, repaired the damaged BM EPCs triggered by 5-fluorouracil (5FU) in vitro and in vivo. Clinically, activation of PPARδ by GW501516 benefited the damaged BM EPCs from PGF patients or acute leukemia patients in complete remission (CR) post-chemotherapy. Mechanistically, we found that increased expression of NADPH oxidases (NOXs), the main ROS-generating enzymes, may lead to elevated ROS level in BM EPCs, and insufficient PPARδ may trigger BM EPC damage via ROS/p53 pathway. Collectively, we found that defective PPARδ contributes to BM EPC dysfunction, whereas activation of PPARδ in BM EPCs improves their hematopoiesis-supporting ability after myelosuppressive therapy, which may provide a potential therapeutic target not only for patients with leukemia but also for those with other cancers.

Bone marrow macrophages are involved in the ineffective hematopoiesis of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a group of heterogeneous myeloid clonal disorders characterized by ineffective hematopoiesis. Accumulating evidence has shown that macrophages (MΦs) are important components in the regulation of tumor progression and hematopoietic stem cells (HSCs). However, the roles of bone marrow (BM) MΦs in regulating normal and malignant hematopoiesis in different clinical stages of MDS are largely unknown. Age-paired patients with lower-risk MDS (N = 15), higher-risk MDS (N = 15), de novo acute myeloid leukemia (AML) (N = 15), and healthy donors (HDs) (N = 15) were enrolled. Flow cytometry analysis showed increased pro-inflammatory monocyte subsets and a decreased classically activated (M1) MΦs/alternatively activated (M2) MΦs ratio in the BM of patients with higher-risk MDS compared to lower-risk MDS. BM MФs from patients with higher-risk MDS and AML showed impaired phagocytosis activity but increased migration compared with lower-risk MDS group. AML BM MΦs showed markedly higher S100A8/A9 levels than lower-risk MDS BM MΦs. More importantly, coculture experiments suggested that the HSC supporting abilities of BM MΦs from patients with higher-risk MDS decreased, whereas the malignant cell supporting abilities increased compared with lower-risk MDS. Gene Ontology enrichment comparing BM MΦs from lower-risk MDS and higher-risk MDS for genes was involved in hematopoiesis- and immunity-related pathways. Our results suggest that BM MΦs are involved in ineffective hematopoiesis in patients with MDS, which indicates that repairing aberrant BM MΦs may represent a promising therapeutic approach for patients with MDS.

Repair of dysfunctional bone marrow endothelial cells alleviates aplastic anemia

Aplastic anemia (AA) is a life-threatening disease characterized by bone marrow (BM) failure and pancytopenia. As an important component of the BM microenvironment, endothelial cells (ECs) play a crucial role in supporting hematopoiesis and regulating immunity. However, whether impaired BM ECs are involved in the occurrence of AA and whether repairing BM ECs could improve hematopoiesis and immune status in AA remain unknown. In this study, a classical AA mouse model and VE-cadherin blocking antibody that could antagonize the function of ECs were used to validate the role of BM ECs in the occurrence of AA. N-acetyl-L-cysteine (NAC, a reactive oxygen species scavenger) or exogenous EC infusion was administered to AA mice. Furthermore, the frequency and functions of BM ECs from AA patients and healthy donors were evaluated. BM ECs from AA patients were treated with NAC in vitro, and then the functions of BM ECs were evaluated. We found that BM ECs were significantly decreased and damaged in AA mice. Hematopoietic failure and immune imbalance became more severe when the function of BM ECs was antagonized, whereas NAC or EC infusion improved hematopoietic and immunological status by repairing BM ECs in AA mice. Consistently, BM ECs in AA patients were decreased and dysfunctional. Furthermore, dysfunctional BM ECs in AA patients led to their impaired ability to support hematopoiesis and dysregulate T cell differentiation toward proinflammatory phenotypes, which could be repaired by NAC in vitro. The reactive oxygen species pathway was activated, and hematopoiesis- and immune-related signaling pathways were enriched in BM ECs of AA patients. In conclusion, our data indicate that dysfunctional BM ECs with impaired hematopoiesis-supporting and immunomodulatory abilities are involved in the occurrence of AA, suggesting that repairing dysfunctional BM ECs may be a potential therapeutic approach for AA patients.

The serum lipid profiles in immune thrombocytopenia: Mendelian randomization analysis and a retrospective study

BACKGROUND

Immune thrombocytopenia (ITP) is an autoimmune hemorrhagic disease characterized by increased platelet destruction and impaired thrombopoiesis. The changes in platelet indices depend on the morphology and volume of platelets. Serum lipids have been found to affect platelet formation and activity in certain diseases, thus inducing the corresponding variation of platelet indices.

METHODS

Mendelian randomization (MR) analysis was performed based on databases. The clinical data from 457 ITP patients were retrospectively collected and analyzed, including platelet indices, serum lipids, hemorrhages and therapeutic responses.

RESULTS

MR analysis showed low high-density-lipoprotein-cholesterol (HDL-C), low apolipoprotein A-1, high triglyceride (TG) and high apolipoprotein B (ApoB) caused high platelet distribution width (PDW); high low-density-lipoprotein-cholesterol (LDL-C) increased mean platelet volume (MPV). In ITP, there were positive correlations between platelet count with TG, PDW with HDL-C and ApoB, and plateletcrit with TG and non-esterified fatty acid, and the correlation had gender differences. Bleeding scores were negatively correlated with cholesterol and LDL-C. LDL-C and homocysteine were risk factors for therapeutic responses.

CONCLUSIONS

Serum lipids, especially cholesterol were tightly correlated with platelet indices, hemorrhage and therapeutic effects in ITP patients. These results provide clinical references for the management of serum lipids, and highlight the necessity to further explore the relationship between lipids and pathogenesis of ITP.

TRIAL REGISTRATION

No: NCT05095896, October 14, 2021, retrospectively registered.

Hyperlipidemia in immune thrombocytopenia: a retrospective study

BACKGROUND

Immune thrombocytopenia (ITP) is an autoimmune hemorrhagic disease characterized by low platelet count and bleeding manifestations. However, some patients also suffered from atherosclerosis or even infarction. Apart from activated platelets, lipid metabolism takes a large part in the formation of atherosclerosis and metabolic syndrome. The lipid metabolic state in ITP patients is still unknown.

METHODS

We retrospectively reviewed 302 hospitalized ITP patients in our cohort, comparing their blood lipids, bleeding symptoms, metabolic diseases and treatment responses.

RESULTS

We found a high proportion of ITP patients suffered from hyperlipidemia, and other metabolic diseases including cardiovascular or cerebral atherosclerosis or infarction, hypertension, and type 2 diabetes. Hyperlipidemia was associated with severe bleeding and treatment refractoriness in ITP. Statins could alleviate thrombocytopenia and bleeding severity, and facilitate ITP treatment, while improving hyperlipidemia in ITP patients.

CONCLUSIONS

Our present study demonstrated that lipid metabolism might play an indispensable role in ITP pathogenesis and development.

Evaluation of the Effects of Atorvastatin and N-Acetyl Cysteine on Platelet Counts in Patients with Primary Immune Thrombocytopenia: An Exploratory Clinical Trial

Objective: We aimed to evaluate the efficacy of the combination of atorvastatin and N-acetyl cysteine in increasing platelet counts in patients with immune thrombocytopenia who were resistant to steroid therapy or had a relapse after treatment. Material and Methods: The patients included in this study received oral treatment of atorvastatin at a dose of 40 mg daily and N-acetyl cysteine at a dose of 400 mg every 8 h. The desired treatment duration was 12 months, but we included patients who completed at least 1 month of treatment in the analysis. The platelet counts were measured prior to the administration of the study treatment and in the first, third, sixth, and twelfth months of treatment (if available). A p value < 0.05 was considered statistically significant. Results: We included 15 patients who met our inclusion criteria. For the total treatment duration, the global response was 60% (nine patients); eight patients (53.3%) had a complete response and one patient (6.7%) had a partial response. Six patients (40%) were considered as having undergone treatment failure. Of the responder group, five patients maintained a complete response after treatment (55.5%), three patients maintained a partial response (33.3%), and one patient (11.1%) lost their response to the treatment. All of the patients in the responder group had significant increases in their platelet counts after treatment (p < 0.05). Conclusion: This study provides evidence of a possible treatment option for patients with primary immune thrombocytopenia. However, further studies are needed.

Therapeutic potential of MSCs and MSC-derived extracellular vesicles in immune thrombocytopenia

Immune thrombocytopenia (ITP) is an acquired autoimmune disease involving a variety of immune cells and factors. Despite being a benign disease, it is still considered incurable due to its complex pathogenesis. Mesenchymal stem cells (MSCs), with low immunogenicity, pluripotent differentiation, and immunomodulatory ability, are widely used in a variety of autoimmune diseases. In recent years, impaired bone marrow mesenchymal stem cells (BMMSCs) were found to play an important role in the pathogenesis of ITP; and the therapeutic role of MSCs in ITP has also been supported by increasing evidence with encouraging efficacy. MSCs hold promise as a new approach to treat or even cure refractory ITP. Extracellular vesicles (EVs), as novel carriers in the "paracrine" mechanism of MSCs, are the focus of MSCs. Encouragingly, several studies suggested that EVs may perform similar functions as MSCs to treat ITP. This review summarized the role of MSCs in the pathophysiology and treatment of ITP.

How we treat primary immune thrombocytopenia in adults

Primary immune thrombocytopenia (ITP) is an immune-mediated bleeding disorder characterized by decreased platelet counts and an increased risk of bleeding. Multiple humoral and cellular immune abnormalities result in accelerated platelet destruction and suppressed platelet production in ITP. The diagnosis remains a clinical exclusion of other causes of thrombocytopenia. Treatment is not required except for patients with active bleeding, severe thrombocytopenia, or cases in need of invasive procedures. Corticosteroids, intravenous immunoglobulin, and anti-RhD immunoglobulin are the classical initial treatments for newly diagnosed ITP in adults, but these agents generally cannot induce a long-term response in most patients. Subsequent treatments for patients who fail the initial therapy include thrombopoietic agents, rituximab, fostamatinib, splenectomy, and several older immunosuppressive agents. Other potential therapeutic agents, such as inhibitors of Bruton's tyrosine kinase and neonatal Fc receptor, are currently under clinical evaluation. An optimized treatment strategy should aim at elevating the platelet counts to a safety level with minimal toxicity and improving patient health-related quality of life, and always needs to be tailored to the patients and disease phases. In this review, we address the concepts of adult ITP diagnosis and management and provide a comprehensive overview of current therapeutic strategies under general and specific situations.

Current therapeutic strategies and perspectives in refractory ITP: What have we learned recently?

Immune thrombocytopenia (ITP) is an acquired autoimmune bleeding disorder featured by increased platelet destruction and deficient megakaryocyte maturation. First-line treatments include corticosteroids, intravenous immunoglobulin and intravenous anti-D immunoglobulin. Second-line treatments consist of rituximab, thrombopoietin receptor agonists and splenectomy. Although most patients benefit from these treatments, an individualized treatment approach is warranted due to the large heterogeneity among ITP patients. In addition, ITP patients may relapse and there remains a subset of patients who become refractory to treatments. The management of these refractory patients is still a challenge. This review aims to summarize emerging therapeutic approaches for refractory ITP in several categories according to their different targets, including macrophages, platelets/megakaryocytes, T cells, B cells, and endothelial cells. Moreover, current management strategies and combination regimens of refractory ITP are also discussed.

Plasma Metabolomics Identifies the Dysregulated Metabolic Profile of Primary Immune Thrombocytopenia (ITP) Based on GC-MS

ITP is a common autoimmune bleeding disorder with elusive pathogenesis. Our study was implemented to profile the plasma metabolic alterations of patients diagnosed with ITP, aiming at exploring the potential novel biomarkers and partial mechanism of ITP. The metabolomic analysis of plasma samples was conducted using GC-MS on 98 ITP patients and 30 healthy controls (HCs). Age and gender matched samples were selected to enter the training set or test set respectively. OPLS-DA, t-test with FDR correction and ROC analyses were employed to screen out and evaluate the differential metabolites. Possible pathways were enriched based on metabolomics pathway analysis (MetPA). A total of 85 metabolites were investigated in our study and 17 differential metabolites with diagnostic potential were identified between ITP patients and HCs. MetPA showed that the metabolic disorders of ITP patients were mainly related to phenylalanine, tyrosine and tryptophan biosynthesis, phenylalanine metabolism and glyoxylate and dicarboxylate metabolism. Additionally, we discriminated 6 differential metabolites and 5 enriched pathways in predicting the resistance to glucocorticoids in chronic ITP patients. The distinct metabolites discovered in our study could become novel biomarkers for the auxiliary diagnosis and prognosis prediction of ITP. Besides, the dysregulated pathways might contribute to the development of ITP.

Prophylactic NAC promoted hematopoietic reconstitution by improving endothelial cells after haploidentical HSCT: a phase 3, open-label randomized trial

BACKGROUND

Poor graft function (PGF) or prolonged isolated thrombocytopenia (PT), which are characterized by pancytopenia or thrombocytopenia, have become serious complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Our previous single-arm trial suggests that N-acetyl-L-cysteine (NAC) prophylaxis reduced PGF or PT after allo-HSCT. Therefore, an open-label, randomized, phase 3 trial was performed to investigate the efficacy and tolerability of NAC prophylaxis to reduce PGF or PT after allo-HSCT.

METHODS

A phase 3, open-label randomized trial was performed. Based on the percentage of CD34⁺VEGFR2 (CD309)⁺ endothelial cells (ECs) in bone marrow (BM) detected by flow cytometry at 14 days before conditioning, patients aged 15 to 60 years with acute leukemia undergoing haploidentical HSCT were categorized as low-risk (EC ≥ 0.1%) or high-risk (EC < 0.1%); patients at high risk were randomly assigned (2:1) to receive NAC prophylaxis or nonprophylaxis. The primary endpoint was PGF and PT incidence at +60 days post-HSCT.

RESULTS

Between April 18, 2019, and June 24, 2021, 120 patients with BM EC <0.1% were randomly assigned for NAC (group A, N = 80) or nonprophylaxis (group B, N = 40), and 105 patients with EC≥0.1% (group C) were also analyzed. The +60 days incidence of PGF and PT was 7.5% (95% CI, 1.7 to 13.3%) and 22.5% (95% CI, 9.1 to 35.9%) in group A and group B (hazard ratio, 0.317; 95% CI, 0.113 to 0.890; P = 0.021) and 11.4% (95% CI, 5.2 to 17.6%) in group C (hazard ratio, 0.643; 95% CI, 0.242 to 1.715; P = 0.373). Consistently, NAC prophylaxis gradually improved BM ECs and CD34⁺ cells in group A, whereas reduced their reactive oxygen species (ROS) levels post-HSCT. Within 60 days post-HSCT, the most common grade 3 to 5 adverse events for the NAC and control groups were infections (19/80 [24%] vs. 10/40 [25%]) and gastrointestinal adverse events (16/80 [20%] vs. 7/40 [18%]). There were no treatment-related deaths.

CONCLUSIONS

N-Acetyl-L-cysteine prophylaxis can prevent the occurrence of poor hematopoietic function and is well tolerated in haploidentical HSCT. It may offer a potential pathogenesis-oriented therapeutic approach for patients with poor hematopoietic function.

TRIAL REGISTRATION

This trial was registered at ClinicalTrials.gov as #NCT03967665.

Dysfunctional bone marrow endothelial progenitor cells are involved in patients with myelodysplastic syndromes

Background

Myelodysplastic syndromes (MDS) are a group of heterogeneous myeloid clonal disorders characterized by ineffective haematopoiesis and immune deregulation. Emerging evidence has shown the effect of bone marrow (BM) endothelial progenitor cells (EPCs) in regulating haematopoiesis and immune balance. However, the number and functions of BM EPCs in patients with different stages of MDS remain largely unknown.

Methods

Patients with MDS (N = 30), de novo acute myeloid leukaemia (AML) (N = 15), and healthy donors (HDs) (N = 15) were enrolled. MDS patients were divided into lower-risk MDS (N = 15) and higher-risk MDS (N = 15) groups according to the dichotomization of the Revised International Prognostic Scoring System. Flow cytometry was performed to analyse the number of BM EPCs. Tube formation and migration assays were performed to evaluate the functions of BM EPCs. In order to assess the gene expression profiles of BM EPCs, RNA sequencing (RNA-seq) were performed. BM EPC supporting abilities of haematopoietic stem cells (HSCs), leukaemia cells and T cells were assessed by in vitro coculture experiments.

Results

Increased but dysfunctional BM EPCs were found in MDS patients compared with HDs, especially in patients with higher-risk MDS. RNA-seq indicated the progressive change and differences of haematopoiesis- and immune-related pathways and genes in MDS BM EPCs. In vitro coculture experiments verified that BM EPCs from HDs, lower-risk MDS, and higher-risk MDS to AML exhibited a progressively decreased ability to support HSCs, manifested as elevated apoptosis rates and intracellular reactive oxygen species (ROS) levels and decreased colony-forming unit plating efficiencies of HSCs. Moreover, BM EPCs from higher-risk MDS patients demonstrated an increased ability to support leukaemia cells, characterized by increased proliferation, leukaemia colony-forming unit plating efficiencies, decreased apoptosis rates and apoptosis-related genes. Furthermore, BM EPCs induced T cell differentiation towards more immune-tolerant cells in higher-risk MDS patients in vitro. In addition, the levels of intracellular ROS and the apoptosis ratios were increased in BM EPCs from MDS patients, especially in higher-risk MDS patients, which may be therapeutic candidates for MDS patients.

Conclusion

Our results suggest that dysfunctional BM EPCs are involved in MDS patients, which indicates that improving haematopoiesis supporting ability and immuneregulation ability of BM EPCs may represent a promising therapeutic approach for MDS patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03354-2.

Atorvastatin restores imbalance of cluster of differentiation 4 (CD4)+ T cells in immune thrombocytopenia in vivo and in vitro

Immune thrombocytopenia (ITP) is an autoimmune haemorrhagic disease, in which the overactivation of T cells is crucial in the pathogenesis. Atorvastatin (AT), a lipid-lowering medicine, has shown promising immunomodulatory effects in certain inflammatory conditions. However, the immunoregulatory role of AT in ITP remains elusive. To investigate the effect of AT in the treatment of ITP, cluster of differentiation 4 (CD4)⁺ T cells were isolated from patients with ITP and cultured with different dosages of AT. We found that AT significantly inhibited cell proliferation, led to cell cycle arrest, induced apoptosis, and repressed the activation of CD4⁺ T cells in vitro. ITP murine models were then established, and results showed that AT treatment led to faster recovery of the platelet count to normal and exhibited comparable immunomodulatory function. Furthermore, we found the phosphorylation of mammalian target of rapamycin (mTOR), protein kinase B (AKT) and extracellular signal-regulated kinase (ERK), as well as activation of rat sarcoma virus (RAS) were all reduced dramatically after AT treatment in vitro. In conclusion, our present study demonstrated that AT could reinstate the functions of CD4⁺ T cells by inhibiting the excessive activation, proliferation, and survival of CD4⁺ T cells in ITP via the RAS/mitogen-activated protein kinase kinase (MEK)/ERK and the mTOR/phosphatidylinositol-3 kinase (PI3K)/AKT pathway. Therefore, we propose that AT could be used as a potential therapeutic option for ITP by restoring the over-activated cellular immunity.

Atorvastatin improves bone marrow endothelial progenitor cell function from patients with immune-related hemocytopenia

Background

Immune-related hemocytopenia (IRH) is a type of autoimmune disease that targets bone marrow hematopoietic cells. This study investigated the influence of atorvastatin on the functional aspects of bone marrow endothelial progenitor cells (BM EPCs) in IRH patients.

Methods

BM EPCs were isolated from 15 patients with IRH and 20 normal controls. The isolated BM EPCs were characterized by flow cytometry. Cell counting kit-8, flow cytometry, and Transwell migration assays were used to determine the proliferation, apoptosis, and migration of BM EPCs, respectively. Protein levels were determined by western blot assay.

Results

The BM EPCs isolated from IRH patients showed reduced proliferation, increased apoptosis, and attenuated migratory ability compared to those from normal controls. Western blot analysis showed that the protein level of p-p38 was significantly increased, while that of Phosphorylated protein kinase B (p-AKT) was significantly decreased in the BM EPCs from IRH patients, compared to BM EPCs from healthy subjects. Cell proliferation and migration were significantly enhanced by atorvastatin, recombinant human thrombopoietin, and SB20358 compared to the untreated BM EPCs from IRH patients. Atorvastatin, Recombinant human thrombopoietin (TPO), and SB20358 treatment significantly suppressed the protein levels of p-p38 protein, but increased those of p-AKT in BM EPCS from IRH patients.

Conclusions

In summary, atorvastatin increases the number and function of BM EPCs in IRH patients by regulating the p38 and AKT signaling pathways.

Improved function and balance in T cell modulation by endothelial cells in young people

Elderly individuals exhibit unbalanced bone marrow (BM) effector T cell subset differentiation, such as increased T helper type 1 (Th1) and T cytotoxic type 1 (Tc1) cell frequencies, but the underlying mechanism is still unclear. Endothelial cells (ECs), which are instructive components of the BM microenvironment, exhibit the phenotype of semi-professional antigen-presenting cells and regulate T cell recruitment and activation. Thus, we compared the frequency and function of BM ECs, especially their capacity to regulate effector T cell subsets, between young and elderly healthy individuals, and explored the underlying mechanism of this immunomodulatory discrepancy. Although the young and elderly EC percentages were comparable, young ECs showed fewer reactive oxygen species and better migratory and tube-forming abilities than elderly ECs. Notably, increased T cell activation molecules and inflammatory cytokines were found in elderly ECs which regulated T cells to differentiate into more proinflammatory T cells, including Th1 and Tc1 cells, than young ECs.

Predictive Value of High ICAM-1 Level for Poor Treatment Response to Low-Dose Decitabine in Adult Corticosteroid Resistant ITP Patients

Primary immune thrombocytopenia (ITP) is an autoimmune hemorrhagic disease. Endothelial cell activation/injury has been found in some autoimmune diseases including SLE, systemic sclerosis, and rheumatoid arthritis, but its role in ITP pathogenesis remains unclear. This study attempted to elucidate the correlation between endothelial dysfunction and disease severity of ITP and find related markers to predict response to low-dose decitabine treatment. Compared with healthy volunteers, higher plasma levels of soluble intercellular adhesion molecule-1 (ICAM-1), vascular endothelial growth factor (VEGF), and Angiopoietin-2 were found in adult corticosteroid resistant ITP patients. Notably, ICAM-1 levels were negatively correlated with the platelet count, and positively associated with the bleeding score. Recently, we have reported the efficacy and safety of low-dose decitabine in adult patients with ITP who failed for the first line therapies. Here, we evaluated the correlation of plasma ICAM-1 level with the efficacy of low-dose decitabine therapy for corticosteroid resistant ITP. A total of 29 adult corticosteroid resistant ITP patients who received consecutive treatments of low-dose decitabine were enrolled in this study. Fourteen patients showed response (nine showed complete response and five showed partial response). The levels of ICAM-1 before and after treatment were significantly higher in the non-responsive ITP patients than in the responsive patients. As shown in the multivariable logistic regression model, the odds of developing no-response to low-dose decitabine increased by 36.8% for per 5 ng/ml increase in plasma ICAM-1 level [odds ratio (OR) 1.368, 95% confidence interval (CI): 1.060 to 1.764]. In summary, this was the first study to elucidate the relationship between endothelial dysfunction and corticosteroid resistant ITP and identify the potential predictive value of ICAM-1 level for response to low-dose decitabine.

M2 macrophages, but not M1 macrophages, support megakaryopoiesis by upregulating PI3K-AKT pathway activity

Dysfunctional megakaryopoiesis hampers platelet production, which is closely associated with thrombocytopenia (PT). Macrophages (MФs) are crucial cellular components in the bone marrow (BM) microenvironment. However, the specific effects of M1 MФs or M2 MФs on regulating megakaryocytes (MKs) are largely unknown. In the current study, aberrant BM-M1/M2 MФ polarization, characterized by increased M1 MФs and decreased M2 MФs and accompanied by impaired megakaryopoiesis-supporting abilities, was found in patients with PT post-allotransplant. RNA-seq and western blot analysis showed that the PI3K-AKT pathway was downregulated in the BM MФs of PT patients. Moreover, in vitro treatment with PI3K-AKT activators restored the impaired megakaryopoiesis-supporting ability of MФs from PT patients. Furthermore, we found M1 MФs suppress, whereas M2 MФs support MK maturation and platelet formation in humans. Chemical inhibition of PI3K-AKT pathway reduced megakaryopoiesis-supporting ability of M2 MФs, as indicated by decreased MK count, colony-forming unit number, high-ploidy distribution, and platelet count. Importantly, genetic knockdown of the PI3K-AKT pathway impaired the megakaryopoiesis-supporting ability of MФs both in vitro and in a MФ-specific PI3K-knockdown murine model, indicating a critical role of PI3K-AKT pathway in regulating the megakaryopoiesis-supporting ability of M2 MФs. Furthermore, our preliminary data indicated that TGF-β released by M2 MФs may facilitate megakaryopoiesis through upregulation of the JAK2/STAT5 and MAPK/ERK pathways in MKs. Taken together, our data reveal that M1 and M2 MФs have opposing effects on MKs in a PI3K-AKT pathway-dependent manner, which may lead to new insights into the pathogenesis of thrombocytopenia and provide a potential therapeutic strategy to promote megakaryopoiesis.

Effect of Statins on Platelet Activation and Function: From Molecular Pathways to Clinical Effects

Purpose

Statins are a class of drugs widely used in clinical practice for their lipid-lowering and pleiotropic effects. In recent years, a correlation between statins and platelet function has been unveiled in the literature that might introduce new therapeutic indications for this class of drugs. This review is aimed at summarizing the mechanisms underlying statin-platelet interaction in the cardiologic scenario and building the basis for future in-depth studies.

Methods

We conducted a literature search through PubMed, Embase, EBSCO, Cochrane Database of Systematic Reviews, and Web of Science from their inception to June 2020.

Results

Many pathways could explain the interaction between statins and platelets, but the specific effect depends on the specific compound. Some could be mediated by enzymes that allow the entry of drugs into the cell (OATP2B1) and others by enzymes that mediate their activation (PLA2, MAPK, TAX2, PPARs, AKT, and COX-1), recruitment and adhesion (LOX-1, CD36, and CD40L), or apoptosis (BCL2). Statins also appear to have a synergistic effect with aspirin and low molecular weight heparins. Surprisingly, they seem to have an antagonistic effect with clopidogrel.

Conclusion

There are many pathways potentially responsible for the interactions between statins and platelets. Their effect appears to be closely related, and each single effect can be barely measured. Also, the same compound might have complex downstream signaling with potentially opposite effects, i.e., beneficial or deleterious. The multiple clinical implications that can be derived as a result of this interaction, however, represent an excellent reason to develop future in-depth studies.

Atorvastatin potentiates the chemosensitivity of human liver cancer cells to cisplatin via downregulating YAP1

Atorvastatin is a competitive inhibitor of β-hydroxy β-methylglutaryl-CoA reductase, which is involved in anticancer effects in numerous types of cancer, including in human liver cancer. However, its functions and underlying mechanisms of chemosensitivity in liver cancer remain to be elucidated. The present study investigated the effect of atorvastatin on cisplatin chemosensitivity and its molecular mechanisms, with a focus on the Yes1-associated transcriptional regulator (YAP1) protein. The present study demonstrated that atorvastatin significantly potentiated chemosensitivity to cisplatin in the liver cancer HepG2 and Huh-7 cell lines. Furthermore, cell survival and apoptosis in liver cancer cell lines were analyzed using MTT assay and flow cytometry, respectively. Atorvastatin suppressed HepG2 and Huh-7 cell viability in a dose-dependent manner, similar to cisplatin and paclitaxel. Subtoxic levels of atorvastatin significantly increased cisplatin-induced apoptosis in Huh-7 cells. Atorvastatin-promoted chemosensitivity was predominantly mediated by caspase 3, caspase 9 and poly-(ADP ribose)-polymerase activation, and YAP1 downregulation. Finally, YAP1 overexpression significantly reversed the susceptibility of Huh-7 cells to cisplatin. Overall, the results of the present study suggested the underlying mechanisms of atorvastatin chemosensitivity in inducing liver cancer cell apoptosis via downregulating YAP1 and implicated the potential application of atorvastatin-potentiated chemosensitivity in liver cancer therapy.

Different subsets of haematopoietic cells and immune cells in bone marrow between young and older donors

Young donors are reported to be associated with better transplant outcomes than older donors in allogeneic hematopoietic stem cell transplantation (allo-HSCT), but the mechanism is still unclear. The current study compared the different subsets of haematopoietic stem cells (HSCs) and their progenitors as well as immune cells in bone marrow (BM) between young and older donors. The frequencies of HSCs, multipotent progenitors (MPPs) and myeloid progenitors, including common myeloid progenitors (CMPs) and megakaryocyte-erythroid progenitors (MEPs), were decreased, whereas those of lymphoid progenitors, including multi-potent lymphoid progenitors (MLPs) and common lymphoid progenitors (CLPs), were increased in the BM of young donors compared with in that of older donors. Lower reactive oxygen species (ROS) levels were observed in BM HSCs and six progenitor lines in young donors. Furthermore, young donors demonstrated higher frequencies of naive T cells and immune suppressor cells, such as alternative macrophages (M2) and lower frequencies of memory T cells and immune effectors, including T helper-1 and T cytotoxic-1 cells, in BM than older donors. Multivariate analysis demonstrated that donor age was independently correlated with BM HSC frequency. Although further validation is required, our results suggest that the differences in the frequency and immune differentiation potential of HSCs in BM between young donors and older donors may partly explain the different outcomes of allo-HSCT.

Atorvastatin disrupts primary human brain microvascular endothelial cell functions via prenylation-dependent mitochondrial inhibition and oxidative stress

Primary human brain microvascular endothelial cell (HBMEC) is the major component of the blood-brain barrier (BBB). Atorvastatin, a HMG-CoA reductase inhibitor, is a cholesterol-lowering drug commonly used to reduce the risk for cardiovascular disease. Numerous studies have reported the pleiotropic effects of atorvastatin on endothelial cells, but the findings are controversial and inconclusive. In addition, little is known about the biological effects of atorvastatin on HBMEC. In this work, we demonstrate that atorvastatin at micromolar but not nanomolar concentrations induces dysfunctions of a number of HBMEC events, including differentiation into capillary network, migration and growth but not cell adhesion. We further show that the inhibitory effects of atorvastatin on HBMEC are independent of angiogenesis stimulators. Atorvastatin induces HBMEC apoptosis even in the presence of vascular endothelial growth factor (VEGF) and serum. Mechanism studies indicate that atorvastatin at micromolar concentration leads to protein prenylation inhibition, mitochondrial dysfunction and thereby subsequent oxidative stress and damage in HBMEC. Rescue experiments confirm that atorvastatin inhibits HBMEC functions via prenylation-dependent mitochondrial inhibition. Our work reveals the inhibitory effects of atorvastatin on HBMEC and suggests the possible negative influence of atorvastatin in blood-brain barrier.

Chemerin enhances the adhesion and migration of human endothelial progenitor cells and increases lipid accumulation in mice with atherosclerosis

Background

The role of adipokines in the development of atherosclerosis (AS) has received increasing attention in recent years. This study aimed to explore the effects of chemerin on the functions of human endothelial progenitor cells (EPCs) and to investigate its role in lipid accumulation in ApoE-knockout (ApoE−/−) mice.

Methods

EPCs were cultured and treated with chemerin together with the specific p38 mitogen-activated protein kinase (MAPK) inhibitor SB 203580 in a time- and dose-dependent manner. Changes in migration, adhesion, proliferation and the apoptosis rate of EPCs were detected. ApoE−/− mice with high-fat diet-induced AS were treated with chemerin with or without SB 203580. Weights were recorded, lipid indicators were detected, and tissues sections were stained.

Results

The data showed that chemerin enhanced the adhesion and migration abilities of EPCs, and reduced the apoptosis ratio and that this effect might be mediated through the p38 MAPK pathway. Additionally, chemerin increased the instability of plaques. Compared with the control group and the inhibitor group, ApoE−/− mice treated with chemerin protein had more serious arterial stenosis, higher lipid contents in plaques and decreased collagen. Lipid accumulation in the liver and kidney and inflammation in the hepatic portal area were enhanced by treatment with chemerin, and the size of adipocytes also increased after chemerin treatment. In conclusion, chemerin can enhance the adhesion and migration abilities of human EPCs and reduce the apoptosis ratio. In animals, chemerin can increase lipid accumulation in atherosclerotic plaques and exacerbate plaques instability. At the same time, chemerin can cause abnormal lipid accumulation in the livers and kidneys of model animals. After specifically blocking the p38 MAPK pathway, the effect of chemerin was reduced.

Conclusions

In conclusion, this study showed that chemerin enhances the adhesion and migration abilities of EPCs and increases the instability of plaques and abnormal lipid accumulation in ApoE−/− mice. Furthermore, these effects might be mediated through the p38 MAPK pathway.

Gut microbiome alterations and its link to corticosteroid resistance in immune thrombocytopenia

Quantitative metagenomic studies have linked the gut microbiota to autoimmune disorders. Here, we performed deep shotgun metagenomic sequencing of fecal samples from 99 immune thrombocytopenia (ITP) patients and 52 healthy controls. Dysbiosis in the gut microbiome of ITP was detected phylogenetically and functionally, and classifier based on species markers distinguished individuals with ITP from healthy controls. In particular, the abundance of Ruminococcus gnavus, Bifidobacterium longum and Akkermansia muciniphila was markedly increased in treatment-naïve ITP patients, and the alterations of microbial species were correlated with clinical indices. Functionally, the secondary bile acid biosynthesis and flagellar assembly were depleted in the gut microbiota of ITP, which may contribute to the onset of ITP by affecting the immune system. Furthermore, we found that corticosteroid treatment affected the gut microbiome of ITP. Compared with corticosteroid-sensitive ITP patients, we identified that the corticosteroid-resistant ITP patients displayed a distinct gut microbiome, which was different from that of the treatment-naïve ITP patients. Together, we provided support for the critical role of gut microbiota in the development of ITP and established a foundation for further research characterizing gut microbiota in relation to corticosteroid resistance of ITP.

Low-energy shock wave pretreatment recruit circulating endothelial progenitor cells to attenuate renal ischaemia reperfusion injury

Low‐energy shock wave (LESW) has been recognized as a promising non‐invasive intervention to prevent the organs or tissues against ischaemia reperfusion injury (IRI), whereas its effect on kidney injury is rarely explored. To investigate the protective role of pretreatment with LESW on renal IRI in rats, animals were randomly divided into Sham, LESW, IRI and LESW + IRI groups. At 4, 12, 24 hours and 3 and 7 days after reperfusion, serum samples and renal tissues were harvested for performing the analysis of renal function, histopathology, immunohistochemistry, flow cytometry and Western blot, as well as enzyme‐linked immunosorbent assay. Moreover, circulating endothelial progenitor cells (EPCs) were isolated, labelled with fluorescent dye and injected by tail vein. The fluorescent signals of EPCs were detected using fluorescence microscope and in vivo imaging system to track the distribution of injected circulating EPCs. Results showed that pretreatment with LESW could significantly reduce kidney injury biomarkers, tubular damage, and cell apoptosis, and promote cell proliferation and vascularization in IRI kidneys. The renoprotective role of LESW pretreatment would be attributed to the remarkably increased EPCs in the treated kidneys, part of which were recruited from circulation through SDF‐1/CXCR7 pathway. In conclusion, pretreatment with LESW could increase the recruitment of circulating EPCs to attenuate and repair renal IRI.

Autophagy in endothelial cells regulates their haematopoiesis-supporting ability

Background

Endothelial cells (ECs) function as an instructive platform to support haematopoietic stem cell (HSC) homeostasis. Our recent studies found that impaired bone marrow (BM) ECs are responsible for the defective haematopoiesis in patients with poor graft function (PGF), which is characterised by pancytopenia post-allotransplant. Although activated autophagy was reported to benefit ECs, whether EC autophagy plays a critical role in supporting HSCs and its effect on PGF patients post-allotransplant remain unclear.

Methods

To evaluate whether the autophagy status of ECs modulates their ability to support haematopoiesis, human umbilical vein endothelial cells (HUVECs) and primary BM ECs derived from healthy donors were subjected to knockdown or overexpression of Beclin-1 (an autophagy-related protein). Moreover, BM ECs derived from PGF patients were studied.

Findings

Beclin-1 knockdown significantly reduced the haematopoiesis-supporting ability of ECs by suppressing autophagy, which could be restored by activating autophagy via Beclin-1 upregulation. Moreover, autophagy positively regulated haematopoiesis-related genes in HUVECs. Subsequently, a prospective case-control study demonstrated that defective autophagy reduced Beclin-1 expression and the colony-forming unit (CFU) plating efficiency in BM ECs from PGF patients compared to matched patients with good graft function. Rapamycin, an autophagy activator, quantitatively and functionally improved BM ECs from PGF patients in vitro and enhanced their ability to support HSCs by activating the Beclin-1 pathway.

Interpretation

Our results suggest that the autophagy status of ECs modulates their ability to support haematopoiesis by regulating the Beclin-1 pathway. Defective autophagy in BM ECs may be involved in the pathogenesis of PGF post-allotransplant. Rapamycin provides a promising therapeutic approach for PGF patients.

Funding

Please see funding sources.

Granulocyte Colony-Stimulating Factor-Primed Unmanipulated Haploidentical Blood and Marrow Transplantation

Granulocyte colony-stimulating factor (G-CSF), a growth factor for neutrophils, has been successfully used for stem cell mobilization and T cell immune tolerance induction. The establishment of G-CSF-primed unmanipulated haploidentical blood and marrow transplantation (The Beijing Protocol) has achieved outcomes for the treatment of acute leukemia, myelodysplastic syndrome, and severe aplastic anemia with haploidentical allografts comparable to those of human leukocyte antigen (HLA)-matched sibling donor transplantation. Currently, G-CSF-mobilized bone marrow and/or peripheral blood stem cell sources have been widely used in unmanipulated haploidentical transplant settings. In this review, we summarize the roles of G-CSF in inducing T cell immune tolerance. We discuss the recent advances in the Beijing Protocol, mainly focusing on strategies that have been used to improve transplant outcomes in cases of poor graft function, virus infections, and relapse. The application of G-CSF-primed allografts in other haploidentical modalities is also discussed.

Pulmonary Infection Within 100 Days After Transplantation Impaired Platelet Recovery in Patients with Hematologic Malignancies: A Propensity-Score-Matched Analysis

Background

Pulmonary infection is one of the life-threatening complications occurring during allogeneic hematopoietic stem cell transplantation (alloHSCT), even when prophylactic measures have been employed. Few studies have investigated whether pulmonary infection affects platelet recovery during alloHSCT.

Material/Methods

We retrospectively reviewed 253 consecutive patients with hematologic diseases who received alloHSCT in our institute. Among them, 62 patients (25%) had pulmonary infection within 100 days after alloHSCT. Using the one-to-two propensity-score matching logistic model, 50 patients with pulmonary infection and 100 patients without were included based on age, disease and stage, time from diagnosis to transplantation, infused CD34⁺ cells, and mononuclear cells.

Results

The incidences of prolonged thrombocytopenia in patients with pulmonary infection were 44% (22/50) and 9% (9/100) in the corresponding matched group (P<0.001). The mean time for platelet engraftment in patients with and without pulmonary infection were 19.29±13.96 days and 13.94±4.12 days (P=0.012), respectively. Multivariable logistic regression showed that pulmonary infection was an independent risk factor for impaired platelet recovery (OR: 5.335, 95% CI: 2.735–10.407, P<0.001). Impaired platelet recovery was associated with shorter survival and higher treatment-related mortality.

Conclusions

Our results indicate that patients with pulmonary infection within 100 days after alloHSCT are more likely to suffer from impaired platelet recovery and have inferior long-term survival.

Current and emerging treatments for immune thrombocytopenia

Introduction: Immune thrombocytopenia (ITP) is an autoimmune disease. Even though there are many treatments available, some patients remain resistant to multiple treatments. Therefore, it is very important to develop new treatment options. Areas covered: Here, the authors summarize several current and emerging treatments developed for ITP in recent years. They include a summary of their mechanisms of action and clinical trial results. Expert opinion: At present, the first-line treatment of ITP is glucocorticoid and intravenous immunoglobulin (IVIg). Other traditional therapies include splenectomy, thrombopoietin (TPO), rituximab and other immunosuppressive agents. The several emerging treatments developed recently for ITP may change the treatment pattern in the future.

Prophylactic oral NAC reduced poor hematopoietic reconstitution by improving endothelial cells after haploidentical transplantation

Poor graft function (PGF) and prolonged isolated thrombocytopenia (PT) remain life-threatening complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Endothelial cells (ECs) play a crucial role in regulating hematopoiesis in the bone marrow (BM) microenvironment. However, whether the impaired BM ECs are responsible for defective hematopoiesis in PGF and PT patients requires clarification, and clinical management is challenging. Two prospective clinical trials were included in the current study. In the first trial (N = 68), PGF and PT patients demonstrated defective BM ECs pre-HSCT and impaired BM EC dynamic reconstitution at early time points post-HSCT, which was positively correlated with reactive oxygen species (ROS) levels. Receiver operating characteristic curves showed that BM EC < 0.1% pre-HSCT could identify high-risk patients with PGF and PT. The second trial enrolled patients (N = 35) with EC < 0.1% who accepted oral N-acetyl-l-cysteine (NAC; 400 mg 3 times per day) from -14 days pre-HSCT to +2 months post-HSCT continuously, whereas the remaining EC ≥ 0.1% patients (N = 39) received allo-HSCT only. Prophylactic NAC intervention was safe and effective in preventing the occurrence of PGF and PT in EC < 0.1% patients by promoting the dynamic reconstitution of BM ECs and CD34+ cells, along with reducing their ROS levels, which was further confirmed by in situ BM trephine biopsy analyses. These findings suggest that the impaired BM ECs pre-HSCT are responsible for the defective hematopoiesis in PGF and PT patients. Therefore, improvement of BM ECs through prophylactic NAC intervention may be a promising therapeutic approach to promote hematopoietic reconstitution post-HSCT. This trial was registered at www.clinicaltrials.gov as #NCT03236220 and #NCT02978274.

G-CSF-induced macrophage polarization and mobilization may prevent acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Macrophages (MΦs) are an important immune cell population that are essential for tissue homeostasis and disease pathogenesis. MΦs are now classified as either M1, which produce pro-inflammatory cytokines, or M2, which produce antiinflammatory cytokines. The impact of granulocyte colony-stimulating factor (G-CSF) on MΦs in humans is unclear. Moreover, little is known about the association between MΦ subsets in allografts and the occurrence of acute graft-versus-host disease (aGVHD) in patients who undergo allogeneic hematopoietic stem cell transplantation (allo-HSCT). In the current study, we found that the M1/M2 ratio was markedly decreased in both G-CSF-treated bone marrow (post-BM) and G-CSF-treated peripheral blood from healthy donors. Post-BM MΦs exhibited reduced migration and increased phagocytosis. Moreover, post-BM MΦs reduced the percentage of Th1 and Tc1 lineages and increased the percentage of Th2, Tc2, and Treg lineages. Patients who received BM grafts with a higher M1/M2 ratio exhibited a higher incidence of grade 2-4 aGVHD. In summary, our data indicate that G-CSF decreases the M1/M2 ratio in BM grafts from healthy donors, which may contribute to preventing the occurrence of grade 2-4 aGVHD in patients after allo-HSCT.

Poor graft function after allogeneic hematopoietic stem cell transplantation-an old complication with new insights☆

Poor graft function (PGF), characterized by pancytopenia, is a life-threatening complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT). PGF has become a growing obstacle that contributes to high morbidity and mortality after allo-HSCT, especially with the increasing use of haploidentical allo-HSCT, and clinical management 81870139, is challenging. Emerging evidence demonstrates that the bone marrow (BM) microenvironment plays a crucial role in maintaining and regulating hematopoiesis. Recent prospective case-control studies demonstrated that impaired BM microenvironments are involved in the pathogenesis of PGF. Moreover, in vitro treatment with N-acetyl-L-cysteine, a reactive oxygen species scavenger, could enhance the defective hematopoietic stem cells by repairing the dysfunctional BM microenvironment of PGF patients. Consequently, a better understanding of the pathogenesis of PGF may guide effective therapy and eventually improve the prognosis of allo-HSCT. Here, based on new insights into the BM microenvironment in PGF patients, we provide an overview of the pathogenesis and promising treatment strategies for PGF patients.

Dysfunctional Bone Marrow Mesenchymal Stem Cells in Patients with Poor Graft Function after Allogeneic Hematopoietic Stem Cell Transplantation

Poor graft function (PGF) is a life-threatening complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and is characterized by defective hematopoiesis. Mesenchymal stem cells (MSCs) have been shown to support hematopoiesis, but little is known about the role of MSCs in the pathogenesis of PGF. In the current prospective case-control study, we evaluated whether the number and function of bone marrow (BM) MSCs in PGF patients differed from those in good graft function (GGF) patients. We found that BM MSCs from PGF patients expanded more slowly and appeared flattened and larger, exhibiting more apoptosis and senescence than MSCs from GGF patients. Furthermore, increased intracellular reactive oxygen species, p-p53, and p21 (but not p38) levels were detected in MSCs from PGF patients. Moreover, the ability of MSCs to sustain hematopoiesis was significantly reduced in PGF patients, as evaluated by cell number, apoptosis, and the colony-forming unit-plating efficiency of CD34⁺ cells. In summary, the biologic characteristics of PGF MSCs are different from those of GGF MSCs, and the in vitro hematopoiesis-supporting ability of PGF MSCs is significantly lower. Although requiring further validation, our study indicates that reduced and dysfunctional BM MSCs may contribute to deficient hematopoiesis in PGF patients. Therefore, improvement of BM MSCs may represent a promising therapeutic approach for PGF patients after allo-HSCT.