Haploidentical hematopoietic stem cell transplantation as a first-line treatment for paediatric severe aplastic anemia: a single-center research.

MRD-HSCT is the first-line therapy for children with SAA, while it is not easy to find a compatible donor due to the Chinese one-child policy. IST has a high recurrence rate, a risk of clonal transformation. Thus, Haplo-HSCT, as a first-line treatment, has gradually attracted clinicians' attention. To evaluate the efficacy of Haplo-HSCT in children with SAA, we performed a retrospective study (2006.06-2021.01) of 210 patients with AA who received HSCT or IST in Beijing Children's Hospital. The OS and FFS rates were analyzed to evaluate the efficacy of Haplo-HSCT and IST. We found that from 2006 to 2021, 3- and 5-year cumulative survival rates were both 85.3% in the first-line Haplo group, 98.1% and 96.8% in the first-line IST group, both 85.7% in the ATG group (P = 0.866), both 100% in the ATG + TPO group (P = 0.016), and 99.1% and 97.2% in the ATG + eltrombopag group (P = 0.056). 3- and 5-year cumulative FFS rates were both 85.3% in the first-line Haplo-HSCT group and 67.5% and 66.2% in the first-line IST group (P = 0.033). Therefore, we believe that Haplo-HSCT can be a first-line treatment for paediatric SAA.

Advances in the treatment of solid tumors in children and adolescents.

Tumor is one of the leading causes of death in children (0 to 14-year-old) and adolescents (15 to 19-year-old) worldwide. Unlike adult tumors, childhood and adolescent tumors are unique in their type, molecular characteristics, and pathogenesis, and their treatment involves many challenges. In recent years, with the development of a large number of clinical studies, the survival rate of children and adolescents with tumors has improved significantly. The extensive research and application of optimized treatment regimens and new targeted drugs have led to new hope for the treatment of childhood and adolescent tumors. This article reviews the clinical and basic research and treatment of childhood and adolescent tumors and provides new ideas for the future development of precise treatment of childhood and adolescent tumors.

Immune Reconstitution in Pediatric Aplastic Anemia after Allogeneic Hematopoietic Stem-cell Transplantation.

Background: Previous studies had revealed that immune reconstitution (IR) after allogeneic hematopoietic stem-cell transplantation (allo-HSCT) affected the clinical prognosis of patients. However, few studies were based on pediatric patients and patients with aplastic anemia (AA). The purpose of this research was to analyze IR of pediatric AA after HSCT and further explore its clinical prognostic value. Methods: The whole of 61 pediatric patients with AA who underwent HSCT were enrolled. Lymphocyte subsets count in peripheral blood, CD4+/CD8+ T cell ratio, and serum concentration of immunoglobulins were detected using flow cytometry at regular intervals after HSCT. Results: Innate immunity recovered faster than adaptive immunity, T lymphocytes recovered faster than B lymphocytes. The number of transfused CD34+ cells and the implantation time of ANC significantly affected the early rapid IR of CD3+ T cells. The degree of HLA site coincidence significantly affected the early rapid IR of CD19+ B cells. The number of transfused MNC and CD34+ cells significantly affected the early rapid IR of CD56+ NK cells. The overall survival (OS) and failure-free survival (FFS) of CD56+ NK cells in early rapid IR group were higher than those in non-IR group. The CD3+ T cell early rapid IR group and CD8+ T cell early rapid IR group had higher OS than the non-IR group. Conclusion: Early rapid IR after HSCT is a good predictor of clinical prognosis in children with AA. This study provides a reasonable prediction for early rapid IR, which may improve clinical outcomes of children.

IL-1ß expression in bone marrow dendritic cells is induced by TLR2 agonists and regulates HSC function.

Hematopoietic stem/progenitor cells (HSPCs) reside in localized microenvironments, or niches, in the bone marrow that provide key signals regulating their activity. A fundamental property of hematopoiesis is the ability to respond to environmental cues such as inflammation. How these cues are transmitted to HSPCs within hematopoietic niches is not well established. Here, we show that perivascular bone marrow dendritic cells (DCs) express a high basal level of Toll-like receptor-1 (TLR1) and TLR2. Systemic treatment with a TLR1/2 agonist induces HSPC expansion and mobilization. It also induces marked alterations in the bone marrow microenvironment, including a decrease in osteoblast activity and sinusoidal endothelial cell numbers. TLR1/2 agonist treatment of mice in which Myd88 is deleted specifically in DCs using Zbtb46-Cre show that the TLR1/2-induced expansion of multipotent HPSCs, but not HSPC mobilization or alterations in the bone marrow microenvironment, is dependent on TLR1/2 signaling in DCs. Interleukin-1ß (IL-1ß) is constitutively expressed in both murine and human DCs and is further induced after TLR1/2 stimulation. Systemic TLR1/2 agonist treatment of Il1r1-/- mice show that TLR1/2-induced HSPC expansion is dependent on IL-1ß signaling. Single-cell RNA-sequencing of low-risk myelodysplastic syndrome bone marrow revealed that IL1B and TLR1 expression is increased in DCs. Collectively, these data suggest a model in which TLR1/2 stimulation of DCs induces secretion of IL-1ß and other inflammatory cytokines into the perivascular niche, which in turn, regulates multipotent HSPCs. Increased DC TLR1/2 signaling may contribute to altered HSPC function in myelodysplastic syndrome by increasing local IL-1ß expression.

Efficacy of hematopoietic stem cell transplantation in the treatment of children with non-severe aplastic anemia.

BACKGROUND: Non-severe aplastic anemia is more likely to develop into severe aplastic anemia, and there is no widely accepted treatment plan at present. Hematopoietic stem cell transplantation might be a new therapeutic strategy. METHODS: Retrospectively analyzed 32 patients with non-severe aplastic anemia who underwent hematopoietic stem cell transplantation from September 2007 to September 2020, and the 5-year estimated overall survival rate and the incidence of graft-versus-host disease were analyzed to evaluate the efficacy and safety of hematopoietic stem cell transplantation in the treatment of pediatric non-severe aplastic anemia. RESULTS: Thirty-two patients who underwent transplantation, 29 patients (90.6%) survived, 3 patients (9.4%) died. The incidence of acute graft-versus-host disease was 51.6% (16/31), including 15 cases (48.4%) of grade I-II and 1 case (3.2%) of grade III-IV. The incidence of chronic graft-versus-host disease was 38.7% (12/31). The 5-year overall survival rate was 91.8%. CONCLUSIONS: Hematopoietic stem cell transplantation is a practicable, safe, and effective treatment option for non-severe aplastic anemia pediatric patients who are suitable for transplant.

Haploidentical hematopoietic stem cell transplantation for pediatric patients with chronic active Epstein-Barr virus infection: a retrospective analysis of a single center.

BACKGROUND: This study aimed to evaluate the feasibility and clinical effect of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) for the treatment of pediatric patients with chronic active Epstein-Barr virus infection (CAEBV). METHODS: Children with CAEBV who did not have matched donors and underwent haplo-HSCT in Beijing Children's Hospital, Capital Medical University, from October 2016 to June 2020 were analyzed retrospectively. Data relating to the clinical manifestations, engraftment, and prognosis of the children were extracted from medical records. RESULTS: Twenty-five patients, including 16 males and 9 females, with an onset age of 5.0 ± 2.6 years and a transplantation age of 6.9 ± 2.9 years, were enrolled in this study. The mean time from diagnosis to transplantation was 3.8 (2.0-40.2) months. The mean observation time was 19.0 ± 12.0 months. Three patients received the reduced intensity conditioning regimen, and the remaining patients all received the modified myeloablative conditioning regimen. By the end of the follow-up, 23 patients were characterized by disease-free survival (DFS), 22 were characterized by event-free survival (EFS), and two died. One of the patients died of thrombotic microangiopathy (TMA), and another died of graft versus host disease (GVHD); this patient discontinued the treatment for economic reasons. The 3-year overall survival (OS) rate was estimated to be 92.0% ± 5.4%, and the 3-year EFS rate was estimated to be 87.4% ± 6.8%. All active patients survived after HSCT event-free. Acute GVHD degrees 1-3 were observed in ten patients (40.0%), and degree IV was observed in six (24.0%), who were all cured except for one patient. Chronic GVHD was observed in nine (36.0%), and most of these cases were mild. The incidence of TMA and veno-occlusive disease (VOD) was 28.0% and 4.0%. CONCLUSIONS: Haploidentical hematopoietic stem cell transplantation is safe and effective in the treatment of pediatric CAEBV and can be used as an alternative therapy without matched donors or emergency transplantation. Patients with active disease before HSCT also benefited from haplo-HSCT. Haplo-HSCT requires careful monitoring for complications, such as GVHD and TMA. Early detection of TMA and timely treatment can reduce mortality and can improve the survival rate.

Haploidentical haematopoietic stem cell transplantation for malignant infantile osteopetrosis and intermediate osteopetrosis: a retrospective analysis of a single centre.

OBJECTIVE: To evaluate the clinical efficacy of haploidentical haematopoietic stem cell transplantation (haplo-HSCT) for the treatment of malignant infantile osteopetrosis (MIOP) and intermediate osteopetrosis. METHODS: Children with MIOP and IOP who underwent haplo-HSCT in Beijing Children's Hospital, Capital Medical University, from January 2010 to May 2018 were retrospectively analysed. Data relating to the clinical manifestations, engraftment, and prognosis of the children were extracted from medical records. RESULTS: Twenty-seven patients, including 18 males and 9 females, with an onset age of 12 (0.04-72) months were enrolled in this study. The median time from diagnosis to transplantation was 4 (1-23) months. All patients received haplo-HSCT with a myeloablative conditioning regimen (including fludarabine, busulfan, and cyclophosphamide). Graft versus host disease (GVHD) prophylaxis was based on anti-human T lymphocyte porcine immunoglobulin/anti-human thymus globulin, methotrexate, and mycophenolate mofetil. The median observation time was 55.2 (0.3-126.2) months. By the end of follow-up, twenty patients survived and seven patients died. The 5 year overall survival rate was 73.9%. Stage I-II acute GVHD was observed in 20 patients, stage III GVHD in 1 patient and no patients had stage IV disease. Chronic GVHD was observed in 11 patients (40.7%) and was controlled by anti-GVHD therapy. CONCLUSIONS: Haplo-HSCT was an effective treatment for MIOP and IOP, with a high survival rate and significantly improved clinical symptoms. For patients with a vision impairment before HSCT, the improvement was slow after transplantation. The incidence of GVHD was high but mild and was effectively controlled by appropriate treatment. These data indicated that haplo-HSCT was a feasible treatment for MIOP and IOP.

Efficacy and safety of eltrombopag in the first-line therapy of severe aplastic anemia in children.

Eltrombopag is being investigated for the treatment of aplastic anemia (AA) by stimulating hematopoietic stem cell (HSC) proliferation. To evaluate the efficacy and safety of eltrombopag in the first-line therapy of pediatric AA. The present retrospective study assessed pediatric patients with newly diagnosed AA administered immunosuppressive therapy (IST) (rabbit ATG combined with CSA) with eltrombopag at a single center from March to September 2017. All patients were followed up for >2 years. A total of 14 patients (8 males), averagely aged 86 months, were enrolled in this study. Eltrombopag was administered with a median time to initiation of 19.5 days after IST; the median course of treatment was 253 days. Complete and overall response rates at 6 months were 64.3% (9/14 case) and 78.6% (11/14 cases), respectively. The survival rate was 100%, and no relapse occurred in responders. Eltrombopag was well-tolerated; however, the most common adverse events included indirect bilirubin elevation, jaundice, and transient liver-enzyme elevation. By the end of follow-up, bone marrow chromosomes were normal, and no abnormal myelodysplastic syndrome (MDS)-related clones appeared. Addition of eltrombopag to IST is associated with markedly increased complete response with respect to hematology in pediatric patients with SAA compared with a historical cohort, without intolerable side effects.

TLR7/8 agonist treatment induces an increase in bone marrow resident dendritic cells and hematopoietic progenitor expansion and mobilization.

There is accumulating evidence suggesting that toll-like receptor (TLR) signals play an important role in the regulation of hematopoietic stem/progenitor cells (HSPCs). TLR7/8 stimulation induces the myeloid differentiation of normal HSPCs and acute myeloid leukemia cells. However, the in vivo effect of TLR7/8 agonists on hematopoiesis is largely unknown. Here, we show that, similar to TLR4 and TLR2, treatment with the TLR7/8 agonist R848 induces an expansion of phenotypic hematopoietic stem cells (HSCs) with reduced repopulating potential and HSPC mobilization. In contrast to chronic TLR4 stimulation, treatment with R848 for 5 days did not induce a significant increase in myeloid-biased HSCs. Treatment with R848 results in a significant increase in classic dendritic cells (DCs) in the bone marrow, but a decrease in common dendritic cell progenitors and pre-DCs. Phenotypic analysis of DCs revealed that R848 treatment is associated with altered expression of certain chemokines, activation markers, and migratory receptors. Together, these data indicate that systemic administration of a TLR7/8 agonist has unique effects on hematopoiesis, including the expansion of DCs in the bone marrow, that might have clinical relevance to augment responses to certain immunotherapies, such as cancer vaccines and immune checkpoint blockade.

Insensitive to PTH of CD8+ T cells regulate bone marrow mesenchymal stromal cell in aplastic anemia patients.

Aplastic anemia (AA) is a rare disorder characterized by the suppression of bone marrow function resulting in progressive pancytopenia. The pathogenesis of AA is complex and involves an abnormal hematopoietic microenvironment, hematopoietic stem cell/progenitor cell deficiencies, and immunity disorders. However, the underlying mechanism of the disease is still not fully uncovered. In this research, we collected both donor and patient samples and found suppressed proliferation, abnormal differentiation as well as increased apoptosis of patient mesenchymal stem cells (MSCs). Considering the close relationship of parathyroid hormone (PTH) and MSCs differentiation, further studies showed that although patients maintained normal serum PTH level, their CD8+ T cells possessed lower PTH receptors. The insensitive to PTH of patients' CD8+ T cells finally lead to reduced expression of key Wnt factors. In all, bone marrow CD8+ T cells may play an important role in inducing MSCs adipogenesis and osteogenesis imbalancement.

Bone marrow dendritic cells regulate hematopoietic stem/progenitor cell trafficking.

A resident population of dendritic cells (DCs) has been identified in murine bone marrow, but its contribution to the regulation of hematopoiesis and establishment of the stem cell niche is largely unknown. Here, we show that murine bone marrow DCs are perivascular and have a type 2 conventional DC (cDC2) immunophenotype. RNA expression analysis of sorted bone marrow DCs shows that expression of many chemokines and chemokine receptors is distinct from that observed in splenic cDC2s, suggesting that bone marrow DCs may represent a unique DC population. A similar population of DCs is present in human bone marrow. Ablation of conventional DCs (cDCs) results in hematopoietic stem/progenitor cell (HSPC) mobilization that is greater than that seen with ablation of bone marrow macrophages, and cDC ablation also synergizes with G-CSF to mobilize HSPCs. Ablation of cDCs is associated with an expansion of bone marrow endothelial cells and increased vascular permeability. CXCR2 expression in sinusoidal endothelial cells and the expression of two CXCR2 ligands, CXCL1 and CXCL2, in the bone marrow are markedly increased following cDC ablation. Treatment of endothelial cells in vitro with CXCL1 induces increased vascular permeability and HSPC transmigration. Finally, we show that HSPC mobilization after cDC ablation is attenuated in mice lacking CXCR2 expression. Collectively, these data suggest that bone marrow DCs play an important role in regulating HSPC trafficking, in part, through regulation of sinusoidal CXCR2 signaling and vascular permeability.

Fabrication and characterization of a novel corn straw/modified ammonium lignosulfonate bio-composite strengthened by polyethylenimine pretreatment.

This study focuses on the development of novel bio-composites via the pretreatment of corn straw particles (PCSP) and modified ammonium lignosulfonate (MAL) as a binder. The corn stalk particles (CSP) were pretreated with polyethylenimine (PEI) to enhance compatibility. The effects of PEI dosage on the mechanical properties and dimensional stability were examined, where PEI pretreatment improved the interfacial properties of MAL and CSP considerably. The optimum values of the PCSP/MAL composites complied with the Chinese national standard for load-bearing particleboard. Furthermore, the results confirmed that PEI pretreatment resulted in good surface activity and exhibited a favorable effect on the crystallinity of the PCSP/MAL composites. The storage moduli E' and tan δ peak of the PCSP/MAL composites were considerably greater than those of the CSP/MAL composites. The fractured morphology of the composites clearly showed that PEI pretreatment improves the interfacial adhesion of MAL and CSP.

Eltrombopag for Delayed Platelet Recovery and Secondary Thrombocytopenia Following Allogeneic Stem Cell Transplantation in Children.

The delay in platelet recovery after hematopoietic stem cell transplantation (HSCT) is closely related to the overall survival rate of transplanted children. The use of platelet-producing agents such as eltrombopag and romiplostim has made great progress in treating diseases such as immune thrombocytopenia and aplastic anemia. However, the use of such drugs in patients with thrombocytopenia after transplantation, especially in children, is rare. This study aimed to report eltrombopag treatment for 3 children with primary platelet engraftment failure and secondary thrombocytopenia after allogeneic HSCT. Of these patients, 2 had platelets stabilized at ≥50×10/L after eltrombopag treatment and subsequent withdrawal of eltrombopag. All 3 patients showed no clear adverse reactions. The results indicated a wide application prospect of eltrombopag treatment in children with thrombocytopenia after allogeneic HSCT.

[Study on Immunophenotypes and Gene of Acute Lymphoblastic Leukemia--Review].

Transplantation-associated thrombotic microangiopathy (TA-TMA) is one of the fatal complications of hematopoietic stem cell transplantation(HSCT). The pathogenesis of TA-TMA has not been fully elucidated. The latest researches show that the abnormal activation of the complement system may lead to widespread endothelial injury which may play an important role in the pathogenesis of this disease. Incontrotable hypertension, proteinuria, increase of soluble C5b-9 concentration and early pericardial effusion are the risk factors of TA-TMA . In this review, the latest advances of pathogenesis, early diagnosis, treatment and other aspects of the progress of TA-TMA are summarized, so as to provide new ideas to early diagnosis and treatment in TA-TMA.

Hematopoietic stem cell transplantation without in vivo T-cell depletion for pediatric aplastic anemia: A single-center experience.

For young patients, HLA-MRD HSCT is the first-line treatment of SAA. However, due to China's birth control policy, few patients could find suitable sibling donors and HLA-MUD. More and more transplantation centers have used Haplo-D as the donor source for young adult and pediatric patients. However, studies with larger amount of pediatric patients are rare. We retrospectively analyzed the data of children with AA who were treated with allogeneic HSCT and compared the therapeutic efficacy of Haplo-HSCT and MRD/MUD group. A total of 62 patients were enrolled. Implantation was successfully performed in 58 patients. There was no significant difference in the time for reconstruction of hematopoietic function between patients in the two groups. Thirty-two had grade I-IV aGVHD with incidence of 51.61%. The incidence of aGVHD was 79.41% for patients in the Haplo-HSCT, significantly higher than that of 17.86% for patients in the MRD/MUD group (P < .01). However, the incidence of cGVHD was not significantly different between patients in the two groups (26.47% vs 10.71%, P = .09), the incidence of CMV infection was 28.57% and 52.94% for patients in the MRD/MUD and Haplo group, respectively, showing no significant difference (P = .053). The incidence of EBV infection was 47.06% for patients in the Haplo group and 28.57% for patients in the MRD/MUD group, showing no significant difference (P = .11). However, the 3- and 5-year cumulative OS and FFS rates showed statistically significant difference in the two groups, P = .012 and .045, respectively. Compared to Haplo-HSCT, MRD/MUD is more economic. In this study, we achieved good Haplo transplantation results. The incidences of cGVHD and CMV/EBV were not significantly different between Haplo group and MRD/MUD group. Although OS and FFS of the Haplo group were not as good as those of the MRD/MUD group, it is still acceptable as an alternative treatment under emergency.

Prognostic significance of osteopontin in acute myeloid leukemia: A meta-analysis.

Osteopontin (OPN) has been investigated in the field of tumor research for several years. However, the prognostic role of OPN overexpression in acute myeloid leukemia (AML) remains controversial. A meta-analysis of four studies, including a total of 492 patients, was performed to determine the association of OPN with overall survival (OS) in AML patients. The random-effects model of Der Simonian and Laird was used to synthesize data; hazard ratio (HR) with its 95% confidence interval (CI) was used as the effect size estimate. It was observed that serum-based OPN was inversely correlated with OS and the difference was statistically significant (HR=1.83; 95% CI: 1.43-2.35; P<0.001). Experimental findings indicate that OPN overexpression is associated with a poor prognosis in AML and may be of prognostic value for AML stage and metastasis.

Haploidentical hematopoietic stem cell transplantation without total body irradiation for pediatric acute leukemia: a single-center experience.

Hematopoietic stem cell transplantation (HSCT) is a promising method for therapy of pediatric patients with acute leukemia. However, less availability of matched donors limited its wide application. Recently, haploidentical HSCT has become a great resource. Here, we have retrospectively reported our experience of 20 pediatric patients with acute leukemia who underwent haploidentical HSCT without total body irradiation (TBI) myeloablative regimen in our center from November 2007 to June 2014. All the patients attained successful HSCT engraftment in terms of myeloid and platelet recovery. Thirteen patients developed grade I-IV acute graft-versus-host disease (a-GVHD). The incidence of grade I-II a-GVHD, grade III-IV a-GVHD, and chronic GVHD (c-GVHD) was 45%, 20%, and 25%, respectively. The mean myeloid and platelet recovery time was 13.20±2.41 and 19.10±8.37 days. The median follow-up time was 43.95±29.26 months. During the follow-up, three patients died. The overall survival (OS) rate was 85%. The present study indicated that haploidentical HSCT without TBI myeloablative regimen significantly improved the OS rate of pediatric patients with acute leukemia.

Targeting stem cell niche can protect hematopoietic stem cells from chemotherapy and G-CSF treatment.

INTRODUCTION: Hematopoietic stem/progenitor cells (HSPCs) reside in a tightly controlled local microenvironment called bone marrow niche. The specialized microenvironment or niche not only provides a favorable habitat for HSPC maintenance and development but also governs stem cell function. METHOD: We investigated the effect of cytotoxic drugs on bone marrow niche. To mimic the multiple rounds of chemotherapy followed by autologous hematopoietic stem cells (HSCs) transplantation in a clinical setting, we further verified the hypothesis that targeting the niche might improve stem cell-based therapies in mouse models. RESULTS: We found that multiple rounds of cytotoxic drug treatment significantly disrupted niche and serum osteocalcin level was significantly reduced after treatment in autologous HSPCs transplanted patients (P = 0.01). In mouse models, the number of CD45(-)Ter119(-)OPN(+) osteoblasts was significantly reduced after multiple rounds of chemotherapies and granulocyte colony stimulating factor (G-CSF) treatment (P < 0.01). Parathyroid hormone (PTH) or receptor activator of nuclear factor kappa-B ligand (RANKL) treatment significantly increased the number of HSCs mobilized into peripheral blood (PB) for stem cell harvesting and protected stem cells from repeated exposure to cytotoxic chemotherapy. Treatments with G-CSF and PTH significantly increased the preservation of the HSC pool (P < 0.05). Moreover, recipient mice transplanted with circulation HSPCs that were previously treated with PTH and RANKL showed robust myeloid and lymphatic cell engraftment compared to the mice transplanted with HSCs after chemotherapy or G-CSF treatment. CONCLUSION: These data provide new evidence that the niche may be an important target for drug-based stem cell therapy.

[Changes of angiopoietin 1 expression in G-CSF induced hematopoietic stem progenitor cells mobilization].

OBJECTIVE: To investigate the changes and mechanism of angiopoietin1 (Ang1) in murine bone marrow during G-CSF induced mobilization of hematopoietic stem/progenitor cell. METHODS: The proportion of Lin-Sca1⁺cKit⁺ (LSK) cells in peripheral blood of C57BL/6 mice before and after G-CSF mobilization was detected by flow cytometry. Expression changes of Ang1 and osteocalcin (OCN) during HSC mobilization were determined by immunohistochemistry, enzyme linked immunosorbent assay (ELISA) and real-time fluorescence quantitative PCR. The number of osteoblasts in the bone marrow was counted under the microscope. RESULTS: After treated with G-CSF, the proportion of LSK cells in peripheral blood significantly increased from the controls (0.04 ± 0.01)% to (0.61 ± 0.05)% at day 5 (P<0.05). Before G-CSF mobilization, the endosteum cells expressed higher level of OCN and Ang1 than that of bone marrow nucleated cells. The mRNA expression level of OCN was significantly reduced from 28.64 ± 8.61 in the controls to 12.55 ± 7.06 on day 3 and 4.75 ± 1.62 on day 5, and the expression level of Ang1 also declined from 2.84 ± 0.95 in the controls to 0.93 ± 0.30 on day 3 and to 0.92 ± 0.22 on day 5 after G-CSF mobilization. The number of endosteum osteoblasts was significantly decreased after mobilization (P<0.05). The Ang1 expression was decreased in the BM after mobilization. The serum OCN was significantly reduced from (24.11 ± 3.17) ng/ml in the controls to (9.96 ± 2.16) ng/ml on day 3 and (8.43 ± 2.62) ng/ml on day 5, and the Ang1 also declined from (2.24 ± 0.52) ng/ml in the controls to (1.21±0.38) ng/ml on day 3 and (0.90±0.24) ng/ml on day 5. CONCLUSION: In G-CSFinduced HSPC mobilization, the bone marrow osteoblasts retraction causes reduction of Ang1, and the reduction of Ang1 may contribute to HSPC mobilization.

Granulocyte Colony-Stimulating Factor Induces Osteoblast Inhibition by B Lymphocytes and Osteoclast Activation by T Lymphocytes during Hematopoietic Stem/Progenitor Cell Mobilization.

In the bone marrow (BM), hematopoietic stem and progenitor cells (HSPCs) reside in specialized niches near osteoblast cells at the endosteum. HSPCs that egress to peripheral blood are widely used for transplant, and mobilization is most commonly performed with recombinant human granulocyte colony-stimulating factor (G-CSF). However, the cellular targets of G-CSF that initiate the mobilization cascade and bone remodeling are not completely understood. Here, we examined whether T and B lymphocytes modulate the bone niche and influence HSPC mobilization. We used T and B defective mice to show that G-CSF-induced mobilization of HSPCs correlated with B lymphocytes but poorly with T lymphocytes. In addition, we found that defective B lymphocytes prevent G-CSF-mediated osteoblast disruption, and further study showed BM osteoblasts were reduced coincident with mobilization, induced by elevated expression of dickkopf1 of BM B lymphocytes. BM T cells were also involved in G-CSF-induced osteoclast activation by regulating the Receptor Activator of Nuclear Factor-κ B Ligand/Osteoprotegerin (RANKL/OPG) axis. These data provide evidence that BM B and T lymphocytes play a role in G-CSF-induced HSPC mobilization by regulating bone remodeling.