共表达EGFP和CXCR4的大鼠骨髓间充质干细胞的构建及其迁移能力

目的 构建携带增强绿色荧光蛋白(EGFP)及CXCR4慢病毒载体并实现其在大鼠骨髓间充质干细胞(rMSCs)中的表达,观察转CXCR4基因后对rMSCs迁移能力的影响。方法 RT-PCR扩增大鼠CXCR4编码区片段,将其插入慢病毒载体质粒PNL-IRES2-EGFP,获得的PNL-CXCR4-IRES2-EGFP与包装及包膜质粒用脂质体法共转染293T细胞,包装生产慢病毒。所获慢病毒转染rMSCs后,用RT-PCR、Western blot、细胞免疫荧光组织化学和流式细胞术检测转CXCR4基因rMSCs组、转空载体rMSCs组中CXCR4表达情况。利用Transwell方法检测两组rMSCs在SDF-1作用下的迁移能力。结果 双酶切和测序证实,PNL-CXCR4-IRES2- EGFP构建正确,转CXCR4基因rMSCs组CXCR4表达明显增多,在SDF-1α作用下迁移能力明显增强。结论 成功构建带有EGFP和大鼠CXCR4的慢病毒载体,并获得CXCR4-rMSCs基因工程细胞,为深入研究SDF/CXCR4轴在rMSCs向损伤组织定向迁移中的作用奠定了基础。     

Neutrophil circulation and release from bone marrow during hypothermia.

The effect of hypothermia on neutrophil circulation and release from bone marrow has been studied. Pigs were anesthetized and maintained at 37 degrees C or surface cooled to 29 degrees C over 60 min. As the core temperature was reduced to 29 degrees C, the number of circulating neutrophils (X 10(9) per liter) fell from 6.0 +/- 0.6 to 2.3 +/- 0.3 by 60 min. No significant change in the number of circulating mature or immature neutrophils was observed over the 4 h of observation at 29 degrees C. Neutrophil demargination after administration of intravenous catecholamines was similar at 37 and 29 degrees C. Steroid stimulation of bone marrow to release neutrophils was markedly impaired at 29 degrees C. Circulating mature neutrophils in normothermic pigs increased from 5.6 +/- 1.2 to 10.4 +/- 1.2 by 120 min after administration of intravenous hydrocortisone sodium succinate. Circulating immature neutrophils increased from 1.7 +/- 0.3 to 5.3 +/- 0.4. At 29 degrees C, no significant changes in the number of circulating mature or immature neutrophils occurred. Endotoxin also failed to stimulate neutrophil release from the bone marrow. Furthermore, a marked neutropenia occurred in hypothermic pigs after intravenous endotoxin, which persisted for the 3 h of observation. Neutrophil circulation and release from bone marrow are compromised by hypothermia, which may increase the risk for bacterial infection.     

G-CSF induces stem cell mobilization by decreasing bone marrow SDF-1 and up-regulating CXCR4

Granulocyte colony-stimulating factor (G-CSF) induced hematopoietic stem cell mobilization is widely used for clinical transplantation; however, the mechanism is poorly understood. We report here that G-CSF induced a reduction of the chemokine stromal cell derived factor 1 (SDF-1) and an increase in its receptor CXCR4 in the bone marrow (BM), whereas their protein expression in the blood was less affected. The gradual decrease of BM SDF-1, due mostly to its degradation by neutrophil elastase, correlated with stem cell mobilization. Elastase inhibition reduced both activities. Human and murine stem cell mobilization was inhibited by neutralizing CXCR4 or SDF-1 antibodies, demonstrating SDF-1 CXCR4 signaling in cell egress. We suggest that manipulation of SDF-1 CXCR4 interactions may be a means with which to control the navigation of progenitors between the BM and blood to improve the outcome of clinical stem cell transplantation.     

系统性红斑狼疮患者骨髓细胞培养上清对间充质干细胞衰老作用的研究

为了探讨SLE患者骨髓局部微环境对间充质干细胞(MSC)衰老的影响及机制。首先收集性别、年龄匹配的健康对照者及SLE患者骨髓各6例,留取上清液并灭活补体;以含10%骨髓上清的DMEM/F12培养基模拟机体骨髓局部微环境,培养脐带来源的MSC;SA-β-gal染色并计数阳性MSC比例;real time PCR及western blot法分别检测MSC的p53、p21基因及蛋白表达水平;荧光显微镜观察MSC核内DNA损伤标记53BP1的表达情况;CCK8检测细胞活力;流式细胞术检测Annexin V/PI评估细胞凋亡。结果显示,与正常对照相比,SLE患者骨髓上清可显著增加β半乳糖苷酶阳性MSC细胞比例,且上调p53和p21的表达量;在SLE患者骨髓上清处理的条件下,MSC细胞内与DNA损伤反应有关的标志性蛋白53BP1的表达水平显著增高;SLE患者骨髓上清还能够明显抑制MSC的增殖能力。这提示SLE患者骨髓上清促进MSC衰老,其机制可能在于诱导MSC细胞核内DNA损伤反应。     

SDF-1/CXCR4增强骨髓间质干细胞的造血支持作用

目的探讨基质细胞衍生因子-1(SDF-1)/CXCR4在骨髓间质干细胞(MSCs)支持CD34 造血干/祖细胞(HSPCs)扩增中的作用。方法在长期培养基(LTC)中,以大鼠骨髓MSCs作为饲养层体外扩增骨髓CD34 细胞,每周分别加入SDF-1、SDF-1抗体或CXCR4抗体至5周。计算CD34 细胞数和集落形成细胞(CFC)数,以评价造血支持功能。为评估SDF-1/CXCR4对CD34 细胞增殖周期的影响,进行了杀伤试验以计算增殖指数。流式细胞术检测MSCs和CD34 细胞中SDF-1与CXCR4的表达;ELISA检测MSCs和CD34 细胞培养基中SDF-1的含量。结果CD34 细胞数、CFC数和增殖指数在加入SDF-1后明显增加(P<0.01),加入SDF-1抗体或CXCR4抗体后明显减少(分别为P<0.05,P<0.01)。CD34 细胞表面表达CXCR4,MSCs则不表达;MSCs细胞内表达SDF-1,而CD34 细胞不表达。在MSCs培养基中检测到SDF-1,在CD34 细胞培养基中未发现。结论SDF-1/CXCR4在骨髓MSCs支持HSPCs扩增中起重要作用。     

Macrophages and their subpopulations following allogeneic bone marrow transplantation for chronic myeloid leukaemia

A morphometric and immunohistochemical study was performed on 354 bone marrow trephine biopsies derived from 126 patients with chronic myeloid leukaemia (CML) before and after allogeneic bone marrow transplantation (BMT). The purpose of this investigation was to evaluate the macrophage population, including several subsets and their dynamics in the posttransplant period. In addition to the total CD68⁺ resident (mature) macrophages the so-called activated fraction identified by its capacity to express α-d-galactosyl residues, the pseudo-Gaucher cells (PGCs) and the iron-laden histiocytic reticular cells were also considered. Following immuno- and lectin-histochemical staining morphometric analysis was carried out on sequential postgraft bone marrow specimens at standardized intervals. Compared to the normal bone marrow and calculated per haematopoiesis (cellularity) an overall decrease of about 40–50% in the quantity of CD68⁺ macrophages and the BSA-I⁺ subpopulation was detectable in the early posttransplant period (9–45 days after BMT). Noteworthy was the temporal recurrence of PGCs in the engrafted bone marrow, which was not associated with a clonally transformed cell population or leukaemic relapse. Reappearance of postgraft PGCs was most prominent in the first 2 months after BMT. This conspicuous feature was presumed to be functionally associated with a pronounced degradation of cell debris following pretransplant myelo-ablative therapy (scavenger macrophages). Evidence for an activation of the BSA-I⁺ macrophage subset was derived from the identical carbohydrate-binding capacity shown by the PGCs. In the regenerating haematopoiesis shortly after BMT a significant correlation between the number of BSA-I⁺ macrophages and erythroid precursor cells was determinable. This result implicates a close functional relationship between postgraft reconstitution of erythropoietic islets and centrally localized activated macrophages. In conclusion, findings emerging from this study included the reappearance of PCGs in the engrafted bone marrow independently of a leukaemic relapse and the significant association of the activated BSA-I⁺ macrophage subset with the recovery of erythropoiesis. Received: 31 January 2000 / Accepted: 6 March 2000     

Near-infrared molecular imaging of tumors via chemokine receptors CXCR4 and CXCR7

The chemokine CXCL12/SDF-1 and its receptors CXCR4 and CXCR7 play a major role in tumor invasion, proliferation and metastasis. Since both receptors are overexpressed on distinct tumor cells and on the tumor vasculature, we evaluated their potential as targets for detection of cancers by molecular imaging. We synthesized conjugates of CXCL12 and the near-infrared (NIR) fluorescent dye IRDye^®800CW, tested their selectivity, sensitivity and biological activity in vitro and their feasibility to visualize tumors in vivo. Purified CXCL12-conjugates detected in vitro as low as 500 A764 human glioma cells or MCF-7 breast cancer cells that express CXCR7 alone or together with CXCR4. Binding was time- and concentration-dependent, and the label could be competitively displaced by the native peptide. Control conjugates with bovine serum albumin or lactalbumin failed to label the cells. In mice, the conjugate distributed rapidly. After 1–92 h, subcutaneous tumors of human MCF-7 and A764 cells in immunodeficient mice were detected with high sensitivity. Background was observed in particular in liver within the first 24 h, but also skull and hind limbs yielded some background. Overall, fluorescent CXCL12-conjugates are sensitive and selective probes to detect solid and metastatic tumors by targeting tumor cells and tumor vasculature.     

A novel method for long term bone marrow culture and genetic modification of murine neutrophils via retroviral transduction

Neutrophils are a critical component of the innate immune response to invading microbial pathogens. However, an excessive and/or prolonged neutrophil response can result in tissue injury that is thought to underlie the pathogenesis of various inflammatory diseases. The development of novel therapeutic strategies for inflammatory diseases depends on an improved understanding of regulation of neutrophil function. However, investigations into neutrophil function have been constrained in part by the difficulty of genetically modifying neutrophils using current techniques. To overcome this, we have developed a novel method for the genetic modification of murine bone marrow derived progenitor cells using retroviral transduction followed by long term bone marrow culture to generate mature neutrophils. These neutrophils are functionally mature as determined by morphology, surface marker (Gr1, CD11b, CD62L and CXCR2) expression, and functional attributes including the ability to generate superoxide, exocytose granule contents, chemotax, and phagocytose and kill bacteria. Further, the in vitro matured neutrophils are capable of migrating to an inflammatory site in vivo. We utilized this system to express the Bcl-2 transgene in mature neutrophils using the retroviral vectors pMIG and pMIT. Bcl-2 overexpression conferred a substantial delay in spontaneous apoptosis of neutrophils as assessed by annexin V and 7-amino-actinomycin D (7AAD) staining. Moreover, Bcl-2 overexpression did not alter granulopoiesis, as assessed by morphology and surface marker expression. This system enables the genetic manipulation of progenitor cells that can be differentiated in vitro to mature neutrophils that are functional in vitro and in vivo.     

Deregulation of the CXCL12/CXCR4 axis in methotrexate chemotherapy-induced damage and recovery of the bone marrow microenvironment

Cancer chemotherapy disrupts the bone marrow (BM) microenvironment affecting steady-state proliferation, differentiation and maintenance of haematopoietic (HSC) and stromal stem and progenitor cells; yet the underlying mechanisms and recovery potential of chemotherapy-induced myelosuppression and bone loss remain unclear. While the CXCL12/CXCR4 chemotactic axis has been demonstrated to be critical in maintaining interactions between cells of the two lineages and progenitor cell homing to regions of need upon injury, whether it is involved in chemotherapy-induced BM damage and repair is not clear. Here, a rat model of chemotherapy treatment with the commonly used antimetabolite methotrexate (MTX) (five once-daily injections at 0.75 mg/kg/day) was used to investigate potential roles of CXCL12/CXCR4 axis in damage and recovery of the BM cell pool. Methotrexate treatment reduced marrow cellularity, which was accompanied by altered CXCL12 protein levels (increased in blood plasma but decreased in BM) and reduced CXCR4 mRNA expression in BM HSC cells. Accompanying the lower marrow CXCL12 protein levels (despite its increased mRNA expression in stromal cells) was increased gene and protein levels of metalloproteinase MMP-9 in bone and BM. Furthermore, recombinant MMP-9 was able to degrade CXCL12 in vitro. These findings suggest that MTX chemotherapy transiently alters BM cellularity and composition and that the reduced cellularity may be associated with increased MMP-9 expression and deregulated CXCL12/CXCR4 chemotactic signalling.     

Growth factors mobilize CXCR4 low/negative primitive hematopoietic stem/progenitor cells from the bone marrow of nonhuman primates.

Abstract The chemokine receptor CXCR4 is expressed by CD34 + hematopoietic stem/progenitor cells (HSC/HPC). Several investigators have suggested that expression of CXCR4 may be an important characteristic of HSC/HPC. We studied the dynamic expression of CXCR4 during growth factor-induced mobilization of HSC in a clinically relevant nonhuman primate model, Papio anubis (baboons). We evaluated whether CXCR4 expression in HSC/HPC varies during steady-state hematopoiesis as well as during growth factor-induced mobilization. Peripheral blood stem cells from 5 baboons were mobilized with growth factors. During mobilization, there was a consistent stepwise increase in the proportion of peripheral blood CD34 + cells that were CXCR4 -. The highest number of CD34 + CXCR4 - cells appeared in the peripheral blood at the same time as the maximum number of assayable colony-forming cells. The cloning efficiency of the CD34 + CXCR4 - population was 3-fold greater than that of CD34 + CXCR4 + cells, and the frequency of cobblestone area-forming cells was 6 times higher in the CD34 + CXCR4 - population in comparison to CD34 + CXCR4 + cells. Furthermore, the most quiescent CD34 + cells isolated on the basis of low Hoechst 33342 (Ho) and rhodamine 123 (Rho) staining (Ho Low /Rho Low ) were highly enriched in the CXCR4 Low/- cell population. Ex vivo incubation of mobilized peripheral blood CD34 + cells with growth factors for 40 hours resulted in increasing numbers of cells expressing CXCR4. Peripheral blood stem cell grafts containing CD34 + cells that consisted of predominantly CXCR4 - cells were able to rapidly engraft lethally irradiated baboons. Because the overwhelming number of CD34 + cells within the mobilized peripheral blood grafts were CXCR4 - and were capable of rescuing lethally irradiated baboons, it seems unlikely that the expression of CXCR4 in vitro is an absolute requirement for HSC homing and engraftment. In summary, our data suggest the dynamic nature of CXCR4 expression on CD34 + cells during growth factor-induced HSC/HPC mobilization. In addition, our data indicate that the lack of CXCR4 expression is possibly a characteristic of relatively more primitive HSC/HPC characterized by a higher proliferative capacity.     

Three-dimensional engineered bone from bone marrow stromal cells and their autogenous extracellular matrix

Most bone tissue-engineering research uses porous three-dimensional (3D) scaffolds for cell seeding. In this work, scaffold-less 3D bone-like tissues were engineered from rat bone marrow stromal cells (BMSCs) and their autogenous extracellular matrix (ECM). The BMSCs were cultured on a 2D substrate in medium that induced osteogenic differentiation. After reaching confluence and producing a sufficient amount of their own ECM, the cells contracted their tissue monolayer around two constraint points, forming scaffold-less cylindrical engineered bone-like constructs (EBCs). The EBCs exhibited alizarin red staining for mineralization and alkaline phosphatase activity and contained type I collagen. The EBCs developed a periosteum characterized by fibroblasts and unmineralized collagen on the periphery of the construct. Tensile tests revealed that the EBCs in culture had a tangent modulus of 7.5 +/- 0.5 MPa at 7 days post-3D construct formation and 29 +/- 9 MPa at 6 weeks after construct formation. Implantation of the EBCs into rats 7 days after construct formation resulted in further bone development and vascularization. Tissue explants collected at 4 weeks contained all three cell types found in native bone: osteoblasts, osteocytes, and osteoclasts. The resulting engineered tissues are the first 3D bone tissues developed without the use of exogenous scaffolding.     

A novel antagonist of CRTH2 blocks eosinophil release from bone marrow, chemotaxis and respiratory burst

BACKGROUND: Chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) has been revealed to be a novel receptor for prostaglandin (PG) D(2), which is a major mast cell product released during the allergic response. The aim of this study was to analyze the effects of a newly developed small molecule antagonist of CRTH2, Cay10471, on eosinophil function with respect to recruitment, respiratory burst and degranulation. METHODS: Chemotaxis of guinea pig bone marrow eosinophils and human peripheral blood eosinophils were determined using microBoyden chambers. Eosinophil release from bone marrow was investigated in the in situ perfused guinea pig hind limb preparation. Respiratory burst and degranulation were measured by flow cytometry. RESULTS: Cay10471 bound with high affinity to recombinant human and guinea pig CRTH2, but not DP, receptors. The antagonist prevented the PGD(2)-induced release of eosinophils from guinea pig bone marrow, and inhibited the chemotaxis of guinea pig bone marrow eosinophils and human peripheral blood eosinophils. Pretreatment with PGD(2) primed eosinophils for chemotaxis towards eotaxin, and this effect was prevented by Cay10471. In contrast, PGD(2) inhibited the C5a-induced up-regulation of CD63, a cellular marker of degranulation, in a Cay10471-sensitive manner. Finally, Cay10471 abolished the respiratory burst of eosinophils upon stimulation by PGD(2). CONCLUSION: These data further emphasize the importance of CRTH2 in eosinophil function and show that Cay10471 is a highly potent and selective antagonist of PGD(2)-induced eosinophil responses. Cay10471 might hence be a useful compound for the treatment of allergic diseases.     

The chemokine receptor CXCR4 is required for the retention of B lineage and granulocytic precursors within the bone marrow microenvironment

We report that the chemokine receptor CXCR4 is required for the retention of B lineage and granulocytic precursors within fetal liver and bone marrow microenvironment. In CXCR4-deficient embryos, pro-B cells are present in blood but hardly detectable in liver; myeloid cells are elevated in blood and reduced in liver compared to wild-type embryos. Mice reconstituted with CXCR4-deficient fetal liver cells have reduced donor-derived mature B lymphocytes in blood and lymphoid organs. The numbers of pro-B and pre-B cells are reduced in bone marrow and abnormally high in blood. Granulocytic cells are reduced in bone marrow but elevated and less mature in the blood. B lineage and granulocytic precursors are released into the periphery in absence of CXCR4.     

Pharmacologic regulation of mediator generation and release from the murine bone marrow derived mast cell

Mucosal mast cells constitute the subclass of IgE-FcR-bearing cells for which the murine bone marrow derived mast cell (BMMC) is an in vitro model. BMMC can be induced by an IgE-dependent mechanism to biosynthesize prostaglandin D2, several 5-lipoxygenase products, and an alkyl-ether phospholipid metabolite, as well as to degranulate. By introduction of selective enzyme inhibitors, it was determined that the bioavailability of each mediator class occurred without regulatory effects on the others. Additionally, since BMMC divide in culture, cell responsiveness for secretion of each mediator class was shown to be independent of the state of proliferation by employing three different nontoxic inhibitors of cell division.     

Observations on the discharged granules from guinea-pig bone marrow basophils following anaphylaxis

Degranulation of basophils took place in sensitized guinea-pigs when challenged with specific antigen, regardless of whether the animals had received a mepyramine maleate (anti-histamine) injection or not. The degranulation was most pronounced in the first 5 minutes following challenge. The discharged basophil granules were taken up by the neutrophils, the macrophages, and the monocytes in the bone marrow; the neutrophils, however, responded much more promptly and actively than the other phagocytes. Phagocytosis of the discharged basophil granules was most active 10–15 minutes following challenge, during which varying numbers of phagocytic vacuoles were found in the phagocytes.

Stages of changes were observed in the phagocytic vacuoles and their granule contents, which consisted of: (1) diminution or disappearance of the perigranular clear space with subsequent adhesion of the limiting membrane of the vacuole to the granule content; (2) disintegration or dissolution of the granule content and the limiting membrane of the vacuole; and (3) incorporation of the granule content into the cytoplasmic matrix of the phagocyte. In addition, a depletion of neutrophil granules in the cytoplasm surrounding the phagocytic vacuole was also observed in association with the above changes, and was suggested to be related to the digestion of the ingested granules.

The discharged basophil granules disappeared completely from the bone marrow by 1 hour after challenge. The removal of the granules was by digestion while they were in the bone marrow as well as by dispersal of the granules through the bone marrow sinusoids into the circulation.

     

Allergen-induced traffic of bone marrow eosinophils, neutrophils and lymphocytes to airways

We evaluated whether bone marrow (BM) inflammatory cells have capacity to traffic into the airways following allergen exposure in a mouse model of allergen-induced airway inflammation. We also evaluated the effect of IL-5 overexpression on (i) the production of eosinophils in BM, (ii) the accumulation of eosinophils, neutrophils and lymphocytes in blood and airways and (iii) the changes in CD34+ cell numbers in BM, blood and airways. Bromodeoxyuridine (BrdU) was used to label cells produced during the exposure period. Furthermore, CD3 splenocytes were adoptively transferred to investigate the BM inflammatory response. Allergen exposure induced traffic of BM eosinophils, neutrophils and lymphocytes to the airways and increased the number of BrdU+ eosinophils, neutrophils, lymphocytes and CD34+ cells in BALf. IL-5 overexpression enhanced the eosinophilopoiesis and increased the presence of BrdU+ eosinophils and CD34+ cells in airways and enhanced the number of CD34+ cells in BM and blood after allergen exposure. Adoptive transfer of CD3 lymphocytes overexpressing IL-5 caused increased BM eosinophilia. In conclusion, allergen exposure induces traffic of not only newly produced eosinophils but also newly produced neutrophils and lymphocytes into the airways.     

Meninges control tangential migration of hem-derived Cajal-Retzius cells via CXCL12/CXCR4 signaling

Cajal-Retzius cells are critical in the development of the cerebral cortex, but little is known about the mechanisms controlling their development. Three focal sources of Cajal-Retzius cells have been identified in mice-the cortical hem, the ventral pallium and the septum-from where they migrate tangentially to populate the cortical surface. Using a variety of tissue culture assays and in vivo manipulations, we demonstrate that the tangential migration of cortical hem-derived Cajal-Retzius cells is controlled by the meninges. We show that the meningeal membranes are a necessary and sufficient substrate for the tangential migration of Cajal-Retzius cells. We also show that the chemokine CXCL12 secreted by the meninges enhances the dispersion of Cajal-Retzius cells along the cortical surface, while retaining them within the marginal zone in a CXCR4-dependent manner. Thus, the meningeal membranes are fundamental in the development of Cajal-Retzius cells and, hence, in the normal development of the cerebral cortex.