Cytokine-mobilized peripheral blood progenitor cells for allogeneic reconstitution of miniature swine

BACKGROUND: Because of the relative ease of acquisition, increased yield, and improved engraftment characteristics, mobilized peripheral blood progenitor (stem) cells (PBSCs) have recently become the preferred source for hematopoietic stem cell transplantation. In our laboratory, procurement of a megadose of PBSCs is necessary for on-going studies evaluating non-myelosuppressive transplant regimens for the induction of mixed chimerism and allograft tolerance. To exploit hematopoietic growth factor synergy, we have sought to combine growth factors with proven utility to improve PBSC mobilization and maximize our PBSC procurement through an automated collection procedure. METHODS: Mobilization characteristics of PBSCs were determined in 2-5-month-old miniature swine. Animals received either swine recombinant stem cell factor (pSCF, 100 microg/kg) and swine recombinant interleukin 3 (pIL-3, 100 microg/kg), administered intramuscularly for 8 days, or pSCF, pIL-3, and human recombinant granulocyte-colony stimulating factor (hG-CSF), at 10 microg/kg. Leukapheresis was performed beginning on day 5 of cytokine treatment and continued daily for 3 days. RESULTS: Collection of PBSCs from cytokine-mobilized animals via an automated leukapheresis procedure demonstrated a 10-fold increase in the number of total nucleated cells (TNC) (20-30 x 10(10) TNC) compared to bone marrow harvesting (2-3 x 10(10) total TNC). A more rapid rise in white blood cells (WBCs) was seen after administration of all three cytokines compared to pSCF and pIL-3 alone. An increase in colony-forming unit granulocyte-macrophage frequency measured daily from peripheral blood during cytokine treatment, was seen with the addition of hG-CSF to pSCF/pIL-3 correlating well with the rise in WBCs. Similarly, the addition of hG-CSF demonstrated a notable increase in the median progenitor cell yield from the 3-day leukapheresis procedure. Cytokine-mobilized PBSCs were capable of hematopoietic reconstitution. PBSCs mobilized with pSCF/pIL-3 were infused into an SLA-matched recipient conditioned with cyclophosphamide (50 mg/kg) and total body irradiation 1150 cGy. Neutrophil and platelet engraftment occurred on days 5 and 7, respectively, with minimal evidence of graft-versus-host disease. Complete donor chimerism has been demonstrated 331 days after transplant. CONCLUSIONS: Our preliminary results show that in this well-defined miniature swine model, recombinant swine cytokine combinations (pSCF, pIL-3 with or without hG-CSF) successfully mobilize a high yield of progenitor cells for allogeneic transplantation. Furthermore, these cytokine-mobilized PBSCs demonstrate the potential to reconstitute hematopoiesis and provide long-term engraftment in miniature swine.     

Kinetics of peripheral blood CD34-positive cells and the optimum timing for harvesting peripheral blood stem cells during BEP chemotherapy in patients with testicular germ cell tumor

PURPOSE: Recently, high-dose chemotherapy with peripheral blood stem cell (PBSC) rescue has been developed for poor risk testicular germ cell cancer. In this study, we investigated the optimum timing for harvesting PBSCs with the use of bleomycin + etoposide + cisplatin (BEP) chemotherapy, which is a well known first-line regimen for the testicular cancer. MATERIAL AND METHOD: Peripheral blood CD34-positive cell ratios were measured during a total of 10 courses of BEP chemotherapy in 6 patients with metastatic germ cell cancer between 1996 and 1998. We performed 4 apheresis in 3 patients during this period. Recombinant human granulocyte-colony stimulating factor (rhG-CSF) was administrated from the day on which the neutrophil count decreased less than 1,000/microliter. RESULTS: The peripheral blood CD34-positive cell ratios became maximum (3.0-24.6%; average 10.0%) on the day 18 to 21 (median day 19) of BEP chemotherapy with rhG-CSF administration. The maximum ratios of peripheral blood CD34 positive cells were achieved when the number of leukocyte were 6,880-23,600/microliter and exceeded 6,000/microliter after the 18th day of BEP chemotherapy. The average number of collected CD34 positive cells was 9.5 x 10(6)/kg at a single apheresis, and 12.6 x 10(6)/kg per patient. CONCLUSION: Efficient hematopoietic progenitor cells were mobilized by BEP chemotherapy with rhG-CSF administration of first-line setting. Our results suggest that the optimum timing of PBSCs harvest is the day when the numbers of leukocyte exceed 6,000/microliter after the 18th day of BEP chemotherapy and the following day.     

Higher dose of CD34+ peripheral blood stem cells is associated with better survival after haploidentical stem cell transplantation in pediatric patients

Haploidentical stem cell transplantation (SCT) is increasingly used to treat pediatric patients with malignant or nonmalignant hematological disorders. The CD34+ dose of bone marrow or peripheral blood stem cells (PBSCs) has been shown to be an important determinant of the transplant outcome in adults under various preparative regimens. However, knowledge of the effect of the CD34+ dose in pediatric haploidentical SCT is limited. We analyzed the data of 348 pediatric patients (aged 2‐18 years) with acute or chronic leukemia, myelodysplastic syndrome (MDS), and other hematological disorders that received a transplant between 2002 and 2012. The results of multivariate analysis showed that PBSC CD34+ counts greater than 1.01 × 10⁶ kg^?1 improved platelet engraftment, improved overall survival, and reduced nonrelapse mortality. In contrast, a higher PBSC CD34+ dose did not affect the incidence of acute or chronic graft‐versus‐host disease, including engraftment syndrome. These data suggest that a PBSC CD34+ dose greater than 1.01 × 10⁶ kg^?1 is optimal for pediatric haploidentical SCT.     

Collection of peripheral blood stem cells with granulocyte-colony-stimulating factor alone in testicular cancer patients.

BACKGROUND: High-dose chemotherapy with the transplantation of peripheral blood stem cells (PBSC) has been performed for the treatment of advanced testicular cancer patients. Recently, it has been reported that, in healthy donors, a large quantity of stem cells can be transferred to peripheral blood using granulocyte-colony-stimulating factor (G-CSF) alone. Therefore, it was decided to try to harvest PBSC from three patients having testicular cancers with G-CSF alone. METHODS: The three patients with testicular cancer were 26, 56 and 62-years-old. They had undergone five, two and three cycles of chemotherapy, respectively, but no radiation therapy. Granulocyte colony-stimulating factor was subcutaneously injected (250 microg) into each patient twice per day for 6 days. Peripheral blood stem cells were harvested for 3 days (days 4-6) and mononuclear cells (MNC), CD34-positive cells and colony-forming units of granulocyte-macrophage (CFU-GM) in PBSC collected by apheresis were measured. RESULTS: Apheresis showed that the total MNC count was 20.2 x 10(8)/kg (range, 10.6-25.9 x 10(8)/kg), the CD34-positive cell count was 0.98 x 10(6)/kg (range, 0.75-1.4 x 10(6)/kg) and the total CFU-GM count was 1.36 x 10(5)/kg (range, 0.25-3.0 x 10(5)/kg). CONCLUSION: After mobilization of peripheral blood stem cells with G-CSF alone, sufficient amounts of MNC were obtained from testicular cancer patients who had undergone chemotherapy several times. However, sufficient amounts of CD34-positive cells and CFU-GM could not be obtained. These results suggested that the G-CSF dose was not adequate for harvesting sufficient amounts of CD34-positive cells and CFU-GM.     

CD34+细胞在干细胞旁分泌下向内皮细胞分化的研究

目的 探讨人脐血CD34+细胞在脐带间充质干细胞(UC-MSCs)旁分泌作用下向内皮细胞诱导分化的可行性.方法 收集20份脐血,体积(103.80±19.77)ml.免疫磁珠(MACS)分选CD34+细胞;取脐带用消化贴壁法获得UC-MSC.流式鉴定干细胞表型.实验分单纯培养组、诱导组、共培养组.结果 流式鉴定CD34+细胞纯度(95.02±3.81)%.培养14 d流式检测共培养组表达CD31、CD144、VWF分别为(65.43±5.61)%、(54.40±4.13)%、(47.53±3.96)%(与单纯培养组比较P＜0.05),部分表达CD34,阴性表达CD45,这与诱导组及成熟脐静脉内皮细胞表达率一致.结论 UC-MSCs旁分泌作用与外源性细胞因子都具有促分化作用,均能使脐血CD34+细胞向内皮细胞分化.

Abstract：

Objective To study whether the paracrine action of umbilical cord-derived mesenchymal stem cells (UC-MSC) can induce differentiation of human umbilical cord blood-derived CD34+ cells into endothelial cells in vitro. Methods The 20 fresh umbilical cord blood samples were collected with volume of (103. 80 ± 19. 77) ml. CD34+ cells were isolated from the mononuclear cells by magnetic activated cell sorting system (MACS) , and mesenchymal stem cells (MSCs) were isolated from umbilical cord by collagenase and trypsin digestion. Three groups were set up: CD34+ cells pure culture group, cytokineinduced group and two stem cells co-culture group with noncontact. Results The average purity of enriched CD34+ cells as assessed by FACS was (95. 02 ± 3. 81) %. Freshly isolated CD34+ cells were small and round which suspended in culture medium. Attached cord-like structure cells of CD34+ cells appeared after 7 days coculture with noncontacted MSC, and when the CD34+ cells grew into large number, they formed colonies. These cells expressed endothelial specific markers, including CD144 (54. 40 ±4. 13)% ,vWF (47. 53 ± 3. 96) % , CD31 (65. 43 ± 5. 61) % ( P ＜ 0. 05, as compared with CD34+ cells pure culture group) , partially expressed CD34 and, the leukocyte common antigen CD45 was negatively expressed.Conclusion Human umbilical cord blood-derived CD34+ cells could be induced into endothelial cells under the paracrine action of umbilical cord-derive mesenchymal stem cells which has the same effect of cytokines.     

由脐血单个核细胞和富集的CD34+细胞扩增的造血干/祖细胞的生理功能比较

目的 探讨由脐血单个核细胞(MNC)和富集的CD34+细胞起始扩增所得的造血干/祖细胞在体内植入及造血重建的能力.方法 从人脐血中分离出MNC和CD34+细胞,在体外扩增7 d.将非肥胖糖尿病型重症联合免疫缺陷型(NOD/SCID)小鼠分为四组,在接受亚致死剂量铯源照射后,进行细胞移植,实验A组接受由MNC培养得到的CD34+细胞和CD34-细胞;实验B组接受由富集的CD34+细胞培养得到的CD34+细胞和CD34-细胞;阳性对照组接受从脐血新鲜分离的CD34+细胞和CD34-细胞;阴性对照组不接受细胞移植,仅输注相同体积的IMDM培养基.6周后处死存活的小鼠,取其骨髓、脾脏和外周血细胞,分别进行细胞表型分析、集落和人特异性基因的检测.结果 经过体外扩增,以富集的CD34+细胞起始培养者的细胞总扩增倍数为39.8倍,远高于以MNC为起始细胞者的1.88倍.移植6周后,所有接受细胞移植的小鼠均存活,存活小鼠的骨髓和脾脏细胞中均能检测到人源细胞(CD45+细胞)及人源的各系血细胞,实验A组各类细胞的含量稍高于实验B组,且接受细胞移植小鼠的骨髓和脾脏细胞中可检测出人特异的Alu序列.结论 与从脐血中新鲜分离的细胞相比,扩增后的造血干/祖细胞的体内植入能力有所下降,以MNC起始扩增的造血干/祖细胞体内植入能力优于以富集的CD34+细胞起始扩增者,但二者体内造血重建能力的差异不显著.     

Conditions that enable human hematopoietic stem cell engraftment in all NOD-SCID mice

BACKGROUND: Transplantation of human hematopoietic stem cells is the only true test of their long-term repopulation potential. Models are readily available to evaluate murine hematopoietic stem cells, but few exist that allow reliable quantification of human stem cells. The non-obese diabetic-severe combined immunodeficient (NOD-SCID) mouse model enables quantification of human hematopoietic stem cells, but the conditions that permit human engraftment in all animals have yet to be defined. The aims of the project were, therefore, to describe the variables that allow human engraftment in the NOD-SCID mouse model and the techniques that accurately quantify this engraftment. METHODS: NOD-SCID mice that had or had not received 250, 325, or 400 cGy irradiation received cord blood (CB) mononuclear or CD34+ cells i.v. or i.p. Mice were killed 6 weeks after transplantation, and the bone marrow, spleen, and thymus were harvested. Four-color flow cytometric analysis, semi-quantitative PCR, myeloid and erythroid progenitor, and stem cell assays were used to monitor human engraftment. RESULTS: A 250 or 325 cGy and i.v. injection of CB mononuclear or CD34+ cells is required to detect multilineage human engraftment in the bone marrow, spleen, or thymus of NOD-SCID mice. Four-color flow cytometric analysis and semi-quantitative PCR enable accurate detection of 0.1% human cells. Progenitor and stem cell assays provide functional information about the engrafted cells. CONCLUSIONS: Successful development of the NOD-SCID mouse model and techniques to assess human engraftment now allow it to be used reliably to analyze the effects of short-term cytokine exposure on the long-term repopulating capacity of CB stem cells.     

Successful multilineage engraftment of human cord blood cells in pigs after in utero transplantation

BACKGROUND: Successful engraftment of human hematopoietic stem and progenitor cells (HSPCs) in a large animal may serve not only as a model to study human hematopoiesis but also as a bioreactor to expand human HSPCs in vivo. The aim of this study was to accomplish xenotransplantation of human HSPCs into pig. METHODS: Total mononuclear or CD34-positive HSPCs obtained from human cord blood were xenotransplanted percutaneously under an ultrasonographic guidance into preimmune pig fetuses. Peripheral blood and bone marrow (BM) cells of recipient pigs were collected and analyzed for the presence of human cells by a polymerase chain reaction to detect human specific Alu sequence on DNA extracted from those cells. Fluorescence-activated cell sorting (FACS) analysis was also performed to detect human hematopoietic cells. RESULTS: Transplantation of human cord blood cells into pig fetuses aged less than 52 days postcoitus resulted in a good engraftment rate. In one case, engraftment was detected up to 315 days posttransplantation by polymerase chain reaction. Human hematopoietic cells were detectable also by FACS in peripheral blood and BM. Furthermore, human CD34+ HSPCs were also observed in the BM of recipients. Those CD34+ cells in BM were sorted by FACS and subjected to further analyses. First, in vitro colony formation assay resulted in formations of multilineage colonies. Second, when they were transplanted into an immunodeficient mouse they were engrafted in the mouse. CONCLUSIONS: These data indicate an engraftment of human HSPCs in pig BM. In utero transplantation of human HSPCs into a preimmune pig fetus is useful to establish a pig reproducing human hematopoiesis.     

动员自体骨髓干细胞对大鼠急性肾小管坏死的治疗

目的：观察粒细胞集落刺激因子联合干细胞因子动员骨髓干细胞的作用、骨髓干细胞是否具有向损伤肾组织归巢的能力及其在肾脏组织中的分布,初步探讨粒细胞集落刺激因子联合干细胞因子是否具有促进急性肾小管坏死修复的作用。方法：160只8～10周龄雄性SD大鼠随机分为4组：对照组,模型组、G-CSF＋SCF治疗组、G-CSF＋SCF对照组,检测：（1）外周血白细胞总数及单个核细胞中CD34＋细胞百分比的变化;（2）尿NAG酶检测;（3）肾脏组织病理学改变;（4）肾组织CD34＋细胞表达变化。结果：（1）G-CSF＋SCF治疗组和G-CSF＋SCF对照组外周血中白细胞数、CD34＋细胞百分比于第5天达高峰,与对照组、模型组相比,差异有统计学意义（P〈0.05）,以后逐渐下降;相应地,G-CSF＋SCF治疗组肾组织内CD34＋细胞较对照组、模型组也明显增多（P〈0.05）。（2）手术后第5、10、17天,G-CSF＋SCF治疗组尿NAG酶、肾脏病理学改变均明显好于模型组（P〈0.05）。第24天G-CSF＋SCF治疗组尿NAG酶、肾脏病理学改变基本恢复正常,而模型组仍异常。第31天各组间尿NAG酶、肾脏病理学改变其差异无统计学意义。结论：（1）粒细胞集落刺激因子和干细胞因子联合应用对缺血再灌注损伤诱发急性肾小管坏死大鼠的骨髓干细胞有显著的动员作用。（2）骨髓干细胞能在损伤的肾小管归巢和定居,并可能参与损伤肾组织的修复。（3）粒细胞集落刺激因子和干细胞因子联合应用能在一定程度上加速急性肾小管坏死后肾功能的修复。     

CD34+ selected bone marrow grafts are radioprotective and establish mixed chimerism in dogs given high dose total body irradiation.

BACKGROUND: Canine stem cell transplantation models have provided important preclinical information for human clinical studies. The recent cloning of cDNA for canine CD34 and the production of monoclonal antibodies that recognize canine CD34 have been the basis for the development of techniques for the large-scale enrichment of canine hematopoietic progenitor cells. In this study, we evaluated the in vivo functional properties of canine bone marrow CD34+ cells after a myeloablative conditioning regimen. METHODS: After 920 cGy total body irradiation, three dogs received infusion of autologous CD34+ selected cells from the marrow, three dogs CD34+ depleted autologous marrow cells, and two dogs received CD34+ autologous marrow cells that were immunomagnetically selected and then further purified by cell sorting. In addition, four dogs received allogeneic marrow enriched for CD34+ cells from dog leukocyte antigen-identical littermates to investigate long-term repopulating function of CD34+ cells. Chimerism studies were performed using polymerase chain reaction to detect highly polymorphic microsatellite markers. RESULTS: In three recipients of autologous marrow enriched for CD34+ cells to between 29% and 70% (1.6 x 10(6) to 3.4x10(6) CD34+ cells/kg), prompt and full hematopoietic recovery occurred, whereas in three dogs that received marrow depleted of CD34+ cells (1 x 10(7) cells/kg), no hematopoietic recovery was achieved. In two dogs that received highly purified CD34+ cells (purity: 98% and 96%, 0.79x10(6) to 0.547x 10(6) CD34+ cells/kg), delayed but full hematopoietic recovery was seen. Three of four allograft recipients of 1.75x10(6) to 6.8x10(6) CD34+ cells/kg engrafted and showed full hematopoietic recovery, whereas one dog rejected the graft. The three long-term survivors showed stable mixed hematopoietic chimerism with predominantly donor hematopoiesis. CONCLUSION: Transplantation of canine CD34+ cells after lethal total body irradiation provides radioprotection and gives rise to long-term hematopoietic reconstitution. Stable donor/host mixed chimerism was observed in allograft recipients most likely as a result of T-cell depletion of the grafts. Our findings suggest a future role for canine preclinical transplant studies involving in vitro manipulation of hematopoietic pro.     

Expression of stem cell markers on mononuclear cells derived from heparinized cadaveric organ donors before and after disconnection from the respirator

We have attempted to evaluate the level of the earliest human hematopoietic cell marker expression (CD34, CD117, CD133, CD184) on cells obtained from heparinized cadaveric organ donors before and after disconnection from the respirator. Moreover, we compared various cell populations: (1) coexpressing CD34/CD117; (2) CD34/CD133; (3) highly enriched hematopoietic stem cells (CD34+CXCR4+CD45+); and (4) highly enriched tissue-committed stem cells (CD34+CXCR4+CD45-). Finally, we analyzed whether the level of hematopoietic stem cell marker expression depended on the age of the donor. The expression of the membrane receptors (CD34, CD45, CD117, CD133, CD184) was studied by flow cytometry. We observed that the proportion of mononuclear cells expressing these markers slightly decreased in bone marrow harvested after disconnection from the respirator compared with the samples obtained before disconnection. Moreover, the proportion of cells expressing CD117 antigen depended on age of the donor.     

T-cell reconstitution after unmanipulated, CD8-depleted or CD34-selected nonmyeloablative peripheral blood stem-cell transplantation

BACKGROUND: We have previously shown that CD8 depletion or CD34 selection of peripheral blood stem cells (PBSC) reduced the incidence of acute graft-versus-host disease (GvHD) after nonmyeloablative stem-cell transplantation (NMSCT). In this study, we analyze the effect of CD8 depletion or CD34 selection of the graft on early T-cell reconstitution. METHODS: Nonmyeloablative conditioning regimen consisted in 2 Gy total-body irradiation (TBI) alone, 2 Gy TBI and fludarabine, or cyclophosphamide and fludarabine. Patients 1 to 18 received unmanipulated PBSC, patients 19 to 29 CD8-depleted PBSC, and patients 30 to 35 CD34-selected PBSC. RESULTS: T-cell counts, and particularly CD4+ and CD4CD45RA+ counts, remained low the first 6 months after nonmyeloablative stem-cell transplantation (NMSCT) in all patients. CD34 selection (P<0.0001) but not CD8 depletion of PBSC significantly decreased T-cell chimerism. Donor T-cell count was similar in unmanipulated compared with CD8-depleted PBSC recipients but was significantly lower in CD34-selected PBSC recipients (P=0.0012). T cells of recipient origin remained stable over time in unmanipulated and CD8-depleted PBSC patients but expanded in some CD34-selected PBSC recipients between day 28 and 100 after transplant. Moreover, whereas CD8 depletion only decreased CD8+ counts (P<0.047), CD34 selection reduced CD3+(P<0.001), CD8+(P<0.016), CD4+ (P<0.001), and CD4+CD45RA+ (P<0.001) cell counts. T-cell repertoire was restricted in all patients on day 100 after hematopoietic stem-cell transplantation but was even more limited after CD34 selection (P=0.002). CONCLUSIONS: Despite of the persistence of a significant number of T cells of recipient origin, T-cell counts were low the first 6 months after NMSCT. Moreover, contrary with CD8 depletion of the graft that only affects CD8+ lymphocyte counts, CD34 selection dramatically decreased both CD8 and CD4 counts.     

The effect of human fetal liver-derived mesenchymal stem cells on CD34+ hematopoietic stem cell repopulation in NOD/Shi-scid/IL-2Rã(null) mice

Mesenchymal stem cells (MSCs) are progenitors that are capable of differentiating into mesenchymal tissues. They are known to support allogeneic hematopoietic stem cell transplantation by facilitating engraftment without increasing the risk of graft-versus-host disease. We optimized culture conditions for human fetal liver-derived MSCs (hFL-MSCs) to investigate the role of hFL-MSCs on repopulation of hematopoietic stem cells in NOD/Shi-scid/IL-2Rγ(null) (NOG) mice using CD34(+) hematopoietic stem cells (HSCs) derived from umbilical cord blood (UCB). FL-MSCs and CD34(+) HSCs were prepared from fetal liver and UCB, respectively. Twenty-four hours after irradiation, CD34(+) HSCs and hFL-MSCs were injected intravenously and intratibially into NOG mice. During 24 weeks posttransplantation, engraftment levels of human cells were analyzed in bone marrow, peripheral blood, and spleen of transplanted mice by flow cytometry. hFL-MSCs showed a fibroblast-like morphology and immunophenotypic characteristics appropriate for MSCs. hFL-MSCs prolonged the survival of NOG mice that had been cotransplanted with UCB CD34(+) cells. Fluorescence-activated cell-sorting analysis showed that engraftment of human cells was increased by cotransplantation of hFL-MSCs. However, significant enhancement of human cell engraftment was not detected in NOG mice regardless of the number of cotransplanted MSCs. Although survival of repopulating NOG mice and engraftment of human cells were prolonged by cotransplantation of hFL-MSCs, 8.0 × 10(6) MSCs were not sufficient to increase HSC engraftment in irradiated NOG mice in vivo.     

Stable engraftment after megadose blood stem cell transplantation across the HLA barrier: the case for natural killer cells as graft-facilitating cells.

BACKGROUND: The case of a patient with chronic myelogenous leukemia who underwent transplantation with highly purified CD34+ peripheral blood stem cells from his two-antigen-mismatched mother is reported. No graft-versus-host disease has been observed so far and stable engraftment has been documented until day 100. METHODS: Weekly analysis of chimerism in different cellular subsets was performed using a quantitative polymerase chain reaction assay for nine short tandem repeat markers in leukocytes sorted by fluorescence-activated cell sorting. RESULTS: No donor CD4+ or CD8+ T cells have been detected up to 3 months after transplantation, whereas a rapid increase of donor CD56+ natural killer (NK) cells was observed in parallel with circulating donor CD34+ progenitors and myeloid cells. CONCLUSIONS: Because the graft contained virtually no T and NK cells, we believe the rapid in vivo generation of NK cells supported stable engraftment across the HLA barrier. The differentiation of CD34+ progenitors into NK cells might be a distinct feature of megadose stem cell transplants.     

Increased engraftment and GVHD after in utero transplantation of MHC-mismatched bone marrow cells and CD80low, CD86(-) dendritic cells in a fetal mouse model.

BACKGROUND: Bone marrow transplantation (BMT) is the only known cure for a variety of inherited diseases and requires the administration of high doses of immunosuppressive and myeloablative therapy. Because the fetus is immunoincompetent early in gestation, in utero stem cell transplantation (IUT) could avoid the need for this toxic conditioning. A major limitation to date of IUT is the low level of engraftment and failure to induce tolerance. Dendritic cells (DC) are considered very potent antigen-presenting cells, but DC progenitors (pDC) are strongly tolerogenic. METHODS: We examined the effect of donor pDC on the degree of engraftment and tolerance induction after IUT. Bone marrow-derived pDC (CD80low, CD86-) from male C57BL/6 mice (H2b) were injected with and without donor bone marrow (BM) intraperitoneally into 13 to 15-day BALB/c (H2d) fetuses. Engraftment was determined by flow cytometry and quantitative polymerase chain reaction and tolerance by skin grafts and the mixed lymphocyte reaction. RESULTS: At 1-month posttransplant, mice that received BM+pDC showed a higher degree of engraftment (29+/-46%) than mice that received pDC-enriched cells or BM cells alone (0.11+/-0.70% and 1.71+/-1.66%, respectively, P<0.001). However, 5/19 recipients of BM+pDC died within 6 weeks; 4/5 had significant donor cell engraftment in blood and/or tissues. Also, these mice had evidence of graft-versus-host disease (GVHD). Two mice out of 15 long-term survivors in the BM+pDC group had virtually complete replacement of host with donor hematopoietic cells. Skin grafts and mixed lymphocyte reaction studies showed no durable tolerance induction other than in the two fully engrafted recipients of BM+pDC. CONCLUSIONS: These results suggest that donor pDC, along with donor BM, can have a significant impact on engraftment of MHC-mismatched donor cells associated with an increased incidence of GVHD. However, marrow-derived pDC do not result in an increase in tolerance induction in utero even when microchimerism is present.     

Ex vivo expansion of canine dendritic cells from CD34+ bone marrow progenitor cells

BACKGROUND: The aims of this study were to ex vivo expand canine dendritic cells and determine their phenotype and functional characteristics. METHODS: CD34+-selected cells and CD34+-depleted canine bone marrow (BM) cells were cultured in Iscove's modified medium for 14 days. Cytokines added to the cultures included human granylocyte/macrophage colony-stimulating factor 5 ng/ml, hFlt3 ligand 200 ng/ml, and human tumor necrosis factor-alpha 10 ng/ml. Cultured cells and purified subpopulations were assessed for cell surface antigen expression, morphology, and function by flow cytometric analysis, electron microscopy, and an allogeneic mixed lymphocyte reaction at day 14. RESULTS: Two main cell populations were identified, DR++(bright)/CD14- and DR+(dim)/CD14+. Ex vivo expanded CD34+-selected cells showed increased allostimulatory activity compared to both cultured CD34+-depleted cells and mononuclear cells. In contrast, ex vivo expansion from CD34+-depleted cells was unsuccessful. After sorting cells from the ex vivo expanded CD34+-selected bone marrow to enrich for DR++/CD14- cells, a 42-fold increase (median) of allostimulatory activity was observed as compared with sorted DR+/CD14+ cells (P=0.02). CONCLUSIONS: Cells with dentric cell-like phenotypes and functions can be cultured from canine CD34+-selected bone marrow cells. Future studies will address the roles of these cells in engraftment, graft versus host reactions and graft-host tolerance in a canine hematogoietic stem cell transplantaton model.     

Rapid isolation of human CD34 hematopoietic stem cells--purging of human tumor cells.

Human CD34+ hematopoietic stem cells were purified using a new technology in which monoclonal antibodies are covalently immobilized on polystyrene surfaces. The CD34+ cell isolation scheme involved three sequential processes: (1) purification of bone marrow mononuclear cells; (2) enrichment of CD34+ cells using covalently immobilized soybean agglutinin; and (3) positive selection of CD34+ cells using polystyrene surfaces coated with the anti-CD34 monoclonal antibody ICH3. CD34+ cells purified by this process have both low-to-medium forward light scatter and low 90 degrees light-scatter properties. Moreover, the purified CD34+ cells are greater than 85% viable, express appropriate characteristic surface antigens, and are 10-50-fold enriched in short- and long-term hematopoietic activity. CD34+ cells collected in this manner from bone marrow samples contaminated with radiolabeled breast carcinoma, neuroblastoma, acute myelogenous leukemia, or small cell lung carcinoma cells were 99.9% depleted of the tumor cells. The CD34+ cell selection devices are sterile and are easily scaled-up to process clinical scale bone marrow samples.     

Postnatal booster injections increase engraftment after in utero stem cell transplantation

BACKGROUND: The primary barrier to clinical application of in utero hematopoietic stem cell (HSC) transplantation is limited donor cell engraftment. We hypothesized that limited engraftment was due to competition between host and donor cells for available niches. We reasoned that increased engraftment might be achieved by performing multiple transplants separated by brief intervals to allow time for formation of new niches. To test this we performed multiple transplants in a congenic combination to avoid confounding immunologic effects. MATERIALS AND METHODS: C57Pep3B (H2Kb, CD45.1) mice were used as donors of adult bone marrow and C57Bl/6 (H2Kb, CD45.2) mice were used as 14-day-gestation fetal recipients. All fetuses were injected intraperitoneally with 1 x 10(6) mononuclear cells. Boosted neonates were injected at Days 2, 4, and 7 of life with 5 x 10(6) cells. All animals were analyzed for donor cell engraftment by dual-color flow cytometry using CD45 and CD45.1 antigens. Results are reported as the mean +/- SD. Statistical analysis was performed using the two-tailed Student t test with P < 0.05 considered significant. RESULTS: Postnatally boosted animals demonstrated significantly elevated levels of donor cell engraftment (3.30 +/- 0.8%; n = 8; P < 0.00001) when compared to the control animals (0.69 +/- 0.5%; n = 9) as determined by peripheral blood analysis at 6 weeks of age. This elevated level of engraftment was stable long term. CONCLUSIONS: Our results demonstrate a significant increase in donor cell engraftment with postnatal booster injections after in utero transplantation. This supports the hypothesis that a limited number of niches may be a major component of the barrier to engraftment. It also suggests that postnatal booster injections may be a viable therapeutic strategy for improving donor cell engraftment after in utero HSC transplantation.     

FLT3 ligand promotes engraftment of allogeneic hematopoietic stem cells without significant graft-versus-host disease

BACKGROUND: Graft-versus-host (GVH) reactions contribute to stable engraftment of allogeneic hematopoietic stem cell transplants. It was hypothesized that the in vivo expansion of recipient dendritic cells (DC) with the administration of ligand for Flt3 (FL) could promote allogeneic engraftment after reduced-intensity conditioning by enhancing the GVH effect. METHODS: FL was first administered to three nonirradiated healthy dogs for 13 days at a dosage of 100 microg/kg/day. Next, nine dogs received 4.5 Gy total-body irradiation (TBI) and unmodified marrow grafts from dog leukocyte antigen (DLA)-identical littermates without posttransplant immunosuppression. FL was administered to the recipients at a dosage of 100 microg/kg/day from day -7 until day +5. RESULTS: In normal dogs, FL produced significant increases in monocytes (CD14+) and neutrophils in the peripheral blood, a marked increase in CD1c+ cells with DC-type morphology in lymph nodes, and increased alloreactivity of third-party responders to peripheral blood mononuclear cells in mixed lymphocyte reactions (P<0.001). Sustained engraftment was observed in eight of nine (89%) FL-treated dogs compared with 14 of 37 (38%) controls (P=0.02, logistic regression). All engrafted FL-treated dogs became stable complete (n=2) or mixed (n=6) hematopoietic chimeras without significant graft-versus-host disease (GVHD). Recipient chimeric dogs (n=4) were tolerant to skin transplants from their marrow donors but rejected skin grafts from unrelated dogs within 7 to 9 days (median, 8 days). CONCLUSIONS: In this study, the authors showed that FL administered to recipients promotes stable engraftment of allogeneic marrow from DLA-identical littermates after 4.5 Gy TBI without significant GVHD.