Functional tissue-engineered blood vessels from bone marrow progenitor cells

OBJECTIVE: Stem cells have significant potential for development of cell-based therapeutics for cardiovascular tissue regeneration. METHODS: We developed a novel method for isolating smooth muscle cells (SMC) from ovine bone marrow using a tissue-specific promoter and fluorescence-activated cell sorting. RESULTS: As compared to vascular SMC, bone marrow-derived smooth muscle progenitor cells (BM-SMPC) exhibited similar morphology, showed higher proliferation potential and expressed several SMC markers including alpha-actin, calponin, myosin heavy chain, smoothelin, caldesmon and SM22. When embedded in fibrin hydrogels, BM-SMPC contracted the matrix and displayed receptor- and non-receptor-mediated contractility, indicating that BM-SMPC can generate force in response to vasoreactive agonists. We also prepared tissue-engineered blood vessels from BM-SMPC and BM-derived endothelial cells and implanted them into the jugular veins of lambs. As early as five weeks post-implantation, grafted tissues displayed a confluent endothelial layer overlaying the medial layer in which BM-SMPC were aligned circumferentially and synthesized significant amounts of collagen. In contrast to previous results with vascular SMC, BM-SMPC synthesized high amounts of elastin that was organized in a fibrillar network very similar to that of native vessels. CONCLUSIONS: Our results suggest that BM-SMPC may be useful in studying SMC differentiation and have high potential for development of cell therapies for the treatment of cardiovascular disease.     

Human bone marrow progenitor cells stimulated by cord blood

Agar cultures of human bone marrow cells stimulated by cord plasma or irradiated cord blood feeder layers demonstrated the presence of a multilineage hemopoietic growth factor in cord blood. When bone marrow cultures stimulated with giant cell tumor-conditioned medium (GCT-CM) were supplemented with this cord blood-derived growth factor, total colony numbers increased by more than 50% after day 23 and persisted in culture for approximately 40 days. Marrow cultures stimulated by the cord blood-derived growth factor formed colonies of neutrophils, monocyte-macrophages, eosinophils, mast cells, and a few colonies containing a mixed cell population. The results suggest that, while GCT-CM contains granulocyte-monocyte colony-stimulating factor (GM-CSF), cord blood contains a high concentration of a multilineage hemopoietic growth factor, which may be multi-CSF.     

Cord blood transplantation provides better reconstitution of hematopoietic reservoir compared with bone marrow transplantation

Delayed hematopoietic recovery is the main factor precluding a wider use of cord blood (CB) transplants. We hypothesized that this delayed engraftment might not be related to an insufficient number of stem cells in the graft, but to an intrinsic difficulty of these cells to undergo differentiation. To test our hypothesis, 2 groups of children were compared; 12 received a CB transplant and 12 an adult bone marrow (BM) transplant. We studied neutrophil and platelet recovery and, at a median time of approximately 1 year after transplantation, the frequency of colony-forming cells (CFCs) and long-term culture initiating cells (LTC-ICs) in the BM of the 2 groups. Recipients of BM transplants received 1-log more cells and had significantly faster neutrophil and platelet recovery. Conversely, the frequency of committed and early progenitors was significantly higher in the BM of children given CB cells compared with BM transplant recipients (median count of CFC/2 x 10(4) BM mononuclear cells, 20 versus 11, P =.007; median count of LTC-IC/10(6) BM mononuclear cells, 8.2 versus 0.2 P =.001). CB, but not adult BM stem cells, can better restore the host hematopoietic progenitor cell reservoir; the delayed engraftment after CB transplantation may reflect the difficulty of CB progenitors to reprogram themselves toward differentiation.     

A novel strategy for generating platelet-like fragments from megakaryocytic cell lines and human progenitor cells

Transfusion of allogeneic platelets is the mainstay of therapy for patients with thrombocytopenic hemorrhage. However, donated platelets can only be stored for 5 days and are maintained at room temperature, increasing the risk of bacterial growth. Developing a method to produce functional platelets in vitro would greatly advance transfusion therapy. During our studies to understand megakaryocyte development, we discovered that a Src kinase inhibitor, SU6656, induces cellular enlargement, polyploidization, and cytoplasmic fragmentation of several hematopoietic cell lines. Therefore, we tested the hypothesis that these fragments possess platelet-like activity. We studied a megakaryocytic cell-line, UT-7/TPO, and immature human primary megakaryocytes. After 6 days in the presence of thrombopoietin and SU6656, the majority of cells became polyploid and started shedding platelet-like fragments. These fragments were tested for aggregation and analyzed by electron microscopy. The platelet-like fragments did not undergo spontaneous activation but did show rapid and sustained aggregation in response to each of the standard agonists collagen, arachidonic acid, adenosine diphosphate, and epinephrine. Platelet-like fragments generated in SU6656 had higher amplitude and more prolonged aggregation in each of three experiments. Primary progenitors developed demarcation membranes within 72 h and evidence of dense granules and platelet-like fragments after 6 days. These cell fragments demonstrated properties consistent with platelet aggregation in response to multiple agonists without spontaneous aggregation. These studies provide evidence that SU6656 promotes megakaryocytic differentiation and thrombopoiesis in vitro.     

Plastic-adherent progenitor cells in human bone marrow

Human bone marrow contains plastic-adherent hemopoietic progenitor cells whose plating efficiency is increased by brief (2 h) exposure to methylprednisolone (MP). When subsequently covered with methylcellulose medium, they form colonies of monoblastoid cells. Colony size, but not number, and mature cell production are increased by erythropoietin (epo) and granulocyte-macrophage colony-stimulating factor (GM-CSF). However, colonies do not grow under serum-free conditions. The resistance of plastic-adherent progenitors to treatment with 5-fluorouracil (5FU), their growth pattern, and their capacity to produce granulocytic and erythroid colonies on replating, suggest that they may be similar to the primitive, 5FU-resistant, plastic-adherent progenitor cells (HPP-CFC) in murine marrow.     

Peripheral stem cells in bone marrow transplantation. Cord blood stem cell transplantation.

Since it was shown that the number of haematopoietic stem cells contained in one sample of cord blood was sufficient for engrafting children and adults, cord blood banking has developed world wide. Cord blood banking has several advantages, including availability of this source of stem cells, low viral infection rate at birth, speed of the search and the possibility of collecting cord blood in ethnic groups under-represented in bone marrow donor registries. Other possible advantages which require further study, include a low risk of acute graft-versus-host disease, even with some degree of HLA mismatch. More than 700 cord blood transplants have been reported worldwide. The Eurocord Registry has analysed 250 cases. Briefly, analysis of the clinical results has shown that related cord blood transplants give better results than unrelated cord blood transplants. Factors associated with better survival in related and unrelated transplants were younger age, diagnosis with better results in inborn errors and children with acute leukaemia in first or second remission. High number of nucleated cells in the transplant and recipient negative cytomegalovirus serology were also favourable risk factors for survival.     

Selective secretion of chemoattractants for haemopoietic progenitor cells by bone marrow endothelial cells: a possible role in homing of haemopoietic progenitor cells to bone marrow

To elucidate the mechanisms by which haemopoietic progenitor cells lodge in the bone marrow, we examined the secretion of chemoattractants for haemopoietic progenitor cells by bone marrow and lung endothelial cells. The bone marrow endothelial cells, but not lung endothelial cells, secreted chemoattractants for the haemopoietic progenitor cell line, FDCP-2, and normal haemopoietic progenitor cells. Checkerboard analysis demonstrated that the conditioned medium of the bone marrow endothelial cells had chemotactic activity and random motility-stimulating activity. The bone marrow endothelial cells expressed stromal-cell-derived factor-1 (SDF-1) mRNA and produced SDF-1 protein, whereas the lung endothelial cells did not. Adhesion of FDCP-2 cells to the bone marrow endothelial cells was partially inhibited by anti-SDF-1 antibody. These findings suggest that the chemoattractants for haemopoietic progenitor cells including SDF-1 and random motility-stimulating factor(s) selectively secreted by the bone marrow endothelial cells may contribute to the homing of haemopoietic progenitor cells to bone marrow.     

Chemotherapy and donor peripheral blood progenitor cells for acute leukemia in early relapse after allogeneic bone marrow transplantation

Ten patients with acute leukemia (AL) in early relapse after allo-BMT were treated with a modified MEC (mitoxantrone, etoposide and Ara-C) regimen followed by donor PBPC collected after mobilization with G-CSF. Seven patients achieved CR or had normal hemopoietic reconstitution: two had an early relapse at days +53 and +48, two patients died from acute GVHD at days +31 and +96, one died of interstitial pneumonia at day +55, and two patients experienced long-term survival. One patient with refractory disease and nodal involvement who did not respond to the first BMT had overt expansion of the leukemia at day +36; one patient with Ph+ ALL and one with ANLL evolving from MDS, both with skin involvement, had blast cells in peripheral blood at day +27 and +26, respectively. Transient cytopenia occurred in all patients; a normal granulocyte and platelet count was achieved within 3 weeks in all patients but one; acute GVHD occurred in six patients, and four had chronic GVHD. This approach is feasible in patients in early relapse after allo-BMT. It assists prompt re-establishment of normal donor hematopoiesis avoiding the prolonged cytopenia observed after donor lymphocyte infusion in AL patients relapsed after allo-BMT.     

Increase in circulating bone marrow progenitor cells after myocardial infarction

BACKGROUND: Most circulating blood cells expressing the marker CD34 are bone marrow progenitor cells. These cells differentiate into cardiomyocytes, endothelial and smooth muscle cells after myocardial infarction in vivo. Mobilization of bone marrow progenitor cells into the peripheral blood after myocardial infarction may supply these cells to the heart. Rise in CD34+ cell concentrations following myocardial infarction would support the existence of myocardial-initiated mobilization. METHODS: Serial measurements of circulating CD34+ cells were made in 42 consecutive patients presenting with first ST-elevation myocardial infarction. Measurement of serum concentrations of monocyte chemoattractant protein-1, stromal derived factor-1, hepatocyte growth factor, interleukin-17 and thrombopoietin was also performed. Samples were drawn on day 1 after myocardial infarction, and on days 4, 8 and 12. Levels of CD34+ cells and cytokines were also measured in 15 controls. RESULTS: By day 8, the mean concentration of CD34+ cells rose by 74% above mean control level of 2527 cells/ml, and 41% above day 1 mean (P=0.02). This rise was sustained on day 12 (P=0.05). On day 1, there was a 9.3-fold rise in hepatocyte growth factor above the control level of 589 pg/ml (P=0.002). Hepatocyte growth factor levels declined from the day 1 mean of 6061 to 1485 pg/ml on day 12 (P=0.002). No significant change in stromal derived factor-1, interleukin-17, monocyte chemoattractant protein-1 and thrombopoietin was observed. Elevations in CD34+ cells and hepatocyte growth factor were not related to infarction size as estimated on echocardiography. CONCLUSIONS: Elevation in the concentration of circulating CD34+ cells after myocardial infarction suggests that myocardial initiated bone marrow progenitor cell mobilization exists in humans. The cytokines studied in our protocol are not likely to play a direct role in bone marrow progenitor cell mobilization.     

Isolation and characterization of bone marrow multipotential mesenchymal progenitor cells

OBJECTIVE: There is an increased interest in rheumatology in mesenchymal progenitor/stem cells (MPCs) and their roles in rheumatic diseases, but little is known about the phenotype of these cells in vivo. The aim of this study was to isolate and characterize human bone marrow (BM) MPCs. METHODS: Fluorescence microscopy was used to identify putative MPCs among adherent BM cells. To purify them, a positive selection with antifibroblast microbeads was used, combined with fluorescence-activated cell sorting (FACS) for microbead+,CD45(low) cells. A more detailed phenotype of these cells was determined using 4-color flow cytometry, and standard chondrogenic, osteogenic, and adipogenic assays were used to investigate their differentiation potentials. RESULTS: Putative MPCs microscopically identified as large, fibroblast-like, D7-FIB+ cells were purified using positive selection with D7-FIB-conjugated (antifibroblast) microbeads followed by FACS for specifically bound microbead+,CD45(low) cells. These cells represented 0.01% of mononuclear cells in the BM. They were uniformly positive for CD105, LNGFR, HLA-DR, CD10, CD13, CD90, STRO-1, and bone morphogenetic protein receptor type IA (BMPRIA) and were negative for CD14, CD34, CD117, and CD133. Only cells with this phenotype could proliferate and produce adherent cell monolayers capable of chondrogenic, osteogenic, and adipogenic differentiation. D7-FIB- cells in the BM lacked any MPC activity. Uncultured skin fibroblasts had a phenotype similar to that of BM MPCs, but were negative for LNGFR, STRO-1, HLA-DR, and BMPRIA. CONCLUSION: This study shows the distinct phenotype, morphology, and method of isolation of BM MPCs. The findings may have implications for defining the physiologic roles of MPCs in arthritis, bone diseases, and joint regeneration.     

Effect of a bone marrow microenvironment on the ex-vivo expansion of umbilical cord blood progenitor cells

Progenitor cells (CD34(+)) can be isolated from umbilical cord blood and used to correct or reconstitute various cell lines within the haematopoietic and endothelial cell lineage. The main disadvantage of this procedure relates to the low volume of blood that can be collected after the umbilical cord has been clamped, which limits the number of progenitor cells available for treatment. This limitation, however, can be overcome by expanding CD34(+) cells ex vivo. Our aim was to perform a controlled study to determine if the ex-vivo proliferation of umbilical cord CD34(+) cells is enhanced when they are placed in a system that mimics the bone marrow microenvironment. For this purpose, CD34(+) cells were isolated from umbilical cord blood using a magnetic cell sorting kit and seeded in platforms containing different cocktails of cytokines with and without a three-dimensional (3D) biomatrix. Results from this study suggest that the number of viable cells can double after 1 week in any of the culture platforms and that the 3D biomatrix does not enhance cell proliferation.     

Effect of recombinant interferons alpha and gamma on human bone marrow- derived megakaryocytic progenitor cells

Interferons (IFNs) have been shown to suppress the proliferation of human pluripotent hematopoietic progenitor cells, CFU-GEMM, and committed erythroid (BFU-E, CFU-E) and granulocyte-macrophage (CFU-GM) progenitor cells. However, no information is yet available concerning the effect of IFNs on human megakaryocytic progenitor cells CFU-Mk. Furthermore the mechanisms underlying the inhibitory activity of IFNs are still controversial. Therefore highly purified recombinant IFN preparations, rIFN-alpha and rIFN-gamma, were assessed for their influence on in vitro growth of human bone marrow-derived CFU-Mk as well as CFU-GEMM. In addition, the role of hematopoietic accessory cells, that is, adherent cells and T lymphocytes, in the mediation of the suppressive effect of rIFNs was examined. When added to unseparated bone marrow cells, both rIFN preparations significantly inhibited colony formation with 50% inhibition of CFU-Mk occurring at 22 U/mL for rIFN-alpha and 59 U/mL for rIFN-gamma, while 50% inhibition of CFU-GEMM occurred at 59 U/mL for rIFN-alpha and 101 U/mL for rIFN-gamma. The suppressive effect of rIFN-alpha and rIFN-gamma was selectively abolished by monoclonal antibodies (MoAbs) against rIFN-alpha and rIFN- gamma, thus confirming that the inhibitory activity was due to the rIFN preparations used. The antiproliferative effect of rIFN-alpha and rIFN- gamma on CFU-GEMM growth was not associated with a decrease in the percentage of mixed colonies containing megakaryocytic cells as assessed by use of the MoAb C17.28 against platelet glycoprotein IIIa. Removal of adherent cells and T lymphocytes from the target bone marrow cells had no influence on the suppressive effect of rIFN-alpha, whereas it significantly reduced the inhibitory effect of rIFN-gamma on the growth of megakaryocytic colonies and the other hematopoietic progenitors. The data indicate that (1) human megakaryocytopoiesis is markedly inhibited by rIFN-alpha and rIFN-gamma, and (2) the inhibitory effect of rIFN-alpha is due to a direct action on hematopoietic progenitor cells, whereas the effect of rIFN-gamma is mediated to a significant degree through accessory cell populations.     

Phenotypic characterization of human bone marrow granulocyte-macrophage forming progenitor cells

Cell surface antigens of the human bone marrow CFU-C have been studied. Human marrow cells were incubated with a variety of monoclonal antisera and complement prior to culture in semisolid media. By using indirect immunofluorescent studies, the percentage of bone marrow cells binding the antibodies was determined. The CFU-C phenotype is HLA+, la+, 4F2+, 3A1-, and DUALL-1-. This study provides information that is useful in the study of myeloid cell ontogeny and necessary for the use of some of these reagents in the treatment of bone marrow cells prior to human bone marrow transplantation in various clinical settings.     

Enrichment of pluripotent hemopoietic progenitor cells from human bone marrow

Pluripotent hemopoietic progenitor cells (CFU-GEMM, cells forming mixed hemopoietic colonies in methylcellulose) from human bone marrow were enriched 90-fold by positive selection on the fluorescence-activated cell sorter using monoclonal antibody RFB-1. Bone marrow cells were separated by cell size, using log 90 degrees light scatter, and the cell fraction containing CFU-GEMM was further separated by relative fluorescence intensity for the RFB-1 antigen. Further enrichment, up to 150-fold, was achieved by depleting bone marrow of T cells and mature myeloid cells prior to RFB-1 selection. These procedures yield a cell fraction containing 51% blast cells, 2% promyelocytes, and 47% undifferentiated (lymphocyte-like) mononuclear cells, although only 1% of the cells formed a mixed colony. CFU-GEMM are strongly positive for the RFB-1 antigen, whereas morphologically identifiable erythroblasts, myeloblasts, and promyelocytes are weakly RFB-1+. This suggests that the relative concentration of the RFB-1 antigen on bone marrow cells is inversely related to their maturity. The greatly increased recovery of CFU-GEMM after the separation of bone marrow by log 90 degrees light scatter and the removal of T cells and mature myeloid cells suggested that accessory cells that normally regulate the cloning efficiency of CFU-GEMM were removed.     

骨髓CD34^＋干细胞向内皮细胞转化的诱导方法

目的探讨骨髓CD34^＋细胞向血管内皮细胞转分化的诱导方法。方法采集犬骨髓,经免疫磁珠分离出内皮祖细胞,内皮细胞生长因子（VEGF）诱导分化为内皮细胞并扩增,倒置相差显微镜、免疫细胞化学和摄取DilAc—LDL试验鉴定。将所得细胞种植于人工血管,扫描电镜观察细胞形态,并与MNCs作对比。结果经流式细胞仪测定,分离后的细胞中CD34^＋细胞占78．46％±6．37％;CD34^＋细胞培养2周后细胞基本铺满培养瓶底面,细胞呈“鹅卵石”状排列,CD34^＋和Ⅷ因子免疫细胞化学染色均为阳性。扫描电镜下观察可见内皮细胞平铺于人工血管表面,有伪足伸出并长入血管内表面微孔内。结论通过免疫磁珠方法可分离得到高纯度的骨髓CD34^＋细胞,经体外培养VEGF诱导后可定向分化为内皮细胞。     

Detection of residual lymphoma cells by polymerase chain reaction in peripheral blood is significantly less predictive for relapse than detection in bone marrow

Polymerase chain reaction (PCR) amplification of the t(14;18) has been shown to be a highly sensitive method to detect minimal residual disease in patients with non-Hodgkin's lymphoma (NHL) whose tumors bear this translocation. The ideal tissue source to detect residual lymphoma would be from a previously involved lymph node. However, lymphoid tissue is rarely available once patients achieve complete remission. Although PCR amplification has been used to detect residual lymphoma cells in both bone marrow (BM) and peripheral blood (PB) of patients in complete remission, it is presently unknown whether BM and PB are equivalent tissue sources to detect residual disease. In the present study, we compared the clinical utility of the detection of residual lymphoma in both the BM and the PB of patients with advanced-stage non- Hodgkin's lymphoma before, at the time of, and after high-dose therapy and autologous BM transplantation (ABMT). The detection of residual lymphoma in either the BM or PB was associated with decreased disease- free survival. However, in the present study, 44% of patients who relapsed had no evidence of circulating lymphoma cells in their PB. At the time of BM harvest, PCR-detectable residual lymphoma cells were detected in 211 of 212 patients; although, in a subset of these patients analyzed, lymphoma cells were detected in the peripheral blood of only 49% of patients. When residual lymphoma cells within the autologous BM are infused into the patient these cells are rapidly detectable circulating in the PB in the patient. These cells continue to circulate during the immediate posttransplant period and be detectable in the PB in the majority of patients who are infused with marrow containing residual lymphoma. We conclude that BM is a more informative tissue source than PB in detecting minimal residual disease at the time of and after ABMT, and that contamination of PB early after ABMT appears to be the consequence of reinfusion of lymphoma cells within autologous marrow.